Effect of CaO addition on the structure and electrical conductivity of the pyrochlore-type GdSmZr ₂O ₇

Polycrystalline GdSm _1-xCa _xZr ₂O _7-x/2 (0 ≤ x ≤ 0.20) ceramics have been prepared by the solid-state reaction method. The effects of CaO addition on the microstructure and electrical properties of the pyrochlore-type GdSmZr ₂O ₇ ceramic were investigated. GdSm _1-xCa _xZr ₂O _7-x/2 (x ≤ 0.05) ceramics exhibit a pyrochlore-type structure; however, GdSm _1-xCa _xZr ₂O _7-x/2 (0.10 ≤ x ≤ 0.20) ceramics consist of the pyrochlore-type structure and a small amount of CaZrO ₃. The total conductivity of GdSm _1-xCa _xZr ₂O _7-x/2 ceramics follows the Arrhenius relation, and gradually increases with increasing temperature from 723 to 1173 K. GdSm _1-xCa _xZr ₂O _7-x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10 ^-4-1.0 atm at each test temperature. The highest total conductivity is about 1.20 × 10 ^-2 S cm ^-1 at 1173 K for the GdSm _0.9Ca _0.1Zr ₂O _6.95 ceramic.