Structural peculiarities of Bi, Pb-2223/Ag composites annealed in an [N.sub.2]-[O.sub.2] atmosphere

-X-ray diffraction analysis, transmission and scanning electron microscopy, and electron microprobe analysis were used to study Bi,Pb-2223/Ag composites annealed in a low-oxygen atmosphere (7.5% [O.sub.2] + 92.5% [N.sub.2]). The ceramics was found to be characterized by some nonuniformity in the distribution of all the components. Two structural peculiarities of the 2223 phase were found. These are the existence of atomic displacement waves, which are related to the oxygen deficiency or nitrogen substitution for oxygen, and a more intense Ag penetration into the ceramics, which results from the annealing in the [O.sub.2]-[N.sub.2] atmosphere at a pressure of 10 atm. The unstable state of the lattice characterized by oxygen atomic displacement waves is due to the prolonged annealing in oxygen-depleted atmosphere. Usually, in the case of other favorable factors of the ceramics structure, the lattice instability positively affects the superconducting properties of the ceramics. Key words: HTSC composites, structure, atomic displacement waves; superconductivity