Strain-induced destabilization of crystals: Lattice dynamics of the cubic-tetragonal phase transition inZrO2

The concept of the strain-induced interatomic tensions as the most general anharmonic factor responsible for mechanical instability of crystals is discussed. We employ this concept to examine the mechanism of the cubic-tetragonal phase transition in zirconia. According to the model prediction, the ${\mathit{X}}_2^{\mathrm{-}}$ phonon in the cubic phase would have a low frequency, and vanish when the interatomic separation diminishes. This supports the hypothesis that this phonon’s condensation is responsible for the transition in question. The cubic-tetragonal-monoclinic evolution of the lattice and related phenomena are discussed in the light of the results obtained.