It was noted that fluorite-type O-ion conducting solid solutions of the form, (Bi0.95Nb0.05)0.85Ho0.15O1.5+d and (Bi1-xZrx)0.85Y0.15O1.5+d (with x = 0.05 or 0.07), partially decomposed at temperatures below 900K. This led to the formation of several phases which were isostructural with δ- and γ-Bi2O3. The formation of the body-centered cubic γ-type phase at 770K led to a sharp decrease in the conductivity; from about 0.1 to 0.001S/cm within 200h. Interaction of the Bi2O3-based solid electrolytes, with Ag electrodes, was observed at temperatures above 850K. This resulted in an increasing resistance of the electrochemical cells. Electrodes of Pt and perovskite-type La0.7Sr0.3CoO3 exhibited sufficient stability when placed in contact with the Bi2O3-based electrolytes at 870 to 1000K.

Stability of δ-Bi2O3-Based Solid Electrolytes. A.A.Yaremchenko, V.V.Kharton, E.N.Naumovich, A.A.Tonoyan: Materials Research Bulletin, 2000, 35[4], 515-20