Abstract
Entropy-stabilized oxide systems with four and five cations have been synthesized by the thermal decomposition of a metal–nitrate–citrate complex at 800-925 °C. A five-component oxide (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O is found to exhibit a reversible transformation between a multi-phase and single-phase state at elevated temperatures. Experimental results show that the cations in the single-phase state with a rocksalt structure are distributed homogeneously. The phase transformation temperature is reduced for the powders synthesized by a wet chemical reaction route. Similar results are also observed in the four-component oxide (Mg0.25Ni0.25Cu0.25Zn0.25)O. Effects of chemical compositions and phase formation on physical properties of the above entropy-stabilized oxide systems are investigated.