Effects of Additive Li8SiN4 on cBN Crystal Morphology

After adding Li8SiN4 into the catalytic system of Li-complex borom nitrides, the glossy transparent cBN brown crystals were synthesized under the conditions of high pressure and high temperature in the range 4.5～5.0 GPa and 1 500～1 800 ℃ respectively. The morphology of cBN crystals is studied. The result shows that the percentage of blocky cBN crystals synthesized with Li8SiN4 increases obviously, and except the partial tuncated tetragonal crystals, the most of them are tuncated octahedral crystals. The edges and corners of cBN crystals are accurate and sharp, and surfaces of them are dense and smooth.