Thermoelectric Properties of Icosahedral Al-Pd-(Mn or Re) Quasicrystals: Improvement of the ZT Value by Ga Substitution for Al Atoms

Abstract

We report the thermoelectric properties of polygrain icosahedral Al 71 Pd 20 Mn 9 and Al 71 Pd 20 Re 9 quasicrystals (QCs). The microstructure of polygrain (arcmelted and annealed) Al-Pd-Re QCs is highly porous. We synthesized sintered pellets of the Al 71 Pd 20 Re 9 QC by the spark plasma sintering (SPS) method, resulting in an improvement in their relative density from 65% to more than 99%. This enables direct comparison of Al 71 Pd 20 Mn 9 QCs with Al 71 Pd 20 Re 9 QCs. The maximum dimensionless figures of merit ZT were 0.18 and 0.12 for Al 71 Pd 20 Mn 9 and Al 71 Pd 20 Re 9 QCs, respectively. For further improvement of the ZT value, we substituted Ga for Al atoms in the Al 71 Pd 20 Mn 9 QC in accordance with the guiding principle of weakly bonded rigid heavy clusters (WBRHCs). The sound velocity and Debye temperature beneficially decreased with increasing Ga concentration, indicating weakening of the intercluster bond strength, as predicted for WBRHCs. The maximum ZT value was increased by a factor of 1.4 from 0.18 for the Al 71 Pd 20 Mn 9 QC to 0.26 for the Al 68 Ga 3 Pd 20 Mn 9 QC by the addition of an alloying effect to that of the WBRHCs.

Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants

“…Figure 10(c) shows the temperature dependence of ZT for Al 71 Pd 20 Mn 9 and sintered Al 71 Pd 20 Re 9 quasicrystals [55]. Note that, the composition of Al 71 Pd 20 Mn 9 shows the highest S 2 σ , which is the same situation as in the Al–Pd–Re system.…”

“…Dimensionless figure of merit ( ZT ) as a function of temperature for (a) Al 71 Pd 20 (Re 1 −  x Ru x ) 9 ( x  = 0, 0.4, 0.55, 0.7) [53], (b) Al 71 Pd 20 (Re 1 −  x Fe x ) 9 ( x  = 0, 0.2, 0.4, 0.65) [54], and (c) Al 71 Pd 20 (Mn, Re) 9 [55] quasicrystals.…”

Thermoelectric properties of Tsai-type Au–Al–RE (RE: Yb, Tm, Gd) quasicrystals and approximants

“…However, it should be addressed that σ is also contributed by carriers within such an energy range. Therefore, the present σ and S Compared with i-Al-based QC, Al-Ga-Pd-Mn QC with a highest zT (= 0.26 at 473 K) [31,32] has a temperature dependence of S 2 σ that is completely different and reaches a maximum at 473 M A N U S C R I P T…”

Effect of electron doping on thermoelectric properties for narrow-bandgap intermetallic compound RuGa2

“…2-4 Examples include clathrates 5 and skutterudites 6 for narrow-bandgap compounds. On the other hand, pseudogap compounds, such as Fe 2 VAlbased half-Heusler compounds 7 and Al-based icosahedral quasicrystals 8 , also exhibit large S 2 r values. Recently, relatively large ZT values have been reported in a series of binary semiconducting intermetallic compounds composed of transition metals and group-13 elements, such as RuAl 2 -, 9,10 RuGa 2 -, [10][11][12][13][14] and RuIn 3 -based [15][16][17] compounds.…”