New approximant crystals of decagonal B–Mg–Ru quasicrystal

Abstract

We have discovered four new approximant phases of the B–Mg–Ru decagonal quasicrystal. Six phases were observed in electron diffraction patterns of B–Mg–Ru alloys prepared at 1673 K from B_2xMg_(1-x)Ru_2(1-x) (x = 0.44–0.48). Two of them are known, B₄Mg₂Ru₅ and B₁₁Mg₅Ru₁₃, and the other four are new approximant phases. Their lattice parameters range from a = 0.84 nm to 8.5 nm; some of them can be described with the Fibonacci sequence. We suggest tiling models of these approximants using two subunits of B₄Mg₂Ru₅ and B₁₁Mg₅Ru₁₃, ‘hexagon’ and ‘boat’.

Acknowledgment

We are grateful to Mr. T. Itoh for kind guidance and technical support to use TEM at Institute of Engineering Innovation, the University of Tokyo.