Superconductivity of La2−x Sr x CuO4 with high strontium concentration by sulphur doping

The effects of sulphur substitution for oxygen on the structure and properties of nonsuperconducting La_2–xSr_xCuO₄, where x=0.26 and 0.30, have been studied. In La_2–xSr_xCuO _4–y-S_y, the sulphur-doped samples exhibit superconducting transition at 37–39 K and a larger Meissner effect than undoped samples. It was found that the superconductivity of La_2–xSr_xCuO_4–yS_y is apparently determined by the value of x–y and the strontium concentration region in which La_2–xSr_xCuO₄ shows superconductivity shifts to higher strontium concentrations with sulphur doping.