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Nanocrystalline bulk materials n-type (Bi1–xTbx)2(Te0.9Se0.1)3 (x = 0, 0.002, 0.004, 0.008) are fabricated by high pressure sintering (HPS) technique. The HPS samples are then annealed for 36 h in a vacuum at 633 K. The phase compositions and crystal structure of HPS sample are analyzed by X-ray diffraction. The microscopic morphology of HPS sample is observed by field-emission scanning electron microscopy. The electric conductivity, Seebeck coefficient, and thermal conductivity of the HPS sample and annealed sample are measured in a temperature range from room temperature to 473 K. The effects of Tb content on crystal structure and thermoelectric properties of the sample are systematically studied. The results show that HPS sample consists of nanoparticles. With the increase of content of Tb, the cell volume increases. Besides, the power factor increases but thermal conductivity decreases through doping Tb, thus the optimal figure of merit (ZT) value increases. The Tb doping amount of x = 0.004 is an optimal doping amount. At this doping amount, the maximum ZT of 0.29 is achieved, which is enhanced by 32% compared with the ZT value of undoped sample. The thermoelectric performance can be improved significantly by annealing. The thermal conductivity of the annealed sample with x = 0.004 is 0.9 W·m–1·K–1 at 373 K, decreased by 23% compared with the thermal conductivity of HPS sample. Consequently, the ZT value of annealed sample is significantly higher than that of HPS sample. The maximum thermoelectric ZT of 0.99 is achieved for annealed sample with x =0.004 at 373 K. Furthermore, it is worthwhile to note that this annealed sample possesses a ZT value larger than 0.8 when the temperature is higher than 323 K.
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Keywords:
- high pressure sintering /
- Tb-doped /
- n-type Bi2Te2.7Se0.3 /
- thermoelectric properties
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图 1 高压烧结样品(Bi1–xTbx)2(Te0.9Se0.1)3 (x = 0, 0.002, 0.004, 0.008)的XRD图谱
Figure 1. XRD patterns of the (Bi1–xTbx)2(Te0.9Se0.1)3 (x = 0, 0.002, 0.004, 0.008) HPS samples.
图 2 Tb掺杂量为x = 0.004的高压烧结样品(Bi1–xTbx)2(Te0.9Se0.1)3的FE-SEM照片
Figure 2. FE-SEM of the (Bi1–xTbx)2(Te0.9Se0.1)3 HPS sample (x = 0.004).
图 3 Tb不同掺杂量的高压烧结样品的电导率随温度的变化
Figure 3. The temperature dependences of electrical conducti-vities for the HPS samples doped with different Tb contents.
图 4 Tb不同掺杂量的高压烧结样品的Seebeck系数随温度的变化
Figure 4. The temperature dependence of Seebeck coefficient for the HPS samples doped with different Tb contents.
图 5 Tb不同掺杂量的高压烧结样品的功率因子随温度的变化
Figure 5. Temperature dependence of power factor for the HPS samples doped with different Tb contents.
图 6 高压烧结样品的热导率随温度变化 (a) 未掺杂样品; (b) 掺杂量为x = 0.004的样品
Figure 6. Temperature dependence of thermal conductivities for the HPS samples: (a) Tb-free sample (x = 0); (b)Tb-doped sample (x = 0.004).
图 7 未掺杂及掺杂量为x = 0.004的样品的ZT值随温度变化的关系
Figure 7. Temperature dependence of the figure of merit ZT for the Tb-free HPS sample and Tb-doped HPS sample with x = 0.004.
图 8 Tb不同掺杂量的退火样品的电导率随温度的变化
Figure 8. Temperature dependence of electrical conductivity for the annealed samples doped with different Tb contents.
图 9 Tb不同掺杂量的退火样品的Seebeck系数随温度的变化
Figure 9. Temperature dependence of Seebeck coefficient for the annealed samples doped with different Tb contents.
图 10 Tb不同掺杂量的退火样品的功率因子随温度的变化
Figure 10. Temperature dependence of power factor for the annealed samples doped with different Tb contents.
图 11 Tb掺杂量为x = 0.004的退火样品的热导率随温度变化的关系
Figure 11. Temperature dependence of thermal conductivity for the annealed sample with x = 0.004.
图 12 未掺杂及掺杂量为x = 0.004的退火样品的ZT值随温度变化的关系
Figure 12. Temperature dependence of the figure of merit ZT for the Tb-free annealed sample and Tb-doped annealed sample with x = 0.004.
表 1 (Bi1–xTbx)2(Te0.9Se0.1)3 (x = 0, 0.002, 0.004, 0.008)样品的晶格常数
Table 1. Lattice constants of (Bi1–xTbx)2(Te0.9Se0.1)3 (x = 0, 0.002, 0.004, 0.008).
Sample x = 0 x = 0.002 x = 0.004 x = 0.008 a/Å 4.3748 4.38086 4.38205 4.38468 c/Å 30.3456 30.34931 30.35013 30.35389 V/Å3 502.96 504.41 504.70 505.37 
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表 2 (Bi1–xTbx)2(Te0.9Se0.1)3样品的载流子浓度和迁移率
Table 2. Carrier concentrations and mobility of (Bi1–xTbx)2(Te0.9Se0.1)3 samples.
Samples Carrier concentrationn/1019 cm–3 Carrier mobility μ/cm2·V–1·s–1 x = 0 (HPS) 1.92 197.98 x = 0.002 (HPS) 3.95 133.53 x = 0.004 (HPS) 6.51 95.31 x = 0.008 (HPS) 7.17 92.39 x = 0.004 (Annealed) 1.36 599.34 x = 0.008 (Annealed) 1.77 491.17
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[1] DiSalvo F J 1999 Science 285 703
Google Scholar
[2] Bell L E 2008 Science 321 1457
Google Scholar
[3] Wu D, Zhao L D, Hao SQ, Jiang Q K, Zheng F S, Doak J W, Wu H J, Chi H, Gelbstein Y, Uher C, Wolverton C, Kanatzidis M, He J Q 2014 J. Am. Chem. Soc. 136 11412
Google Scholar
[4] Zhou Y M, Zhao L D 2017 Adv. Mater. 29 1702676
Google Scholar
[5] Chang C, Wu M H, He D S, Pei Y L, Wu C F, Wu X F, Yu H L, Zhu F Y, Wang K D, Chen Y, Wang K D, Huang L, Li J F, He J Q, Zhao L D 2018 Science 360 778
Google Scholar
[6] Snyder G J, Toberer E S 2008 Nat. Mater. 7 105
Google Scholar
[7] Wang Z L, Akao T, Onda T, Chen Z C 2017 Scripta Mater. 136 111
Google Scholar
[8] Pan Y, Wei T R, Cao Q, Li J F 2015 Mater. Sci. Eng. B 197 75
Google Scholar
[9] Jiang C P, Fan X A, Feng B, Hu J, Xiang Q S, Li G Q, Li Y W, He Z 2017 J. Alloys Compd. 692 885
Google Scholar
[10] 王善禹, 谢文杰, 李涵, 唐新峰 2010 59 8927
Google Scholar
Wang S Y, Xie W J, Li H, Tang X F 2010 Acta Phys. Sin. 59 8927
Google Scholar
[11] Rong Z Z, Fan X A, Yang F, Cai X Z, Han X W, Li G Q 2016 Mater. Res. Bull. 83 122
Google Scholar
[12] Xu GY, Niu ST, Wu XF 2012 J. Appl. Phys. 112 073708
Google Scholar
[13] Yu F R, Xu B, Zhang J J, Yu D L, He J L, Liu Z Y, Tian Y J 2012 Mater. Res. Bull. 47 1432
Google Scholar
[14] May A F, Singh D J, Snyder G J 2009 Phys. Rev. B 79 153101
Google Scholar
[15] Zhang Y H, Zhu T J, Tu J P, Zhao X B 2007 Mater. Chem. Phys. 103 484
Google Scholar
[16] 徐桂英, 邹平, 王松, 张艳华 2015 稀有金属材料与工程 44 950
Xu G Y, Zou P, Wang S, Zhang Y H 2015 Rare Metal Mat. Eng. 44 950
[17] Sharp J W, Poon S J, Goldsmid H J 2001 Phys. Status Solidi A 187 507
Google Scholar
[18] Kim DH, MitaniT 2005 J. Alloys Compd. 399 14
Google Scholar
[19] Slack GA, Hussain MA 1991 J. Appl. Phys. 70 2694
Google Scholar
[20] Wang SY, Xie WJ, Li H, Tang X F 2011 Intermetallics 19 1024
Google Scholar
[21] Wu F, Song H Z, Jia J F, Gao F, Zhang Y J, Hu X 2013 Phys. Status Solidi A 210 1183
Google Scholar
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