Crystalline defects on the nano-scale, which are called artificial pinning centers (APCs), were successfully introduced into high-temperature superconductors (HTS) by nanotechnology, in order to strongly pin the quantized vortices. The critical current densities, Jc, of the HTS films were dramatically improved by APCs. It is possible to form APCs in high-quality epitaxial films, keeping the desired dimensionality, volume fraction, spatial distribution and so on. The in-field Jc of HTS films at 77 K was improved by one order of magnitude compared with previous values using APCs. This technology can be applied to the coated conductor technology in progress, and a high Jc has already been reported. A current outline of the research is described in this review.

https://iopscience.iop.org/article/10.1088/0953-2048/23/1/014001/pdf

Artificial pinning center technology to enhance vortex pinning in YBCO coated conductors

This work covers the high-temperature superconducting (HTS) technologies based on the highlights in recent achievements in the applied HTS field in China. Its comprehensive coverage includes practical HTS material manufacturing and characterization, large-scale applications, and electronic applications. The applied HTS technologies have been well enabled to build applicable devices, and their characteristics have been well verified in the HTS devices developed to be industrialized for practical applications. The highlighted HTS devices and their performance details reveal the trend and the necessary improvement required to reach the goal of industrial applications of HTS technologies.

Enabling High-Temperature Superconducting Technologies Toward Practical Applications

The magnitude and anisotropy of the critical current density Jc as well as the irreversibility field Hirr of BaZrO3 (BZO)-doped YBa2Cu3O7 ? x?(YBCO) thin films are determined by both the amount of BZO and the deposition temperature. The influence of these two parameters was investigated on BZO/YBCO quasi-multilayers in two temperature series with different doping amounts (4 and 9?vol% BZO). The deposition temperature was varied between 790 and 850??C. The samples show an increase in Hirr, logarithmic peaks in Jc(B) and strong c-axis peaks in Jc(?). Nevertheless, the two series reveal opposite temperature trends for Jc: whereas Jc?increases with temperature for 4?vol% BZO, it decreases for 9?vol%. This is explained by a diffusion model for the formation and growth of BZO nanocolumns and an optimum balance between correlated and random pinning centres for high Jc. TEM images support this model.

Nanocolumns in YBa2Cu3O7 − x/BaZrO3 quasi-multilayers: formation and influence on superconducting properties

We report on large magnetoresistance in ferromagnet/superconductor/ferromagnet trilayer structures made of La_(0.7)Ca_(0.3)MnO_(3) and YBa_(2)Cu_(3)O_(7). We find that the shape and height of the magnetoresistance peaks are not modified when the relative orientation of current and magnetic field is changed from parallel to perpendicular. Furthermore, we find that the temperature shift of the resistance curves is independent of current and of the sweep rate of the magnetic field. These observations favor the view that the magnetoresistance phenomenon originates in the spin dependent transport of quasiparticles transmitted from the ferromagnetic electrodes into the superconductor, and rule out interpretations in terms of spontaneous vortices or anisotropic magnetoresistance of the ferromagnetic layers.

Spin-dependent magnetoresistance of ferromagnet/superconductor/ferromagnet La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(7-δ)/La_(0.7)Ca_(0.3)MnO_(3) trilayers

Preparation and characterization of a biaxially textured Gd2Zr2O7 and Ce0.9La0.1O2 ? y?(CLO, cap)/Gd2Zr2O7 (GZO, barrier) buffer layer stack by the metal?organic deposition route are reported. YBa2Cu3O7 ? d (YBCO) superconductor films were deposited by the pulsed-laser deposition (PLD) technique to assess the efficiency of such a novel buffer layer stack. Biaxial texture quality and morphology of the buffer layers and the YBCO superconductor films were fully characterized. The surface crystallinity of the buffer layers is studied by the electron backscatter diffraction technique. It is revealed that post-annealing GZO films in 2%?H2 in Ar is an effective way to improve the surface crystallinity. As a result, a highly textured CLO film can grow directly on the GZO film at a lower crystallization temperature. The critical current density of a YBCOPLD film is higher than 1?MA?cm ? 2 (@77?K, in self-field), demonstrating that the novel CLO/GZO stack is very promising for further development of low cost buffer layer architectures for coated conductors.

http://iopscience.iop.org/article/10.1088/0953-2048/25/1/015008/pdf

Development of all chemical solution derived Ce0.9La0.1O2 − y/Gd2Zr2O7 buffer layer stack for coated conductors: influence of the post-annealing process on surface crystallinity

In the present work, the single buffer layers of La2Zr2O7 (LZO) with different thicknesses were prepared using pulsed laser deposition (PLD) on highly textured Ni?5?at.%W tapes for YBa2Cu3O7??-coated conductors. The highly textured LZO layers are obtained on the metallic substrates, making the subsequent epitaxial growth of superconducting YBa2Cu3O7?? layers feasible. The superconducting transition temperature increases as the LZO thickness increases up to 240?nm, achieving a value of Tc of more than 92?K with a narrow transition width less than 1?K. Inductive measurement reveals that the critical current density (Jc) reaches 0.77?MA?cm?2 at 77?K in self-field, showing that the single buffer of LZO is comparable to standard buffer architectures such as CeO2/YSZ/Y2O3 or CeO2/LZO. This implies that the LZO as a single buffer layer is promising for the simplification of the preparation process, leading to cost-effective coated conductors.

http://iopscience.iop.org/article/10.1088/0953-2048/22/9/095005/pdf

Thickness effect of La2Zr2O7 single buffers on metallic substrates using pulsed laser deposition for YBa2Cu3O7−δ-coated conductors

Magnetic dependent proximity effects of superconductivity and ferromagnetism in Y Ba2Cu3O7−ō/La1−xCaxMnO3 bilayers

A series of Gd 2 Zr 2 O 7 (GZO) single buffer layers with different thicknesses were epitaxially grown on highly textured Ni–5 at.% W tapes using pulsed laser deposition. These allow the subsequent growth of high-quality superconducting YBa 2 Cu 3 O 7−δ layers. The superconducting transition temperature T c reaches a maximum value of 92.4 K as well as a narrow transition width of 0.8 K for the optimized GZO layer thickness. The inductive measurements show the critical current density as high as 1.2 MA/cm 2 at 77 K in self-field, indicating that a GZO single buffer layer is a suitable alternative for simplifying the second generation high T c superconducting coated conductors architecture.

Deposition of Gd2Zr2O7 single buffer layers with different thickness for YBa2Cu3O7-δ coated conductors on metallic substrates

In the present work, La 2 Zr 2 O 7 (LZO) buffer layers were deposited using pulsed laser deposition (PLD) on various metallic substrates including epitaxial pure Ni on a LaAlO 3 (LAO) substrate as well as highly textured Ni–5 at.%W tapes. It is shown that the LZO deposited on pure Ni-buffered LAO exhibits a mixed orientation while LZO on Ni–5 at.%W grows epitaxially. This difference may be explained by the existence of a sulphur superstructure on the surface of Ni–5 at.%W tapes, promoting the epitaxial (0 0  l ) nucleation of seed layers. Highly textured YBa 2 Cu 3 O 7− δ layers were prepared either by using a single buffer layer of LZO or bilayer buffers of CeO 2 /LZO on Ni–5 at.%W. The superconducting transition temperature ( T c ) increases with the LZO thickness, reaching a value of 90 K with a very narrow transition width (1.5 K) for 240 nm thick LZO layers. Inductive J c measurements at 77 K in self-field show a value of about 0.96 MA/cm 2 for the thickest LZO layers, which is comparable to the value observed on standard buffer architectures such as CeO 2 /YSZ/Y 2 O 3 .

Epitaxial growth of La2Zr2O7 buffer layers for YBa2Cu3O7−δ coated conductors on metallic substrates using pulsed laser deposition

A series of quasimultilayers consisting of YBa2Cu3O7−δ (YBCO) and SrRuO3 (SRO), namely, p×(YBCO(m)/SRO(n)) (p: repetition periods; m: YBCO pulse number; n: SRO pulse number), is prepared on single crystal SrTiO3 by pulsed laser deposition. X-ray diffraction measurements reveal that a heterogeneous phase of Ba2YRuO6 is formed due to the chemical reaction, while both the in-plane and out-of-plane textures of the present quasimultilayers are as good as in the pure YBCO films. The content of Ba2YRuO6 increases as the pulse number of SRO increases, leading to the decrease in superconducting transition temperature (Tc). There is no obvious difference in Tc between the samples with the different deposition sequence orders of YBCO and SRO. The magnetic field dependence of critical current density (Jc) shows an enhanced flux pinning at relatively high fields for all the present quasimultilayers, which occurs at different ranges of fields depending on the applied temperatures. The Jc of the quasimultilayers can rea...

Liliang Ying

Papers

Thickness effect of La2Zr2O7 single buffers on metallic substrates using pulsed laser deposition for YBa2Cu3O7−δ-coated conductors

Magnetic dependent proximity effects of superconductivity and ferromagnetism in Y Ba2Cu3O7−ō/La1−xCaxMnO3 bilayers

Deposition of Gd2Zr2O7 single buffer layers with different thickness for YBa2Cu3O7-δ coated conductors on metallic substrates

Epitaxial growth of La2Zr2O7 buffer layers for YBa2Cu3O7−δ coated conductors on metallic substrates using pulsed laser deposition

Heteroperovskite phase formation and magnetotransport properties of YBa2Cu3O7−x/SrRuO3 quasimultilayers