High‐Pressure Phase Transitions in Zirconia and Yttria‐Doped Zirconia

Abstract

Raman spectroscopy has been utilized to characterize the phase transformations and transition pressures in pure and doped zirconia containing 3, 4, and 5 wt% Y2O3. The pressure‐induced transformations were investigated to over 6 GPa (at room temperature) using a diamond anvil pressure cell. Pure zirconia single‐crystal samples transformed to a “new” tetragonal phase (different from the one obtained at high temperatures at atmospheric pressure) at about 4 GPa. The pressure transformation, like the temperature transition, was reversible and exhibited an approximately 0.45‐GPa hysteresis at room temperature. The 3 and 4 wt% Y2O3 crystals underwent a monoclinic (P21/b) to tetragonal (P42 nmc) phase transition similar to that observed at high temperatures. This phase change was found to be irreversible on releasing the pressure. The 5 wt% Y2O3 at atmospheric pressure consists of a tetragonal modification in a disordered cubic matrix; a gradual, but reversible, disordering transformation of the tetragonal precipitate takes place with pressure.