Effect of oxygen on the thermal conductivity of aluminium nitride ceramics

Sintered aluminium nitride is a good thermal conductor which is one of the principal properties of this ceramic. Previous studies have shown that the thermal flux transfer depends strongly on the oxygen contained in the crystal lattice, and on the powder surface. An AlN ceramic containing YF3 as additive has been fabricated by tape-casting and sintering. This study shows that binder burnout must be carried out in air at 550 degrees C or in nitrogen at 650 degrees C. Sublimation of YF3 to YOF, and formation of yttrium aluminate occurred during calcination. The amount of YF3 present, thermal treatment duration and the rate of temperature increase and decrease affected oxygen diffusion in the nitride lattice. However, there is no correlation between thermal conductivity and oxygen content and microstructural characteristics are more influential than total oxygen content up to a thermal conductivity value of 220 W/mK. Published by Elsevier Science Limited.