利用電流輔助熱壓與退火對電沉積碲化鉍系於其晶種層之熱電性質研究

Effects of Current-Assisted Hot Pressing and Annealing on Thermoelectric Properties of Bismuth-Telluride-based Film Electrodeposited on Its Seeding Layer

游福全(FU-CHIUAN YOU)

指導教授 ： 林昭任

國立中正大學/工學院/化學工程學系/碩士(2016年)

摘要

本實驗於碲化鉍系晶種層上利用電化學沉積法搭配聚苯乙烯球模板沉積出具有三維結構的熱電材料，再經由不同後處理方式對鍍膜熱電性質的影響。電鍍方式採定電位沉積法，固定溫度30oC、轉速300rpm，參考電極為Ag/AgCl, KCl3m。實驗操作方面分別為以不同的沉積電位來找尋最佳理想組成、探討移除聚苯乙烯球模板的時間對熱電性質影響、不同後處理方式對熱電性質的改善。
實驗結果顯示，P-type沉積電位為-0.45V時，沉積鍍膜的組成為Bi0.4Sb1.4Te3.2，與理想組成Bi0.5Sb1.5Te3最接近;而N-type在沉積電位-0.32V下的鍍膜組成為Bi2.1Te2.6Se0.3，與理想組成Bi2Te2.7Se0.3最接近。而聚苯乙烯球模板若移除不完全，則會破壞內部碲化鉍系三維結構，造成電阻率上升。後處理方面，由於試片經過熱壓和退火及通電處理後，使得原始鬆散結構變得緻密進而降低電阻率；另一方面也讓原子重新排列再結晶並消除結構內部晶格缺陷使得載子濃度降低並提高載子遷移率。在熱電性質的部分，Power factor最大值出現於以溫度290oC、壓力195kgf/cm2、電流密度1600 A/cm2下進行電流輔助熱壓處理時，P-type功率因子為1496.12μW/K2m;N-type功率因子為1073.87μW/K2m。

關鍵字

電沉積 ； 聚苯乙烯球模板 ； 電流輔助熱壓 ； 碲化鉍系晶種層

並列摘要

This study used potentiostatic electrodeposition technique to prepare three-dimensional Bi2Te3-based thin films within nanoscale polystyrene templates, which were premade on the top of P-type or N-type seeding layer via blade coating method. Processing temperature were fixed to 30oC and agitated with a speed of 300rpm during electroplating. To enhance thermoelectric properties, a current assisted hot pressing and annealing method was applied to films after electroplating. The different electrodeposition potential, templates removed time and after-treatment methods has been chosen in order to investigate the effects of parameters on thermoelectrical properties.
The results showing that P-type bismuth-antimony-telluride and N-type bismuth-telluride-selenium thin films, which were deposited at a constant potential -0.45V and -0.32V vs. Ag/AgCl, KCl3m were the closest one to the ideal composition. It’s also found that if there were any polystyrene templates been left over the films will drop thermoelectrical properties dramatically. In after-treatments aspect, due to specimen after hot pressing and annealing and current assisted hot pressing treatment, that the original loose structure becomes densified thus reducing resistivity; the other hand atoms to rearrange during process which will reduce the lattice defects so that carrier concentration is reduced to improve the carrier mobility. In terms of performance, the maximum power factor in this study is 1496.12μW/K2m for P-type bismuth-antimony-telluride and is 1073.87μW/K2m for N-type bismuth-telluride-selenium. Both samples were prepared under the conditions of 290oC and 195kgf/cm2 and current density 1600A/cm2.

並列關鍵字

electrodeposition ； Polystyrene template ； Current-Assisted Hot Pressing ； Bi2Te3-based Seeding Layer

參考文獻

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