On the Origin of Lateral Fringes on Crystals Grown from the Melt

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Abstract
Alkali halide single crystals were grown by the Kyropoulos method, using rotatory and fixed seeds. In both techniques, horizontal fringes appear on the lateral surface of the crystals, which are parallel to the interface. The interfringe distance was found to be related with the thermodynamical constants of the material. From the analysis of heat transfer during the growth an expression was deduced which relates the thermodynamical constants, and the crystal and seed dimensions with the rate of growth. This formula is in good agreement with the experimental results. A mechanism of discontinuous growth, based on the effect of impurities at the moving interface, is suggested to explain the appearance of the fringes in both rotatory or fixed seed techniques. This mechanism is also used to interpret the results of other authors, which were not explained by other proposed mechanisms.