Effect of polymorphism of Al2O3 on the synthesis of magnesium aluminate spinel

MgAl2O4 spinet was prepared by reaction sintering and the effect of polymorphism of Al2O3 on the synthesis and densification of the spinet studied. gamma-Al2O3, rho-Al2O3 and alpha-Al2O3 were mixed with analytical reagent of MgO according to the stoichiometric spinet ratio, respectively, and pressed into billets with diameter of 20 mm and height of 15 mm. The green-body billets then were sintered at temperature from 800 degrees C to 1600 degrees C in an air atmosphere. Bulk density, porosity, linear expansion changes, phase composition, microstructure and grain size of final sintered products were analyzed. The results indicated that gamma-Al2O3 is beneficial for synthesize of spinet because it has a crystal structure similar to that of spine]. Among materials sintered at 1600 degrees C for 3 h, samples using gamma-Al2O3 as raw material had the highest density, up to 91% of the theoretical density of MgAl2O4, and had the largest grain size of spinel. (c) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.