Sputter deposition of yttria-stabilized zirconia and silver cermet electrodes for SOFC applications

Abstract

Yttria-stabilized zirconia (YSZ) thin films were deposited by reactive magnetron sputter deposition from a composite Zr-Y target in Ar-O 2 mixtures. YSZ deposition rates of 2.7 μm 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 stres. 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 15nm. Fully dense films were obtained at a deposition temperature of 350°C. Temperature-dependent impedance spectroscopy analysis of YSZ films with silver electrodes showed that the oxygen-ion conductivity was as expected for YSZ. Ag 1- x [(Y 2O 3) 0.1(ZrO 2) 0.9] x cermet thin films havew been deposited by reactive magnetron co-sputtering silver and Zr/Y targets in Ar-O 2 mixtures. The resistivity ϱ of as-deposited and annealed films as a function od silver volume fraction ⨍ Ag varied over several orders of magnitude. Evaporation of silver from cermet films. observed during long-term annealing at 750°C, was eliminated by depositing a 1 μm thick Sr-doped LaCoO 3 cap layer on the cermet. The cermet with ⨍ Ag≈0.5 is a promising air electrode material for solid oxide devices operating at temperatures <-705°C, exhibiting both low resistivity ( 1×10 -4Ω cm ) and high thermal stability.