Understanding the role of Cu into the reactivity and stabilization of the prototype High Entropy Oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O

We propose to study reactivity and stabilization of the high entropy oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O, by applying high instrumental and spatial resolution XRD to diffusion couples (DCs). Since Cu is deemed to be the destabilizing element in this system, we focus on the reaction between CuO and the quaternary oxide (Mg,Co,Ni,Zn)O. A SEM analysis showed the formation of a product layer (Cu2MgO3-like) and a defective, less crystalline, diffusion layer. A high resolution XRD test proved to be effective in monitoring the structure (phases, distortion, cell parameter) across the interface, while producing the same compositions in powder form led to inconclusive results. As we observed from SEM a different distribution of elements, and even phases, ranging from short (up to 30 minutes) to long reaction times, we propose to investigate insitu the reaction of the DC at 1000°C. In comparison, we plan to investigate the DCs obtained by interrupting the reaction after a selected duration.