PRODUCTION OF HIGH-PURITY HEXAGONAL BORON NITRIDE POWDER

PURPOSE:To improve the purity by crushing a crystalline BN, dispersing the crushed crystalline BN in a solvent, subsequently filtering it, drying it, removing soluble components, carrying out heat treatment, grinding the heat treated material into a powder having an average particle size represented by a specified formula and then heat treating the resultant powder in a non-oxidative atmosphere. CONSTITUTION:A synthesized crystalline BN is crushed by a wet or dry method and the resultant crushed BN is dispersed together with a surfactant or a water soluble organic solvent in a washing water followed by stirring. The obtained dispersion is then filtered under a reduced pressure and the resultant cake is dispersed again in a washing water. After stirring, water soluble compounds (B) are removed by filtration and vacuum drying is then carried out. The dried material is then heat treated and subsequently crushed into a powder having a target average particle size represented by the formula [Y is average particle size (mum) of product BN and X is average particle size (mum) before heat treatment]. The obtained powder is heat treated at 1900-2200 deg.C in a non-oxidative atmosphere of N2, etc., thus obtaining the objective hexagonal BN powder having a composition of