Thermodynamics Aspects of Chemical Vapour Deposition of V-VII Group Metals and their Alloys with Tungsten

Abstract
The composition of the gas and solid phases for the metal (V, Nb, Ta, Mo, W, Re)-fluorine-hydrogen (Me-F-H) systems in the temperature range 400-2000 K at pressures of 1.3x10⁵ Pa and 2 kPa and for fluoride to hydrogen ratios from 1:3 to 1:100 have been calculated using complete basic data of thermochemical constants of the fluorides in different valent and structural states. It was established that the moving forces (supersaturation) of the metal crystallization in these systems decrease in the following order : Re, W, Mo, Nb, Ta, V. Thermodynamics of tungsten solid solutions in V, Nb, Ta, Mo and Re was considered in the frames of the crystallization theory. It was shown that the temperature of tungsten deposition from the Me-F-H systems in the CVD processes increases with the addition of Re, W, Mo, V, Nb, Ta fluorides (in the order of increment).