A Study on Thermoelectric Power and Electrical Properties of Bi-2223 Superconductors Sintered for Different Time Periods

Structure examination, resistivity, and thermopower measurements were made on samples of Bi_1.75Pb_0.35 Sr₂Ca₂Cu₃O _y sintered for different time periods. Thermoelectric power of all samples was found to be positive and changes slightly with sintering time prolongation. The normal state resistivity was analyzed using only the equation ρ _n =ρ(0)+aT which was found to be satisfactory. The superconducting fluctuation behavior has been investigated using the Aslamazov and Larkin (AL), Lawrence and Doniach (LD), and Varlamov and Livanov (VL) models. In agreement with the theoretical prediction, the ln (Δσ/σ ₃₀₀)−ln (ε) plots exhibited three different regions, namely critical, mean field, and short wave fluctuation regions. Some parameters such as critical exponents, zero temperature coherence length ζ(0), the interlayer spacing d, the interlayer coupling ν, and the Fermi energy E _F have been estimated. The effect of sintering time on such estimated parameters has been studied. The critical exponent λ values have indicated dimensionality cross-over from 2D to 3D for all the investigated samples.