ABSTRACT
High temperature plasticity of YAP and YAG single crystals was experimental investigated to understand the correlation between plasticity and crystal structure. YAG showed a very high resistance to creep and the plastic deformation was attributed largely to the dislocation glide. In the case of YAP, plastic deformation resulted from dislocation climb and the resistance to creep was significant lower than that of YAG at a comparable condition. The difference showed a clear control of creep mechanism over the high temperature plasticity. Crystal plasticity is primarily determined by the Peierls stress when dislocation glide dominant i n creep and a well defined plasticity-systematics found among YAG and other oxide garnets. Similar plasticity systematica is failure in the YAP (weakest slip system) and the other perovskites, in which dislocation climb is involved in creep. This observation implies that plasticity systematics works only for the materials undergoing creep through dislocation glide, and gives the constrain to searching for strong materials based on the plasticity of known materials.
