A COMPARATIVE XPS STUDY OF BI2SR2CACU2O8 AND BI1.6PB0.4SR2CACU2O(8) COMPOUNDS

The influence of Pb doping on the electronic structure of 2212 superco nductor was investigated by XPS. The evolution of the core level spect ra of the material components as a function of the sample treatment ha s shown that in situ heating at 450 degrees C allows to gain surface w hose properties represent well those of the bulk. From detailed analys is of the high resolution XPS spectra we have deduced that the ions ex ist as Cu-(2+epsilon+), Sr2+, Ca2+, Pb2+ and Bi3+ and that each Sr and Ca ions in the lattice crystal have two occupation sites, Sr-O layer and Ca layer. The most remarkable influence of Pb concerned the enhanc ement of the thermal stability of the superconductor, proving the prob able existence of an induced stronger interaction between Bi-O planes