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

Series of Ca 2+ ion‐doped high‐entropy [(La 0.25 Nd 0.25 Sm 0.25 Eu 0.25 ) 1− x Ca x ] 2 Zr 2 O 7− δ ( 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 [(La 0.25 Nd 0.25 Sm 0.25 Eu 0.25 ) 1− x Ca x ] 2 Zr 2 O 7− δ 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 CO 2 atmosphere.