MOSSBAUER STUDIES ON HIGH-TEMPERATURE SUPERCONDUCTORS

Fe-57 Mossbauer spectroscopy as well as X-ray diffractometry and DTA m easurements were used to study the preparation of YBa2(Cu(Fe-57))4O8 c uprates, the degradation of 1-2-3 type superconductor by hydrogenation and the suppression of superconductivity in a PrBa2(Cu(Fe-57))3O7-d c ompound. 1-2-3 type compounds could only be prepared instead of a 1-2- 4 one using the same or similar methods reported by Cava et al. or Poo ke et al. We have demonstrated that the change in the relative intensi ty of doublet D2 (associated with iron at five-coordinated Cu(I) site) in 1-2-3 superconductors can sensitively reflect not only the change in the oxygen content, but also the effect of hydrogenation. At hydrog enation performed by gas loading at room temperature hydrogen can rema in localized near the O(5) at the Cu(I) site, while a decrease of oxyg en content can be observed according to the degradation of the superco nductor caused by hydrogenation at 220-degrees-C. The isomer shifts, o bserved with unusual values for 1-2-3 superconductors, of doublets of the PrBa2(Cu(Fe-57))3O7-d material were associated with the mechanism of suppression of superconductivity in the Pr-containing 1-2-3 compoun d.