INFLUENCE OF THE ANNEALING ATMOSPHERE ON THE SUPERCONDUCTIVITY IN (PB,SR)SR2(Y.CA)CU2OY

We have prepared by solid reaction in air the Pb-based layered copper oxide of (Pb0.6Sr0.4)Sr2(Y0.5Ca0.5)Cu2Oy with T(c)(onset)=110K, which is the highest one for Pb-based superconductors to our knowledge. Ther e are two superconducting phases in the sample, a high T(c) phase with T(c)(onset)=110K and a low T(c) phase with T(c)(onset)=80K and T(c)(z ero)=43K. The low T(c) phase has (Pb,Sr)-1212 structure with a=3.822 a ngstrom and c=11.875 angstrom. The superconducting volume fraction of the low T(c) phase is about 25% at 5K, indicating bulk superconductivi ty. Magnetic measurements revealed the volume fraction of the high T(c ) phase is too low to be detected by the magnetic measurement or X-ray diffraction(XRD) analysis. The influence of the annealing atomosphere (N2, O2) on the superconductivity has been studied, which revealed th at the oxygen content and its distribution are the key points to the s uperconductivity in this material.