On the Production of Bismuth and White Tin Single Crystals by the Bridgman Method

Abstract

The effects of the purity of the material and the lowering rate of the mold on the yield percentage and orientation distribution of round-bar single crystals (about 5 mm in diameter) of trigonal bismuth and tetragonal tin as grown by the Bridgman method have been studied. The suction casting was used for the preparation of ingots. In bismuth, for which three materials were used, the yield percentage decreases approximately exponentially with increasing lowering rate of the mold, irrespective of the purity of the material, and the higher the purity of the material the greater is the yield percentage. Single crystals with θ (the angle which the rod axis makes with the c axis)\gtrsim70° are grown most easily, while crystals with θ=10∼40° are difficult to grow. Single crystals of nearly all orientations grow at low lowering rate of the mold, but single crystals of small θ do not grow at fast lowering rates of the mold. In white tin, the yield percentage decreases approximately linearly with increasing lowering rate of the mold. As for the crystal orientation, the ⟨110⟩ direction predominates at fast lowering rates of the mold, although all orientations are possible at slow mold-lowering rates.