Annealing Time Effect Fluctuation Induced Excess Conductivity in Bi (Pb):2223 Superconductors

Abstract

We report here on the effect of annealing time, in air and at 800°C for time periods of (6-30 h), on the fluctuation induced excess conductivity ∆σ in Bi2-xPbx: 2223 superconductors with various x values. The logarithmic plots of ∆σ and the reduced temperature e reveal three different exponents corresponding to two different crossover temperatures in the slope of each plot. The first exponent in the normal region is at a temperature of (Tc^(mf) ＜＜ T ＜ 2Tc ^(mf) ) and its values are close 2.5, in which the order parameter dimensionality (OPD) is not 0D. The second exponent is at a temperature of T ＞ Tc^(mf) , and its values are close to 1, in which the OPD is 2D. The third exponent is in the critical-field region at a temperature of (Tc ＜ T ≤ Tc^(mf)), and its values are close to 0.5, in which the OPD is 3D. Furthermore, the interlayer coupling J, Ginzburg-Landau coherence length ζc(0), temperature width (To-T^c(mf)), and resistivity slope (dp/dT) are also calculated for the two examined samples, and their values are affected by changing both the annealing time and Pb content. Our results are discussed in terms of the correlation between the carrier concentration and volume fraction of the high Tc phase for the considered samples.