Thermoelectric Properties of Al–Ga–Pd–Re Icosahedral Quasicrystals

Abstract

Various compositions of Al–Ga–Pd–Re icosahedral quasicrystals (QCs) were synthesized using arc-melting and annealing methods, and their thermoelectric properties were investigated. With the same trend in the Seebeck coefficient as Al–Pd–Mn and Al–Pd–Re QCs, the Al–Ga–Pd–Re QC has a similar pseudogap electronic structure near the Fermi level. More particularly, we found that a sample with a nominal composition of Al₆₆Ga₄Pd₂₁Re₉ exhibited a higher Seebeck coefficient of 90 µV K⁻¹ at 373 K, and is thus a highly efficient thermoelectric material. This dense sample, having neither cracks nor pores, shows a 1.5 times higher dimensionless figure of merit ZT of 0.18 compared with sintered Al₇₁Pd₂₀Re₉. ZT enhancement through Ga substitution for Al is enabled through an increase in both electrical conductivity and Seebeck coefficient, and a decrease in phonon thermal conductivity. This behavior is discussed in terms of the precipitation of metallic secondary phases and the “weakly bonded rigid heavy clusters (WBRHCs)” scheme applicable to cluster-based solids including quasicrystals.