High Entropy Oxides

Stable solid-solution phases consisting of five or more primary elements can be achieved due the high entropy of mixing stabilizing the structure, overcoming enthalpy minimization driven segregation. This has initially been realized in high entropy alloys (HEA), which exhibit unique mechanical properties superior to the traditional alloys. Research work on high entropy materials has been extended to oxide systems with rock salt MO, spinel M3O4 or perovskite ABO3 structures where ‘M’, ‘A’ and ‘B’ represent five or more nearly equiatomic metal cations. The high configurational entropy can effectively stabilize single phases of such complex multicomponent oxide systems, giving rise to new functional properties. Recently, the concept was extended to multi anionic high entropy materials such as LiMOF, which could be synthesized successfully. The atomic and electronic structure of HEAs and HEOs is of great interest and depends on the choice of substitutional elements. The geometric structure and electronic state of the cations will in turn determine the mechanical, electric and magnetic properties of the materials. We are investigating the atomic and electronic structure of entropy-stabilized materials with state-of-the-art transmission electron microscopy.