Study on the Replacement of Oxygen by Fluorine in Y-Ba-Cu-O Superconductors

In this paper, several samples with different amount of fluorine of Y-Ba-Cu-（O,F） superconductors have been synthesised directly with CuF₂ as one of the components. The main properties of these supperconductors are always better than those without fluorine. X-ray diffractions show that these samples are without peaks of fluoride or oxide. This reveals that F^- has entered into 123 phase in crystal lattice. Infrared and paramagnetic resonance spectra support this conclusion. The constants of lattice are a=3.8250Å, b=3.8969Å and c=11.7008Å, while those of Y-Ba-Cu-O are a=3.8224Å,b=3.8910Å and c=11.6848Å, The effect of fluorine on superconductivity is also disscussed.