Browsing by Author "Wang, Ming-Fang"

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Enhanced catalytic activity of Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
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Chen, Kuei-Bo
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Wang, Ming-Fang
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Weng, Sheng-Feng
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Lee, Chi-Shen
Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Enhanced catalytic activity of Ce1-xMxO2 (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
;
Chen, Kuei-Bo
;
Wang, Ming-Fang
;
Weng, Sheng-Feng
;
Lee, Chi-Shen
Ce1-xMxO2 (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Structural, spectroscopic and photolurninescence studies of LiEu(WO4)(2-x)(MoO4), as a near-UV convertible phosphor
(2007-02-01)
Chiu, Chuang-Hung
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Wang, Ming-Fang
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Lee, Chi-Shen
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Chen, Teng-Ming
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應用化學系
A series of lithium europium double tungsto-molybdate phosphors LiEu(WO4)(2-),(MoO4), (X = 0, 0.4, 0.8, 1.2, 1.6, 2.0) have been synthesized by solid-state reactions and their crystal structure, optical and luminescent properties were studied. As the molybdate content increases, the intensity of the D-5(0) -> F-7(2) emission of Eu3+ activated at wavelength of 396 mn was found to increase and reach a maximum when the relative ratio of Mo/W is 2:0. These changes were found to be accompanied with the changes in the spectral feature, which can be attributed to the crystal field splitting of the D-5(0) -> F-7(2) transition. As the molybdate content increases the emission intensity of the 615 nm peak also increases. The intense red-emission of the tungstomolybdate phosphors under near-UV excitation suggests them to be potential candidate for white light generation by using near-UV LEDs. In this study the effect of chemical compositions and crystal structure on the photolumineseent properties of LiEu(WO4)(2-x)(MoO4), is investigated and discussed. (c) 2006 Elsevier Inc. All rights reserved.
Synthesis and characterization of a new quaternary selenide Sr(3)GeSb(2)Se(8)
(2008-09-01)
Yu, Ching-Yi
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Wang, Ming-Fang
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Chung, Ming-Yang
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Jang, Shyue-Ming
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Huang, Jih-Chen
A new quaternary selenide Sr(3)GeSb(2)Se(8) has been synthesized at 750 degrees C from pure elements in a stoichiometric ratio under vacuum. The product as-synthesized is characterized by single-crystal X-ray diffraction, diffuse reflectance spectroscopy, and thermoanalysis. The title compound crystallizes in the orthorhombic space group Pnma with a = 12.633(4) angstrom, b = 4.301(1) angstrom, c = 28.693(7) angstrom, V = 1558.8(8) angstrom(3), Z = 4, R(1)/wR(2) = 0.0582/0.1221, and GOF = 1.077. The structure of Sr(3)GeSb(2)Se(8) features a new structural type that consists of one-dimensional chains of vertex-sharing tetrahedra (1)(infinity)[MSe(3)] (M = Ge/Sb) and fused double chains of edge-shared square pyramids (1)(infinity)[M(2)Se(5)], which are held together by Sr(2+) ions. A band gap of 0.75 eV for Sr(3)GeSb(2)Se(8) was derived from its diffuse reflectance spectrum. (C) 2007 Elsevier Masson SAS. All rights reserved.
Synthesis and characterization of quaternary chalcogenides InSn(2)Bi(3)Se(8) and In(0.2)Sn(6)Bi(1.8)Se(9)
(2009-06-01)
Wang, Ming-Fang
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Jang, Shyue-Ming
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Huang, Jih-Chen
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Lee, Chi-Shen
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應用化學系
Quaternary chalcogenides InSn(2)Bi(3)Se(8) and In(0.2)Sn(6)Bi(1.8)Se(9) were synthesized on direct combination of their elements in stoichiometric ratios at T>800 degrees C under vacuum. Their structures were determined with X-ray diffraction of single crystals. InSn(2)Bi(3)Se(8) crystallizes in monoclinic space group C2/m (No. 12) with a = 13.557(3) angstrom, b = 4.1299(8) angstrom, c = 15.252(3)angstrom, beta = 115.73(3)degrees, V = 769.3(3) angstrom(3), Z = 2, and R(1)/wR(2)/GOF = 0.0206/0.0497/1.092; In(0.2)Sn(6)Bi(1.8)Se(9) crystallizes in orthorhombic space group Cmc2(1) (No. 36) with a = 4.1810(8) angstrom, b = 13.799(3) angstrom, c = 31.953(6) angstrom, V=1843.4(6) angstrom(3), Z = 4, and R(1)/wR(2)/GOF = 0.0966/0.2327/1.12. InSn(2)Bi(3)Se(8) and In(0.2)Sn(6)Bi(1.8)Se(9) are isostructural with CuBi(5)S(8) and Bi(2)Pb(6)S(9) phases, respectively. The structures of InSn(2)Bi(3)Se(8) and In(0.2)Sn(6)Bi(1.8)Se(9) feature a three-dimensional framework containing slabs of NaCl-(311) type with varied thicknesses. Calculations of the electronic structure and measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps. Both compounds show n-type semiconducting properties with Seebeck coefficients -270 and -230 mu V/K at 300 K for InSn(2)Bi(3)Se(8) and In(0.2)Sn(6)Bi(1.8)Se(9), respectively. (C) 2009 Elsevier Inc. All rights reserved.
Synthesis and characterization of quaternary chalcogenides InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9
(2009-06-01)
Wang, Ming-Fang
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Jang, Shyue-Ming
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Huang, Jih-Chen
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Lee, Chi-Shen
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應用化學系
Quaternary chalcogenides InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 were synthesized on direct combination of their elements in stoichiometric ratios at T>800 degrees C under vacuum. Their structures were determined with X-ray diffraction of single crystals. InSn2Bi3Se8 crystallizes in monoclinic space group C2/m (No. 12) with a = 13.557(3) angstrom, b = 4.1299(8) angstrom, c = 15.252(3)angstrom, beta = 115.73(3)degrees, V = 769.3(3) angstrom(3), Z = 2, and R-1/wR(2)/GOF = 0.0206/0.0497/1.092; In0.2Sn6Bi1.8Se9 crystallizes in orthorhombic space group Cmc2(1) (No. 36) with a = 4.1810(8) angstrom, b = 13.799(3) angstrom, c = 31.953(6) angstrom, V=1843.4(6) angstrom(3), Z = 4, and R-1/wR(2)/GOF = 0.0966/0.2327/1.12. InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 are isostructural with CuBi5S8 and Bi2Pb6S9 phases, respectively. The structures of InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9 feature a three-dimensional framework containing slabs of NaCl-(311) type with varied thicknesses. Calculations of the electronic structure and measurements of electrical conductivity indicate that these materials are semiconductors with narrow band gaps. Both compounds show n-type semiconducting properties with Seebeck coefficients -270 and -230 mu V/K at 300 K for InSn2Bi3Se8 and In0.2Sn6Bi1.8Se9, respectively. (C) 2009 Elsevier Inc. All rights reserved.
Synthesis and Phase Width of Quaternary Selenides Pb(4)In(x)M(6-x)Se(13) (M = Bi, x=2.1-2.8; Sb, x=2)
(2009-07-20)
Wang, Ming-Fang
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Huang, Wen-Hen
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Lee, Chi-Shen
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應用化學系
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Department of Applied Chemistry
Quaternary selenides of Pb(4)In(x)M(6-x)Se(13) (M = Bi, x = 2.1-2.8; Sb, x = 2) were synthesized by solid-state methods, and their structures were determined from X-ray diffraction of single crystals. These compounds are isostructural with Pb(4)In(2)Bi(4)S(13) and crystallize in orthorhombic space group Pbam (No. 55) with Z = 4; the structure features a three-dimensional framework consisting of Z-shaped ribbon units and corner-sharing infinite one-dimensional [InSe(4)](proportional to) chains running parallel to the c-axis, which are connected by Pb atoms to form a three-dimensional structure. Calculations of the band structure and measurements of Seebeck coefficient, electrical conductivity, and diffuse reflectance spectra confirm that these compounds are semiconductors with a narrow band gap. All compounds show semiconducting properties; the Seebeck coefficient of Pb(4)In(2.5)Bi(3.5)Se(13) is -180 mu V/K at 295 K.
Synthesis and Phase Width of Quaternary Selenides Pb4InxM6-xSe13 (M = Bi, x=2.1-2.8; Sb, x=2)
(2009-07-20)
Wang, Ming-Fang
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Huang, Wen-Hen
;
Lee, Chi-Shen
;
應用化學系
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Department of Applied Chemistry
Quaternary selenides of Pb4InxM6-xSe13 (M = Bi, x = 2.1-2.8; Sb, x = 2) were synthesized by solid-state methods, and their structures were determined from X-ray diffraction of single crystals. These compounds are isostructural with Pb4In2Bi4S13 and crystallize in orthorhombic space group Pbam (No. 55) with Z = 4; the structure features a three-dimensional framework consisting of Z-shaped ribbon units and corner-sharing infinite one-dimensional [InSe4](proportional to) chains running parallel to the c-axis, which are connected by Pb atoms to form a three-dimensional structure. Calculations of the band structure and measurements of Seebeck coefficient, electrical conductivity, and diffuse reflectance spectra confirm that these compounds are semiconductors with a narrow band gap. All compounds show semiconducting properties; the Seebeck coefficient of Pb4In2.5Bi3.5Se13 is -180 mu V/K at 295 K.
Ternary Chalcogenides GeSb2Se3 and Ge3Sb4Se7 Containing a (1)(infinity)[Sb2Se2](2-) 1D Chain and a 2D Structure Related to SnSe
(2020-08-17)
Chen, Guan-Ruei
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Li, Chien-He
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Yu, Ching-Yi
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Wang, Ming-Fang
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Lee, Chi-Shen
Ternary chalcogenides, GeSb2Se3 and Ge3Sb4Se7, were synthesized and characterized. These chalcogenides are the first ternary selenides in a ternary Ge-Sb-Se system that feature a layer structure related to black phosphorus and SnSe-type structures. Both compounds contain a(infinity)( 1)[Sb2Se2](2-) unit with Sb+ cations in a zigzag Sb-Sb chain structure, and Sb3+ cations in a distorted NaCl100-type of (1)(infinity)[Gen-2Sb2Sen](2+) unit (n = 4, 5). These materials exhibit n-type semiconducting properties with thermal conductivity significantly lower than that of GeSe and Sb2Se3, which could be correlated to the 1D Sb+ chain and disordered sites with different Ge/Sb compositions. It is anticipated that these newly discovered ternary chalcogenides may provide unique properties with enhanced thermoelectric properties.