Ionic Conductivity of Cubic Solid Solutions in the System CaO—Y2O3—ZrO2

The ionic conductivity of cubic solid solutions in the system CaO -Y₂O₃-ZrO₂ was examined. Particular Y₂O₃-ZrO₂ binary compositions were more conductive at elevated temperatures (>600°C) than either CaO-ZrO₂ binary or CaO-Y₂O₃-ZrO₂ ternary compositions. The higher ionic conductivity appears to be related to a lower activation energy rather than to the number of oxygen vacancies dictated by composition. Those compositions of highest conductivity lie close to the cubic-monoclinic solid-solution phase boundary. Conductivity-temperature data are presented that indicate a reversible order-disorder transition for Y₂O₃-ZrO₂ cubic solid solutions containing 20 and 25 mole % Y₂O₃. The transference number for the oxygen ion at 1000°C for Y₂O₂-ZrO₂ cubic solid solutions is greater than 0.99.