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Precipitation and dissolution of KCaCl 3 impurity in NaCl crystals
Author(s) -
Andreev G. A.,
Buritskova L. G.,
Hartmanová M.
Publication year - 1978
Publication title -
kristall und technik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0023-4753
DOI - 10.1002/crat.19780130712
Subject(s) - nucleation , impurity , metastability , activation energy , dissolution , precipitation , annealing (glass) , diffusion , stoichiometry , kinetics , phase (matter) , materials science , crystallography , analytical chemistry (journal) , thermodynamics , chemistry , metallurgy , chromatography , physics , organic chemistry , meteorology , quantum mechanics
Impurity precipitation in NaCl crystals containing CaCl 2 and KCl in various proportions is studied by means of flotation density measurements. The paper is concerned with the determination and dissolution, the kinetics and activation energy, and the mechanism of nucleation. Two temperature regions for solid solution decomposition were revealed. The characteristic stages in density variation upon isochronal annealing are shown to be correlated with radical changes in the X‐ray diffraction patterns. Evidence is given that the nucleation is heterogeneous for the stable phase and homogeneous for the metastable one. – The activation energy in the low‐temperature region has been found to be 0.8 ± 0.1 eV, which suggests precipitation to be diffusion‐limited. From the kinetics studies it follows that the composition of the metastable phase corresponds to KCaCl 3 and the rate‐controlling stage in stoichiometric crystals is a K + diffusion.