Oxygen Behavior in the Superconductor (Bi, Pb)2Sr2Ca2Cu3Oy Phase Studied by X-Ray Photoelectron Spectroscopy

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Abstract
Samples annealed in lower and higher oxygen partial pressure than P O2 =10-2 atm show T c shift to the lower temperatures compared with the sample annealed in P O2 =10-2 atm, which shows the highest T c, 107 K. X-ray Photoelectron Spectroscopy (XPS) measurement was carried out to study the behavior of oxygen and the change of chemical environments of each ion in the high T c phase, dependent on the annealing atmosphere changes becoming the origin of these phenomena. The tendency toward increasing binding energies of Bi 4f7/2 and Cu 2p3/2 with increasing oxygen partial pressures during the heat treatments indicates that the mobile oxygens are located in the (Bi, Pb)-O and the Cu-O layers. We know that the valence of Cu moves to +3 with increasing oxygen content in the structure, and this increase of Cu valence indicates the enhancement of hole creation.