Abstract
Investigated in this paper is influence of the size and amount of combustible nanosized particles added as a void forming agent (VFA) for generating isolated closed pores (nanovoids) within a densely sintered Al-doped ZnO matrix on the thermoelectric properties of the oxide. With increasing amount of VFA, the electrical conductivity (σ) and the thermal conductivity (κ) of the samples decrease, while the Seebeck coefficient (S) is relatively insensitive to the amount of VFA; these results appear to be a natural consequence concerning increasing porosity. However, conventional κ-porosity relation is revealed to be unapplicable to the present system, showing a much steeper decrease in κ with increasing porosity. These results suggest that the nanovoid structure is capable of scattering phonons more effectively compared to conventional porous structures with similar porosity. Moreover, the S values significantly increase with decreasing average diameter of VFA from 1800 nm down to 150 nm. Consequently, the samples prepared with 5-10wt% of 150 nm VFA show ZT = 0.54 - 0.59 at 1000°C. Detailed investigation of the transport properties of the samples reveals that the &sigma/κ ratios can be larger for the nanoviod samples than that of the dense matrix without VFA, implying a possible selective phonon scattering.
| Original language | English |
|---|---|
| Title of host publication | Proceedings ICT'07 - 26th International Conference on Thermoelectrics |
| Pages | 112-116 |
| Number of pages | 5 |
| DOIs | |
| Publication status | Published - Dec 1 2007 |
| Event | ICT'07 - 26th International Conference on Thermoelectrics - Jeju, Korea, Republic of Duration: Jun 3 2007 → Jun 7 2007 |
Publication series
| Name | International Conference on Thermoelectrics, ICT, Proceedings |
|---|
Other
| Other | ICT'07 - 26th International Conference on Thermoelectrics |
|---|---|
| Country | Korea, Republic of |
| City | Jeju |
| Period | 6/3/07 → 6/7/07 |
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All Science Journal Classification (ASJC) codes
- Engineering(all)
Cite this
Thermoelectric properties of sintered ZnO incorporating nanovid structure : Influence of the size and number density of nanovoids. / Ohtaki, Michitaka; Hayashi, Ryosuke; Araki, Kazuhiko.
Proceedings ICT'07 - 26th International Conference on Thermoelectrics. 2007. p. 112-116 4569436 (International Conference on Thermoelectrics, ICT, Proceedings).Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Thermoelectric properties of sintered ZnO incorporating nanovid structure
T2 - Influence of the size and number density of nanovoids
AU - Ohtaki, Michitaka
AU - Hayashi, Ryosuke
AU - Araki, Kazuhiko
PY - 2007/12/1
Y1 - 2007/12/1
N2 - Investigated in this paper is influence of the size and amount of combustible nanosized particles added as a void forming agent (VFA) for generating isolated closed pores (nanovoids) within a densely sintered Al-doped ZnO matrix on the thermoelectric properties of the oxide. With increasing amount of VFA, the electrical conductivity (σ) and the thermal conductivity (κ) of the samples decrease, while the Seebeck coefficient (S) is relatively insensitive to the amount of VFA; these results appear to be a natural consequence concerning increasing porosity. However, conventional κ-porosity relation is revealed to be unapplicable to the present system, showing a much steeper decrease in κ with increasing porosity. These results suggest that the nanovoid structure is capable of scattering phonons more effectively compared to conventional porous structures with similar porosity. Moreover, the S values significantly increase with decreasing average diameter of VFA from 1800 nm down to 150 nm. Consequently, the samples prepared with 5-10wt% of 150 nm VFA show ZT = 0.54 - 0.59 at 1000°C. Detailed investigation of the transport properties of the samples reveals that the &sigma/κ ratios can be larger for the nanoviod samples than that of the dense matrix without VFA, implying a possible selective phonon scattering.
AB - Investigated in this paper is influence of the size and amount of combustible nanosized particles added as a void forming agent (VFA) for generating isolated closed pores (nanovoids) within a densely sintered Al-doped ZnO matrix on the thermoelectric properties of the oxide. With increasing amount of VFA, the electrical conductivity (σ) and the thermal conductivity (κ) of the samples decrease, while the Seebeck coefficient (S) is relatively insensitive to the amount of VFA; these results appear to be a natural consequence concerning increasing porosity. However, conventional κ-porosity relation is revealed to be unapplicable to the present system, showing a much steeper decrease in κ with increasing porosity. These results suggest that the nanovoid structure is capable of scattering phonons more effectively compared to conventional porous structures with similar porosity. Moreover, the S values significantly increase with decreasing average diameter of VFA from 1800 nm down to 150 nm. Consequently, the samples prepared with 5-10wt% of 150 nm VFA show ZT = 0.54 - 0.59 at 1000°C. Detailed investigation of the transport properties of the samples reveals that the &sigma/κ ratios can be larger for the nanoviod samples than that of the dense matrix without VFA, implying a possible selective phonon scattering.
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UR - http://www.scopus.com/inward/citedby.url?scp=51849099495&partnerID=8YFLogxK
U2 - 10.1109/ICT.2007.4569436
DO - 10.1109/ICT.2007.4569436
M3 - Conference contribution
AN - SCOPUS:51849099495
SN - 9781424422623
T3 - International Conference on Thermoelectrics, ICT, Proceedings
SP - 112
EP - 116
BT - Proceedings ICT'07 - 26th International Conference on Thermoelectrics
ER -