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1.
Dielectric properties and relaxation phenomena of hybrid material (functionalized nanosilver/BaTiO3/epoxy) were studied as a function of ceramic content. Nanoparticles were obtained through chemical reduction in ethanol and
triethylenetetramine. Epoxy resin, functionalized Ag and BaTiO3 were mixed and composites were prepared onto glass substrates by dipping technique. Samples containing various amounts of
ceramic filler were examined by thermal and SEM analysis. Dielectric measurements were performed at different frequencies
and temperatures. It was found that hybrid materials had high permittivities and their relaxation processes were influenced
by the epoxy resin near its T
g, while metallic and ceramic content modified the real permittivity values. 相似文献
2.
Leandro Alfredo Ramajo Maria Marta Reboredo Miriam Susana Castro 《Journal of Materials Science》2007,42(10):3685-3691
Polymer composites of epoxy resin and Nb2O5 doped BaTiO3 were prepared in the form of film (thickness 30–300 μm) using a dipping technique. Samples containing various amounts of
ceramic filler were examined by thermal analysis and SEM analysis. Dielectric measurements were performed from 20 Hz to 1 MHz
and 20 °C to 120 °C. It was found that the final materials had high permittivities increasing with the filler concentration.
Electrical relaxations were assigned to interfacial phenomena due to the particles and α-relaxation because of the resin. 相似文献
3.
4.
V. V. Sydorchuk S. V. Khalameida V. P. Klimenko V. A. Mikheev V. A. Zazhigalov 《Inorganic Materials》2012,48(9):925-930
Barium titanate has been synthesized in pores of oxide matrices using barium titanyl oxalate and barium titanyl peroxide (peroxotitanate) by a sol-gel process and by dispersing the precursors together with pyrogenic oxides in water. The composites were characterized by X-ray diffraction, differential thermal analysis, nitrogen adsorption measurements, transmission electron microscopy, dielectric spectroscopy, and photocatalytic activity measurements. The results demonstrate that the pore structure of the composites forms concurrently with their crystal structure. The composite produced using pyrogenic alumina has high dielectric permittivity. 相似文献
5.
Sung-Dong Cho Sang-Yong Lee Jin-Gul Hyun Kyung-Wook Paik 《Journal of Materials Science: Materials in Electronics》2005,16(2):77-84
Polymer/ceramic composites are the most promising embedded capacitor material for organic substrates application. Predicting the effective dielectric constant of polymer/ceramic composites is very important for design of composite materials. In this paper, we measured the dielectric constant of epoxy/BaTiO3 composite embedded capacitor films with various BaTiO3 particles loading for 5 different sizes BaTiO3 powders. Experimental data were fitted to several theoretical equations to find the equation useful for the prediction of the effective dielectric constant of polymer/ceramic composites and also to estimate the dielectric constant of BaTiO3 powders. The Lichtenecker equation and the Jayasundere-Smith equation were useful for the prediction of the effective dielectric constant of epoxy/BaTiO3 composites. And calculated dielectric constants of the BaTiO3 powders were in the range of 100 to 600, which were lower than the dielectric constant of BaTiO3 bulk ceramics probably due to the presence of voids or pores. 相似文献
6.
7.
xBaTiO3 + (1 − x)Ni0.93Co0.02Cu0.05Fe2O4 (x = 0.5, 0.6, 0.7, 0.8) composites with ferroelectric–ferromagnetic characteristics were synthesized by the ceramic sintering
technique. The presence of constituent phases in the composites was confirmed by X-ray diffraction studies. The average grain
size was calculated by using a scanning electron micrograph. The dielectric characteristics were studied in the 100 kHz to
15 MHz. The dielectric constant changed higher with ferroelectric content increasing; and it was constant in this frequency
range. The relation of dielectric constant with temperature was researched at 1, 10, 100 kHz. The Curie temperature would
be higher with frequency increasing. The hysteresis behavior was studied to understand the magnetic properties such as saturation
magnetization (M
s). The composites were a typical soft magnetic character with low coercive force. Both the ferroelectric and ferromagnetic
phases preserve their basic properties in the bulk composite, thus these composites are good candidates as magnetoelectric
materials. 相似文献
8.
Bo Li Shuren Zhang Xiaohua Zhou Sheng Wang Zhu Chen 《Journal of Materials Science》2007,42(6):2090-2096
BaTiO3-based ultrafine nonreducible dielectrics for multilayer ceramic capacitors were prepared by a newly developed nanocomposite
doping process. According to TG-DTA, XRD and TEM analysis, the nanocomposite dopants via sol–gel method were uniform and well
dispersive. The micromechanism was investigated based on comparing conventional process with nano-doping process. It indicated
that due to the special nano-effect, doping effect of additives became more effective and the microstructure and dielectric
properties of ceramics were improved. The results showed that high performance dielectrics satisfying X8R specification were
achieved, with high dielectric constant of 2,900, low dielectric loss of 0.6% and large insulation resistivity of 1012 Ω cm. 相似文献
9.
We have studied the effect of heat treatment of the starting BaTiO3 powder on the dielectric properties and microstructure of X7R-type BaTiO3-based ceramics. The results demonstrate that annealing of BaTiO3 stabilizes the degree of tetragonality in the crystal lattice of the ceramics. Microstructural analysis shows that the annealing
temperature has no effect on the average grain size of the ceramics. Increasing the BaTiO3 annealing temperature increases the dielectric permittivity of the core phase and reduces the temperature coefficient of
capacitance (TCC). We obtained an X7R-type BaTiO3-based ceramic material (BaTiO3 annealing temperature, 1150°C; firing temperature, 1160°C) with the following properties: ɛ25°C = 2230, TCC = ±12% (−55 to 125°C), and tanδ25°C = 0.013. 相似文献
10.
Haibo Yang Ying Lin Jianfeng Zhu Fen Wang 《Journal of Materials Science: Materials in Electronics》2010,21(4):368-372
Dense Ca(Zn1/3Nb2/3)O3/NiZn ferrite composites with homogeneously fine microstructures were prepared through conventional solid-state method. The
powder XRD patterns confirm the coexistence of the two phases. The dielectric properties in the low frequency range (100 Hz–1 MHz)
follow the rule of Maxwell–Wagner interfacial polarization. The dielectric and magnetic properties in the high frequency range
(10 MHz–1 GHz) are also reported. The results show that this kind of magnetic–dielectric composites could be used in high-frequency
communications for the capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. 相似文献
11.
Strontium titanate and barium titanate ceramics prepared by a reaction-sintering process were investigated. The mixture of
raw materials of stoichiometric SrTiO3 and BaTiO3 was pressed and sintered into ceramics without any calcination stage involved. A density 4.99 g/cm3 (97.5% of the theoretic value) was found in SrTiO3 after 6 h sintering at 1,370 °C. Grains less than 1.5 μm were formed at 1,300–1,330 °C and became 2.2–3.3 μm at 1,350–1,370 °C
SrTiO3. A density 5.89 g/cm3 (97.9% of the theoretic value) was found in BaTiO3 after 6 h sintering at 1,400 °C. Merged grains were observed in BaTiO3 and were less than 10 μm after sintered at 1,400 °C. 相似文献
12.
Preparation of epoxy/SiO2-TiO2 composites is investigated in this paper. The products are characterized by FT-IR spectroscopy. Results of FT-IR spectroscopy and atom force microscope (AFM) demonstrated that epoxy chains have been covalently bonded to the surface of the SiO2-TiO2 particles. The particles sized of SiO2-TiO2 are about 20–50 nm, which characterized by AFM. The properties of composites such as impact strength, flexural strength, tensile strength and ring-on-block wear are also investigated. Dry sliding wear tests showed that the SiO2-TiO2 particles could improve the wear resistance of the epoxy matrix even though the content of the SiO2-TiO2 particles was at a relatively low level (1.95–2.65 wt%). This makes it possible to develop novel type of epoxy-based materials with improved wear resistance for various applications. The worn surface was observed by scanning electron microscopy (SEM), and mechanisms for the improvement are discussed in this paper 相似文献
13.
将颗粒尺寸分布较宽的钛酸钡(BT)粉末与环氧树脂采用溶液共混旋涂工艺制备了嵌入式电容器材料,并对该复合材料的显微结构、晶相、热稳定性及介电性能进行了分析.研究表明,该复合材料的介电常数及介电损耗与陶瓷相含量和陶瓷粉末的分散有关;在20~150kHz频率范围内,复合材料介电常数的变化较为稳定,而介电损耗值均在0.036~0.039之间,随频率增大略有增大;受BT粒子的影响,复合材料基体聚合物的有序排列分子结构被破坏,环氧树脂分子链的排列密度降低;BT粉末的加入及BT含量的增加均导致材料体系的固化温度和热分解温度提高. 相似文献
14.
S. A. Lokare R. S. Devan D. R. Patil Y. D. Kolekar K. K. Patankar B. K. Chougule 《Journal of Materials Science》2007,42(24):10250-10253
Polycrystalline samples of mixed composites of Ni0.93Co0.02Mn0.05Fe2O4 + BaTiO3 were prepared by conventional double sintering ceramic method. The phase analysis was carried out by using X-ray diffraction
technique. Variation of dc resistivity and thermo emf was studied as a function of temperature. AC conductivity (σac) was investigated in the frequency range 100 Hz–1 MHz. The loss tangent (tan δ) measurements conclude that the conduction
mechanism in these samples is due to small polaron hopping. The magnetoelectric conversion factor, i.e. dc(ME)
H
was studied as a function of intensity of magnetic field and the maximum value 407 μV/cm/Oe was observed at a field of 0.8 kOe
in a composite with 85% BaTiO3 and 15% Ni0.93Co0.02Mn0.05Fe2O4 phase. 相似文献
15.
Dense nanocrystalline BaTiO3 ceramics are successfully prepared by the high pressure assisted sintering. Microstructures are observed by scanning electronic
microscopes. The grain sizes are estimated to be about 30 and 150 nm. In comparison, BaTiO3 ceramics with the grain size of 600 nm and 1.5 μm are fabricated by conventional pressure-less sintering. The thermal properties
of BaTiO3 ceramics with different grain sizes are investigated by differential scanning calorimetry and thermal expansion. The results
suggest that the enthalpy values for the tetragonal-cubic transition decreased and the thermal expansion values increased
with decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size. 相似文献
16.
17.
Bo Li Shuren Zhang Xiaohua Zhou Zhu Chen Sheng Wang 《Journal of Materials Science》2007,42(13):5223-5228
The microstructures and dielectric properties of Y/Zn codoped BaTiO3 ceramics sintered in a reducing atmosphere were investigated. XRD analysis indicated the crystal structure of samples change
from tetragonal to pseudocubic with increasing Y2O3 and ZnO content. SEM micrographs showed Y2O3 can suppress grain growth more effectively compared with ZnO, which is ascribed to the presence of second phase Y2Ti2O7. Proper amount of Y2O3 and ZnO can significantly improve the dielectric temperature characteristics due to the formation of grain core-shell structure.
The high performance dielectrics meeting the X7R code were achieved by codoping 1.5 mol% Y2O3 and 3.0 mol% ZnO. 相似文献
18.
《Composites Part B》2013,45(1):128-132
Barium titanate (BaTiO3) filled polymethylmethacrylate (PMMA) composites were prepared using the simple solution method followed by hot pressing. The content of BaTiO3 was varied from 0 to 65 vol.%. Scanning electron microscopy showed good dispersion and adhesion of BaTiO3 with the PMMA matrix. The dielectric constant of the composites increased significantly. There was weak dispersion in the dielectric constant of the composites (up to 45 vol.%) with frequency between 100 Hz and 15 MHz. The dissipation factor of the composites increased from 0.021 for pure PMMA to 0.029 for 45 vol.% composites. However, 65 vol.% composite showed dispersion in dielectric constant with increasing frequency and higher dissipation factor. The Lichtenecker equation agreed well with the experimental data. The microhardness and the glass transition temperature of the composites increased approximately 4.7-fold and 42 °C, respectively, compared to pure PMMA. The CTE of the 65 vol.% composite is close to that of copper. 相似文献
19.
The microstructure and dielectric properties of Yb-Mn- and Yb-Ni-substituted BaTiO3 ceramics are investigated in this paper. Both Yb-Mn- and Yb-Ni-substituted BaTiO3 ceramics satisfy the X8R specification (−55 ∘C to 150 ∘C, Δ C = ±15% or less) for automotive application when CaZrO3 is incorporated in the formulations. It is found that both Mn and Ni ions can suppress the diffusion of Yb and CaZrO3 into BaTiO3 grains, resulting in formation of core-shell structures in the grains. It is found that Mn is more favorable to stabilize
the core-shell structure in BaTiO3 ceramics as compared with Ni. 相似文献
20.
S. H. Shah P. D. Bristowe A. M. Kolpak A. M. Rappe 《Journal of Materials Science》2008,43(11):3750-3760
The geometrical, chemical and ferroelectric properties of a new nanoscale short-period three-component SrTiO3/BaTiO3/PbTiO3 perovskite superlattice are investigated using a first principles density functional approach. The study focuses on varying
the thickness of each component in the superlattice and determining the resulting lattice distortion and total polarization.
Thicknesses of up to three unit cells in a single component are considered and the in-plane lattice constants normal to the
[001] stacking direction are fixed to the bulk SrTiO3 values to simulate a rigid substrate. It is found that the PbTiO3 layers play a key role in strain and polarization enhancement. By increasing the amount of PbTiO3 in the superlattices the strain in the other components increases significantly resulting in an enhanced total polarization
of the superlattice relative to bulk BaTiO3. Increasing the number of BaTiO3 layers also improves the overall polarization. All the SrTiO3 layers in each superlattice are found to be highly polarized. Many of the calculated features are similar to those found
previously by others for the SrTiO3/BaTiO3/CaTiO3 superlattice, although in the present study significantly greater enhancement factors and polarization values are found.
The predicted enhancement of the polarization is mostly attributed to lattice strain due to mismatch of the in-plane lattice
constant of the three-component materials. 相似文献