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  • 1. Ahuja, B. L.
    et al.
    Arora, G
    Ahmed, G
    Rathor, A
    Sharma, V
    Kádas, Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    A study of electron momentum density and charge transfer in W-Cu system2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 467, no 1-2, p. 595-599Article in journal (Refereed)
    Abstract [en]

    We present the first ever Compton scattering study on WxCu1-x(x=0.60, 0.72) alloys. The Compton profile measurements have been made using 20Ci (CS)-C-137 gamma-ray source. The experimental data are compared with the superposition of APW-based Compton profiles of constituent metals. A schematic study on charge transfer has been reported using the experimental valence band Compton profiles of both the alloys, W and Cu. Our first ever data support the charge transfer from W to Cu on alloying, which is also confirmed by our band structure calculations employing exact muffin-tin orbitals method (EMTO). (C) 2007 Elsevier B.V. All rights reserved.

  • 2.
    Allal, Adel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Amar Telidji, Lab Phys Mat, BP 37G, Laghouat 03000, Algeria..
    Bouchenafa, Mohamed
    Univ Amar Telidji, Fac Sci, Dept Sci Matiere, BP 37G, Laghouat 03000, Algeria.;Univ Blida 1, Theoret Phys & Radiat Matter Interact Lab LPTHIRM, Phys Dept, Blida, Algeria..
    Halit, Mohamed
    Univ Amar Telidji, Lab Phys Mat, BP 37G, Laghouat 03000, Algeria..
    Saib, Salima
    Univ Msila, Lab Mat Phys & Applicat, Msila 28000, Algeria..
    Liu, Zeliang
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Yanshan Univ, Coll Civil Engn & Mech, Qinhuangdao, Hebei, Peoples R China..
    Luo, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Structural stability, mechanical, electronic and optical behaviour of RbXS2 (X = Y and La) under high pressure: A first-principle study2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 848, article id 156401Article in journal (Refereed)
    Abstract [en]

    The high-pressure behaviour of the ternary sulphides, RbXS2 (X = Y and La), has been investigated by using first-principle calculations based on density functional theory. Upon applying hydrostatic pressure, the unit-cell parameters (a, c) decrease with different rates, indicating an anisotropic axial compression. The most of RbYS2 and RbLaS2 crystals compressibility comes from Rb+1-S-2 bonds. Elastic constants and their dependence on pressure and related mechanical properties have been reported and analysed. From Pugh's criterion, RbYS2 and RbLaS2 turn from brittle to ductile material for applied pressures beyond 3.1 GPa and 2.9 GPa, respectively. Stability criteria show that RbYS2 and RbLaS2 are not mechanically stable in ci-NaFeO2 crystal structure above 20.63 GPa and 16.24 GPa, respectively. Both RbYS2 and RbLaS2 have indirect band gap, which decreases with increasing pressure. However, no indirectdirect band gap transition is observed for both materials. Finally, the calculated optical spectrum of both compounds exhibits an anisotropy and a broadening at high pressures.

  • 3. Azdouz, M.
    et al.
    Manoun, B.
    Essehli, R.
    Azrour, M.
    Bih, L.
    Benmokhtar, S.
    Ait Hou, A.
    Lazor, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Crystal chemistry, Rietveld refinements and Raman spectroscopy studies of the new solid solution series: Ba3−xSrx(VO4)2 (0≤x≤3)2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 498, no 1, p. 42-51Article in journal (Refereed)
    Abstract [en]

    The new solid solution series Ba3-xSrx(VO4)(2) (0 <= x <= 3) has been synthesized and studied by a combination of X-ray powder diffraction and Raman vibrational spectroscopy. This continuous solid solution crystallise in the hexagonal system with R (3) over barm space group. The structure has been determined at room temperature from X-ray diffraction by the Rietveld method analysis. It is formed by a 3D network of (Ba/Sr)((1))(VO4)(2)(4-) layers linked into a crystal network by (Ba/Sr)(2+)((2)) cations. The vibrational spectra of this crystalline orthovanadate solid solution series are interpreted by means of factor group analysis in terms of space group R (3) over barm (D-3d(5)). Assignments of the V-O vibrational stretching and bending modes, as well as some of the external modes, have been made. While all the modes show a monotonous shift as a function of the composition x, a break in the curves of intensities, full width at half maximum and band areas as a function of x is observed and attributed to the statistical distribution of Ba and Sr ions in the same crystallographic sites.

  • 4. Azofeifa, D. E.
    et al.
    Clark, N.
    Vargas, W. E.
    Solis, H.
    Pálsson, Gunnar K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hydrogen induced changes in the optical properties of Pd capped V thin films2013In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 580, no Suppl. 1, p. S114-S118Article in journal (Refereed)
    Abstract [en]

    Optical properties of 50 nm thick single crystal vanadium films deposited on double side polished MgO substrates have been obtained from spectrophotometric measurements. The films were coated with a polycrystalline Pd layer (5 nm thick) to protect them from oxidation and to favor absorption of atomic hydrogen. Electrical resistance was recorded while hydrogen pressure was increased slowly up to 750 mbar keeping temperature constant. Simultaneously, under normal incidence of non-polarized radiation [350-950 nm], transmittance spectra of this Pd/V/MgO system were measured. These were numerically inverted to obtain the spectral behavior of the Pd, V. PdHy, and VHx dielectric functions at 22 and 140 degrees C, and at 750 mbar. Hydrogen concentration in V film was first determined from a resisto-optical method. Finally, we demonstrate the possibility to determine the concentration in the Pd and the V layers independently, solely using the changes in the optical transmission. 

  • 5. Baranovskiy, A. E.
    et al.
    Grechnev, G. E.
    Fil, V. D.
    Ignatova, T. V.
    Logosha, A. V.
    Panfilov, A. S.
    Svechkarev, I. V.
    Shitsevalova, N. Y.
    Filippov, V. B.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Electronic structure, bulk and magnetic properties of MB6 and MB12 borides2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 442, no 1-2, p. 228-230Article in journal (Refereed)
    Abstract [en]

    The bulk and magnetic properties of MB6 and MB12 were investigated on the basis of first principles electronic structure calculations. The elastic constants were measured for ZrB12, HoB12, ErB12, TmB12, LuB12, YB6 and LaB6 compounds at low temperatures. The calculated equations of states and balanced crystal orbital overlap populations have allowed to analyse bonding and magnetic properties of MB6 and MB12

    .

  • 6.
    Boeije, M. F. J.
    et al.
    Delft Univ Technol, Fundamental Aspects Mat & Energy, Fac Sci Appl, Mekelweg 15, NL-2629 JB Delft, Netherlands..
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    van Dijk, N. H.
    Delft Univ Technol, Fundamental Aspects Mat & Energy, Fac Sci Appl, Mekelweg 15, NL-2629 JB Delft, Netherlands..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bruck, E.
    Delft Univ Technol, Fundamental Aspects Mat & Energy, Fac Sci Appl, Mekelweg 15, NL-2629 JB Delft, Netherlands..
    On the phase stability of CaCu5-type compounds2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 722, p. 549-554Article in journal (Refereed)
    Abstract [en]

    We present a hybrid method to inspect the phase stability of compounds having a CaCu5-type crystal structure. This is done using 2D stability plots using the Miedema parameters that are based on the work function and electron density of the constituent elements. Stable compounds are separated from unstable binary compounds, with a probability of 94%. For stable compounds, a linear relation is found, showing a constant ratio of charge transfer and electron density mismatch. DFT calculations show the same trend. Elements from the s, d, f-block are all reliably represented, elements from the p-block are still challenging.

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  • 7.
    Cedervall, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Mikael Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Delczeg-Czirjak, Erna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bergqvist, Lars
    Hansen, Thomas C.
    Beran, Premysl
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetic structure of the magnetocaloric compound AlFe2B22016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 654, p. 784-791Article in journal (Refereed)
    Abstract [en]

    The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be - 1.3 J/K kg at the magnetic transition temperature.

  • 8.
    Czub, J.
    et al.
    AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, Mickiewicza 30, PL-30059 Krakow, Poland.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Przewoznik, J.
    AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, Mickiewicza 30, PL-30059 Krakow, Poland.
    Zarzecka, A.
    AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, Mickiewicza 30, PL-30059 Krakow, Poland.
    Hoser, A.
    Helmholtz Zentrum Berlin, Hahn Meitner Pl 1, D-14109 Berlin, Germany.
    Gondek, L.
    AGH Univ Sci & Technol, Fac Phys & Appl Comp Sci, Mickiewicza 30, PL-30059 Krakow, Poland.
    On the properties of the novel CeMgNi2T2 (T = Co, Cu) alloys and their hydrides2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 814, article id 152244Article in journal (Refereed)
    Abstract [en]

    In this contribution, we report the results of the studies on the novel CeMgNi2Co2 and CeMgNi2Cu2 alloys and their hydrides/deuterides. Both the parent alloys and the CeMgNi2Co2H6.1 hydride crystallize in the MgCu4Sn-type structure, while the CeMgNi2Cu2H6.0 hydride becomes almost completely amorphous. In the MgCu4Sn structure the 3d metals are distributed over the 16e site forming the pyrochlore lattice. That makes this system particularly interesting as concerns the magnetic properties. Our studies reveal that magnetic susceptibilities of the alloys are weakly temperature-dependent and therefore, the Pauli-like paramagnetism can be suggested. Additionally, the results of the low temperature neutron diffraction experiments revealed the lack of the long-range magnetic ordering.

  • 9.
    Dastanpour, Esmat
    et al.
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Huang, Shuo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. China Univ Geosci, Fac Mat Sci & Chem, Wuhan 430074, Peoples R China..
    Dong, Zhihua
    Chongqing Univ, Coll Mat Sci & Engn, Natl Engn Res Ctr Magnesium Alloys, Chongqing 400044, Peoples R China.;Chongqing Inst Adv Light Met, Chongqing 400030, Peoples R China..
    Schönecker, Stephan
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Ström, Valter
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, H-1525 Budapest, Hungary..
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, H-1525 Budapest, Hungary..
    Investigation of the metastable spinodally decomposed magnetic CrFe-rich phase in Al doped CrFeCoNi alloy2023In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 939, article id 168794Article in journal (Refereed)
    Abstract [en]

    We have conducted an in-depth study of the magnetic phase due to a spinodal decomposition of the BCC phase of a CrFe-rich composition. This magnetic phase is present after casting (arc melting) or water quenching after annealing at 1250 degrees C for 24 h but is entirely absent after annealing in the interval 900-1100 degrees C for 24 h. Its formation is favored in the temperature interval ca 450-550 degrees C and loses magnetization above 640 degrees C. This ferromagnetic-paramagnetic transition is due to a structural transformation from ferromagnetic BCC into paramagnetic sigma and FCC phases. The conclusion from measurements at different heating rates is that both the transformation leading to the increase of the magnetization due to the spinodal decomposition of the parent phase and the vanishing magnetization at 640 degrees C are diffusion controlled.

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  • 10.
    Dastanpour, Esmat
    et al.
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Huang, Shuo
    China Univ Geosci, Fac Mat Sci & Chem, Wuhan 430074, Peoples R China..
    Ström, Valter
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Varga, Lajos Karoly
    Wigner Res Ctr Phys, Inst Solid State Phys & Opt, H-1525 Budapest, Hungary..
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Schönecker, Stephan
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    An assessment of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8) high-entropy alloys for magnetocaloric refrigeration application2024In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 984, article id 173977Article in journal (Refereed)
    Abstract [en]

    This study investigates the magnetocaloric potential of the Al50Cr21-xMn17+xCo12 (x=0, 4, 8 at%) high-entropy alloy (HEA) series using integrated experimental and theoretical approaches. Structural analysis by X-ray diffraction and scanning electron microscopy indicate a dual phase containing B2 and body-centered cubic (BCC) structures. Magnetic characterization shows an approximately linear decrease in saturation magnetization and Curie temperature with increasing Cr content. Curie temperatures calculated by Monte Carlo simulations suggest that the measured magnetic properties originate from the B2 phase rather than the BCC phase. The enhanced magnetocaloric effect with decreasing Cr content highlights the attractiveness of HEAs in magnetocaloric applications.

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  • 11. Denys, R. V.
    et al.
    Riabov, B.
    Yartys, V. A.
    Delaplane, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, The Studsvik Neutron Research Laboratory.
    Sato, M.
    Hydrogen storage properties and structure of La1-xMgx(Ni1-yMny)(3) intermetallics and their hydrides2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 446, p. 166-172Article in journal (Refereed)
    Abstract [en]

    'Hybrid' RNi3 (R =rare earth metal) crystal structures are built of the slabs of simpler types, CaCu5 and MgZn2. Different affinities of these slabs to hydrogen result in unusual "anisotropic" expansion of the RNi3 and R2Ni7 (R = La, Cc) structures upon hydrogenation. This work focuses on studies of the hydrogenation behaviour of LaNi3 and on the properties of the hydrides of the modified by Mg and Mn La-Ni alloys. The crystal structure of LaNi3D2.8 and the crystal structure and hydrogen storage behaviours of the La1.5Mg0.5Ni7 and La(Ni-1-,Mn,)3 (x=0; 0.067-, 0.133; 0.2: 0.267; 0.3; 0.333; 0.4) alloys were in focus. The deuteration of LaNi3 with PuNi3 type of structure leads to the formation of LaNi3D2.8 and is accompanied by a deformation of the metal matrix causing a change of the initial rhombohedral symmetry (space group R3m) to a nionoclinic one (space group C2/m; a = 8.6408(7) angstrom, b=4.928](4) angstrom, c= 32.774(3) A; = 90.850(8)degrees; V= 1395.5(2) angstrom(3)). Similar to the earlier studied CeNi3D2.8, preferential occupation by deuterium atoms of the AB, layers takes place, leading to the "anisotropic" expansion of the unit cell along [0 0 1] (Delta c/c = 30.6%). 14 occupied D crystallographic sites have 4 chemically different types of metal-atom surroundings, including Ni-4 (2), La2Ni2 (2), La3Ni (6), and La3Ni3 (4). Modification of the La-Ni alloys by magnesium and manganese leads to the formation of intermetallic compounds crystallising with the PuNi3, CeNi3, and Ce2Ni7-type structures. An ordered substitution of La by Mg in the MgZn2-type slabs was observed, causing a complete alteration of the hydrogenation behaviour of the original LaNi3 alloy. La1.5Mg0.5Ni7D9 isotropically expands upon its formation and leads to a substantial increase of the stability against hydrogenation-induced aniorphisation. On the other hand, replacement of Ni by Mn leads to the change in crystal-structure type from PuNi3 to CeNi3 in the LaNi3-xMn. alloys (x>0.1). An ordered substitution of Ni by Mn proceeds inside the RNi5 slabs only. This decreases the stability of the initial alloy against amorphisation on hydrogenation.

  • 12.
    Eggert, Bruno G. F.
    et al.
    Inst Energy Technol IFE, Dept Hydrogen Technol, POB 40, NO-2027 Kjeller, Norway..
    Delczeg-Czirjak, Erna Krisztina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Maccari, Fernando
    Tech Univ Darmstadt, Mat Sci, Funct Mat, D-64287 Darmstadt, Germany..
    Kumar, Susmit
    Univ Oslo, Dept Chem, Sem Saelands Vei 26, N-0371 Oslo, Norway..
    Gutfleisch, Oliver
    Tech Univ Darmstadt, Mat Sci, Funct Mat, D-64287 Darmstadt, Germany..
    Fjellvag, Helmer
    Univ Oslo, Dept Chem, Sem Saelands Vei 26, N-0371 Oslo, Norway..
    Hauback, Bjorn C.
    Inst Energy Technol IFE, Dept Hydrogen Technol, POB 40, NO-2027 Kjeller, Norway..
    Frommen, Christoph
    Inst Energy Technol IFE, Dept Hydrogen Technol, POB 40, NO-2027 Kjeller, Norway..
    Exploring V-Fe-Co-Ni-Al and V-Fe-Co-Ni-Cu high entropy alloys for magnetocaloric applications2022In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 921, article id 166040Article in journal (Refereed)
    Abstract [en]

    A series of V1-x-Fe-Co-Ni-Al1+ x and V1-x-Fe-Co-Ni-Cu1+ x high entropy alloys with varying compositions (0 <= x <= 0.75) has been investigated for magnetocaloric applications. Compositions were selected according to established properties, such as configurational entropy, atomic size difference, and enthalpy of mixing. To study the influence of composition on magnetic ordering temperatures, the V and (Al/Cu) contents were changed while the content of Fe, Co and Ni was retained at 20 at. % each. The crystal structure and microstructure of the as-cast alloys were compared to literature phase guidelines and thermodynamic calculations based on the CALPHAD approach. The V-Fe-Co-Ni-Al compounds are monophasic and crystallize in a disordered body centered cubic structure or its ordered B2 variant, while the V-Fe-Co-Ni-Cu compounds are all multiphasic. Magnetic transitions in the V-Fe-Co-Ni-Al system span over 400 K, with Curie temperature ranging from 155 K in equiatomic VFeCoNiAl, to 456 K in non-equiatomic V0.25FeCoNiAl1.75. The V-Fe-Co-Ni-Cu alloys display magnetic transitions that span about 150 K, with Curie temperature ranging from 230 K for equiatomic VFeCoNiCu to 736 K for non-equiatomic V0.25FeCoNiCu1.75. The magnetic properties of the V-Fe-Co-Ni-Cu compounds were evaluated by means of density functional theory. Individual element-specific moments, magnetic exchange integrals between atomic pairs, and Curie temperatures were calculated. V0.85FeCoNiCu1.15 is selected due to its Curie temperature of 329 K, and its calculated isothermal entropy change of 0.75 J/kg.K for a field change of 5 T is comparable to other 3d metal-based high entropy alloys that form disordered solid solutions. (c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.0

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  • 13.
    Ek, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fjellvåg, Øystein S.
    Institute for Energy Technology, Department of Neutron Materials Characterization, P.O Box 40, NO-2027, Kjeller, Norway.
    Vajeeston, Ponniah
    Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, P.O Box 1033, NO-0315, Oslo, Norway.
    Armstrong, Jeff
    ISIS Pulsed Neutron and Muon source, Rutherford Appleton Laboratory, OX11 0QX, Didcot, United Kingdom.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Häussermann, Ulrich
    Department of Materials and Environmental Chemistry, Stockholm University, SE-10691, Stockholm, Sweden.
    Vibrational properties of High Entropy Alloy based metal hydrides probed by inelastic neutron scattering2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 877, article id 160320Article in journal (Refereed)
    Abstract [en]

    The vibrational properties of several High Entropy Alloy (HEA) based metal hydrides are investigated by inelastic neutron scattering (INS). HEAs have recently emerged as a new type of materials with a wide range of intriguing properties and potential applications such as hydrogen storage. The special properties of HEAs are believed to originate from the disordered lattice and internal strain that is introduced from the differences in atomic radii. This makes HEA hydrides provide an intriguing situation for the local H coordination, of several different transition metals. INS spectra were collected on a series of HEA-based metal hydrides starting with TiVNbHx and subsequently adding Zr and Hf to increase the atomic size mismatch. A general feature of the spectra are the optical peaks centered around an energy loss of 150 meV that can be attributed to hydrogen vibrations in a tetrahedral environment. Upon the addition of Zr and Hf, a shoulder appears on the optical peak at lower energy transfers that after comparison with in silico calculated INS spectra is indicative of hydrogen also occupying octahedral sites in the structure.

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  • 14. Eriksson, Anna Karin
    et al.
    Liebig, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ólafsson, Sveinn
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Resistivity changes in Cr/V(0 0 1) superlattices during hydrogen absorption2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 446, p. 526-529Article in journal (Refereed)
    Abstract [en]

    The hydrogen induced resistivity changes in Cr/VHx(0 0 1) superlattices where investigated in the concentration range 0<x<0.7. Initially, the resistivity increases with H content, reaching a maximum at H/V≈0.5 atomic ratio. At concentration above 0.5, the resistivity decreases with increasing H concentration. These results are in stark contrast to the H induced resistivity changes in Fe/V(0 0 1) superlattices, in which the resistivity increases monotonically up to H/V≈1. The results unambiguously prove the importance of the interface scattering, which calls for better theoretical description of the H induces changes in the electronic structure in this type of materials.

  • 15.
    Eriksson, Therese
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Mellergård, Anders
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Larsson, Anna-Kristin
    Felton, Solveig
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Höwing, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Magnetic short-range order in the new ternary phase Mn8Pd15Si72005In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 403, no 1-2, p. 19-28Article in journal (Refereed)
    Abstract [en]

    A new compound, Mn8Pd15Si7, is reported to crystallize in a face centered cubic unit cell of dimension a = 12.0141(2) Å, space group, and can thus be classified as a G-phase. The crystal structure was studied by single crystal X-ray diffraction, X-ray and neutron powder diffraction and electron diffraction. A filled Mg6Cu16Si7 type structure was found, corresponding to the Sc11Ir4 type structure. The magnetic properties were investigated by magnetization measurements and Reverse Monte Carlo modeling of low temperature magnetic short-range order (SRO). Dominating near neighbor antiferromagnetic correlations were found between the Mn atoms and geometric frustration in combination with random magnetic interactions via metal sites with partial Mn occupancy were suggested to hinder formation of long-range magnetic order.

  • 16.
    Ershadi, Mahshid
    et al.
    Amirkabir Univ Technol, Dept Chem, Tehran, Iran;Amirkabir Univ Technol, Renewable Energy Res Ctr, Tehran, Iran.
    Javanbakht, Mehran
    Amirkabir Univ Technol, Dept Chem, Tehran, Iran;Amirkabir Univ Technol, Renewable Energy Res Ctr, Tehran, Iran.
    Mozaffari, Sayed Ahmad
    Amirkabir Univ Technol, Renewable Energy Res Ctr, Tehran, Iran;IROST, Dept Chem Technol, Tehran, Iran.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lee, Ming-Tao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Zahiri, Beniamin
    Univ British Columbia, Clean Energy Res Ctr, 6250 Appl Sci Lane, Vancouver, BC V6T 1Z4, Canada.
    Facile stitching of graphene oxide nanosheets with ethylenediamine as three dimensional anode material for lithium-ion battery2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 818, article id 152912Article in journal (Refereed)
    Abstract [en]

    In this study, we employed an efficient and straightforward synthesis method for the functionalization and stitching of graphene oxide (GO) sheets with ethylenediamine (EDA). 3-D-structured GO-EDA was prepared by low reduction of the oxygen-containing functional groups of GO. The EDA was used as a nitrogen source to create the nitrogen-doped graphene (N-graphene), as well as a factor to control the self-assembly of graphene nanosheets into 3-D structures. The morphology, composition, and covalently grafted functional groups of GO-EDA were investigated by FT-IR and Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and various electrochemical techniques. GO-EDA exhibits a layered structure resembling graphite, with an enhanced d-spacing of 0.373 nm compared with graphite (0.348 nm). The results showed that the porous channels of the synthesized GO-EDA facilitate the efficient transportation of lithium ions through the electrolyte-filled channels. The first discharge and charge showed specific capacities of 830.34 mAh g(-1) and 664 mAh g(-1), respectively at the current density of 100 mA g(-1), corresponding to an initial coulombic efficiency of ca. similar to 80%; superior to the GO reference (27.8%). Moreover, GO-EDA displayed improve cycling stability (maintaining a reversible capacity of similar to 300 mAh g(-1) at 200 mA g(-1) after 100 cycles). The improved electrochemical operation was ascribed to enhanced ion (Li+) transport within the graphitic layers by the increased d-spacing due to the inserted functional groups. 

  • 17.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Casado, Francisco Javier Martinez
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Matej, Zdenek
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Bednarcik, Jozef
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany..
    Ångstrom, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Insights into formation and stability of tau-MnAlZ(x) (Z = C and B)2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 692, p. 198-203Article in journal (Refereed)
    Abstract [en]

    The tau-phase MnAl alloys are promising candidate for rare earth free permanent magnets. In this study, In order to better understand the MnAl epsilon ->tau phase transition mechanism in a continuous cooling process and metastable MnAl tau-phase high temperature stability, Mn0.54Al0.46, Mn0.55Al0.45C0.02 and Mn0.55Al0.45B0.02 alloys were systematically studied by in situ synchrotron X-ray powder diffraction (SR-XRD). The relationship between tau-phase formation tendency and different cooling rates of Mn0.55Al0.45C0.02 was investigated. Besides, the high temperature stabilities of undoped tau-MnAl and carbon/boron doped tau-MnAl were studied. Differential thermal analysis (DTA) was also employed to study the phase transformation as well. The research results show that a high cooling rate of 600 degrees C/min leads to a 50/50 wt% mixture of epsilon- and tau-phase; almost pure tau-phase was obtained when cooled at a moderate cooling rate of 10 degrees C/min; while for a slow cooling rate of 2 degrees C/min, the tau-phase partially decomposed into beta and gamma(2) phases. No intermediate epsilon'-phase was observed during the epsilon ->tau phase transition during the experiments. For the boron and carbon doped tau-MnAl, the 800 degrees C high temperature stability experiments reveal that C stabilizes the tau-MnAl while doped B destabilises the tetragonal structure and it decomposes into beta- and gamma(2)-phases.

  • 18.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Li, Jiheng
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing, Peoples R China.
    Shafeie, Samrand
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ekström, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gómez, Cesar Pay
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Bednarcik, Jozef
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Insights into phase transitions and magnetism of MnBi crystals synthesized from self-flux2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 781, p. 308-314Article in journal (Refereed)
    Abstract [en]

    To effectively synthesize high purity ferromagnetic low temperature phase (LTP) MnBi with optimal microstructure is still a challenge that needs to be overcome for the system to reach its full potential. Here, the phase transitions and magnetic properties of MnBi crystals are reported. The phase transition between the low and high temperature structure of MnBi was systematically investigated at different heating/cooling rates using in situ synchrotron radiation X-ray diffraction. The material crystallizes in a layered hexagonal structure giving a platelike microstructure. The magnetic characterization of the crystals reveal that the saturation magnetization varies from 645 kA/m at 50 K to 546 kA/m at 300 K. Magnetization measurements also show that the sample upon heating becomes non-magnetic and transforms to the high temperature phase (HTP) at similar to 640 K, and that it regains ferromagnetic properties and transforms back to the LTP at similar to 610 K upon subsequent cooling.

  • 19.
    Fernandes, P. A.
    et al.
    IPP, CIETI, Dept Fis, Inst Super Engn Porto, Rua Dr Antonio Bernardino de Almeida 431, P-4200072 Porto, Portugal;INL Int Iberian Nanotechnol Lab, Av Mestre Jose Veiga, P-4715330 Braga, Portugal;Univ Aveiro, I3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Shongalova, A.
    Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal;Satbayev Univ, Satpayev St 22a, Almaty City 050013, Kazakhstan.
    da Cunha, A. F.
    Univ Aveiro, I3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Teixeira, J. P.
    Univ Aveiro, I3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Leitao, J. P.
    Univ Aveiro, I3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Cunha, J. M. V.
    INL Int Iberian Nanotechnol Lab, Av Mestre Jose Veiga, P-4715330 Braga, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Bose, Sourav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. INL Int Iberian Nanotechnol Lab, Av Mestre Jose Veiga, P-4715330 Braga, Portugal.
    Salome, P. M. P.
    INL Int Iberian Nanotechnol Lab, Av Mestre Jose Veiga, P-4715330 Braga, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Correia, M. R.
    Univ Aveiro, I3N, Campus Univ Santiago, P-3810193 Aveiro, Portugal;Univ Aveiro, Dept Fis, Campus Univ Santiago, P-3810193 Aveiro, Portugal.
    Phase selective growth of Cu12Sb4S13 and Cu3SbS4 thin films by chalcogenization of simultaneous sputtered metal precursors2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 797, p. 1359-1366Article in journal (Refereed)
    Abstract [en]

    In this work, we present a procedure to grow Cu12Sb4S13 and Cu3SbS4 thin films consisting of the deposition of simultaneously sputtered metal precursors followed by a annealing treatment in a sulphur atmosphere. The selection of the ternary phase is performed by adjusting the sulphur evaporation temperature in the chalcogenization process. It is shown that for a sulphur evaporation temperature of 140 °C the predominant phase is Cu12Sb4S13 while for 180 °C the predominant phase is Cu3SbS4. In order to ensure precursor composition homogeneity, the Cu-Sb metallic precursors are deposited simultaneously by RF magnetron sputtering using adjustable segmented targets. The morphological characterization of the films was made by scanning electron microscopy and the composition was analysed by energy dispersive spectroscopy. The structural analysis and phase identification were performed by X-ray diffraction and Raman scattering. The optical properties were studied on films deposited directly on bare glass and the optical bandgap energies of 1.47 eV and 0.89 eV for Cu12Sb4S13 and Cu3SbS4, respectively, were determined.

  • 20. Fraerman, A. A.
    et al.
    Gribkov, B. A.
    Gusev, S. A.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
    Artificial helix nanomagnets2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 103, p. 073916-Article in journal (Refereed)
  • 21.
    Fu, Jie
    et al.
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China..
    Li, Xiaoqing
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Zhao, Jijun
    Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Ion & Electron Beams, Dalian 116024, Peoples R China..
    Improved Finnis-Sinclair potential for vanadium-rich V-Ti-Cr ternary alloys2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 705, p. 369-375Article in journal (Refereed)
    Abstract [en]

    We have developed an improved Finnis-Sinclair (IFS) potential for vanadium-rich V-Ti-Cr random alloys with body-centred cubic structure. An extra exponential term is added to the original FS potential to enhance the repulsive interaction. The IFS potential is fitted to experimental crystal structure, cohesive energy and elastic constants of pure metals (V, Ti and Cr) and theoretical data of binary alloys (V15Ti, V15Cr and Ti8Cr8). The good agreement of the predicted formation energies of mono-vacancy and selfinterstitial of octahedral interstitial site, tetrahedral interstitial site, < 111>-dumbbell, < 110>-dumbbell, and < 100>-dumbbell with available experimental and theoretical data confirms the validity of our IFS potential in pure V. Furthermore, the agreement of elastic properties and defect properties of typical alloy (V-4-Ti-4-Cr) with experimental or DFT data also support the applicability of the IFS potential in Vrich ternary V-Ti-Cr alloys. Finally, this work also provides a reference to develop empirical potentials for other ternary alloys.

  • 22.
    Fuger, C.
    et al.
    TU Wien, Christian Doppler Lab Surface Engn High Performan, Vienna, Austria..
    Schwartz, B.
    TU Wien, Christian Doppler Lab Surface Engn High Performan, Vienna, Austria..
    Wojcik, T.
    TU Wien, Christian Doppler Lab Surface Engn High Performan, Vienna, Austria.;TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria..
    Moraes, V
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria..
    Weiss, M.
    TU Wien, Inst Chem Technol & Analyt, Vienna, Austria..
    Limbeck, A.
    TU Wien, Inst Chem Technol & Analyt, Vienna, Austria..
    Macauley, C. A.
    Friedrich Alexander Univ Erlangen Nurnberg, Dept Mat Sci, Erlangen, Germany.;Interdisciplinary Ctr Nanostruct Films IZNF, D-91058 Erlangen, Germany..
    Hunold, O.
    Oerlikon Surface Solut AG, Oerlikon Balzers, FL-9496 Balzers, Liechtenstein..
    Polcik, P.
    Plansee Composite Mat GmbH, D-86983 Lechbruck, Germany..
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Felfer, P.
    Friedrich Alexander Univ Erlangen Nurnberg, Dept Mat Sci, Erlangen, Germany..
    Mayrhofer, P. H.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria..
    Riedl, H.
    TU Wien, Christian Doppler Lab Surface Engn High Performan, Vienna, Austria.;TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria..
    Influence of Ta on the oxidation resistance of WB2-z coatings2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 864, article id 158121Article in journal (Refereed)
    Abstract [en]

    Ternary W1-x TaxB2-z is a promising protective coating material possessing enhanced ductile character and phase stability compared to closely related binaries. Here, the oxidation resistance of W1-xTaxB2-z thin films was experimentally investigated at temperatures up to 700 degrees C. Ta alloying in sputter deposited WB2-z coatings led to decelerated oxide scale growth and a changed growth mode from paralinear to a more linear (but retarded) behavior with increasing Ta content. The corresponding rate constants decrease from k(p)* = 6.3.10(-4) mu m(2)/s for WB2-z to k(p)* = 1.1.10(-4) mu m(2)/s for W0.66Ta0.34B2-z as well as k(1) = 2.6.10(-5) mu m/s for TaB2-z, underlined by decreasing scale thicknesses ranging from 1170 nm (WB2-z), over 610 nm (W0.66Ta0.34B2-z) to 320 nm (TaB2-z) after 10 min at 700 degrees C. Dense and adherent scales exhibit an increased tantalum content (columnar oxides), which suppresses the volatile character of tungsten-rich as well as boron oxides, hence being a key-factor for enhanced oxidation resistance. Thus, adding Ta (in the range of x = 0.2-0.3) to a-structured WB2-z does not only positively influence the ductile character and thermal stability but also drastically increases the oxidation resistance.

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  • 23.
    Ghorai, Sagar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Shtender, Vitalii
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ström, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skini, Ridha
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Effect of small cation occupancy and anomalous Griffiths phase disorder in nonstoichiometric magnetic perovskites2022In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 895, article id 162714Article in journal (Refereed)
    Abstract [en]

    The structural, magnetic, magnetocaloric and Griffiths phase (GP) disorder of non-stoichiometric perovskite manganites La0.8-xSr0.2-yMn1+x+yO3 are reported here. Determination of valence states and structural phases evidenced that the smaller cations Mn2+ and Mn3+ will not occupy the A-site of a perovskite under atmospheric synthesis conditions. The same analysis also supports that the vacancy in the A-site of a perovskite induces a similar vacancy in the B-site. The La3+ and Sr2+ cation substitutions in the A-site with vacancy influences the magnetic phase transition temperature (TC) inversely, which is explained in terms of the electronic bandwidth change. An anomalous non-linear change of the GP has been observed in the Sr substituted compounds. The agglomeration of Mn3+-Mn4+ pairs (denoted as dimerons), into small ferromagnetic clusters, has been identified as the reason for the occurrence of the GP. A threshold limit of the dimeron formation explains the observed non-linear behaviour of the GP formation. The Sr-substituted compounds show a relatively large value of isothermal entropy change (maximum 3.27 J/kgK at mu H-0 = 2T) owing to its sharp magnetic transition, while the broad change of magnetization in the La-substituted compound enhances the relative cooling power (maximum 98 J/kg at mu H-0 = 2T).

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  • 24. Ghosh, Tanmoy
    et al.
    Jena, Ambika Prasad
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sonomura, Hirosuke
    Fukuda, Takashi
    Kakeshita, Tomoyuki
    Mukhopadhyay, P. K.
    Mookerjee, Abhijit
    Effect of short range ordering on the magnetism in disordered Fe:Al alloy2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 613, p. 306-311Article in journal (Refereed)
    Abstract [en]

    Magnetic behavior of equiatomic FeAl alloy is still not satisfactorily understood. In this work, we studied the magnetic properties of disordered FeAl alloy both experimentally and using first-principles theories and revisited the alloy system in perspective of the inhomogeneity present in the system. After obtaining magnetic exchange interactions from first-principles theories, we carried out Monte-Carlo simulations on special quasi-random structures (SQS) and compared the results with experimental measurements. We tried to understand the plethora of often differing results and explain them in terms of possible inhomogeneities in the system.

  • 25.
    Gyergyek, Saso
    et al.
    Jozef Stefan Inst, Dept Synth Mat, Jamova 39, SI-1000 Ljubljana, Slovenia..
    Chernyshova, Elena
    Natl Inst Chem, Dept Mat Chem, Hajdrihova 19, SI-1000 Ljubljana, Slovenia..
    Böör, Katalin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Jozef Stefan Inst, Dept Synth Mat, Jamova 39, SI-1000 Ljubljana, Slovenia..
    Necemer, Marijan
    Jozef Stefan Inst, Dept Low & Medium Energy Phys, Jamova 39, SI-1000 Ljubljana, Slovenia..
    Makovec, Darko
    Jozef Stefan Inst, Dept Synth Mat, Jamova 39, SI-1000 Ljubljana, Slovenia..
    Magnetic carbon nanocomposites via the graphitization of glucose and their induction heating2023In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 953, article id 170139Article in journal (Refereed)
    Abstract [en]

    Carbon nanocomposites containing iron-based nanoparticles are attractive materials for the catalyst sup-ports used for magnetic (induction) heating catalysis. The metallic, soft-magnetic iron nanoparticles pro-vide local heating of the support in an alternating magnetic field and ensure rapid magnetic separation of the nanocomposite particles from reaction suspensions. In this work, magnetic carbon nanocomposites were prepared by annealing the precursor particles consisting of iron-oxide nanoparticles dispersed in a carbohydrate matrix. The annealing was conducted at 600 degrees C and 750 degrees C in an Ar atmosphere. At both temperatures the carbothermal reduction of iron oxide to Fe/Fe3C was observed; however, at the lower temperature the rate of reduction and the growth of the nanoparticles were considerably slower. The Fe3C was formed in negligible amounts only after a prolonged period of annealing at 600 degrees C. A detailed structural analysis showed that the Fe/Fe3C nanoparticles catalyze the graphitization of the carbonaceous precursor material already at 600 degrees C, resulting in the formation of a graphitic shell that surrounds them. This shell is tight enough to prevent the areal oxidation of the encapsulated Fe nanoparticles; their magnetic properties remained unchanged even after 1 year of storage under ambient conditions. At the higher annealing temperature, the growth of the Fe/Fe3C nanoparticles caused bursting of the graphitic shell and thus par-tially exposed their surfaces to the atmosphere. All the nanocomposites exhibited ferromagnetic behavior in accordance with their compositions. The nanocomposite that was predominantly composed of a graphitic shell, encapsulated Fe nanoparticles and a negligible amount of Fe3C, showed the highest specific ab-sorption rate (760 W/gFe at 274 kHz), even at a relatively low AC-field amplitude (88 mT).(c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

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  • 26. Heathman, S.
    et al.
    Haire, R. G.
    Le Bihan, T.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, S.
    Luo, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    The unique high-pressure behavior of curiurn probed further using alloys2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 138-141Article in journal (Refereed)
    Abstract [en]

    The changing role of the 5f electrons across the actinide series has been of prime interest for many years. The remarkable behavior of americium's 5f electrons under pressure was determined experimentally a few years ago and it precipitated a strong interest in the heavy element community. Theoretical treatments of americium's behavior under pressure followed and continue today. Experimental and theoretical findings regarding curium's behavior under pressure have shown that the pressure behavior of curium was not a mirror image of that for americium. Rather, one of the five crystallographic phases observed with curium (versus four for americium) was a unique monoclinic structure whose existence is due to a spin stabilization effect by curium's 5f(7) electronic configuration and its half-filled 5f-shell. We review briefly the behavior of pure curium under pressure but focus on the pressure behaviors of three curium alloys with the intent of comparing them with pure curium. An important experimental finding confirmed by theoretical computations, is that dilution of curium with its near neighbors is sufficient to prevent the formation of the unique C2/c phase that appears in pure Cm metal under pressure. As this unique C2/c phase is very sensitive to having a 5f7 configuration to maximize the magnetic spin polarization, dilution of this state with adjacent actinide neighbors reduces its stability.

  • 27. Hristea, Amalia
    et al.
    Popovici, Elisabeth-Jeanne
    Muresan, Laura
    Stefan, Maria
    Grecu, Rodica
    Johansson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Morpho-structural and luminescent investigations of niobium activated yttrium tantalate powders2009In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 471, no 1-2, p. 524-529Article in journal (Refereed)
    Abstract [en]

    Yttrium tantalate-based phosphors are a class of efficient luminescent materials used in medical imaging applications. The paper presents the influence of activator concentration, firing regime and flux nature on the crystalline structure, morphology and luminescent characteristics of niobium activated yttrium tantalate powders. Phosphors samples were prepared by solid-state reaction route and their properties were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) measurements and scanning electron microscopy (SEM).

  • 28.
    Huang, Wen
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Palonen, Heikki
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Droulias, Sotirios A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hartmann, Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Diffusion of hydrogen in ultra-thin V(001) layers2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 723, p. 484-487Article in journal (Refereed)
    Abstract [en]

    We report on investigations of the influence of one dimensional confinement on the diffusion of hydrogen, in the low concentration limit (alpha-phase). The confinement is obtained by utilising single crystal Fe/V(001) superlattices, in which hydrogen preferably resides in the V layers. The diffusion along the [110] direction in the V(001) layers can thereby be determined. Activation energy and attempt jump rates are extracted from an Arrhenius analysis. No effects are observed from the confinement on the hydrogen diffusion in the thickness range 7-28 monolayers (approximate to 1.1-4.2 nm) of V(001).

  • 29.
    Ivanov, Sergey
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Dept Inorgan Mat, Moscow 105064, Russia.
    Sarkar, Tapati
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bazuev, G. V.
    Russian Acad Sci, Inst Solid State Chem, Ural Branch, Ekaterinburg 620990, Russia.
    Kuznetsov, M. V.
    Russian Acad Sci, Inst Solid State Chem, Ural Branch, Ekaterinburg 620990, Russia.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Modification of the structure and magnetic properties of ceramic La2CoMnO6 with Ru doping2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 752, p. 420-430Article in journal (Refereed)
    Abstract [en]

    Effects of Ru doping on the structure and magnetic properties of La2CoMn1-xRuxO6 ceramics with different compositions (x = 0, 0.1, 0.2, 0.3, 0.5, 0.75, 1.0) have been investigated using a variety of complementary techniques (X-ray powder diffraction and photoelectron spectroscopy, electron microscopy, and magnetometry). Phase-pure polycrystalline samples were prepared by the conventional solid-state reaction method including high pressure (3000 kg/cm(2) ) treatment of the original mixture of reagents. X-ray diffraction analyses of the samples accompanied with Rietveld refinement suggested a change in the crystal structure upon doping: for 0 <= x <= 0.3 the structure of the samples is predominantly disordered orthorhombic (s.g. Pnma) which transformed to ordered monoclinic (s.g. P2(1)/n) for 0.5 <= x <= 1. This suggests that Ru doping induces (partial) cation order in the B-sublattice. Magnetic measurements indicated a low temperature ferromagnetic phase, and a positive value of the Curie-Weiss temperature (theta cw) was derived for all samples of composition x <= 0.75. However, the Curie temperature (T-c) and theta cw decreased with increasing Ru doping. These changes in Tc upon doping can be correlated to the changes in the nearest neighbor and next nearest neighbor exchange interactions. The sample with x =1 orders antiferromagnetically at approximately 25 K.

  • 30.
    Jiang, Guanzhong
    et al.
    Shandong Univ, Key Lab Liquid Solid Struct Evolut & Proc Mat, Minist Educ, Jinan, Shandong, Peoples R China;Shandong Univ, Suzhou Inst, Jinan, Shandong, Peoples R China.
    Qian, Zhao
    Shandong Univ, Key Lab Liquid Solid Struct Evolut & Proc Mat, Minist Educ, Jinan, Shandong, Peoples R China;Shandong Univ, Suzhou Inst, Jinan, Shandong, Peoples R China.
    Bououdina, Mohamed
    Univ Bahrain, Dept Phys, Coll Sci, Zallaq, Bahrain.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Liu, Xiangfa
    Shandong Univ, Key Lab Liquid Solid Struct Evolut & Proc Mat, Minist Educ, Jinan, Shandong, Peoples R China;Shandong Univ, Suzhou Inst, Jinan, Shandong, Peoples R China.
    Exploring pristine and Li-doped Mg2NiH4 compounds with potential lithium-storage properties: Ab initio insight2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 746, p. 140-146Article in journal (Refereed)
    Abstract [en]

    In this work, pure and Li-doped Mg2NiH4 hydrides are explored for potential Li-ion battery conversion anode materials applications from state-of-the-art Density functional theory. The most thermodynamically stable Li-doped Mg2NiH4 structure is determined, which possesses a smaller band gap than pure material and owns a theoretical specific capacity of 975.35 mA h g(-1) and an average voltage of 0.437 V (vs. Li+/Li-0). The Li-doping also improves the diffusion behavior of Li-ion in electrode material especially at 300 K, which implies the promising rate capability of the device at room temperature when the anode material is doped utilizing Li element. The non-empirical values of diffusion coefficients of Li-ion in both pure and Li-doped Mg2NiH4 system are also quantitatively determined from ab initio molecular dynamics. After Li-doping, the diffusion coefficient of Li-ion in the electrode is evidently increased to 1.791 x 10(-9) m(2) s(-1) from the pristine 1.431 x 10(-9) m(2) s(-1) at 300 K and the Li-ion conductivity is also increased. This theoretical study is proposed to encourage the design and experimental modification of better light-metal based hydrides for Li-ion battery conversion anodes applications.

  • 31.
    Johansson, Börje
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Li, Sa
    The actinides - a beautiful ending of the Periodic Table2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 202-206Article in journal (Refereed)
    Abstract [en]

    The 5f elements, actinides, show many properties which have direct correspondence to the 4f transition metals, the lanthanides. The remarkable similarity between the solid state properties of compressed Ce and the actinide metals is pointed out in the present paper. The alpha-gamma transition in Ce is considered as a Mott transition, namely, from delocalized to localized 4f states. An analogous behavior is also found for the actinide series, where the sudden volume increase from Pu to Am can be viewed upon as a Mott transition within the 5f shell as a function of the atomic number Z. On the itinerant side of the Mott transition, the earlier actinides (Pa-Pu) show low symmetry structures at ambient conditions; while across the border, the heavier elements (Am-Cf) present the dhcp structure, an atomic arrangement typical for the trivalent lanthanide elements with localized 4f magnetic moments. The reason for an isostructural Mott transition of the f electron in Ce, as opposed to the much more complicated cases in the actinides, is identified. The strange appearance of the delta-phase (fcc) in the phase diagram of Pu is another consequence of the border line behavior of the 5f electrons. The path leading from delta-Pu to alpha-Pu is identified.

  • 32.
    Johansson, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of oxygen content on structure and material properties of reactively sputtered Al-Ge-O-N thin films2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 738, p. 515-527Article in journal (Refereed)
    Abstract [en]

    Ternary Al-Ge-N and quaternary Al-Ge-O-N coatings were deposited by reactive dc magnetron cosputtering of Al and Ge targets in an Ar/N-2 or Ar/N-2/O-2 atmosphere at a substrate temperature of 250 degrees C. The structure and material properties of the coatings were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), nanoindentation, UV-vis spectroscopy and optical profilometry. In agreement with literature, the ternary Al-Ge-N coatings were found to be nanocomposite materials with nanocrystalline (Al1-xGex) N-y solid solution phase in a Ge3N4-z amorphous matrix. The Al-Ge-O-N coatings consisted of a nanocrystalline wurzite-type (Al1-xGex)( N1-yOy) solid solution phase for low oxygen concentrations with a possible co-existence of an amorphous Ge-N matrix phase. For higher O contents, the coatings became X-ray amorphous. The mechanical properties of the Al-Ge-O-N films were improved for low oxygen content, as compared to the ternary Al-Ge-N samples, showing an increase in hardness up to 29 GPa and Young's modulus to 320 GPa. The oxygen addition also resulted in an additional design parameter of the optical properties compared to the ternary Al-Ge-N films. The optical absorption edge was thus tuneable towards both shorter and longer wavelength by changing the O and Ge content respectively, and ranged from 302 to 373 nm, corresponding to an optical bandgap (E-04) between 4.1 and 3.3 eV. After annealing of the Al-Ge-O-N coatings in ultra-high vacuum at 500 degrees C, indications of increased thermal stability for the coating with high oxygen content were observed. For the annealed Al-Ge-O-N films the mechanical properties were improved upon heat treatment, while the optical properties were only slightly changed. These results suggests that coatings of the Al-Ge-O-N system could be suitable as protective optical coatings at elevated temperatures.

  • 33.
    Karlsson, Dennis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Beran, Premysl
    Nuclear Physics Institute, Academy of Sciences of the Czech Republic, 25068 Rez, Czech Republic and European Spallation Source ESS ERIC, Box 176, SE-221 00 Lund, Sweden.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tseng, Jo-Chi
    Deutsches Elektronen Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg, Germany.
    Harlin, Peter
    Sandvik Additive Manufacturing, Sandvik AB, Box 510, SE-101 30 Stockholm, Sweden.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, SE-106 91 Stockholm, Sweden.
    Structure and Phase Transformations in Gas Atomized AlCoCrFeNi High Entropy Alloy Powders2022In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 893, article id 162060Article in journal (Refereed)
    Abstract [en]

    In this study, the crystal structure and phase stability of gas atomized equiatomic AlCoCrFeNi powder was investigated. This alloy is usually described as a high entropy alloy forming a solid solution phase stabilized by a high mixing entropy. However, thermodynamic calculations show that the high entropy phase is stable only at very high temperatures close to the melting point and that a mixture of several phases are the most stable state at lower temperatures. This suggest that kinetic effects may influence the phase composition of atomized powder. The unique features of X-ray diffraction, neutron diffraction as well as transmission electron microscopy were used to study the atomic structure of the atomized powder in detail. The results show that the powder crystallises in an ordered B2 (CsCl-type) structure with a preferred site occupation of Al and Fe on the (½ ½ ½) position and Co and Ni on the (0 0 0) position. During heat-treatment of the powder, the B2 phase decomposes into fcc and σ phases and the final phase composition is highly dependent on the heating rate. The effect of heat-treatment on the atomized powder was also investigated and revealed a significant phase transformation with e.g. the formation of σ phase preferably at the surface of the powder particles. The phase content was also dependent on the size fraction of the powder particles. Sintering of green bodies made with different heat cycles showed that the phase composition of the starting material had a significant impact on the final phase composition and microstructure of the sintered components. The results illustrate the importance of well-defined powder materials for powder consolidation, especially additive manufacturing (binder jetting) of high entropy alloys.

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  • 34.
    Karlsson, Dennis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Marshal, Amalraj
    Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany.
    Johansson, Filip
    Sandvik Machining Solut AB, Sandvik Addit Mfg, Mossvagen 10, SE-81181 Sandviken, Sweden.
    Schuisky, Mikael
    Sandvik Machining Solut AB, Sandvik Addit Mfg, Mossvagen 10, SE-81181 Sandviken, Sweden.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Schneider, Jochen M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström. Rhein Westfal TH Aachen, Mat Chem, Kopernikusstr 10, D-52074 Aachen, Germany.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Elemental segregation in an AlCoCrFeNi high-entropy alloy: A comparison between selective laser melting and induction melting2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 784, p. 195-203Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing of a high-entropy alloy, AlCoCrFeNi, was studied with selective laser melting from gas atomized powder. A wide process parameter window in the SLM process was investigated but it was impossible to produce crack-free samples, attributed to stresses that originate during the building processes. The microstructure and elemental segregation in the SLM samples were compared with induction-melted AlCoCrFeNi. The induction-melted sample crystallizes in randomly oriented large grains (several hundred microns). Dendritic and inter-dendritic areas with slightly different chemical composition can be observed. Within these areas a spinodal decomposition occurs with a separation into FeCr- and NiAl-rich domains. Further spinodal decomposition within the FeCr-rich regions into Cr- and Fe-rich domains was observed by atom probe tomography.

    In contrast, the SLM-samples crystallizes in much smaller grains (less than 20 μm) with a dendrite-like substructure. These dendrite-like features exhibit distinct chemical fluctuations on the nm-scale. During annealing more pronounced chemical fluctuations and the formation of Cr-rich and Cr-poor regions can be observed. The difference in microstructure and spinodal decomposition between the induction-melted and SLM samples is attributed to the significantly higher cooling rate for SLM. This study shows that, by using different synthesis pathways, it is possible to modify the microstructure and segregation of element within alloys. This can be used to tune the materials properties, if the cracking behavior is handled e.g. by change of alloy composition to minimize phase transformations or use of a heating stage.

  • 35. Kulkarni, Shrinivas R.
    et al.
    Vennila, R. Selva
    Phatak, Nishad A.
    Saxena, S. K.
    Zha, C. S.
    El-Raghy, T.
    Barsoum, M. W.
    Luo, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Study of Ti2SC under compression up to 47 GPa2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 448, no 1-2, p. L1-L4Article in journal (Refereed)
    Abstract [en]

    The pressure dependence of the lattice parameters of the ternary layered carbide, Ti2SC, was measured by using synchrotron radiation X-ray diffraction and a diamond anvil cell setup. The experiment was conducted at room temperature and no phase transformation was observed up to the maximum pressure of 47 GPa. The a and c lattice parameters at room condition are 3.216 (A) over circle and 11.22 (A) over circle, respectively. The bulk modulus, calculated using the Birch-Murnaghan equation of state, is 191 +/- 3 GPa, with a pressure derivative of 4.0 +/- 0.3 and that obtained by our ab initio calculations is 183 GPa, with a pressure derivative of 4.1. L Like the majority of the ternary layered carbides (MAX phases), compressibility along the c-axis was higher than that along the a-axis.

  • 36.
    Kumar, Anil P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Univ Duisburg Essen, Fac Phys, Lotharstr 1, D-47048 Duisburg, Germany.;Univ Duisburg Essen, Ctr Nanointegrat Duisburg Essen CENIDE, Lotharstr 1, D-47048 Duisburg, Germany..
    Ivanov, Sergey
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpov Inst Phys Chem, Ctr Mat Sci, Vorontsovo Pole 10, Moscow 105064, Russia..
    Ritter, Clemens
    Inst Laue Langevin, BP 156, F-38042 Grenoble, France..
    Vijayaraghavan, R.
    VIT Univ, Sch Adv Sci, Mat Chem Div, Vellore 632014, Tamil Nadu, India..
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sadovskaya, N.
    Karpov Inst Phys Chem, Ctr Mat Sci, Vorontsovo Pole 10, Moscow 105064, Russia..
    Sarma, Dipankar Das
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Indian Inst Sci, Solid State & Struct Chem Unit, Bengaluru 560012, India.;Jawaharlal Nehru Ctr Adv Sci Res, Bengaluru, India..
    Composition driven structural transition in La2-xSrxCuRuO6 (0 <= x <= 1) double perovskites2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 693, p. 1096-1101Article in journal (Refereed)
    Abstract [en]

    We report results of detailed structural investigations on the system La2-xSrxCuRuO6 (0 <= x <= 1) as a function of composition using neutron powder diffraction. Our results reveal that this series of compounds exhibit an interesting structural transition manifested through Sr doping; with Ru in single valency, in end members, and mixed valency otherwise. The end members La2CuRuO6 and LaSrCuRuO6 crystallize in monoclinic structures with space group P2(1)/n. However, the compositions with intermediate Sr doping (x = 0.2 and 0.8) crystallize in triclinic structure with space group P-1, albeit with minute distortions. The detailed structural studies by neutron powder diffraction at room temperature and at 10 K, for compositions, x = 0.2, 0.8 and 1 are presented. While magnetic measurements are indicative of ferro and antiferromagnetic like transitions for x = 0 and x > 0 respectively, neutron diffraction patterns collected at 10 K and 30 K across the characteristic transition temperature suggested by the magnetic data, do not show any extra peaks or extra intensity at lower temperature as compared to the high temperature, thus, establishing the absence of any long-range magnetic ordering in these samples.

  • 37.
    Larsen, Simon R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Christensen, Christian K.
    DESY, Photon Sci Div, Notkestr 85, D-22607 Hamburg, Germany.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Magnetic properties and thermal stability of B2 and bcc phases in AlCoCrFeMnxNi2021In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 861, article id 158450Article in journal (Refereed)
    Abstract [en]

    Alloys of AlCoCrFeMnxNi (x = 0.0, 0.04, 0.08, 0.12 and 0.16) have been synthesized through arc–melting and gas atomisation (x = 0.0 and 0.16) to investigate the effect of Mn additions to AlCoCrFeNi. Here, the structure, magnetic properties and the thermal stability of the alloys is presented. Electron microscopy confirmed the elemental composition and revealed the microstructure to consist of two spinodally decomposed phases. Rietveld analysis of standard powder X-ray diffraction showed the arc-melted samples consisted of two phases, a B2 phase and a bcc phase while the gas atomised powders consisted of a single-phased B2 structure. Magnetic measurements revealed an increase in the saturation magnetisation at room temperature by 68% for AlCoCrFeMnNi compared to AlCoCrFeNi. The thermal stability of the alloys was investigated using magnetometry, differential scanning calorimetry and in–situ X-ray diffraction, which showed that an increase in Mn content adversely effected the thermal stability of the alloy.

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  • 38. Lee, Jae-chul
    et al.
    Lee, Ji-eun
    Lee, Ju-won
    Lee, Jae-choon
    Subramaniam, N. G.
    Kang, Tae-won
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Se concentration dependent band gap engineering in ZnO1-xSex thin film for optoelectronic applications2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 585, p. 94-97Article in journal (Refereed)
    Abstract [en]

    ZnO1-xSex films with various selenium concentrations are deposited on the sapphire substrate (0001) by pulsed laser deposition technique. Structural properties of the thin films studied by X-ray diffraction (XRD) and chemical bonding studied by X-ray photoelectron spectroscopy (XPS) reveals that Se is substituted in O site during the growth of ZnO1-xSex films. Optical properties are analyzed by UV-Visible spectrometer. From the plot for (alpha h upsilon)(2) vs photon energy, it is inferred that the band gap energy of ZnO1-xSex gradually reduces to 2.85 eV with increasing Se concentration.

  • 39.
    Leitao, J. V.
    et al.
    Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TU Delft, Nederländerna.
    Xinmin, You
    Nanjing University of Technology, Kina.
    Caron, Luana
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bruck, E.
    Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, TU Delft, Nederländerna.
    Magnetostructural study of the (Mn,Fe)3(P,Si) system2012In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 520, p. 52-58Article in journal (Refereed)
    Abstract [en]

    Using X-ray diffraction, DSC and magnetization measurements, a magnetostrutural map of the (Mn,Fe)(3)(Si,P) system was assembled and reported in the current paper. Besides the already known cubic phase for Mn3-xFexSi system and the tetragonal and orthorhombic phases for the Mn3-xFexP system, a novel hexagonal phase has been observed for Mn3-xFexSi1-yPy, within the approximate range of 0.2 < x < 2.0 and 0.2 < y < 0.9. Magnetization measurements both confirm and further detail the already known properties of the Mn3-xFexSi and Mn3-xFexP systems.

  • 40.
    Lewin, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Empa, Lab Nanoscale Mat Sci, Uberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Patscheider, Jörg
    Empa, Lab Nanoscale Mat Sci, Uberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Structure and properties of sputter-deposited Al-Sn-N thin films2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 682, p. 42-51Article in journal (Refereed)
    Abstract [en]

    Coatings consisting of Al, Sn and N have been deposited using co-sputtering from Al and Sn targets in a reactive atmosphere containing N-2. AlN was used as starting point, and the Sn content was gradually increased through higher cathode power on the Sn target, resulting in coatings with Sn-contents between 0 and 24 at.%. The coatings were analysed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) and also characterised using UV-vis spectroscopy and nanoindentation. All coatings show a nitrogen content of about 50 at.% and are thus fully nitrided, which is confirmed by bonding analysis with XPS. A combination of results from XRD and XPS leads to the conclusion that the coatings consist of a single phase solid solution based on wurzite (Al1-xSnx) N-y with x varying between 0 and 0.5, and y close to unity. The attained material is metastable with respect to decomposition into AlN, Sn and N-2, as shown by sputter damages occurring during Ar+ ion etching. The top surface and cross sections, as observed in SEM, were found to become smoother and the columnar structure less pronounced, changing to grainy and finally glass like morphology, as the Sn content is increased. The material is hard at room temperature, with nanoindentation values of 17-24 GPa. Coatings on silica substrates are transparent and yellow to red-brown in colour. This is quantified as a shifting absorption edge, which moves from 211 to 510 nm, corresponding to an optical band gap of 5.9 and 2.4, respectively, as the Sn-content is increased. The index of refraction varies between 2.0 and 2.6. The deposited materials are thus hard, and have a tuneable absorption edge, which could be applicable in optical applications as a multifunctional optical filter with scratch resistant properties.

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  • 41.
    Li, Xiaoqing
    et al.
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Schönecker, Stephan
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Zhao, Jijun
    Dalian Univ Technol, Sch Phys & Optoelect Technol, Dalian 116024, Peoples R China.;Dalian Univ Technol, Coll Adv Sci & Technol, Dalian 116024, Peoples R China.;Dalian Univ Technol, Minist Educ, Key Lab Mat Modificat Laser Elect & Ion Beams, Dalian 116024, Peoples R China..
    Johansson, Börje
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Alloying effect on the ideal tensile strength of ferromagnetic and paramagnetic bcc iron2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 676, p. 565-574Article in journal (Refereed)
    Abstract [en]

    Using ab initio alloy theory formulated within the exact muffin-tin orbitals theory in combination with the coherent potential approximation, we investigate the ideal tensile strength (ITS) in the [001] direction of bcc ferro-/ferrimagnetic (FFM) and paramagnetic (PM) Fe1-xMx (M = Al, V, Cr, Mn, Co, or Ni) random alloys. The ITS of ferromagnetic (FM) Fe is calculated to be 12.6 GPa, in agreement with available data, while the PM phase turns out to posses a significantly lower value of 0.7 GPa. Alloyed to the FM matrix, we predict that V, Cr, and Co increase the ITS of Fe, while Al and Ni decrease it. Manganese yields a weak non-monotonic alloying behavior. In comparison to FM Fe, the alloying effect of Al and Co to PM Fe is reversed and the relative magnitude of the ITS can be altered more strongly for any of the solutes. All considered binaries are intrinsically brittle and fail by cleavage of the (001) planes under uniaxial tensile loading in both magnetic phases. We show that the previously established ITS model based on structural energy differences proves successful in the PM Fe-alloys but is of limited use in the case of the FFM Fe-based alloys. The different performance is attributed to the specific interplay between magnetism and volume change in response to uniaxial tension. We establish a strong correlation between the compositional effect on the ITS and the one on the shear elastic constant C' for the PM Fe-alloys and briefly discuss the relation between hardenability and the ITS.

  • 42.
    Li, Xiaoqing
    et al.
    Royal Inst Technol KTH, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
    Wei, Daixiu
    Tohoku Univ, Inst Mat Res, 2-1-1 Katahira, Sendai, Miyagi 9808577, Japan.
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden;Wigner Res Ctr Phys, Res Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary.
    Lizarraga, Raquel
    Royal Inst Technol KTH, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
    Micro-mechanical properties of new alternative binders for cemented carbides: CoCrFeNiWx high-entropy alloys2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 820, article id 153141Article in journal (Refereed)
    Abstract [en]

    High-entropy alloys are a new type of materials with excellent properties that offer a great variety of possibilities due to the large degree of freedom in element composition. In particular, CoCrFeNiW alloys have recently attracted a lot of attention due to their potential use in solving the long-standing problem of substituting cobalt in the cemented carbide industry. The lack of experimental and theoretical studies on these multi-components alloys hinders their optimal development. In this work, we aim at filling in this gap by studying their mechanical properties employing first-principles alloy theory and experimental techniques. By using the calculated elastic parameters, we analyzed the mechanical stability, elastic anisotropy, Debye temperature, and derived polycrystalline moduli. Moreover, we fabricated CoCrFeNi and (CoCrFeNi)(0.)W-96(0.04) and analyzed them by means of X-ray diffraction and electron backscatter diffraction. The hardness and the Young's modulus were measured. The Young's moduli and the lattice parameters were compared to first principles calculations and good agreement was obtained. Hardness increases with the increment of W composition. 

  • 43.
    Liao, Xiaoqi
    et al.
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Wang, Yu
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Wetterskog, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Cheng, Fei
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Hao, Chunxi
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Khan, Muhammad Tahir
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Zheng, Yan-Zhen
    Xi An Jiao Tong Univ, Frontier Inst Sci & Technol, Multidisciplinary Mat Res Ctr, Xian 710049, Shaanxi, Peoples R China.
    Yang, Sen
    Xi An Jiao Tong Univ, MOE Key Lab Nonequilibrium Synth & Modulat Conden, Xian 710049, Shaanxi, Peoples R China;Xi An Jiao Tong Univ, State Key Lab Mech Behav Mat, Xian 710049, Shaanxi, Peoples R China.
    Superposition of conventional and spontaneous exchange bias in a Ni50Mn34In13Fe3 magnetic shape memory alloy2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 772, p. 988-993Article in journal (Refereed)
    Abstract [en]

    The conventional exchange bias and spontaneous exchange bias are two interesting but fundamentally different effects in Mn rich Ni-Mn-Z magnetic shape memory alloys. Previous investigations show that these two phenomena appear separately. Here, we report that the conventional and spontaneous exchange bias phenomena coexist in a Ni50Mn34In13Fe3 alloy and the superposition of them increases the total exchange bias of the alloy. Our results suggest that the canonical spin glass and super spin glass may coexist and are embedded in the antiferromagnetic matrix of the martensite, through properly tuning the temperature-field history, which further results in the superposition of conventional and spontaneous exchange bias for this alloy. The interfacial interaction between the canonical spin glass and the antiferromagnetic matrix forms during field cooling process, which results in the conventional exchange bias. Moreover, the application of large magnetic field during the isothermal magnetization process changes the superspin glass into a superferromagnetic state, which interacts with the antiferromagnetic matrix at the interface, causing the spontaneous exchange bias. The superposition of exchange bias provides an effective way to achieve large exchange bias in materials. (C) 2018 Elsevier B.V. All rights reserved.

  • 44.
    Liu, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Ivanov, Sergey
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Karpovs Inst Phys Chem, Dept Inorgan Mat, Moscow 105046, Russia.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Weil, Matthias
    Vienna Univ Technol, Inst Chem Technol & Analyt, A-1060 Vienna, Austria.
    Li, Xiaodong
    Chinese Acad Sci, Inst High Energy Phys, Beijing Synchrotron Radiat Facil, Beijing 100049, Peoples R China.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Pressure tuning of octahedral tilt in the ordered double perovskite Pb2CoTeO62019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 801, p. 310-317Article in journal (Refereed)
    Abstract [en]

    Double perovskites represent a family of materials with promising fundamental properties (e.g. multiferroicity) and vast potential applications. However, the knowledge of pressure effects on the crystal structure of double perovskite is limited, which hinders their efficient synthesis using high-pressure techniques. Pb2CoTeO6 (PCTO) is considered as a good candidate for multiferroic materials, although a polymorph with a polar structure has not been synthesized yet. In the present study, the pressure effect on the crystal structure of PCTO was systematically studied by employing in situ synchrotron X-ray powder diffraction and Raman scattering techniques up to 60 GPa. A structural phase transition from R-3 to I2/m structure was observed at around 20 GPa, indicating that increasing the pressure has a similar effect on PCTO as decreasing the temperature, i.e., promoting the distortion of the structure. No polar structure of PCTO has been observed in the applied pressure range. The present study provides a valuable information about the crystal structure evolution of double perovskites upon compression, and will benefit high-pressure syntheses of novel double perovskites in the future. 

  • 45.
    Liu, Yang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Harbin Institute of Technology.
    Zhang, mingfu
    Harbin Institute of Technology.
    Wu, Dan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wang, Tao
    Harbin Institute of Technology.
    Ying, Nie
    Harbin Institute of Technology.
    Han, Jiecai
    Harbin Institute of Technology.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Microstructures and mechanical properties of Al2O3/YAG:Ce3+ eutectics with different Ce3+concentrations grown by HDS method2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669Article in journal (Refereed)
  • 46.
    Luo, Wei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ab initio prediction of high-pressure structural phase transition in BaH22007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 446, p. 405-408Article in journal (Refereed)
    Abstract [en]

    We have performed ab initio electronic structure calculations to calculate the structural properties and high-pressure phase transition in Barium dihydride (BaH2). Our results show that BaH2 crystallizes the orthorhombic phase (CoSi2-type structure) with Pnma space group at ambient conditions. A phase transition to the hexagonal (Ni2In-type structure) with P6(3)/mmc space group is found at pressure around 4 GPa. At the phase transition, the coordination number of hydrogen increases from 9 to 11 and the average bond length of Ba-H increases. The results show a band gap of 2.9 eV for orthorhombic and 1.8 eV for hexagonal phase. In addition, it was also found that more energy is required to desorb hydrogen atom from high-pressure phase as compared to ambient phase.

  • 47. Ma, Ming-Guo
    et al.
    Zhu, Jie-Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Cao, Shao-Wen
    Chen, Feng
    Sun, Run-Cang
    Hydrothermal synthesis of relatively uniform CePO4@LaPO4 one-dimensional nanostructures with highly improved luminescence2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 492, no 1-2, p. 559-563Article in journal (Refereed)
    Abstract [en]

    Using monoclinic CePO4 as cores, uniform CePO4@LaPO4 single-crystalline one-dimensional nanostructures have been successfully synthesized via a facile and simple hydrothermal method. The CePO4@LaPO4 one-dimensional nanostructures have highly enhanced photoluminescent emission compared to the pure-phase CePO4. The uniform LaPO4 sheaths effectively eliminated surface trap-states and remarkably increase the luminescent efficiency. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectra (EDS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL).

  • 48. Manoun, B.
    et al.
    Benmokhtar, S.
    Bih, L.
    Azrour, M.
    Ezzahi, A. Ider
    Azdouz, M.
    Annersten, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Synthesis, structure, and high temperature Mössbauer and Raman spectroscopy studies of Ba1.6Sr1.4Fe2WO9 double perovskite2011In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, no 1, p. 66-71Article in journal (Refereed)
    Abstract [en]

    Ba1.6Sr1.4Fe2WO9 has been prepared in polycrystalline form by solid-state reaction method in air, and has been studied by X-ray powder diffraction method (XRPD), and high temperature Mössbauer and Raman spectroscopies. The crystal structure was resolved at room temperature by the Rietveld refinement method, and revealed that Ba 1.6Sr1.4Fe2WO9 crystallizes in a tetragonal system, space group I4/m, with a = b = 5.6489(10), c = 7.9833(2) and adopts a double perovskite-type A3B′2B″O 9 (A = Ba, Sr; B′ = Fe/W, and B″ = Fe/W) structure described by the crystallographic formula (Ba1.07Sr 0.93)4d(Fe0.744W0.256) 2a(Fe0.585W0.415)2bO6. The structure contains alternating [(Fe/W)2aO6] and [(Fe/W)2bO6] octahedra. Mössbauer studies reveal the presence of iron in the 3+ oxidation state. The high temperature Mössbauer measurements showed a magnetic to paramagnetic transition around 405 ± 10 K. The transition is gradual over the temperature interval. The decrease in isomer shift is in line with the general temperature dependence. While the isomer shift is rather linear over the whole temperature range, the quadratic dipolar ΔE temperature dependence shows an abrupt change at 405 K. The latter results allow concluding that a temperature-induced phase transition had occurred. The high temperature Raman study confirms the Mössbauer results on the magnetic to paramagnetic transition.

  • 49. Manoun, Bouchaib
    et al.
    Ezzahi, A.
    Benmokhtar, S.
    Ider, A.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Bih, L.
    Igartua, J. M.
    X-ray diffraction and Raman spectroscopy studies of temperature and composition induced phase transitions in Ba2-xSrxZnWO6 (0 <= x <= 2) double perovskite oxides2012In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 533, p. 43-52Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction and Raman spectroscopy studies of Sr doped double perovskites compound Ba2-xSrxZnWO6 with (0 <= x <= 2) were investigated. As a function of composition while increasing strontium amount, the samples show two phase transitions from cubic to tetragonal phase and from tetragonal to monoclinic structure. Both Rietveld refinements and Raman studies showed that the first phase transition occurs between x = 1 and 1.2; the second phase transition is observed around x = 2. Furthermore, increasing the temperature for the compositions (1.2 <= x <= 2), manifests the tetragonal to cubic phase transition. For x = 2 two phase transitions were observed as a function of temperature. For this series, the phase transitions are illustrated by considerable changes in the composition and temperature dependence of the modes. All the Raman modes show a linear behavior when the composition or temperature is increased, then the slope change indicating the symmetry change.

  • 50.
    Manoun, Bouchaib
    et al.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Mirinioui, F.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Tamraoui, Y.
    Univ Hassan 1er, LS3M, Khouribga 25000, Morocco..
    Solhy, A.
    Mohammed VI Polytech Univ, CAM, Lot 660 Hay Moulay Rachid, Ben Guerir 43150, Morocco..
    Yang, Wenge
    HPSTAR, Shanghai 201203, Peoples R China.;Carnegie Inst Sci, Geophys Lab, HPSynC, Argonne, IL 60439 USA..
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Temperature and nickel substitution effects on the phase transitions in the Sr2Zn1-xNixWO6 ( 0 <= x <= 1) double perovskite2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 689, p. 233-245Article in journal (Refereed)
    Abstract [en]

    Sr2Zn1-xNixWO6 solid solutions (with 0 <= x <= 1) have been synthesized by solid-state reactions, and characterized by X-Ray diffraction and Raman spectroscopy. The X-Ray powder diffraction (XRD) data at room temperature shows a systematical change of structure vs. nickel content: the compound adopts a monoclinic phase with a P2(1)/n space group with 0 <= x <= 0.18, a tetragonal structure with a I4/m space group with x = 0.25, and a tetragonal structure with a I4/mmm space group with 0.5 <= x <= 1. Further in-situ Raman study at elevated temperature (up to 555 degrees C) shows the pristine monoclinic phase (0 <= x <= 0.18) follows the phase path: monoclinic (P2(1)/n) -> tetragonal (I4/m) -> tetragonal (I4/ mmm) -> cubic (Fm (3) over barm); for the compound Sr2Zn0.75Ni0.25WO6, it involves later two phase transitions as tetragonal (I4/m) -> tetragonal (I4/mmm) -> cubic (Fm (3) over barm); and for the 0.5 <= x <= 1 compounds, only one phase transition I4/mmm to Fm (3) over barm was observed. The combined investigation of composition and temperature provides us a complete understanding of chemical substitution and temperature effect on structural phase transition.

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