ABSTRACT
The nature of the cubic–to–tetragonal(c–t) transformation is briefly reviewed. Assuming that this transformation is a second–order phase transition, the c–t equilibrium is satisfactorily described with a firm thermodynamic basis. The microstructure evolution caused by this transformation is also reasonably explained on the same assumption. In particular, the modulated structure formed in some zirconia alloys is attributable to a spinodal decomposition. The generation of a fully tetragonal structure in some fine–grained, toughened zirconia is related to the nature of this transformation.
