Pressureless sintering of gelcast ZTA–MgO–TiO 2 systems as potential dental ceramics

Abstract

The pressureless sintering behaviour of gelcast zirconia toughened alumina (ZTA) containing the total 5 wt-% additives of MgO and TiO₂ was investigated. The effects of four combinations of MgO and TiO₂ on the bulk properties, morphology and phase composition of the ZTA composites were evaluated in comparison with pure ZTA in the temperature range of 1150–1600°C. Four combinations of MgO and TiO₂ initiated effective densification and enhancement at 1450°C, as indicated by the relative density and three-point bending strength measurements and fracture morphological observations by using scanning electron microscopy. X-ray diffraction analyses confirmed that the difference in the bending strength among four groups of ZTA composites was due to the MgO dependent formation of minor MgAl₂O₄ and TiO₂ induced polymorphic transformation of tetragonal phase to monoclinic ZrO₂. These results are useful to further develop dental ceramics, including glass infiltrated ZTA.