Abstract
Thermal conductivity (κ) of the Al82.6− x Mn17.4Si x and Al82.6− x Re17.4Si x 1/1-cubic approximants was investigated with varying Si concentration x over a wide temperature range from 2 K to 300 K. Behaviors in κ observed for these 1/1-cubic approximants were essentially the same with those reported for the corresponding icosahedral quasicrystals; very small magnitude lower than 4.5 W/m K, small contribution of electrons, and possession of a local maximum and a local minimum around 30 ∼ 50 K and 100 ∼ 200 K, respectively. By analyzing measured κ in terms of local atomic structure, we revealed that the lattice thermal conductivity is greatly reduced by combination of small group velocity of phonons and enhanced umklapp process of phonon-scattering. Those characteristics were caused by large lattice constant and vacancies in the structure.