Electrical Conductivity in the ZrO 2 ‐Rich Region of Several M 2 O 3 —ZrO 2 Systems

The electrical conductivity of M 2 O 3 ‐ZrO 2 compositions containing 6 to 24 mole % M 2 O 3 , where M represents La, Sm, Y, Yb, or Sc, was examined. Only Sm 2 O 3 , Y 2 O 3 , and Yb 2 O 3 formed cubic solid solutions with ZrO 2 over most of this substitutional range. Scandia forms a wide cubic solid solution region with ZrO 2 at temperatures above 130°C whereas the cubic solid solution region at room temperature is narrow (6 to 8 mole % Sc 2 O 3 ). Lanthana additions to ZrO 2 produced no fluorite‐type cubic solid solutions within the compositional range investigated. Generally, the electrical conductivity of these cubic solid solutions increased as the size of the substituted cation decreased and the electrical conductivity for each binary system attained a maximum at about 10 to 12 mole % M 2 O 3 .