Abstract
We found that an Al-Si-Ru cubic quasicrystalline approximant has a semiconducting band structure by performing an orbital analysis based on density functional theory. These semiconducting transport properties have been confirmed in an experimentally synthesized sample. The temperature dependences of the electrical conductivity and the Seebeck coefficient were consistent with the trends of an intrinsic semiconductor with a band gap of $0.15\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ above $350\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The lattice thermal conductivity had a low value of approximately $1.0\phantom{\rule{0.28em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ above $400\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, which is close to the theoretical minimum.
Highlights
Since the discovery of the quasicrystal (QC) in 1984 [1], many of the unique properties of QCs have been revealed, including their crystal structures [2] and electrical properties [3]
The performance of a TE material can be evaluated using the dimensionless figure of merit zT = S2σ T /(κel + κlat ), where S, σ, T, κel, and κlat are the Seebeck coefficient, the electrical conductivity, the absolute temperature, the electronic thermal conductivity, and the lattice thermal conductivity, respectively
While semiconductorlike properties that were attributed to a combination of the pseudogap in the density of states (DOS) and electronic weak localization were previously reported in some aluminum–transition metal (Al-TM) QCs [6,7,8,9,10] and quasicrystalline approximants (QCAs) [10,11], a finite band gap has yet to be observed experimentally in these materials to date
Summary
Since the discovery of the quasicrystal (QC) in 1984 [1], many of the unique properties of QCs have been revealed, including their crystal structures [2] and electrical properties [3].
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