Analysis of two grain size α-Al2O3 sintering at low heating rate based on master sintering curves

Master sintering curves (MSC) were constructed for dry pressed compacts composed of either a submicrocrystalline or a microcrystalline alpha-Al2O3 powder using constant heating rate dilatometry data containing lower heating rates only. The MSC constructed for two grain size alpha-Al2O3 were used to evaluate the sintered densities, which agreed well with the density obtained with different heating procedures and determined by Archimedes method. So the applicability of the MSC theory to alumina ceramic sintering under lower heating rates was validated. Apparent activation energies for submicrocrystalline and microcrystalline alpha-Al2O3 were determined to be 1035 and 1148 kJ mol(-1) based on the MSC respectively. The calculated activation energies for densification are higher than the values reported in the literature concerning heating rates >5 K min(-1).