Quantitative analysis of microstructural homogeneity and capacitance correlations in palladium/yttria-stabilized zirconia composites

Voronoi tessellation was applied to quantify the microstruetural homogeneity of palladium particles in random Pd/cubic yttria-stabilized zirconia (YSZ) composites with the I'd concentration ranging from 0 to 30 vol%. Room-temperature impedance measurements were used to determine the capacitance of the composites. A fourfold enhancement in capacity near the percolation threshold of I'd was obtained. The percolation threshold was estimated at similar to30 vol% Pd using the normalized percolation theory (NPT). Data obtained from Voronoi diagrams resulted in a quantitative measure for the homogeneity of the dual-phase composite. The homogeneity was found to decrease with increasing I'd concentration in the composites. Near the theoretical value of the percolation threshold, the I'd phase appeared to be distributed too inhomogeneously for preparing insulating composites. No large increase in capacity as predicted by NPT could therefore be experimentally verified.