熱壓對3-D碲化鉍電鍍膜熱電性質影響之研究

Effects of Hot-pressing on Thermoelectric Properties of 3-dimensional Bismuth Telluride Film

胡嗣祥(Hu, Sihsiang)

指導教授 ： 林昭任

國立中正大學/工學院/化學工程學系/碩士(2013年)

摘要

本實驗主要為利用聚苯乙烯球電泳於ITO(銦錫氧化物)玻璃基材製備三維結構模板，並於模板常壓電鍍碲化鉍熱電材料，進行電流輔助熱處理前先行熱壓，探討不同熱壓處理方式對熱電性質(載子濃度、遷移率、電阻率、Seebeck coefficient)與結構之影響。實驗操作分別為不同熱壓壓力、溫度、時間及不同溫度熱處理對熱電性質之影響，並探討高溫熱處理下熱電性質之變化原因。實驗結果顯示，利用固定沉積電位-0.12V電鍍，可達良好Bi2Te3化學計量係數比。實驗發現於330℃電流輔助退火時，會有Seebeck coefficient與Power factor下降之情形，而此情況估計一為在高溫下破壞碲化鉍三維結構，造成晶格缺陷，如Te空孔(vacancy)之形成作為電子施體(donor)使得載子濃度上升；二為聚苯乙烯球模板未移除完全所導致。本研究提升甲苯溶劑溫度至60℃，降低其表面張力，以利進入三維Bi2Te3結構中溶解殘留之聚苯乙烯，發現可使Bi2Te3薄膜電阻率從原本4.89mΩ-cm下降至3.58mΩ-cm。 Bi2Te3膜經熱壓後發現可使遷移率提升進而使電阻率下降，再利用電流輔助熱處理於305℃固定電流密度150mA/cm3處理5分鐘，可有效的消除晶格缺陷，使結晶性上升，其Power factor值可由為熱壓前之195.87μV/mK2上升至503.49μV/mK2。

關鍵字

熱壓法 ； 電流輔助熱處理 ； 碲化鉍 ； 熱電性質

並列摘要

This study was to investigate the preparation of three-dimensional material by electrodepositing bismuth telluride in a three-dimensional polystyrene template which was made from electrophoresis depositing polystyrene sphere on ITO (Indium Tin Oxide) glass substrate. Before electric current assisted thermal treatment process, I used hot pressing method to modify the Bi2Te3 films, which observe the difference hot press parameter’s influence of several thermoelectric properties including carrier concentration, mobility, resistivity, and Seebeck coefficient on the thermoelectric material. The experimental operation used different parameters of hot pressing pressure, temperature, time and thermal treatment temperature to enhance the power factor. By using a fixed -0.12V as the depositing potential, the stoichiometry of the bismuth telluride film met Bi2Te3. It was found that when electric current assisted thermal treatment at 330℃, the Seebeck coefficient and power factor were decrease. There are two possible reasons. Firstly: estimate at high annealing temperature cause Bi2Te3 three- dimensional structure would be destroyed. For example: the telluride trepan became electron donor to increase the carrier concentration; Secondly: there still has polystyrene in Bi2Te3 three- dimensional structure. This study showed that increase the toluene solvent temperature to reduce surface tension which used for remove polystyrene in Bi2Te3 structure. The resistivity of Bi2Te3 films were be decrease from 4.89 to 3.58 mΩ-cm. Hot pressing treatment of three-dimensional Bi2Te3 films were increase the mobility and decrease the resistivity, and then used electric current assisted thermal treatment at a current density of 150 mA/cm3 and 305℃ for 5 minutes. It could eliminate crystal lattice defects and enhance the crystallinity. The power factor increased from 195.87μW/mK2 to 503.49μW/mK2.

並列關鍵字

hot press treatment ； electric current assisted thermal treatment ； bismuth telluride ； thermoelectric properties

參考文獻

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