North-Holland Publishing Company EFFECT OF GRAIN BOUNDARIES ON THE CONDUCTIVITY OF HIGH-PURITY ZrO2-Y203 CERAMICS

Grain boundary conductivities are determined by complex impedance measurements (1-106 Hz) on high-purity ceram-ics prepared by the alkoxide synthesis and on less pure ceramics obtained from a commercial powder. The grain size wa varied systematically in the region 0.36-55 tam. The grain boundary conductivity is strongly influenced by the gsain size, impurities and cooling procedure. The grain boundary conductivity increases linearly with th grain sizefor small grain sizes (0.3 to 2-4 tam) and is constant for larger grain sizes The calculated specific conductivity of the grain boundary for pure materials is about 100 times smaller than that of the bulk. The grain boundary thickness was estimated to be 5.4 rim. The activation energy of the grain boundary conductivity is 7 kJ mole-1 higher than that of the bulk. 1