Capacitance at ambient temperature and microstructure of platinum/yttria-stabilized zirconia composites

The influence of microstructure on the capacitive behavior in the dual-phas e composite system platinum/cubic-yttria-stabilized zirconia (YSZ) was stud ied 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 capa city increased with Pt content. Depending on the synthesis method, differen ces in microstructural homogeneity were observed by C, SEM. However, for sa mples prepared via different routes and with similar volume fractions of me tallic Pt, no significant differences in capacity were observed. A maximum increase in the capacity of approximately 12.6 compared to pure cubic yttri a-stabilized zirconia was obtained for a composite containing 25 vol% plati num, prepared via the sol-gel method. The percolation threshold for the pla tinum phase was estimated from a fit of the experimental data to normalized percolation theory and was found to be 31.1 +/- 1.5 vol%. (C) 2001 Elsevie r Science Ltd. All rights reserved.