Inducing superconductivity and structural transformations by fluorination of reduced YBCO

Anion Ordering in Fluorinated La2CuO4

“…This means that part of the apical oxygen atoms in the initial La CuO is replaced by interstitial fluorine. This competing anion exchange reaction always takes place during fluorination in a closed vessel at temperatures above 300°C, as was shown previously for different superconducting oxides (13,14). The oxygen released due to anion ex-change is absorbed at the inner surface of the copper tube, forming traces of Cu O.…”

“…Recently we showed that XeF is a soft and effective fluorinating agent and may be applied for the preparation of different superconducting oxyfluorides (12)(13)(14)(15). In this paper we report the results of the fluorination of La CuO by XeF at different synthesis conditions and the structural characterization of the materials by a combination of X-ray diffraction, electron diffraction, and high resolution electron microscopy.…”

Oxyfluoride Chemistry of Layered Perovskite Compounds

“…Thus, the fluorine contents in the resultant material depend on the choice, not only of the fluorinating agent, but also the anion lattice of the precursors. For example, the fluorine contents incorporated by XeF 2 in YBa 2 Cu 3 O 7−δ increase with decreasing the oxygen deficient contents [45]. The fluorination of perovskite SrFeO 3 using PVDF yields SrFeO 2 F while the reaction of brownmillerite Sr 2 Fe 2 O 5 with F 2 gas results in the formation of two cubic phases different from SrFeO 2 F [17,46].…”

High-temperature superconductors based on complex layered copper oxyfluorides

“…Fluorination with xenon difluoride in different temperature ranges involves the following main reactions. It was demonstrated 44 that the incorporation of fluorine into the structure of complex cuprate was the major process in the case of fluorination of YBa 2 Cu 3 O 6.11 (Y123 phase) in the temperature range from 423 to 573 K YBa2Cu3O6.11 + 0.5x XeF2 YBa2Cu3O6.11Fx + 0.5x Xe.…”