Polar habits of the Bi12SiO20 crystals grown by the Czochralski method

Abstract Crystals of bismuth silicon oxide (Bi 12 SiO 20 ) with a diameter of 35 mm have been grown along 〈111〉 axes by the Czochralski method in an air atmosphere. The crystal morphology and the shapes of the crystal-melt interface are investigated. It has been shown that the shape of the growth interface changes from convex to concave towards the melt at a constant crystal diameter under the same pull and rotation rates throughout the growth. The inversion of the morphological polarity of the Bi 12 SiO 20 crystal during parallel growth can be qualitatively accounted for on the basis of the approximate analysis of the thermal stress and strain caused by the nonuniform temperature distribution in the growing crystal, which was previously given by Brice.