Single crystallization of Ba8AlxSi46−x clathrate for improvement of thermoelectric properties

Mugita, Naoki; Nakakohara, Yusuke; Teranishi, Ryo; Munetoh, Shinji

doi:10.1557/jmr.2011.193

Cited by 12 publications

(7 citation statements)

References 10 publications

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“…Ba 8 Al 16 Si 30 with type I clathrate structure has been characterized with an aim toward potentially high thermoelectric efficiency at high temperatures. − The phase range, structure, and thermoelectric properties of Ba 8 Al x Si 46‑ x type I clathrates have been previously investigated. − Ba 8 Al 14 Si 31 has a zT reaching 0.34 at 1150 K, and all the samples showed relatively low thermal conductivity (∼2 W/Km) . Further improvement can be achieved by optimizing the carrier concentration.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

Sui

Bobev

et al. 2015

Chem. Mater.

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Å, respectively. The type I clathrate structure (cubic, Pm3̅ n) was confirmed for all phases, and in the case of K 8 Al 8 Si 38 and K 8 Ga 8 Si 38 , the structures were also refined using synchrotron powder diffraction data. The samples were consolidated by Spark Plasma Sintering (SPS) for thermoelectric property characterization. Electrical resistivity was measured by four probe AC transport method in the temperature range of 30 to 300 K. Seebeck measurements from 2 to 300 K were consistent with K 8 Al 8 Si 38 and K 8 Ga 8 Si 38 being n-type semiconductors, while Rb 8 Ga 8 Si 38 and Cs 8 Ga 8 Si 38 were p-type semiconductors. K 8 Al 8 Si 38 shows the lowest electrical resistivity and the highest Seebeck coefficient. This phase also showed the largest thermal conductivity at room temperature of ∼1.77 W/Km. K 8 Ga 8 Si 38 provides the lowest thermal conductivity, below 0.5 W/Km, comparable to the type I clathrate with heavy elements such as Ba 8 Ga 16 Ge 30. Surface photovoltage spectroscopy on films shows that these compounds are semiconductors with band gaps in the range 1.14 to 1.40 eV.

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Section: Introductionmentioning

confidence: 99%

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

Sui

Bobev

et al. 2015

Chem. Mater.

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“…It is interesting to note that peaks in the heat capacities are only observed at higher Al content. We assume that it is not a coincidence that the synthesis of Ba 8 Al x Ge 46– x with x ≥ 16 , and Ba 8 Al x Si 46– x with x ≥ 15 ,− has proved difficult. Instead, we suggest that not only the chemical ordering but also the order–disorder transition directly affects the stability of these compounds.…”

Section: Resultsmentioning

confidence: 99%

First-Principles Study of Order–Disorder Transitions in Pseudobinary Clathrates

2021

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It has been recently demonstrated that the pseudoternary Ba8Al x Ga y Ge46–x–y clathrate undergoes an order–disorder transition with increasing temperature that can be observed via site occupation factors (SOFs) and manifests itself, e.g., in electrical transport properties. Here, we generalize this result and analyze the characteristics of this order–disorder transition in the pseudobinary clathrates Ba8Ga x Ge46–x , Ba8Ga x Si46–x , Ba8Al x Ge46–x , and Ba8Al x Si46–x . To this end, we employ atomistic simulations that combine alloy cluster expansions trained against density functional theory calculations with Wang–Landau and ensemble Monte Carlo simulations. The simulations show that all four systems studied here display order–disorder transitions for at least some composition range. Based on an extensive literature survey, we also provide evidence for signatures of the transition in earlier experimental studies that to the best of our knowledge have hitherto not been related to such transitions. The predicted transition temperatures are lower for Ba8Ga x Ge46–x and Ba8Ga x Si46–x than for Ba8Al x Ge46–x and Ba8Al x Si46–x , although it appears that the simulations underestimate the transition temperatures for Ga-containing systems compared to the experiment. This nonetheless provides a sensible explanation for why the experimentally determined Al SOFs agree better with the simulated high-temperature disordered configurations, while the Ga SOFs more closely agree with the simulated ground-state configurations. As a result of stronger interactions, the SOFs vary substantially, especially near the stoichiometric 16:30 composition, providing an indication of why it has proved difficult to synthesize Ba8Al x Ge46–x and Ba8Al x Si46–x samples at this ratio. The present study thereby yields detailed atomic-scale insights into the ordering in inorganic clathrates that, given the connection to transport properties established earlier, are not only useful from a fundamental perspective but also relevant for applications.

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“…Synthesis and thermoelectric properties of sintered skutterudite CoSb 3 with a bimodal distribution of crystal grains S Katsuyama, F Maezawa and T Tanaka -Influence of preparation conditions on thermoelectric properties of Ba 8 Ga 16 Si 30 clathrate by combining arc melting and spark plasma sintering methods Hiroaki Anno, Hiroki Yamada, Takahiro Nakabayashi et al …”

Section: Related Contentmentioning

confidence: 99%

“…Many studies of highperformance Si clathrates have been performed by controlling the chemical composition. However, it is reported that most Si-based clathrate compounds show n-type conduction [15,16] and there are few reports of p-type Si-based clathrates [17]. The p-type material is necessary in order to manufacture the n-p modules of thermoelectric generators.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and thermoelectric properties of p-type Ba₈Au_xSi_46-xclathrate

Saisho

Liu

Nagatomo

et al. 2012

J. Phys.: Conf. Ser.

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View the article online for updates and enhancements. clathrates were synthesized by the arc melting method and a subsequent annealing treatment. The as-synthesized sample contained some precipitates rich in Au at the grain boundaries, and the precipitates were reduced by annealing at 1000 ˚C. The Au content of the clathrate phase for the as-synthesized sample, Ba 7.4 Au 4.7 Si 41.3 , was slightly lower than that for the stoichiometric composition, Ba 8 Au 6 Si 40 . In the annealed samples, the Au content of the clathrate phase increased with annealing time. These results indicated that Au can diffuse from Au-rich precipitates to the clathrate phase by annealing. The Seebeck coefficient of the as-synthesized and 1 hour annealed sample, Ba 7.5 Au 5.7 Si 40.3 , were -80 and +100 V/K at 500 ˚C, respectively. This suggested that the carrier type was changed by the Au content in the clathrate. In the samples annealed for longer than 1 hour, the Seebeck coefficient decreased with annealing time. This indicated that the hole carrier concentration increased in excess because of overdoping due to the diffusion of Au. Related content

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Single crystallization of Ba₈Al_xSi_46−x clathrate for improvement of thermoelectric properties

Abstract: Abstract

Cited by 12 publications

References 10 publications

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

First-Principles Study of Order–Disorder Transitions in Pseudobinary Clathrates

Synthesis and thermoelectric properties of p-type Ba₈Au_xSi_46-xclathrate

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Single crystallization of Ba8AlxSi46−x clathrate for improvement of thermoelectric properties

Abstract: Abstract

Cited by 12 publications

References 10 publications

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A8Ga8Si38 (A = K, Rb, Cs) and K8Al8Si38

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A8Ga8Si38 (A = K, Rb, Cs) and K8Al8Si38

First-Principles Study of Order–Disorder Transitions in Pseudobinary Clathrates

Synthesis and thermoelectric properties of p-type Ba8AuxSi46-xclathrate

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Single crystallization of Ba₈Al_xSi_46−x clathrate for improvement of thermoelectric properties

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

Synthesis, Structure, Thermoelectric Properties, and Band Gaps of Alkali Metal Containing Type I Clathrates: A₈Ga₈Si₃₈ (A = K, Rb, Cs) and K₈Al₈Si₃₈

Synthesis and thermoelectric properties of p-type Ba₈Au_xSi_46-xclathrate