High-Temperature Specific Heat of Al–Cu–Ru Icosahedral Quasicrystals and 1/1 Crystal Approximants

Tamura, Shinichi; Fukushima, Kento; Tokumoto, Yuki; Takagiwa, Yoshiki; Edagawa, Keiichi

doi:10.2320/matertrans.mt-mb2020004

Cited by 11 publications

(9 citation statements)

References 14 publications

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“…where V, B, and α are the atomic volume, the bulk modulus, and the linear thermal expansion coefficient, respectively. Although we did not perform measurements of B and Returning to the estimation of κ el , the Wiedemann-Franz law applied for pseudogap and narrow-gap compounds is found to be invalid because it assumes that the spectral conductivity varies linearly with energy [17]. The validity of the Wiedemann-Franz law was also discussed by Maciá [23].…”

Section: Resultsmentioning

confidence: 91%

“…Returning to the estimation of κ el , the Wiedemann–Franz law applied for pseudogap and narrow-gap compounds is found to be invalid because it assumes that the spectral conductivity varies linearly with energy [ 17 ]. The validity of the Wiedemann–Franz law was also discussed by Maciá [ 23 ].…”

Section: Resultsmentioning

confidence: 99%

“…The calculated κ ph as a function of temperature are shown in Figure 5 a,b. It should be noted that although the apparent increase in κ ph at high temperatures originates from conduction carriers [ 17 ], room-temperature κ ph may not be largely under- or over-estimated. We found that the increase in κ t,300K for Au-substituted samples ( Table 3 ) is attributed to an increase in κ el , as shown in Figure 4 b, probably because of an increase in the carrier concentration because the electrical conductivity increases for Au-substituted Al-Cu-Fe [ Figure 4 a].…”

Section: Resultsmentioning

confidence: 99%

“…Although the microstructure (such as defect, strain, and grain size) can also affect σ, the observed non-monotonic change in σ cannot be explained only by such extrinsic factors. Returning to the estimation of κel, the Wiedemann-Franz law applied for pseudogap and narrow-gap compounds is found to be invalid because it assumes that the spectral conductivity varies linearly with energy [17]. The validity of the Wiedemann-Franz law was also discussed by Maciá [23].…”

Section: Resultsmentioning

confidence: 99%

“…Here, we selected Au and Pt as substitution elements for Cu because of the large atomic radii, strong bond strength with Al, and a high melting point of Pt. From the experimental point of view, investigating high-temperature thermal conductivity is of great importance for controlling the unusual increase in the specific heat [15][16][17][18][19] for Al-based QCs and approximants, which provides an additional route to tune the thermoelectric [3] and thermal rectifier [12] properties.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of Thermal Conductivity for Icosahedral Al-Cu-Fe Quasicrystal through Heavy Element Substitution

et al. 2021

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Icosahedral Al-Cu-Fe quasicrystal (QC) shows moderate electrical conductivity and low thermal conductivity, and both p- and n-type conduction can be controlled by tuning the sample composition, making it potentially suited for thermoelectric materials. In this work, we investigated the effect of introducing chemical disorder through heavy element substitution on the thermal conductivity of Al-Cu-Fe QC. We substituted Au and Pt elements for Cu up to 3 at% in a composition of Al63Cu25Fe12, i.e., Al63Cu25−x(Au,Pt)xFe12 (x = 0, 1, 2, 3). The substitutions of Au and Pt for Cu reduced the phonon thermal conductivity at 300 K (κph,300K) by up to 17%. The reduction of κph,300K is attributed to a decrease in the specific heat and phonon relaxation time through heavy element substitution. We found that increasing the Pt content reduced the specific heat at high temperatures, which may be caused by the locked state of phasons. The observed glass-like low values of κph,300K (0.9–1.1 W m−1 K−1 at 300 K) for Al63Cu25−x(Au,Pt)xFe12 are close to the lower limit calculated using the Cahill model.

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Section: Resultsmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduction of Thermal Conductivity for Icosahedral Al-Cu-Fe Quasicrystal through Heavy Element Substitution

et al. 2021

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Unraveling the effects of phason strain on the thermoelectric properties in Ag-In-Yb icosahedral quasicrystals

Zhang,

Kurono,

Tokumoto

et al. 2024

Journal of Alloys and Compounds

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Three-Center Bonds in an Al–Pd–Co Quasicrystalline Approximant: Wannier Function-Based Chemical Bonding Analysis

Iwasaki,

Kimura,

Kitahara

2023

J. Phys. Chem. C

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The relationship between the valence electronic state and crystal structure of aluminum−transition-metal quasicrystals and their approximants remains to be elucidated. The origin of the semiconducting band structure on the Katz−Gratias− Boudard-type 1/1 approximants has yet to be clarified. We calculated the electronic structure of an Al−Pd−Co 1/1 quasicrystalline approximant (Al 92 Pd 8 Co 28 per unit cell) using density functional theory and analyzed the approximant's valence orbital character by constructing maximally localized Wannier functions. Among the 304 Wannier functions constructed from the valence bands, 288 were localized around transition metal atoms and 12 were localized between two Co atoms. The other four functions were localized around the center of three-membered rings of Co atoms, which indicates the presence of three-center bonds in this approximant. This situation is an exception to the Yannello− Fredrickson and Kitahara's electron rules, which explain the valence electronic states of aluminum−transition metal approximants and their related intermetallic compound semiconductors considering only two-center bonds. In this study, these rules are expanded to consider three-center bonds, making it possible to explain the semiconducting origin. This work indicates that the electron rule considering three-center bonds can be applied to quasicrystals and other approximants that have triangle networks.

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High-Temperature Specific Heat of Al–Cu–Ru Icosahedral Quasicrystals and 1/1 Crystal Approximants

Cited by 11 publications

References 14 publications

Reduction of Thermal Conductivity for Icosahedral Al-Cu-Fe Quasicrystal through Heavy Element Substitution

Reduction of Thermal Conductivity for Icosahedral Al-Cu-Fe Quasicrystal through Heavy Element Substitution

Unraveling the effects of phason strain on the thermoelectric properties in Ag-In-Yb icosahedral quasicrystals

Three-Center Bonds in an Al–Pd–Co Quasicrystalline Approximant: Wannier Function-Based Chemical Bonding Analysis

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