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The optical anomalies are investigated and the internal stresses are calculated for lead molybdate crystals grown by the Czochralski method. An effect of the growth conditions on the distribution of stresses in the crystals is revealed. [ABSTRACT FROM AUTHOR]

Curved-face growth of NaNO3 crystals under the action of the (NH4)2Mo2O7 impurity is studied experimentally and possible causes of face bending are analyzed. Selective impurity adsorption on the basal pinacoid results in growth of platelike crystals with spherically bent faces. Growth-rate measurements show that the impurity decelerates pinacoid-face growth by the Bliznakov kink-poisoning mechanism. Face bending can be explained by gradual deceleration of step growth by the impurities accumulated before step fronts. A model of step deceleration is suggested that is based on the assumption of slow impurity adsorption resulting in the instability of a step train. The model allows one to qualitatively interpret the experimental data. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Dissymmetrization of (α-alum crystals of two isomorphous series, (NH[sub 4],K)AI(SO[sub 4])[sub 2] u 12H[sub 2]O and K(A1,Cr)(SO[sub 4])[sub 2] u 12H[sub 2]O, with different values of anomalous birefringence has been studied by X-ray diffraction methods. Dissymmetrization is revealed mainly from the comparison of the intensities of crystallographi- cally equivalent reflections in the space group Pa &3macr; characteristic of alum. The degree of dissymmetrization depends on the position in which the isomorphous replacements occurs, as well as on the growth sector of the crystal, and shows a good correlation with birefringence. [ABSTRACT FROM AUTHOR]

Twisting of PbMoO4 and PbWO4 crystals around the longitudinal axis during their growth in the [100] direction has been revealed. It is shown that this twisting is a purely morphological effect accompanying the development of facets on the growth front. [ABSTRACT FROM AUTHOR]