This proposal combines the experimental and theoretical efforts of one ceramist, one chemist, and one applied mathematician, to seek a fundamental understanding of the basis of phase stability of zirconia and fluorite related materials; and the origin of fatigue behavior and the development of appropriate constitutive relationships of transformation toughened ceramics. EXAFS and XANES techniques will be used to coordinate with the mechanical properties of zirconia polymorphs. Analytical and computational modelling will be complemented by deformation and fracture experiments, under monotonic, cyclic, high strain rate, and high pressure loading conditions. %%%% This research promises to provide new insights to the micromodelling of transformation toughening of zirconia ceramics. It starts from the viewpoint of shear-dilatant plasticity. Information to be gained on phase stability of oxides is important not only for zirconia ceramics, but also to other oxide systems as well.