BCSJ : Vol. 78 (2005) , No. 7 pp.1259-1262

Growth of Hexagonal Bipyramidal Ruby Crystals by the Evaporation of a Li₂O–MoO₃ Flux

Katsuya Teshima¹⁾, Hitoshi Kondo¹⁾ and Shuji Oishi¹⁾

1) Department of Environmental Science and Technology, Faculty of Engineering, Shinshu University

(Received August 19, 2004)

The growth of hexagonal bipyramidal ruby crystals by the flux evaporation method in the Li₂O–MoO₃ flux system has been reported. Ruby crystals were grown by heating a mixture of a solute (Al₂O₃ + 0.5 wt % Cr₂O₃) and a flux (Li₂O–MoO₃) at 1050, 1100, or 1200 °C, followed by holding the solution at these temperatures for 5 h. The crystal size was dependent on the evaporation loss of the flux. The evaporation loss of the flux gradually decreased with increasing amount of Li₂O added to MoO₃, and increased with the holding temperature. The obtained ruby crystals had lengths of up to 2.6 mm and widths of up to 2.1 mm, and had a transparent-red color. Their form was a bipyramid, bounded by well-developed faces. The most suitable flux composition for high-quality and large ruby crystal growth was found to be 2 mol % Li₂O–98 mol % MoO₃.