Thermal and electrothermal characterization of bismuth based high-Tc superconductors

This paper investigates the relationships among macroscopic physical properties and features at atomic level for the high-Tc superconducting material with nominal composition Bi1.6Pb0.4Sr1.6Ba0.4Ca2Cu3Oy, which was prepared by a solid-state reaction method. The samples were analyzed by dc electrical resistivity, ac susceptibility, thermal transport, electrothermal conductivity and thermoelectric properties all as a function of temperature (from room down to LN2 temperature). Room temperature X-ray diffraction studies were also done. All the above measurements showed that in the samples, there exists almost a single high-Tc phase with Tc,0 ≃ 110 ± 1 K. The lattice constants of the material were determined by indexing the diffraction peaks. Samples are investigated for thermal transport properties, i.e. thermal conductivity, thermal diffusivity and heat capacity per unit volume, by an advantageous transient plane source method. Simultaneous measurement of thermal conductivity and thermal diffusivity makes it possible to estimate specific heat and the Debye temperature ΘD. Thermoelectric power (Seebeck coefficient) and electrothermal conductivity is also measured with a newly developed and calibrated apparatus. Using electrical resistivity, thermal conductivity and thermoelectric power, the Figure of merit factor was calculated.