Mechanism of Lowering the Sintering Temperature of Al2O3 Ceramic by the Addition of CuO–TiO2 (II)

The effects of CuO and TiO2 additives on the sintering behavior, microstructure, phase composition, sintering activation energy and the mechanism of lowering the sintering temperature of Al2O3 ceramics have been investigated. The TiO2 began to dissolve into Al2O3 and formed Al2Ti7O15 solid solution at the sintering temperature of 1150–1200oC , and the diffusion coefficient improved largely with the augment of Al 3+ vacancy concentration, which was the essential reason why the sintering process of A12O3 ceramic had been promoted by the TiO2 addition. However, the solid solubility limit of TiO2 was 2%–4% (mass fraction), and it was unuseful for lowering the sintering temperature of A12O3 ceramic by doping superfluous TiO2. The temperature of TiO2 dissolved into Al2O3 could be lowed down to 1100 with the addition of 0.4% CuO, which was effective to promote the sintering process of A12O3 ceramic. The sintering activation energy of alumina ceramic doped with different CuO–TiO2 was consistent with the above results. The sintering activation energy of A12O3 ceramic was reduced to 54.15 kJ·mol 1 by adding 4% TiO2 and 2.4% CuO.