B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Nauki Ave., Kharkiv 61103, Ukraine
Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
Received October 9, 2019, published online December 27, 2019
X-ray studies were performed for iron chalcogenide single crystals FeTe0.65Se0.35, which for a long time were in the air and an atmosphere of hydrogen at room and elevated temperatures. A significant effect has been established on the structural characteristics of the diffraction pattern for the impurity components of this layered tetragonal superconductor. It is shown that impurities do not alter the matrix symmetry of the tetragonal substitution solutions in the molecular state. But when the dissociation of hydrogen molecules occurs near 200 °C under the thermocatalytic effect of Fe atoms, the tetragonal lattice of the matrix becomes unstable. Symmetry is reduced against the background of an increase in the concentration of atomic hydrogen and enhancement of chemical bonds in crystals, and the density of crystals increases greatly, and an interstitial solution FeTe0.65Se0.35 + H is formed based on of an orthorhombic lattice. It is shown that the structural tetra-ortho phase transition occurs in these solutions near 200 °C.
Key words: hydrogen intercalation, iron superconductor, chalcogenides.