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Kim H.S.,Korea Electrotechnology Research Institute | Oh S.S.,Korea Electrotechnology Research Institute | Lee N.J.,Korea Electrotechnology Research Institute | Jang S.H.,Korea Electrotechnology Research Institute | And 6 more authors.
Physica C: Superconductivity and its Applications | Year: 2011

Sm1+xBa2-xCu3+ yO7-δ (SmBCO) films were directly deposited on the epi-MgO/IBAD-MgO/Y2O3/Al 2O3/Hastelloy template by co-evaporation using the evaporation using drum in dual chambers (EDDC) system without the buffer layer in order to investigate the effect of the composition ratios on superconducting property, microstructure and texture of SmBCO film. The films with gradient composition ratios of Sm:Ba:Cu were deposited using a shield with an opening which was placed between the substrate and the boats. The highest Ic of 52 A (corresponding to Jc = 1.6 MA/cm2 and a thickness of 800 nm) was observed at 77 K in self field at a composition x = 0.01-0.05 and y = -0.23 to -0.46. When the composition ratio is outside this range, the Ic value rapidly decreased. The superconducting critical current was highly dependent on the composition ratio. As the composition ratio is farther away from that of the highest Ic, the SmBCO (1 0 3) peak intensity increased and the amount of a-axis oriented parts increased. A dense microstructure with round-shape grains was observed in the region showing the highest Ic. The optimum composition ratio can be found by analyzing films deposited with variable deposition rates of each depositing element. © 2011 Elsevier B.V. All rights reserved. Source

Kim H.-S.,Korea Electrotechnology Research Institute | Oh S.-S.,Korea Electrotechnology Research Institute | Lee N.-J.,Korea Advanced Institute of Science and Technology | Baik S.-K.,Korea Electrotechnology Research Institute | And 7 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2010

The Hall probe measurement system was used to measure the critical current distribution of superconducting coated conductor. The system consists of reel to reel moving apparatus, 7 array Hall probe, a rotary encoder and permanent magnet. The magnetic field profile across the width of superconducting coated conductor using Bean's critical state model was calculated. The effect of various parameters of the formulas on the magnetic field distribution and the effect of shape and size of artificial defects, which were formed on the surface of SmBa2Cu3O7-d(SmBCO) coated conductor using laser marking system, on the Hall probe magnetic field signal of the Hall probe measurement system was investigated. © 2006 IEEE. Source

Kim K.L.,Korea University | Hwang S.J.,Korea University | Hahn S.,Massachusetts Institute of Technology | Moon S.H.,Nano and Advanced Materials Corporation | Lee H.G.,Korea University
Journal of the Korea Institute of Applied Superconductivity and Cryogenics | Year: 2010

The properties of the conductor-mechanical, thermal, and electrical-are the key information in the design and optimization of superconducting coils. Particularly, in devices using second generation (2G) high temperature superconductors (HTS), whose base materials (for example, the substrate or stabilizer) and dimensions are adjustable, a design process for conductor optimization is one of the most important factors to enhance the electrical and thermal performance of the superconducting system while reducing the cost of the conductor. Recently, we developed a numerical program that can be used for 2G HTS conductor optimization. Focusing on the five major properties, viz. the electrical resistivity, heat capacity, thermal conductivity, Z-value, and enthalpy, the program includes an electronic database of the major base materials and calculates the equivalent properties of the 2G HTS conductors using the dimensions of the base materials as the input values. In this study, the developed program is introduced and its validity is verified by comparing the experimental and simulated results obtained with several 2G HTS conductors. Source

Ko K.P.,Seoul National University | Choi S.M.,Seoul National University | Kim Y.C.,Seoul National University | Lee J.W.,Seoul National University | And 3 more authors.
Physica C: Superconductivity and its Applications | Year: 2011

We report the effects of BSO addition on the crystallinity, texture, and the field dependency of critical current density (Jc) of GdBCO coated conductors (CCs) prepared by pulsed laser deposition (PLD). Undoped and BSO-doped GdBCO films showed only c-axis oriented growth, and the incorporated BSO nanorods exhibited epitaxial relationship with the GdBCO matrix. In comparison with undoped film, BSO-doped GdBCO film exhibited greatly enhanced Jc and higher pinning force densities in the entire field region of 0-5 T (H//c) at 77 and 65 K. The BSO-doped GdBCO film showed the maximum pinning force densities (Fp) of 6.5 GN/m3 (77 K, H//c) and 32.5 GN/m3 (65 K, H//c), ∼2.8 times higher than those of the undoped sample. Cross-sectional TEM analyses exhibited nano-structured BSO nanorods roughly aligned along the c-axis of the GdBCO film, which are believed effective flux pinning centers responsible for strongly improved critical current densities in magnetic fields. © 2011 Elsevier B.V. All rights reserved. Source

Lee J.W.,Seoul National University | Shin G.M.,Seoul National University | Moon S.H.,Nano and Advanced Materials Corporation | Yoo S.I.,Seoul National University
Physica C: Superconductivity and its Applications | Year: 2010

We report a successful fabrication of high-Jc GdBa 2Cu3O7 δ (GdBCO) films by the metal-organic deposition process on the LaAlO3 (LAO) (0 0 1) substrates. The coating solution was prepared by mixing Gd, Cu fluorine-free sources with Ba trifluoroacetate. Samples were dip-coated, pyrolized within 3 h at the temperature up to 400 °C in a humid oxygen atmosphere, and finally fired at various high temperatures in 100 ppm Ar/O2 atmosphere. The GdBCO films fired at 775 and 800 °C exhibited Jc values of ∼2.1 MA/cm2 at 77 K in a self-field, which are attributable to both high Tc,zero values of ∼89 K and high in-plane textures of 1.3-1.4°. Above 800 °C, however, the superconducting properties of GdBCO films are degraded due to the thermal decomposition of GdBCO film in 100 ppm Ar/O2 atmosphere. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. Source

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