Preparation and properties of new oxygen ion conductors for use at low temperatures

Two new systems, Bi₂O₃Er₂O₃ and ZrO₂Y₂O₃(CaO)Bi₂O₃ were investigated. The first system has a homogeneous cubic, fluorite phase between 17.5 and 45.5 mol % Er₂O₃ and can be sintered to densities near 95% at 1200 K. At temperatures between 700 K and 1000 K the highest value of the a.c. oxygen ion conduction in this system is twice as much as the highest value found in the literature. In the second system concentrations of 1–3 mol % Bi₂O₃ act as an excellent sintering aid for ZrO₂Y₂O₃ and ZrO₂CaO samples which can be sintered to densities higher than 95% at temperatures of 1350 K. During this procedure a liquid ZrO₂Bi₂O₃ phase exists from which Bi₂O₃ partly evaporates with increasing sintering time. The oxygen ion conduction is little affected by the Bi₂O₃-rich second phase. The influence of annealing procedures up to 1570 K on the conduction in the ZrO₂Y₂O₃Bi₂O₃ system is small despite weight losses up to 4%.