Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
Link to record
Permanent link

Direct link
Shafeie, Samrand
Publications (9 of 9) Show all publications
Cedervall, J., Clulow, R., Boström, H., Joshi, D. C., Andersson, M., Mathieu, R., . . . Shafeie, S. (2021). Phase stability and structural transitions in compositionally complex LnMO(3) perovskites. Journal of Solid State Chemistry, 300, Article ID 122213.
Open this publication in new window or tab >>Phase stability and structural transitions in compositionally complex LnMO(3) perovskites
Show others...
2021 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 300, article id 122213Article in journal (Refereed) Published
Abstract [en]

Entropy stabilised materials have possibilities for tailoring functionalities to overcome challenges in materials science. The concept of configurational entropy can also be applied to metal oxides, but it is unclear whether these could be considered as solid solutions in the case of perovskite-structured oxides and if the configurational entropy plays a stabilising role. In this study, compositionally complex perovskite oxides, LnMO(3) (Ln = La, Nd, Sm, Ca and Sr, M = Ti, Cr, Mn, Fe, Co, Ni, and Cu), are investigated for their phase stability and magnetic behaviour. Phase-pure samples were synthesised, and the room temperature structures were found to crystallise in either Pnma or R (3) over barc space groups, depending on the composition and the resulting tolerance factor, while the structural transition temperatures correlate with the pseudo cubic unit cell volume. The techniques used included diffraction with X-rays and neutrons, both ex- and in-situ, X-ray photoelectron spectroscopy, magnetometry as well as electron microscopy. Neutron diffraction studies on one sample reveal that no oxygen vacancies are found in the structure and that the magnetic properties are ferrimagnetic-like with magnetic moments mainly coupled antiferromagnetically along the crystallographic c-direction. X-ray photoelectron spectroscopy gave indications of the oxidation states of the constituting ions where several mixed oxidation states are observed in these valence-compensated perovskites.

Place, publisher, year, edition, pages
ElsevierACADEMIC PRESS INC ELSEVIER SCIENCE, 2021
Keywords
Perovskites, Phase transitions, High entropy oxides, Magnetism
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-449243 (URN)10.1016/j.jssc.2021.122213 (DOI)000661134000018 ()
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research , EM-16-0039SweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Energy Agency
Available from: 2021-07-22 Created: 2021-07-22 Last updated: 2024-01-15Bibliographically approved
Ivanov, S., Beran, P., Bush, A. A., Sarkar, T., Shafeie, S., Wang, D., . . . Mathieu, R. (2019). Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)(2/3)W1/3O3 solid solutions. European Physical Journal B: Condensed Matter Physics, 92(8), Article ID 163.
Open this publication in new window or tab >>Cation ordering, ferrimagnetism and ferroelectric relaxor behavior in Pb(Fe1-xScx)(2/3)W1/3O3 solid solutions
Show others...
2019 (English)In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 92, no 8, article id 163Article in journal (Refereed) Published
Abstract [en]

Ceramic samples of the multiferroic perovskite Pb(Fe1-xScx)(2/3)W1/3O3 with 0 <= x <= 0.4 have been synthesized using a conventional solid-state reaction method, and investigated experimentally and theoretically using first-principle calculations. Rietveld analyses of joint synchrotron X-ray and neutron diffraction patterns show the formation of a pure crystalline phase with cubic (Fm3(_)m) structure with partial ordering in the B-sites. The replacement of Fe by Sc leads to the increase of the cation order between the B and B '' sites. As the non-magnetic Sc3+ ions replace the magnetic Fe3+ cations, the antiferromagnetic state of PbFe2/3W1/3O3 is turned into a ferrimagnetic state reflecting the different magnitude of the magnetic moments on the B ' and B '' sites. The materials remain ferroelectric relaxors with increasing Sc content. Results from experiments on annealed and quenched samples show that the cooling rate after high temperature annealing controls the degree of cationic order in Pb(Fe1-xScx)(2/3)W1/3O3 and possibly also in the undoped PbFe2/3W1/3O3.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Solid State and Materials
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-392576 (URN)10.1140/epjb/e2019-100149-9 (DOI)000477626500002 ()
Funder
Swedish Research Council
Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2022-01-10Bibliographically approved
Fang, H., Li, J., Shafeie, S., Hedlund, D., Cedervall, J., Ekström, F., . . . Sahlberg, M. (2019). Insights into phase transitions and magnetism of MnBi crystals synthesized from self-flux. Journal of Alloys and Compounds, 781, 308-314
Open this publication in new window or tab >>Insights into phase transitions and magnetism of MnBi crystals synthesized from self-flux
Show others...
2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 781, p. 308-314Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
In situ synchrotron radiation X-ray diffraction, Phase transitions, Rare earth free permanent magnet, MnBi, Single crystals
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-378612 (URN)10.1016/j.jallcom.2018.12.146 (DOI)000457845900034 ()
Funder
Swedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2023-10-31Bibliographically approved
Kontos, S., Fang, H., Li, J., Delczeg-Czirjak, E. K., Shafeie, S., Svedlindh, P., . . . Gunnarsson, K. (2019). Measured and calculated properties of B-doped τ-phase MnAl: A rare earth free permanent magnet. Journal of Magnetism and Magnetic Materials, 474, 591-598
Open this publication in new window or tab >>Measured and calculated properties of B-doped τ-phase MnAl: A rare earth free permanent magnet
Show others...
2019 (English)In: Journal of Magnetism and Magnetic Materials, Vol. 474, p. 591-598Article in journal (Refereed) Published
Abstract [en]

The metastable tetragonal τ-phase MnAl has been doped interstitially with B through a drop synthesis method creating the (Mn0.55Al0.45)B0.02 compound. The as-casted samples were annealed, quenched and thereafter ball-milled and relaxed in order to decrease grain size and reduce the number of crystallographic defects. The Curie temperature of the quenched sample was estimated to 655 K. The magnetization, coercivity and anisotropy were analyzed with respect to flash-milling time, relaxation time and temperature. The results show that (Mn0.55Al0.45)B0.02 could be directly obtained from drop synthesis. The highest measured saturation magnetization of 393 kA/m (measured at ±1440kA/m) was achieved with a relaxation process after 1.5h milling, giving a theoretical maximum energy product of 48 kJ/m3. The highest value of the coercivity was 355 kA/m achieved by flash-milling for 10 h. However, the high coercivity was achieved at an expense of low saturation magnetization.

Keywords
Permanent magnets; Rare-Earth-free; Diffraction; Magnetometry; Computational modeling
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-368265 (URN)10.1016/j.jmmm.2018.11.006 (DOI)000459494600086 ()
Funder
Swedish Energy AgencySweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-03-21Bibliographically approved
Shafeie, S., Fang, H., Hedlund, D., Nyberg, A., Svedlindh, P., Gunnarsson, K. & Sahlberg, M. (2019). One step towards MnAl-based permanent magnets: Differences in magnetic, and microstructural properties from an intermediate annealing step during synthesis. Journal of Solid State Chemistry, 274, 229-236
Open this publication in new window or tab >>One step towards MnAl-based permanent magnets: Differences in magnetic, and microstructural properties from an intermediate annealing step during synthesis
Show others...
2019 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 274, p. 229-236Article in journal (Refereed) Published
Abstract [en]

The influence of an additional annealing step during synthesis on the preparation of MnAl based permanent magnet alloys has been investigated. Bulk samples of Mn55Al45C2 alloys were synthesized using induction heating through drop synthesis from 1400 °C. Samples produced using cooling directly from 1400 °C (from the melt), and from 1400 °C to an intermediate annealing step at 1200 °C for ~ 30 min before cooling were compared with respect to differences in phase purity, microstructure and magnetic properties. We found that the phase purity was significantly enhanced using the route with an intermediate annealing step at 1200 °C. From XRD the phase purity of the tau-phase was improved from ~ 91 wt% for the sample cooled directly from 1400 °C to ~ 95.1 - 99.5 wt% for the sample exposed to an intermediate annealing step before cooling. Additionally, EBSD, and SEM with EDS indicates a clear difference in the phase composition and differences in the distribution of the magnetic tau phase and the non-magnetic epsilon-, beta-, and gamma-phases. Magnetic properties also indicate, an improvement in saturation magnetization for the sample exposed to the extra annealing step during synthesis. Our results suggest that an intermediate annealing step in the production of MnAl based alloys will provide a simple way of achieving better phase purity and magnetic properties in the bulk alloy.

Keywords
permanent magnet, rare earth free, microstructure
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-368283 (URN)10.1016/j.jssc.2019.03.035 (DOI)000467663700032 ()
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Foundation for Strategic Research
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2023-10-31Bibliographically approved
Sheikh, S., Bijaksana, M. K., Motallebzadeh, A., Shafeie, S., Lozinko, A., Gan, L., . . . Guo, S. (2018). Accelerated oxidation in ductile refractory high-entropy alloys. Intermetallics (Barking), 97, 58-66
Open this publication in new window or tab >>Accelerated oxidation in ductile refractory high-entropy alloys
Show others...
2018 (English)In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 97, p. 58-66Article in journal (Refereed) Published
Abstract [en]

Refractory high-entropy alloys (RHEAs) are promising candidates for new-generation high temperature materials, but they generally suffer from room temperature brittleness and unsatisfactory high-temperature oxidation resistance. There currently lack efforts to address to these two critical issues for RHEAs at the same time. In this work, the high temperature oxidation resistance of a previously identified ductile Hf0.5Nb0.5Ta0.5Ti1.5Zr RHEA is studied. An accelerated oxidation or more specifically, pesting, in the temperature range of 600-1000 degrees C is observed for the target RHEA, where the oxidation leads the material to catastrophically disintegrate into powders. The pesting mechanism is studied here, and is attributed to the failure in forming protective oxide scales accompanied by the accelerated internal oxidation. The simultaneous removal of zirconium and hafnium can eliminate the pesting phenomenon in the alloy. It is believed that pesting can also occur to other equiatomic and non-equiatomic quinary Hf-Nb-Ta-Ti-Zr or quaternary Hf-Nb-Ti-Zr and Hf-Ta-Ti-Zr RHEAs, where all currently available ductile RHEAs are identified. Therefore, the results from this work will provide crucial perspectives to the further development of RHEAs as novel high-temperature materials, with balanced room-temperature ductility and high-temperature oxidation resistance.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2018
Keywords
Refractory high-entropy alloys, Oxidation resistance, Pesting, High temperature materials
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-356614 (URN)10.1016/j.intermet.2018.04.001 (DOI)000433016500009 ()
Available from: 2018-08-20 Created: 2018-08-20 Last updated: 2018-08-20Bibliographically approved
Sheikh, S., Gan, L., Tsao, T.-K., Murakami, H., Shafeie, S. & Guo, S. (2018). Aluminizing for enhanced oxidation resistance of ductile refractory high-entropy alloys. Intermetallics (Barking), 103, 40-51
Open this publication in new window or tab >>Aluminizing for enhanced oxidation resistance of ductile refractory high-entropy alloys
Show others...
2018 (English)In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 103, p. 40-51Article in journal (Refereed) Published
Abstract [en]

Refractory high-entropy alloys (RHEAs) emerge as promising candidate materials for ultrahigh-temperature applications. One critical issue to solve for RHEAs is their balanced oxidation resistance and mechanical properties, mainly room-temperature ductility for the latter. Recently, it was found that existing ductile RHEAs are subject to catastrophic accelerated oxidation, also known as pesting. In this work, both alloying and surface coating, are applied to enhance the oxidation resistance of ductile RHEAs, with the focus on surface coating using the pack cementation method and more specifically, aluminizing. The oxidation resistance of two RHEAs, Hf0.5Nb0.5Ta0.5Ti1.5Zr, one recently identified ductile RHEA which pests in the temperature range of 600-1000 degrees C, and Al0.5Cr0.25Nb0.5Ta0.5Ti1.5, the newly designed ductile RHEA which does not pest but embrittles after oxidation, are studied after aluminizing at 900 degrees C using three different pack components. Aluminizing, if using the appropriate pack cementation parameters, can avoid pesting in Hf0.5Nb0.5Ta0.5Ti1.5Zr and alleviate the oxidation induced embrittlement in Al0.5Cr0.25Nb0.5Ta0.5Ti1.5, and holds the promise for further improving the RHEAs as potential ultrahigh-temperature materials.

Keywords
Refractory high-entropy alloys, Oxidation resistance, Aluminizing, Pack cementation, Coating
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-371037 (URN)10.1016/j.intermet.2018.10.004 (DOI)000450380700005 ()
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-01-08Bibliographically approved
Fang, H., Cedervall, J., Hedlund, D., Shafeie, S., Deledda, S., Olsson, F., . . . Sahlberg, M. (2018). Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl. Scientific Reports, 8(1), Article ID 2525.
Open this publication in new window or tab >>Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl
Show others...
2018 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, no 1, article id 2525Article in journal (Refereed) Published
Abstract [en]

The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fne powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a fash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the fash heated samples display high saturation magnetization as well as increased coercivity.

National Category
Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-341024 (URN)10.1038/s41598-018-20606-8 (DOI)000424189500012 ()29410462 (PubMedID)
Funder
Swedish Energy AgencySweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Research Council
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2022-09-15Bibliographically approved
Koroleva, A. F., Bush, A. A., Kamentsev, K. E., Shkuratov, V. Y., Ivanov, S., Cherepanov, V. M. & Shafeie, S. (2018). Synthesis, X-ray Diffraction Characterization, Mössbauer Spectroscopy, and Dielectric Properties of Solid Solutions in the PbFe2/3W1/3O3–PbSc2/3W1/3O3 System. Inorganic Materials (Neorganicheskie materialy), 54(3), 288-294
Open this publication in new window or tab >>Synthesis, X-ray Diffraction Characterization, Mössbauer Spectroscopy, and Dielectric Properties of Solid Solutions in the PbFe2/3W1/3O3–PbSc2/3W1/3O3 System
Show others...
2018 (English)In: Inorganic Materials (Neorganicheskie materialy), ISSN 0020-1685, E-ISSN 1608-3172, Vol. 54, no 3, p. 288-294Article in journal (Refereed) Published
Abstract [en]

Ceramic Pb(Fe1–xSc x )2/3W1/3O3 samples with 0 ≤ x ≤ 1 have been prepared and characterized by X-ray diffraction, Mössbauer spectroscopy, and dielectric and pyroelectric measurements. The stoichiometry ranges of the perovskite solid solutions in this system have been identified, their structural parameters have been determined, and their dielectric permittivity, dielectric loss tangent, resistivity, and thermally stimulated depolarization current have been measured as functions of temperature. The composition dependences of the dielectric properties for the solid solutions have been obtained. The solid solutions have been shown to exhibit ferroelectric relaxor properties, with a well-defined maximum in their permittivity in the range 180–250 K.

Keywords
ferroelectric ceramics, magnetoelectric materials, solid solutions, perovskite structure, dielectric properties, Mossbauer spectroscopy, X-ray powder diffraction
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-351096 (URN)10.1134/S0020168518030056 (DOI)000427490400013 ()
Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-06-05Bibliographically approved
Organisations

Search in DiVA

Show all publications