Mechanochemical Synthesis of (Co,Cu,Mg,Ni,Zn)O High-Entropy Oxide and Its Physicochemical Properties
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The study describes the physicochemical properties of transition metal (Co,Cu,Mg,Ni,Zn)O high-entropy oxide prepared using mechanochemical synthesis (MS) followed by thermal treatment, as well as the structural evolutions in the powder with milling time. The microstructure and electrical properties of the materials were studied using x-ray diffraction, scanning electron microscopy—energy dispersive spectroscopy and electrochemical impedance spectroscopy. The powders obtained after 30 h and 100 h of MS contained a mixture of two phases with a rock salt structure and, in addition, about 11 wt.% of Co3O4. Sintering these materials for 10 h in air at 1273 K led to the formation of a single-phase, solid solution with a rock salt structure. The developed sinters exhibited a fine-crystalline structure of grains and a uniform distribution of elements. The highest electrical conductivity was measured at 1148 K, and it was equal to 8.03 × 10−2 S cm−1.
KeywordsMilling electrical conductivity transition metal oxides high-entropy oxides
This work was performed as part of the statutory activities of the Department of Physical Chemistry and Modeling, Faculty of Materials Science and Ceramics, AGH University of Science and Technology (Contract No. 11.11.160. 768) and the Institute of Materials Science and Engineering, Faculty of Mechanical Engineering and Management, Poznan University of Technology (No. 02/24/DSPB/4657). The authors would also like to thank Professor Konrad Świerczek from the AGH-UST Faculty of Energy and Fuels for performing high-temperature XRD studies as well as Professor Mitsutoshi Ueda from the Tokyo Institute of Technology for the SEM–EDS analysis he performed.
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Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.