High-Resolution Studies of Grain Boundary Structure in Yttria-Stabilized Cubic Zirconia Thin Films Grown by MOCVD

Abstract

Polycrystalline cubic-phase YSZ films with a colummar grain morphology were sunthesized by MOCVD. Under suitable growth and annealing conditions highly (001) textured films were obtained and used for investigations of [001] tilt grain boundaries (GBs) by TEM, AEM and HREM. Individual primary GB dislocations in low-angle GBs were imaged by Fresnel contrast and HREM techniques. Both low and high-angle GBs were well structured at the atomic scale. No amorphous GB phases were found in any of the GBs. However, yttria segregation to GBs after high-temperature anneals was indicated by EDS. The atomic-scale structures, although in detail quite different from previously investigated oxide GBs, such as the Σ5, (210) GB in NiO, share a number of structural features with other oxide GBs. These include the tendency toward coherence between low-index planes crossing the GB, misfit localization, and the formation of many types of asymmetric facets that include low-index planes. The fact that well-structured GBs free of secondary phases can be produced in YSZ is of technological importance, especially for fast-ion conduction applications, such as in high temperature fuel cells.