Liquid-Phase Oxidation Joining of Yttria-Stabilized Zirconia via Al/Fe-Cr Alloy/Al Interlayers

Abstract

Liquid-phase oxidation (LPO) joining technique was employed to join yttria-stabilized zirconia (YSZ) blocks using Al/Fe-Cr alloy /Al interlayer for development of a gas sealing technique for solid oxide fuel cells (SOFCs). The YSZ blocks were joined at 1073 to 1473 K for 3.6 to 28.8 ks in vacuum (< 0.2 Pa) with a stress of 80 MPa and annealed at 973 K for 3.6 ks in air. The average four-point bend strength and Weibull modulus of LPO-joined YSZ specimen increased with increasing joining time at 1273 K. The specimen joined at 1273 K for 28.8 ks has a four-point bend strength of 135 MPa, which was about four times greater than that obtained by brazing technique using Ag solder, and comparable to unbonded monolithic YSZ. Polycrystalline alumina layer, which is expected to act as an insulating and protective layer, was formed between YSZ and Fe-Cr alloy after the LPO joining.