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Prediction of Giant Thermoelectric Power Factor in Type-VIII Clathrate Si 46

View Article: PubMed Central - PubMed

ABSTRACT

Clathrate materials have been the subject of intense interest and research for thermoelectric application. Nevertheless, from the very large number of conceivable clathrate structures, only a small fraction of them have been examined. Since the thermal conductivity of clathrates is inherently small due to their large unit cell size and open-framework structure, the current research on clathrates is focused on finding the ones with large thermoelectric power factor. Here we predict an extraordinarily large power factor for type-VIII clathrate Si46. We show the existence of a large density of closely packed elongated ellipsoidal carrier pockets near the band edges of this so far hypothetical material structure, which is higher than that of the best thermoelectric materials known today. The high crystallographic symmetry near the energy band edges for Si46-VIII clathrates is responsible for the formation of such a large number of carrier pockets.

No MeSH data available.


The total and the partial power factors of each peak in valence band of the type-VIII Si46 along with the Fermi energy as a function of doping concentration (inset).The colored band indicated the thermal broadening of the carrier distribution around Fermi energy (i.e. Ef ± 2kBT). (a) p-type, and (b) n-type.
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f2: The total and the partial power factors of each peak in valence band of the type-VIII Si46 along with the Fermi energy as a function of doping concentration (inset).The colored band indicated the thermal broadening of the carrier distribution around Fermi energy (i.e. Ef ± 2kBT). (a) p-type, and (b) n-type.

Mentions: We calculated the Fermi energy and the power factor as functions of the doping concentration for the temperature of 1000 C as shown in Figure 2. The results predict that both for p-type and n-type Si46–VIII there exist optimum values for the doping concentration which are approximately 1.1 × 1021 cm−3 and 1.04 × 1021 cm−3, respectively. We have considered a doping concentration of 1.1 × 1021 cm−3 for both p-type and n-type Si46-VIII in all other calculations. As presented in Figure 2, for both types the total power factor is predicted to increase rapidly with doping concentration. The contribution of each peak of the valence band in the power factor is also presented in Figure 2. For the p-type material the highest contribution comes from the NH and N peaks and after that the ΓH, P, and Γ peaks give their contributions at higher doping concentrations, respectively. For the n-type material, NH, ΓH, and Γ valleys have highest contribution, respectively.


Prediction of Giant Thermoelectric Power Factor in Type-VIII Clathrate Si 46
The total and the partial power factors of each peak in valence band of the type-VIII Si46 along with the Fermi energy as a function of doping concentration (inset).The colored band indicated the thermal broadening of the carrier distribution around Fermi energy (i.e. Ef ± 2kBT). (a) p-type, and (b) n-type.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382702&req=5

f2: The total and the partial power factors of each peak in valence band of the type-VIII Si46 along with the Fermi energy as a function of doping concentration (inset).The colored band indicated the thermal broadening of the carrier distribution around Fermi energy (i.e. Ef ± 2kBT). (a) p-type, and (b) n-type.
Mentions: We calculated the Fermi energy and the power factor as functions of the doping concentration for the temperature of 1000 C as shown in Figure 2. The results predict that both for p-type and n-type Si46–VIII there exist optimum values for the doping concentration which are approximately 1.1 × 1021 cm−3 and 1.04 × 1021 cm−3, respectively. We have considered a doping concentration of 1.1 × 1021 cm−3 for both p-type and n-type Si46-VIII in all other calculations. As presented in Figure 2, for both types the total power factor is predicted to increase rapidly with doping concentration. The contribution of each peak of the valence band in the power factor is also presented in Figure 2. For the p-type material the highest contribution comes from the NH and N peaks and after that the ΓH, P, and Γ peaks give their contributions at higher doping concentrations, respectively. For the n-type material, NH, ΓH, and Γ valleys have highest contribution, respectively.

View Article: PubMed Central - PubMed

ABSTRACT

Clathrate materials have been the subject of intense interest and research for thermoelectric application. Nevertheless, from the very large number of conceivable clathrate structures, only a small fraction of them have been examined. Since the thermal conductivity of clathrates is inherently small due to their large unit cell size and open-framework structure, the current research on clathrates is focused on finding the ones with large thermoelectric power factor. Here we predict an extraordinarily large power factor for type-VIII clathrate Si46. We show the existence of a large density of closely packed elongated ellipsoidal carrier pockets near the band edges of this so far hypothetical material structure, which is higher than that of the best thermoelectric materials known today. The high crystallographic symmetry near the energy band edges for Si46-VIII clathrates is responsible for the formation of such a large number of carrier pockets.

No MeSH data available.