Phases, Electrical Properties, and Stability of High-Entropy Pyrochlores [(La0.25Nd0.25Sm0.25Eu0.25)1-xCax]2Zr2O7-δ Oxides

Series of Ca2+ ion-doped high-entropy [(La0.25Nd0.25Sm0.25Eu0.25)(1-x)Ca-x](2)Zr2O7-delta (x = 0.025, 0.05, 0.075, 0.1, and 0.2) materials are prepared through a traditional solid-state reaction method. The solubility of Ca is revealed to be x = 0.075, which is higher than that in the cases with single lanthanide on the A-site of A(2)Zr(2)O(7)-based pyrochlore materials. The study of electrical properties discloses that the conductivities of [(La0.25Nd0.25Sm0.25Eu0.25)(1-x)Ca-x](2)Zr2O7-delta increased with Ca-doping level and dominated by oxide ion conduction, without noticeable proton conduction. Good chemical stability is revealed for these materials under a wet CO2 atmosphere.