Browsing by Author "Huang, Wen-Heng"

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Structural variations in the ternary system HfAl(2-x)Cu(x) (x=0.2-1.0)
(2011-12-01)
Huang, Wen-Heng
;
Lee, Chi-Shen
;
應用化學系
;
Department of Applied Chemistry
Synthesized ternary intermetallic phases HfAl(2-x)Cu(x) in a series with (x = 0.49, 0.88, 1.04) are characterized as Laves phase structures. X-ray diffraction revealed homogeneity within ranges 0.2 <= x <= 0.5 and 0.7 <= x <= 0.9 for structure types MgCu(2) and MgNi(2), respectively. When Cu atoms gradually replaced the Al atoms, the structure type altered in the sequence MgCu(2) -> MgNi(2) -> MgZn(2), and the Kagome nets were distorted with varied bond lengths. Measurements of physical properties revealed these phases to be metallic, with resistances 4.35 (x = 0.5), 5.85 (x = 0.7), and 6.50 (x = 0.9) m Omega cm, respectively, at temperature 300 K. The coloring schemes reveal that, upon increasing the proportion of Cu atoms, the stability of these phases correlated with the arrangements of the Al and Cu atoms. Calculated electronic structures indicate that the bonding character is consistent with the experimentally observed phase width. (C) 2011 Elsevier Ltd. All rights reserved.
Structural variations in the ternary system HfAl2-xCux (x=0.2-1.0)
(2011-12-01)
Huang, Wen-Heng
;
Lee, Chi-Shen
;
應用化學系
;
Department of Applied Chemistry
Synthesized ternary intermetallic phases HfAl2-xCux in a series with (x = 0.49, 0.88, 1.04) are characterized as Laves phase structures. X-ray diffraction revealed homogeneity within ranges 0.2 <= x <= 0.5 and 0.7 <= x <= 0.9 for structure types MgCu2 and MgNi2, respectively. When Cu atoms gradually replaced the Al atoms, the structure type altered in the sequence MgCu2 -> MgNi2 -> MgZn2, and the Kagome nets were distorted with varied bond lengths. Measurements of physical properties revealed these phases to be metallic, with resistances 4.35 (x = 0.5), 5.85 (x = 0.7), and 6.50 (x = 0.9) m Omega cm, respectively, at temperature 300 K. The coloring schemes reveal that, upon increasing the proportion of Cu atoms, the stability of these phases correlated with the arrangements of the Al and Cu atoms. Calculated electronic structures indicate that the bonding character is consistent with the experimentally observed phase width. (C) 2011 Elsevier Ltd. All rights reserved.
Syntheses, Crystal Structures, Resistivities and Electronic Structures of Hf5Al3-xSbx (x=0.70, 1.44, 2.14)
(2013-07-01)
Huang, Wen-Heng
;
Chung, Ming-Yan
;
Lee, Chi-Shen
;
應用化學系
;
Department of Applied Chemistry
Three new hafnium aluminum antimonides Hf5Al3-xSbx (x = 0.70, 1.44, 2.14) were synthesized from pure elements in an arc-melting reaction; structures were solved from the X-ray diffraction data of single crystals. Al and Sb mixing produced two homogeneity ranges; the Mn5Si3 structural type was homogeneous for 0 x 1.0, and the W5Si3 structure covered the range 2.0 x 2.5. Both structures are condensations of two polyhedrons stacked along the c-axis. Calculations of the electronic structures revealed substantial contributions from Hf-Sb interactions; heteroatomic bonding in Hf-Al and Hf-Sb contacts affected the stabilities of these two phases. Measurements of the resistivity of polycrystalline samples revealed a dependence on temperature, indicating metallic behavior, consistent with the results of our calculations.
Ternary intermetallics Hf(13.0)Ni(40.8)Ga(30.9) and Zr(13.0)Ni(40.6)Ga(31.0)
(2011-11-01)
Huang, Wen-Heng
;
Lee, Chi-Shen
;
應用化學系
;
Department of Applied Chemistry
Ternary compounds Hf(13).(0)Ni(40.8)Ga(30.9) and Zr(13.0)Ni(40.6)Ga(31.0) were synthesized from the pure elements in arc-melting reactions; their structures were characterized through X-ray diffraction of single crystals. Each compound adopts a hexagonal structure of type Y(13)Pd(40)Sn(31) and crystallizes in space group P6/mmm (No. 191). The cell parameters of Hf(13.0)Ni(40.8)Ga(30.9) are a = 17.895(3)angstrom; c = 8.2434(16)angstrom; V=2286.0(6) angstrom(3); R(1)/wR(2)= 0.0299/0.0598. The cell parameters of Zr(13.0)Ni(40.6)Ga(31.0) are a= 17.964(3) angstrom; c = 8.2757(17) angstrom; V= 2312.7(7) angstrom(3); R(1)/wR(2) = 0.0348/0.0686. These structures comprise polyhedra with diverse coordination numbers - Hf 12-15, Ni and Ga 6-12. Analysis of the structures reveals layer frameworks based on structures of type CaCus, accompanied with atomic substitution and elimination on the layers and decreased values of the concentration of valence electrons. Calculated electronic structures reveal a strong contribution from a Ni-Ga interaction and the characteristics of a polar interrnetallic phase. (C) 2011 Elsevier Ltd. All rights reserved.
Ternary intermetallics Hf13.0Ni40.8Ga30.9 and Zr13.0Ni40.6Ga31.0
(2011-11-01)
Huang, Wen-Heng
;
Lee, Chi-Shen
;
應用化學系
;
Department of Applied Chemistry
Ternary compounds Hf-13.0Ni40.8Ga30.9 and Zr13.0Ni40.6Ga31.0 were synthesized from the pure elements in arc-melting reactions; their structures were characterized through X-ray diffraction of single crystals. Each compound adopts a hexagonal structure of type Y13Pd40Sn31 and crystallizes in space group P6/mmm (No. 191). The cell parameters of Hf13.0Ni40.8Ga30.9 are a = 17.895(3)angstrom; c = 8.2434(16)angstrom; V=2286.0(6) angstrom(3); R-1/wR(2)= 0.0299/0.0598. The cell parameters of Zr13.0Ni40.6Ga31.0 are a= 17.964(3) angstrom; c = 8.2757(17) angstrom; V= 2312.7(7) angstrom(3); R-1/wR(2) = 0.0348/0.0686. These structures comprise polyhedra with diverse coordination numbers - Hf 12-15, Ni and Ga 6-12. Analysis of the structures reveals layer frameworks based on structures of type CaCus, accompanied with atomic substitution and elimination on the layers and decreased values of the concentration of valence electrons. Calculated electronic structures reveal a strong contribution from a Ni-Ga interaction and the characteristics of a polar interrnetallic phase. (C) 2011 Elsevier Ltd. All rights reserved.