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利用水热法合成了Bi2Te3纳米粉末, 并在300500 ℃的温度范围内对其进行等离子烧结. X射线衍射测试表明制得的Bi2Te3粉末是单相的. 对于300500 ℃范围内烧结的样品, 扫描电子显微镜观察发现随着烧结温度的升高样品颗粒明显增大, 但是根据X射线衍射峰的宽度计算得到的样品晶粒大小并没有明显的变化. 正电子湮没寿命测试结果表明, 所有的样品中均存在空位型缺陷, 而这些缺陷很可能存在于晶界处. 正电子平均寿命随着烧结温度的升高而单调下降, 说明较高的烧结温度导致了空位型缺陷浓度的降低. 另外, 随着烧结温度从300 ℃升高到500 ℃, 样品的热导率从0.3 Wm-1K-1升高到了2.4 Wm-1K-1, 这表明在纳米Bi2Te3中, 空位型缺陷和热导率之间存在着密切的联系.Bismuth telluride (Bi2Te3) and its alloys are regarded as the best thermoelectric materials available nowadays at room temperature and can be well prepared by using existing technology. In this paper, Bi2Te3 nanocrystals are prepared by hydrothermal method and then treated by a spark plasma sintering (SPS) process at five temperatures of 300, 350, 400, 450 and 500 ℃ each for 5 min under a pressure of 20 MPa. X-ray diffraction (XRD) and positron annihilation spectroscopy are used to study the microstructures of the samples after SPS treatment at different temperatures. According to the XRD patterns, the diffraction peaks of the as-grown powder are consistent with those indicated in the standard card for Bi2Te3, which confirms successful synthesis of Bi2Te3 powders. Scanning electron microscope images show that the particles of all the samples take on flake-like structures, and the particle sizes increase from about 100 nm to a few m with the sintering temperature increasing from 350 to 500 ℃. This suggests significant reorganization of nanograins in sintering process, and some grains are agglomerated into larger particles. However, the grain sizes estimated from the X-ray diffraction peaks show little change in all the samples sintered at temperatures between 300-500 ℃. And most of the grains have sizes around 30 nm. Positron lifetime spectra are measured for Bi2Te3 samples sintered at different temperatures. The measurements reveal vacancy defects existing in all the sintered samples. With the increase of sintering temperature, there appears no significant change in trapped positron lifetime (2). This suggests that the defect size has no change during sintering. However, intensity I2 decreases monotonically with increasing sintering temperature, which indicates the lowering of vacancy concentration. The average positron lifetime shows a monotonous decrease with increasing sintering temperature, which indicates the recovery of vacancy defects at higher sintering temperatures. The thermal conductivity of the sample increases from 0.3 Wm-1K-1 to about 2.4 Wm-1K-1 with the sintering temperature increasing from 300 to 500 ℃. Since the lattice thermal conductivity dominates the total thermal conductivity, it can be inferred that sintering at higher temperature leads to the increase of lattice thermal conductivity. According to the positron annihilation lifetime result, the vacancy defects in the interface region gradually recover after sintering at higher temperatures. This shows good correlation with the increase of lattice thermal conductivity, indicating that vacancy-type defects are effective phonon scattering centers for Bi2Te3.
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Keywords:
- Bi2Te3 /
- positron /
- vacancy-type defects /
- thermal conductivity
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[36] Yoon S, Kwon O J, Ahn S, Kim J Y, Koo H, Bae S H, Cho J Y, Kim J S, Park C 2013 J. Electron. Mater. 42 3390
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[1] Zhang F, Zhu H T, Luo J, Liang J K, Rao G H, Liu Q L 2010 Acta Phys. Sin. 59 7232 (in Chinese) [张帆, 朱航天, 骆军, 梁敬魁, 饶光辉, 刘泉林 2010 59 7232]
[2] Wang Z C, Li H, Su X L, Tang X F 2011 Acta Phys. Sin. 60 027202 (in Chinese) [王作成, 李涵, 苏贤礼, 唐新峰 2011 60 027202]
[3] Huo F P, Wu R G, Xu G Y, Niu S T 2012 Acta Phys. Sin. 61 087202 (in Chinese) [霍凤萍, 吴荣归, 徐桂英, 牛四通 2012 61 087202]
[4] Ji X, Zhang B, Tritt T M, Kolis J W, Kumbhar A 2007 J. Electron. Mater. 36 721
[5] Slack G A, Tsoukala V G 1994 J. Appl. Phys. 76 1665
[6] Callaway J, von Baeyer H C 1960 Phys. Rev. 120 1149
[7] Klemens P G 1955 Proc. Phys. Soc. A 68 1113
[8] Abeles B 1963 Phys. Rev. 131 1906
[9] Pei Y Z, Morelli D T 2009 Appl. Phys. Lett. 94 122112
[10] Kurosaki K, Matsumoto H, Charoenphakdee A, Yamanaka S, Ishimaru M, Hirotsu Y 2008 Appl. Phys. Lett. 93 012101
[11] Yu C, Scullin M L, Huijben M, Ramesh R, Majumdar A 2008 Appl. Phys. Lett. 92 191911
[12] Wang Y, Li F, Xu L X, Sui Y, Wang X J, Su W H, Liu X Y 2011 Inorg. Chem. 50 4412
[13] Plirdpring T, Kurosaki K, Kosuga A, Ishimaru M, Harnwunggmoung A, Sugahara T, Ohishi Y, Muta H, Yamanaka S 2011 Appl. Phys. Lett. 98 172104
[14] Zhu G H, Lan Y C, Wang H, Joshi G, Hao Q, Chen G, Ren Z F 2011 Phys. Rev. B 83 115201
[15] Wiedigen S, Kramer T, Feuchter M, Knorr I, Nee N, Hoffmann J, Kamlah M, Volkert C A, Jooss C 2012 Appl. Phys. Lett. 100 061904
[16] Levander A X, Tong T, Yu K M, Suh J, Fu D, Zhang R, Lu H, Schaff W J, Dubon O, Walukiewicz W, Cahill D G, Wu J 2011 Appl. Phys. Lett. 98 012108
[17] Liu Y, Zhao L D, Liu Y C, Lan J L, Xu W, Li F, Zhang B P, Berardan D, Dragoe N, Lin Y H, Nan C W, Li J F, Zhu H M 2011 J. Am. Chem. Soc. 133 20112
[18] Kato A, Yagi T, Fukusako N 2009 J. Phys.: Condens. Matter 21 205801
[19] Park C H, Kim Y S 2010 Phys. Rev. B 81 085206
[20] Hashibon A, Elsässer C 2011 Phys. Rev. B 84 144117
[21] Alam H, Ramakrishna S 2013 Nano Energy 2 190
[22] Son J S, Choi M K, Han M K, Park K, Kim J Y, Lim S J, Oh M, Kuk Y, Park C, Kim S J, Hyeon T 2012 Nano Lett. 12 640
[23] Fu J P, Song S Y, Zhang X G, Cao F, Zhou L, Li X Y, Zhang H J 2012 Crys. Eng. Comm. 14 2159
[24] Wang X Z, Yang Y M, Zhu L L 2011 J. Appl. Phys. 110 024312
[25] Termentzidis K, Pokropivny A, Woda M, Xiong S Y, Chumakov Y, Cortona, Volz S 2012 J. Phys.: Conference Series 395 012114
[26] Wang S J, Chen Z Q, Wang B, Wu Y C, Fang P F, Zhang Y X 2008 Applied Positron Spectroscopy (Wuhan: Hubei Science and Technology Press) pp18-19 (in Chinese) [王少阶, 陈志权, 王波, 吴奕初, 方鹏飞, 张永学 2008 应用正电子谱学 (湖北科学技术出版社)第18–19页]
[27] Dutta S, Chattopadhyay S, Jana D 2006 J. Appl. Phys. 100 114328
[28] Chakrabarti M, Dutta S, Chattapadhyay S, Sarkar A, Sanyal D, Chakrabarti A 2004 Nanotechnology 15 1792
[29] Tuomisto F, Ranki V, Saarinen K, Look D C 2003 Phys. Rev. Lett. 91 205502
[30] Dutta S, Chakrabarti M, Chattopadhyay S, Jana D, Sanyal D, Sarkar A 2005 J. Appl. Phys. 98 053513
[31] Chakrabarti M, Bhowmick D, Sarkar A, Chattopadhyay S, Dechoudhury S, Sanyal, Chakrabarti A 2005 J. Mater. Sci. 40 5265
[32] Ni H L, Zhu T J, Zhao X B 2005 Mater. Sci. Eng. B 117 119
[33] Takashiri M, Tanaka S, Hagino H, Miyazaki K 2012 J. Appl. Phys. 112 084315
[34] Kirkegaard P, Pederson N J, Eldrup M 1989 Riso Report M 2740, Risφ National Laboratory, DK-4000 Roskilde, Denmark
[35] Zheng X J, Zhu L L, Zhou Y H, Zhang Q J 2005 Appl. Phys. Lett. 87 242101
[36] Yoon S, Kwon O J, Ahn S, Kim J Y, Koo H, Bae S H, Cho J Y, Kim J S, Park C 2013 J. Electron. Mater. 42 3390
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