Investigation of properties of metal oxides in the superconducting and normal states

Data are presented of an X-ray phase analysis of the superconducting compounds in the RE-Ba-Cu-O system where RE is yttrium and all the rare earth elements except promethium. The correlation between the critical temperature Tc of the compounds and the parameters of the unit cell and phase composition of the specimens is investigated. The electrophysical and magnetic properties of the specimens are studied in a broad range of magnetic field strength (up to 500 kOe) and temperature. Such experimental data as the correlation between Tc and the magnitude of the rhombic distortion of the crystal structure, the weak effect of the magnetic moment of RE on Tc, the high values of the second critical field Hc2(T) and the linear variation of the electric resistance for T>Tc are analyzed. The analysis indicates that the copperoxygen chains play an important role in the formation of the superconducting state in REBa2Cu3O7-x compounds