鐵電晶體在力電耦合下之遲滯表現與電域旋轉: 實驗與模擬

Hysteresis and domain switching behaviors of ferroelectric crystals under electromechanical loading: experiments and modeling

葉潔樺(Jay-Hua Yeh)

指導教授 ： 謝宗霖

國立臺灣大學/工學院/材料科學與工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01719

摘要

本篇論文主軸分為實驗與理論模擬(Modeling)兩大部分。 在實驗部分可細分成力電耦合實驗(Electromechanical loading)與即時影像觀察實驗(In-situ observation)兩種，力電耦合實驗是同時以交互電場和單軸向壓應力作用於鈦酸鋇單晶(Barium Titanate Single Crystal)與多晶PLZT(Polycrystalline Lanthanum-Doped Lead Zirconate Titanate)兩種塊材之上以得到電滯曲線與蝴蝶曲線之實驗，於鈦酸鋇單晶與PLZT中，我們分別可使其應變量達0.45%與0.23%，此時所施加之單軸向壓應力則分別是2.7MPa與3.2MPa，交互電場為±1.25MVm-1，我們並由這些數據來解釋應力誘發90°晶域旋轉(Domain switching)以造成應變量大幅上升的行為，同時，由晶域觀察所得之影像我們可以得知所施加之電場並不一定能使偶極完全朝同一方向，使得應變值與理論值有所差距；而即時影像觀察實驗乃利用光學顯微鏡配合偏光片(Polarizer)觀察鈦酸鋇單晶與PLZT在正負交互電場作用下晶域即時之變化情況，除了可觀察到晶域於旋轉一開始時產生類氣泡狀(Bubble-like)且狀似成核之變化，還能觀察到在電場作用過程時晶域sweeping的現象，此外利用晶域變化的情況，我們定義出90°晶域旋轉起始點與結束點之矯頑電場( 與 )大小，我們得到鈦酸鋇單晶之 為0.06MVm-1、 為0.25MVm-1，而PLZT之 與 則分別是0.15 MVm-1與0.37 MVm-1。
在理論模擬的部分，則承續上述實驗之結果與數值來配合理論發展出一套以能量極小化為概念的模型，並模擬晶域旋轉的行為以驗證與比較力電耦合下電滯曲線與蝴蝶曲線所得之結果。

關鍵字

力電耦合 ； 即時影像觀察 ； 鈦酸鋇單晶 ； PLZT ； 晶域旋轉 ； 模擬

並列摘要

This thesis is consisted of two sections: electromechanical loading experiments on BaTiO3 (Barium titanate) single crystals and PLZT (Lanthanum-Doped Lead Zirconate Titanate) polycrystals and simulations of electromechanical behaviors of BaTiO3 single crystals. For the electromechanical loading experiments a cyclic electric field and a uniaxial compressive stress were applied on to BaTiO3 single crystals and PLZT polycrystals (5×5×2mm3) to obtain their hysteresis and butterfly curves. About 0.45% of strain is obtained for the BaTiO3 single crystal under a compressive stress of 2.7MPa and a cyclic electric field of ±1.25MVm-1. About 0.23% of strain is obtained for the PLZT polycrystal under a compressive stress of 3.2MPa and a cyclic electric field of ±1.25MVm-1. It is concluded that the stress-induced 90° domain switching increases the level of strain output. It is found that the electric field of ±1.25MVm-1 is unable to produce one single domain in the BaTiO3 single crystal; this unsaturation provides a condition for “polarization-free” straining. Optical microscopy with polarizers are adopted to observe the motion of domain switching within the BaTiO3 single crystal and the PLZT during cyclic electric field loading. The bubble-like patterns are observed at the beginning of 90° switching in the BaTiO3 single crystal. From the observed patterns, the starting and the finishing electric fields of 90° domain switching are defined. and for the BaTiO3 single crystal are 0.06MVm-1 and 0.25MVm-1, respectively, and and for the PLZT are 0.15 MVm-1and 0.37 MVm-1, respectively.
For the simulation study, a energy-minimization-based model is developed. Simulations of domain switching processes are tested against the experiment results.

並列關鍵字

Electromechanical loading ； in-situ observation ； BaTiO3 single crystal ； PLZT polycrystal ； Domain switching ； Simulation

參考文獻

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