【正文】 其工作頻率越來(lái)越高達(dá)到幾十兆赫茲時(shí)，在這種超高頻率下， 用實(shí)驗(yàn)的方法來(lái)了解其的響應(yīng)情況很難實(shí)現(xiàn)，這時(shí)可以通過(guò)回線面積 A與電場(chǎng)幅值 E0和頻率 f在高頻下的關(guān)系來(lái)外推至超高頻率 ，從而預(yù)測(cè)在該頻率下的響應(yīng)情況和工作狀態(tài) [5]。由于疇翻轉(zhuǎn)需要消耗能量，該能量即為外電場(chǎng)所做的功， 因此極化強(qiáng)度 P在交變電場(chǎng) E的作用下其變化表現(xiàn)出落后于電場(chǎng) E的變化，構(gòu)成 PE雙值函數(shù)，又稱(chēng)作電滯回線。 圖 Bi4Ti3O12晶體結(jié)構(gòu)圖 Bi4Ti3O12鐵電薄膜有很大的各向異性，其自發(fā)極化方向位自發(fā)極化矢量位于 a— c平面，靠近 a軸（與 a軸成約 ）。 90年代以前，并沒(méi)有器件真正用到鐵電材料的鐵電性，而主要是利用鐵電材料的 壓電性和熱釋電性等 。 Devonshire將其進(jìn)行完善，發(fā)展為朗道 ? 德文希爾理論。自發(fā)極化是由于晶胞內(nèi)原子位置變化導(dǎo)致正負(fù)電荷中心不重合而產(chǎn) 生的。 本科畢業(yè)論文 (設(shè)計(jì) ) 題 目： 取向生長(zhǎng) Bi4Ti3O12鐵電薄膜的回線動(dòng)力學(xué)標(biāo)度 學(xué) 院： 物理科學(xué)學(xué)院 專(zhuān) 業(yè)： 材料物理 姓 名： 指導(dǎo)教師： 2022年 6 月 12 日 摘 要 稀土摻雜層狀鈣鈦礦結(jié)構(gòu)的 Bi4Ti3O12鐵電薄膜具有居里溫度高，自發(fā)極化大，耐疲勞性好的特點(diǎn)，適用于制作鐵電儲(chǔ)存器 。宏觀表現(xiàn)為極化矢量與外電場(chǎng)之間存在 電滯回線關(guān)系 [1]，即具有 鐵電性 。 鈣鈦礦時(shí)期 ? 鐵電軟膜理論， 1925 年左右發(fā)現(xiàn)了鈦酸鹽陶瓷具有很高的介電常數(shù)。隨著 80 年代中期薄膜制備技術(shù)取得了突破性進(jìn)展，高質(zhì)量鐵電薄膜的應(yīng)用成為可能。 隨機(jī)取向的 Bi4Ti3O12 鐵電薄膜的應(yīng)用具有很大的局限性，因?yàn)榫О帕须s亂無(wú)章，分散了其各向異性。 標(biāo)度 疇結(jié)構(gòu)以及其極化翻轉(zhuǎn)是理解和預(yù)測(cè)鐵電材料結(jié)構(gòu)和性能間關(guān)系的基礎(chǔ)，測(cè)量觀察電滯回線可以得到疇翻轉(zhuǎn)的一些信息。 第三，可以了解疇翻轉(zhuǎn)過(guò)程中過(guò)程中動(dòng)力學(xué)行為，比如，通過(guò)動(dòng)第二章 動(dòng)力學(xué)標(biāo)度及其意義 8 力學(xué)標(biāo)度，面積隨頻率的變化關(guān)系可以得到極化翻轉(zhuǎn)的特征時(shí)間，從而推測(cè)材料極化翻轉(zhuǎn)充分進(jìn)行 所需時(shí)間，進(jìn)而應(yīng)用于指導(dǎo)電子器件的設(shè)計(jì)和應(yīng)用。 鐵電體的自發(fā)極化強(qiáng)度并不是整個(gè)晶體為同一個(gè)方向 ，而是不同極化方向區(qū)域的疊加，既不同電疇的極化強(qiáng)度矢量疊加。 ： 1）啟動(dòng)鐵電測(cè)試儀，運(yùn)行鐵電測(cè)試軟件。 3）得到不同頻率 f和電場(chǎng)幅值 E0下對(duì)應(yīng)的面積 A，就可以繪制某一電場(chǎng)幅值 E0下回線面積 A隨頻率 f 的變化圖和某一頻率下回線面積 A隨電場(chǎng)幅值 E0的變化圖。 C/cm2。 用 ， a=﹣ ， b=。 圖 (a)(b)為外電場(chǎng)幅值 E0=450(kv/cm)情況下的 隨機(jī)取向Bi4Ti3O12 鐵電薄膜電滯回線隨外電場(chǎng)頻率的變化關(guān)系。 C/cm2左右。 2) 指數(shù) a 反映了回線面積 A隨電場(chǎng)頻率 f 變化的快慢，指數(shù) a為正值時(shí)，回線面積 A隨電場(chǎng)頻率 f 的增大而增大；指 數(shù) a 為負(fù)值時(shí)，回線面積 A隨電場(chǎng)頻率 f 的增大而減小?？梢缘弥?，當(dāng)回線達(dá)到飽和時(shí)，隨機(jī)取向樣品（ 1）， a/b 軸低擇優(yōu)取向度樣品（ 2）和 a/b 軸高擇優(yōu)取向度樣品（ 3）三者回線面積相比較，隨機(jī)取向樣品的回線面積 A要小于 a/b軸低擇優(yōu)取向度樣品小于 a/b軸高擇優(yōu)取向度樣品，這說(shuō)明隨機(jī)取向Bi4Ti3O12鐵電薄膜翻轉(zhuǎn)過(guò)程中消耗的能量隨取向度的增大而增大。 90186。 不同取向電疇消耗的能量不同，發(fā)生極化翻轉(zhuǎn)所需的外電場(chǎng)值也不同，與外電場(chǎng)方向越接近平行越易翻轉(zhuǎn)。 ，飽和回線對(duì)應(yīng)的疇翻轉(zhuǎn)越充分。s annual National Day for Eye Care, the China Youth Development ServiceCenter and Zhejiang Medicine, a leading listed Chinese pharmaceutical pany, jointlyannounced the kickoff of the about one month, a questionnaire piled by top eye care medical experts in China willbe distributed through multiple online partners, including m, as well asthrough offline survey events held in universities, middle schools and primary schools acrossthe report will be released based on the survey statistics and analysis, and most importantly,guidelines for parents and youth on how to care for the eyes and prevent myopia — agrowing problem in China39。s Pink Revolution, an annual campaign that seeks to raise awareness and funds for breast cancer research, the hotel recently announced. A major sponsor of the campaign for three years in a row, Conrad Macao has pledged to donate a portion of its proceeds to the fund, includ ing those collected from selling its popular bear and rubber duck merchandise, in limited pink editions. Pink is the theme for floral arrangements and decorations in the hotel in October. In addition, on Fridays that month, members of the management and staff will add something pink to their uniforms, regular s and handwritten guest cards. Breast cancer is the most prevalent type of cancer among women in Hong Kong and is also of significant concern in Macao and around the world, regardless of age, general manager Bede Barry said in a statement. The hotel has enlisted the support of a number of international and local celebrities to help drive the cause, including South Korean actor Jung Suk Won. This year, a lucky guest who stays at the hotel during the campaign and also donates money for the cause will win a necklace specially designed by Arte Madrid, a Spanish jewelry brand. Women should strive to balance quality of work and life, and have children at a young age. As a doctor I see much suffering because of this imbalance. Xiao Ying, 36, works for a large law firm. Her job means lots of travel, a heavy caseload and a large number of meetings, so her schedule is hectic. She has been pregnant twice, but had abortions on both occasions because she felt her busy, highpressure career wasn39。s ovarian function has declined and a bilateral oviduct blockage has occurred, meaning that in vitro fertilization is her only option. So, after reducing her workload, Xiao underwent IVF treatment. Luckily, she got pregnant after just one treatment cycle, but later experienced vaginal bleeding, and rushed to the hospital. I told her to rest and carry on with the treatment (to prevent a miscarriage). As Zubin Zarthoshtimanesh, a yoga guru, demonstrated postures at a high school stadium in Dujiangyan city, Sichuan province, some 200 students sat on colorful mats watching him closely. It was part of the first IndiaChina international yoga festival in the provincial capital, Chengdu, in Southwest China, where more than 1,000 fans from home and abroad gathered for lessons from 20 leading practitioners of the ancient Indian regimen, from June 1721. Yoga is to India what 參考文獻(xiàn) 31 perhaps tai chi is to China. Many countries other than India and China, also held the first World Yoga Day on June 21, after the United Nations last year agreed to Indian Prime Minister Narendra Modi39。s behaviors to care for eyes, basedon the timely and factual statistics the survey series of followup events will also be held in six cities, including Jinan in Shandongprovince, and Changsha in Hunan province, to educate people on how to care for eyes afterthe survey started. More and more Chinese are jogging to get and stay fit. Most joggers will run alone, but some will jog with friends or even coaches. The Beijing Olympic Forest Park is one of the most popular spots. It is packed with runners in the afternoon, usually after work, and at weekends. Jogging after a whole day39。盧老師誨人不倦的高尚情操、勤奮嚴(yán)謹(jǐn)?shù)闹螌W(xué)風(fēng)范和淵博的學(xué)識(shí)將使我終身受益。 a/b 軸擇優(yōu)取向 Bi4Ti3O12薄膜中電疇方向分布不平均， |cosθ |接近 1（易翻轉(zhuǎn)）的電疇多，其他方向分布的電疇（翻轉(zhuǎn)隨 |cosθ |的變小而變得困難）相對(duì)較少，因此其 A隨 E0變化表現(xiàn)出隨電場(chǎng)變大迅速增大，易翻轉(zhuǎn)電疇翻轉(zhuǎn)完成后，難翻轉(zhuǎn)電疇開(kāi)始翻轉(zhuǎn)，但與隨機(jī)取向薄膜相比數(shù)量要少，因此 A隨 E0的增加會(huì)更平緩。 疇一般發(fā)生在較高的外加電場(chǎng)作用下。翻轉(zhuǎn)過(guò)程中消耗的總能量等于對(duì)應(yīng)不同θ