Effect of bismuth addition on the electrical conductivity of gadolinium-doped ceria ceramics

The structure, thermal expansion and electrical conductivity of Ce0.8(Gd1−xBix)0.2O1.9 (x = 0.1–0.5), prepared by coprecipitation were investigated. Ce0.8(Gd1−xBix)0.2O1.9 ceramics was sintered in the range of 1350–1450 °C for 6 h; the bulk density of Ce0.8(Gd1−xBix)0.2O1.9 ceramics was over 95% of the theoretical density; the maximum electrical conductivity, σ800 °C = 0.078 S/cm with minimum activation energy, Ea = 0.638 eV was found for the Ce0.8(Gd0.5Bi0.5)0.2O1.90 ceramic. The gadolinium-doped ceria ceramics preparation by coprecipitation can reduce the sintering temperature by addition of bismuth. The thermal expansion coefficient of Ce0.8(Gd1−xBix)0.2O1.9 covers the range of 20.132–20.478 ppm/°C. The ceramic has a fracture toughness in the range of 1.28–2.60 MPa m1/2 for dense Ce0.8(Gd1−xBix)0.2O1.9 ceramics. The value of fracture toughness increased with Bi content. It indicated that the mechanical properties of gadolinium-doped ceria ceramics could be improved by addition of bismuth.