Redox Stability and Electrical Properties of the High‐Entropy (Pb_0.2Ca_0.2Ba_0.2Sr_0.2Mg_0.2)_0.7La_0.3WO_4.15 Oxide Ion Conductor

Donor‐doped Pb_1−xLa_xWO₄ (x ≤ 0.3) materials are well‐known for their high oxygen ionic conductivity. However, their poor phase and redox stabilities under a reducing atmosphere hinder their practical applications, such as electrolytes for solid oxide fuel cells. In this work, a high‐entropy (Pb_0.2Ca_0.2Ba_0.2Sr_0.2Mg_0.2)_0.7La_0.3WO_4.15 material is prepared through a traditional solid‐state reaction method, aimed to enhance the phase and redox stability of the material under reducing atmosphere. The results reveal that this material has high phase and structural stability in high oxygen partial pressure environments. However, it will still undergo phase decomposition, yielding impurity, and introducing strong electronic conduction, showing even lower redox stability and phase stability than the non‐high‐entropy counterpart Pb_0.7La_0.3WO_4.15. Thus, improving the phase and redox stabilities under reducing atmospheres of the PbWO₄‐based materials is still the main challenge in the future.