Thermal conductivity of Al2O3-AlN ceramics

The effect of AlN on the thermal conductivity of aluminum oxide, pressureless sintered at nitrogen atmosphere, was investigated. With increasing aluminum nitride content up to 1 similar to 10 mol%, the thermal conductivity of Al2O3-AlN system was significantly decreased, and was constant when 20 and 25 mol% aluminum nitride were subsequently added. The thermal conductivity of the 1700 degrees C-sintered Al2O3 containing 1-10 mol% AlN showed a maximum, and it decreased with increasing sintering temperature. This phenomenon was attributed to the alpha-Al2O3 and AlON formed by the reaction of Al2O3 With AIN at less than or equal to 1700 degrees C, and the existence of a secondary phase, phi(5Al(2)O(3) AlN) phase at greater than or equal to 1750 degrees C. The thermal conductivity of the 1800 degrees C-sintered Al2O3 containing 20 and 25 mol% AlN showed a maximum value. Both alpha-Al2O3 and AlON existed at 1600 degrees C, while AlON phase existed only at greater than or equal to 1650 degrees C.