Characterization of metastable tetragonal forms in ZrO2-2.8 mol pct 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 XRD 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 the temperature is increased, a reversible transformation between both forms involving a redistribution of the oxygen vacancy occurs. Once the transition is completed, the oxygen vacancy movement is described by a fast relaxation regime with an activation energy of 0.50 +/- 0.04 eV. (Author)