Superconductor-semiconductor-superconductor junction network in bulk polycrystalline composites Y3/4Lu1/4Ba2Cu3O7+Cu1-xLixO

Bulk Y3/4Lu1/4Ba2Cu3O7 + Cu1-xLixO composites with x = 0, 0.003 and 0.06 an d varied volume content of Cu1-xLixO have been prepared. Analysis of the tr ansport properties of the composites has shown that they can be represented as a network of superconductor-semiconductor-superconductor (S-Sm-S) weak links. The dependence of the critical current density on the normal resista nce for the composites studied shows a behaviour similar to that for single Josephson junctions. The experimental temperature dependences of the criti cal current are qualitatively described in terms of a theory of S-Sm-S junc tions that takes into account the Andreev reflection of carriers from the S -Sm and Sm-S interfaces.