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Structural, magnetic, and electronic properties of compounds in the series La2-xSrx CuO4-y for 0.05 </= x </= 1.1, with deltax = 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 T(c), 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 degrees C increases T(c) to 40.3 K, while annealing at the same temperature under vacuum suppresses the superconductivity. These changes in oxygen content and T(c) are reversible.
Tarascon et al. (Fri,) studied this question.