Sputtered YSZ based protective thin films for SOFCs

Abstract

Protective Zr(Y)O2–δ based films, deposited using magnetron sputtering, onto apatite type ceramics, were appraised for potential applications in solid oxide fuel cells with silicate based solid electrolytes, where performance may suffer from surface decomposition processes in reducing atmospheres. While as prepared Zr(Y)O2–δ films without copper additive were already crystallised and single phase, fresh Cu containing Zr(Y)O2–δ are essentially amorphous, requiring high temperature treatment in air for crystallisation. Deposition rate of 0·50–0·75 μm h–1 at sputtering power of 300 W was achieved. Surface morphology studies using atomic force microscope revealed typical film structures with small (<50 nm) grains. The hardness of films decreases from 15·8 to 8·4 GPa with increasing copper content. Polarisation studies of electrochemical cell with cermet anodes, applied over protective films, suggested that electrochemical reaction is essentially governed by oxygen anion transfer from zirconia phase and/or hydrogen oxidation in vicinity of zirconia film surface. Copper incorporation into Zr(Y)O2–δ film leads to higher anode resistivity.