EFFECT OF WEAK LINKS IN N-TYPE SUPERCONDUCTING CERAMICS

Unusual forms of resistive superconducting transition have been observ ed in some n-type cuprate ceramics. Their shape are strongly magnetic field dependent. In some cases, the transition shows a double peak beh avior : the resistivity presenting two maxima before reaching zero. Th is behavior and its change with magnetic field has been explained by a n interplay between the superconducting transition of the grains and t he Josephson temperature of the intergranular region. We present a mod el based on a self consistent medium approach which describes the vari ous behaviors one can observe in these ceramics.