Thermal conductivity and thermoelectric power of DyBaCuO bulk superconductors

The ab-plane thermal conductivity κ(T) and thermoelectric power S(T) have been investigated for DyBaCuO bulk superconductors for various contents of the Dy₂BaCuO₅ (Dy211) phase X. The absolute κ(T) value is pretty small compared with that of other REBaCuO bulks (RE ≤ Y and rare earth elements). The S(T) value above the superconducting transition temperature T_c changes from negative to positive and κ(T) slightly decreases with increasing oxygen deficiency in the DyBa ₂Cu₃O_7-δ (Dy123) superconducting phase. The point-defect-type phonon scattering due to oxygen deficiency affects the κ(T) value, but is not a main origin for the low κ(T) even for the fully oxidized DyBaCuO bulk. Another type of powerful phonon scattering centre governs the thermal transport properties in the DyBaCuO bulk.