IMPROVED SUPERCONDUCTIVITY IN BISRCACUO SINGLE-CRYSTALS BY LITHIUM DOPING

We have successfully grown Li-doped Bi2Sr2CaCu2O(y) single crystals by a self-flux method and systematically investigated effects of the doping on the crystallographic and superconducting properties. The crystal exhibited a cleaved surface perpendicular to c-axis. The length of c-axis linearly increased with the nominal ratio of Li to Cu in the melt, coincident with the secondary ion mass spectroscopy (SIMS) observation that the relative amount of Cu and Li incorporated to the crystals was changed. The superconducting properties were improved by Li doping. The onset temperature T(c), onset of superconducting transition rose in proportion to the nominal ratio of Li, while the zero resistance temperature T(c), represented a peak of 86.3 K at the ratio of 50%. Measurements of Meissner effect implied that the behavior was bulky. Similar effects were also observed in the high-T(c) phase intergrown incidentally.