Improved superconductivity in BiSrCaCuO single crystals by lithium doping

The authors successfully grew Li-doped Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ single crystals by a self-flux method and systematically investigated effects of the doping on the crystallographic and superconducting properties. Tlie crystal exhibited a cleaved surface perpendicular to the c-axis. The length of the c-axis increased linearly with the nominal ratio of Li to Cu in the melt, in agreement with the secondary ion mass spectroscopy (SIMS) observation that the relative amount of Cu and Li in the crystals was changed. The superconducting properties were improved by Li doping. The onset temperature of superconducting transition rose in proportion to the nominal ratio of Li, while the zero resistance temperature had a peak of 86.3 K at a ratio of 50%. Measurements of the Meissner effect implied that the behavior was bulky. The superconducting properties of the high-T/sub c/ phase were also improved by Li doping.