Annealing Studies of Re Doped AlPdMn Quasicrystals
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Annealing Studies of Re Doped AlPdMn Quasicrystals Donny W. Winkler1, Terry M. Tritt1,2, Robert Gagnon3, and J. Strom-Olsen3 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 2 Materials Science and Engineering Department, Clemson University, Clemson, SC 29634 3 Department of Physics and Astronomy, McGill University, Montreal, Canada 1
ABSTRACT Quasicrystals have properties associated with both crystalline and amorphous materials. These properties appear to be sensitive to both composition and annealing conditions. Therefore, it is important to investigate the influence of the microstructure on the electrical and thermal transport properties of quasicrystals. AlPdMn quasicrystal samples were prepared with various levels of Re substituted for the Mn (Al70Pd20Mn10-XReX) and then subjected to different annealing conditions. Electrical resistivity, thermopower and thermal conductivity were measured on each as grown and annealed sample over a broad range of temperature, 10 K < T < 300 K. The relationship between the electrical and thermal transport properties and microstructure will be presented and discussed.
INTRODUCTION Quasiperiodic crystals (or quasicrystals) which were discovered in 1984 by Shechtman, Blech, Gratias and Chan [1], display a “forbidden” 5, 8, 10 or 12-fold symmetry [2,3,4]. They have long-range positional order and lack long-range translational or rotational order. The longrange positional order is shown by the sharp Bragg diffraction peaks. Quasicrystals possess properties associated with both amorpous materials and crystals [5,6]. Both AlPdMn and AlPdRe are icosahedral phase quasicrystals. The electrical and thermal transport has been well studied in both systems.[7, 8] As discussed below, the transport appears to be governed by different mechanisms in the two systems. Both systems have a low thermal conductivity (λ < 3 W m-1 K-1) and a relatively large positive thermopower. The electrical resistivity in the AlPdRe system is significantly higher (∼ 5.3 mΩ cm) than the AlPdMn system. Electrical resistivity, ρ, in the AlPdMn system increases with temperature in the range of 10 K < T < 70 K and then it begins to decrease with further increase in temperature. The room temperature value of electrical resistivity is 1.7 mΩ cm for the Al70Pd20Mn10 system. Electrical transport in the AlPdMn system can be explained by weak localization and electron-electron interactions.[9] The thermopower, α, for the Al70Pd20Mn10 system is large and positive, α ∼ 65 µV/K at room temperature.[10] The thermopower increases almost linearly with increasing temperature. The thermal conductivity, λ, of AlPdMn exhibits a small peak at low temperatures. This peak is thought to be due to changes in lattice or phonon scattering. The lattice contribution is observed to saturate at temperatures just above the low temperature peak. The electronic contribution governs the temperature dependence of the thermal conductivity at high temperatures. Al70Pd20Mn10 has a thermal conductivity of approximately 2 W m-1 K-
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