Chemistry of high-temperature superconductivity in YBa2Cu3O7

Experiments of chemical substitution in positions Y, Ba, Cu and O (alloying of K, Zn) to detect crystallochemical correlations of composition and properties of the YBa2Cu3O7-type superconductors are carried out. The supposition that existence of one-dimensional conducting chains relates to the Tc high values observed is confirmed; properties of a superconductor are shown to be sensitive to a mixed valence state of copper in chains. Consideration of a function and a contribution of two-dimensional planar part of the structure has led to the conclusion that for this structural element electron properties are more important than conducting ones. Occurrence of superconductivity in exciton mechanism agrees completely with the representations about high-temperature superconductors considered. 14 refs.; 1 fig