NEW SERIES OF OXYSULFATE SUPERCONDUCTORS (CU0.5S0.5)SR2CAN-1CUNOY (N=3-7), PREPARED AT HIGH-PRESSURE

A new series of oxysulphate superconductors, (Cu0.5S0.5)Sr2Can-1CunOy was prepared at high pressure of 6 GPa and 1250 degrees C. Five member s with n = 3-7 were obtained in bulk. They show superconductivity with T-c ranging from similar to 60 K for n = 7 to 100 K for n = 3. HRTEM and electron diffraction observation for each member indicated an orde red arrangement of Cu and S in a (Cu,S) plane resulting in a superstru cture with a(s) = 2a, b(s) = b, c(s) = 2c or a(s) = 2s, b(s) = b, c(s) = c with respect to a basic tetragonal lattice, a, b, c. Local interg rowths of phases with various n values up to 13 were also observed.