Hydrogen effect on superconducting ceramics YBa2Cu3Oy (y=6.91 and 6.54)

Hydrogen saturation of superconducting ceramics YBa2Cu3O6.91 and YBa2Cu3O6.54 at the temperature of ∼373K and pressure of PH2=300-350 mm Hg is carried out. It is found that with increase of hydrogen concentration x=H/Y decrease of orthorhombic degree in both ceramics takes place. Superconducting transition initial temperature for YBa2Cu3O6.91Hx remained unchanged, while for YBa2Cu3O6.54Hx decrease of Tc was detected. Superconducting volume fraction Δ, defined by diamagnetic signal value, decreased with x, and superconductivity for YBa2Cu3O6.91Hx disappeared at x∼1.55, and for YBa2Cu3O6.54Hx at x∼0.62. Possible explanation of observed Δ(x) dependence due to hydrogen interaction with copper atoms in frames of solid solution is discussed