Growth and oxygenating studies of Bi 2+ xSr 2− xCa n−1 Cu nO 2 n+4+ δ single crystals

Abstract

Growth of Bi 2+ x Sr 2− x Ca n−1 Cu n O 2 n+4+ δ ( x≤0.2, n=1, 2) single crystals from self-flux is described using the techniques of slow cooling, Bridgman and travelling solvent floating zone (TSFZ) methods. TSFZ crystal platelets with dimensions of 20×5×2 mm 3 have been obtained. The crystal symmetry was identified to be orthorhombic for Bi 2.2Sr 1.8CaCuO 8+ δ grown by Bridgman method, and monoclinic for Bi 2.1Sr 1.9CuO 6+ δ grown by cold finger and TSFZ methods. Oxygen content was estimated in as-grown and post-annealed crystals. The as-grown crystals are generally found to have a deficiency of oxygen, which could be slowly taken up by post growth annealing. The Bi 2.2Sr 1.9CuO 6+ δ crystal grown by the Bridgman method exhibited a semiconductor-like behavior and a T c∼4.5 K obtained after annealing. The superconducting and electrical properties for all the crystals are affected by the oxygen content.