H. V. Alexandru^1,* , C. Berbecaru¹, R. C. Radulescu²

Abstract

Three crystals were simultaneously grown in the same conditions, 9 liters solution volume of the crystallisation chamber, by temperature lowering method. The growth kinetic of prismatic faces was measured for a period of ~30 days. Arrhenius corrections of the growth rates were made to 55 0C growth temperature. Prismatic faces are very sensitive to Me3+ impurities and have typical "dead" growth zone at small supersaturations. At higher supersaturations s ‡ 0.08, 2D-nucleation mechanism becomes dominant. Using 2D-nucleation formalism introduced by Chernov [14,21] we have found the edge free energy per growth unit kT 4 39 .0=g , in good agreement with the literature data. The coverage 6 10 33-· =q . of ad-molecules in the surface layer, susceptible to trigger 2D nucleation is of the same order of magnitude as Fe3+ impurities in solution and suggests a heterogeneous 2D-nucleation mechanism to be dominant. The lower limit of the adsorption energy ~18 kcal/mol of this impurity was estimated on the prismatic faces of KDP, much lower than ~9.5 kcal/mol the activation energy for growth. The critical coverage 4 10 63-· » q . * at the limit of the “dead” growth zone, much higher than previous figure, suggest the segregation coefficient of this impurity increases dramatically towards low supersaturation..

Keywords

Potassium dihydrogen phosphate, Solution growth, Kinetics, Mechanism of growth.

Submitted at: July 1, 2003
Accepted at: July 31, 2003

Citation

H. V. Alexandru, C. Berbecaru, R. C. Radulescu, MECHANISM OF KDP GROWTH FROM SOLUTION, Journal of Optoelectronics and Advanced Materials Vol. 5, Iss. 3, pp. 599-607 (2003)

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