Temperature dependence of thermal and electrical conductivity of Bi-based high-Tc (2 2 2 3) superconductor

Superconducting samples with nominal composition Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_δ were prepared by the conventional solid-state reaction technique. The samples have been characterized by X-ray diffraction, dc electrical resistivity, ac magnetic susceptibility and thermal conductivity. The X-ray diffraction studies were done at room temperature and the lattice constants of the material were determined by indexing all the peaks. All the above measurements show that, there exists two phases i.e. high-T_c (2 2 2 3) and low-T_c (2 2 1 2). The information obtained from dc electrical resistivity data agrees with ac magnetic susceptibility measurements. The onset temperature T_c (onset) and zero resistivity temperature T_c (R = 0) of the samples remains within the temperature 120 ± 1 K and 103 ± 1 K. Thermal conductivity has been measured with a transient plane source (TPS) technique in the temperature range 77–300 K. The estimation of the electrical resistivity change due to scattering by phonons and impurities has been discussed. An increase in thermal conductivity is observed above and below T_c (R = 0). The electron–phonon scattering time, phonon-limited mobility and the size of the electron–phonon constant are also calculated. Wiedemann–Franz law is applied to gain prediction about the magnitude of electronic and phonon contribution to the total thermal conductivity of the samples. It is observed that heat is mainly conducted by the phonons in this system.