INTERFACE SHAPE AND HORIZONTAL VARIATIONS OF AL AND GA CONTENTS IN SUBSTITUTED YIG SINGLE-CRYSTALS GROWN BY THE FLOATING ZONE METHOD

The shape of the solid-liquid interface in the TSFZ growth of a YIG single crystal was revealed by an etching technique, and the horizontal variations of the Al and Ga contents in the Al- and Ga-substituted crystals were determined by means of EPMA. The interface can be divided into three regions by their characteristics in cross-sectional profile. They are (1) core region, (2) intermediate region, and (3) peripheral region. The characteristics of growth striations in each region and the influence of the rotation rate on the interface shape suggest that the forced convection by crystal rotation is dominant in the melt above the core region, and the thermocapillary convection is dominant in the melt above the peripheral region. EPMA analysis indicated that the concentration of Al2O3 was higher in the peripheral region than in the core, and it was highest at the part 300-500 μm inside from the crystal edge. Such horizontal variation can be interpreted in terms of the local variation of the boundary layer thickness caused by the coexistence of convections of the different types in the molten zone. © 1979.