Effect of TiO 2 in Spinel Formation and Reactive Sintering of Magnesia-rich Ceramics

The solid solubility of magnesia in magnesium -aluminate spinel and magnesium-aluminate spinel in magnesia does not change with temperature thus not creating bonds over periclase grains in single stage sintering process. In the present study, magnesia and alumina powders along with tetravalent oxide (TiO2) additive was analyzed for its role in reactive densification of spinel in single stage firing process in order to achieve a better binding system for magnesia-based refractories. This tetravalent oxide on reaction with magnesia from spinel solid solution with MgAl2O4 as they have similar crystal structure. The spinel solid solution formed using oxide additive is expected to higher solubility in magnesia than magnesium- aluminate spinel, resulting in improvement of the bonding during sintering through increased in solid solubility at elevated temperatures, similar to the complex spinel in magnesia-chrome refractories. The formation of spinel during firing remains as a second phase that retards the grain growth of periclase.