Samples with the nominal composition Bi2Sr2Ca1Cu2-xNixO 8+?? (x = 0.00, 0.02, 0.10, 0.20)
have been studied by X-ray photoelectron spectroseopy (XPS). From deconvolution of Bi 4f and O 1s XPS
core-level spectra, we propose that the main reason leading to the decrease of superconducting transition
temperature (Tc) with increasing Ni content, is the distortion of the Bi-2212 crystal structure by extra
oxygen being intercalated between the adjacent Bi-O layers which then affects the hole concentration (nh) of
the CuO2 planes. ?? 1998 Elsevier Science B.V. All rights reserved.
