Effect of Silicon Dioxide on the Thermal Diffusivity of Aluminum Nitride Ceramics

The thermal diffusivity of AlN ceramics was significantly decreased by the addition of SiO 2 . The AlN ceramics with 4 wt% SiO 2 could not be densified by pressureless sintering in the temperature range 1400° to 1800°C. The thermal diffusivity of these samples was very low because of their porous structure. The AlN ceramics containing 2, 4, and 8 wt% SiO 2 were densified by hot‐pressing and also had low thermal diffusivity. In these samples, the grains of the 27R polytype that resulted from the reaction between AlN and SiO 2 were dispersed, obstructing the conduction of heat. The relation between the amount of 27R polytype and the thermal diffusivity of the AlN ceramics was determined.