Differences in the tetragonal to monoclinic phase transformation rate in hot water of 3 mol% Y2O3-ZrO2 ceramics under different surface conditions

摘要

Hot-isostatic-pressed(HIP'd) tetragonal zirconia ceramiccontaining 3mol% Y2O3 was soaked in hot water at 95-100°C toevaluate the transformation rate from the tetragonal (T) to themonoclinic (M) phase. The transformation rate differedconsiderably between the polished surface and the surface cut bya diamond wheel. After about 1000h of soaking in hot water, thevolume of the M-phase was 50% in the cut surface and less than 20%in the polished surface. Tetragonal ZrO2 with polished and cutsurface were annealed at 1000°C for 2h in air. When the annealedspecimens were soaked in hot water, the transformation rate in thecut surface was the same as that before annealing; on the otherhand, the M-phase volume in the polished surface increased to 70%after 1000 H of soaking. Surface roughness, a rhombohedral phasegenerated by cutting or machining and orientation of the T-phasecrystal due to machining, are thought to be causes of thetransformation rate change. However, not one of them on its owncould explain all the phenomena without contradiction.