ON THERMODYNAMIC EQUILIBRIA OF SOLID BN AND GAS PHASES IN THE B-N-H-CL-HE SYSTEM

Thermodynamic analysis of the chemical vapour deposition (CVD) of boro n nitride was performed for the B-N-H-Cl-He system, with new thermodyn amic data for different modifications of boron nitride (hexagonal h-BN , cubic c-BN and wurtzite w-BN). The phase equilibria were calculated for the temperature region 673-2273 K, at total pressures of 1.013 x 1 0(3) and 1.013 x 10(5) Pa and for a wide range of atomic ratios of ele ments in the system. The results are presented in the form of CVD phas e diagrams which are a good way of illustrating the influence of the s ystem parameters on the formation of stable phases. c-BN is formed in a quasi-equilibrium process at temperatures below 1804 K, the h-BN mod ification is most stable above this temperature, and w-BN is a metasta ble phase for all possible variations of the process conditions.