Thermal conductivity of the Al-based quasicrystals and approximants

At high temperatures above 200 K, a significant increase in thermal conductivity (kappa) was observed for the M-based icosahedral quasicrystals and their corresponding approximants. By comparing the measured kappa of the Al-Re-Si 1/1-cubic approximants with their electronic density of states at the Fermi level (epsilon(F)) determined by the low temperature specific heat measurements, we found that the increase in kappa at high temperature was most pronounced when epsilon(F) is located at the bottom of the pseudogap. This fact indicates that the large increase in kappa is not brought about by the lattice but by the conduction electrons in associated with the narrow pseudogap at epsilon(F). It is also found that the behavior of kappa at high temperature is well accounted for in terms of the bipolar diffusion effect of conduction electrons that is generally employed to analyze kappa of the narrow-gap semiconductors and semimetals.