| 摘要(英) |
GeTe is a chalcogenide with semi-metallic conductivity and ferroelectricity. The ferroelectric temperature is 670 K. Because it has higher electrical conductivity and higher thermal conductivity than other IV-VI compounds (8W/m -1K-1), it’s suitable as a thermoelectric material. However, there are a large number of Ge vacancies in GeTe which decreases the seebeck coefficient and affects the ZT value. Therefore, if the holes concentration can be reduced through doping, its thermoelectric performance can be improved. It is known from other studies that the doping of Sb and Bi in GeTe will affect electrons and phonons and improve the thermoelectricity value. Therefore, in this experiment, we will focus on discussing the influence of impurities on phonon scattering and the reduction of thermal conductivity after sample doping.
We used cold neutron triple-axis spectrometer SIKA in Ansto for inelastic neutron scattering measurement. First, we measured the elastic neutron scattering pattern in the temperature range of 300 K to 710 K. It was found that the sample changed from R3m to Fm3̅m phase in the temperature range of 625 K to 710 K, where two structural phases coexist. In addition, we draw the phonon dispersion diagram of Ge0.86Sb0.08Bi0.06Te in the temperature range of 300 K to 680 K, and obtain the Brillouin zone boundary lattice harmonic energy Eh, electron-phonon interaction energy Ee-p and anharmonic energy Ea. It is found that in this temperature range lattice anharmonicity and very strong electron-phonon interaction occur. In addition, due to the strong electron-phonon scattering, the phonon energy is softened. The properties of the phonon group velocity, phonon lifetime, and propagation length are obtained by fitting. It is known that the sample has a shorter phonon lifetime and phonon propagation length after mixing, and the group velocity will change to a negative value at a large q value. These factors limit the heat transfer and reduce the lattice thermal conductivity of Ge0.86Sb0.08Bi0.06Te, thereby increasing the ZT value of the sample. |
| 參考文獻 |
[1] Thermoelectrics Handbooks—Macro to Nano, edited by D. M. Rowe (2018)
[2] G. J. Snyder & E. S.Toberer , Nature Materials volume 7, 105–114(2008)
[3] Y. Tokure, JSAP international No.2 (Jul. 2000)
[4] S. Roychowdhury, M. Samanta, S. Perumal & K. Biswas, Chem. Mater. 30, 17, 5799–5813(2018)
[5] E. M. Levin, M. F. Besser1, & R. Hanus1, Journal of Applied Physics 114, 083713 (2013)
[6] S. Perumal, S. Roychowdhury & K. Biswas, J. Mater. Chem. C, 4, 7520-7536 (2016)
[7] J. Dong, F.-H. Sun, H. Tang, J. P., H.-L. Zhuang, H.-H. Hu, B.-P. Zhang, Y. Pan &J.-F. Li, Energy Environ. Sci., 12, 1396-1403(2019)
[8] K. Jeong, S. Park, D. Park, M. Ahn, J. Han, W. Yang, H.-S. Jeong & M.-H. Cho, Scientific Reports volume 7, Article number: 955 (2017)
[9] E. M. Levin, M. F. Besser1, & R. Hanus, J. Appl. Phys.114, 083713(2013)
[10] S. Perumal, S. Roychowdhury & K. Biswas,Inorg. Chem. Front., 3, 125-132(2015)
[11] S. Perumal, P. Bellare, U. S. Shenoy, U. V. Waghmare , & K. Biswas, Chem. Mater. 29, 24, 10426–10435(2017)
[12] C. Kittel, Introduction to Solid State Physics, P93-103(1953)
[13] K. Jeong, S. Park, D. Park, M. Ahn, J. Han, W. Yang, H.-S. Jeong and M.-H. Cho, Sci. Rep., 7, 955 (2017)
[14] J. A. Schneeloch, Z. Xu, J. Wen, P. M. Gehring, C. Stock, M. Matsuda, B. Winn, G. Gu, S. M. Shapiro, R. J. Birgeneau, T. Ushiyama, Y. Yanagisawa, Y. Tomioka, T. Ito & G. Xu, , Phys. Rev. B 91, 064301 (2015)
[15] J. Jensen & A. R. Mackintosh, Rare Earth Magnetism: Structures and Excitations P173-177(1991)
[16] S.W. Lovesey, Theory of Neutron Scattering from Condensed Matters, v1, Clarendon Press, Oxford, pp.124-125.( 1984)
[17] P.L. Taylor, A Quantum Approach to the Solid State, Prentice-Hall Inc, New Jersey, pp.103~107, pp.178-182. (1970)
[18] N.W. Ashcroft, N.D. Mermin, D. Wei, Solid State Physics, revised ed., Cengage Learning Asia Pte Ltd, Singapore, pp.771-773.( 2016)
[19] C. Grimaldi, Weak-and strong-coupling limits of the two-dimensional Fröhlich polaron with spin-orbit Rashba interaction, Phys. Rev. B 77, 024306, (2008). |
[Endnote RIS 格式]
[相關文章]
[文章引用]
[完整記錄]
[館藏目錄]
[檢視]
plurk
funp
live
udn
HD
myshare
netvibes
friend
youpush
delicious
baidu
Google bookmarks
del.icio.us
hemidemi
facebook
twitter
google
reddit