摻雜效應和晶體結構對Bi-Sb-Te化合物熱電傳輸特性影響之研究

Effects of doping and crystallographic texture on thermoelectric transport properties of Bi-Sb-Te compounds

蘇令杰(Ling-Chieh Su)

指導教授 ： 廖建能

國立清華大學/工學院/材料科學工程學系/碩士(2014年)

https://doi.org/10.6843/NTHU.2014.00353

摘要

熱電發電技術為當今備受矚目的綠能相關發展技術之一，熱電材料本身能進行熱能和電能的可逆轉換，一般在工廠、汽車廢熱回收和致冷元件都能見其應用。本實驗主要研究之材料系統為碲化鉍系化合物，其在室溫範圍下擁有良好的熱電優值，且已成功運用在一些熱電發電元件與致冷元件。若能有效提升其熱電特性，將可進一步增加熱電發電系統的轉換效率，達到節能減碳的目標。本研究係以中國鋼體股份有限公司所提供的碲化鉍系化合物作為研究基材，各別將銀原子與銅原子以不同方式摻雜到熱電材料中，並探討以區域熔煉(zone melting)晶棒、冷壓(cold press)和熱壓(hot press)三種製程方式所製備材料之微結構與熱電傳輸性質。實驗結果發現，區域熔煉法製備的晶棒和手磨粉末冷壓試片具有顯著的晶體優選方向性，然而球磨粉末冷壓試片及熱壓試片則無明顯晶體優選方向。基於此晶體結構方向性上的差異，這些由不同方法所製備試片的電性量測結果亦呈現非均向性。最後，透過不同方式分別將銀原子與銅原子摻雜到碲化鉍系材料中，再以自製掃描式Seebeck電壓量測機台進行量測，發現在材料可觀察到一較不尋常的熱電效應，顯示在特定製程條件下有機會提升材料的熱電特性。本研究將比較不同製程所製備碲化鉍系化合物中銀原子與銅原子的擴散特性，及其對材料熱電傳輸性質的影響。

關鍵字

熱電材料 ； 摻雜 ； 碲化鉍 ； 擴散 ； 塊材

並列摘要

Thermoelectric power generation that converts thermal energy into electrical energy has been considered to be a promising green technology. Bismuth telluride based compounds have reasonably high thermoelectric figure-of-merit at room temperature regime. They have been widely employed in the applications of waste-heat recovery and thermoelectric refrigeration. If the thermoelectric properties of bismuth telluride compounds can be improved further, it would possible to increase the conversion efficiency of thermoelectric devices and contribute to the reduction of CO2 emission. In the study, bismuth telluride based raw materials are provided by the China Steel Corporation. Three different processing methods including zone-melting, cold press and hot press were used to prepare the Bi-Sb-Te compounds. The microstructure and thermoelectric transport properties of these materials with different doping processes are investigated. The samples prepared by zone melting and cold-press with hand-crushed powders have shown preferred crystallographic texture, while those by hot-press and cold press with ball-milled powders have no preferred texture. The anisotropic crystallographic texture leads to anisotropic transport properties. In addition, the samples with special Ag and Cu doping profiles have shown an unusual thermoelectric effect measured by a home-made scanning Seebeck system. The results suggest that it is possible to change the transport properties of Bi-Sb-Te based compounds through special fabrication process. The diffusion and thermoelectric properties of Bi-Sb-Te compounds with different fabrication processes are discussed in this research.

並列關鍵字

thermoelectrics ； doping ； bismuth telluride ； diffusion ； bulk

參考文獻

[31] H. H. Huang, M. P. Lu, C. H. Chiu, L. C. Su, C. N. Liao, J. Y. Huang, H. L. Hsieh, Applied Physics Letters 103, 163903 (2013).

[28] X. A. Fan, J. Y. Yang, W. Zhu, S. Q. Bao, X. K. Duan, C. J. Xiao and K. Li1, Journal of Physics D-Applied Physics 40, 5727–5732 (2007).

[9] X. A. Fan, J. Y. Yang, R. G. Chen, H. S. Yun, W. Zhu, S. Q. Bao, and X. K. Duan, Journal of Physics D-Applied Physics 39, 740 (2006).

[26] W. J. Xie, X. F. Tang, Y. G. Yan, Q. J. Zhang, and T. M. Tritt, Applied Physics Letters 94, 102111 (2009).

[22] Y. S. Hor, D. Qu, N. P. Ong and R. J. Cava, Journal of Physics: Condensed Matter 22, 375801 (2010).