Transport properties of the superconducting YBa2Cu3O7-delta-DyBa2SnO5.5 percolation system

The electrical transport properties and percolation behavior of superconducting YBa2Cu3O7-delta-DyBa2SnO5.5, a superconductor-insulator composite system, have been studied by X-ray diffraction and temperature-resistivity measurements. The normal-state percolation threshold is similar to 22 vol.% of YBa2Cu3O7-delta and the superconducting percolation 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 expected values for an ideal conductor-insulator percolation system. No detectable chemical reactivity was observed between YBa2Cu3O7-delta and a ceramic insulator DyBa2SnO5.5, even when the two materials were mixed thoroughly and sintered at 1020 degrees C. The implications are discussed.