Mechanism of lowering the sintering temperature of Al2O3 ceramic by the addition of CuO–TiO2 (I)

The effects of CuO and TiO_2 additives on the sintering behavior,microstructure,phase composition,sintering activation energy and the mechanism of lowering the sintering temperature of Al_2O_3 ceramics have been investigated.The TiO_2 began to dissolve into Al_2O_3 and formed Al_2Ti_7O_(15) solid solution at the sintering temperature of 1150-1200℃,and the diffusion coefficient improved largely with the augment of Al~(3+) vacancy concentration,which was the essential reason why the sintering process of Al_2O_3 ceramic had been promoted by the TiO_2 addition.However,the solid solubility limit of TiO_2 was 2%-4%(mass fraction),and it was unuseful for lowering the sintering temperature of Al_2O_3 ceramic by doping superfluous TiO_2.The temperature of TiO_2 dissolved into Al_2O_3 could be lowed down to 1100℃with the addition of 0.4%CuO,which was effective to promote the sintering process of Al_2O_3 ceramic.The sintering activation energy of alumina ceramic doped with different CuO-TiO_2 was consistent with the above results.The sintering activation energy of Al_2O_3 ceramic was reduced to 54.15 kJ·mol~(-1) by adding 4%TiO_2 and 2.4%CuO.