EFFECT OF YTTRIA ON THE THERMAL-CONDUCTIVITY OF ALUMINUM NITRIDE

The effect of yttria additions up to 10 wt% on the thermal conductivit y of pressureless-sintered aluminum nitride was investigated. Addition s of up to 3 wt% increased the thermal conductivity to values around 1 60 W/(m . K). Additions higher than 5 wt% slowly decreased the thermal conductivity because of the increasing volume fraction of the low-con ductivity yttrium aluminate phases. In all cases samples containing th e same yttria content with the binder burned out in nitrogen had highe r thermal conductivity than those with the binder burned out in air. C omparisons are made to previous studies containing additives of silica and calcia to aluminum nitride.