Browsing by Author "LIN, LF"

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AMBIENT-PRESSURE SYNTHESIS OF SUPERCONDUCTING YBA2CU4O8
(1993-12-01)
LIN, LF
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CHEN, TM
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交大名義發表
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應用化學系
;
National Chiao Tung University
A highly homogeneous and monophasic high-T(c) superconductor YBa2Cu4O8 with T(c(zero)) of 75 K and fine grain size has been synthesized at 1 atm of oxygen via a route employing polymeric ethylene glycol/citric acid (EG/CA) precursors. In addition to the chemistry involved in the preparation, the effect of preparation temperature, time of processing and EG/CA ratio in the precursor on the formation and superconductivity of the 124 phase was systematically investigated. The results of X-ray diffraction, the temperature dependence of resistivity and dc magnetic susceptibility, and the SEM microstructure studies on 124 synthesized under different conditions were also summarized.
CHEMICAL SYNTHESIS AND CHARACTERIZATION OF SUPERCONDUCTING YBA2CU4O8 AT AMBIENT-PRESSURE
(1994-12-01)
CHEN, TM
;
LIN, LF
;
應用化學系
;
Department of Applied Chemistry
A monophasic high-T-c superconductor YBa2Cu4O8 with T-c(onset) 80 K and fme grain size has beeen synthesized under oxygen at 1 bar employing metal-ethandiol/citric acid (EG/CA) polyester complex precursors. In addition to the preparation, we report the results of infrared (IR) spectra, thermogravimetric analysis (TGA), and X-ray diffraction (XRD) relevant to preparation of the YBa2Cu4O8 superconductor. The effect of temperature of preparation and precursor compositions (i.e. EG/CA molar ratio) on the purity and superconductivity of the YBa2Cu4O8 compound was investigated. The temperature dependence of resistivity and normal-state resistivity of the samples varied systematically with the EG/CA ratio in the precursors. T-c(onset) and the width of the superconducting transition for YBa2Cu4O8 samples were determined to be 80 K for all samples and 6 - 9 K, respectively; the latter depended on the corresponding EG/CA ratios in the precursors. The Meissner fraction of YBa2Cu4O8 samples determined from dc magnetization tests was independent of the EG/CA ratio. Polyester precursors can potentially be applied in large-scale preparation of high T-c ceramic-oxide superconductors and superconducting thin firms.