Relationship between strength and failure mode of ceramic multilayers

The mechanical strength of ceramic multilayers for use in solid oxide fuel cell stacks was examined. The multilayers consist of a substrate, made of yttria stabilised zirconia (YSZ), with a NiO/YSZ composite coating on both faces. Under some processing conditions the mechanical strength of the multilayers was similar to that of pure YSZ, while a much lower strength was found for other processing conditions.

Inspections of the fracture surfaces revealed markedly different appearances, suggesting that a transition in failure mode had occurred. Fracture mechanics models for thin films on substrates were used to interpret the observed fracture modes, providing insight to the underlying failure mechanisms.