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Zinc oxide (ZnO) has attracted increasing attention as one of the most promising n-type thermoelectric materials. Although ZnO has been screened for high power factor, the ZT results were discouraging for its high thermal conductivity. Preparing nanocomposite is an effective way to reduce the thermal conductivity. The Ag-ZnO nanocomposites were synthesized by means of sol-gel method and their thermoelectric properties were investigated. Their XRD pattern and SEM miro graphs show that Ag nanoparticles are mainly lecated at the grain boundary of ZnO. Increasing Ag content leads to a significant decrease in absolute value of Seebeck coefficient (|S|). The electrical conductivity increases with increasing Ag content, while the thermal conductivity of Ag-ZnO nanocomposites is much lower than the bulk ZnO sample. The highest ZT (0.062) is found for 7.5 mol% Ag@ZnO nanocomposite at 750 K, thirty-five times of that of bulk ZnO. Since the Ag-ZnO junction leads to charge redistribution, the deflexed energy band obtained for ZnO should facilitate the electron transfer across the interface and thus accelerates the mobility of charge carriers. Thus increasing mobility of charge carriers would lead to the increase in electrical conductivity and a decrease in Seebeck coefficient. The difference of thermal conductivity comes from the lattice thermal conductivity. Due to the high density of interfaces and grain boundaries present in the nanocomposites, the scattering of phonons across a broad wavelength spectrum is enhanced. This suppresses the lattice thermal conductivity of the nanocomposites significantly.
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Keywords:
- thermolelectric materials /
- ZnO /
- nanocomposite /
- thermal conductivity
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[2] Cao Y Q, Zhao X B, Zhu T J, Zhang X B, Tu J P 2008 Appl. Phys. Lett. 92 143106
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[16] Bergman D J, Imry Y 1977 Phys. Rev. Lett. 39 1222
[17] Barber W C, Ye F, Belanger D P 2004 Phys. Rev. B 69 024409
[18] Meir Y 1999 Phys. Rev. Lett. 83 3506
[19] Reddy P, Jang S Y, Segalman R A, Majumdar A 2007 Science 315 1568
[20] Liu Y S, Chen Y R, Chen Y C 2009 ACS. Nano. 3 3497
[21] Pei Y Z, Andrew A, Snyder G J 2011 Adv. Energy Mater. 1 291
[22] Kim D, Kim Y, Choi K, Grunlan J C, Yu C 2010 ACS. Nano. 4 513
[23] Meng C Z, Liu C H, Fan S S 2010 Adv. Mater. 22 535
[24] Zhang R Z, Chen W Y, Yang L N 2012 Acta Phys. Sin. 61 187201 (in Chinese) [张睿智, 陈文灏, 杨璐娜 2012 61 187201]
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[1] Zhou M, Li J F, Kita T 2008 J. Am. Chem. Soc. 130 4527
[2] Cao Y Q, Zhao X B, Zhu T J, Zhang X B, Tu J P 2008 Appl. Phys. Lett. 92 143106
[3] Zhang H, Luo J, Zhu H T, Liu Q L, Liang J K, Rao G H 2012 Acta Phys. Sin. 61 086101 (in Chinese) [张贺, 骆军, 朱航天, 刘泉林, 梁敬魁, 饶光辉 2012 61 086101]
[4] Shi X, Chen L, Yang J, Meisner G P 2004 Appl. Phys. Lett. 84 2301
[5] 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]
[6] Wu Z H, Xie H Q, Zeng Q F, Yin M 2012 J. Optoelectron. Adv. Mater. 14 262
[7] Ioffe A F, Goldsmid H J 1957 Semiconductor Thermoelements and Thermoelectric Cooling (1st Edn.) (London:Inforesearch) P72
[8] Ohtaki M, Tssubota T, Eguchi K, Arai H 1996 J. Appl. Phys. 79 1816
[9] Ong K P, Singh D J, Wu P, 2011 Phys. Rev. B 83 115110
[10] Jood P, Mehta R J, Zhang Y L, Peleckis G, Wang X, Siegel R W, Tasciuc T B, Dou S X, Ramanath G 2011 Nano. Lett. 11 4337
[11] Ohtaki M, Maehara S, Shige S 2003 Proc. 22th Int. Conf. Thermoelectrics (France) 171
[12] Feng X M, Cheng Y F, Ye C, Ye J S, Peng J Y, Hu J Q 2012 Mater. Lett. 79 205
[13] Karunakaran C, Rajeswari V, Gomathisankar P, Mater 2011 Sci. in Semicon. Proc. 14 133
[14] Lin D D, Wu H, Qin X L, Pan W 2009 Appl. Phys. Lett. 95 112104
[15] Houng B, Huang C J 2006 Surf. Coat. Technol. 201 3188
[16] Bergman D J, Imry Y 1977 Phys. Rev. Lett. 39 1222
[17] Barber W C, Ye F, Belanger D P 2004 Phys. Rev. B 69 024409
[18] Meir Y 1999 Phys. Rev. Lett. 83 3506
[19] Reddy P, Jang S Y, Segalman R A, Majumdar A 2007 Science 315 1568
[20] Liu Y S, Chen Y R, Chen Y C 2009 ACS. Nano. 3 3497
[21] Pei Y Z, Andrew A, Snyder G J 2011 Adv. Energy Mater. 1 291
[22] Kim D, Kim Y, Choi K, Grunlan J C, Yu C 2010 ACS. Nano. 4 513
[23] Meng C Z, Liu C H, Fan S S 2010 Adv. Mater. 22 535
[24] Zhang R Z, Chen W Y, Yang L N 2012 Acta Phys. Sin. 61 187201 (in Chinese) [张睿智, 陈文灏, 杨璐娜 2012 61 187201]
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