Nature of thermodynamic fluctuations in the electrical conductivity of Y-Ba-Cu-O pellets and tapes containing silver

Results on the temperature dependence of the electrical resistivity of single-phase silver-doped Y-Ba-Cu-O pellets and tapes, prepared by a coprecipitation technique, are presented. The excess electrical conductivity nearT>T_cis analyzed using Aslamzov-Larkin (AL) formulations. Silver addition in Y-Ba-Cu-O influences strongly the temperature range of both the 3D and 2D regions. The lower limit of the breakdown temperature of the mean-field region (x=–0.5) shifts toward higher temperatures as the concentration of Ag increases in Y-Ba-Cu-O. For samples with higher Ag contents, a third region with critical exponent x=–0.28 is seen beyond the mean-field region. This possibly indicates the appearance of a fully critical 3D region, where dynamic scaling theory applies.