Bulk superconductivity was observed in the new system (In xPb0.75-xCu0.25)Sr2(Ca 0.5Y0.5)Cu2 O7-δ. An increase in indium doping, 0≤x≤0.2, into the Pb sites results in an increase in the superconducting transition temperature Tc from 45 K for x=0 to 60 K for x=0.2. For nominal compositions x≳0.2, a decrease in Tc was observed, and an increase in the concentration of an impurity phase. From the results of the x-ray diffraction and energy- dispersive spectrometry, we identify the phase responsible for the superconductivity to be [In 0.06(1)Pb0.69(1)Cu0.25]Sr 1.99(7)[Ca0.47(1)Y 0.53(2)]Cu2O 7-δ; this phase resulted from the synthesis of a sample of nominal composition (In0.2Pb0.55Cu0.25)Sr 2(Ca0.5Y0.5)Cu2 O 7-δ.
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