Phonon spectra evolution and soft-mode instabilities of zirconia during the c-t-m transformation

The joint lattice-dynamical model treatment of c-, t-, and m-polymorph of Z rO2 is conducted with an emphasis on the evolution of their vibrational spe ctra during the structure variation. The soft mode mechanisms are establish ed for both c-t and t-m phase transitions and some challenging points of re levant Raman-scattering evidence are discussed. The results obtained propos e the assignment of the bands observed in Raman spectra of t-ZrO2 other tha n those conventionally accepted in the literature, explain the stabilizatio n mechanism of the doped t-ZrO2, and clarify some points in the interpretat ions of the Raman and infrared spectra of m-ZrO2. (C) 1999 Elsevier Science Ltd. All rights reserved.