DEPOSITION, STRUCTURE, AND PROPERTIES OF CERMET THIN-FILMS COMPOSED OF AG AND Y-STABILIZED ZIRCONIA

Ag1-x[(Y2O3)0.1(ZrO2)0.9]x (YSZ) cermet thin films have been deposited by reactive magnetron cosputtering from Ag and Zr/Y targets in Ar-O2 mixtures. The deposition conditions were such that the YSZ component in the films was fully oxidized. The film densities varied from almost-equal-to 75% to > 85% as the total pressure was decreased from 20 to 5 mTorr. Film resistivities rho varied with Ag volume fraction f(Ag) from 5 x 10(-6) OMEGA-cm to > 10(9) OMEGA-cm. For f(Ag) < 0.4, rho decreased rapidly with increasing f(Ag). For f(Ag) > 0.4, rho decreased more gradually with increasing f(Ag). rho in annealed films ranged from 4 x 10(-4) OMEGA-cm for f(Ag) = 0.4 to 5 x 10(-6) OMEGA-cm for pure Ag. Long term (> 100 h) annealing at greater-than-or-equal-to 700-degrees-C resulted in a gradual increase in cermet resistivity due to Ag evaporation and Ag segregation to surface islands. Both decomposition mechanisms were effectively suppressed at up to 750-degrees-C by depositing a 1-mu-m thick porous perovskite cap layer on the cermet. Complex impedance spectroscopy measurements in air of cermet electrodes on YSZ electrolytes gave interfacial resistances that were a factor of almost-equal-to 6 lower than those of pure Ag electrodes, e.g., 1.4 OMEGA-cm2 at 750-degrees-C. Ag-YSZ cermets thus have potential as high-conductivity, low-overpotential air electrode materials for solid-oxide electrochemical devices operating at temperatures less-than-or-equal-to 750-degrees-C.