Densification and grain growth of a refractory grade magnesia derived from magnesite

Magnesite calcination experiments were performed employing additions of differing amounts of magnesium chloride, magnesium acetate, and lithium carbonate. The effects of these additives on the properties of the calcined powder, green compacts, and sintered specimens were analyzed. The addition of magnesium chloride promoted the coarsening of the resultant periclase crystallites and the breakdown of pseudomorphic structures formed during the calcination process. A volatilization reprecipitation process is suggested to be the promoting mechanism. High density sintered specimens were obtained in this case. Additions of magnesium acetate and lithium carbonate did not significantly affect the final properties of the sintered specimens.; Zirconia, zirconium silicate, and magnesium pyrophosphate were introduced as additives in the sintering of a refractory grade magnesia. Additions of the zirconium compounds promoted densification and periclase crystal growth during the sintering process. Liquid-phase sintering mechanisms are suggested to be associated with these effects. Additions of magnesium pyrophosphate resulted in a reduction on the bulk density of sintered specimens which was related to the partial volatilization of this additive.