應用超臨界二氧化碳電鍍碲硒化鉍熱電薄膜之研究

Studies of Electroplating Bismuth-Telluride-Selenium Thermoelectrical Film in the Supercritical Carbon Dioxide

黃盟議(Huang, Mengyi)

指導教授 ： 林昭任

國立中正大學/工學院/化學工程學系/碩士(2012年)

摘要

本研究為利用超臨界二氧化碳電鍍(SC-CO2)熱電材料碲硒化鉍薄膜於不鏽鋼基材上並探討之特性變化。首先實驗結果顯示Se濃度於10-3M時，其Power factor值將有極大值，並將此薄膜藉由EDS分析發現，此薄膜之Se化學計量約為0.3~0.41之間(依照Bi2Te3-ySey換算)。之後設定實驗操作壓力從0.1~20.4MPa、溫度35℃、固定轉速350rpm、沉積電位為-0.04V與-0.06V vs. Ag/AgCl。結果發現在超臨界二氧化碳電鍍下，碲硒化鉍為多晶結構，於未添加界面活性劑下電鍍，鍍膜呈現穀粒狀結構；但添加OGME與FSN-100界面活性劑時，鍍膜則呈現針狀結構，因添加界面活性劑會使沉積電流皆小於未添加界面活性劑，進而導致添加界面活性劑之鍍膜中的Te+Se含量大於未添加界面活性劑者。且發現晶粒尺寸會隨著操作壓力的增加而下降，於添加FSN-100界面活性劑、操作壓力為20.4MPa時，其(015)晶面之晶粒尺寸可縮小至20.1nm。在熱電性質分析中，可觀察到載子濃度會隨著晶粒尺寸下降而減少；但Seebeck係數與電阻率則會隨著晶粒尺寸下降而增加，主因為晶粒尺寸下降而造成晶界能障變多而造成。其中Power factor值於添加入FSN-100界面活性劑且操作壓力為17MPa時，可提升至94.43(μW/mK2)。

關鍵字

超臨界電鍍 ； 熱電材料 ； 碲硒化鉍

並列摘要

This study was to investigate the characteristics of thermoelectric films (Bismuth-Telluride-Selenium) electroplated on stainless steel under supercritical carbon dioxide. First, the experimental results showed that the power factor of Bi2Te3-ySey reached maximum when the concentration of selenium is 10-3M. And the films measured by EDS, the stoichiometry of selenium was 0.3~0.41 based on Bi2Te3-ySey. The electroplating pressure was from 0.1 to 20.4MPa at 35℃ and agitated at a speed of 350rpm, and the Bismuth-Telluride-Selenium films was prepared at -0.04V and -0.06V v.s. Ag/AgCl. The Results showed that the Bismuth-Telluride-Selenium films were polycrystalline structure. Without adding surfactant, the morphologies of BixTe3-ySey films were wheat-shaped structures, whereas adding the surfactant of OGME and FSN-100, the BixTe3-ySey films consisted with needle-like structures. It was because adding surfactant caused less current of deposition than that without adding surfactant, so led the atomic percent of Te plus Se of adding surfactant greater than without adding surfactant. It was also found that the grain size decreased with the increasing operating pressure, while the grain size of (015) plane was reached to minimum of 20.1nm when FSN-100 was added to the electrolyte as the surfactant and the operating pressure was 20.4MPa. In the analysis of the thermoelectric properties, it was discovered that the carrier concentration decreased with the decreasing grain size, but the Seebeck coefficient and resistivity were increased with the decreasing grain size. The major reason was because that the grain size decreased leading to the increasing of grain boundary barrier. In the study, the power factor reached to maximum of 94.43(μW/mK2) while the surfactant FSN-100 was added to the electrolyte and the operating pressure was 17MPa.

並列關鍵字

Supercritical Carbon Dioxide ； Thermoelectric material ； Bismuth-Telluride-Selenium

參考文獻

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