XPS STUDIES OF THE BI-SR-CA-CU-O CERAMICS AT TEMPERATURES NEAR T(C)

Ceramic samples of the oxide superconductor Bi2-xPbxSr2Ca2Cu3Oy with x = 0, 0.2, and 0.3 have been prepared and studied by x-ray-photoelectr on spectroscopy. A comparison of the Cu 2p, Bi 4f, and O 1s spectra of undoped and doped samples from ambient temperature down to 96 K near the critical temperature suggests the formation of dimer oxygen specie s in the superconducting state. A mechanism of charge transfer between CuO2 and BiO planes is proposed to explain this possibility, which is suggested to be related to the change of the conductivity of the cera mics.