SPUTTER DEPOSITION OF YTTRIA-STABILIZED ZIRCONIA AND SILVER CERMET ELECTRODES FOR SOFC APPLICATIONS

Yttria-stabilized zirconia (YSZ) thin films were deposited by reactive magnetron sputter deposition from a composite Zr-Y target in Ar-O2 mixtures. YSZ deposition rates of 2.7-mu-m h-1 were obtained at a sputter source power of 150 W. Deposition with total pressures from 3 to 20 mTorr yielded continuous, crack-free films in a compressive state of stress. X-ray diffraction and electron microscopy results showed that the films were polycrystalline cubic YSZ with a columnar structure and an average grain diameter of 15 nm. Fully dense films were obtained at a deposition temperature of 350-degrees-C. Temperature-dependent impedance spectroscopy analysis of YSZ films with silver electrodes showed that the oxygen-ion conductivity was as expected for YSZ. Ag1-x[(Y2O3)0.1(ZrO2)0.9]x cermet thin films have been deposited by reactive magnetron co-sputtering from silver and Zr/Y targets in Ar-O2 mixtures. The resistivity-rho of as-deposited and annealed films as a function of silver volume fraction f(Ag) varied over several orders of magnitude. Evaporation of silver from cermet films, observed during long-term annealing at 750-degrees-C, was eliminated by depositing a 1-mu-m thick Sr-doped LaCoO3 cap layer on the cermet. The cermet with f(Ag) almost-equal-to 0.5 is a promising air electrode material for solid oxide devices operating at temperatures less-than-or-equal-to 705-degrees-C, exhibiting both low resistivity (1 x 10(-4)OMEGA-cm) and high thermal stability.