Sintering of Alumina-Reinforced Ceramics Using Low-Temperature Sintering Additive

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering of dense ceramic bodies in relatively low temperatures (up to 1100 °C) was possible with the usage of CuO-TiO2-Nb2O5-based additive, together with an intense milling process. By using the XRD method, the formation of dominant α-Al2O3 and m-ZrO2 phases with small concentrations of secondary ones in experimental samples was confirmed. SEM studies showed that uniform distribution of components in the composite was achieved in samples sintered from intensively milled powders. The significant increase in the values of Vickers hardness and biaxial flexural strength (by 2.6 times) in samples from intensively milled powders at a sintering temperature of 1050 °C was explained by reduced porosity, improved grain distribution, and the formation of the t-ZrO2 phase in the alumina-reinforced composite. The study clearly showed high potential of the proposed low-temperature sintering method for zirconia-toughened aluminum oxide, which can be used in manufacturing of advanced ceramics.