Browsing by Author "Kao, FS"

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A study on the high-pressure synthesis and properties of praseodymium-substituted R(2)Ba(4)Cu(7)O(14+delta) (R=Nd, Eu, Tm) cuprates
(1996-04-01)
Kao, FS
;
Chen, TM
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The formation of phases in the (R(1-x)Pr(x))(2)Ba4Cu7O?(14+delta (R = Nd, Eu, Tm; Pr-doped R247 phases) system with x = 0 - 0.5 was investigated. Samples of the above three series were synthesized at 980 degrees C at 25 bar O-2, followed by annealing at 300 degrees C under 130 bar O-2 for 30 hours. Oxygen content of the samples has been determined by iodometric titration. X-ray diffraction indicated that nearly single-phased samples were obtained with err < 0.4, 0.5 and 0.5 for R = Nd, Eu and Tm, respectively, and the cell dimension of the Pr-doped R247 phases was found to expand steadily with increasing Pr content. Field-cooled temperature-dependent magnetization measurements showed that T-c of the Pr-doped R247 decreased with increasing Pr content. We have compared the dT(c)/dx for the three series with R = Nd, Eu and Tm with that for R = Y as a function of size of R(3+) ions and the results are discussed. In addition, the field-dependent magnetization studies at 5 K for a series of (Eu1-xPrx)(2)Ba4Cu7O14+delta samples with x = 0, 0.2, and 0.4 are also reported.
A study on the luminescent properties of new green-emitting terbium-activated CaIn2O4 : xTb phosphors
(2002-03-01)
Kao, FS
;
Chen, TM
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應用化學系
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Department of Applied Chemistry
Calcium indate phosphors have been prepared by solid-state reactions at 1400 degreesC. This indate matrix permits photoluminescence when doped with terbium. It was found that under ultraviolet excitation with a wavelength of 254nm the phosphors revealed yellowish green luminescence that was attributed to the transitions from D-5(4) excited state to F-7(J) multiplet ground states of Tb3+ ions. The powder X-ray diffraction, photoluminescence spectra, brightness, fluorescence decay lifetime, and chromatic characteristics of the Tb3+-activated CaIn2O4 phosphors were systematically investigated and reported. (C) 2002 Elsevier Science B.V. All rights reserved.
A study on the luminescent properties of praseodymium-activated CaIn2O4 phosphors
(2000-12-01)
Kao, FS
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The photoluminescent (PL) properties and decay lifetime of a series of unprecedented praseodymium-activated calcium indates (CaIn2O4:xPr(3+)) have been investigated. The CaIn2O4:xPr(3+) (x = 6.25 x 10(-4), 0.5%, 1%, and 2%) was found to exhibit orange emission under ultraviolet excitation. With different levels of Pr3+ doping, the X-ray diffraction profiles, photoluminescence spectra and fluorescence decay lifetime as a function of Pr3+ concentration, and chromatic characteristics of CaIn2O4:xPr(3+) with different x's have been systematically investigated. The analysis of PL emission and excitation spectra, decay lifetime, and comparison of chromaticity coordinates and hues for CaIn2O4:xPr(3+) are presented and their implications are discussed. (C) 2000 Academic Press.
A study on the luminescent properties of red-emitting praseodymium-activated SrIn2O4 phosphors
(2001-01-01)
Kao, FS
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The photoluminescent (PL) properties of new red-emitting praseodymium-activated strontium indates have been investigated. A series of SrIn2O4:xPr(3+) (x = 6.25 x 10(-4), 0,5%, 2%, and 4%) phases were synthesized and found to exhibit red emission. With different levels of Pr3+ doping, the absolute brightness, CIE chromatic characteristics, PL and cathodoluminescence spectra, and luminescence decay lifetime (tau (R)) for SrIn2O4:xPr(3+) have been systematically investigated. The results are reported and their implications are discussed. (C) 2001 Academic Press.
The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth based R2Ba4Cu7O14+delta (R = Nd, Sm, Eu, Gd, Ho, Tm)
(1997-08-01)
Chen, TM
;
Lai, YL
;
Kao, FS
;
交大名義發表
;
應用化學系
Samples of the (R1-xPrx)(2)Ba4Cu7O14+delta (R = Nd, Sm, Eu, Gd, Ho, Tm; Pr-doped R247) systems with x = 0 to 1.0 and with an increment of 0.1 in x was investigated. Single-phased samples were obtained with substitution limit equal to 0.4, 0.6, 0.5, 0.6, 0.8 and 0.5 for phases with R = Nd, Sm, Eu, Gd, Ho and Tm, respectively, as indicated by x-ray diffraction (XRD) data. T-c's of the Pr-doped R247 phases were found to be suppressed from 66, 69, 75, 70, 92 and 88K down to 41K (x=0.3), 20 K (x=0.4), 52K(x = 0.4), 18K (x = 0.5), 8K (x = 0.7) and 50K (x = 0.4) and the corresponding composition coefficients of T-c, dT(c)/dx, were found to be -41.3, -50.4, -28.0, -47.7, -53.0 and -46.0 K/Pr-atom per formula unit for Pr-doped R247 phases with R = Nd, Sm, Eu, Gd, Ho and Tm, respectively. The variation of T-c and dT(c)/dx coefficients ofthe Pr-doped R247 phases upon Pr doping are described and their implcations are discussed.
The high-pressure synthesis and characterization of some praseodymium-substituted rare-earth-based R2Ba4Cu7O14+delta (R = Nd, Eu, Tm)
(1997-08-01)
Chen, TM
;
Kao, FS
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The formation of phases in the (R1-xPrx)(2)Ba4Cu7O14+delta (Pr-doped R247; R = Nd, Eu, Tm) system with x = 0-1.0 was investigated. Samples of the title series were synthesized at 980-990 degrees C at 25 bar O-2, followed by annealing at 300 degrees C under 130 bar O-2 for 30 hr. Oxygen content of the samples has been determined by iodometric titration, Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R = Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements, With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T-c's) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T-c's of R247 (R = Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R3+ radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu1-xPrx)(2)Ba4Cu7O14+delta samples with x = 0, 0.2, and 0.4, respectively, are also reported. (C) 1997 Academic Press.