Lattice-dynamical study of the cubic-tetragonal-monoclinic transformations of zirconia

Vibrational and elastic properties of cubic and tetragonal phases of zirconia are discussed within the framework of quantitative lattice-dynamical treatments. The results reveal mechanical instabilities of both phases originating from the stresses inherent for these structures, and show that c-t and t-m transformations of ${\mathrm{ZrO}}_{2}$ are driven by successive condensations of the zone-boundary modes whose softening is induced by the interatomic tensions.