The thermal conductivity of polycrystalline YBaℓCuℓOℓ superconductor from 10 K to 300 K

The steady-state longitudinal heat flow method was used to determine the thermal conductivity of polycrystalline, bulk YBa₂Cu₄O₈ over the temperature range of 10 to 300 K. YBa₂Cu₄O₈is an oxide material that exhibits superconducting properties (loss of electrical resistance and partial or complete expulsion of magnetic fields) at temperatures lower than 80 K. The measurement of thermal conductivity, γ, for this material proved to be difficult because of the physical limitations of sample size and the low thermal conductivity of the material. The electrical resistivity and thermal conductivity of YBa₂Cu₄O₈were determined and used to infer the behavior of electrons and phonons in the material.

Existing theory cannot explain some features of the experimential results. At temperature, T, below 40 K, the dependence of γ on T was relatively weak, with γ α 1; in contrast, existing theory predicts a stronger dependence, with γ α Τ₃. This result was compared to a similar material,YBa₂Cu₃O_7-x, and a similar dependence was found.