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.     

Influence of Water Vapor Pressure on Superconducting Properties of YBCO Film by TFA-MOD

We fabricated YBa₂Cu₃O_7−x (YBCO) films on LaAlO₃ (LAO) substrates using metal organic deposition of precursor solutions containing metal trifluoroacetates (TFA-MOD). The effect of water vapor pressure on the microstructure, degree of texture, and critical current of prepared YBCO films was evaluated. The firing process was performed in the water vapor pressure range from 7 to 31 kPa. According to the results of the XRD, SEM and X-ray ω scan analyses, the causes of critical properties’ change with the different water pressure were explained. The YBCO film prepared at the lower water pressure showed the low critical current because of the a–b axis grain. The films fired at 20 kPa showed the highest critical current of 3.8 MA/cm².     

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.     

Fabrication of YBCO Film Using a New Copper Precursor by Chemical Solution Method

YBCO films were fabricated by using a modified precursor solution, which was prepared by mixing yttrium trifluoroacetate, barium trifluoroacetate, and a fluorine-free copper precursor. Crack-free films have been obtained in a rapid pyrolysis process. The texture, microstructure and superconducting properties of films were characterized by x-ray diffraction, scanning electron microscopy, and the inductive method, respectively. The effect of the heating rate on the phase formation, texture and critical properties (J _c) of YBCO films was investigated. The texture and critical current density varied significantly with the heating rate. Moreover, the J _c of 1.7?MA/cm² was obtained for YBCO films prepared at the heating rate of 3?K/min.     

不同热处理制度对NbTiTa超导线材性能的影响

通过调整超导线材的最终附加应变、时效热处理时间和时效热处理温度3个参数来提高NbTiTa超导线材的J_c性能.在法国国家高场实验室通过标准四引线法,在4.2K、0～11T的磁场中测量了线材的临界电流.结果表明,适度升高时效热处理温度、延长时效热处理时间、增加最终附加应变,有益于提高NbTiTa超导线材的临界电流密度.经4次时效热处理385~C×(40～70)h,最终附加应变从2.5增加到3.5,Φ1.25mm超导线材的J_c在4.2K、8T下达到777A/nm~2,与国外文献报道的J_c值相当.     

衬底温度对掺锆酸钡高温超导YBCO薄膜结构和超导电性能的影响

高温超导氧化物YBCO外延薄膜在掺入少量锆酸钡(BaZrO3,BZO)后,其超导性能会得到较大幅度的提高.研究了不同衬底温度对掺BZO的YBCO薄膜的外延特性及超导性能的影响.以固相反应法制备了YBCO及BZO原材料,利用固相烧结工艺制备了BZO含量为2%(质量分数)的YBCO-BZO复合靶材,采用脉冲激光沉积技术(PLD)在LaAlO3(100)基片上外延生长YBCO薄膜.以不同的衬底温度制备了YBCO薄膜,用X射线衍射和高分辨透射电子显微技术对所制备的YBCO薄膜的外延特性进行了分析.最后比较了在不同衬底温度下制备的YBCO薄膜的超导性能,得到了最佳衬底温度.     

无氟MOD法制备YBCO超导薄膜工艺中物相的演变过程

第二代高温超导带材在电力系统和磁体领域拥有良好的应用前景, 无氟金属有机盐沉积技术(FF-MOD)以其设备成本低、晶体生长速率快、环境友好等特点, 成为研究热点。本研究通过FF-MOD技术, 在铝酸镧单晶和CeO₂/IBAD-MgO/Y₂O₃/Al₂O₃/Hastelloy C276人工基板上制备得到钇钡铜氧(YBCO)薄膜, 并对不同制备温度下的样品进行淬火, 随后对淬火样品进行了X射线衍射、扫描电子显微镜和衰减全反射红外光谱的表征, 系统地研究了高温成相过程中BaCO₃和YBCO的相演变过程。实验结果表明, 在YBCO成相过程中, BaCO₃不会与Y、Cu元素的氧化物反应直接生成YBCO晶体, 并生成的YBCO相晶体先呈随机取向, 然后在热处理的过程中(800℃左右)逐渐转化为具有双轴织构的YBCO晶体。     

Preparation of Thick BaZrO3 Epitaxial Film for Coated Conductors by Polymer-Assisted Chemical Solution Deposition Method

BaZrO₃ (BZO) epitaxial films have been deposited on single-crystal substrate by polymer-assisted chemical solution deposition method and have been studied with X-ray diffraction (XRD), SEM, and AFM analyses. It is found that the surface morphology and degree of c-axis texturing of the epi-films vary with processing temperature and atmosphere, with the optimized processing temperature of 900 °C in argon. The films are found with good phase purity, high-degree in-plane and out-of-plane texturing, good density with pin hole- and microcrack-free nature, and a sufficient thickness of >250 nm. Highly epitaxial 700-nm-thick YBa₂Cu₃ O _7?x (YBCO) thin film exhibits the self-field critical current density (Jc) that reached 1.2 MA/cm² at 77 K. These results show that the BZO epi-films made with the current technique possess potentials as a single buffer layer for YBCO-coated conductors.     

沉积温度对化学气相沉积法制备铜薄膜性质的影响

以双(2,2,6,6-四甲基-3,5-庚二酮)化铜(Cu(DPM)₂)为前驱体,使用智能化学气相沉积设备在673 K至1173 K下于AlN多晶基板上制备Cu薄膜。研究了不同沉积温度对Cu薄膜的相组成、择优取向、宏观表面、微观结构、元素组成及电导的影响。在873 K至1173 K时制备了具有(111)择优取向的紫铜色铜薄膜,同时存在(200)和(220)取向,且铜晶粒呈岛状生长模式。随着沉积温度的升高,薄膜的导电性先增强后减弱。在1073 K时,制得了导电性最好且高度(111)择优取向的最纯紫铜色Cu薄膜,即1073 K为制备Cu薄膜的最佳沉积温度。     

碳含量对碳氮化硅薄膜化学结构和力学性能的影响

利用微波电子回旋共振（MW-ECR）等离子体增强非平衡磁控溅射法制备了碳氮化硅（SiCN）薄膜。研究结果表明，碳含量对薄膜化学结构、力学性能有很大影响。傅里叶变换红外光谱（FT-IR）和X射线光电子能谱（XPS）表征显示，随着碳靶溅射偏压由-450V提高到-650V，薄膜中碳含量由19．0％增加到27．1％，sp^3C-N键含量增多，薄膜生长速率由3．83nm／min提高到5．83nm／min，硬度在-600V时达到最大值25．36GPa。上述结果表明，提高碳靶溅射偏压，可以提高薄膜含碳量，得到性能较好的SiCN薄膜。     

溶胶—凝胶法制备YBCO超导薄膜微细图形

以甲醇为溶剂,以醋酸铜、醋酸钇和醋酸钡为起始原料,二乙烯三胺、三氟乙酸、丙烯酸为添加剂,采用溶胶-凝胶法制备了具有紫外感光性的YBCO溶胶及其凝胶薄膜,其紫外吸收峰在250nm附近,对应于铜络合物的电子跃迁吸收,随着紫外光的照射,其峰值逐渐降低,凝胶在有机溶剂中的溶解性也发生变化,显示了凝胶薄膜的紫外感光性.基于这一特性,本文提出了一种YBCO 超导薄膜图形制备新方法,即利用凝胶薄膜自身的紫外感光性,使紫外光通过掩模照射薄膜,然后在甲醇中溶洗,进一步热处理,得到了YBCO超导薄膜图形.结果表明,图形化的YBCO薄膜具有较强的c轴取向,超导转变温度T_C达到92K.     

乙烯对CVD法制备硅薄膜性能的影响

以硅烷和乙烯的混合气体的原料气,通过常压化学气相沉积方法在玻璃衬底上生长出了硅薄膜。结合光电子能谱、高分辨电镜以及薄膜抗腐蚀性研究,证实乙烯的引入使硅薄膜中形成一定数量的ＳｉＣ微晶粒。ＳｉＣ较高的化学稳定性使薄膜具有较强的耐碱性,而其较小的折射率使薄膜的镜面反射率较高低。含有ＳｉＣ的硅薄膜经碱液适当腐蚀后能降低镜面反射,进而有可能减少光污染现象。     

Ag基底织构和表面状况对YBCO薄膜性能的影响

采用MOD方法在三种不同织构和表面状态的Ag基底上制备了YBCO薄膜,研究了Ag基底的织构和表面状态对YBCO超导薄膜的影响.在真空中退火的Ag基底上沉积的YBCO薄膜仅有c轴取向,且薄膜表面有很多平行条纹,薄膜的连接性不好,J_c不高;在氩气气氛中退火的Ag基底上沉积的YBCO薄膜,具有很强的c轴取向和良好的面内织构,J_c相对较高为1.2×10⁴A/cm²;冷轧Ag基底沉积的YBCO薄膜织构没有氩气退火的Ag基底上的强,但薄膜的表面平整,连接性好,临界电流密度最高为1.5×10⁴A/cm².     

Effect of Heat Treatment on the Structure and Properties of Superconducting Nb and Nb3Sn Electrodeposits

The effect of vacuum heat treatment (900–1600°C) on the structure and properties of superconducting Nb and Nb₃Sn coatings produced via electrolysis of molten salts is studied. The results demonstrate that the primary recrystallization of the coatings is characterized by a nonuniform nucleation of new grains: nuclei appear first in a defect-rich layer near the coating–substrate interface. The presence of the substrate during heat treatment prevents complete relaxation of the lattice strain and dislocations in the coatings, without significantly influencing the macroscopic stress. The relaxation of lattice strain and the reduction in dislocation density during recrystallization bring the coatings closer to equilibrium, thereby changing their superconducting properties.     

热处理对溶胶-凝胶法制备ZnO薄膜性能的影响

以(CH3COO)2Zn·2H2O为前驱物,利用溶胶-凝胶旋转涂膜法以普通玻璃为基底制备ZnO薄膜。分别采用X射线衍射仪、紫外-可见分光光度计和扫描电子显微镜等对ZnO薄膜的物相组分、透射率和表面形貌进行测量与表征。研究了热处理温度对ZnO薄膜的物相结构和光学特性的影响。实验结果表明,ZnO薄膜的物相结构和可见光透射率都与热处理温度有关,随着热处理温度升高,ZnO薄膜的晶粒尺寸增大,晶格常数逐渐减小,薄膜的透射率增大。     

CVD金刚石薄膜的介电性能研究

对直流电弧等离子体ＣＶＤ制备的金刚石薄膜的介电性能进行了研究，结果表明，金刚石薄膜的介电性能主要取决于样品的多昌性质以及表面和晶界处的非金刚石相和杂质成分。     

YBCO Superconducting Film Coated on LaAlO3 Substrate by TFA-MOD Process

Epitaxial YBCO film was coated on (001) LaAlO₃ single-crystal substrate by metalorganic deposition of metal trifluoroacetate precursors. From XRD and EDS analysis, it was observed that the film contains CuO or Cu₂BaO₂ segregation, but transport measurement found the segregation structure does not severely prevent the percolation of supercurrent-carrying material. The YBCO films performance is up to 2.4 MA/cm² with I_c of 137 A/cm-width at 77 K and 0 T, and superconducting transition temperature T_c reaches around 91.3 K with sharp transition temperature T_c of 0.36 K.     

可见光诱导TiO2光催化及其机理研究进展

简述了二氧化钛的光催化机理。针对其禁带宽度较大,只能被小于387nm的紫外光所激发的缺点,综述了近年来国内外针对纳米TiO2可见光催化的改性方法和改性机理研究进展,包括离子掺杂、半导体复合、表面光敏化等方法。最后展望了提高纳米TiO2可见光光催化活性研究的前景。