PVP辅助低氟溶液法制备YBa_2Cu_3O_(7-x)厚膜研究(英文)

传统的化学溶液法制备微米级YBa2Cu3O7-x(YBCO)涂层导体过程中,需要反复多次镀膜和热分解过程才能使膜厚达到1μm以上。本研究以独特的先进低氟溶液为YBCO前驱溶液,通过添加聚吡咯烷酮(PVP)作为增稠剂,提高了YBCO胶体的粘度,并提高了最终YBCO薄膜的厚度及致密性。单次镀膜获得的YBCO薄膜厚度达到了600nm。77K,0T条件下,临界电流密度Jc达到1MA/cm2以上。这种高分子改性的低氟YBCO前驱溶液沉积技术有望在未来涂层导体开发中发挥作用.     

前驱液成分对TFA-MOD法制备YBa2Cu3O7-x薄膜超导性能的影响

采用三氟乙酸盐-金属有机沉积法(TFA-MOD)在铝酸镧单晶基体上制备了YBa₂Cu₃O_7-x (YBCO)超导薄膜.通过改变前驱液的成分,研究了金属元素的不同化学计量比对YBCO薄膜的结构和性能的影响.结果表明,按照钇盐Y(CH₃COO)₃与钡盐Ba(CH₃COO)₂的比例为Y ∶Ba=1 ∶1.5时所制备的YBCO薄膜的临界电流密度比严 关键词： 三氟乙酸盐-金属有机沉积 钇钡铜氧薄膜 前驱液成分 磁通钉扎     

YBCO超导层的a轴晶生长研究

采用化学溶液沉积制备YBCO薄膜,研究了氧分压对YBCO超导层a轴晶生长的影响.研究发现氧分压是YBCO薄膜a轴晶形成的关键因素.当氧分压改变,YBCO生长模式由c轴生长转变为过渡到a(b)-c混合生长模式.低氧分压可以促进YBCO的c轴生长.高氧分压影响YBCO超导层的微观结构,促使YBCO的织构取向变差,最终导致YBCO超导层的性能降低.     

YGdBCO/YBCO+BaHfO3 复合超导层的制备

采用脉冲激光沉积和化学溶液沉积相结合制备超导薄膜. 在物理法制备的 YGdBCO 薄膜上实现化学法YBCO+BHO 的同质外延生长. 利用 X 射线衍射和扫描电镜对复合薄膜的相组成、 织构和形貌进行了表征. 结果表明, 采用化学溶液沉积可以在 YGdBCO 层上制备出高性能的 YBCO+BHO 薄膜. 复合薄膜具有良好表面形貌和锐利织构, 而且复合薄膜在77 K、1 T 的磁场下J c 为0.3 MA/cm2 , 最大钉扎力达到3 GN/m3 .     

改进型前驱液对化学溶液法制备YBCO薄膜的影响

传统全三氟乙酸前驱液对涂敷环境湿度、低温预分解过程中的升温速率和水汽分压等因素具有敏感性,采用改进型前驱液可以降低其敏感性,从而有利于涂层导体的连续制备.我们提出的改进型前驱液中,三氟乙酸钇、三氟乙酸钡和苯甲酸铜是前驱体,甲醇和丙酸的为溶剂.采用化学溶液法在铝酸镧单晶衬底上制备YBCO,低温分解阶段以1～5℃/min快速升温,可以获得低温后的前驱膜光滑完整,无裂纹.通过X衍射分析和扫描电镜分析了薄膜的织构和表面微结构,四引线法测试薄膜超导电性.采用改进型前驱液制备的薄膜超导转变温度(Tc)为90K,在77K、自场下临界电流密度(Jc)为1MA/cm2.     

化学溶液法La_2Zr_2O_7缓冲层的厚度对外延生长超导层的影响（英文）

采用全化学溶液沉积方法在NiW衬底上制备La_2Zr_2O_7缓冲层和YBCO薄膜.采用X射线衍射和扫描电镜研究了不同的LZO缓冲层厚度对超导层的影响.不同厚度LZO的面内外织构具有一定差别.当LZO厚度达到145nm时,LZO缓冲层的织构和阻隔能力最佳,才能制备出具有良好性能YBCO超导层.     

YBCO-TFA前驱溶液的透射红外光谱和粘度特性研究

三氟乙酸-金属有机沉积方法(TFA-MOD)是制备高质量大面积YBCO高温超导薄膜的有效制备方法之一,而溶液配制过程中的化学反应和提纯工艺是制备前驱液的关键技术。采用透射红外光谱分析手段对前驱溶液制备过程中的化学反应进行了系统研究,给出了每一步化学反应后溶液的红外光谱解析图谱,判定前驱液制备过程中发生的反应。同时,利用旋转粘度计对溶液的粘度进行持续测量,用来研究环境温度、放置时间对于溶液特性的影响。研究结果表明,在室温温度范围(20±2℃)制备前驱溶液的过程中特征有机官能团没有出现副反应,但是随着放置时间延长和温度升高,溶液的粘度降低。此外,对比提纯前后溶液的红外光谱,分析得出蒸馏过程只是简单的去除多余的水和乙酸等小分子物的过程。     

湿度对YBCO薄膜微观结构和超导性能的影响

文中采用无氟高分子辅助金属有机物沉积法( PA - MOD)在不同湿度条件下在LaAlO3单晶基底上制备了一系列YBCO超导薄膜.X射线衍射、扫描电镜和物性测量的结果表明,在成相热处理过程中气氛湿度对YBCO薄膜的结构和超导性能的有明显影响.干燥气氛成相的YBCO薄膜织构较好,表面较平整、致密,超导性能也较高,其临界超...     

高温热处理气氛对低氟MOD法制备YBCO超导薄膜的影响研究

金属有机物沉积法(MOD)制备YBa2Cu3O7-x(YBCO)涂层导体是最具有商业前景的方法之一.本文使用环烷酸铜代替三氟乙酸铜,降低了前驱液中大约50%的氟含量.然后在带有缓冲层(Y2O3/YSZ/CeO2)的Ni-5at.%W基带上采用MOD法制备了YBCO薄膜并系统研究了高温热处理过程中气体流速和氧分压对YBC...     

钛酸锶衬底表面改性对YBCO高温超导薄膜性能的影响北大核心CSCD

YBa_2Cu_3O_(7-x)(YBCO)高温超导材料在高温高场中具有比较高的临界电流密度,因此具有较好的应用前景.通过研究YBCO高温超导薄膜,以提高它的载流能力和超导性能是市场应用的迫切需要.文中所研究的钛酸锶(SrTiO_3)衬底,作为一种钙钛矿结构,不仅具有良好的化学和热稳定性,而且与YBCO高温超导薄膜具有较小的晶格失配度.通过酸腐蚀法和无酸腐蚀处理钛酸锶SrTiO_3(100)(STO)衬底,运用原子力显微镜观察了两种衬底处理方法对钛酸锶衬底表面结构的影响.并在其上用三氟乙酸盐金属有机沉积法(TFA-MOD)制备出临界密度达到约2.50~3.00 MA/cm^2的YBCO高温超导薄膜.通过四引线法表征YBCO高温超导薄膜的Tc达到了均约93K.通过扫描电子显微镜(SEM)分析了衬底处理技术的不同对其表层生长的YBCO高温超导薄膜形貌的影响.通过X射线衍射仪(XRD)固定方位角法表征了不同的衬底处理技术对薄膜内的残余应力的影响.     

高气压反射式高能电子衍射仪监控脉冲激光外延氧化物薄膜

在超高真空分子束外延（MBE）生长技术中，反射式高能电子衍射仪（RHEED）能实时显示半导体和金属外延生长过程，给出薄膜表面结构和平整度的信息，成为MBE必备的原位表面分 析仪.为了研究氧化物薄膜如高温超导（YBa₂Cu₃O₇） 、铁电薄膜（Sr_1-xBa_x TiO₃）及它们的同质和异质外延结构的生长机理，获得高质量的符合各种应用 需要的氧化 物多层薄膜结构，在常规的制备氧化 关键词： 高温超导薄膜 RHEED     

Fabrication of YBCO／YSZ and YBCO／MgO thick films using electrophoretic deposition with top-seeded melt growth process

Superconducting thick films were grown on single crystals MgO and YSZ by electrophoretic deposition with Y_2BaCuO_5(Y211) addition. YBCO thick films were then accomplished by sintering the precursor films above the peritectic temperature. Single crystals of MgO (3×3×0.5 mm^3) were used as top-seed to control crystal structure of the thick films. As shown by scanning electron microscopy, the morphologies of YBCO/YSZ and YBCO/MgO thick films are spherulitic texture and platelet type. The critical temperature is ～89 K for the YBCO/YSZ thick film; the onset transition temperature is 86.4 K and the transition width is ～3 K for YBCO/MgO thick film. The critical current densities (as determined by Bean model) are, in A/cm^2, 3870 (77 K) for YBCO/YSZ thick films and 2399 (77 K) for YBCO/MgO thick films, which are comparable to the best J_c reported of the thick films prepared by the same method.     

Influence of MgO surface conditions on the in-plane crystal orientation and critical current density of epitaxial YBCO films

The effect of magnesium oxide (MgO) surface conditions on in-plane grain orientation and critical current density of epitaxial YBa₂Cu₃O₇ (YBCO) films was systematically investigated. The MgO substrates were either “as received” or stored for some time, cleaned using different methods and lithographically prepared for our step-edge junction devices. The YBCO films were grown via reactive thermal co-evaporation by Theva, GmbH. The surface characterisation of MgO substrates was studied using X-ray photoelectron spectroscopy (XPS). The in-plane grain orientation of the YBCO films was studied by means of X-ray diffraction (XRD) φ-scan and the critical current density was measured for the XRD scanned samples. The surface condition of the MgO substrates was found to have a strong influence on the in-plane grain orientation and the critical current density of the YBCO films. The MgO substrates with a degraded or contaminated surface gave rise to 45° grain misorientation in YBCO films and reduced the critical current density. A final process step using a low energy Ar ion beam etching (IBE) of the MgO substrates prior to the YBCO film deposition was found effective in removing the in-plane grain misorientation and promoting the growth of perfectly aligned c-axis YBCO films.     

Effect of different oxidizing gases on the in-situ growth of YBa2Cu3O7−δ films by pulsed laser deposition

The effectiveness of oxygen (O₂), nitrous oxide (N₂O), and nitrogen dioxide (NO₂) as oxidizing agents during in-situ growth of YBa₂Cu₃O_7−δ (YBCO) films on (100) SrTiO₃ substrates by pulsed laser deposition has been studied as a function of deposition temperature (700–800°C), and laser wavelength (193,248 and 355 nm), for a wide range of oxidizer gas pressure (0.1–200 mTorr). In general, the superconducting transition temperature of the films has been found to increase with increasing oxidant pressure, with zero-resistance temperature ≈90 K only obtained in films prepared in a relatively high pressure (150–200 mTorr) of oxidizer gas. At lower pressures, the transition temperature while being depressed is quite sensitive to the nature of the oxidant, the laser wavelength and the deposition temperature. Nevertheless, independent of the oxygen source or other growth parameters, an almost linear decrease in transition temperature with a corresponding increase in the c-axis lattice parameter has been observed for all the film. YBCO films have also been deposited in a low pressure background (≤ 1 mTorr) using a combination of atomic oxygen and pulsed molecular oxygen. The results are discussed in terms of the oxygen requirement for kinetic and thermodynamic stability of YBCO during growth of the film by pulsed laser deposition.     

插入二氧化铈薄膜提高MOD-YBa2Cu3O7-x厚膜超导性能的研究

YBa₂Cu₃O_7-x(YBCO)膜存在“厚度效应”: 随着厚度增加, YBCO薄膜的临界电流密度下降, 尤其是YBCO薄膜的厚度超过1 μm时, 它的临界电流密度急剧下降. 本文在YBCO薄膜之间引入极薄的二氧化铈(CeO₂)薄膜, 成功制备出结构为YBCO/YBCO/CeO₂/YBCO的超导厚膜. 所制备的厚度为2 μm的YBCO膜临界电流密度为1.36 MA/cm² (77 K, 自场), 其性能比相同厚度的纯YBCO膜有了较大幅度的提升. 研究表明CeO₂薄膜起到了传递织构、松弛应力的作用.     

A new method to preserve the c-axis growth of thick YBa2Cu3O7–δ films grown by pulsed laser deposition

YBa₂Cu₃O_7–δ (YBCO) films were prepared on (1 0 0) MgO substrates by pulsed laser deposition (PLD) method. In order to eliminate the a-axis growth, which is commonly observed in the YBCO film thicker than a critical value, we developed a new PLD target that was sintered at a temperature far below YBCO 123 phase formation. The surface analysis made by AFM technique confirmed that very fine particles of around 20 nm size could be ejected from the new target to the substrate. The fine oxide clusters could be easily moved and incorporated into the YBCO phase thus benefited the c-axis growth even in the thick films. For instance, only the c-axis growth in the new film with a thickness of about 650 nm was larger than a critical thickness of the a-axis growth. However, in the standard film of the same thickness, there is 24.5% of the a-axis growth accompanying the main c-axis growth. Therefore, the c-axis growth could be preserved in the very thick YBCO film by a non-superconducting target.     

Effects of tin-compounds addition on Jc and microstructure for YBCO films

Tin-compounds were doped into YBa₂Cu₃O_7−δ (YBCO) films as pinning centers to enhance J_c in magnetic fields. YBCO films were grown by a metal organic deposition process using tri-fluoroacetates starting solutions. Tin-acetylacetonate salts were then dissolved into the starting solution as pinning centers. J_c of the YBCO films with tin-acetylacetonates were enhanced in all magnetic field angles. Transmission electron microscopy (TEM) and TEM-EDS (Energy Dispersive X-ray Spectroscopy) observations revealed the existence of tin-compound particles with the size of about 30 nm in the YBCO film. These nano particles were distributed randomly in the film and were considered to act as 3-dimentional pinning centers.     

快速前处理TFA-MOD制备YBCO超导薄膜的研究

三氟乙酸盐金属有机物沉积(TFA-MOD)方法是制备YBa2Cu3O7(YBCO)超导薄膜最有应用前景的方法之一。采用快速前处理TFA-MOD的方法在LaAlO3单晶基片上生长YBCO薄膜并与常规的TFA-MOD方法进行对比研究。XRD分析表明用快速前处理TFA-MOD方法制备的YBCO薄膜的c轴取向一致性,没有常规的TFA-MOD制备的YBCO薄膜好。SEM的分析表明快速前处理TFA-MOD制备的YBCO超导薄膜表面有孔洞和YBCO(103)取向生长的晶粒,常规方法制备的YBCO薄膜表面比较光滑,孔洞较少。虽然较常规方法制备的薄膜的临界电流密度(JC)低,但超导电性能分析表明,快速前处理方法制备的YBCO薄膜JC达到1mA/cm2以上,且前处理时间大幅缩短,对于提高YBCO薄膜制备的效率非常有效。     

低噪声HT_c rf SQUID芯片可控制备的实验研究

针对低内禀噪声要求条件下HTcrf SQUID芯片制备成品率和优质率低等问题,通过对YBCO薄膜的PLD制备工艺参数及所制作的YBCO薄膜性能与微观形貌的观测分析,提出晶界结构的非均匀和不一致性可能是影响低噪声台阶边沿型晶界结制备质量的观点,进而以淀积温度为典型控制参数设计了一组实验,对实验获取的YBCO薄膜和SQUID芯片的性能测试表明:YBCO薄膜生长的三高条件(高淀积温度、高氧分压和高激光能量密度)易造成薄膜表面平整度恶化和晶界构型的不均匀,而选择合适的淀积温度可有效提高SQUID芯片的噪声性能。