Peculiarities in the behavior of thermal conductivity, thermal diffusivity, and specific heat of high-temperature superconductors near T c

The thermal conductivity of the same YBa2Cu3O7−δ single crystal is measured for the first time both in the ab plane (κab), and in the direction of the c-axis of the crystal (κc) in the temperature range 4–300 K. No anomalies typical of high-Tc superconductors near Tc and below due to the electron–phonon interaction are observed in the κc(T) dependence. Anomalies are observed in the thermal conductivity of Ag-doped yttrium ceramics near Tc and attributed to the effect of superconducting fluctuations.