Thermal Conductivity and Thermoelectric Power of Yb-Substituted Bi-2212 Superconductor

H Gündoğmuş,A Sotelo,B Özçelik,M A Madre

doi:10.1088/1742-6596/667/1/012001

Abstract

In the present study, Bi2Sr2CaCu2-xYbxO8+y where x = 0.0, 0.05, 0.1 and 0.25, superconductor materials were textured using the Laser Floating Zone technique. After annealing the as-grown materials, they were characterized by thermal conductivity (κ-T), thermoelectric power (S-T), and electrical resistivity (R-T) measurements performed from room temperature down to 20 K. The thermoelectric power is positive in all cases and is found to increase with decreasing temperature, reaching the maximum value (peak) around the samples TC values and dropping rapidly to zero below TC. Electrical resistivity measurements show a slight decrease of TC when Yb substitution is raised. In spite of this effect, TC values are higher than 90 K in all cases. On the other hand, Yb substitution also decreases thermal conductivity, compared with the undoped samples.

Highlights

Since Bi-based superconductors Bi2Sr2Can−1CunOx (n = 1, 2, 3) were discovered by Maeda et al [1] many substitutions have been made in BSCCO system in order to improve their physical and magnetic properties [2,3,4,5,6,7,8,9,10,11,12,13,14]
The thermoelectric properties of BSCCO have been investigated by many research groups [18,19,20,21,22,23]
In order to identify the present phases, powder X-ray diffraction patterns of the materials were recorded at room temperature using a Rigaku D/max-B powder diffract meter system working with CuKα radiation and a constant scan rate between 2θ= 3-60o

Summary

Introduction

The studies of transport properties, such as electrical resistivity, thermoelectric power (S) and thermal conductivity (κ), are important for exploring the conduction mechanism and the nature of charge carriers. Negative values of the thermoelectric power indicates the effect of two types of charge carriers, i.e. holes and electrons, respectively. The material preparation techniques for the BSCCO systems play a crucial role. Laser Floating Zone Melting (LFZ) technique is one of the most reliable methods to texture these bulk superconductor samples [24].

Results

Conclusion