RAMAN-ACTIVE MODES AND THE TETRAGONAL-MONOCLINIC PHASE-TRANSITION IN ZRO2 DOPED WITH 12 MOL-PERCENT CEO2

For the first time, we present a Raman scattering study of the tetragonal-monoclinic phase transition at low temperature in tetragonal ZrO2-polycrystal doped with 12 mol% CeO2 (Ce-TZP). Raman-active modes of symmetry A(1g), B-1g and E(g), A(g) and B-g for the tetragonal (D-4h(15);P4(2)/nmc) and monoclinic (C-2h(5);P2(1)/c) phases of Ce-TZP, are monitored in the temperature range 296-76 K by Raman scattering. It was found that the 139 cm(-1) B-1g and the 253 cm-1 E(g) modes for the tetragonal phase never disappear, but they coexist with the Raman-active modes for the monoclinic phase after the tetragonal-monoclinic phase transition is induced at 121 K; all Raman-active modes (9A(g) + 9B(g)) for the monoclinic phase are not detected whereas all Raman-active modes (A(1g) + 2B(1g) + 3E(g)) for the tetragonal phase are identified. The frequency, linewidth and intensity of each Raman-active mode are determined by Lorenzian-curve fitting to the Raman spectra before and after the phase transition. The 139 cm(-1) B-1g and the 253 cm(-1) E(g) modes, and the other Raman-active modes exhibit anomalies at 121 K in the frequency, intensity and linewidth vs temperature plot. The temperature dependence of frequency, linewidth and intensity for the Raman-active modes is discussed, with reference to structural or spectroscopic information on the tetragonal and monoclinic phases of ZrO2 and/or doped ZrO2.