Rapid preparation of the nitrate P YBCO superconductive film by AD solution deposition

用硝酸盐高分子辅助沉积法（简称PAD）来制备YB2C3O7-x（YBCO）超导薄膜,有着制备速度快、工艺简单和无环境污染等优点。采用硝酸盐水相前驱液,并加入高分子螯合剂和薄膜改性剂,然后将前驱液涂覆在LaAlO3（LAO）单基晶片上,采用快速低温分解,再经过高温烧结制备出完整的YBCO超导薄膜。在1.0×10-4 O2/N2气氛下制备的YBCO超导薄膜致密,YBCO（00l）峰取向明显,没有其它杂相峰,同时,转变起始温度TC=91K,转变宽度ΔTC=2K;在77K、自场下临界电流密度JC为约1MA/cm2。实验结果表明,采用硝酸盐PAD法的低温分解时间比传统的TFA-MOD法缩短9h左右,而且制备出的YBCO超导薄膜性能优良,该方法为以后的长带生产提供了一种新的制备技术。     

低温热处理对TFA-MOD技术制备YBCO超导薄膜的影响

采用三氟乙酸盐-金属有机沉积(TFA-MOD)技术在LaAlO3(001)单晶衬底上沉积YBa2Cu3O7-χ(YB-CO)导薄膜,研究了低温热处理条件(涂覆环境相对湿度和升温速度)对前驱膜形貌和YBCO超导膜的影响.从金相显微镜(OM)和扫描电镜(SEM)观察可以看出,高涂覆环境相对湿度是引起前驱膜出现宏观裂纹的主要原因,前驱膜分解速度过快会造成薄膜中出现褶皱和微观裂纹,前驱膜出现不完整性形貌将会影响YBCO薄膜的成相、形貌和性能.通过优化低温热处理务件,获得了表面形貌完整的前驱膜,避免了在高温成相阶段中出现杂相,提高了涂层导体的超导性能,77K时J.可超过2.0MA/cm2.     

前驱液中添加聚乙烯吡咯烷酮对YBa2Cu3O7-δ膜形貌和性能的影响

用三氟乙酸金属有机物沉积(TFA-MOD)方法在LaAlO3(100)基底上生长YBa2Cu3O7-δ(YBCO)超导薄膜,研究了向前驱液中添加聚乙烯吡咯烷酮(PVP)对YBCO薄膜微结构和超导性能的影响.涂膜在氧气环境中进行200～250℃热解,再经775℃氩气环境下结晶后获得YBCO超导薄膜.在相同热处理条件下,未添加PVP的前驱液制得的YBCO薄膜临界电流密度为4050A/cm2,添加PVP的前驱液制得的YBCO薄膜临界电流密度为5800A/cm2.后者表现出较少的孔洞,较强的c轴取向,较纯的双轴织构和较高的临界电流密度.因此,向前驱液中添加PVP的化学方法可以改进YBCO涂层导体的MOD制备过程.总压,氧分压和热处理温度等工艺条件将进一步优化,以提高临界电流密度.     

YBCO覆膜导体低成本制备研究

报道新近发展的离子束结构改性(ISM)技术以及同步织构(STEX)技术在YBCO覆膜导体制备中的最新进展。采用TFA-MOD工艺成功的在LaAlO_3(100)衬底上制备出了临界电流密度高达6.5 MA/cm~2 (77K,0T)的YBCO超导薄膜,其超导转变温度接近91K;同时还在LaAlO_3(100)衬底上成功地采用溶胶-凝胶工艺制备出了具有高度外延双轴织构取向的SrTiO_3缓冲层材料;在YSZ(100)衬底上采用溶胶-凝胶工艺制备出了具有高度双轴织构取向的CeO_2缓冲层材料。随后在这两种衬底上采用TFA-MOD工艺沉积的YBCO超导薄膜也获得了超过1MA/cm~2(77K,0T)的临界电流密度。作为制备实用化YBCO超导带材的新路线,在数厘米长的IBAD-YSZ/Hastelloy金属基带模板上,采用低成本化学溶液方法依次制备出了高质量的CeO_2缓冲层和YBCO超导薄膜,获得了高达1.2MA/cm~2(77K,0T)的临界电流密度。为长超导带材的制备打下了很好的基础。提出了在金属基带上制备YBCO覆膜导体的新方法一同步织构(STEX)法。用该方法可以有效解决RABiTS方法中的金属基带热处理变软...     

低氟MOD法制备Zr掺杂YBCO薄膜的研究

在金属有机盐沉积（MOD）法制备YBCO薄膜的工艺中, 采用无F的α甲基丙烯酸铜取代原来的三氟乙酸铜, 可以降低前驱溶液中大约50%的氟含量. 研究表明, 该方法大大缩短了YBCO前驱薄膜受热分解的时间, 仅为原来的1/7. 通过XRD、SEM分析发现, 该方法可以制备成分单一、具有良好立方织构的YBCO薄膜, 且薄膜表面平整致密, 没有裂纹, 临界温度(T_c)达到了90K左右, 77K、自场下的临街电流密度(J_c)达到了2.84MA/cm². 通过在制备的YBCO薄膜中引入6mol% 的 Zr元素掺杂, 有效地提高了YBCO薄膜在外加磁场下的超导性能.     

脉冲激光法制备涂层导体YBCO超导层的研究

报道了用脉冲激光沉积技术(PLD)在CeO2/YSZ/Y2O3/NiW衬底上连续制备YBCO超导层的研究结果。分析了衬底温度、薄膜厚度和退火时间分别对YBCO的织构、表面形貌及c轴晶格常数的影响。实验发现温度较低将导致a轴晶粒的生长,薄膜太厚将引起表面形貌变差,而YBCO薄膜c轴晶格常数随退火时间的增长而减小。最终得到了高质量的YBCO涂层导体,超导转变宽度(ΔTc)为1.6K,临界电流密度(Jc)达1.3MA/cm2(77K,SF)。     

Ba源配比对MOCVD法制备YBCO薄膜性能的影响研究

采用单一液相混合源进液及闪蒸的MOCVD系统在LaAlO₃(001)单晶基片上制备YBa₂Cu₃O_7-x(YBCO)薄膜, 研究混合源中Ba含量对YBCO超导薄膜成分、结构及电流承载能力的影响。结果表明, 当Ba含量较小时, YBCO薄膜中易于形成尺寸较小的CuO颗粒; 随着Ba含量的增加, 薄膜中形成Ba₂CuO₃晶粒, 并且Ba₂CuO₃晶粒尺寸随Ba含量的增加而逐渐增大。杂质相的含量、尺寸以及与YBCO的晶格匹配程度对YBCO薄膜的双轴取向生长和电流承载能力具有重要影响。当原料摩尔配比Ba/Y=3.9时, 成功制备出了具有优异面内面外取向、结构致密的YBCO超导薄膜, 77 K下的300 nm厚度薄膜的临界电流密度达到4.0 MA/cm², 该研究结果对于第二代涂层导体的发展具有重要意义。     

YBa2Cu3O7-δ薄膜的BaCl2/BaF2-MOD法制备及超导特性研究

传统三氟乙酸金属有机化学溶液沉积法(TFA-MOD)制备YBa₂Cu₃O_7-δ (YBCO)超导层,Ba倾向于与F结合,从而避免BaCO₃的形成。本工作开展了新型基于BaCl₂/BaF₂途径的化学溶液法生长YBCO超导薄膜的研究。重点研究了添加Cl对YBCO薄膜晶粒取向、微观结构和超导性能的影响,并通过生长反应的热化学计算,分析了BaCl₂途径YBCO薄膜的物相转变机制。结果表明:添加Cl有利于抑制a轴晶粒取向,促进c轴晶粒成核。添加Cl的YBCO双层膜起始转变温度(Tc-onset)没有明显变化,约为89.6 K,其临界电流密度(Jc)显著提升, Jc达到2.07 MA/cm²(77K,自场)。此外,生长反应过程的物相转变分析表明Cl优先与Ba结合形成BaCl₂,有效避免BaCO₃的形成。本研究结果表明:添加Cl对制备YBCO超导厚膜有促进作用,这为MOD法制备YBC...     

化学溶液沉积法制备Y2O3过渡层

为了满足YBa2Cu3O7(YBCO)超导带材生产实际的需要,在金属基带和YBCO超导薄膜之间制备一层合适的氧化物过渡层显得尤为重要。以乙酸钇为原料配制前驱体溶液,采用金属盐化学溶液沉积法在织构的Ni-5%W(质量分数)(Ni-5W)带上成功制备了Y_2O_3过渡层。结果显示,氮气氛下1050℃热处理1h后,所获得的Y_2O_3过渡层具有良好的晶体织构,晶体生长取向为(100),完全复制了Ni-5W带模板的结构,为YBCO生长提供了良好的模板。在Y_2O_3过渡层上制备的YBCO薄膜表现出良好的超导性能。     

高温超导带材用YBCO前驱体的热分解非等温动力学研究

基于金属有机物沉积法制备YBCO高温超导带材的研究现状,为了探索涂层导体超导层的快速制备工艺,开展了超导层前驱体的热分解动力学研究。在氩气条件下利用同步热分析仪获得丙酸为溶剂、乙酸盐为溶质的前驱体热分解过程的TG-DTG-DSC-MS曲线,采用普适积分法、微分法以及多重速率扫描Kissinger法相结合的方式确定YBCO超导相合成反应的机理和相关动力学参数。结果表明,从室温～900℃的升温过程中,前驱体的热分解反应可分为4个阶段。其中,第4阶段的YBCO超导相合成反应过程服从随机成核和随后生长的机理模型(n=2),热分解反应动力学补偿效应为lnA=0.120E-2.699。     

High Quality YBCO Film Growth on SrTiO_3-Buffered LaAlO_3 Substrate by Full Solution Method

A full solution method has been developed as a low cost process of YBa2Cu3OT-x （YBCO） coated conductor fabrication. In this study, highly biaxially textured SrTiO3 （STO） buffer layers were fabricated on LaAlO3 （LAO） single crystal substrates by sol-gel method using metal alkoxides as the staring precursor materials. High quality YBCO superconducting film was then fabricated on STO-buffered LAO substrate by trifluoroacetic metalorganic deposition （TFA-MOD） method. For the YBCO superconducting film, only （001） diffraction peaks can be detected by XRD （X-ray diffraction） analysis with no other phases detectable. Especially, Inplane texture of YBCO film is improved compared to that of STO buffer layer from phi scans analysis, which indicates the self-epitaxy phenomenon explained by considering interracial energy. STO and YBCO films both show c-axis oriented grains growth and have uniform surface microstructure. A critical transition temperature, TC （R=0） of 89.5 K and a critical current density of 2 mA/cm2 （77 K, self-field） were obtained for a 0.2μm thick YBCO film on STO-buffered LAO substrate. No reaction between YBCO and STO was detected by XRD analysis. This full solution process may provide a promising low cost fabrication route for YBCO coated conductors on metal tape.     

大面积YBCO高温超导双面薄膜的生长研究

采用倒筒式直流溅射(ICS)方法,辐射方式加热基片,通过电机带动基片旋转,在两面同时溅射沉积YBCO高温超导双面薄膜。在加热温度为850℃,总压强为35Pa,氧氩比为1∶2,靶基距50mm,基片转速5～40r／min条件下,在20mm×20mm的LaAlO     

超声雾化方法中两步沉积对YBCO薄膜性能的影响

用自行研制的超声雾化装置在{110}<011>织构的Ag基带上直接沉积了YBCO涂层超导薄膜, 结果发现一步沉积所得YBCO薄膜的表面有许多白色小颗粒, 而且薄膜的织构和临界电流密度都较低, 这是在900℃高温沉积过程中大量的Ag蒸发和扩散到YBCO膜层中所致. 于是本文提出分高低温两步沉积的实验方案, 即700℃先沉积15min, 再升温到900℃沉积30min, 通过SEM对薄膜表面和EDS能谱对薄膜的断面进行分析可知, 两步沉积的YBCO薄膜中Ag的含量大大降低, 而且薄膜的织构和临界电流密度得到明显改善和提高, 最后通过两步沉积制备了15cm长、临界电流密度高于10⁴A/cm²的YBCO超导薄膜.     

Dependence of Microstructure and <Emphasis Type="Italic">J</Emphasis><Subscript>c</Subscript> of YBCO Films on CeO<Subscript>2</Subscript> Cap Layers Deposited by Multi-plume PLD

In order to achieve high-performance YBa₂Cu₃O_7?x (YBCO)coated conductors (CCs) fabricated in industrial scale, it is necessary to enhance the transport properties and production speed of the CCs for use in various application forms. The transport performance of CCs depends upon the inner structure of the conductors, which make it important to analyze the microstructure and transport properties. The thickness of the buffer layer is a factor in improving speed. In this work, we deposited YBCO films on CeO₂ cap layers with different thicknesses ranging from 21 to 563 nm by multi-plume pulsed laser deposition (PLD) and investigated the dependence of the microstructure and superconducting properties of YBCO film on the thickness of CeO₂ films. The crystalline structure and surface morphology of YBCO films are systematically characterized by means of XRD, AFM, SEM and TEM. The critical current of YBCO film was measured by the conventional four-probe method at 77 K, in self-field. The results showed that the microstructure and superconducting performance of YBCO film were strongly dependent on the thickness of CeO₂ films. At the optimal CeO₂ layer thickness of 221 nm, the YBCO film exhibited a sharp in-plane and out-of-plane texture of full width at half maximum (FWHM) values of 1.5° and 2.4°, respectively, and smooth morphology of root mean square (RMS) value as low as 4.0 nm. The sharply biaxially textured YBCO films with the critical current density as high as 4.7 × 10⁶ A/cm² (77 K, in self-field) were obtained on CeO₂/MgO/Y₂O₃/Al₂O₃/C276 architecture.     

溶胶-凝胶法制备YBa2Cu3O7-x超导薄膜的研究

传统的TFA-MOD法制备YBa2Cu3O7-x薄膜,采用Y、Ba、Cu 3种金属的三氟醋酸盐(TFA)为先驱体,在热分解时,会产生大量的HF气体,即使通过将近20h的缓慢升温过程来对薄膜进行热分解,也难以获得较为光洁的表面,从而无法实现厚膜的制备.本文提出了一种新的含氟溶胶-凝胶工艺,通过减少溶胶中F的含量,并利用二乙醇胺做修饰剂,缩短了热分解时间,提高了薄膜的表面光洁度.利用该方法在(010)LaAlO3衬底上制备了具有良好c轴取向,临界转变温度为89K的YBCO超导薄膜.     

Chemical solution approaches to YBa2Cu3O7_delta-Au nanocomposite superconducting thin films

We explore the feasibility of preparing YBa2CU3O7-Au (YBCO-Au) nanocomposite thin films by chemical solution deposition (CSD). Two approaches were used: (i) A standard in-situ methodology where Au metallorganic salts are added into the precursor solution of YBCO trifluoroacetate (TFA) salts and (ii) a novel approach where stable colloidal solutions of preformed gold nanoparticles (5-15 nm) were homogeneously mixed with TFA-YBCO solutions. A detailed analysis of the microstructure of the films showed that in both cases, there is a strong tendency of gold nanoparticles to migrate to the film surface. However the kinetics of this migration evidences important differences and in the case of preformed nanoparticles their size remains unchanged (a few nanometers) whereas for the in-situ nanocomposites gold ripening leads to large particles (hundreds of nanometers). The grown YBCO-Au films showed good superconducting characteristics (J(c) 2 MA/cm2 at 77 K) but the absence of Au inclusions inside the YBCO matrix explains the fact that no enhancement of vortex pinning was observed.     

Growth and Characterization of YBCO Thin Films by Sequential Deposition and Annealing

A novel thin film growth procedure, sequential deposition and annealing (SDA), which contains the advantages of both in situ and ex situ procedures, was proposed. Y₁Ba₂Cu₃O_{7 – x} (YBCO) high temperature superconducting thin films were grown and characterized by the SDA procedure. Purely c-axis-oriented YBCO thin films with no foreign phases and other oriented grains were successfully prepared. The superconducting transition properties of SDA-grown YBCO thin films were measured by measurement of inductance and resistance. The inductance measurements gave a T _c ^onset of 85 K and a T _c of 5 K. The resistance measurements gave a T _c ^onset of 90 K and a T _c of 5 K. Atomic force microscopy studies showed that SDA-grown YBCO thin films had micrometer-size grains surrounded by many nanometer-size grains. The nanometer-size grains in SDA-grown YBCO thin films are responsible for degradation of superconducting transition properties.     

Influence of Partial Melting Temperature on Structure and Superconducting Properties of YBCO Film by Non-fluorine MOD

High performance YBCO epitaxial films were prepared on LaAlO₃ (00l) single crystal substrate by the non-fluorine polymer-assisted metal organic deposition (PA-MOD) method. Influence of partial melting temperature on the epitaxial structure and superconducting properties of YBCO films was investigated. Biaxial texture, surface morphology, and superconducting properties of the films have been significantly improved under the optimized preparation conditions. A high J _c up to 3.5 MA/cm² at 77 K, self-field has been achieved with a significantly improved J _c(H).     

Effect of post-annealing on thin YBCO films deposited from a nanocrystalline target

Pulsed laser deposition is used to ablate thin superconducting YBCO films on SrTiO ₃ substrates. The most important parameters of thin superconducting films are high critical current density, ability to stand magnetic fields and smoothness of surfaces. Smoothness is important in fabrication of layered structures and for research of basic properties of thin superconducting structures. The target sintered from YBCO nanopowder is a promising material for making films which meet most of the requirements above. Investigations by AFM show that our target has grains about one order of magnitude smaller than usual grain size of commercial targets. At optimal deposition parameters, the oxygen pressure of 0.4 torr in the chamber and the substrate temperature 725°C, films with T _c = 90 K, J _c =8 × 10⁶ A/cm ² (77 K) and RMS surface roughness = 1.5 nm are obtained. Thermal annealing of the deposited films for 18 h at 900°C further increases the value of J _c .     

High-Quality YBa2Cu3O7−x Films with CeO2/YSZ Buffer Layers on 2-Inch Si Wafers Deposited by Pulsed Laser

The pulsed laser deposition (PLD) process is shown for in situ reproducibly fabricating YBa₂Cu₃O_7?x (YBCO) superconducting films with yttrium-stabilized zirconia (YSZ) and CeO₂ buffer layers, nonsuperconducting crystalline YBa₂Cu₃O_7?x (YBCO*) passivation layer, and silver contact film on 2-inch silicon wafers. Variations of less than ±7% in film thickness have been obtained for this multilayer growth over the whole wafer. The YBCO films on 2-inch silicon wafers have homogeneous superconducting properties with zero resistance temperature T _c0 from 88.4 K to 88.9 K. and critical current density J _c at 77 K and zero field from 2.5 × 10⁶ to 7× 10⁶ A/cm². The YSZ, CeO₂ and YBCO layers grow epitaxially on silicon wafers. Full widths at half maximum (FWHMs) of (113) reflections of 40 nm thick YBCO layer from φ-scan patterns are only 1.71° and 1.85° corresponding to the center and edge of the wafer, respectively. These results are very promising for developing high-quality high-T _c superconducting devices on large-area silicon wafers.