Proximity effect in bulk LaBa2Cu3O7-y samples with Ag additions

Bulk LaBa2Cu3O(7-y) samples with different Ag additions were investigated. II was shown that Ag does not enter the crystallographic structure of the s uperconductor and segregates on the grain boundary region. Current path in these samples occurs through the proximity-connected grains, and this was c onfirmed from the temperature dependence of the critical current density an d mutual inductance. By using the theory developed for the thin-film struct ures, we conclude that growing of the Ag content increased the effective cr oss-section and the normal metal thickness. The effective cross-section pre vails at low concentration, increasing the current. The normal metal thickn ess dominates at higher concentration, leading to saturation or even loweri ng of the critical current.