Thermal Conductivity and Thermoelectric Power of Potassium and Sodium-Substituted Bi-2212 Superconductor Prepared by PEI Technique

Abstract

In the present study, thermal conductivity (κ-T), thermoelectric power (S-T), and figure of merit (ZT) measurements from room temperature down to 20 K of polycrystalline Bi 2 Sr 2 Ca 1-x Na x Cu 2 O 8+y and Bi 2 Sr 2 Ca 1-x K x Cu 2 O 8+y superconductors prepared by a polymer solution technique using polyethyleneimine, PEI, have been carried out. The thermoelectric power, S(T), of samples have both negative (at high T) and positive values (at low T), and are found to increase with decreasing temperature, reaching their maximum values (peaks) around their Tc values and droping rapidly to zero below Tc. Na and K substitutions also have a considerable effect on the thermal conductivity, κ. Namely, with increasing Na concentration the magnitude of κ is decreased, but for the K substitution, the magnitude of κ is drastically increased for x=0.75.