GROWTH OF SUPERCONDUCTING SINGLE-CRYSTAL BI-SR-CA-CU-O COMPOUNDS

Three types of Bi-Sr-Ca-Cu-O single crystals with different chemical compositions were grown from molten Bi//2O//3-SrCO//3-CaCO//3-CuO mixtures. Crystals with compositions of Bi//4//. //4(Sr//3//. //6Ca//2)Cu//4O//z and Bi//4//. //4(Sr//4//. //2Ca//1//. //4)Cu//4O//z exhibit superconductivit with T//c's above 80 K. The Bi//4//. //6(Sr//2//. //4Ca//1)Cu//2O//z crystals, however, do not show superconductivity down to 4. 2 K. These crystals have similar structures. Study of composition and X-ray analyses suggested that the ordering of perovskite-like sub-cells has a strong influence on the high-T//c superconductivity.