Raman spectra and vibrational analysis of nanometric tetragonal zirconia under high pressure Original Research Article

Raman spectra of nanometric tetragonal zirconia have been recorded under high pressure up to 31 GPa. The two lowest frequency modes exhibit an unusual over-damped soft mode behaviour upon increasing pressure. The non-crossover of these modes is the indication that they belong to the same symmetry and this lead us to reconsider the previous normal mode assignment. A new assignment of Raman active mode is deduced from normal mode calculations based on the linear chain model. The continuous loss of intensity and the softening of the Eg low frequency mode are likely associated with a phase transition which could take place around 38 GPa. The discussion of an evolution of the compound towards a possibly distorted fluorite-like structure at high pressure is based on the reduction of the number of Raman bands and on the decrease of the anisotropy of the microscopic compressibility coefficients estimated from the pressure evolution of force constants.