GROWTH, TWIN AND DOMAIN-STRUCTURE STUDIES OF SUPERCONDUCTING BI2SR2CA1-XYXCU2O8-CRYSTALS(DELTA SINGLE)

Single crystals of superconducting Bi2Sr2Ca1-xYxCu2O8+delta (x=0.0-0.2 5) have been grown by spontaneous nucleation technique from stoichiome tric melt composition. The effect of yttrium on the growth as well as on the superconducting properties has been studied. The variation of l attice parameters with Y concentration has also been studied by powder X-ray diffraction analysis. Extensive twinning has been observed on b oth undoped and less Y doped (x=0.053) crystals and has been correlate d to the c/a ratio. Undoped crystals show a T(c) value of about 84 K. The T(c) value of doped crystals increases with increase in Y concentr ation, reaches a maximum (94 K) for x=0.156 and drops rapidly. The var iation of crystal thickness with Y concentration and the growth featur es are also discussed.