Thermal Conductivity and Thermoelectric Power of Vanadium-Substituted Bi-Based (2223) High-T c Superconductor as a Function of Temperature

Abstract

Superconducting samples with nominal composition Bi1.3V0.3Pb0.4Sr2Ca2Cu3Oδ are prepared by the solid state reaction method. The samples are characterized by X-ray diffraction, scanning electron microscopy, DC electrical resistivity, critical current density, AC magnetic susceptibility, thermal conductivity and thermoelectric measurements. The room temperature X-ray diffraction pattern of the sample indicated the presence of large amount of Bi-(2223) phase along with minor amount of Bi-(2212) phase. The standard four-probe technique is applied to measure DC electrical resistivity in the temperature range from 300 to 77 K. The onset temperature Tc (onset) and zero resistivity critical temperature Tc (R=0) are found to be 112±1 K and 106±1 K, respectively. The low field AC magnetic susceptibility is also measured as a function of temperature. Thermal conductivity and thermoelectric power of large disc-shaped cylindrical samples are measured as a function of temperature from 300 to 77 K. The increase in thermal conductivity is observed below and above Tc (R=0). The estimation of the resistivity change due to scattering by phonons and impurities has been discussed.