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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. 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.

  • 3. 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. 

  • 4. 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

    .

  • 5.
    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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  • 6.
    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.

  • 7.
    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.

  • 8. 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.

  • 9. 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.

  • 10.
    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.

  • 11.
    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. 

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15. 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)
  • 16.
    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.

  • 17. 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.

  • 18. 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.

  • 19. 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).

  • 20.
    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).

  • 21.
    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.

  • 22.
    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.

  • 23.
    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.

  • 24.
    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.

  • 25.
    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.

  • 26. 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.

  • 27.
    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.

  • 28. 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.

  • 29.
    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.

  • 30.
    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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  • 31.
    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.

  • 32.
    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. 

  • 33.
    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.

  • 34.
    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. 

  • 35.
    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)
  • 36.
    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.

  • 37. 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).

  • 38. 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.

  • 39. 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.

  • 40.
    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.

  • 41.
    Marattukalam, Jithin J.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. Natl Inst Technol Karnataka, Dept Met & Mat Engn, Srinivasnagar PO, Mangalore 575025, India.
    Balla, Vamsi K.
    CSIR Cent Glass & Ceram Res Inst, Bioceram & Coating Div, 196 Raja SC Mullick Rd, Kolkata 700032, India..
    Das, Mitun
    CSIR Cent Glass & Ceram Res Inst, Bioceram & Coating Div, 196 Raja SC Mullick Rd, Kolkata 700032, India..
    Bontha, Srikanth
    Natl Inst Technol Karnataka, Dept Mech Engn, Srinivasnagar PO, Mangalore 575025, India..
    Kalpathy, Sreeram K.
    Indian Inst Technol, Dept Met & Mat Engn, Madras 600036, Tamil Nadu, India..
    Effect of heat treatment on microstructure, corrosion, and shape memory characteristics of laser deposited NiTi alloy2018In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 744, p. 337-346Article in journal (Refereed)
    Abstract [en]

    The aim of this work is to study the effect of heat treatment on the microstructure, phase transformations, shape memory characteristics and corrosion behaviour of laser deposited equiatomic NiTi alloy. Dense samples of NiTi alloy were fabricated using Laser Engineered Net Shaping (LENS T) with two different laser energy densities by varying the scan speed and laser power. These samples were annealed for 30 min at 500 degrees C and 1000 degrees C in flowing argon, followed by furnace-cooling to room temperature. The resulting microstructures and properties were compared with the corresponding as-deposited samples. Microstructural analysis after heat treatment showed needle-shape martensite in the samples processed at lower laser energy density of 20 J/mm(2), and lenticular or plate-like martensite in the samples processed at 80 J/mm(2). The XRD results revealed relatively high concentration of martensite (B190) in heat-treated NiTi alloy compared to as-processed samples. Furthermore, the heat treatment decreased the forward and reverse transformation temperatures of NiTi alloy from 80 - 95 degrees C to 20-40 degrees C, presumably due to annihilation of thermally induced defects. Interestingly, the samples annealed at 500 degrees C showed a measurable increase of 1-2% in the shape memory recovery, from the net recovery of 8% exhibited by the as-processed NiTi alloy. The corrosion resistance of laser-processed NiTi alloy decreased upon annealing.

  • 42.
    Migas, D. B.
    et al.
    Belarusian State Univ Informat & Radioelect, P Browki 6, Minsk 220013, BELARUS;Natl Res Nucl Univ MEPhI, Moscow Engn Phys Inst, Kashirskoe Shosse 31, Moscow 115409, Russia.
    Filonov, A. B.
    Belarusian State Univ Informat & Radioelect, P Browki 6, Minsk 220013, BELARUS.
    Borisenko, V. E.
    Belarusian State Univ Informat & Radioelect, P Browki 6, Minsk 220013, BELARUS;Natl Res Nucl Univ MEPhI, Moscow Engn Phys Inst, Kashirskoe Shosse 31, Moscow 115409, Russia.
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat & Engn, Multiscale Mat Modelling, SE-10044 Stockholm, Sweden.
    Effect of polaron formation on electronic, charge and magnetic properties of Nb12O292020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 821, article id 153527Article in journal (Refereed)
    Abstract [en]

    We present the ab initio study of different phases of Nb12O29, which has been done in the framework of density functional theory using the onsite Hubbard-U correction applied to the Nb-d states. We vary the U parameter in between 0 and 7 eV and suggest U = 3.7–5.0 eV to be most appropriate for the description of Nb12O29. We show that one cannot get any adequate description of this oxide using the crystallographic unit cell but at least 3 times larger supercell is needed increased along the shortest lattice parameter b to accommodate lattice distortions associated with polaron formation. Our results obtained for the enlarged cells show the possibility of simultaneous co-existence of localized states (polaron formation) and delocalized states providing metal-like properties of Nb12O29, in qualitative agreement with available experimental data.

  • 43.
    Mongstad, T
    et al.
    Institute for Energy Technology, Kjeller, Norge.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Karazhanov, S Zh
    Institute for Energy Technology, Kjeller, Norge.
    Holt, A
    Institute for Energy technology, Kjeller, Norge.
    Maehlen, J P
    Institute for Energy Technology, Kjeller, Norge.
    Hauback, B C
    Institute for Energy Technology, Kjeller, Norge.
    Transparent yttrium hydride thin films prepared by reactive sputtering2011In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 509, p. S812-S816Article in journal (Refereed)
    Abstract [en]

    Metal hydrides have earlier been suggested for utilization in solar cells. With this as a motivation we have prepared thin films of yttrium hydride by reactive magnetron sputter deposition. The resulting films are metallic for low partial pressure of hydrogen during the deposition, and black or yellow-transparent for higher partial pressure of hydrogen. Both metallic and semiconducting transparent YH(x) films have been prepared directly in situ without the need of capping layers and post-deposition hydrogenation. Optically the films are similar to what is found for YH(x) films prepared by other techniques, but the crystal structure of the transparent films differ from the well-known YH(3-eta) phase, as they have an fcc lattice instead of hcp.

  • 44.
    Mongstad, Trygve
    et al.
    Institute for Energy Technology, Kjeller, Norge.
    You, C. C.
    Institute for Energy Technology, Kjeller, Norge.
    Thogersen, A.
    Institute for Energy Technology, Kjeller, Norge.
    Maehlen, J. P.
    Institute for Energy Technology, Kjeller, Norge.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hauback, B. C.
    Institute for Energy Technology, Kjeller, Norge.
    Karazhanov, S. Zh
    Institute for Energy Technology, Kjeller, Norge.
    MgyNi1-y(H-x) thin films deposited by magnetron co-sputtering2012In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 527, p. 76-83Article in journal (Refereed)
    Abstract [en]

    In this work we have synthesized thin films of MgyNi1-y(H-x) metal and metal hydride with y between 0 and 1. The films are deposited by magnetron co-sputtering of metallic targets of Mg and Ni. Metallic MgyNi1-y films were deposited with pure Ar plasma while MgyNi1-yHx hydride films were deposited reactively with 30% H-2 in the Ar plasma. The depositions were done with a fixed substrate carrier, producing films with a spatial gradient in the Mg and Ni composition. The combinatorial method of co-sputtering gives an insight into the phase diagram of MgyNi1-y and MgyNi1-yHx, and allows us to investigate structural, optical and electrical properties of the resulting alloys. Our results show that reactive sputtering gives direct deposition of metal hydride films, with high purity in the case of Mg similar to 2NiH similar to 4. We have observed limited oxidation after several months of exposure to ambient conditions. MgyNi1-y and MgyNi1-yHx films might be applied for optical control in smart windows, optical sensors and as a semiconducting material for photovoltaic solar cells.

  • 45.
    Muscas, Giuseppe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Jovanovic, S.
    Univ Belgrade, Lab Phys, Vinca Inst Nucl Sci, POB 522, Belgrade 11001, Serbia;Jozef Stefan Inst, Adv Mat Dept, Jamova 39, Ljubljana 1000, Slovenia.
    Vukomanovic, M.
    Jozef Stefan Inst, Adv Mat Dept, Jamova 39, Ljubljana 1000, Slovenia.
    Spreitzer, M.
    Jozef Stefan Inst, Adv Mat Dept, Jamova 39, Ljubljana 1000, Slovenia.
    Peddis, D.
    Univ Genoa, Dipartimento Chim & Chim Ind, Via Dodecaneso 31, I-16146 Genoa, Italy;CNR, Ist Struttura Mat, I-00015 Monterotondo, RM, Italy.
    Zn-doped cobalt ferrite: Tuning the interactions by chemical composition2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 796, p. 203-209Article in journal (Refereed)
    Abstract [en]

    Magnetic nanoparticles represent complex but very interesting objects. They combine the bulk properties with novel phenomena emerging at the nanoscale due to finite-size effects. The recent development of the synthetic procedures allows having a strong control on the size and shape of individual particles and on their physical-chemical structure. Among different magnetic materials, spinel ferrite nanoparticles offer strong chemical and physical stability as well as tunable magnetic properties. In the present article, we investigate the effect of Zn substitution in cobalt ferrite nanoparticles. The technological development of nanoparticle-based magnetic materials aims to find a balance between a well-defined magnetic behavior of individual elements and their strong interactions, which arise from the need of miniaturization that leads to dense ensembles of the system's constituents. Within this complex context, we provide one route to optimize the properties of small spinel ferrite particles by tuning their chemical composition without compromise their structural properties, and with full control of their size and shape. Furthermore, we propose an advanced analysis of their magnetic properties in the framework of the random anisotropy model. We will show that the chemical composition not only determines the intrinsic anisotropy energy of each nanoparticle but also owns a profound effect on the interparticle interactions.

  • 46. Norén, L.
    et al.
    Larsson, A. -K
    Withers, R. L.
    Rundlöf, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, The Studsvik Neutron Research Laboratory.
    A neutron and X-ray powder diffraction study of B8(2) related superstructure phases in the Ni-In system2006In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 424, no 1-2, p. 247-254Article in journal (Refereed)
    Abstract [en]

    The crystal structures of two low temperature B8(2) related superstructure phases in the nickel indium system, Ni13In9 and Ni7-delta In3, have been refined and described in relation to the underlying parent Ni2In structure-type. They are isostructural to In13Pt9 and Cu7In3, respectively and both accommodate the change in stoichiometry from Ni2In by forming "same atom" structural motifs, In-centred indium octahedral units in the case of Ni13In9 and trigonal bipyramidal nickel units in the case of Ni7-delta In3. A sample with the nominal composition Ni51n3, reported to form part of a solid solution in the binary phase diagram, is not stable at 400 degrees C and forms a two-phase mix of Ni7-delta In3 and Ni13In9.

  • 47.
    Oleshkevych, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Zamani, Atieh
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Kotenko, Igor
    Voloshko, Svitlana
    Sidorenko, Sergey
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Thermally driven redistribution of phases and components in Cu/Sn thin films2012In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 535, p. 108-113Article in journal (Refereed)
    Abstract [en]

    Unusual features of phase transformations under the thermal treatment of the thin films system Cu (80 nm)-Sn (20 nm) have been studied using a range of physical methods. Processes of mass transfer in thin layers were studied and regimes of thermal treatment were chosen to compare the influence of different temperatures for a given time and the influence of annealing time at a fixed temperature. Presence of the intermetallic phase Cu6Sn5 in the as-deposited state and its transformation into Cu3Sn phase after annealing at temperature 373 K for different times has been identified by grazing incidence X-ray diffraction. Annealing at a temperature of 473 K, and higher, leads to the formation, unexpectedly, of the Cu4Sn phase. The concentration distribution of tin through the depth of the sample was obtained by Rutherford backscattering spectroscopy and demonstrated the existence of the Cu4Sn composition. The topography of the surface of the samples was determined with atomic-force microscopy.

  • 48.
    Oppeneer, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Shick, A. B.
    Rusz, Jan
    Lebegue, S.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Fermiology of PuCoGa5 and of related Pu-115 compounds2007In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 444, p. 109-113Article in journal (Refereed)
    Abstract [en]

    We report computational investigations of the electronic structures of the superconducting Pu-compounds PuCoGa5 as well as of the non-superconducting compounds PuFeGa5 and PuNiGa5. To capture the localization behavior of the Put 5f electrons, we apply two computational approaches, which are both rooted in the density-functional theory: the local spin-density approximation (LSDA) and the around mean field (AMF) LSDA + U approach. The latter is applicable to moderately localized 5f electrons while the former is applicable to delocalized 5f electrons. Our LSDA calculations show that the Fermi surfaces of the three Pu-115 compounds are sensitive to the amount of band filling, i.e., the number of electrons of the 3d element. Precisely at the electron filling corresponding to PuCoGa5 the Fermi surface has a particularly two-dimensional shape. AMF-LSDA+U calculations (with a Coulomb U of about 3 eV and exchange J of 0.6 eV) lead to a non-magnetic ground state for PuCoGa5, in which the 5f states are shifted to a higher binding energy, in better agreement with photoemission data. The Fermi surface of PuCoGa5 computed with the AMF-LSDA+U approach is nonetheless rather two-dimensional and similar to the LSDA Fermi surface. The AMFLSDA+U approach with a Coulomb U of approximate to 3 eV would thus predict an electronic structure for PuCoGa5 in accord with several experimental data.

  • 49.
    Pacheco, Victor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Marattukalam, Jithin J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Stolpe, Moritz
    Heraeus Addit Mfg GmbH, D-63450 Hanau, Germany.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Jansson, Ulf
    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.
    Thermal stability and crystallization of a Zr-based metallic glass produced by suction casting and selective laser melting2020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 825, article id 153995Article in journal (Refereed)
    Abstract [en]

    The thermal stability and crystallization mechanism of the Zr59.3Cu28.8Al10.4Nb1.5 (at%) metallic glass produced through selective laser melting SLM (from industrial grade material) was studied and compared with the same alloy produced by suction casting (from laboratory grade material of high purity). Oxygen- and Al-rich particles of a cubic phase (Fd (3) over barm) with a size of up to 200 nm are detected in the as-built selective laser melted samples by transmission electron microscopy. The crystallization process of the cast and SLM samples is investigated by in-situ X-ray diffraction experiments. In the cast samples, the initial crystallization occurs via the formation of a metastable tetragonal phase (Al2Zr3), together with tetragonal CuZr2 and hexagonal Al3Zr4 type structures, while the SLM samples initially crystallize through the formation of the metastable, oxygen- and Al-rich, cubic phase already present before annealing. The main phases present at the end of the crystallization for both type of samples are the same, mainly CuZr2 and Al3Zr4. The differences in the crystallization paths are attributed to differences in the oxygen levels. In general, the higher oxygen content (similar to 1 at%) of the SLM samples results in a decrease of the thermal stability of the alloy and promotes the formation of an oxygen-rich, metastable cubic phase. 

  • 50.
    Pandey, Nidhi
    et al.
    UGC DAE Consortium Sci Res, Univ Campus,Khandwa Rd, Indore 452001, Madhya Pradesh, India..
    Gupta, Mukul
    UGC DAE Consortium Sci Res, Univ Campus,Khandwa Rd, Indore 452001, Madhya Pradesh, India..
    Gupta, Rachana
    Inst Engn & Technol DAVV, Khandwa Rd, Indore 452017, Madhya Pradesh, India..
    Chakravarty, Sujay
    UGC DAE Consortium Sci Res, Kokilamedu 603104, Tamil Nadu, India..
    Shukla, Neeraj
    UGC DAE Consortium Sci Res, Kokilamedu 603104, Tamil Nadu, India..
    Devishvili, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Inst Laue Langevin, Rue Martyrs, F-38042 Grenoble, France.;Lund Univ, Dept Chem, Div Phys Chem, S-22100 Lund, Sweden..
    Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 694, p. 1209-1213Article in journal (Refereed)
    Abstract [en]

    In this work, we studied cobalt nitride (Co-N) thin films deposited using a dc magnetron sputtering method at a substrate temperature (T-s) of 523 K. We find that independent of the reactive gas flow (R-N2) used during sputtering, the phases of Co-N formed at this temperature seems to be identical having N at.% similar to 5. This is contrary to Co-N phases formed at lower T-s. For example at T-s similar to 300 K, an evolution of Co-N phases starting from Co(N) -> Co4N -> Co-3 N -> CoN can be seen as R-N2 increases gradually to 100%, whereas when T-s increases to 523 K, the phase formed is fcc Co along with a minuscule Co4N phase for R-N2 >= 25%. We used x-ray diffraction (XRD) to probe long range ordering, x-ray absorption spectroscopy (XAS) at Co absorption edge for the local structure, Magneto-optical Kerr effect (MOKE) and polarized neutron reflectivity (PNR) to measure the magnetization of samples. Quantification of N at.% was done using secondary ion mass spectroscopy (SIMS). Measurements suggest that the magnetic moment of Co N samples deposited at 523 K is slightly higher than the bulk Co moment and does not get affected with the R-N2 used for reactive sputtering. Our results provide an important insight about the phase formation of Co-N thin films which is discussed in this work.

12 1 - 50 of 74
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