TRANSPORT-PROPERTIES OF THE SUPERCONDUCTING YBA2CU3O7-DELTA-DYBA2SNO5.5 PERCOLATION SYSTEM

The electrical transport properties and percolation behavior of superc onducting YBa2Cu3O7-delta-DyBa2SnO5.5, a superconductor-insulator comp osite system, have been studied by X-ray diffraction and temperature-r esistivity measurements. The normal-state percolation threshold is sim ilar to 22 vol.% of YBa2Cu3O7-delta and the superconducting percolatio n threshold is similar to 30 vol.% of YBa2Cu3O7-delta in the composite . The values obtained for the critical exponents describing the normal -state transport behavior of the system agree with the theoretically e xpected values for an ideal conductor-insulator percolation system. No detectable chemical reactivity was observed between YBa2Cu3O7-delta a nd a ceramic insulator DyBa2SnO5.5, even when the two materials were m ixed thoroughly and sintered at 1020 degrees C. The implications are d iscussed.