Composition dependence of thermoelectric properties of AlPdRe icosahedral quasicrystals

Abstract

Observation of metal-insulator transition in Al-Pd-Re quasicrystals by x-ray absorption and photoemission spectroscopy Appl.We present the composition dependence of the Seebeck coefficient and the electrical conductivity of AlPdRe icosahedral alloys. As the concentration of transition metal ͑either Pd or Re͒ increases, the Seebeck coefficient rapidly increases. The strong composition dependence is related to the pseudogap structure in the electron density of states at the Fermi energy, and to the variation in bonding nature between Al and transition metal. Glass-like transport behavior in thermal conduction is also observed. The dimensionless thermoelectric figure of merit has a maximum value of approximately 0.1 in the temperature range from 600 to 700 K and reveals strong composition dependence.

Thermoelectric properties of Al–Pd–Re quasicrystal sintered by Spark Plasma Sintering (SPS): effect of improvement of microstructure

“…. The microstructure of annealed Al--Pd--Re quasicrystals is highly porous and contains a lot of cracks, same as previously reported papers [2,[11][12][13][14], and the relative density is low ($65%). We successfully improved the microstruc-80 Y. Takagiwa, T. Kamimura, S. Hosoi et al Figure 2 shows XRD patterns of the synthesized Al 71 Pd 20 Re 9 quasicrystals.…”

“…This secondary phase of Al 11 Re 4 may affect the electrical and thermal transport properties of the Al--Pd--Re quasicrystals. The values of electrical conductivity for Al 11 Re 4 are approximately s 373 K $ 600 (W cm) À1 and s 873 K $ 300 (W cm) À1 and exhibits negative temperature dependence [2]. Above 500 K, the observed electrical conductivity is larger than that of Al 11 Re 4 crystalline as described in the next paragraph.…”

“…The estimated volume of voids of 30% gave a reduction of conductivity of about 50%. On the other hand, the Seebeck coefficient of poly-grain samples exhibits strong composition dependence, as previously reported by Kirihara and Kimura [2]. They examined the e=a (the average valence electron number per atom) dependence of the Seebeck coefficient of various compositions of poly-grain Al--Pd--Re quasicrystals.…”

“…Some Al-based icosahedral quasicrystals such as Al--Pd--Mn [1] and Al--Pd--Re [2] exhibit semiconductor-like electron transport properties in spite of being composed of metallic elements, and they exhibit strong composition dependence of the electrical conductivity and its temperature coefficient. We have pointed out that not only the composition dependence but also the difference in the electrical properties between different alloy systems is related to the difference in the bonding nature of local atomic arrangements such as icosahedral clusters.…”

Compatibility factor of segmented thermoelectric generators based on quasicrystalline alloys

“…2 In the last few years it has been progressively realized that quasicrystals (QCs) deserve some attention as potential thermoelectric materials (TEMs), since they naturally fulfill the Slack's requirements for a material belonging to the "electronic crystal/phonon glass" class. [3][4][5][6][7] Quite interestingly, relatively high, positive thermopower values ͑+100 − 120 V K −1 ͒ have been reported for representatives of the icosahedral AlPdMn and AlPdRe families in the temperature range 300-600 K. [8][9][10] The main aim of this paper is to show that, by a judicious choice of sample's stoichiometry, 11 suitable candidates for a high temperature material, compatible with PbTe, ͑AgSbTe 2 ͒ 0.15 ͑GeTe͒ 0.85 (TAGS) or skutterudites, may be found among the AlPd͑Re, Mn͒ quasicrystalline alloys.…”