To improve the surface hardness of zirconia using a phase transition, bed sintering was conducted on 3mol% Y2O3-tetragonal zirconia polycrystal (3Y-TZP) embedded in hydroxyapatite (HA) powder and β-tricalciumphosphate (β-TCP) powder at 1450oC for different times. HA and TCP were decomposed to CaO, which is one of the stabilizers of zirconia at 1400 oC. Various properties of the specimens were analyzed. X-ray diffraction showed that CaO had diffused into ZrO2 and induced a tetragonal to cubic phase transition during the sintering process. At the same time, the zirconia pellet was densified during the sintering process. The microstructure of zirconia indicated that the thickness of the cubic phase at the surface increased with increasing sintering time. As a result, the Vickers hardness of the specimens processed by powder bed sintering was higher than that of the untreated specimen due to the formation of a cubic phase.

Keywords: Bed Sintering, Phase transformation, CaO, Zirconia