Electrical and percolative behavior of Sr2YSbO6–YBa2Cu3O7-δYBa2Cu3O7-δ composites

We found that a mixture of materials Sr2YSbO6 insulator with YBa2Cu3O7-δYBa2Cu3O7-δ superconductor is a system where the particles of superconductor and insulator materials are found coexisting in a composite with two well-defined separate phases. Electrical transport properties and percolation behavior have been studied by electrical resistivity measurements at room temperature on several samples of composites with different vol% of YBa2Cu3O7-δYBa2Cu3O7-δ. Resistivity measurements agree with the equation which describes the conductivity in percolation theory. However, critical exponent t=6.65t=6.65 is greater than universal value t∼2t∼2. Furthermore, there is a non-negligible conductivity below percolation threshold while it is expected to be zero in ideal percolative systems. Nevertheless, percolative behavior in this region was found and, critical exponent value s was determined to be s=0.75s=0.75 in agreement with universal value.