THE EFFECT OF BI2O3 ON THE MICROSTRUCTURE AND ELECTRICAL-CONDUCTIVITY OF ZRO2-Y2O3 CERAMICS

ZrO2-Y2O3 ceramics with varying Bi2O3 contents were prepared and their microstructures and electrical conductivities investigated. The phase stability of cubic fluorite zirconia was disturbed by the introduction of Bi2O3 and tetragonal or monoclinic second phases appeared. The effect of the second phases on the intragrain and the grain boundary conductivities was investigated in the 300-550-degrees-C range using complex plane analysis in the frequency range of 5 Hz to 13 MHz. It showed that conductivity data could readily be interpreted in terms of possible physical models and electrical equivalent circuits. Tetragonal phases had a small positive influence on the intragrain conductivity. The grain 9boundary resistivity could be diminished by discrete monoclinic second phases which offered more conductive intergranular contacts.