Thermal conductivity of AlN ceramics sintered with CaF2 and YF3

Dense AlN ceramics with a thermal conductivity of 180 W/m.K were obtained at a sintering temperature of 1750 C using CaF2 and YF3 as additives. At temperatures below 1650 C, the shrinkage of AlN ceramics was promoted by liquid (Ca,Y)F2 and Ca12Al14O32F2. Liquid CaYAlO4 mainly improved the densification of the sample when the sintering temperature increased to 1750 C. The formation of liquid (Ca,Y)F2 at a relatively low temperature resulted in homogeneous YF3 distribution around the AlN particles, which benefited the removal of oxygen impurity in the AlN lattice, and thus produced a higher thermal conductivity. 13 refs.