RAMAN-SCATTERING STUDY OF CUBIC-TETRAGONAL PHASE-TRANSITION IN ZR1-XCEXO2 SOLID-SOLUTION

A structural phase transition between the cubic (space group, Fm3m) and tetragonal (space group, P4(2)/nmc) phases in a zirconia-ceria solid solution (Zr1-xCexO2) has been observed by Raman spectroscopy. The cubic-tetragonal (c-t'') phase boundary in compositionally homogeneous samples exists at a composition X0 (0.8 < X0 < 0.9) at room temperature, where t'' is defined as a tetragonal phase whose axial ratio c/a equals unity. The axial ratio c/a decreases with an increase of ceria concentration and becomes 1 at a composition X0' (0.65 < X0' < 0.7) at room temperature. The sample with a composition between X0 and X0' is t''-ZrO2. By Raman scattering measurements at high temperatures, the tetragonal (t'') --> cubic and cubic --> tetragonal phase transitions occur above 400-degrees-C in Zr0.2Ce0.8O2 solid solution.