Phase transformation of zirconia ceramics by annealing in hot water (part 2)

Abstract

The tetragonal-to-monoclinic phase transformation of 3 mol% and 4 mol% Y2O3-doped ZrO2 (Y-PSZ) was investigated by annealing at 140°C in hot water. Sintered bodies of 3Y-PSZ and 4Y-PSZ were prepared by sintering at 1350°C for 0-10 h, in air, and sintering at 1400 or 1450°C, respectively. A 3 mol% and 4 mol% Y-PSZ fine powder, synthesized by means of the hydrolysis method was used, as a starting powder. It was revealed that the Y2O3 concentration within the 3Y-PSZ tetragonal phase decreased and grain size was nearly constant as the holding time at 1350°C increased. When the sintered bodies of 3Y-PSZ were subjected to annealing in hot water, the phase transformation rate increased as the holding time increased. This behavior can be explained by considering the Y2O3 concentration within the tetragonal phase at constant grain size. In order to confirm the effect of grain size, a similar characterization was performed on 4Y-PSZ, which shows higher grain size than the 3Y-PSZ. It is shown that the behavior upon annealing in hot water depends only on the Y2O3 concentration within the tetragonal phase and not on the grain size. In addition, the phase-transformation behavior abruptly changes at the critical concentration of 2.75 mol% of Y2O3, which reveals that, for fractions>3.0 mol%, the phase transformation is completely controlled by the Y2O3 concentration within the tetragonal phase.