Approximant phase of an icosahedral quasicrystal in a boron-carbon semiconducting system

The possibility of a semiconducting quasicrystal in boron-rich solids made of ${\mathrm{B}}_{12}$ icosahedra is investigated. On the basis of crystallographic data and a molecular-orbital calculation, we predict the existence of a semiconducting quasicrystal, based on α-rhombohedral units of boron icosahedra, and its boron-carbon composition. We have experimentally discovered a new 1/0-1/0-0/1 orthorhombic approximant phase of an icosahedral quasicrystal by annealing amorphous phase ${\mathrm{B}}_{100\mathrm{-}\mathit{x}}$ ${\mathrm{C}}_{\mathit{x}}$ (x=3, 5, 7) above 1200 °C for 10 min. It must be a semiconductor like other boron-rich compounds.