The origin of the threshold stress in pure 3mol%yttria tetragonal zirconia polycrystals was analysed in detail. In this regard, two explanations found in the literature were considered thoroughly. One of them invokes dislocation activity as the origin for such quantity, whereas the other one was based upon yttrium segregation at the grain boundaries. Critical assessment for both of them was performed, and it has allowed concluding that the dislocation activity observed by Morita and Hiraga was just an artefact created during sample preparation. Thence, segregation at the grain boundaries seems to be the only mechanism accounting for a threshold stress and its temperature and grain size dependence.

A Critical Assessment of the Dislocation-Driven Model for Superplasticity in Yttria Tetragonal Zirconia Polycrystals. A.Domínguez-Rodríguez, D.Gómez-García, M.Castillo-Rodríguez: Journal of the European Ceramic Society, 2008, 28[3], 571-5