Fluorination of Y1Ba2Cu3O7-x by a solid state electrochemical

This paper reports on a solid state electrochemical method that has been employed to fluorinate Y1Ba2Cu3O7-x pellets of stoichiometry close to Y1Ba2Cu3O6.2 and Y1Ba2Cu3O6.9. The optimum condition for the coulometric titration of fluorine was found to be at a temperature of less than 673K and for titration into tetragonal material of low oxygen stoichiometry. A tetragonal lattice configuration s approached at high fluorination levels, regardless of the initial oxygen stoichiometry of the samples before fluorination, and the phase is more thermodynamically stable than the pure oxide. The superconducting properties of the fluorinated material were not enhanced above the maximum value of 92K measured in the pure oxide phase. However, Tc onset as high as 87K were measured in samples of the Y1Ba2Cu3O7-xFy phase of initial oxygen stoichiometry close to 7 - x = 6.9, and as high as 60K in Y1Ba2Cu3O7-xFy samples of the initial oxygen stoichiometry, 7 - x, close to 6.2