ELECTRONIC CONTRIBUTION TO SUPERPLASTICITY IN CERAMICS

Extensive tensile ductility during superplastic deformation in ceramic s has been demonstrated experimentally in yttria stabilised tetragonal zirconia polycrystals, with the achievement of about 800% tensile elo ngation reported. It has not been possible to achieve such extensive e longations in other ceramics such as Si3N4/SiC composites and alumina. The authors consider that the extensive superplastic deformations obt ained in ceramics could be associated with the fact that some ceramics can be classified as having a 'metallic' character based on she natur e of the orbitals responsible for their bonding. These metallic cerami cs show extensive superplastic deformation compared with other ceramic s that can be classified as insulators based on the nature of their bo nding orbitals. This observation would help to demarcate ceramic mater ials that cart exhibit superplasticity from the brittle ceramics.