Thermal conductivity of the Al-based quasicrystals and approximants

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