Browsing by Author "Cheng, Syh-Yuh"

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Effects of microwave heating on dielectric and piezoelectric properties of PZT ceramic tapes
(2008-04-01)
Chen, Yun-Tien
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Sheu, Ching-Iuan
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Lin, Shih-Chin
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Cheng, Syh-Yuh
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交大名義發表
Commercial lead zirconate titanate (PZT) perovskite powders were used to fabricate ceramic tape and then sintered by microwave and conventional methods. Both dielectric and piezoelectric properties of PZT ceramic tapes were studied in terms of sintering process. X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) show the PZT perovskite phase with smaller grain size and dense microstructure can be obtained at a lower sintering temperature by microwave process. It was also observed that shrinkage ratio and bulk density of the tapes sintered at 800 degrees C were obtained about 19% and 7.46 g/cm(3) by the microwave heating method, respectively, that is corresponding to those values of sintered PZT tapes at 950 degrees C by conventional process. Moreover, the dielectric constant and maximum permittivity are increased about 30% as compared with conventional processing method. The experimental results demonstrated that the characteristics of the PZT tapes could be significantly improved by microwave heating method. These results demonstrate that such a simple approach can upswing the piezoelectric and dielectric properties of these tapes by using microwave process with a short heating time. (C) 2007 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Electrochemical fabrication and magnetic properties of highly ordered silver-nickel core-shell nanowires
(2008-01-31)
Lin, Shih-Chin
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Chen, San-Yuan
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Chen, Yun-Tien
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Cheng, Syh-Yuh
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交大名義發表
Ordered silver-nickel core-shell nanowire arrays were successfully fabricated by electrodeposition. The ordered silver nanowire arrays embedded in a porous alumina template were first fabricated from an aqueous solution of Ag(NO3)(2) and Ac(NH3). After removing out the template, the obtained silver nanowire arrays were subsequently electrodeposited with nickel at 1.6-2.6 V and 60 degrees C using the electrolyte composed of NiSO4, NiCl2 and H3BO3. Transmission electron microscopy observation revealed that a similar to 15 nm thick nickel film was coated on the surface of the silver nanowires with about 200 nm in diameter. It was found that the silver nanowires with nickel coating showed enhanced magnetic properties in comparison to that of pure silver nanowires. The magnetic force microscope image of silver-nickel core-shell nanowires showed magnetic domain state. In addition, the hysteresis loops of the silver-nickel nanowire arrays showed a coercive field of 180 Oe, almost independent of the applied magnetic field. However, it was observed that a larger magnetic domain was found in parallel direction than that in perpendicular direction. (c) 2007 Elsevier B.V. All rights reserved.
Fabrication and Characterization of Mg-Doped ZnO Nanorod Arrays
(2010-07-01)
Liao, Hung-Chou
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Chen, San-Yuan
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Peng, Cheng-Hsiung
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Lin, Chin-Ching
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Cheng, Syh-Yuh
Photoelectronic characteristics are investigated in well-aligned MgO-coated ZnO nanorods (MgO/ZnO nanocables) grown on Si substrates buffered with ZnO film at a low temperature by solution techniques. Transmission electron microscopy shows that a rough surface was observed for the MgO-coated ZnO nanorods due to deposition of MgO nanoparticles on the surface of the ZnO nanorods. However, after annealed at high temperatures, the surface of the MgO-coated ZnO nanorods was flattened to form Mg-doped ZnO nanorods. Photoluminescence spectra of Mg-doped ZnO nanorods displayed a blue shift of the near-band-edge emission with increasing annealing temperature indicative of an increase in the band gap of the MgZnO alloy due to diffusion of the Mg atoms into the ZnO nanorods. In contrast, no blue shift was detected for the samples annealed in H(2)/N(2) (5%/95%) reduction atmosphere but a blue emission was detected at 800 degrees C, indicating that MgO diffusion process may produce a new luminescent center to emit the blue emission in H(2)/N(2) reduction atmosphere.
High electron injection structure in hybrid solar cells
(2008)
Liao, Hung-Chou
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Chen, San-Yuan
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Lin, Chin-Ching
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Cheng, Syh-Yuh
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材料科學與工程學系
We evaluate an ordered organic-inorganic solar cell architecture based on CdS QD-decorated ZnO nanorod arrays encased in the hole-conducting polymer Poly(3-hexylthiophene-2,5-diyl) (P3HT). In this work, CdS quantum dot with different sizes were attached to the surface of the nanorods capped with mercaptopropionic acid. The results show that the CdS QDs on the ZnO nanorods increase both the open circuit voltage (V(OC)) and short circuit current density (J(SC)) relative to devices without CdS QDs. A photovoltaic device based that has been decorated with CdS QDs yields power conversion efficiency over 4 times greater than that for a similar device without CdS QDs. The best device yields a short circuit current density of 1.38 mAcm(-2) under AM1.5 illumination (100 MW cm(-2)), resulting in a power conversion efficiency of 0.21% The increase shows that the modification with CdS QDs can serve not only as a photosensitizer but mainly as an energy funnel and/or an electronic mediator to significantly improve the electron injection efficiency from P3HT to ZnO nanorods.
RETRACTION: Nucleation and growth behavior of well-aligned ZnO nanorods onorganic substrates in aqueous solutions (Retraction of Vol 283, Pg 141, 2005)
(2018-12-15)
Lin, Chin-Ching
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Chen, San-Yuan
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Cheng, Syh-Yuh
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材料科學與工程學系
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Department of Materials Science and Engineering
Role of Metall-Organic Precursor-doped Silver Paste in Low Temperature Co-Fired Ceramics
(2000)
Chou, Ching-Huan
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Chen, San-Yuan
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Cheng, Syh-Yuh
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材料科學與工程學系
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Department of Materials Science and Engineering
In this study, a variety of metall-organic precursors were used to compare its effect on sintering densification of Ag-based paste. It was found that the thermal shrinkage of silver-based paste was strongly influenced by powder characteristics, solid loading and compositions. Furthermore, we found that the addition of metall-organic precursor, especially Zr-based organic precursor, in silver-paste is more useful to inhibit the sintering of silver particles and further reduce shrinkage mismatch between silver-based paste and dielectrics. The microstructure evolution of silver-paste/dielectrics is also discussed.
Synthesis and luminescent properties of strong blue light-emitting Al2O3/ZnO nanocables
(2008)
Hsiao, Chi-Sheng
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Kuo, Wan-Lin
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Chen, San-Yuan
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Shen, Ji-Lin
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Lin, Chin-Ching
Photoelectronic characteristics are investigated in well-aligned aluminum-coated ZnO nanorods (Al2O3/ZnO nanocables) grown on Si substrates buffered with ZnO film at a low temperature. Photoluminescence measurement indicates that a strong blue emission peak at similar to 450 nm appears at 400 and 600 degrees C in O-2 and N-2 atmospheres, respectively. A 30x enhancement of the relative intensity ratio of blue emission (I-B) to ultraviolet emission (I-UV) has been observed for the Al2O3/ZnO nanocables. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analyses reveal that the origin of the strong blue emission can be attributed to the structure transition and cleavage of the oxygen-hydrogen bond (OH) of the Al2O3/ZnO nanocable, which leads to the formation of singly ionized oxygen vacancies (Al-O-center dot). (C) 2008 The Electrochemical Society.
Synthesis and optical properties of white-light-emitting alumina/ZnO nanotubes
(2008-10-08)
Hsiao, Chi-Sheng
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Chen, San-Yuan
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Kuo, Wan-Lin
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Lin, Chin-Ching
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Cheng, Syh-Yuh
A simple chemical solution process was used to prepare alumina nanoparticle-coated ZnO nanotubes (ANZTs). Transmission electron microscope (TEM) images proved that the alumina nanoparticles were uniformly dispersed on the ZnO nanotubes. After thermal treatment at different temperatures under various atmospheres, photoluminescence (PL) measurements showed that the ANZTs emitted a variety of colors, including blue, green and white light. Gaussian curve fitting of the PL spectra revealed that the competition between the blue, blue-green, green and yellow band emissions and their relative emission intensities were strongly associated with various defects. Blue emission was attributed to large numbers of oxygen defects in alumina, while green and yellow emissions were related to oxygen and zinc defects in ZnO, respectively. Under specific conditions, white light, consisting of blue, blue-green, green and yellow band emissions, was obtained. Further TEM analysis indicated that the defect structure of ANZTs could be manipulated by the interface interaction between alumina and the ZnO nanotubes.
Synthesis and physical characteristics of AlOx-coated ZnO nanorod arrays grown in aqueous solution at low temperatures
(2008-02-01)
Hsiao, Chi-Sheng
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Chen, San-Yuan
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Cheng, Syh-Yuh
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材料科學與工程學系
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Department of Materials Science and Engineering
AlOx-ZnO core-shell nanorods arrays have been successfully synthesized by soaking the ZnO nanorods in the sol-gel solution of Al(NO3)(3) and NH4OH at room temperature. It was found that both crystal growth and morphology of the AlOx-ZnO core-shell nanorods are strongly influenced by the solution pH value. SEM image shows that the AlOx-ZnO core-shell nanorods can be perpendicularly grown on the ZnOf/Si substrate under the solution only with a pH value of 6-7. High-resolution TEM observation demonstrates that the structure of the AlOx layer is amorphous and the ZnO nanorod core remains single crystal. After annealed at 400 degrees C in N-2 atmosphere, a strong photoluminescence peak corresponding to blue emission (similar to 450 nm) was detected from the AlOx-ZnO core-shell nanorods that may result from the induced defects due to interaction between AlOx shell and ZnO nanorods. (C) 2007 Elsevier Ltd. All rights reserved.