Effect of CeO_2 and ZrO_2 additives on microstructure and thermal stability of high-energy ball milling Al_2O_3 powder

The phase transformation and thermal stability of Al_2O_3 during high-energy ball milling were investigated by means of X-ray diffraction(XRD) and scanning electron microscopy(SEM).The effect of CeO_2 and ZrO_2 additives on the phase transformation and thermal stability of Al_2O_3 during high-energy ball milling and annealing was also studied.The results show that with the increase of ball milling time,the grain size of Al_2O_3 powder decreases and part of γ-Al_2O_3 transforms to α-Al_2O_3.After ball-milling for 30h and subsequently annealing at 850℃,Al_2O_3 powder transforms completely to α-phase.However,with addition of CeO_2 and ZrO_2,the transformation of γ-Al_2O_3 to α-Al_2O_3 is restrained effectively during ball milling and the temperature for the phase transformation increases to above 1000℃.The results demonstrate that the thermal stability of γ-Al_2O_3 powder is improved by the addition of CeO_2 and ZrO_2.