Formation and properties of high entropy oxides in Co-Cr-Fe-Mg-Mn-Ni-O system: Novel (Cr,Fe,Mg,Mn,Ni)3O4 and (Co,Cr,Fe,Mg,Mn)3O4 high entropy spinels |
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| Affiliation: | 1. School of Physics and Materials Science, Thapar Institute of Engineering and Technology, Patiala 147004, India;2. ISIS facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Oxfordshire OX11 0QX, United Kingdom;3. Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, P.O. Box 1033, N-0315 Oslo, Norway;4. Laboratory Crismat, UMR6508 CNRS, Normandie University, ENSICAEN, UNICAEN, 6 bd Maréchal Juin, 14050 Caen cedex 4, France;1. KIT-TUD-Joint Research Laboratory Nanomaterials, Technical University Darmstadt, Darmstadt 64287, Germany;2. Institute of Nanotechnology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen 76344, Germany;3. Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Lotharstr. 1, Duisburg 47057, Germany;4. Nano Functional Material Technology Centre (NFMTC), Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600036, India;5. Inorganic Chemistry and Catalysis, Utrecht University, Universiteitsweg 99, CG Utrecht 3584, The Netherlands;6. Institute for Materials Science, University of Stuttgart, Heisenbergstr. 3 Stuttgart 70569, Germany;1. Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany;2. KIT-TUD Joint Research Laboratory Nanomaterials, Institute of Materials Science, Technical University Darmstadt, 64287 Darmstadt, Germany;3. Nano Functional Materials Technology Centre, Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, 600036 Chennai, India;4. Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany |
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| Abstract: | Possibility of formation of quinary and senary equimolar high entropy oxides from the Co-Cr-Fe-Mg-Mn-Ni-O system is presented. Different proposed compositions are synthesized using the solid-state reaction route at high temperatures (900?1100 °C) and quenched to room temperature. Phase composition of the samples is studied, showing tendency toward formation of two main phases: rock salt-structured Fm-3 m and spinel-structured Fd-3 m. It is documented that the annealing temperature has a profound effect on stability of both structures, and at 1100 °C usually the highest content of Fm-3 m phase is usually observed. Three different oxides, namely, (Co,Cr,Fe,Mn,Ni)3O4, (Co,Cr,Fe,Mg,Mn)3O4 and (Cr,Fe,Mg,Mn,Ni)3O4 are obtained as single-phase materials, which structure can be described as the high entropy Fd-3 m spinel one. The latter two compounds have not been previously reported in the literature. Activated character of the electrical conductivity dependence on temperature is observed, with relatively high total conductivity at high temperatures and corresponding high absolute values of Seebeck coefficient. |
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| Keywords: | High entropy oxides Spinel phase Rock salt phase Microstructure Transport properties |
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