Effect of Y2O3 content on densification, microstructure and mechanical properties of reaction sintered magnesium aluminate spinel

Dense magnesium aluminate (MgAl2O4) spinels were developed via single-stage solid-state reaction sintering method at 1550-1650(o)C using combinations of varied commercial grade reactants-three different sources of alumina and two different sources of magnesia. The effect of Y2O3 doping in the concentration range of 1-4 wt % on different spinel batches was studied. Y2O3 addition was found to favour the densification of all the spinels at all dopant concentrations and maximum densification was found for the 2 wt % Y2O3 containing spinel batches. Phase analysis of the Y2O3 containing batches revealed the presence of yttrium aluminum garnet (YAG, Y3Al5O12) at all the sintering temperatures. Owing to similar crystal structure isotropic configuration of YAG (cubic) as that of spinel (cubic), Y2O3 doping was found to favour densification of spinel. Microstructural investigation revealed that Y2O3 containing batches have a controlled grain structure as compared to the without additive batches. Also, 2 wt % Y2O3 containing spinel batches sintered at 1650(o)C revealed better mechanical properties such as cold modulus of rupture and strength retainment after thermal shock than that of the undoped spinel batches.