Excess conductivity in the Si doped (BiPb)SrCaCuO superconducting system

Abstract The resistivity behavior above the critical temperature of the system (Bi 1.6 Pb 0.4−x Si x )Sr 2 Ca 3 Cu 4 O 12+° (0 ≤ x ≤ 0.4) and (Bi 1.6 Pb 0.4 )Sr 2 Ca 3 (Cu 1−y Si y ) 4 O 12+° (0 ≤ y ≤ 0.1250) have been studied. With the use of Aslamazov- Larkin theory, the dimensionality of the samples was determinated. The value of the critical exponent (λ ∼ 1) obtained for samples with 0 ≤ x ≤ 0.20 and 0 ≤ y ≤ 0.0625 indicates the two dimensional nature of the superconductivity. However, an increase in the exponent λ in Si-doped sample with x ≥ 0.25 and y ≥ 0.0750 has been observed. This can be interpreted as a consequence of disorder which produces inhomogeneity in the CuO 2 planes.