Investigation of the chemical versatility in high‐entropy pyrochlores

Abstract

Abstract This article reports on the exploration of the chemical versatility of entropy‐stabilized pyrochlores (A 2 B 2 O 7 ) with large chemical disorder introduced on the B site, as well as the study of isovalent and aliovalent substitution on the B site and of Ca 2+ ‐doping on the A site. Among all the 20 new compounds obtained in this study, 8 are entropy‐stabilized: RE 2 (TiZrHfGeSn) 2 (with RE = Gd–Ho and Y), Pr 2 (TiZrHfScNb) 2 O 7 , and RE 2 (TiGeSnAlNb) 2 O 7 (with RE = Er and Y). Moreover, some physical properties (magnetic, electrical, thermal, and optical properties) of these high‐entropy pyrochlores have been screened, and some of them could be potentially interesting for applications. For example, we observed low thermal diffusivity values (between 0.4 and 0.7 m 2 s −1 ) making them interesting for thermal barrier coating or tunable optical bandgaps in the visible region that could make them appealing as photocatalysts or in optical applications. Furthermore, single‐phased compounds were obtained for almost all the rare earths (REs) on the A site. Therefore, when five nonmagnetic cations are used for the B site, it enables to study the magnetic properties and, more specifically, the influence of the local chemical and structural disorder on the exotic ground states observed in monocationic RE pyrochlores.