Browsing by Author "LEE, WH"

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ANISOTROPIC AC-SUSCEPTIBILITY RESPONSE OF A MELT-TEXTURED YBCO SUPERCONDUCTOR
(1991-12-01)
CHEN, YC
;
CHEN, K
;
HSU, SW
;
TSENG, TY
;
LU, SW
We report on low field measurements of the out-of-plane (c-axis parallel-to H) and in-plane (c-axis perpendicular-to H) ac susceptibilities of a melt-textured YBa2Cu3Ox superconductor with high transport J(c). With the field parallel to the ab-plane of the sample, an obvious second peak appears in the imaginary part of chi(ac) at T almost-equal-to 81 K with a width of 2-4 K depending on the ac field amplitude, which may be due to the interlayer weak-links in the melt-textured samples.
EFFECT OF AG2O ADDITIVE ON MICROSTRUCTURE AND SUPERCONDUCTIVITY OF THE TL2BA2CA2CU3OY COMPOUND
(1993-06-21)
KOO, HS
;
HURNG, WM
;
LEE, WH
;
TSENG, TY
;
CHEN, M
A series of Ag-doped Tl2Ba2Ca2Cu3Oy superconducting Oxides were prepared by a solid-state reaction and the influence of Ag2O content, with a varying molar ratio which ranged from 0 to 1.0, was also investigated. The normal-state resistance of the samples decreased with an increase in the content of Ag2O additive, while the critical superconducting temperatures of the Ag-doped samples increased once the Ag2O content was increased. The doping of the silver oxide was indicated from the results of the x-ray diffraction pattern to be favorable to the formation of the three CuO layers with a high-T(c) phase T12Ba2Ca2Cu3Oy. The diamagnetic Property of the samples was also confirmed by the magnetic measurements to become enhanced by doping with silver oxide. The platelike grains of Tl2 Ba2CaCu2Oy phase Were Observed from scanning electron micrographs to be primarily present in the undoped sample, while the amount of the needlelike Tl2Ba2Ca2Cu3Oy grain increased with an increase in the doping amount of Ag2O.
HIGH-TC SUPERCONDUCTING OXIDE FILM PREPARED BY SPRAY PYROLYSIS COATING
(1990-11-01)
KOO, HS
;
TU, GC
;
CHU, JJ
;
LEE, WH
;
WU, PT
MAGNETIC-RELAXATION IN A AG-SHEATHED HIGH-JC BI-PB-SR-CA-CU-O SUPERCONDUCTING TAPE
(1991-12-01)
CHEN, K
;
LEE, WH
;
HORNG, L
;
YANG, TJ
;
電子物理學系
The magnetic relaxation and magnetization curves were studied on the Ag-sheathed and highly c-axis oriented Bi-Pb-Sr-Ca-Cu-O tape with transport J(c) > 10(4) A/cm2 at 77 K. Zero-field-cooled (ZFC) in-field relaxation for applied field perpendicular to the sample a-b plane was investigated. It was found that the field-dependent relaxation rate had a maximum in the certain applied field at various temperatures. The applied field at this maximum was greater than H*, the first field for which currents flow through the entire volume of the sample in the Bean's critical state model. Pinning energies were estimated at the maximal relaxation rate in a series of temperatures.