Superconductivity in (Hg0.83Cu0.17)Ba2CuO4+δ at a temperature above 120 K

The superconducting compound (Hg0.83Cu0.17)Ba2CuO4+δ is obtained by the method of solid-phase synthesis with the beginning of the transition from the paramagnetic to the diamagnetic state at a temperature of 125 K. The coordinates of the atoms, the isotropic thermal parameters and the interatomic distances were made more precise by x-ray structure analysis. In the compound (Hg0.83Cu0.17)Ba2CuO4.05 the appearance of optical generation of the second harmonic (GSH) of a YAG laser (λ =1.05 μm) was first observed at 130 K. This indicates the appearance of an acentric distribution of the electron density, which correlates with the appearance of the superconducting phase transition. It is proposed that the increase in Tc is associated with the formation of two layers [CuO2] in the average elementary cell in the case of replacement of some of the atoms of Hg by Cu and by the partial filling of the 2(f) positions by oxygen atoms.