GROWTH OF LARGE-SIZE SINGLE-CRYSTALS AND WHISKERS OF BI2SR2CACU2O8 BYSTEP-COOLING METHOD

Single crystals of large surface area with dimensions of 10 X 3 X 0.2 mm3 have been grown from excess CuO flux by adopting a step-cooling me thod. Crystals have also been grown from a stoichiometric melt and are thicker and smaller in size (2 x 1.5 x 0.5 mm3). Laue and powder X-ra y diffraction studies confirm the single crystallinity and orthorhombi c structure of the crystals, respectively. Single crystalline whiskers of length 4-6 mm, which are highly deficient in Sr and Ca, and platel et crystals of the Ca-free phase have also been observed for excess Cu O flux. AC susceptibility studies show superconducting transition of a bout 82 and 78 K for crystals grown from CuO flux and stoichiometric m elt, respectively.