Control of Shrinkage during Sintering of Alumina Ceramics Based on Master Sintering Curve Theory

Abstract

The Master Sintering Curve (MSC) is quite useful for analyzing the shrinkage behavior of ceramics. It is possible to compare shrinkage behavior using MSCs that are obtained from different firing profiles. In this study, shrinkage behavior during sintering of green bodies of several kinds of Al2O3 based ceramics were evaluated, using an electric furnace equipped with a dilatometer to be controlled based on the MSC theory. Although all of the samples shrank monotonically, shrinkage behavior depended on the additive and heating rate. The MSC theory was applied to analyze shrinkage behavior. As a result, a different MSC could be obtained in Al2O3 with and without the addition of MgO. In the pure Al2O3, a single MSC could be obtained from shrinkage curves by firing at a heating rate of 7.5-20oC/min, though the shrinkage curve at a heating rate of 3-5oC/min did not correspond with the MSC. In contrast, shrinkage curves at heating rate of 5-20oC/min were converged in the case of the MgO doped Al2O3 to obtain a unique MSC independent of firing profile. Apparent activation energy for sintering was estimated as 555 kJ/mol in the pure Al2O3 and 880 kJ/mol in the MgO doped Al2O3. The firing profile to obtain a requested sintering shrinkage curve was predicted from the resultant MSC. A comparison between the predicted and the experimental shrinkage curves, showed good consistency, thus confirming that it is possible to control shrinkage behavior using the MSC.