Thermoelectric properties of (α-, δ-, ζ-) Ti–Ru–B approximants for the decagonal quasicrystal

Abstract

The electronic structure and the thermoelectric properties of (α-, δ-, ζ-) Ti–Ru–B approximants related to its decagonal quasicrystal phase were investigated. The band structure calculation reveals that they form pseudogaps in the electronic density of states across the Fermi level. The samples were synthesized by arc-melting, followed by spark plasma sintering. The electrical conductivity at 373 K varies from 1600 to 4200 Ω−1 cm−1 and their temperature coefficients are negative. All measured compounds show n-type properties, judging from the sign of the Seebeck coefficient; however, the magnitudes are rather low of less than 25 μV K−1. The phonon thermal conductivity at 373 K have a range 3–5 W m−1 K−1 resulting from complex crystal structures with large unit cell volumes. The maximum dimensionless figure-of-merit of 0.008 is evaluated at 773 K for δ-Ti–Ru–B.