SINGLE-CRYSTAL GROWTH OF AKERMANITE (CA2MGSI2O7) AND GEHLENITE (CA2AL2SIO7) BY THE FLOATING ZONE METHOD

The floating zone method was successfully applied to the single crystal growth of Ca2MgSi2O7 (akermanite) and Ca2Al2SiO 7 (gehlenite) using an apparatus of the radiation convergence type with a halogen lamp as the heat source. The resulting crystals were colourless, transparent and free from visual imperfections such as holes and inclusions. Examination with a polarizing microscope revealed the homogeneity of the grown crystals. Seeded growth of gehlenite was attempted along the [110] direction at a rate of 1 mm/h. It was recognized that for both akermanite and gehlenite the atmosphere of the growth region was related to the formation of holes in the crystals and of bubbles in the molten zone. A low partial oxygen pressure gas composed of pure air or nitrogen was chosen as the optimum growth atmosphere. © 1979.