Abstract
Methods for evaluation of equilibrium and effective distribution coefficients of admixtures for preparation of high purity metals by crystallization methods, zone melting and directional crystallization, are presented in the paper. k_eff is evaluated by analysis of concentration profile curves after zone melting, e.g. using special radionuclides as marker admixtures by nondestructive integral method based on Burris-Stockman-Dillon equation.
Method of rapid solidified zone is used during electron beam zone melting (floating zone method) of refractory metal for direct specification of admixture concentration in liquid phase and solid phase very near before the solidified zone. By that technology it is possible, by a destructive method, to evaluate real values of k_eff for specific conditions of crystallization.
For low crystallization speed it is possible to express the functional dependence k_eff = f(v) by Burton-Prim-Slichter equation, and extrapolating it for v → 0, to reach the experimental limit values k_{o exp}, which can be compared with the limit value of the equilibrium distribution coefficient k_{o lim}.

Key words
effective distribution coefficients, zone melting, rapid solidification method, radiometric absorption analysis

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