GROWTH AND ANISOTROPIC RESISTIVITY OF Bi2Sr2CaCu2Oy SINGLE CRYSTALS WITH ZERO RESISTIVITY AT 90 K

Abstract

A Bi2Sr2CaCu2Oy single crystal with zero resistivity at 90 K was grown by self-flux method. The diffraction of TEM and X-ray showed that the crystals were in “2212” phase with c=3.07 nm. Diamagnetism appeared at 91.5 K. The anisotropic resistivity of the crystal has been measured using the Montgomery technique. The superconducting transition onset in resistivity occurred at about 95 K and zero resistivity at 90 K. The resistivity showed strong anisotropic characteristics, with typical metallic behavior above 122 K and a semiconducting-like temperature dependence before superconducting transition in the a-b plane, which is quite different from previous results. The resistivity in the c-direction showed semiconducting-like temperature dependence, like other high Tc oxide superconductors but only above 122 K. ρcT versus T2 could be quite well represented by a linear relation. At present, it is difficult to determine the temperature dependence of resistivity in-plane from data analysis. The structure instability may be responsible for the negative temperature dependence of resistivity below 122 K.