Superconductivity at 40 K in the Oxygen-Defect Perovskites La2-xSrxCuO4-y

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Science  13 Mar 1987:
Vol. 235, Issue 4794, pp. 1373-1376
DOI: 10.1126/science.235.4794.1373


Structural, magnetic, and electronic properties of compounds in the series La2-xSrx CuO4-y for 0.05 ≤ x ≤ 1.1, with δx = 0.025, were studied. Resistance, susceptibility, Meissner, and shielding measurements have revealed superconductivity among several members of the series. For x = 0.15, the transition temperature Tc, measured at the midpoint of the resistive transition, is a maximum at 39.3 K with a width of 2 K. At other compositions the transition is broader and occurs at a lower temperature. Annealing the x = 0.15 sample in oxygen at 500°C increases Tc to 40.3 K, while annealing at the same temperature under vacuum suppresses the superconductivity. These changes in oxygen content and Tc are reversible.