CHARACTERIZATION OF METASTABLE TETRAGONAL FORMS IN ZRO2-2.8 MOL-PERCENT Y2O3 CERAMICS

This paper deals with a perturbed angular correlation investigation of the microstructure and subsequent thermal evolution of a commercial Z rO2-2.8 mol% Y2O3 ceramic powder and of a pellet obtained upon sinteri ng the powder at 1450 degrees C. The perturbed angular correlation res ults, complemented by those of X-ray diffraction and Raman spectrometr y, indicate that the metastable tetragonal phase exhibits two hyperfin e interaction forms instead of the interaction associated with the con ventional t-ZrO2 phase, both having different oxygen vacancy configura tions around zirconium sites, While the powder sample exhibits mainly a very defective tetragonal form, the pellet exhibits a slightly disto rted 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 vaca ncy movement is described by a fast relaxation regime with an activati on energy E(act) = 0.50 +/- 0.04 eV.