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Kinetics of Crystal Growth of Calcium Tungstate from Solutions in Sodium Tungstate Melts by Continuous Cooling
Author(s) -
ROY B. N.,
APPALASAMI S.
Publication year - 1978
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.1151-2916.1978.tb09225.x
Subject(s) - crystallization , tungstate , sodium tungstate , supersaturation , diffusion , crystal (programming language) , crystal growth , kinetics , sodium , materials science , reaction rate constant , analytical chemistry (journal) , chemistry , inorganic chemistry , mineralogy , thermodynamics , crystallography , metallurgy , tungsten , chromatography , physics , organic chemistry , quantum mechanics , computer science , programming language
Crystallization kinetics of calcium tungstate from unstirred supersaturated solutions in sodium tungstate melts was studied by continuous cooling from initial crystallization temperature T O =1000° to 800°C to room temperature at cooling rates R T =0.67° to 3.3°C min −1 . Crystals were examined by optical microscopy and analyzed by various methods. The main crystal growth was diffusion‐rate‐controlled. The final crystal growth was rate‐controlled by the development rate of excess solute concentration. Diffusion rate constant ( k D ) values were estimated. These values increased with cooling rate and initial crystallization temperatures but they are very much smaller than the rate constants for diffusion‐controlled growth of calcium tungstate from lithium chloride melts.