Ionic Conductivity of Cubic Solid Solutions in the System CaO—Y ₂ O ₃ —ZrO ₂

Abstract

The ionic conductivity of cubic solid solutions in the system CaO ‐Y 2 O 3 ‐ZrO 2 was examined. Particular Y 2 O 3 ‐ZrO 2 binary compositions were more conductive at elevated temperatures (>600°C) than either CaO‐ZrO 2 binary or CaO‐Y 2 O 3 ‐ZrO 2 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 Y 2 O 3 ‐ZrO 2 cubic solid solutions containing 20 and 25 mole % Y 2 O 3 . The transference number for the oxygen ion at 1000°C for Y 2 O 2 ‐ZrO 2 cubic solid solutions is greater than 0.99.