Low temperature and rapid preparation of zirconia/zircon (ZrO2/ZrSiO4) composite ceramics by a hydrothermal-assisted sol-gel process

Abstract Hydrothermal-assisted sol-gel process, a novel method of combining both advantages of sol-gel and hydrothermal processes, was developed to synthesize 0.2ZrO 2 /ZrSiO 4 composite ceramics. The effects of sintering temperature and pH value on the phase formation rates, microstructure and mechanical properties were investigated. The phase and microstructure evolutions of samples obtained from hydrothermal-assisted and conventional sol-gel process were compared. Dense zirconia/zircon ceramics can be obtained by hydrothermal-assisted sol-gel process followed by sintering at low temperature (1400 °C) and short time (6 h). It was found that the properties of ceramics strongly depend on sintering temperature and pH. The formation rates of zircon in samples obtained from hydrothermal-assisted sol-gel is higher than those of conventional sol-gel method. The acidity condition is beneficial to phase formation and densification of ZrO 2 /ZrSiO 4 ceramics. SEM images show that the structure of ceramics obtained from hydrothermal-assisted sol-gel is more compact when compared with those prepared by conventional sol-gel. Furthermore, improved Vickers hardness and fracture toughness can be achieved by hydrothermal-assisted sol-gel process.