Quenched-in fcc fluorite-type materials in the Bi2O3–Er2O3–PbO system were annealed in air at 500 and 600C for up to 2000h. Each material experienced a conductivity-lowering structural transformation. 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 500C due to <100> oxide-ion vacancy ordering, and the rate of conductivity decay at 500C increased with increasing Pb2+/Er3+ ratio.

The Structural and Conductivity Evolution of Fluorite-Type Bi2O3–Er2O3–PbO Solid Electrolytes during Long-Term Annealing. N.A.S.Webster, C.D.Ling, C.L.Raston, F.J.Lincoln: Solid State Ionics, 2008, 179[19-20], 697-705