Calculation of the Distribution Coefficient for Sr²⁺ in LaF₃ Crystal at Infinite Dilution, Based on the Data on Directional Solidification of La_1 − ySr_yF_3 − y Solid Solutions

The thermodynamic distribution coefficient for Sr²⁺ impurity in LaF₃ crystal at infinite dilution (c → 0) k₀ = 1.60 ± 0.02 is determined based on the data on directional solidification of La_1 − ySr_yF_3 − y solid solutions (0.01 ≤ y ≤ 0.15, LaF₃ tysonite structure type). The obtained k₀ value is in good agreement with the estimated distribution coefficient k₀ = 1.7, which was found previously by modified cryoscopy from the liquid–solid phase diagram of the SrF₂–LaF₃ system.