Percolation and electronic properties of superconducting (YBa2Cu3O7-δ)1-xAgx ceramics and thick films

The authors present the percolation and electronic properties of (Y1Ba2Cu3O7-δ)1-xAgx compounds in which silver fills the intergranular space without reducing Tc, which remains at 92±1 K. Normal-state resistivity is decreased by up to two orders of magnitude when adding up to 50 wt.% Ag (Tc=87 K), and samples exhibit improved contact resistance, better mechanical properties, and resistance to water. They analyzed the percolation properties of these compounds and found that the critical indices t, s are in agreement with percolation theory, but pc is higher than expected, probably due to the effect of holes. The Jc estimated from magnetization reaches 5·104 A/cm2 (at T=4.2 K, H=0) and shows enhancement of 15-50% by addition of ~10 wt.% Ag, which exists also in samples having a higher Jc due to preparation conditions (temperature). They present preliminary results on the 2D percolation problem in (Y1Ba2Cu3O7-δ)1-xAgx samples, obtained by preparing Y1Ba2Cu3O7-δ thick films using the spin-on technique. Preliminary results show good adhesion, but a reduced Tc of Y1Ba2Cu3O7-δ films compared with bulk samples