On the mechanism of the cubic-tetragonal transition in ZrO2

Abstract This paper concerns the problem of the driving forces of the nonferroelectric structural phase transitions in cubic ZrO2, treated within the framework of lattice dynamics. In a simple model, we consider a short-range microscopic mechanism for the vanishing of the lattice vibration in this crystal. The most important calculational result is that the dispersion branch originating from the highest T2g vibration undergoes a very sharp decrease and provides the lowest-frequency X− 2 phonon (41cm−1) at the Brillouin Zone (BZ) boundary. The model explains why and how the lattice can lose its stability on cooling, and thus confirms the hypothesis of the X− 2 phonon vanishing mechanism.