Preparation of alumina ceramic by κ-Al2O3

This work aims to use κ-Al2O3 transition alumina to prepare alumina ceramics without cracks. It is found that the major reason for the cracking of κ-Al2O3 sintered bodies formed by traditional wet molding process is the inner stress in green bodies rather than the volume reduction during the κ-Al2O3 - α-Al2O3 phase transformation. The cold isostatic pressing can be used to eliminate the inner stress generated in the green bodies, the sintered bodies have no cracks and possess the microstructure which is close to that of the α-Al2O3 ceramic products formed by wet molding process. Due to the fact that the calcining temperature of κ-Al2O3 is much lower than that of α-Al2O3 (1050 °C in comparison with 1400 °C), the application of κ-Al2O3 can lower the production cost significantly.