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Kinetics Parameters and Thermodynamic Properties of Calcium Tungstate Crystal Growth from Lithium Chloride and Sodium Tungstate Melts
Author(s) -
ROY B. N.
Publication year - 1980
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1980.tb10637.x
Subject(s) - sodium tungstate , tungstate , enthalpy , arrhenius equation , crystallization , activation energy , diffusion , sodium , lithium chloride , crystal (programming language) , chemistry , gibbs free energy , thermodynamics , inorganic chemistry , analytical chemistry (journal) , materials science , mineralogy , tungsten , chromatography , physics , organic chemistry , computer science , programming language
Using an ordinary Arrhenius equation k Dl = k 0 e −EIRT , energy ( E ), enthalpy (Δ H a ), entropy (Δ Sa ), and free energy (δ G a ) of activation and the preexponential factor ( K 0 ) were estimated for diffusion‐controlled crystal growth of calcium tungstate from solutions in lithium chloride and sodium tungstate melts. Although E was small and increased slightly with increased cooling rates ( R T ), there was no direct correlation. The Δ H a , Δ S a , and Δ Ga were unaffected by the changes in R T and crystallization temperature ( T 0 ). The distance ( d 12 ) between a diffusing particle and its host crystal, necessary for a successful diffusion, was estimated. Such distances increased with T 0 and R T for the system CaWO 4 ‐Na 2 WO 4 but, for the system CaWO 4 ‐LiCl, they decreased with R T and increased with T 0 .