Diffusion creep in oxide ceramics

Although the models for diffusion creep were developed over 50 years ago, recently there has been considerable debate in the literature regarding the experimental validity of the models. This report summarizes recent theoretical developments in diffusion creep, with specific emphasis on ceramics. Concomitant microstructural changes during high temperature deformation, such as grain growth and cavitation, frequently interfere with the identification of the rate controlling process. Recent careful experiments coupled with appropriate microstructural characterization will be reviewed in structural oxide ceramics such as alumina and tetragonal zirconia; it will be demonstrated that these oxides deform by diffusion creep. Detailed analysis of the data in tetragonal zirconia will also be utilized to demonstrate the significance of diffusion creep in superplastic ceramics.