Bridgman growth of Li/sub 2/B/sub 4/O/sub 7/ crystal of 4-inch diameter

Lithium tetraborate Li/sub 2/B/sub 4/O/sub 7/ (LBO) piezoelectric crystal of 4-inch diameter by 3-inch length was grown by the modified Bridgman method. The most important factor in large diameter of LBO growth is growth rate of the crystal. In order to ensure perfection of LBO material, core-free, twin-free, no crack and no striation, the growth rate V must be reduced with increasing of the diameter D of LBO boule. The relationship between V and D obeys the fitting equation of experimental curve: V=(0.14+0.34 D)/sup -1/. The irregularity of V and its influenced factors, such as the fluctuation of the furnace temperature, the shape and location of solid-liquid (S-L) interface in the furnace as well as effects of V on perfection of the crystal have been also reported.