W.T. Wang

Influence of chemical doping on flux pinning of GdBa2Cu3O7−z films

ABSTRACT Epitaxial GdBCO films with Cobalt (Co) and BaZrO3 (BZO) doping were prepared on (00l) LaAlO3 substrate by a self-developed fluorine-free polymer-assisted metal-organic deposition (FF-PA-MOD) approach. The effect of different doping ways on structure and properties of GdBCO films was investigated. Our results show that in-field critical current density (Jc) values of doped films have been distinctly improved compared to the pure film. It is noted that Co-doped film has much larger in-field Jc values than BZO-doped film, especially at higher temperatures. Furthermore, Co-doped GdBCO film shows significantly enhanced surface smoothness and grain connectivity. It is suggested that obviously enhanced Jc–B properties of the film may be attributed to improved surface morphologies and effective flux pinning centres by dilute Co doping. This study may offer another simple and efficient way to obtain the GdBCO-based coated conductors with high current densities.

Preparation of Coated Conductors With Fluorine-Free CSD Method

Preparation of new architectures of coated conductors (CCs) with fluorine-free chemical solution deposition (CSD) method has been presented. Multifunctional buffer layers, such as Sm_0.2Ce_0.8O_1.9-x, SmBiO₃/NiO(200) have been fabricated via polymer-assisted chemical solution deposition (PACSD) method and surface oxidation epitaxial method. YBa₂Cu₃O₇ (YBCO) superconducting layers have been prepared by partial-melting process. A full process of making CCs using fluorine-free all-CSD method has been demonstrated on reel-to-reel facilities via slot-die coating and drying technology. Long CCs with critical current density J_c > 1 MA/cm² at 77 Kin self-field have been fabricated, demonstrating the feasibility of the full CSD technology in making quality CCs.

Preparation of EuBCO Epitaxial and Textured Films by F-Free Polymer-Assisted Chemical Solution Deposition Method

Epitaxial and textured EuBa2Cu3O7-x(EuBCO) superconductive films were prepared via a F-free polymer-assisted chemical solution deposition (PACSD) method on LaAlO3 (LAO) single crystal substrate in nitrogen atmosphere. Because of the fluorine-free metal organic system, no harmful gas was produced during processing by the PA-CSD method. The film morphorlogy, phase composition, texture and the superconducting critical temperature (Tc) of EuBCO films were investigated by x-ray diffraction (XRD),φ-scan, ω-scan rocking curves, an environmental scanning electron microscope (ESEM) and four-probe method. The Jc value of the EuBCO film in self-field at 77K was measured by using Jc-scan Leipzig system. The results shoed that a denser microstructure and better biaxial texture EuBCO film after a high temperature treatment with a superconducting critical temperature (Tc) of 91K was obtained . The critical current density (Jc) reached 2.4MA/cm2 at 77K in the self-field.

YBa2Cu3O7-z superconducting coated conductors by chemical solution deposition approach

YBa2Cu3O7-δ (YBCO) superconducting coated conductors were prepared on SmBiO3 (SBO) buffered substrates by chemical solution deposition approach. In this work, SBO buffer layers with a rapid decomposition process were heat treated less than 2 h. The SBO buffer layers deposited on LaAlO3, yttria-stabilised zirconium and NiO-buffered NiW substrates possess pure SBO (l00) X-ray diffraction peaks and dense as well as smooth surface microstructures. And YBCO superconducting layers with c-axis texture and dense morphology were successfully fabricated on different SBO-buffered substrates, with superconducting transition temperature Tc of 90 K and critical current density (77 K, self-field) above 1 MA cm−2. This could offer a promising alternative to low cost and high-performance preparation of YBCO superconducting coated conductors.

YDyxBa2Cu3O7-δ Epitaxial Films Prepared by Chemical Solution Deposition

YBa2Cu3O7-δ (YBCO) coated conductors have wide-ranging potential in large scale applications, such as, superconducting maglev trains and superconducting electric cables, but low current carrying capability restrains the practical application of YBCO coated conductors at high temperatures and high magnetic fields. It is crucial to develop YBCO coated conductors with high flux pinning capability. In this paper, epitaxial, dense, smooth and crack-free YDyxBa2Cu3O7-δ (x = 0~0.5) films were prepared on a LaAlO3 (LAO) single crystal substrate via a fluorine-free polymer-assisted metal organic deposition (PA-MOD) method. The effects of Dy addition on the microstructure and superconducting character of YBCO films were investigated. The all films show a strong c-axis orientation and good texture in-plane and out of plane. The Dy addition to the YBCO film hardly affects the critical temperature of YBCO superconductor. The irreversibility fields of YBCO films can be improved with the Dy addition x = 0.5 compared to the pure YBCO film but decreased in the x = 0.3 sample.