Papers by Author: Hui Qing Fan

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Authors: Jie Zhang, Hui Qing Fan, Sha Ming Ke, Yun Ze Shi, Xian Hua Zeng, Mei Tian Bi, Hai Tao Huang
Abstract: The fabrication processing, dielectric properties and thermal properties of polymer-matrix composites containing AlN particles (10μm) for electronic substrates and microelectronic packaging applications were investigated. The epoxy resin (E-51) is used as the matrix, and the dispersion of the AlN in the composites is varied form 0 vol% to 40 vol%. The microstructures of the polymer-matrix composites are observed through scanning electron microscopy (SEM). With increasing the AlN content, thermal conducting of composites is improved, while the composites still keep the relatively low dielectric constant and dielectric loss. According to the dielectric properties dependence on frequencies (1kHz-10MHz) of the composites, the Cole-Cole plot is analyzed. The dipole relaxation in the composite is induced, and it is suggested that the air layer exit between the epoxy resin and the AlN particles.
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Authors: Pin Yang Fang, Hui Qing Fan, Shao Jun Qiu, Lai Jun Liu, Jin Chen
Abstract: Lanthanum-modified bismuth titanate, Bi3.25La0.75Ti3O12 (BLT), powders were prepared from polymerized precursors using citric acid as a chelating agent and ethylene glycol as an esterification agent. The effect of calcination temperature on the microstructure and morphology of powders were studied. It was shown that the pure and normally stoichiometric phase of BLT powders could be obtained at relative low temperature from 550o to 700oC even if the bismuth content is not excess in the starting precursors while the secondary phase could be detected at both lower and higher calcination temperatures. The shape of the BLT grains is also strongly influenced by the calcination temperature.
1555
Authors: Hui Qing Fan, Lai Jun Liu, Xiu Li Chen, Jie Zhang, Wei Wang
Abstract: Barium modified lead zirconate titanate (PBZT) thin films were grown epitaxially on Pt/Ti/SiO2/Si substrates by radio-frequency magnetron sputtering deposition and characterized by X-ray diffraction and scanning electron microscopy. Depending on the growth condition, a wide variation of crystal structure and morphology was evolved in PBZT thin films. The formation of phase structure and pyrochlore phase was strongly dependent on the oxygen partial pressure and re-evaporation of lead from the films during the deposition. Perovskite films were obtained by optimizing the deposition conditions and analyzed by the ferroelectric hysteresis (P~E).
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Authors: Hui Qing Fan
Abstract: Relaxor-based piezoelectric single crystals of lead indium niobate-lead titanate (0.63Pb(In1/2Nb1/2)-0.37PbTiO3, abbreviated as PIN-PT), in the vicinity of the morphotropic phase boundary, were prepared by a flux method. The compositions of the flux, Pb3O4 or PbF2, play different role in perovskite stability and phase development. Thus, pure perovskite PIN-PT single crystals with the size of 2~5 mm were obtained by using Pb3O4 flux as well as a small amount of B2O3 additive. The microstructure and the phase development of the as-grown single crystals were investigated by scanning electron microscopy and transmission electron microscopy and X-ray diffraction. Furthermore, the dielectric properties of the <100>-oriented PIN-PT single crystals were measured in the temperature range between 20°C and 400°C.
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Authors: Xiu Li Chen, Hui Qing Fan
Abstract: Relaxor ferroelectric Pb(Mg1/3Nb2/3)O3 (PMN) crystals were grown at low temperature by a single-step hydrothermal process, using the mixture of PbO, MgO and Nb2O5 as precursors. The precursors were just heated to 150 oC for 24 h. The effect of the KOH concentration on the morphology and microstructure of PMN crystals was systematically investigated. The optimum KOH concentration was found to be 11M, which led to the stabilization of the perovskite crystals against the pyrochlore phase, and to the growth of high-quality PMN crystals suitable for subsequent characterization. According to morphological evolution during the reaction, two possible growth mechanisms are proposed. When the KOH concentration is 11M, at the early stage of the reaction, the starting materials dissolve, and then promote the formation of spherical intermediate pyrochlore phase followed by the formation of primary cubic PMN crystals. At the same time, a platelet-shaped intermediate pyrochlore phase also forms and then grows into larger platelet-shaped PMN crystals.
2059
Authors: Hui Qing Fan
Abstract: Relaxor-based 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films were grown epitaxially on silicon substrates by sol-gel method and PbO cover coat technique, and investigated by x-ray diffraction, auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The phase development and microstrure evolution of the PMN-PT film were significantly affected by the final annealing temperature and time. A perovskite PMN-PT film was obtained after annealing at 850oC for 1 min. Then, highly <100>-oriented and textured PMN-PT films could be achieved by using a LaNiO3 perovskite template.
839
Authors: Zi Min Fan, Hui Qing Fan, Xiao Gang Wang
Abstract: A SiC ceramic coating for high temperature and anti-oxidation was prepared by high temperature reaction and PVD methods inside industrial synthetic furnace of SiC. Its phase composition and microstructure were characterized by using XRD, SEM,and its high temperature anti-oxidation property were studied by isothermal oxidation tests.The results showed that the coating is composed of mainly α-SiC and β-SiC,the coating is uniform, compact, perfect grain growth, without crack, closely with the C/C materials,the thickness is about 600μm. After 10h oxidation in air at 1773 k the weight loss of the coating was only 0.3%,which implies that the coating has excellent anti-oxidation ability.
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Authors: Yun Fei Fu, Pei Feng Zhang, Hui Qing Fan, Xiu Li Chen
Abstract: Ba0.6Sr0.4TiO3 nanopowders (~ 80 nm in size) were prepared by low temperature hydrothermal process. The process and synthesis mechanism were discussed in detail. Furthermore, the powders were pressed into disc-shaped pellets and sintered at different temperatures. The frequency dependence of the dielectric constant and loss angle tangent of the sintered BST ceramics are measured from room temperature to 500°C and a diffuse dielectric anomaly by the dielectric relaxation was found.
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Authors: Lai Jun Liu, Hui Qing Fan
Abstract: The effect of stoichiometry, i.e. Ca/Cu ratios (CaCu3xTi4O12, x = 0.8, 0.9, 1.0, 1.1 and 1.2) on the microstructure and electrical properties was investigated. The grain sizes of CaCu3xTi4O12 composition increased sharply with the increase of copper, from ~1 μm with x = 0.8 to ~50 μm with x = 1.2. The real part of dielectric permittivity changed dramatically, the pellet with x = 1.0 had the highest dielectric permittivity ~160, 000 at 1 kHz. Furthermore, the dielectric permittivity of all pellets was impressively large values (between 10, 000 to 1, 000,000 at 100 Hz) and was nearly constant over a wide frequency range between 100 Hz to ~100 MHz. However, the dielectric permittivity of CaCu3xTi4O12 composition is not consistent with the amount of copper and cell parameters and grain sizes. Impedance spectroscopy exhibited that the CaCu3xTi4O12 composition had two semicircle at least at high frequency (~ 107 Hz) and low frequency (<100 Hz), respectively. The grain and grain boundary of the compositions had different impedance and relaxation behavior.
551
Authors: Shao Jun Qiu, Hui Qing Fan, Xiao Dong Zheng, Jin Chen, Chen Yang, Pin Yang Fang
Abstract: To adjust the morphology and crystallinity of the chemically prepared Zr-riched` lead zirconate titanate (Pb(Zr0.95Ti0.05)O3) powders, polyethylene glycol (PEG 20000) was used in aqueous solution (modified Pechini method). Thermal analysis of the as-synthesized gel showed two distinct stages, which indicates the volatilization of water and the decomposition of polymers, respectively. When the gel were calcined at 400 oC, the powders consisted mainly of perovskite PZT accompanied with small amounts of secondary phases. The higher the calcination temperature applied, the stronger the intensity of XRD, which means the crystallinity were improved. Scanning electron microscopy of as-prepared powders suggested that the powders were soft agglomerate particles when calcined at 600 to 800 oC. Compared with the normal Pechini method, PEG could help the formation of crystalline phase and soft agglomerate. When the powders compacts were sintered at 975 to 1125 oC, high pure (>99.5%) of tetragonal phase ceramics were got having relative density of 85% to 94%.
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