Minghua Pu

The microstructures and superconducting properties of MgB2 bulks prepared by a high-energy milling method

We succeeded in the synthesis of high-Jc MgB2 bulks via high energy ball-milling of elemental Mg and B powder at ambient temperatures. Alternatively to longtime mechanical alloying technique, the mixed powder was ball-milled for only 1h and the completed reaction is achieved by subsequent annealing. The correlations among synthesis parameters, microstructures and superconducting properties in MgB2 bulks were investigated. Samples were characterized by XRD and SEM, and the magnetization properties were examined in a SQUID magnetometer. The highJc, approximately 1.7× 10 A/cm(15K, 0.59T), and improved flux pinning were attribute to a large number of grain boundaries provided by small grain size.

Preparation and Performance of the Sm0.2Ce0.8O1.9-x Single Buffer Layer Fabricated with Dip-Coating

Abstract An epitaxial Sm 0.2 Ce 0.8 O 1.9- x (SCO) single buffer layer with thickness of about 250 nm has been deposited via dip-coating polymer-assisted chemical solution deposition (PACSD) approach for YBCO coated conductors on bi-axially textured Ni-5%W (200) alloy substrate. Flat, crack-free SCO films with sharp (200) c -axis orientation and texture have been obtained by carefully controlling the concentration of precursor solution, withdrawing speed, annealing temperature and dwelling time. Leaving other three factors unchanged, focuses on the influence of different withdrawing speeds on the performance of the SCO buffer layer has been focused on. YBCO superconducting layer has been deposited equally via dip-coating PACSD approach on the SCO-buffered NiW, showing a bi-axially texture. Micro-structural investigations revealed a homogeneous surface structure. Both of these indicate that SCO single buffer layer can function well as template. The approach has shown a promising way to fabricate long-length, low-cost YBCO coated conductors.

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.

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.

Influence of Lattice Mismatch in Preparation of the SmBiO3 Buffer Layer by a CSD Method

SmBiO3 (SBO) buffer layers have been prepared via a rapid chemical solution deposition (CSD) method on different substrates, such as LaAlO3 (LAO), yttrium-stabilized zirconium (YSZ), and NiO-buffered NiW (NiO/NiW). The SBO buffer layers deposited on LAO, YSZ, and NiO/NiW substrates have strong SBO (200) peaks and smooth surface. The SBO buffer layer is difficult to grow on the MgO substrate. The lattice mismatches between SBO buffer layers and different substrates have great influence on the epitaxial films quality. With the increase in lattice mismatch, the optimum texture temperature ranges become narrower, also the texture degrees of SBO epitaxial films decrease, and the SBO buffer layers become rougher.

Annealing Conditions of SCO Buffer Layer via Slot-Die Technique

A biaxially textured Sm0.2Ce0.8O1.9-x (SCO) single buffer layer has been prepared on textured Ni-5%W alloy substrate using slot-die coating for REBCO (RE = Y, La, and other lanthanides)-coated conductors. A smooth, uniform, and crack-free SCO buffer layer with sharp (200) c-axis orientation has been obtained by controlling the annealing conditions, including the decomposition rate of SCO precursor film, the flow rate of protective gas, the heat treatment temperature, and time.