The effect of Bi₂O₃ on the electrical and mechanical properties of ZrO₂-Y₂O₃ ceramics

ZrO₂-Y₂O₃ ceramics with varying Bi₂O₃ content have been prepared and their microstructure, electrical conductivity and mechanical properties investigated. The sintering rate is strongly increased at low temperatures (1270 to 1420 K) due to the occurrence of a reactive phase the amount of which decreases during the sintering process. The main fluorite phase has an approximately constant composition at 0.85 ZrO₂-0.13 Y₂O₃-0.02 Bi₂O₃ while the amount of second phase depends on overall composition and sintering procedure. The electrical conductivity is also approximately constant but about a factor of five lower than in ZrO₂-Y₂O₃ ceramics. Typical strength and fracture toughness values are 160 MPa and 1.8 MPa m^1/2, respectively. However, the non-reproducibility of the second phase content and morphology seriously influences both mechanical properties.