MORPHOLOGY AND DEFECT CHARACTERISTICS OF VERTICALLY PULLED MGAL2O4 SINGLE CRYSTALS

Optical, etch pit and X-ray topographic studies of magnesium aluminate spinel (MgAl2O4) have shown that undoped single crystals vertically pulled from stoichiometric melts can exhibit a high degree of crystalline perfection. The principal defect is strain arising from the formation of {111} facets on the solid/liquid interface. This effect is inhibited by suitable control of interface shape, but is greatly enhanced by the presence of chromium which segregates non-uniformly between the facets and the bulk of the crystal. Chromium also causes strain in the impurity-rich bands corresponding to growth striations. © 1969 Chapman and Hall.