2016 年 124 巻 4 号 p. 375-380
We propose a new master sintering curve (MSC) theory for liquid phase sintering in consideration of grain rearrangement and solution-precipitation in order to analyze the sintering behaviors of silicon nitride (Si3N4) powder compacts. We found that the MSC for liquid phase sintering is theoretically the same expression as that for solid-state sintering. Very fine high-purity powders of Si3N4 Y2O3, Al2O3, AlN, and TiO2 were used as the raw materials to make powder compacts. The degree of sintering shrinkages of the powder compacts, which contained different amounts of the sintering aids, were measured directly by the laser displacement measurement method using a dilatometer. Based on the displacements and the specimen dimensions, the shrinkage ratios and rates could be calculated. The sintering shrinkage behavior depended on the sintering aid used and the heating rate. The MSCs were obtained for shrinkage ratios of 0–2 and 2–15% corresponding to grain rearrangement and the solution-precipitation process, respectively. Finally, the apparent activation energies of sintering of Si3N4 for grain rearrangement and the solution-precipitation process were found to be 251–294 and 345–430 kJ/mol, respectively, depending on the sintering aid used.
