Experimental realization of a semiconducting quasicrystalline approximant in Al-Si-Ru system by band engineering

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.