THERMODYNAMICS ASPECTS OF CHEMICAL-VAPOR-DEPOSITION OF V-VII GROUP-METALS AND THEIR ALLOYS WITH TUNGSTEN

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 1.3x10(5) 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 force s (supersaturation) of the metal crystallization in these systems decr ease in the following order: Re, W, Mo, Nb, Ta, V. Thermodynamics of t ungsten solid solutions in V, Nb, Ta, Mo and Re was considered in the frames of the crystallization theory. It was shown that the temperatur e 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).