ELECTRICAL RESISTANCES AND DEFORMATION OF YTTRIA-STABILIZED CUBIC ZIRCONIA WITH ALUMINA

The effect of addition of alumina to cubic zirconia was investigated in order to explore the possibility of plastic deformation in cubic phase materials and to examine its influence on the electrical conductivity. Zirconia powders with additives of 5.5 mol% yttria and 1, 5, 10 and 20 wt% alumina were made by coprecipitation. Without alumina the grain size increased to about 2 mum after sintering at 1450-degrees-C, but only to 0.5 mum for the material with 5 wt% alumina additives. The latter showed a large deformation in spite of the presence of the cubic phase. The frequency dispersion measurements of cubic zirconia with 5.5 mol% Y2O3 added together with additives of 0, 3, 5, 7 and 10 wt% alumina were analyzed using the brick layer model. Two overlapping arcs in cubic zirconia with 5 wt% alumina were observed in the impedance results obtained at 400-degrees-C. The arc on the high-frequency side is referred to as the bulk resistance. The other one is related to the grain boundaries. The size of this second arc is dependent on the alumina content. The diameter is large for samples containing no alumina. With increasing alumina content, the size of this arc passes through a minimum at 5 wt% and increases slightly with increasing alumina content.