Effect of ZrO₂ and MgO doping on microstructure and properties of translucent alumina fabricated by rapid vacuum sintering

Abstract

Translucent alumina doped with ZrO2 and MgO was fabricated by two-step vacuum sintering (1475[Formula: see text]C/30[Formula: see text]min followed by 1320[Formula: see text]C/20[Formula: see text]min) with a high heating rate (80[Formula: see text]C/min). Densification, grain size, phase composition, mechanical properties and translucency of the alumina were investigated. The results indicated that co-doping of ZrO2 and MgO showed a synergetic effect on grain refinement and densification process. On one hand, the solubility of MgO in alumina was increased by the ZrO2 additive, which was favorable for the densification. On the other hand, more favorable ZrO2 accommodation sites existed at the alumina grain boundaries created by the MgO, effectively decreasing the grain size. Finally, the sample with porosity of 0.5% and mean grain size of 1.21[Formula: see text][Formula: see text]m was obtained at a co-doped content of 0.35[Formula: see text]wt.% of ZrO2 and MgO (mass ratio of 1:1). The co-dopants led to the enhanced hardness and bending strength as well as a favorable fracture toughness of the translucent alumina, when compared with the MgO single-doped and doping free samples. Moreover, total transmission of as high as 51% and good translucency was also obtained. The improved properties widened the prospect of the translucent alumina used as dental restorative materials.