Electronic contribution to superplasticity in ceramics

Extensive tensile ductility during superplastic deformation in ceramics has been demonstrated experimentally in yttria stabilized tetragonal zirconia polycrystals, with the achievement of about 800% tensile elongation reported. It has not been possible to achieve such extensive elongations in other ceramics such as Si₃N₄/SiC composites and alumina. The authors consider that the extensive superplastic deformations obtained in ceramics could be associated with the fact that some ceramics can be classified as having a ‘metallic’ character based on the nature of the orbitals responsible for their bonding. These metallic ceramics show extensive superplastic deformation compared with other ceramics that can be classified as insulators based on the nature of their bonding orbitals. This observation would help to demarcate ceramic materials that can exhibit superplasticity from the brittle ceramics.