Relation between biaxial flexure strength and phase transformation of zirconia with surface treatments

In this study, two types of tetragonal zirconia polycrystals (TZP) were used: a conventional yttria stabilized TZP (3Y-TZP) and a ceria stabilized TZP/alumina nanocomposite (CZA). All specimens were sandblasted with 70 μm-alumina and 125 μm-SiC. Heat treatment was performed at 1100°C for 10 min. XRD patterns of the specimens with grinding, sandblasting and heat treatment were determined, and the content of monoclinic zirconia was calculated using the XRD peak intensity ratios. The biaxial flexure strength of both zirconia increased with the sandblasting and decreased with the heat treatment. The biaxial flexure strength of CZA was higher than that of 3Y-TZP in each treatment. After sandblasting, the content of the monoclinic zirconia of CZA was much higher than that of 3Y-TZP. Although the monoclinic content with SiC-sandblasting was larger than alumina-sandblasting, the biaxial flexure strength with SiC-sandblasting was smaller than that with alumina-sandblasting. These results indicated that the volume expansion due to the phase transformation from tetragonal to monoclinic zirconia induced the compressive stress in the surface area. Furthermore, it suggests that CZA is more susceptible to stress-induced phase transformation by sandblasting than 3Y-TZP.