Superconducting and structural properties of HTSC specimens at various heat treatments

Correlations of superconducting and structral parameters of Y-Ba-Cu-O specimens after heat treatment in air under various conditions are investigated by metallography, X-ray diffraction, X-ray spectral microanalyses and scanning-electron microscopy method. Methods for determination of parameters of an elementary cell and a substructure in compounds with low symmetry of a crystal lattice are developed. It is established that variation of heat treatment conditions permits to change superconducting and structural properties of HTSC, optimal conditions of heat treatment are determined. Critical parameters, phase composition, parameters of elememtary cell and substructure, as well as microhardness change themselfves consistently when conditions of heat treatment are deviated from optimal ones, and the width of a superconducting transformation is proportional to microdistortions