  Annealing of Bi,Pb-2223/Ag composites in (O2+N2) atmosphere at 820-780C is
believed to reduce the number of the accompanying phases, to make contacts
between crystallites closer and to increase the critical current. The goals of
this study were to reveal the changes in the 2223 lattice at annealing in the
reduced oxygen atmosphere, to elucidate the reasons of these changes and to
discuss their effect on the ceramics superconductivity. After the annealing the
transversely-polarized displacement waves of oxygen atoms in [010]2223
direction have been found in the 2223 phase by electron diffraction analysis.
These waves could appear due to the lack of oxygen in the 2223 lattice or to
the nitrogen penetration in it. As demonstrated by the X-ray photo-electron
spectroscopy and nuclear microanalysis, nitrogen does not interact with the
2223 lattice, and the oxygen index decreases to 9.67, which is lower than the
stoichiometric. Thus, the atomic displacement waves result from the lack of
oxygen in Bi-O bilayers.
