Thermal conductivity of the Al 82.6- x Mn 17.4 Si x and Al 82.6- x Re 17.4 Si x 1/1-cubic approximants.

Thermal conductivity ( ? ) of the Al 82.6- x Mn 17.4 Si x and Al 82.6- x Re 17.4 Si 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 ? 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 ? 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. [ABSTRACT FROM AUTHOR]