Interaction of YBa$_2$Cu$_3$O$_{6.8}$ with atmospheric moisture during low-temperature annealing

The interaction of YBa$_2$Cu$_3$O$_{6.8}$ (123) with water vapors at $T$ = 200$^\circ$C and the water influence on the structure and electrophysical properties of the compound have been studied using Raman spectroscopy, magnetometry, and X-ray diffraction. It has been found that the penetration of water into the 123 structure leads to its transition to a hydride-oxyhydroxide H$_{2x-z}$YBa$_2$Cu$_3$O$_{y+x-z}$(OH)$_z$, containing fragments of the 124-type structure and exhibiting the spectrum of two-magnon scattering characteristic of antiferromagnetic 123 á compositions; in this case, the superconducting properties of the material as a whole are conserved. After short-time recovery annealing and subsequent oxidation, the water is removed from the compound structure, which leads to the disappearance of the spectrum of spin fluctuations. A possible mechanism of change in the 123 structure upon hydrogen and water intercalation has been discussed.