A Study of the Heat Conduction of Superconductors : Measurements and Mechanism of the Thermal Conductivities of High-T_c Oxide Superconductors

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We have measured the thermal conductivities and electrical resistivities of Y_1Ba_2Cu_3O_<7-y>, Er_1Ba_2Cu_3O_<7-y> and Bi_1Sr_1Ca_1Cu_2O_y compounds using the steady-state comparative method and conventional four-probe method. Below the transition temperature, T_c, the thermal conductivities had strikingly large values and a maximum value. By applying the Wiedemann-Franz law, λR/T=L_0, with the electrical resistivity data at T_c, the phonon-thermal conductivities were found to predominate in those superconductors. The normalizations of the measured thermal conductivities of those superconductors with respect to λ_C, critical thermal conductivity, show that the temperature dependence of the thermal conductivity of Y_1Ba_2Cu_3O_<7-y> is similar to the dependence of La_<1.8>Sr_<0.2>Cu_1O_<4-y>, Er_1Ba_2Cu_3O_<7-y> and Bi_1Sr_1Ca_1Cu_2O_y compounds. Most of the normalized thermal conductivities agree with our theory, λ_s=2ξ^2・λ_n/(1+ξ^4), in which the value n of the phonon thermal conductivity in the form λ_n=ξ^n in the normal conducting state is between -1 and -1.5 below T_c.
一般社団法人日本機械学会の論文
1991-08-15