Reaction Pathway in The Formation of Rocksalt Entropy-Stabilized Oxides

High entropy oxides (HEO) are characterized through the effects of configurational disorder. The wide combinatorial space offered by complex materials, however, challenges our ability to predict reaction dynamics leading to entropy stabilization. We investigate (MgCoNiCuZn)O and establish the importance of kinetics in single phase formation. Rapid movement and diffusion between 800 °C and 870 °C indicate a eutectic copper oxide transition phase mediates the formation of the entropy-stabilized complex by solvating and localizing metal cations. Larger, constituent particles remain inactive until 1020 °C, where it then dissolves the liquid phase to form an entropy stabilized oxide. Modifying the composition and phase of the binary mixture, we find that the liquid copper phase is essential to the development of a single phase. We propose the possibility that engineered, selective melting may be utilized to realize and design other ESO and oxide phases.