共查询到20条相似文献,搜索用时 9 毫秒
1.
William Nimmo Naseef J. Ali Rik M. Brydson Clair Calvert Edward Hampartsoumian David Hind Steven J. Milne 《Journal of the American Ceramic Society》2003,86(9):1474-1480
Twin-fluid atomization spray pyrolysis (SP) has been investigated for the production of lead zirconate titanate (PZT) powders, using aqueous solutions of lead acetate and zirconium and titanium alkoxide precursor reagents. The particle size distribution of the PZT powder showed a d 50 value of 0.3 μm, but with a small fraction of relatively large particles, several micrometers in size. Most particles were spherical but many of the largest particles, in the size range ca. 1–5 μm, were irregular. It was demonstrated that the morphology of the final PZT powder was controlled by decomposition processes occurring during the initial drying stages, at ≤200°C. A pyrochlore or fluorite-type intermediate crystalline phase was present in the final powders, but when the maximum reactor temperature was raised, and/or when the levels of excess lead in the starting solutions were increased, the proportion of the desired perovskite phase increased. However, at the highest process temperatures studied, ∼900°C, small crystallites of another phase formed on the surface of the PZT particles; these were probably lead oxide carbonate particles. Overall, a starting solution composition containing around 5 mol% excess Pb, and a maximum reactor temperature of 800°C, were selected as offering the most suitable conditions for producing PZT (52/48) powder, with minimal secondary phases(s). Preliminary densification studies showed that the powders could be sintered at 1150°–1200°C to give pellets of 95%–96% theoretical density. 相似文献
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Crystallization of Fine, Chemically Prepared Lead Lanthanum Zirconate Titanate Powders at Low Temperature 总被引:1,自引:0,他引:1
Fine, homogeneous lead lanthanum zirconate titanate (PLZT) powder prepared by the hydrolysis of an aqueous nitrate solution with ammonia gas exhibits high reactivity when calcined. The minimum temperature for crystal formation in PLZT is 400°C. The kinetics of crystallization between 400° and 600°C are studied isothermally by XRD. The isothermal crystallization process is best fitted to a first-order equation derived for a random, nucleation-controlled system on a large number of small particles with an activation energy of 297 kJ/mol. Characterization of the powder by XRD line-broadening and BET surface-area examination in the range 400° to 500°C shows a microstructure consisting of ∼20-nm subunits agglomerated into ∼60-nm particles. Each subunit evidently generates a single nucleus, which grows within that subunit. 相似文献
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热水溶液中钛酸锶晶粒的结晶过程 总被引:6,自引:0,他引:6
研究了以TiCl4水解得到的H4TiO4胶体作为钛源,在热水溶液中制备SrTiO3晶粒的结晶过程,TEM和XRD结果表明,其结晶过程主要包括3个阶段,第1阶段主要是SrTiO3晶核的形成过程;第2阶段主要是SrTiO3晶粒的配向聚集生长过程;第3阶段主要是SrTiO3晶粒的溶解结晶过程,其中第1阶段的控制步骤为H4TiO4胶体的溶解,第2阶段中晶粒的配向聚集生长在短时间内即可完成,很快进入第3阶段小晶粒的溶解和大晶粒的重结晶过程,该阶段反应速度慢,需要较长时间才能得到结晶完好的晶粒,在热水溶液中以H4TiO4胶体作为钛源制备SrTiO3晶粒关键在于控制结晶过程的第1阶段和第2阶段。 相似文献
4.
Edson R. Leite Elaine C. Paris Elson Longo Francesco Lanciotti Jr. Carlos E. M. Campos Paulo S. Pizani Valmor Mastellaro Carlos A. Paskocimas Jose Arana Varela 《Journal of the American Ceramic Society》2002,85(9):2166-2170
The crystallization process of lead titanate (PT) prepared using the polymeric precursor method was investigated using X-ray diffractometry, Raman spectroscopy, electron microscopy, and X-ray absorption spectroscopy techniques. The results showed that amorphous PT was formed by an O–Ti–O structure composed of fivefold and sixfold oxygen-coordinated titanium. The local structure of the amorphous PT phase was similar to that of the cubic PT phase, i.e., similar coordination number and similar bond lengths, leading to a topotactic-like transformation during the phase transformation from amorphous to cubic perovskite PT. Because of the low crystallization temperature, every transformation observed during the crystallization process was associated with a short-range rearrangement process. 相似文献
5.
以FeC l3.6H2O和B i(NO3)3.5H2O为原料,氨水为沉淀剂,KOH为矿化剂,采用共沉淀法制备前驱物,水热法合成了纯相的B iFeO3粉体。X射线衍射结果表明,在160℃,碱浓度仅为0.15 mol/L的水热条件下,即可合成纯相的B iFeO3粉体。该工艺大大降低了水热温度,减小了碱浓度,从而节约了能源,降低了成本,减轻了碱对水热设备的腐蚀。扫描电镜显示,前驱沉淀物陈化时间为1 d时,水热制备的B iFeO3粉体中有发育良好的六方短柱状晶体形成;陈化时间增加到3 d时,所得B iFeO3粉体呈双层板状。差热-失重分析表明,所得B iFeO3粉体的尼尔温度(TN)为301℃,居里温度(TC)为828℃,分解温度为964℃。 相似文献
6.
Bongsoo Kim Seungbum Hong Gun Ahn Kwangsoo No 《Journal of the American Ceramic Society》2016,99(7):2221-2225
Here, we demonstrate a novel process to convert TiO2 nanotubes into ferroelectric nanohoneycombs, comprised of vertically aligned PbTiO3 nanotubes. Tube bottom opening process enabled effective infiltration of lead acetate precursor into the nanotubes. Nanohoneycombs, which were converted via additional lead supplement process, showed uniform conversion and well‐defined ferroelectric properties with the effective piezoelectric coefficient of approximately 20 pm/V, which was measured by piezoresponse force microscopy. 相似文献
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钡钛醋酸盐凝胶制备BaTiO3粉体 总被引:2,自引:1,他引:2
本文报道了用sol-gel法制备钡醋酸盐凝胶,并分别作高灼烧和水热处理制备BaTiO3粉体。通过对产物的表征,比较了这两种处理过程,进而对水热条件下陶瓷粉体的形成机理作了探讨。由于水热条件,凝胶在反应介质中溶解,进而结晶形成晶粒,因此所形成的BaTiO3晶粒线度小;线度分布范围窄。晶粒形貌完整,明显优于高温灼烧处理后得到的粉体。 相似文献
8.
E. R. Leite E. C. Paris E. Longo J. A Varela 《Journal of the American Ceramic Society》2000,83(6):1539-1541
The phase evolution of lead titanate processed by the polymeric precursor method was investigated by thermal analysis, X-ray diffraction, and high-resolution transmission electron microscopy. The results showed that the cubic perovskite PbTiO3 (PT) phase is formed from an inorganic amorphous precursor at a temperature of 444°C. A gradual transition from cubic to tetragonal perovskite PT was observed with the increase of calcination time at this temperature. HRTEM results showed that the cubic PT particles have a size of around 5 nm. The identification of cubic PT as an intermediate phase supports the hypothesis that the chemical homogeneity was kept at the molecular level during the synthesis process, with no cation segregation. 相似文献
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Preparation of Tetragonal Barium Titanate Thin Film on Titanium Metal Substrate by Hydrothermal Method 总被引:2,自引:0,他引:2
Koji Kajiyoshi Nobuo Ishizawa Masahiro Yoshimura 《Journal of the American Ceramic Society》1991,74(2):369-374
Tetragonal BaTiO3 thin films were prepared directly on Ti metal substrates in Ba(OH)2 solutions by a hydrothermal method at temperatures 400° to 800°C for 5 to 240 min. The film thickness estimated from weight gain of Ti plate was in the range from 0.5 to 2.5 μm, and it increased with increasing treatment temperature, treatment time, and Ba(OH)2 concentration. Rectangular crystals having {100} and {001} faces grew idiomorphically with approximate crystal size of 0.3 to 2.0 μm. The tetragonality of the BaTiO3 films became apparent when the average crystal size exceeded about 1 μm. Lattice parameters of the films were a = 3.994 Å, c = 4.035 Å, and c/a = 1.010. The films formed above 600°C had preferred orientation showing stronger XRD peaks of h 00 and 00 l than the other peaks. 相似文献
10.
Hydrothermal Preparation of Calcium Hydroxyapatite Powders 总被引:11,自引:0,他引:11
Calcium hydroxyapatite powders were prepared by hydrothermal reactions of calcium pyrophosphate and calcium oxide. Primary particles of the hydroxyapatite obtained were spherical with diameters less than 0.2 μm, and small prismatic crystals were rarely observed in some fields. The effects of temperature, pressure, and soaking time on the structural features of the resultant powders were also studied by means of XRD and SEM and were smaller than expected for the ranges investigated. 相似文献
11.
Ping-Hua Xiang Xian-Lin Dong Chu-De Feng Yong-Ling Wang 《Journal of the American Ceramic Society》2003,86(9):1631-1634
NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO3 )2 ·6H2 O, and NH4 HCO3 as the starting materials. The amorphous NiCO3 ·2Ni(OH)2 ·2H2 O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ∼8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ∼30 nm. 相似文献
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Aiying Wu Paula M. Vilarinho Isabel M. Miranda Salvado João L. Baptista 《Journal of the American Ceramic Society》2000,83(6):1379-1385
Lead zirconate titanate (PZT) (52/48) powders were prepared by a sol–gel process, using different raw materials to introduce the lead component together with several solvents and chemical modifying agents. A study of the effect of these variables on crystallization behavior was conducted to determine the best conditions for preparing monophasic submicrometer-sized PZT perovskite powders in the morphotropic region. In the present work, well-crystallized, submicrometer-sized single-phase perovskite PZT powders were obtained after heat treatment at 600°C for 1 h. The dependence of this crystallization temperature on the preparation conditions was observed. The sol–gel-derived submicrometer-sized PZT powders were sintered to ∼96% of relative density after 2 h at 950°–970°C. The sintered ceramics exhibited a dielectric permittivity of 1000, a piezoelectric coefficient of 135 pC·N−1 , a remanent polarization of 20 μC·cm−2 , and a coercive field of 10.6 kV·cm−1 . 相似文献
14.
San-Yuan Chen Syh-Yuh Cheng Chien-Min Wang 《Journal of the American Ceramic Society》1990,73(2):232-236
The polymorphic phase transformation of PbO from massicot to litharge phase is easily produced by mechanical force. The transformation is relatively quick by wet ball-milling. The additions of TiO2 and ZrO2 tend to retard it. A second-order exponential relation is observed between the fractional conversion and the milling time for pure PbO, PbO-TiO2 , and PbO-ZrO2 -TiO2 systems with a rutile constituent. This exponential relation is changed into a first-order logarithmic relation when anatase instead of rutile is used. Although the PbO ss phase is observed irrespective of the phase of the PbO in the raw materials, this PbO ss peak is more obvious when massicot PbO or anatase TiO2 is used. The formation of PbO ss phase is also dependent on the reactivity of the ZrO2 , and its presence can affect the formation and piezoelectric properties of PZT ceramics. 相似文献
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Huiwen Xu Keith J. Bowman Elliott B. Slamovich 《Journal of the American Ceramic Society》2003,86(10):1815-1817
Bismuth titanate was synthesized under hydrothermal conditions from an amorphous bismuth–titanium precursor gel. The gel was formed by mixing a bismuth acetate complex with titanium butoxide and then adding the solution dropwise into 6 M NaOH. The resulting gel suspension was reacted under hydrothermal conditions at temperatures ranging from 160° to 200°C to form crystalline bismuth titanate. The gel crystallization kinetics increased with temperature, which resulted in 100% crystalline bismuth titanate in 5 h at 200°C. Wavelength-dispersive spectroscopy data indicated that sodium was incorporated into bismuth titanate during processing, and X-ray diffractometry suggested that the powder was composed of the Bi5 Ti4 O15 phase. Transmission electron microscopy micrographs showed that the gel particles decomposed to 100–200 nm crystalline bismuth titanate particles during hydrothermal processing. 相似文献
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Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms 总被引:5,自引:0,他引:5
Balasubramaniam Vaidhyanathan Anirudh P. Singh Dinesh K. Agrawal Thomas R. Shrout Rustum Roy Suman Ganguly 《Journal of the American Ceramic Society》2001,84(6):1197-1202
A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O3 (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss. 相似文献