INFLUENCE OF THE CATION SUBLATTICE ON THE GROWTH, STRUCTURE AND PROPERTIES OF SINGLE-CRYSTALS OF 123-TYPE AND 2212-TYPE HIGH-T-C SUPERCONDUCTORS

Series of 123- and 2212-type crystals were grown from non-stoichiometr ic melts and were investigated by electron-probe microanalysis (EPMA), X-ray diffraction (XRD) and optical methods. Among doped 123-type cry stals, a group of samples has been distinguished with ordered distribu tion of cations. The presence of impurities in Cu(1) sites and large r are-earth (RE) cations has been determined to cause the structure orde ring. The 123-type crystals with random and ordered cation distributio n correspond to two regions of superconductivity, when they are scaled with respect to deficiency of Cu sites. In the Bi-Pb-Sr-Ca, Y, RE-Cu- O system, series of solid solutions have been distinguished in which c hemical composition, lattice parameters and properties change continuo usly. An increase of carrier concentration at intergrowth of two isost ructural phases and the presence of regions with large deviation from stoichiometry are discussed.