Morphology and characterization studies of Y doped Bi-2212 single crystals

Superconducting Bi-2212 single crystals of nominal composition Bi2.2Sr1.9CaCu2O8, B2.1Y0.1Sr1.9CaCu2O8 and Bi2.2Sr1.9Ca0.9Y0.1Cu2O8 have been grown by flux method using a conical shaped Al2O3 crucible. Effect of Y doping on the crystal morphology has been studied. From the X-ray diffraction studies, the cell parameters were calculated. AC susceptibility showed that Y doping gives rise to highest T-c,T-onset at 92 K and the effect of annealing was also studied. The crystal composition at different places of the crucible and the Al incorporation were studied. The Sr/Ca ratio has been correlated with Y substitution. Chemical etching was also carried out on the grown crystals in order to reveal the nature of twinning and dislocations. (C) 1997 Elsevier Science B.V.