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1.
LiNi0.5Co0.5VO4 nano-crystals were solvothermally prepared using a mixture of LiOH·H2O, Ni(NO3)2·6H2O, Co(NO3)2·6H2O and NH4VO3 in isopropanol at 150–200 °C followed by 300–600 °C calcination to form powders. TGA curves of the solvothermal products show weight losses due to evaporation and decomposition processes. The purified products seem to form at 500 °C and above. The products analyzed by XRD, selected area electron diffraction (SAED), energy dispersive X-ray (EDX) and atomic absorption spectrophotometer (AAS) correspond to LiNi0.5Co0.5VO4. V–O stretching vibrations of VO4 tetrahedrons analyzed using FTIR and Raman spectrometer are in the range of 620–900 cm−1. A solvothermal reaction at 150 °C for 10 h followed by calcination at 600 °C for 6 h yields crystals with lattice parameter of 0.8252 ± 0.0008 nm. Transmission electron microscope (TEM) images clearly show that the solvothermal temperatures play a more important role in the size formation than the reaction times. 相似文献
2.
Tian He Jinhui DaiJintao Tian Zhibin ZhuLiangzhai Guo Zhongfang LiuXiaofei Qu Zhenlei ShenPeipei Wang 《Ceramics International》2008
The Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 powder synthesis through molten salt method was investigated in the temperature range of 650–700 °C for 2–4 h. The XRD results indicated that the optimal synthesizing temperature for molten salt method was 700 °C, significantly lower than that for conventional processing route of solid state reaction method, where a calcining temperature of 850 °C was needed. The SEM results revealed better crystallization of the powders obtained through molten salt method, compared with those through the conventional processing route of solid state reaction method. 相似文献
3.
Tao Chen Hongli Wang Ting Zhang Guangchang Wang Jifang Zhou Jianwei Zhang Yuhong Liu 《Ceramics International》2014
(Bi0.5Na0.5)0.94Ba0.06TiO3–xHfO2 [BNBT–xHfO2] lead-free ceramics were prepared using the conventional solid-state reaction method. Effects of HfO2 content on their microstructures and electrical properties were systematically studied. A pure perovskite phase was observed in all the ceramics with x=0–0.07 wt%. Adding optimum HfO2 content can induce dense microstructures and improve their piezoelectric properties, and a high depolarization temperature was also obtained. The ceramics with x=0.03 wt% possess optimum electrical properties (i.e., d33~168 pC/N, kp~32.1%, Qm~130, εr~715, tan δ~0.026, and Td~106 °C, showing that HfO2-modified BNBT ceramics are promising materials for piezoelectric applications. 相似文献
4.
High-voltage LiNi0.5Mn1.5O4 spinels were synthesized by a low temperature solution combustion method at 400 °C, 600 °C and 800 °C for 3 h. The phase composition, structural disordering, micro-morphologies and electrochemical properties of the products were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and constant current charge–discharge test. XRD analysis indicated that single phase LiNi0.5Mn1.5O4 powders with disordered Fd-3m structures were obtained by the method at 400 °C, 600 °C and 800 °C. The crystallinity increased with increasing preparation temperatures. XRD and FTIR data indicated that the degree of structural disordering in the product prepared at 800 °C was the largest and in the product prepared at 600 °C was the least. SEM investigation demonstrated that the particle size and the crystal perfection of the products were increased with increasing temperatures. The particles of the product prepared at 600 °C with ~200 nm in size are well developed and homogeneously distributed. Charge/discharge curves and cycling performance tests at different current density indicated that the product prepared at 600 °C had the largest specific capacity and the best cycling performance, due to its high purity, high crystallinity, small particle size as well as moderate amount of Mn3+ ions. 相似文献
5.
Ba0.7Sr0.3TiO3 (BST) ceramics prepared by a reaction-sintering process were investigated. BST ceramics could be obtained after 2–6 h sintering at 1330–1370 °C without any calcination involved. BST with density 5.68 g/cm3 (99.8% of the theoretic value) was obtained at 1350 °C for 6 h sintering. Grains of 2–15 μm were formed after 2–6 h sintering at 1330–1370 °C. A diffused ferroelectric–paraelectric transition was observed in pellets sintered at 1330 °C for 2 h and disappeared at a longer soak time or a higher sintering temperature. 相似文献
6.
(1 − x)Ba0.4Sr0.6TiO3/xCaCu3Ti4O12 composite ceramics were prepared by spark plasma sintering. Sintering behavior, microstructures and dielectric properties of the composite ceramics were investigated by XRD, SEM, EDS and dielectric spectrometer. Dense composite ceramics consisting of Ba0.4Sr0.6TiO3 phase and CaCu3Ti4O12 phase were prepared at 800 °C for 0 min. The dielectric loss of the composite ceramic decreased with increasing amount of Ba0.4Sr0.6TiO3, and the high dielectric constant were retained. Moreover, the better temperature stability of dielectric constant was obtained. These improvements of dielectric characteristics have great scientific significance for potential application. 相似文献
7.
Spherical (Ni0.5Mn0.5)(OH)2 with different secondary particle size (3 μm, 10 μm in diameter) was synthesized by co-precipitation method. Mixture of the prepared hydroxide and lithium hydroxide was calcined at 950 °C for 20 h in air. X-ray diffraction patterns revealed that the prepared material had a typical layered structure with space group. Spherical morphologies with mono-dispersed powders were observed by scanning electron microscopy. It was found that the layered Li[Ni0.5Mn0.5]O2 delivered an initial discharge capacity of 148 mAh g−1 (3.0-4.3 V) though the particle sizes were different. Li[Ni0.5Mn0.5]O2 having smaller particle size (3 μm) showed improved area specific impedance due to the reduced Li+ diffusion path, compared with that of Li[Ni0.5Mn0.5]O2 possessing larger particle size (10 μm). Although the Li[Ni0.5Mn0.5]O2 (3 μm) was electrochemically delithiated to Li0.39[Ni0.5Mn0.5]O2, the resulting exothermic onset temperature was around 295 °C, of which the value is significantly higher than that of highly delithiated Li1−δCoO2 (∼180 °C). 相似文献
8.
(1 − x)Ba0.6Sr0.4TiO3-xMgAl2O4(x = 25, 30, 35 and 40 wt%) composite ceramics were prepared by conventional solid-state reaction method. The microstructures, dielectric properties and tunability of the composites have been investigated. The XRD patterns analysis reveals two crystalline phases, a cubic perovskite structure Ba0.6Sr0.4TiO3 (BST) and a spinel structure MgAl2O4 (MA). SEM observations show that the BST grains slightly dwindle and agglomerate with increasing amounts of MA. A dielectric peak with very strong frequency dispersion is observed at higher MA content, and the Curie temperature shifts to a higher temperature with increasing MA content. The ceramic sample with 30 wt% MA has the optimized properties: the dielectric constant is 1503, the dielectric loss is 0.003 at 10 kHz and 25 °C, the tunability is 23.63% under a dc electric field of 1.0 kV/mm, which is suitable for ferroelectric phase shifter. 相似文献
9.
We investigated the effects of the Sm-dopant content and the cooling rate on the electrical properties and microstructure of Ba1.022−xSmxTiO3 (BST) ceramics, which were sintered at 1200 °C for 30 min in a reducing atmosphere and then reoxidized at 800 °C for 1 h. The results indicated that the cooling rate affected the electrical properties and the microstructure of the BST samples, whose room-temperature resistivity increased with increasing cooling rate. The semiconducting BST ceramics showed a pronounced positive temperature coefficient of resistivity effect, with a resistance jump greater by 3.16 orders of magnitude, along with a low room-temperature resistivity of 157.4 Ω cm at a cooling rate of 4 °C/min. The room-temperature resistivity of the specimen was lower after sintering for 30 min at 1150 °C during cooling. 相似文献
10.
This paper studies the preparation of UO2/TiO2 composite ceramic fuel through sol gel-press forming. The research shows that at 1200–1300 °C, UO2/TiO2 composite ceramic grains are small, uniform and compact. Among them, UO2–0.5 wt%TiO2 has the highest density and good mechanical strength at 1250 °C. 相似文献
11.
Xiaoning Guo Guojuan Zhi Xiaoyan Yan Guoqiang Jin Xiangyun Guo Pascal Brault 《Catalysis communications》2011,12(10):870-874
The performances of different promoters (CeO2, ZrO2 and Ce0.5Zr0.5O2 solid solution) modified Pd/SiC catalysts for methane combustion are studied. XRD and XPS results showed that Zr4+ could be incorporated into the CeO2 lattice to form Zr0.5Ce0.5O2 solid solution. The catalytic activities of Pd/CeO2/SiC and Pd/ZrO2/SiC are lower than that of Pd/Zr0.5Ce0.5O2/SiC. The Pd/Zr0.5Ce0.5O2/SiC catalyst can ignite the reaction at 240 °C and obtain a methane conversion of 100% at 340 °C, and keep 100% methane conversion after 10 reaction cycles. These results indicate that active metallic nanoparticles are well stabilized on the SiC surface while the promoters serve as oxygen reservoir and retain good redox properties. 相似文献
12.
A new compound of barium bismuth neodymium titanate BaBi3.5Nd0.5Ti4O15 was synthesized using the traditional solid-state reaction method. X-ray diffraction analysis confirmed the compound to be a layered tetragonal structure and Raman spectrum indicated that Nd ions occupy the A site. The plate-like morphology with average grain size about 2–4 μm was observed by a scanning electron microscope (SEM). A precision impedance analyzer was used to measure the dielectric properties and impedance spectroscopy of the ceramics. The results show that the temperature of dielectric constant maximum (Tm), the room temperature dielectric constant (εr) and loss (tan δ) at 100 kHz are 287° C, 326 and 0.017, respectively. The modified Curie–Weiss law was used to describe the relaxor behavior of the ceramics which was attributed to the A site cationic disorder. The remnant polarization (2Pr) of the sample was observed to be 1.27 μC/cm2 at room temperature. 相似文献
13.
In this study, we fabricated Ba0.6Sr0.4TiO3 (BST) powders via a high-energy ball-milling (HEBM) method. The processing parameters were optimized to obtain an optimum synthesis condition. BST nano-powders (with a mean grain size of 475 nm) were derived from the precursor milled at 400/800 rpm for 5 h and calcined at 1000 °C for 2 h. This synthesis temperature was much lower than that required by traditional solid state reaction. It was suggested that HEBM is a simple and practical route to synthesize BST nano-powders. 相似文献
14.
(LaxSr1−x)MnO3 (LSMO) and (LaxSr1−x)FeO3 (LSFO) (x = 0.2–0.4) ceramics prepared by a simple and effective reaction-sintering process were investigated. Without any calcination involved, La2O3 and SrCO3 were mixed with MnO2 (LSMO) or Fe2O3 (LSFO) then pressed and sintered directly. LSMO and LSFO ceramics were obtained after 2 and 4 h sintering at 1350–1400 and 1200–1280 °C, respectively. Grain size decreased as La content increased in LSMO and LSFO ceramics. 相似文献
15.
Pure K0.5Na0.5NbO3 powders were prepared at low temperatures by an efficient method using Na2CO3, K2CO3 and Nb2O5 as raw materials and urea as fuel. The phase evolution of the powders was investigated by X-ray diffractometer (XRD) and thermo gravimetric analysis-differential scanning calorimeter (TG-DSC). The phase composition and morphology of the powders were characterized by electron probe microanalysis (EPMA) and scanning electron microscope (SEM), respectively. The results reveal that single-phase K0.5Na0.5NbO3 powder can be obtained at 550 °C by the method. The as-prepared powder is stoichimetric, fine and well-developed. 相似文献
16.
The amorphous hydrated precursor of Li1.2V3O8 was synthesized by soft chemistry method, and then heat-treated in air at several temperatures within the range 200–400 °C. The heat-treatment changed its morphological, structural and charging/discharging performance. The product obtained upon the treatment at 300 °C, consisting of uniform, rod-shaped particles, 100–150 nm in diameter and 300–800 nm in length, displayed the best electrochemical performance in aqueous LiNO3 solution. Its initial discharge capacity amounted to 136.8 mAh g−1 at a rate of C/5, which upon 50 charging/discharging cycles decreased for only 12%. 相似文献
17.
The microwave dielectric properties of (BaxMg1−x)(A0.05Ti0.95)TiO3 (A=Zr, Sn) ceramics were investigated with regard to substitution of Ba for Mg of A-site. The microwave dielectric properties were correlated with the Ba content. With an increase in Ba content from 0.01 to 0.1, the dielectric constant and the τf value increased, but the Q×f value decreased. The sintered (BaxMg1−x)(Zr0.05Ti0.95)TiO3 (called BxMZT) ceramics had a permittivity in the range of 19.1−20.6, quality factor from 180,000 to 25,000 GHz, and variation in temperature coefficient of resonant frequency from −35 to −39 ppm/°C with increasing composition x. For sintered (BaxMg1−x)(Sn0.05Ti0.95)TiO3 (called BxMST) ceramics, the dielectric constant increased from 19 to 20.5, Q×f value increased from 120,000 to 37,000 (GHz), and the τf value increased from −50 to −3.3 ppm/°C as the x increased from 0.01 to 0.1. When A=Sn and x=0.1, (Ba0.1Mg0.9)(Sn0.05Ti0.95)TiO3 ceramics exhibited dielectric constant of 20.5, Q×f value of 37,000 (GHz), and a near-zero τf value of −3.3 ppm/°C sintered at 1210 °C for 4 h. 相似文献
18.
Bo-Ra Kim Hyo-Jin Oh Kang-Seop Yun Sang-Chul Jung Wooseung Kang Sun-Jae Kim 《Progress in Organic Coatings》2013
For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO2/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe2O3 and anatase-TiO2 phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe2O3/TiO2/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe2O3/TiO2/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe2O3/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe2O3/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO2 base layer beneath the Fe2O3 layer. 相似文献
19.
Ying-Chieh Lee Tai-Kuang LeeJhen-Hau Jan 《Journal of the European Ceramic Society》2011,31(16):3145-3152
This article studies the microstructure and piezoelectric properties of a ceramic lead-free NBT under different amount of ZnO doping. X-ray diffraction shows that Zn2+ diffuses into the lattice of (Bi0.5Na0.5)TiO3 to form a solid solution with a pure perovskite structure. By modifying the zinc oxide content, the sintering behavior of (Bi0.5Na0.5)TiO3 ceramics was significantly improved and the grain size was increased. The piezoelectric coefficient d33 for the 1.0 wt.% ZnO-doped (Bi0.5Na0.5)TiO3 ceramics sintered at 1050 °C was found to be 95 pC/N, and the electromechanical coupling factor kp = 0.13. However, the piezoelectric coefficient d33 for the 0.5 wt.% ZnO-doped (Bi0.5Na0.5)TiO3 ceramics sintered at 1140 °C was found to be 110 pC/N, and the electromechanical coupling factor kp = 0.17. 相似文献
20.
Yonggang Wang Gang Xu Linlin Yang Zhaohui Ren Xiao Wei Wenjian Weng Piyi Du Ge Shen Gaorong Han 《Ceramics International》2009
Na0.5Bi0.5TiO3 microcubes with smooth faces and clear, well-defined edges have been successfully prepared for the first time by a simple hydrothermal method without any surfactants. The as-prepared Na0.5Bi0.5TiO3 microcubes showed an obvious emission band compared with nanoparticles, which is attributed to the different NBT morphology and size. 相似文献