Growth of Bi₄Ge₃O₁₂ single crystal by the micro-pulling-down method from bismuth rich composition

Bi₄Ge₃O₁₂ (BGO) crystals are well-known scintillator material. In this study, BGO single crystal fibers were successfully grown by the micro-pulling-down method with resistance heating system. Considering the volatilization of bismuth, we grew fibers from two different Bi₂O₃ enriched composition (2.05 mol% Bi₂O₃-3 mol% GeO₂ and 2.1 mol% Bi₂O₃-3 mol% GeO₂). For the composition of Bi₂O₃ 2.1 molar ratio, the best single crystal fibers were obtained for pulling-down rate equal to 0.08 mm/min. The grown fiber crystals from that composition were transparent and nearly colorless except for a slight yellowish tint at the end of the fibers. The distribution coefficient of the Bi and Ge ions in the grown fibers was measured.