Characterization of metastable tetragonal forms in ZrO2-2.8 mol% Y2O3 ceramics

This paper deals with a perturbed angular correlation investigation of the microstructure and subsequent thermal evolution of a commercial ZrO2-2.8 mol% Y2O3 ceramic powder and of a pellet obtained upon sintering the powder at 1450°C. The perturbed angular correlation results, complemented by those of X-ray diffraction and Raman spectrometry, indicate that the metastable tetragonal phase exhibits two hyperfine interaction forms instead of the interaction associated with the conventional t-ZrO2 phase, both having different oxygen vacancy configurations around zirconium sites. While the powder sample exhibits mainly a very defective tetragonal form, the pellet exhibits a slightly distorted one as the major form. As temperature is increased, a reversible transformation between both forms occurs involving a redistribution of the oxygen vacancy. Once the transition is completed, the oxygen vacancy movement is described by a fast relaxation regime with an activation energy Eact = 0.50 ± 0.04 eV.