engleski

Anisotropy of thermal transport in decagonal aproximants

Decagonal approximant phases are structurally composed of periodically stacked planes that obey (approximant) decagonal quasiperiodic structure patterns, and they present an ideal system to study how structure peculiarities influence physical properties. In this work we present anisotropy of the heat transport coefficient of following decagonal approximant phases: Y-Al-Ni-Co, o-Al13Co4, and Al80Cr15Fe5. All three samples have common feature: their thermal conductivity (k), both total and electronic one calculated by Wiedemann-Franz law, is larger within periodic directions as compared to non-periodic ones. This is expected since structural non-periodicity introduces more structurally related phonon scattering centers (like umklapp-like processes). In the case of Y-Al-Ni-Co phase, lattice k (obeyed by subtracting electronic part from the total k) exhibits maxima for both nonperiodic and periodic crystallographic axes ; in the case of Al80Cr15Fe5 maximum is present for periodic direction only, while k of o-Al13Co4 does not exhibit maxima for any of three axes. This shows that k is defined by the nearest neighbors short-range, and not by intermediate or long-range order scale set by periodicity or qusiperiodic atomic clusters. k is analyzed in “ semi-quantitative” manner, where low temperature lattice k (<50 K) is analyzed within Debye model, while for high temperatures (> 100 K) we employ an averaged activation model of localized vibrations. References:

approximants ; thermal conductivity ; Wiedemann-Franz law

The paper was presented at the 1st International Conference on Complex Metallic Alloys and their Complexity (04.10-07.10.2009., Nancy, Francuska) as a poster by Ana Smontara. This work was supported in part by the 6th Framework EU Network of Excellence 'Complex Metallic Alloys' (Contract No. NMP3-CT-2005-500140).