engleski

Thermal conductivity of Al-Cr-Fe approximant compounds

We have investigated electrical resitivity and thermal conductivity of quasicrystalline compounds of the Al-Cr-Fe system: a gamma-brass phase ( -AlCrFe) and a mixture of two orthorhombic approximants of the decagonal phase (O1/O2-AlCrFe) with properties which are are in many respects intermediate to regular metals and quasicrystals. The electrical resistivities show very weak temperature dependences and the resistivity values are in between regular metals and aluminum-based quasicrystals. Thermal conductivity data show that the electronic and lattice contributions are of comparable size. While the electronic contribution can be described by the Wiedemann-Franz law, the lattice contribution can be reproduced by a sum of a long-wavelength phonons and fracton hopping terms. At the lowest measured temperature, scattering of phonons on stacking-faults-like defects limits the heat transport. This type of defects has also been observed in the structural investigations. The results indicate that transport properties of quasicrystalline approximants are not determined by the short-range atomic order only, but are affected by both, the short-range quasiperiodic and long-range periodic atomic orders.

Al-Cr-Fe system ; quasicrystalline approximants ; thermal conductivity

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