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題名 Fe2VGa摻雜Ti及Si之電子結構跟熱電性質之研究
Electronic structure and thermoelectric properties of Ti and Si doped Fe2VGa作者 黃大頌
Huang, Ta Sung貢獻者 陳洋元教授
Chen, Yang Yuan
黃大頌
Huang, Ta Sung關鍵詞 熱電材料
Full Heusler
Fe2VGa
熱傳導日期 2013 上傳時間 25-Aug-2014 15:23:04 (UTC+8) 摘要 熱電材料被視為其中一種可以解決能源問題的材料,其中具有高功率因子(power factor)的Heusler系統近年來被廣泛的研究。這篇論文中,我們利用取代效應探討鐵釩鎵(Fe2VGa) Heusler系統的熱電性質以及磁性性質,其中包括鈦原子(Ti)取代釩原子(V)跟矽原子(Si)取代鎵原子(Ga)。我們使用電弧熔煉法合成所有樣品,包括Fe2V1-xTixGa (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) 和 Fe2VGa1-xSix (x = 0, 0.05, 0.1, 0.15, 0.2)。在X光繞射的分析中,我們展示了所有樣品都是L21的晶體結構還有每個樣品的晶格常數;同時,我們利用能量分散式光譜儀揭露了樣品的化學計量式。當取代濃度大於0.1時,兩個不同取代系統的功率因子(power factor=S2/ρ)皆會大幅度的提升,這現象可以歸功於能態密度中費米能階的移動。由能帶計算中我們得知鐵釩鎵系統的費米能階坐落在pseudo gap中,然而取代效應使費米能階移出pseudo gap,進而跟能態密度有交錯,導致Seebeck常數上升,而功率因子又與Seebeck常數成平方正比的關係,所以兩個不同取代系統的功率因子皆大幅度的提升。因為合金效應的關係,使所有有取代樣品的傳熱性都大幅度被壓抑,其中Fe2VGa0.8Si0.2的熱傳導性被抑制了兩倍。因為傳熱性的抑制以及同時功率因子的提升,使得Fe2V0.8Ti0.2Ga的熱電優值在420 K時較未被Ti取代之母材Fe2VGa提高了10倍。另外,我們也介由觀察樣品的磁化率以及磁化量探討了這些樣品的磁性性質。
Thermoelectric application has been considered as a possible solution for electric crises, and, recently, Heusler alloys have been studied for its large power factor near room temperature. In this thesis, we investigate the thermoelectric and magnetic properties of Ti-substituted (p-type) and Si-substituted (n-type) Heusler alloy Fe2VGa. All samples including Fe2V1-xTixGa (with x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) and Fe2VGa1-xSix (with x = 0, 0.05, 0.1, 0.15, 0.2) are prepared through arc-melting method. The X-ray refinement shows their L21 crystal structure and corresponding lattice parameters, while the Energy-dispersive X-ray spectroscopy (EDX) reveals the stoichiometry. With proper substitution, with x > 0.1, the power factor of both systems is dramatically enhanced, which can be attributed to the Fermi level shifting. According to the theoretical calculation for the density of state, the Fermi level of the un-doped sample is located within the pseudogap, while the Fermi level starts to move out the pseudogap since the substituting effect applying, and it will consequently intercept with the conduction or valence band. Due to the alloying effect, the thermal conductivity of Fe2VGa0.8Si0.2 sample is significantly suppressed by a factor of 2. Therefore, we observed that the figure of merit (zT) in Fe2V0.8Ti0.2Ga sample is enhanced by 10 times at 420 K as compared with the parent compound Fe2VGa. Their magnetic properties are also investigated by means of susceptibility and magnetization measurements.參考文獻 1. C.S. Lue, C.F. Chen, J.Y. Lin, Y.T. Yu, and Y.K. Kuo, Phys. Rev. B 75, 064204 (2007)2. Y. Nishino, and Y. Tamada, J. Appl. Phys. 115, 123707 (2014)3. M. Vasundhara, V. Srinivas, and V.V. Rao, Phys. Rev. B 77, 224415 (2008)4. Y. Nishino, S. Deguchi, and U. Mizutani, Phys. Rev. B 74, 115115(2006)5. K. Renard, A. Mori, Y. Yamada, S. Tanaka, H. Miyazaki, and Y. Nishino, J. Appl. Phys. 115, 033707 (2014)6. H. Kato, M. Kato, Y. Nishino, U. Mizutani, and S. Asano, J. Jpn. Inst. Met. 65, 652 (2001)7. W. Xie, S. Wang, S. Zhu, J. He, X. Tang, Q. Zhang, and T.M. Tritt, J. Mater. Sci. 48, 2745–2760 (2013) 8. C.S. Lue, and Y.K. Kuo, Phys. Rev. B 66, 085121 (2002) 9. A. Bansil, S. Kaprzyk, P. E. Mijnarends, and J. Toboła, Phys. Rev. B 60, 13396 (1999)10. C. S. Lue and J. H. Ross, Jr., Phys. Rev. B 63, 054420 (2001)11. N. Kawamiya, Y. Nishino, M. Matsuo, and S. Asano, Phys. Rev. B 44, 12406 (1991)12. K. Endo, H. Matsuda, K. Ooiwa, M. Iijima, K. Ito, T. Goto, A. Ono, J. Phys. Soc. Jpn. 66, 1257 (1997).13. A. Slebarski, and J. Goraus, Phys. Rev. B 80, 235121 (2009)14. Melvin Cutler et al. Physical Review 181, 1336 (1969)15. L.S. Hsu, Y.K. Wang, G.Y. Guo, and C.S. Lue, Phys. Rev. B 66, 205203 (2002)16. C.S. Lue, W.J. Lai, C.C. Chen and Y.K. Kuo, J. Phys.: Condens. Matter 16, 4283 (4283)17. C.S. Lue, Joseph H. Ross Jr, K.D.D. Rathnayaka, D.G. Naugle, S.Y. Wu, and W.H. Li, J. Phys.: Condens. Matter 13, 1585 (2001) 描述 碩士
國立政治大學
應用物理研究所
101755012
102資料來源 http://thesis.lib.nccu.edu.tw/record/#G0101755012 資料類型 thesis dc.contributor.advisor 陳洋元教授 zh_TW dc.contributor.advisor Chen, Yang Yuan en_US dc.contributor.author (Authors) 黃大頌 zh_TW dc.contributor.author (Authors) Huang, Ta Sung en_US dc.creator (作者) 黃大頌 zh_TW dc.creator (作者) Huang, Ta Sung en_US dc.date (日期) 2013 en_US dc.date.accessioned 25-Aug-2014 15:23:04 (UTC+8) - dc.date.available 25-Aug-2014 15:23:04 (UTC+8) - dc.date.issued (上傳時間) 25-Aug-2014 15:23:04 (UTC+8) - dc.identifier (Other Identifiers) G0101755012 en_US dc.identifier.uri (URI) http://nccur.lib.nccu.edu.tw/handle/140.119/69233 - dc.description (描述) 碩士 zh_TW dc.description (描述) 國立政治大學 zh_TW dc.description (描述) 應用物理研究所 zh_TW dc.description (描述) 101755012 zh_TW dc.description (描述) 102 zh_TW dc.description.abstract (摘要) 熱電材料被視為其中一種可以解決能源問題的材料,其中具有高功率因子(power factor)的Heusler系統近年來被廣泛的研究。這篇論文中,我們利用取代效應探討鐵釩鎵(Fe2VGa) Heusler系統的熱電性質以及磁性性質,其中包括鈦原子(Ti)取代釩原子(V)跟矽原子(Si)取代鎵原子(Ga)。我們使用電弧熔煉法合成所有樣品,包括Fe2V1-xTixGa (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) 和 Fe2VGa1-xSix (x = 0, 0.05, 0.1, 0.15, 0.2)。在X光繞射的分析中,我們展示了所有樣品都是L21的晶體結構還有每個樣品的晶格常數;同時,我們利用能量分散式光譜儀揭露了樣品的化學計量式。當取代濃度大於0.1時,兩個不同取代系統的功率因子(power factor=S2/ρ)皆會大幅度的提升,這現象可以歸功於能態密度中費米能階的移動。由能帶計算中我們得知鐵釩鎵系統的費米能階坐落在pseudo gap中,然而取代效應使費米能階移出pseudo gap,進而跟能態密度有交錯,導致Seebeck常數上升,而功率因子又與Seebeck常數成平方正比的關係,所以兩個不同取代系統的功率因子皆大幅度的提升。因為合金效應的關係,使所有有取代樣品的傳熱性都大幅度被壓抑,其中Fe2VGa0.8Si0.2的熱傳導性被抑制了兩倍。因為傳熱性的抑制以及同時功率因子的提升,使得Fe2V0.8Ti0.2Ga的熱電優值在420 K時較未被Ti取代之母材Fe2VGa提高了10倍。另外,我們也介由觀察樣品的磁化率以及磁化量探討了這些樣品的磁性性質。 zh_TW dc.description.abstract (摘要) Thermoelectric application has been considered as a possible solution for electric crises, and, recently, Heusler alloys have been studied for its large power factor near room temperature. In this thesis, we investigate the thermoelectric and magnetic properties of Ti-substituted (p-type) and Si-substituted (n-type) Heusler alloy Fe2VGa. All samples including Fe2V1-xTixGa (with x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) and Fe2VGa1-xSix (with x = 0, 0.05, 0.1, 0.15, 0.2) are prepared through arc-melting method. The X-ray refinement shows their L21 crystal structure and corresponding lattice parameters, while the Energy-dispersive X-ray spectroscopy (EDX) reveals the stoichiometry. With proper substitution, with x > 0.1, the power factor of both systems is dramatically enhanced, which can be attributed to the Fermi level shifting. According to the theoretical calculation for the density of state, the Fermi level of the un-doped sample is located within the pseudogap, while the Fermi level starts to move out the pseudogap since the substituting effect applying, and it will consequently intercept with the conduction or valence band. Due to the alloying effect, the thermal conductivity of Fe2VGa0.8Si0.2 sample is significantly suppressed by a factor of 2. Therefore, we observed that the figure of merit (zT) in Fe2V0.8Ti0.2Ga sample is enhanced by 10 times at 420 K as compared with the parent compound Fe2VGa. Their magnetic properties are also investigated by means of susceptibility and magnetization measurements. en_US dc.description.tableofcontents 摘要 iAbstract iiTable of Contents iiiList of Figures vChapter 1 Introduction 1Chapter 2 Basic Concepts 42.1 Thermoelectric Effect 42.1.1 Seebeck Effect 42.1.2 Peltier Effect 62.1.3 Thomson Effect 72.2 Electrical Conductivity 92.3 Thermal conductivity 112.3.1 Lattice Thermal Conductivity 122.3.2 Electronic Thermal Conductivity 142.3.3 Umklapp Scattering 16Chapter 3 Experimental Procedures 183.1 X-ray Diffraction (PANalytical X’pert Powder) 183.2 Thermoelectric Properties Measurements 203.2.1 Thermal Diffusivity (LFA-457, NETZSCH) 203.2.2 Seebeck Coefficient and Electrical Resistivity 233.3 Magnetic Susceptibility Measurements 24Chapter 4 Results and Discussions 274.1 Ti-doped Fe2VGa 284.1.1 Crystal Structure Analysis 284.1.2 Electrical Resistivity 314.1.3 Seebeck Coefficient 344.1.4 Thermal Conductivity 364.1.5 Power Factor 404.1.6 Figure of Merit (zT) 414.1.7 Magnetic Properties 424.2 Si-doped Fe2VGa 454.2.1 Crystal Structure Analysis 454.2.2 Electrical Resistivity 484.2.3 Seebeck Coefficient 494.2.4 Thermal Conductivity 514.2.5 Power Factor 544.2.6 Figure of Merit (zT) 55Chapter 5 Conclusions 56References 58 zh_TW dc.format.extent 2230400 bytes - dc.format.mimetype application/pdf - dc.language.iso en_US - dc.source.uri (資料來源) http://thesis.lib.nccu.edu.tw/record/#G0101755012 en_US dc.subject (關鍵詞) 熱電材料 zh_TW dc.subject (關鍵詞) Full Heusler zh_TW dc.subject (關鍵詞) Fe2VGa zh_TW dc.subject (關鍵詞) 熱傳導 zh_TW dc.title (題名) Fe2VGa摻雜Ti及Si之電子結構跟熱電性質之研究 zh_TW dc.title (題名) Electronic structure and thermoelectric properties of Ti and Si doped Fe2VGa en_US dc.type (資料類型) thesis en dc.relation.reference (參考文獻) 1. C.S. Lue, C.F. Chen, J.Y. Lin, Y.T. Yu, and Y.K. Kuo, Phys. Rev. B 75, 064204 (2007)2. Y. Nishino, and Y. Tamada, J. Appl. Phys. 115, 123707 (2014)3. M. Vasundhara, V. Srinivas, and V.V. Rao, Phys. Rev. B 77, 224415 (2008)4. Y. Nishino, S. Deguchi, and U. Mizutani, Phys. Rev. B 74, 115115(2006)5. K. Renard, A. Mori, Y. Yamada, S. Tanaka, H. Miyazaki, and Y. Nishino, J. Appl. Phys. 115, 033707 (2014)6. H. Kato, M. Kato, Y. Nishino, U. Mizutani, and S. Asano, J. Jpn. Inst. Met. 65, 652 (2001)7. W. Xie, S. Wang, S. Zhu, J. He, X. Tang, Q. Zhang, and T.M. Tritt, J. Mater. Sci. 48, 2745–2760 (2013) 8. C.S. Lue, and Y.K. Kuo, Phys. Rev. B 66, 085121 (2002) 9. A. Bansil, S. Kaprzyk, P. E. Mijnarends, and J. Toboła, Phys. Rev. B 60, 13396 (1999)10. C. S. Lue and J. H. Ross, Jr., Phys. Rev. B 63, 054420 (2001)11. N. Kawamiya, Y. Nishino, M. Matsuo, and S. Asano, Phys. Rev. B 44, 12406 (1991)12. K. Endo, H. Matsuda, K. Ooiwa, M. Iijima, K. Ito, T. Goto, A. Ono, J. Phys. Soc. Jpn. 66, 1257 (1997).13. A. Slebarski, and J. Goraus, Phys. Rev. B 80, 235121 (2009)14. Melvin Cutler et al. Physical Review 181, 1336 (1969)15. L.S. Hsu, Y.K. Wang, G.Y. Guo, and C.S. Lue, Phys. Rev. B 66, 205203 (2002)16. C.S. Lue, W.J. Lai, C.C. Chen and Y.K. Kuo, J. Phys.: Condens. Matter 16, 4283 (4283)17. C.S. Lue, Joseph H. Ross Jr, K.D.D. Rathnayaka, D.G. Naugle, S.Y. Wu, and W.H. Li, J. Phys.: Condens. Matter 13, 1585 (2001) zh_TW