Mössbauer studies on high temperature superconductors

⁵⁷Fe Mössbauer spectroscopy as well as X-ray diffractometry and DTA measurements were used to study the preparation of YBa₂(Cu(⁵⁷Fe))₄O₈ cuprates, the degradation of 1-2-3 type superconductor by hydrogenation and the suppression of superconductivity in a PrBa₂(Cu(⁵⁷Fe))₃O_7–d compound. 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 Pooke et al. We have demonstrated that the change in the relative intensity of doublet D2 (associated with iron at five-coordinated Cu(1) site) in 1-2-3 superconductors can sensitively reflect not only the change in the oxygen content, but also the effect of hydrogenation. At hydrogenation performed by gas loading at room temperature, hydrogen can remain localized near the O(5) at the Cu(1) site, while a decrease of oxygen content can be observed according to the degradation of the superconductor caused by hydrogenation at 220 °C. The isomer shifts, observed with unusual values for 1-2-3 superconductors, of doublets of the PrBa₂(Cu(⁵⁷Fe))₃O_7–d material were associated with the mechanism of suppression of superconductivity in the Pr-containing 1-2-3 compound.