Abstract
A series of (Cu(1)0.5Al0.5-xSx)BaSr(Nd1-yCay)Cu2O7-z superconductors have been synthesised for investigating the counterbalance effects of Al, S and Ca doping on structure and superconductivity. The results reveal that S6+ doping at Cu(1) site can stabilise the crystal structure, shorten c parameters and enhance Tc. We found that the optimum composition is (Cu(1)0.5Al0.1S0.4)BaSr(Nd0.6Ca0.4)Cu2O7-z with Tc of 80 K and c parameter of 11.54 A.