本文選題：超導(dǎo)體 + YBCO　； 參考：《吉林大學(xué)》2015年碩士論文

【摘要】：高溫超導(dǎo)體YBCO具有高載流強度和低交流損耗等優(yōu)點,能在液氮環(huán)境下工作,在微波、能源及電力等領(lǐng)域有著廣闊的應(yīng)用前景和商業(yè)價值。研究發(fā)現(xiàn),YBCO超導(dǎo)膜的臨界電流密度會隨著膜厚度的增加而降低。如何解決這一問題進一步提高YBCO超導(dǎo)膜的臨界電流密度,成為了當(dāng)前的研究熱點。根據(jù)磁通釘扎理論,人為的在YBCO超導(dǎo)膜內(nèi)引入缺陷作為釘扎中心來提高其臨界電流密度是可行的。它主要是通過摻雜或者引入晶格失配來影響超導(dǎo)膜內(nèi)的缺陷狀態(tài),提高缺陷濃度。讓這些缺陷作為有效的釘扎中心,可以阻止磁通因渦旋運動而產(chǎn)生能量耗散,從而提高超導(dǎo)膜的電流承載能力。 本文采用光輔助MOCVD技術(shù),就這個問題對YBCO超導(dǎo)疊層膜展開了研究,具體研究內(nèi)容如下： (1)對Ba源對YBCO外延膜結(jié)晶質(zhì)量和表面形貌進行了研究,實驗發(fā)現(xiàn),在制備YBCO外延膜時,Ba源揮發(fā)率對膜結(jié)晶質(zhì)量和微觀形貌有較大影響,“貧鋇”的YBCO薄膜表面堆積大量CuO雜質(zhì)顆粒,膜內(nèi)出現(xiàn)尺寸很大的裂縫；隨著Ba源溫度提高,源揮發(fā)率提高,膜內(nèi)Ba含量得到補充,表面雜質(zhì)顆粒逐漸減少.選用適當(dāng)?shù)腂a源加熱溫度,保持Ba源稍微過量能夠獲得結(jié)晶質(zhì)量較好的膜。 (2)選用了Y2O3納米薄層結(jié)構(gòu)作為生長YBCO疊層膜的過渡層,對在YBCO超導(dǎo)膜上生長的Y2O3納米過渡層的微觀形貌進行了研究,隨著生長時間增加Y2O3納米點由于點與點之間的合并尺寸變大密度降低。 (3)在LAO襯底上成功制備出YBCO/Y2O3/YBCO疊層薄膜,Y2O3納米點的大小對YBCO結(jié)晶質(zhì)量、表面形貌以及臨界電流密度影響很大。隨著Y2O3納米點生長時間的增加,其尺寸增大而密度降低。在上層YBCO薄膜生長過程中,由于大尺寸Y2O3納米點的存在,其晶格排列周期性被破壞,使得膜內(nèi)出現(xiàn)孔洞,薄膜結(jié)晶質(zhì)量變差。制備得到的樣品多空洞,不連續(xù)。在Y2O3納米過渡層生長時間為20s的條件下,獲得了臨界電流密度最好的樣品,其Jc=2.4MA/cm2(77K,OT),與未生長Y203納米點的YBCO薄膜相比,其臨界電流密度提高20%。
[Abstract]:High temperature superconductor (YBCO) has the advantages of high current carrying strength and low AC loss. It can work in liquid nitrogen environment and has broad application prospect and commercial value in microwave, energy and power fields. It is found that the critical current density of YBCO superconducting films decreases with the increase of film thickness. How to solve this problem and improve the critical current density of YBCO superconducting films has become a hot research topic. According to the flux pinning theory, it is feasible to increase the critical current density by artificially introducing defects into YBCO superconducting films as pinning centers. The defect state in the superconducting film is affected by doping or introducing lattice mismatch, and the defect concentration is increased. By using these defects as effective pinning centers, the energy dissipation of the magnetic flux due to vortex motion can be prevented and the current carrying capacity of the superconducting film can be improved. In this paper, the photo-assisted MOCVD technique is used to study the YBCO superconducting laminated films. The main contents of the study are as follows: The crystal quality and surface morphology of YBCO epitaxial films by Ba source were studied. It was found that the volatilization rate of Ba source had a great influence on the crystalline quality and micromorphology of YBCO epitaxial films. A large number of CuO impurity particles were deposited on the surface of "barium poor" YBCO film, and large cracks appeared in the film, and with the increase of Ba source temperature, the volatile rate of the source increased, the Ba content in the film was replenished, and the surface impurity particles gradually decreased. The films with good crystallization quality can be obtained by using proper heating temperature of Ba source and keeping Ba source slightly excessive. (2) Y2O3 nano-thin layer structure was selected as the transition layer for the growth of YBCO laminated film. The microstructure of the Y2O3 nano-transition layer grown on the YBCO superconducting film was studied. With the increase of growth time, the density of Y2O3 nanowires decreases due to the increase of the combined size between the dots. (3) the size of Y _ 2O _ 3 nanowires of YBCO/Y2O3/YBCO laminated films on LAO substrates has a great influence on the quality, surface morphology and critical current density of YBCO. With the increase of the growth time of Y2O3 nanowires, the size increases and the density decreases. During the growth of YBCO thin films in the upper layer, due to the existence of large size Y2O3 nanowires, the lattice arrangement is destroyed periodically, which leads to the formation of pores in the films and the deterioration of the crystalline quality of the films. The prepared samples are void and discontinuous. When the growth time of Y2O3 nanocrystalline transition layer was 20 s, the sample with the best critical current density was obtained. The critical current density of the sample was increased by 20 times compared with that of the YBCO film without Y203 nanoparticles.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM26

【參考文獻】

相關(guān)期刊論文 前6條

1 丁靈效;陳文祥;熊杰;陶伯萬;;快速前處理TFA-MOD制備YBCO超導(dǎo)薄膜的研究[J];低溫與超導(dǎo);2009年04期

2 郭志超;索紅莉;劉志勇;劉敏;馬麟;;超導(dǎo)臨界電流測量方法與原理[J];功能材料;2010年12期

3 張黃莉;田秀勞;徐蘭珍;;化學(xué)溶液沉積(CSD)法制備YBCO/Y_2O_3/YBCO薄膜[J];稀有金屬材料與工程;2012年S2期

4 趙忠賢,陳立泉,楊乾聲,黃玉珍,陳賡華,唐汝明,劉貴榮,崔長庚,陳烈,王連忠,郭樹權(quán),李山林,畢建清;Ba-Y-Cu氧化物液氮溫區(qū)的超導(dǎo)電性[J];科學(xué)通報;1987年06期

5 丁發(fā)柱;古宏偉;張騰;王洪艷;屈飛;彭星煜;周微微;;摻雜Y_2O_3和BaCeO_3提高MOD-YBCO超導(dǎo)性能的研究[J];物理學(xué)報;2013年13期

6 陳晉;;TFA-MOD法制備多層YBCO超導(dǎo)薄膜的特性研究[J];稀有金屬與硬質(zhì)合金;2014年01期

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