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1.
D.S. Jung S.K. Hong J.S. Cho Y.C. Kang 《Applied Physics A: Materials Science & Processing》2007,89(3):769-774
Fine-sized BaO-ZnO-B2O3-SiO2 (BZBS) glass powders were directly prepared by high temperature spray pyrolysis. The hollow glass powders prepared at low
preparation temperature of 1000 °C had a low density of 2.65 g/cm3. However, the densities of the BZBS powders obtained at preparation temperatures of 1200 and 1400 °C were each 3.92 and 4.13 g/cm3. The mean size of the BZBS glass powders prepared by spray pyrolysis at preparation temperature of 1400 °C was 0.98 μm. The
glass transition temperature (Tg) of the prepared BZBS glass powders was 518.9 °C. The dielectric layers formed from the prepared BZBS glass powders with
a dense structure had a clean surface and a dense inner structure without voids at the firing temperature of 580 °C. The transparencies
of the dielectric layers formed from the prepared BZBS glass powders were higher than 90% within the visible range.
PACS 42.70.Ce; 85.60.Pg; 71.55.Jv 相似文献
2.
The double perovskite Sr2NiMoO6 powders and ceramics were prepared by two different (conventional and precursor) solid-state reaction methods. The phase
structure was characterized by XRD and TEM techniques. It has been indicated that single-phase perovskite powders were obtained
when calcined in air at 1300°C. However, nano-particles of the size 30–60 nm have been found in powders prepared with the
precursor method, while those from the conventional route exhibit large irregular shaped particles with aggregation. The dielectric
properties (ε
r
and tanδ) were also examined in the sintered ceramics. The results showed the transition point at 280°C for conventional route, while
no clear phase change was observed in ceramics from the precursor route. These observations clearly indicate that the different
starting processes affected the phase formation behavior and the electrical properties of Sr2NiMoO6 ceramics. 相似文献
3.
F. Wu X.M. Li W.D. Yu X.D. Gao X. Zhang 《Applied Physics A: Materials Science & Processing》2007,88(4):781-784
Thin films of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN-PT) have been grown on Ir/MgO buffered Si(100) substrates at different substrate temperatures by pulsed laser deposition.
Crystalline phases as well as preferred orientations in the PMN-PT films were investigated by X-ray diffraction analysis (XRD).
The microstructure, dielectric and ferroelectric properties of PMN-PT film prepared at 650 °C were studied. The results show
that the film prepared at 650 °C exhibits pure perovskite phase and single c-axis orientation. The dielectric constant and
dissipation factor of the single c-axis oriented film are 1000 and 0.04 at a frequency of 1 kHz, while the remnant polarization
and coercive field are about 13.0 μC/cm2 and 100 kV/cm under an electric field of 480 kV/cm, respectively.
PACS 81.15.Fg; 77.80.-e; 77. 22.Ej; 77.55.+f; 85.50.Gk 相似文献
4.
Lithium manganese oxide powders have been successfully prepared by a molten salt synthesis using eutectic mixture of LiCl
and MnO2 salt at 900 °C. The synthesis was performed in open atmosphere. The crystalline powders were characterized for their phase
identification using X-ray diffraction analysis. The physicochemical properties of the lithium manganese oxide powders are
investigated by thermal analysis (thermo gravimetric analysis/ differential thermal analysis), Fourier transform infrared
spectroscopy, Raman spectroscopy, atomic absorption spectroscopy, electron spin resonance spectroscopy, and scanning electron
microscopy. This work shows the feasibility for obtaining lithium manganese oxide at low-temperature molten salt flux method. 相似文献
5.
Fast oxide-ion conductors La2Mo2-xWxO9 (x = 0–1) have been prepared using mechanochemical activation (MA) of starting oxides in a high-power planetary ball mill. Studies of La2Mo2-xWxO9 genesis and structural properties using thermal analysis, XRD, SEM, IR, and Raman spectroscopy have revealed that MA results in the formation of an amorphous precursor, while the cubic β-phase is formed after calcination at 700–900 °C. Due to a high dispersion of powders, high-density pellets of W-LAMOX ceramics have been obtained already after sintering at 950 °C. Their electrical conductivity measured by the impedance spectroscopy depends on the W concentration being sufficiently high (up to 5.6?10?3 S/cm at 630 °C) at temperatures below 650 °C. 相似文献
6.
C. Masingboon S. Maensiri T. Yamwong P.L. Anderson S. Seraphin 《Applied Physics A: Materials Science & Processing》2008,91(1):87-95
Nanocrystalline CaCu3Ti4O12 powders with particle sizes of 50–90 nm were synthesized by a simple method using Ca(NO3)2·4H2O, Cu(NO3)2·4H2O, titanium(diisoproproxide) bis(2,4-pentanedionate) and freshly extracted egg white (ovalbumin) in aqueous medium. The synthesized
precursor was characterized by TG-DTA to determine the thermal decomposition and crystallization temperature which was found
to be at above 400 °C. The precursor was calcined at 700 and 800 °C in air for 8 h to obtain nanocrystalline powders of CaCu3Ti4O12. The calcined CaCu3Ti4O12 powders were characterized by XRD, FTIR, SEM and TEM. Sintering of the powders was conducted in air at 1100 °C for 16 h.
The XRD results indicated that all sintered samples have a typical perovskite CaCu3Ti4O12 structure and a small amount of CuO, although the sintered sample of the 700 °C calcined powders contained some amount of
CaTiO3. SEM micrographs showed the average grain sizes of 12.0±7.8 and 15.5±8.9 μm for the sintered CaCu3Ti4O12 ceramics prepared using the CaCu3Ti4O12 powders calcined at 700 and 800 °C, respectively. The sintered samples exhibit a giant dielectric constant, ε′ of ∼ 1.5–5×104. The dielectric behavior of both samples exhibits Debye-like relaxation, and can be explained based on a Maxwell–Wagner model.
PACS 77.22.Gm; 81.05.Je; 81.07.Wx; 81.20.Ev 相似文献
7.
In order to study the influence of powder calcination temperature on lithium ion conductivity, synthesized Li1.3Ti1.7Al0.3(PO4)3 (LATP) was calcined at temperatures between 750 and 900 °C. The shape and size of the particles were characterized employing scanning electron microscopy (SEM), and specific surface area of the obtained powder was measured. The crystallinity grade of different heat-treated powders was calculated from XRD spectra. Posteriorly, all powders were sintered at 1100 °C employing field-assisted sintering (SPS), and the electrical properties were correlated to the calcination conditions. The highest ionic conductivity was observed for samples made out of powders calcined at 900 °C. 相似文献
8.
S. Bhaskar Reddy K. Prasad Rao M.S. Ramachandra Rao 《Applied Physics A: Materials Science & Processing》2007,89(4):1011-1015
Single phase Sr substituted BaZr0.1Ti0.9O3 (also known as BZT) ceramics with a formula Ba1-xSrxZr0.1Ti0.9O3 (x=0.10, 0.20, 0.30, 0.40 and 0.50) are prepared using a solid state reaction of mixed oxides at 1250 °C for 15 h. Analysis
of XRD patterns of the ceramic powders show that Sr substitutes into Ba sites and reduces the lattice parameter. The powders
are sintered at 1600 °C for 6 h to investigate the microstructure and functional properties. It is found that strontium substitution
significantly modifies the microstructure and greatly influences the dielectric properties. The increase in Sr content reduces
the ceramic grain size and results in spherical grains. With an increase in Sr content, the Curie temperature is lowered,
and the relative permittivity maximum is increased and broadened. In Ba1-xSrxZr0.1Ti0.9O3 with x=0.30, the relative permittivity reached a maximum of 26600 and with further increase of Sr content, the relative permittivity
is lowered and the phase transition is found to be broad and diffused. The ferroelectric hysteresis characteristics are discussed
in detail.
PACS 77.84.-s; 77.80.Bh; 77.22.Ch; 77.84.Dy; 77.22.-d 相似文献
9.
In this study, well-crystallized Li4Mn5O12 powder was synthesized by a self-propagating combustion method using citric acid as a reducing agent. Various conditions were studied in order to find the optimal conditions for the synthesis of pure Li4Mn5O12. The precursor obtained was then annealed at different temperatures for 24 h in a furnace. X-ray diffraction results showed that Li4Mn5O12 crystallite is stable at relatively low temperature of 400 °C but decompose to spinel LiMn2O4 and monoclinic Li2MnO3 at temperatures higher than 500 °C. The prepared samples were also characterized by FESEM and charge-discharge tests. The result showed that the specific capacity of 70.7 mAh/g was obtained within potential range of 4.2 to 2.5 V at constant current of 1.0 mA. The electrochemical performances of Li4Mn5O12 material was further discussed in this paper. 相似文献
10.
Longlong Xue Yunjiao Li Qiang Han Qianye Su Yongxiang Chen Jianguo Li Tongxing Lei Yujie Chen Jian Chen 《Ionics》2018,24(10):2957-2963
The lithiated transition metal oxide precursor (LNCMO) with typical α-NaFeO2 structure and imperfect crystallinity, obtained from a hydrothermal process, was pretreated at 500 °C and then subjected to sintering at 800–920 °C to synthesize the ternary layered LiNi0.5Co0.2Mn0.3O2 (NCM523). X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge testing were used for investigating the effect of the high-temperature crystallization on the properties of the NCM523 cathode materials. The results show that the materials heated at 880–900 °C possess superior cation ordering, perfect crystallinity, and excellent electrochemical performances, among which the material heated at 900 °C delivers better performances, with the initial discharge capacity of 152.6 mAh g?1 at 0.5 C over 3.0 to 4.3 V and the capacity retention of 95.5% after 50 cycles. Furthermore, the effect of the high-temperature crystallization on the Li+ diffusion coefficient, potential polarization, and electrochemical resistance are discussed. 相似文献
11.
E. Govea-Alcaide I. García-Fornaris P. Muné R. F. Jardim 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):373-378
Measurements of the electrical resistivity as a function
of temperature, ρ(T), for different values of applied
magnetic field, Ba (0 ≤ Ba ≤ 50 mT), were performed in
polycrystalline samples of Bi1.65Pb0.35Sr2Ca2
Cu3O10+δ subjected to different uniaxial compacting
pressure (UCP). We have found appreciable differences in the grain
orientation between samples by using X-ray diffractometry. From
the X-ray diffraction patterns performed, in powder and pellet
samples, we have estimated the Lotgering factor along the (00l)
direction, F(00l). The results indicate that F(00l)
increases ~23% with increasing UCP suggesting that grains
of these samples are preferentially aligned along the c-axis,
which is parallel to the compacting direction. The resistive
transition of the samples have been interpreted in terms of the
thermally activated flux-creep model. In addition, the effective
intergranular pinning energy, U0, have been determined for
different applied magnetic field. The magnetic field dependence of
U0, for Ba > 8 mT, was found to follow a H- α
dependence with α = 0.5 for all samples. The analysis of the
experimental data strongly suggested that increasing UCP results
in appreciable changes in both the grain alignment and the grain
connectivity of the samples. We have successfully interpreted the
data by considering the existence of three different
superconducting levels within the samples: the superconducting
grains, the weak-links, and the superconducting clusters. 相似文献
12.
Fei Qi Anna Moiseev Joachim Deubener Alfred Weber 《Journal of nanoparticle research》2011,13(3):1325-1334
Anatase is the low-temperature (300–550 °C) crystalline polymorph of TiO2 and it transforms to rutile upon heating. For applications utilizing the photocatalytic properties of nanoscale anatase at
elevated temperatures (over 600 °C) the issue of phase stabilisation is of major interest. In this study, binary TiO2/SiO2 particles were synthesized by a flame aerosol process with TiCl4 and SiCl4 as precursors. The theoretical Si/Ti ratio was varied in the range of 0.7–1.3 mol/mol. The synthesized TiO2/SiO2 samples were heat treated at 900 and 1,000 °C for 3 h to determine the thermostability of anatase. Pyrogenic TiO2 P25 (from Evonik/Degussa, Germany) widely applied as photocatalyst was used as non-thermostabilized reference material for
comparison of photocatalytic activity of powders. Both the non-calcinated and calcinated powders were characterized by means
of XRD, TEM and BET. Photocatalytic activity was examined with dichloroacetic acid (DCA) chosen as a model compound. It was
found that SiO2 stabilized the material retarding the collapse of catalyst surface area during calcination. The weighted anatase content
of 85% remains completely unchanged even after calcination at 1,000 °C. The presence of SiO2 layer/bridge as spacer between TiO2 particles freezes the grain growth: the average crystallite size increased negligibly from 17 to 18 nm even during the calcination
at 1,000 °C. Due to the stabilizing effect of SiO2 the titania nanoparticles calcinated at 900 and 1,000 °C show significant photocatalytic activity. Furthermore, the increase
in photocatalytic activity with calcination temperature indicates that the titania surface becomes more accessible either
due to intensified cracking of the SiO2 layer or due to enhanced transport of SiO2 into the necks thus releasing additional titania surface. 相似文献
13.
Ultrafine-structure La0.65Sr0.35MnO3 (LSM) powders synthesized by self-propagating combustion method have been used to fabricate sensing electrodes (SEs) for NO2 mixed-potential sensors based on yttria-stabilized zirconia (YSZ). This type of sensor was found to provide better NO2 sensitivity at 500 °C than sensors with LSM powders synthesized by traditional solid-state methods. The response values of the sensor have good linear relationship (sensitivity 36.6 mV/decade and linear fit 0.99) with the logarithm of NO2 concentration varying from 30 to 500 ppm. The influence of sintering temperature (1000, 1100, 1200, and 1300 °C) on sensor response was also examined and was found to have a significant effect on the morphology of LSM-SEs. Moreover, in the presence of NO, CO2, CO, and NO2, the sensor exhibited good NO2 selectivity. 相似文献
14.
Banarji Behera Pratibindhya Nayak Ram N. P. Choudhary 《Central European Journal of Physics》2008,6(2):289-295
A polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis
of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform
grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various
frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed
by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy
(CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy
of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed
to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident
from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits
Arrhenius type of electrical conductivity.
相似文献
15.
Li-Jiao Zhou Zhou-Lan Yin Zhi-Ying Ding Xin-Hai Li Zhi-Xing Wang Hua-Jun Guo 《Ionics》2018,24(9):2533-2542
The Li[Li0.2Mn0.54Ni0.13Co0.13]O2 coated with CeO2 has been fabricated by an ionic interfusion method. Both the bare and the CeO2-coated samples have a typical layered structure with R-3m and C2/m space group. The results of XRD and TEM images display that the CeO2 coating layer on the precursor could enhance the growth of electrochemically active surface planes ((010), (110), and (100) planes) in the following ionic interfusion process. The results of galvanostatic cycling tests demonstrate that the CeO2-coated sample has a discharge capacity of 261.81 mAh g?1 with an increased initial Coulombic efficiency from 62.4 to 69.1% at 0.05 °C compared with that of bare sample and delivers an improved capacity retention from 71.7 to 83.4% after 100 cycles at 1 °C (1 °C?=?250 mA g?1). The results of electrochemical performances confirm that the surface modification sample exhibits less capacity fading, lower voltage decay, and less polarization. 相似文献
16.
Xiaoling Cui Songli Du Konglei Zhu Shan Geng Dongni Zhao Xiangfei Li Fengjuan Tang Shiyou Li 《Ionics》2018,24(3):697-706
By employment of nano-sized pre-prepared Mn3O4 as precursor, LiMn2O4 particles have been successfully prepared by facile solid state method and sol-gel route, respectively. And the reaction mechanism of the used precursors of Mn3O4 is studied. The structure, morphology, and element distribution of the as-synthesized LiMn2O4 samples are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared with LiMn2O4 synthesized by facile solid state method (SS-LMO), LiMn2O4 synthesized by modified sol-gel route (SG-LMO) possesses higher crystallinity, smaller average particle size (~175 nm), higher lithium chemical diffusion coefficient (1.17 × 10?11 cm2 s?1), as well as superior electrochemical performance. For example, the cell based on SG-LMO can deliver a capacity of 85.5 mAh g?1 at a high rate of 5 °C, and manifests 88.3% capacity retention after 100 cycles at 0.5 °C when cycling at 45 °C. The good electrochemical performance of the cell based on SG-LMO is ascribed mainly to its small particle size, high degree of dispersion, and uniform element distribution in bulk material. In addition, the lower polarization potential accelerates Li+ ion migration, and the lower atom location confused degree maintains integrity of crystal structure, both of which can effectively improve the rate capability and cyclability of SG-LMO. 相似文献
17.
Lalit Sharma Ankush Bhatia Loïc Assaud Sylvain Franger Prabeer Barpanda 《Ionics》2018,24(8):2187-2192
Exploring soft-chemistry synthesis of Fe-based battery cathode materials, we have optimized combustion synthesis as an ultra-rapid approach to produce Na2FePO4F fluorophosphate cathode. It yields nanoscale, carbon-coated target product by annealing (at 600 °C) for just 1 min. The purity of the material crystallizing in the orthorhombic structure was confirmed by powder X-ray diffraction pattern and XPS analysis, while the morphology was studied by scanning electron microscopy. The as-synthesized material exhibits good electrochemical performance delivering a first discharge capacity of more than 70 mAh/g at C/10 rate versus both Li+/Li and Na+/Na, hence acting as an efficient host for both Li-ion and Na-ion insertion. Combustion synthesis can be employed as an economic route for synthesis and rapid screening of various phosphate-based insertion materials. 相似文献
18.
To improve the electrochemical performance of Nickel-rich cathode material LiNi0.8Co0.1Mn0.1O2, an in situ coating technique with Li2ZrO3 is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li2ZrO3 coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li2ZrO3 coating plays an important role to enhance the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 and reveal that choosing suitable temperature and current is critical for solving battery safety problem. 相似文献
19.
The polycrystalline Bi8Fe6Ti3O27 compound was prepared by a high-temperature solid-state reaction technique. Preliminary structural analysis by X-ray diffraction
(XRD) confirms the formation of a single-phase compound in an orthorhombic crystal system at room temperature. The elemental
content of the compound was analyzed by EDAX microanalysis. Microstructural analysis by scanning electron microscopy (SEM)
shows that the compound has well defined grains, which are distributed uniformly throughout the surface of the pellet sample.
Detailed studies of temperature-dependent dielectric response at various frequencies show dielectric anomalies at 380, 389
and 403°C for 10 kHz, 100 kHz, and 1 MHz respectively. The hysteresis loop observed by applying an electric field of 12 kV/cm
on the poled sample with smaller remanent polarization supports the existence of ferroelectricity in this material. The value
of d33 of the compound was found to be 19 pC/N.
相似文献
20.
Zhongliang Xiao Chaoming Hu Liubin Song Lingjun Li Zhong Cao Huali Zhu Jiao Liu Xinyu Li Fuli Tang 《Ionics》2018,24(1):91-98
The LiNi0.8Co0.1Mn0.1O2 with LiAlO2 coating was obtained by hydrolysis–hydrothermal method. The morphology of the composite was characterized by SEM, TEM, and EDS. The results showed that the LiAlO2 layer was almost completely covered on the surface of particle, and the thickness of coating was about 8–12 nm. The LiAlO2 coating suppressed side reaction between composite and electrolyte; thus, the electrochemical performance of the LiAlO2-coated LiNi0.8Co0.1Mn0.1O2 was improved at 40 °C. The LiAlO2-coated sample delivered a high discharge capacity of 181.2 mAh g?1 (1 C) with 93.5% capacity retention after 100 cycles at room temperature and 87.4% capacity retention after 100 cycles at 40 °C. LiAlO2-coated material exhibited an excellent cycling stability and thermal stability compared with the pristine material. These works will contribute to the battery structure optimization and design. 相似文献