CHARACTERIZATION OF GRAIN-BOUNDARIES IN SUPERPLASTICALLY DEFORMED Y-TZP CERAMICS

The effects of compressive deformation on the grain boundary character istics of fine-grained Y-TZP have been investigated using surface spec troscopy, impedance analysis, and transmission electron microscopy. Af ter sintering at low temperature (1150-degrees-C), the grain boundarie s are covered by an ultrathin (1 nm) yttrium-rich amorphous film. Afte r deformation at 1200-degrees-1300-degrees-C under low stress, some gr ain boundaries are no longer covered by the amorphous film. Yttrium se gregation seems to occur only at wetted grain boundaries. Evidence has been found that the extent of dewetting increases with increasing app lied stress.