Raman Scattering Study of Cubic–Tetragonal Phase Transition in Zr 1−x Ce x O 2 Solid Solution

A structural phase transition between the cubic (space group, Fm 3 m) and tetragonal (space group, P 4 2 /nmc) phases in a zirconia–ceria solid solution (Zr 1−x Ce x O 2 ) has been observed by Raman spectroscopy. The cubic–tetragonal ( c–t″ ) phase boundary in compositionally homogeneous samples exists at a composition X 0 (0.8 < X 0 < 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 X′ 0 (0.65 < X′ 0 < 0.7) at room temperature. The sample with a composition between X 0 and X′ 0 is t ″ ZrO 2 . By Raman scattering measurements at high temperatures, the tetragonal ( t″ ) → cubic and cubic → tetragonal phase transitions occur above 400°C in Zr 0.2 Ce 0.8 O 2 solid solution.