Kinetics of Mixed Crystal K₂(SO₄, CrO₄) Growth from Aqueous Solution

Abstract

The investigation of crystal growth kinetics and phase equilibria in the system K,SO,-K,Cr04 -H,O was carried out using the method for the determination of the saturation temperature and the growth rate by microscopic observation of the seed crystal behaviour. The kinetics of mixed crystal growth can be characterized by the expression V = 450.240'.~', where c i s the value of effective supersaturation of the solution calculated by taking into account the specific features of the phase equilibria diagram. Use of this criterion allows the control of the rate of delta crystal growth from solutions of variable composition.

Phase Relations of Mixed Crystals with Solutions: Characterization and Influence on Crystal Formation

“…It proceeds via inter-crystal diffusion, resulting in a change of surface composition that disrupts the surface-solution equilibrium. Fine autoepitaxial excrescences observed during the slow growth of K 2 (S,Cr)O 4 crystals [2] in vicinity of quasi-equilibrium [17] prove this conclusion. The use of a nomogram allows determination of the pathways of quasi-equilibrium or equilibrium crystallization for any initial point of any system.…”

“…The mean of the range was accepted as the saturation temperature value. The method was initially developed for compounds of fixed compositions [18] and was adapted [5,16,17] for systems saturated with an isomorphic pair. The adaptation included the following adjustments: (i) It was necessary to minimize the influence of supersaturation upon the crystal composition during all growth stages, otherwise the error of the equilibrium temperature determination can reach 2°C or more.…”

Anomalous Isomorphism and Mixed Crystals in the Systems NH4Cl:(Cu,Mn)

“…Growth Kinetics and Surface Micromorphology. The normal growth rates of NH 4 Cl {100} faces were measured with a light microscope in a microcrystallization cell 29 in solutions saturated at 31.5−35 °C and supercooled at ΔT = 1, 3, and 5 °C. Although strictly isothermal crystallization conditions were not achieved, the effect of temperature on the growth rate is much weaker than the effect of impurity concentration and can be neglected.…”

On the genetic nature of isomorphism: Mechanism of component selection during crystal growth

“…Glikin. E-mail: glikin@ag2460.spb.edu the systematic variations in the partition coefficient for isomorphic components with an increasing oversaturation of some Tutton salts (Zhmurova et al, 1962;Khaimov-Mal'kov, 1970a, 1970b); unusual overgrowths on the crystal faces of some lowsoluble sulfates, carbonates, and chromates (Melikhov and Merkulova, 1975;Prieto et al, 1997); the growth of epitaxial islands during the simultaneous dissolution of adjacent areas on the faces of semiconductor crystals of the A III B V type (Bolkhovityanov, 1981(Bolkhovityanov, , 1990; and the deceleration of the growth of mixed crystals compared to the growth of pure compounds in the K 2 (S,Cr)O 4 series (Kasatkin et al, 1995).…”

“…It was thought that the selection process was controlled by deformations in the crystal lattice around a newly incorporated particle (Iiyama, 1974, quoted from Urusov, 1997). The deceleration of the growth of mixed compounds and their local dissolution was believed to be accounted for by differences in the unit cell parameters (heterometry) of the matrix crystal and an overgrowing layer, with these differences inducing inconsistency defects and an increase in the potential at the growth front of a step (Melikhov and Merkulova, 1975;Bolkhovityanov, 1981Bolkhovityanov, , 1990Kasatkin et al, 1995).…”