Effect of antimony addition on the temperature dependence of thermal conductivity of (Bi_0.8Pb_0.2-ySb_y)₂Sr₂Ca₂Cu₃O_x superconductors

Abstract

Temperature dependence of thermal conductivity (K) between 10 and 150K of (Bi_0.8Pb_0.2-ySb_y)₂Sr₂Ca₂Cu₃O_x superconducting pellets with y=0.00, 0.04 and 0.08 are reported. The superconducting transition temperature of (Bi_0.8Pb_0.2-ySb_y)₂Sr₂Ca₂Cu₃O_x decreases slightly as Sb concentration increases from 0 to 0.08. But its effect on thermal conductivity seems to be more pronounced. All the typical features of [ K vs T ] behavior for high T_c ceramic superconductors (viz., sharp upturn close to T_c, appearance of a broad peak below T_c etc.) are also observed in Sb added pellets. It appears that while Sb addition does not influence the temperature corresponding to thermal conductivity maximum, it reduces the absolute magnitude of K significantly over the entire measured temperature range. Our data shows the dominance of phonon contribution to total thermal conductivity, compared to charge carrier contribution. Integral expression for thermal conductivity of high T_c superconductors deduced by Tewordt and Wolkhausen explains fairly well our experimental results. Our analysis indicates a contribution of longitudinal acoustic phonons to electron- phonon coupling constant, which falls within the weak coupling region. It also shows that with increasing Sb content in (Bi_0.8Pb_0.24Sb_y)₂Sr₂Ca₂Cu₃O_x, phonons are more dominantly scattered by sheet like faults.