Abstract: The magnesium aluminum spinel was synthesized by light calcined magnesia with different activity and α-Al2 O3 by solid-phase sintering process .The effects of MgO activity on phases composition , cell parameters , microscopic structure and sintering properties to magnesium aluminum spinel were researched .And the mechanism was also discussed .The phases composition and cell parameters of synthetic sample were analysed by XRD and HighScore Plus software .The microscopic structure of synthetic sample was characterized by SEM .The results show that the high activity light calcined magnesia has higher defect energy , which can accelerate the sintering reaction and reduce the synthesis temperature of MgAl2O4.The crystals growth of MgAl2O4 was promoted by high activity light calcined magnesia .The cell parameters and the unit cell volume of the MgAl 2 O4 increase with rising MgO activity . And the grain growth is more complete .

Key words: The magnesium aluminum spinel was synthesized by light calcined magnesia with different activity and α-Al2 O3 by solid-phase sintering process .The effects of MgO activity on phases composition , cell parameters , microscopic structure and sintering properties to magnesium aluminum spinel were researched .And the mechanism was also discussed .The phases composition and cell parameters of synthetic sample were analysed by XRD and HighScore Plus software .The microscopic structure of synthetic sample was characterized by SEM .The results show that the high activity light calcined magnesia has higher defect energy , which can accelerate the sintering reaction and reduce the synthesis temperature of MgAl2O4.The crystals growth of MgAl2O4 was promoted by high activity light calcined magnesia .The cell parameters and the unit cell volume of the MgAl 2 O4 increase with rising MgO activity . And the grain growth is more complete .