臺灣博碩士論文加值系統

本論文是對弛豫鐵電單晶PMN-xPT (x=24、31、33)沿晶體[001]和[111]方向進行介電常數隨溫度變化的研究， PMN-24%PT晶體在385 K附近有一個彌散相變，PMN-31%PT晶體在398 K附近有一個彌散相變，PMN-33%PT晶體在350 K附近有一個彌散相變， 在419 K附近時有一個一階鐵電相變。 而在上述相變點附近都有明顯的熱滯現象， 顯示那些相變都屬於一階相變。
PMN-24%PT晶體、PMN-31%PT晶體和PMN-33%PT晶體在溫度高於居里點(Curie point)時， 不像一般的鐵電晶體遵循居里魏斯(Curie-Weiss)公式 ，它的介電常數符合下列公式 ， 它們的γ值隨著PT成分的增加而降低， 但是和頻率的相關不大。
從PMN-33%PT晶體的實部介電常數 和頻率的關係， 證實了在390 K以下PMN-33%PT晶體系統有一個電偶極的鬆弛過程(relaxation process)。 我們也同時計算了此鬆弛過程中的活躍能(activation energy)， 及 "attempt frequency"。

Dielectric permittivities along the [001] and [111] direction have been measured as a function of temperature for relaxor-ferroelectric single-crystal (Pb(Mg1/3Nb2/3)O3)1-x (PbTiO3)x (PMN-xPT) for x=24, 31, and 33. For PMN-24%PT, PMN-31%PT, and PMN-33%PT a so-called diffuse phase transition was observed near 385 K, 398 K, and 350K, respectively. PMN-33%PT shows a sharp ferroelectric phase transition near 419 K. The nature of the thermal hysteresis for the dielectric permittivity confirms that those transitions are all first-order type.
When the temperature is higher than the Curie point, unlike the normal ferroelectric single-crystal obeys Curie-Weiss formula, PMN-24%PT, PMN-31%PT, and PMN-33%PT agree with the following equation , the parameter decreases with increasing PT composition in the crystal . Also, no correlation between the parameter and measuring frequency was found.
The frequency-dependent dielectric data of PMN-33%PT confirm the existence of an electric dipolar relaxation process below 390 K. The activation energy , and attempt frequency corresponding to this relaxation process are also calculated.

目錄
中文摘要
英文摘要
目錄
1 簡介 1
1.1 弛豫鐵電晶體的性質 1
1.2 鐵電材料的應用 4
2 基礎理論 6
2.1 實數介電常數 6
2.2 複數介電常數 11
2.3 實驗數據計算 12
2.4 活躍能 13
2.5 藍道相變理論 15
2.5.1 二階相變 15
2.5.2 一階相變 16
3 實驗過程 18
3.1 樣品製備 18
3.2 實驗方法 18
4 結果與討論 22
5 結論 48
參考文獻 49

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