Effect of impurities on the metastable zone width of solute–solvent systems

• Published in: Journal of crystal growth 2009-08, Vol.311 (16), p.4050-4061
• Main Author: Sangwal, K.
• Format: Article
• Language: English
• Subjects: A1. Adsorption; A1. Impurities; A1. Metastable zone width; A1. Nucleation; A2. Growth from solutions; A3. Inorganic compounds; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; General studies of phase transitions; Growth from solutions; Materials science; Methods of crystal growth; physics of crystal growth; Nucleation; Physics; Solid surfaces and solid-solid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2009.06.045

The novel approach to interpret the metastable zone width obtained by the polythermal method using the classical theory of three-dimensional nucleation proposed recently [K. Sangwal, Cryst. Growth Des. 9 (2009) 942] is extended to describe the metastable zone width of solute–solvent systems in the presence of impurities. It is considered that impurity particles present in the solution can change the nucleation rate J by affecting both the kinetic factor A and the term B related with the solute–solvent interfacial energy γ. An expression relating metastable zone width, as defined by the maximum supercooling Δ T max of a solution saturated at temperature T 0, with cooling rate R is proposed in the form: ( T 0/Δ T max) 2= F(1− Z ln R), where F and Z are constants. The above relation can also be applied to describe the experimental data on maximum supercooling Δ T max obtained at a given constant R as a function of impurity concentration c i by the polythermal method and on maximum supersaturation σ max as a function of impurity concentration c i by the isothermal method. Experimental data on Δ T max obtained as a function of cooling rate R for solutions containing various concentrations c i of different impurities and as a function of concentration c i of impurities at constant R by the polythermal method and on σ max as a function of impurity concentration c i by the isothermal method are analyzed satisfactorily using the above approach. The experimental data are also analyzed using the expression of the self-consistent Nývlt-like approach [K. Sangwal, Cryst. Res. Technol. 44 (2009) 231]: ln(Δ T max/ T 0)= Φ+ β ln R, where Φ and β are constants. It was found that the trends of the dependences of Φ and β on impurity concentration c i are similar to those observed in the trends of the dependences of constants F and Z on c i predicted by the approach based on the classical nucleation theory.