Capacitance and microstructure of platinum/yttria-stabilised zirconia composites

The influence of microstructure on the capacitive behavior in the dual-phase composite system platinum/cubic-yttria-stabilized zirconia (YSZ) was studied at ambient temperature. Three different synthesis methods were employed. The volume fraction of Pt metal in the composite was varied between 0 and 25 vol%. The resulting composites were characterized by scanning electron microscopy (SEM) and electrical impedance spectroscopy (EIS). The bulk capacity increased with Pt content. Depending on the synthesis method, differences in microstructural homogeneity were observed by SEM. However, for samples prepared via different routes and with similar volume fractions of metallic Pt, no significant differences in capacity were observed. A maximum increase in the capacity of approximately 12.6 compared to pure cubic yttria-stabilized zirconia was obtained for a composite containing 25 vol% platinum, prepared via the sol-gel method. The percolation threshold for the platinum phase was estimated from a fit of the experimental data to normalized percolation theory and was found to be 31.1 ± 1.5 vol%.