Growth and oxygenating studies of Bi2+xSr2-xCan-1CunO2n+4+δ single crystals

Growth of Bi2+xSr2-xCan-1Cu2O2n+4+delta (x less than or equal to 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 20X5X2 mm(3) have been obtained. The crystal symmetry was identified to be orthorhombic for Bi2.2Sr1.8CaCuO8+delta grown by Bridgman method, and monoclinic for Bi2.1Sr1.9CuO6+delta 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 Bi2.2Sr1.9CuO6+delta crystal grown by the Bridgman method exhibited a semiconductor-like behavior and a T-c similar to 4.5 K obtained after annealing. The superconducting and electrical properties for all the crystals are affected by the oxygen content. (C) 2000 Elsevier Science B.V. All rights reserved.