On thermodynamic equilibria of solid BN and gas phases in the B−N−H−Cl−He system

Abstract

Thermodynamic analysis of the chemical vapour deposition (CVD) of boron nitride was performed for the B−N−H−Cl−He system, with new thermodynamic 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 × 10 3 and 1.013 × 10 5 Pa and fora wide range of atomic ratios of elements in the system. The results arc presented in the form of CVD phase diagrams which are a good way of illustrating the influence of the system parameters on the formation of stable phases. c-BN is formed in a quasi-equilibrium process at temperatures below 1804 K, the h-BN modification is most stable above this temperature, and w-BN is a metastable phase for all possible variations of the process conditions.