Mullite whisker frameworks were fabricated by vapor-solid reaction with SiO2, Al2O3 and AlF3 powders as the whisker forming agent at high temperatures. The effects of heating temperature and soaking time on the weight loss, liner shrinkage, porosity, microstructure and compressive strength were investigated. The results showed that with the increasing of the sintering temperature and soaking time, the weight loss and liner shrinkage of the samples increased and the porosities decreased due to the accelerated vapor-solid reaction, resulting in strong bonding and grain growth of the mullite frameworks. The compressive strength of the samples increased with increasing the sintering temperature from 1500 to 1650°C, and decreased with the soaking time extended to more than 5 h for 1500°C and 2 h for 1650°C. A maximum compressive strength of 142 MPa at a porosity of 62.3% was obtained for the mullite whisker framework heated at 1500°C for 5 h. The enhanced strength was attributed to the strong bonding strength and fine mullite grains resulting from a relative lower heating temperature and a modest soaking time.

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.