Electrical transport and superconductivity in YBa2Cu3O7−δ -YBa2HfO5.5 percolation system

Abstract

Percolation behavior of the normal state resistivity and superconductivity of YBa2Cu3O7−δ-YBa2HfO5.5 composites has been studied by x-ray diffraction and temperature- resistivity measurements. No detectable chemical reactivity was observed between YBa2Cu3O7−δ and a ceramic insulator YBa2HfO5.5 even when the two materials were mixed thoroughly and sintered at 1020 °C. Normal state and superconducting percolation threshold values are ≊23 vol % of YBa2Cu3O7−δ in the composite. The values obtained for the critical exponents describing the normal state transport behavior of the system matched with theoretically expected values for an ideal conductor-insulator percolation system. The implications are discussed.