The structural and conductivity evolution of fluorite-type Bi2O3–Er2O3–PbO solid electrolytes during long-term annealing

Quenched-in fcc fluorite-type materials in the Bi2O3–Er2O3–PbO system were annealed in air at 500 and 600 °C for up to 2000 h. Each material experienced a conductivity-lowering structural transformation, thus making them unsuitable for use in SOFCs. For example, the materials (BiO1.5)0.80(ErO1.5)0.20−x(PbO)x, x = 0.03, 0.06 and 0.09, underwent a fluorite-type to tetragonal transformation during annealing at 500 °C due to 〈100〉 oxide-ion vacancy ordering, and the rate of conductivity decay at 500 °C increased with increasing Pb2+/Er3+ ratio.