Mg2Si 基合金屬中溫型熱電材料之一，其發展前景可期，近年來逐漸受到關注。 Mg2Si 基合金具有重量輕、價格便宜且不具毒性等優點，有利於日後中溫型熱電模組系統的推廣與應用；其 ZT 值的研究主要集中於調控熱電塊材的載子濃度，進而增加塊材的電傳導率，以提升功率因子 (power factor)。
於製程上，由於 Mg2Si 基合金之各項元素組成的熔點差異極大，故不易進行熔煉製作，因此本研究利用固相反應法，將銻摻雜於 Mg2Si 基粉體，利用熱處理的方式先行將各元素以固相擴散反應的方式鍵結成 Mg2Si 基粉體，而後再利用熱壓燒結製備合金塊材。實驗是探討熱處理暨熱壓燒結參數對粉體及塊材的晶相、成分及微觀結構的影響，並檢討銻摻雜量對塊材的顯微結構及熱電性質的影響。
在熱電性質方面，無 Sb 摻雜的 Mg2Si 塊材，其電傳行為是隨著溫度的增加會有由p型半導體轉變成 n 型半導體； Sb 摻雜的 Mg2Si:Sb0.005 塊材則為 n 型摻雜半導體的電傳行為，其電傳導率是隨著溫度的增加而增加， Seebeck 係數則略微減少。 800 oC 熱壓燒結所得之 Mg2Si:Sb0.005 塊材，其功率因子 (S2σ) 於 765 K 時有最大值 ，為 0.0274 mW/m-K2。
無 Sb 摻雜的 Mg2.16(Si0.4Sn0.6) 塊材，隨著溫度增加亦會有由p型半導體轉變成 n 型半導體的電傳行為；Sb 摻雜的 Mg2.16(Si0.4Sn0.6)1-ySby (y=0.0075, 0.015, 0.025) 塊材則為 n 型摻雜半導體的電傳行為，其電傳導率隨著溫度的增加而增加， Seebeck 係數則減少。諸試樣中以 650 oC火花電漿燒結所得之 Mg2.16(Si0.4Sn0.6)0.975Sb0.025 塊材，其功率因子 (S2σ) 於 710 K 時有最大值 1.03 mW/m-K2，此值為無 Sb 摻雜的 Mg2.16(Si0.4Sn0.6) 塊材之功率因子 (0.0513 mW/m-K2) 的 20.1 倍。Sb 摻雜的 Mg2.16(Si0.4Sn0.6)1-ySby (y=0.0075, 0.015, 0.025) 塊材其熱傳導率於 473 K - 573 K量測溫度區間皆低於未摻雜之 Mg2.16(Si0.4Sn0.6) 塊材。650 oC 火花電漿燒結所得之 Mg2.16(Si0.4Sn0.6)0.975Sb0.025 塊材，其熱電優值 (ZT) 於 573 K 時為 0.2。

Due to the difference of melting point amomg Mg, Si and Sb elements, it is not easy to synthesize Mg2Si -based alloy by melting method. In this study, Mg2Si-based thermoelectric bulks were fabricated by solid-state reaction and hot-pressed sintering (HP, SPS). The results show that with the increase of Sb-doping in Mg2Si, the electrical conductivity (σ) increase, and the Seebeck coefficient increase slightly at higher temperature. The power factor of Mg2Si -based bulks was improved by Sb doping. The maximum value of the power factor, PF, is 1.03 mW/m-k2 at 765K for the Mg2.16(Si0.4Sn0.6)0.975Sb0.025 bulk.

1. D. M. Rowe, CRC Handbook of Thermoelectrics, CRC Press, Boca Raton, USA (1995).
2. G. S. Nolas, J. W. Sharp and H. J. Goldsmid, Thermoelectrics: Basic Principles and New Materials Developments, Springer-Verlag, Heidelberg (2001).
3. D. M. Rowe, Thermoelectrics Handbook: Micro to Nano, CRC Press, New York (2006).
4. J. J. Pulikkotil, D. J. Singh, S. Auluck, M. Saravanan, D. K. Misra, A. Dhar, and R. C. Budhani, “Doping and temperature dependence of thermoelectric properties in Mg2(Si,Sn),” Phys. Rev. B, 86, 155204 (2012)
5. S. Muthiah, J. Pulikkotil, A. K. Srivastava, A. Kumar, B. D. Pathak, A. Dhar, and R. C. Budhani, “Conducting grain boundaries enhancing thermoelectric performance in doped Mg2Si,” Appl. Phys. Lett. 103, 053901 (2013).
6. M. Ioannou, K. Chrissafis, E. Pavlidou, F. Gascoin, Th. Kyratsi, “Solid-state synthesis of Mg2Si via short-duration ball-milling and low-temperature annealing,” J. Solid State Chem., 197, 172 (2013).
7. J. Tani, H. Kido, “Fabrication and thermoelectric properties of Mg2Si-based composites using reduction reaction with additives,” Intermetallics, 32, 72 (2013).
8. T. Nemoto, T. Iida, J. Sato, T. Sakamoto, N. Hirayama, T. Nakajima, and Y. Takanashi, “Development of an Mg2Si Unileg Thermoelectric Module Using Durable Sb-Doped Mg2Si Legs,” J. Electron. Mater. 42, 7, 2192 (2013).
9. X. Zhang, H. Liu, Q. Lu,1 J. Zhang, and F. Zhang, “Enhanced thermoelectric performance of Mg2Si0.4Sn0.6 solid solutions by in nanostructures and minute Bidoping,” Appl. Phys. Lett. 103, 063901 (2013).
10. M. Tokita, “Mechanism of Spark Plasma Sintering,” J. Soc. Powder Tech. Jpn., 30, 790 (1993).
11. Y. W. Chou, “Spark Plasma Sintering Method and Effect on the Development of Thermoelectric Material,” Industrial Mater., 287, 11, 142 (2010).
12. J. I. Tani, H. Kido, “First-principles and experimental studies of impurity doping into Mg2Si,” Intermetallics, 16 , 418-423 (2008).
13. Jae-Yong Jung, and Il-Ho Kim, “Synthesis and Thermoelectric Properties of n-Type Mg2Si,” Electro. Mater. Lett., 6, 4, 187-191 (2010).
14. Tatsuya Sakamoto, Tsutomu Iida, Atsunobu Matsumoto, Yasuhiko Honda, Takashi Nemoto, Junichi Sato, Tadao Nakajima, Hirohisa Taguchi, and Yoshifumi Takanashi, “Thermoelectric Characteristics of a Commercialized Mg2Si Source Doped with Al, Bi, Ag, and Cu,” J. Electro. Mater., 39, 9 (2010).
15. Tatsuya Sakamoto, Tsutomu Iida, Shota Kurosaki, Kenji Yano, Hirohisa Taguchi, Keishi Nishio, and Yoshifumi Takanashi, “Thermoelectric Behavior of Sb- and Al-Doped n-Type Mg2Si Device Under Large Temperature Differences,”
J. Electro. Mater., 40, 5 (2011).
16. Soon-Mok Choi, Kyung-Ho Kim, Il-Ho Kim, Sun-Uk Kim, Won-Seon Seo,“Thermoelectric properties of the Bi-doped Mg2Si system,” Curr. Appl. Phys. 11, 388-391 (2011).
17. Sin-Wook You, Kwan-Ho Park, Il-Ho Kim, Soon-Mok Choi, Won-Seon Seo, and Sun-Uk Kim, “Solid-State Synthesis and Thermoelectric Properties of Al-Doped Mg2Si,” J. Electro. Mater., 41, 6 (2012).
18. David Berthebaud, Franck Gascoin, “Microwaved assisted fast synthesis of n and p-doped Mg2Si,” J. Solid State Chem. 202, 61-64 (2013).
19. J. de Boor, C. Compere, T. Dasgupta, C. Stiewe, H. Kolb, A. Schmitz, E. Mueller,“Fabrication parameters for optimized thermoelectric Mg2Si,” J. Mater. Sci., 49, 3196-3204 (2014).
20. R. Janot, F. Cuevas, M. Latroche, A. Percheron-Gue´gan, “Influence of crystallinity on the structural and hydrogenation properties of Mg2X phases (X=Ni, Si, Ge, Sn),” Intermetallics 14, 163-169 (2006).
21. Y. Isoda, T. Nagai, H. Fujiu, Y. Imai, Y. Shinohara, “Thermoelectric Properties of Sb-doped Mg2Si0.5Sn0.5,” IEEE, 406-410 (2006).
22. V. K. Zaitsev, M. I. Fedorov, E. A. Gurieva, I. S. Eremin, P. P. Konstantinov, A. Yu. Samunin, and M. V. Vedernikov, “Highly effective Mg2Si1−xSnx thermoelectrics, ” Phys. Rev. B 74, 045207 (2006).
23. R. B. Song, T. Aizawa , J. Q. Sun, “Synthesis of Mg2Si1−xSnx solid solutions as thermoelectric materials by bulk mechanical alloying and hot pressing,” Mater. Sci. Eng. B, 136 , 111-117 (2007).
24. Q. Zhang, J. He, T. J. Zhu, S. N. Zhang, X. B. Zhao, and T. M. Tritt, “High figures of merit and natural nanostructures in Mg2Si0.4Sn0.6 based thermoelectric materials,” Appl. Phys. Lett. 93, 102109 (2008).
25. Weijun Luo, Meijun Yang, Fei Chen, Qiang Shen, Hongyi Jiang and Lianmeng Zhang, “Preparation and Thermoelectric Properties of Bi-Doped Mg2Si0.8Sn0.2 Compound,” Mater. Trans, 51, 2 , 288-291 (2010).
26. H. L. Gao, X. X. Liu, T. J. Zhu, S. H. Yang, and X. B. Zhao, “Effect of Sb Doping on the Thermoelectric Properties of Mg2Si0.7Sn0.3 Solid Solutions,” J. Electro. Mater., 40, 5 (2011).
27. Wei Liu, Xinfeng Tang, Han Li, Kang Yin, Jeff Sharp, Xiaoyuan Zhou, and Ctirad Uher, “Enhanced thermoelectric properties of n-type Mg2.16(Si0.4Sn0.6)1-ySby due to nano-sized Sn-rich precipitates and an optimized electron
concentration,” J. Mater. Chem., 22, 13653 (2012).
28. Xin Zhang, Hongliang Liu, Qingmei Lu, Jiuxing Zhang, and Feipeng Zhang, “Enhanced thermoelectric performance of Mg2Si0.4Sn0.6 solid solutions by in nanostructures and minute Bi-doping,” Appl. Phys. Lett. 103, 063901 (2013).
29. Wei Liu, Qiang Zhang, Kang Yin, Hang Chi, Xiaoyuan Zhou, Xin feng Tang, Ctirad Uher, “High figure of merit and thermoelectric properties of Bi-doped Mg2Si0.4Sn0.6 solid solutions,” J. Solid State Chem., 203, 333–339 (2013).
30. Sin-Wook You, Il-Ho Kim, Soon-Mok Choi, and Won-Seon Seo, “Solid-State Synthesis and Thermoelectric Properties of Mg2+xSi0.7Sn0.3Sbm,”J. Nanomater.,2013, 815925 (2013).
31. T. Dasgupta, C. Stiewe, J. de Boor, and E. Müller, “Influence of power factor enhancement on the thermoelectric figure of merit in Mg2Si0.4Sn0.6 based materials,” Phys. Status Solidi A 211, 6, 1250-1254 (2014).
32. J. Wei Liu, Minghui Song, Masaki Takeguchi, Naohito Tsujii, and Yukihiro Isoda, “Transmission Electron Microscopy Study of Mg2Si0.5Sn0.5 Solid Solution for
High-Performance Thermoelectrics,” J. Electron. Mater. 44, 1 (2015).
33. In-Ho Jung, Dae-Hoon Kang, Woo-Jin Park, Nack J. Kim, Sang Ho Ahn, “Thermodynamic modeling of the Mg–Si–Sn system,” CALPHAD 31, 192-200 (2007).
34. H. Okamoto, “Mg-Si (Magnesium-Silicon) ,” J. Phase Equilib. Diff. 28, 2 (2007).
35. W. Liu, X. F. Tang, and J Sharp, “Low-temperature solid state reaction synthesis and thermoelectric properties of high-performance and low-cost Sbdoped Mg2Si0.6Sn0.4,” J. Phys. D: Appl. Phys. 43, 085406 (2010).
36. Weijun Luo, Meijun Yang, Fei Chen, Qiang Shen, Hongyi Jiang, Lianmeng Zhang, “Fabrication and thermoelectric properties of Mg2Si1−xSnx (0≤x≤1.0) solid solutions by solid state reaction and spark plasma sintering,” Mater. Sci. Eng. B 157, 96-100 (2009).
37. J. I. Tani, H. Kido, “Thermoelectric properties of Al-doped Mg2Si1−xSnx (x≦0.1) ,” J. Alloys Compd. 466, 335-340 (2008).
38. Peng Gao, Isil Berkun, Robert D. Schmidt, Matthew F. Luzenski, Xulu, Patricia Bordon Sarac, Eldon D. Case, and Timothy P. Hogan, “Transport and Mechanical Properties of High-ZT Mg2.08Si0.4-xSn0.6Sbx Thermoelectric Materials,” J. Electro. Mater., 43, 1790-1803 (2013).
39. 維基百科，鎂.
40. 維基百科，矽.
41. 維基百科，錫.
42. 維基百科，銻.
43. 維基百科，矽化鎂.
44. V. K. Zaitsev, M. I. Fedorov, E. A. Gurieva, I. S. Eremin, P. P. Konstantinov, A. Yu. Samunin, and M. V. Vedernikov, “Highly effective Mg2Si1-xSnx Thermoelectrics,” Phys. Rev. B 74, 045207 (2006).
45. Sin-Wook You, Il-Ho Kim, Soon-Mok Choi, and Won-Seon Seo, and Sun-Uk Kim, “Solid-State Synthesis and Thermoelectric Properties of Mg2Si1-xSnx,” J. Electro. Mater., 42, 7 (2013).
46. J. P. Heremans, V. Jovovic, E. S. Toberer, A. Saramat, K. Kurosaki, A. Charoenphakdee, S. Yamanaka and G. J. Snyder, “Enhancement of Thermoelectric Efficiency in PbTe by Distortion of the Electronic Density of
States,” Science, 321, 554 (2008).
47. C. Kittel, Introduction to Solid State Physics, 8th ed., John Wiley ＆ Sons, New York (2005).