CRYSTAL-GROWTH AND SUPERCONDUCTIVITY OF (LA,SR)(2)CUO4 WITH SRF2 AS ADDITIVE

In contrast with ceramic material, it is very difficult to prepare sin gle crystal of(La,Sr)(2)CuO4 (LSCO) with high Tc and sharp transition by flux method. The origin was possibly explained to be doping level, structure ordering, oxygen or Cu deficiencies and the contamination by the crucible materials in the crystal. At present the problem remains to be unsolved. We have carried out an extensive investigation on the relation between the growth conditions and the superconductivity of t he crystals. Recently, we reported a new route to study fluorination o f high Tc superconductors - crystal growth from high temperature solut ion with F- as additive, and found that a small amount of SrF2 could i mprove the superconducting transition temperature. Ac susceptibility m easurement showed that the transition temperature of Tc=37 K with widt h of 3 K for the as-grown crystal and Tc=38.5 K with width of 1.5 K af ter oxygenation have been reached.