Effect of CaF_2 on AlN-BN Ceramic Composites by Hot-pressing

A series of samples of AlN-BN ceramic composites with different contents of sintering additives CaF_2(0-4wt%) were prepared by hot-pressing in nitrogen atmosphere at 1850℃for 3h.The effects of sintering additives on densification,dielectric properties and thermal conductivity of AlN-BN composites were explored.The addition of CaF_2 results in improvements in the level of densification and purified the grain boundary.AlN-BN composites with relative density of 98.53%-98.54% are obtained when CaF_2 contents are 3wt%-4wt%.Dielectric constants of samples are between 7.29 and 7.60 and the best tan5 value is 6.28×10~(-4).It is found that dielectric constants increase with the increasing CaF_2 contents and depend on the density of the AlN-BN ceramic composites.The highest thermal conductivity reach 110W·m~(-1)·K~(-1) by adding 3wt% CaF_2.