臺灣博碩士論文加值系統

　　熱刺激電流技術是電介質材料在研究微觀介電性質中所使用的基本方法。此技術是先將樣品在高溫以直流電場極化，再將樣品降至低溫，透過線性升溫的方式，使內部結構被系統不同陷阱能階內的空間電荷脫離，或者使取向的偶極分子發生介電鬆弛，此鬆弛能在外部形成位移電流，透過自製的外部電路設計，搭配理論的公式擬和曲線可以獲得材料內部空間電荷與取向偶極分子的活化能和儲存的電荷密度等參數。本論文研究水平排列向列型液晶的熱刺激去極化電流。在接近液晶之澄清點時，會有明顯的峰值電流產生。研究發現熱刺激去極化電流出現的峰值電流將隨著極化電壓的增加而增強。此外，若改變極化的時間，熱刺激去極化電流也將改變。更進一步發現，在升溫速率改變之下，熱刺激去極化電流峰值將會往高溫移動。

　　Thermally stimulated depolarization current technique is a fundamental method for the investigation of microscopic dielectric characteristics of dielectric materials. In this technique, when a system is applied with a DC voltage source, the energy can be stored in the forms of molecular dipoles, free charges, bonds and reorientation of polar fragments. Normally, as the field being released, the stored energy dissipates, and the system relaxes to its original state. With proper treatment, one can release the energy in the form of electrical current and extract useful information. Based on the measurement of the TSDC, in this study, the mechanism of obtaining phase transition temperatures of liquid crystals is presented. The behavior of the TSDC signal from a typical nematic cell is investigated with pre-applied voltages, polarization time and heating rate as variables.

中文摘要 i
英文摘要 ii
誌　　　謝 iv
目 錄 vi
圖　目　錄 viii
第一章　簡介 1
1.1前言 1
1.2 文獻回顧 2
1.3 研究目的 6
1.4 論文架構 6
第二章　理論 8
2.1介電質的極化 8
2.1.1 電偶極矩與位能 8
2.1.2 極化種類 10
2.2介電質的極化 14
2.3熱刺激去極化電流 18
第三章　樣品製程與實驗儀器 22
3.1材料概述與樣品製作 22
3.2實驗量測與實驗架設 24
3.2.1 液晶盒厚度量測 24
3.2.2 熱刺激去極化電流之實驗測量 24
3.2.3 熱刺激去極化電流之實驗架設 25
第四章　實驗結果與討論 31
4.1熱刺激去極化電流—以極化電壓為變數 31
4.2熱刺激去極化電流—以極化時間為變數 39
4.3熱刺激去極化電流—以升溫速率為變數 45
第五章　結論與未來展望 51
參考文獻 52
附錄一 5CB 液晶分子特性表 56
附錄二 7CB 液晶分子特性表 57
附錄三 配向劑 SE-2170 58

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