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A semiempirical method is proposed, by which the role of kinetical constraints to the growth in closed tube chemical vapour transport can be evidenced.The method is based on the evaluation of the ratio (@) between the quantity D!E which is related to the semiempirically-determined average diffusivity of the gaseous species during the growth process, and the quantity O r x , which is related to the maximum average diffusivity of the gaseous species as is predicted, through the choice of a suitable diffusional model, by the equilibrium thermodynamics and diffusion properties of the vapour phase. 1962, 1964), ii) absence of free-convection as well as of iii) heat-transport limitations, the CT-CVD crystallization rate can be given, for 8 one-dimensional model, by (1) AH AT -RPa Aa J = -

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