Fluorine effect on superconducting properties of compound Y Ba2 Cu3 O7-y

Complex studies are made on yttrium compounds with the fluorine contents 0<x<1.5. The studies led to finding the Knight shift at the 19 F nuclei, which may be a reliable indication of the fluorine presence in the crystalline lattice of the yttrium compound. The fluorine was introduced following the technique of solid phase diffusion with substitution Y F3 for Y2 O3. Three samples of multiphase yttrium compounds showed metastable superconducting state at ∼ 240 K