Effects of granule compaction procedures on defect structure, fracture strength and thermal conductivity of AlN ceramics

The effect of granule compaction procedures on defect structure, fracture strength and thermal conductivity was examined for AlN ceramics using the same starting granules. For this study, changing the order of the cold isostatic pressing (CIP) and dewaxing procedure was performed, which changed the compaction behavior of the granule bed. The structural examination of green and sintered bodies showed that the change of granule strength strongly influenced the size and concentration of the granule related defects in sintered bodies. A large difference of the fracture strength associated with the change of granule strength was noted, and it was ascribed to the difference between the defect structures in the sintered bodies. On the other hand, the thermal conductivity was kept almost constant (> 150 W/m K) against the process alteration.