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1
Superconducting Properties of Ba2Ca7Cu8O16(O0.8+δF1.2) Studied via Reversible Magnetization

권용태,김영철,김헌정,Akira Iyo,Parasharam M. Shirage 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.11
The Ba2Ca7Cu8O16(O0.8+δF1.2) (F-0278) superconductor with 8 CuO2 planes in the structural unit was investigated by analyzing the reversible magnetization based on the Hao-Clem model and fluctuation theories. In spite of the superconducting block (SCB) being thicker than the charge reservoir block (CRB), the analysis clearly revealed two-dimensional (2D) superconducting properties in F-0278, such as a strong temperature dependence of the Ginzburg parameter κ and a relatively short effective interlayer distance. The extreme 2D behavior can be understood in terms of the significant charge imbalance in the SCB, which was previously proposed to exist in F-0278, where the carriers are distributed quite unequally to crystallographically different CuO2 planes; i.e., the outer planes (OPs) adjacent to the CRB always contain more carriers than the inner planes (IPs). The 2D nature of F-0278 indicates a significant or complete suppression of the superconductivity in the IPs. The important superconducting parameters were also obtained from the analysis.
2
A new process to prepare thick bufferless Tl-1223/Ag high temperature superconducting coated conductors using electrodeposition

Jeong, D Y,Kim, Y H,Shirage, P M,Kim, S Y,Horiuchi, S,Lee, J H IOP Publishing Ltd 2007 Superconductor science & technology Vol.20 No.12
- 원문보기
The present study shows general characteristic features of processes such as electrodeposition, drying, and heat-treatment, involved in the preparation of bufferless Tl-1223/Ag superconducting coated conductors by using an electrodeposition method, the details of which have not been reported in the literature. The importance of the present study, however, lies in a new process to make a thick Tl-1223 superconducting layer by using electrodeposition. In the new method, a relatively thin Tl-1223 precursor film is firstly electrodeposited on an Ag sheet, dried, and then heat-treated for phase transformation to superconducting phases to assign conductivity to the film. Then Tl-1223 precursor film is electrodeposited again on the heat-treated superconducting film, dried, and heat-treated. The process of electrodeposition, drying, and heat-treatment can be repeated many times to prepare a very thick superconducting layer. In the present study, a 2–3 µm thick Tl-1223 layer was prepared on a <img SRC='http://ej.iop.org/images/0953-2048/20/12/026/sust252315ieqn1.gif' ALIGN='MIDDLE' ALT='\{113\}\langle 121\rangle '/> intensified Ag sheet by repeating the process once. Even though Jc values in thick Tl-1223/Ag were quite low mainly due to material loss during heat-treatment, the microstructure analysis indicated that Tl-1223 layers were epitaxially grown on the <img SRC='http://ej.iop.org/images/0953-2048/20/12/026/sust252315ieqn2.gif' ALIGN='MIDDLE' ALT='(113)\langle 121\rangle '/> intensified Ag sheets provided that the Ag surfaces were flat and clean.
3
The Pre-Oxidation Process of Electropolishing for the Textured {113} <121> Ag substrate for Tl-1223 Superconductor Substrate

( Y. H. Kim ),( D. Y. Jeong ),( P. M. Shirage ),( S. Y. Kim ),( U. C. Chung ),( W. S Chung ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.3
- 원문보기
- 복사/대출신청
The surface roughness of a substrate is typically influenced by grain boundaries, grooves and voids. In an effort to improve the surface roughness, a textured {113} <121> Ag substrate was electropolished using a new method that causes the formation of an oxidation layer at the constant current density before electropolishing at a constant voltage of 1.75 V vs. SCE. The constant current density and potential were determined using the anodic polarization method. The pH effect for the optimized electropolishing condition was also investigated by adding phosphoric acid. The edges of the grain boundaries, grooves and voids became smoother when a constant current density was supplied with the pre-oxidation. A RMS (root mean square) value of 5.90-nm regarding the surface roughness of the Ag substrate was obtained without a final surface treatment before electropolishing, while a RMS surface roughness value of 34.12-nm was obtained for an Ag substrate that was given a final surface treatment for mechanical polishing.