J. Kurian et al., Percolation behavior of the normal-state resistivity and superconductivityof the YBa2Cu3O7-delta-Ba2GdNbO6 composite system, J SUPERCOND, 11(6), 1998, pp. 683-687
The percolation behavior of the normal-state resistivity and superconductiv
ity of the YBa2Cu3O7-delta-Ba2GdNbO6 composite system were studied by X-ray
diffraction and temperature-resistivity measurements. No detectable chemic
al reaction was observed between the YBa2Cu3O7-delta superconductor and the
ceramic insulator Ba2GdNbO6, even after severe heat treatment above 950 de
grees C. The normal-state and superconducting percolation threshold values
were found to be 17 vol.% and 30 vol.% of YBa2Cu3O7-delta respectively in t
he YBa2Cu3O7-deltaBa2GdNbO6 composite system. The values obtained for the c
ritical exponents describing the normal-state pecolation behavior of the sy
stem matched fairly well with the theoretically expected values for an idea
l metal-insulator composite system.