Abstract
The thermal diffusivity (α) and the conductivity (κ) of Bi-2223 sintered material was measured between 12 and 200K under an identical experimental setup using a closed cycle helium refrigerator. The electronic contribution to the thermal conductivity was calculated by Wiedemann-Franz law above the critical temperature (Tc) and by Kadanoff's expression below Tc, respectively. The electronic component was substracted from the total thermal conductivity in order to derive the phonon thermal conductivity. The phonon thermal conductivity was analyzed using the theory by Tewordt & Wölkhausen. The contributions of phonons to α were separated out by use of the simultaneously obtained κ data.
