Preparation and characterization of α-Al_2O_3 submicron powders synthesized at low temperature by sol-gel method

Using Al(NO3)3.9H2O,Cu(NO3)2.3H2O and Ti(OC4H9)4 as raw materials,Al2O3 submicron powders were synthesized at a low temperature by the sol-gel process,and the phase and microstructure of powders were investigated.By doping Cu(NO3)2.3H2O and Ti(OC4H9)4 into alumina sol,a blue gel was obtained through placing the sol at 80℃ for a long time.Calcining the blue gel at 950℃ for 2 h produced amorphous Al2O3 powder with only a little γ-Al2O3 crystal phase,while α-Al2O3 nanopowders with a diameter of 80—100 nm were formed at the calcining temperature of 1000℃.As the calcining temperature increased to 1050℃,the grains grew to 200—400 nm.These results indicated that the synthesis temperature of α-Al2O3 was lowered and the grains growth was promoted by doping CuO-TiO2 precursors into alumina sol.