Mechanochemical preparation of BaTiO3–Ni nanocomposites with high dielectric constant (original) (raw)
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Synthesis, sintering and dielectric properties of a BaTiO3–Ni composite
Barium titanate–nickel composites (BaTiO3–Ni) were synthesized at a low temperature using a sol–gel method and sintered in a reducing atmosphere. XRD,FE-SEM,Raman spectroscopy and TGA were performed to confirm the phases of BaTiO3 and Ni,themorphology and tetragonal crystal structure of BaTiO3 and the weight loss.The results indicate that by controlling the experimental conditions (temperature and atmosphere) during the sintering process, the grain size of the BaTiO3–Ni composite can be controlled.The average grain size of the dense BaTiO3–Ni composite was in the range of 0.6–1.5 mm. In addition,the dielectric constant increased from 2000 for monolithic BaTiO3 to 11,000 by increasing the Ni content.The enhanced dielectric properties of the BaTiO3–Ni composite are due to the well-dispersed nickel particles in the BaTiO3 matrix.
Japanese Journal of Applied Physics
The grain size effect on the dielectric, ferroelectric, and piezoelectric properties of BaTiO 3 (BT) ceramics with different Ba/Ti ratios, prepared by solid-state reaction and conventional sintering, was investigated, and the corresponding electrical properties of these ceramics with similar grain size were compared. The BT ceramics with Ba/Ti ratios of 0.997, 1.000, and 1.003 and grain sizes of approximately 1 μm exhibited dielectric constants of 4265, 4275, and 4835 and converse piezoelectric coefficients, d 33 *, of 703, 645, and 466 pm V −1 , respectively. The remanent polarization, P r , was relatively higher for Ba-excess BT ceramics. These results indicated that, in Ti-excess BT ceramics, domain walls were strongly pinned due to oxygen vacancies under small electric fields and they were de-pinned at high electric fields, contributing to the higher d 33 *, while the orientation of domains in high electric fields did not retain upon electric field unloading, resulting in lower P r .
Ferroelectric BaTiO 3 nanoceramics prepared by a three-step high-pressure sintering method
physica status solidi (a), 2007
Dense BaTiO 3 nanoceramics with a homogeneous grain size of 30 nm were prepared at 6 GPa, 1000 °C using a three-step high-pressure sintering method. The microstructure of the ceramics obtained is uniform and the relative density is above 98% of the theoretical value. Similar to normal BaTiO 3 ceramics, successive phase transitions are observed in the 30 nm BaTiO 3 ceramics using variable-temperature X-ray diffraction measurements. Furthermore the 30 nm BaTiO 3 ceramics reveal ferroelectric properties after being post-annealed at low temperature in O 2 atmosphere, but the phase transition temperature from paraelectric to ferroelectric phase is 10 °C lower than that of a normal bulk sample. The results indicate that dense 30 nm BaTiO 3 ceramics retain ferroelectricity above room temperature.
2017
(1-x)Na 0.5 Bi 2. 5Nb 2 O 9-xBaTiO 3 (NBN-BT, x = 0~0.15) 3-0 type composite high-temperature piezoelectric ceramics with T c values over 680 º C are prepared by solid state reaction method. Structural analysis demonstrates that nanosized BaTiO 3 (TB) is preferable to form solid solution with NBN matrix and the solid solution limit of NBN and BT is about x = 0.08. When x > 0.08, BaTiO 3 has a great effect on the grain growth during sintering and a secondary phase appears at the grain boundaries to form NBN-BT composite ceramics. The d 33 values and electrical resistivity of NBN-BT composite ceramics are about 50% and 1~2 orders of magnitude higher than those of pure NBN ceramics, due to the substitution induced piezoactivity from the rotation/tilting of oxygen octahedral and the formation of solid solution promoting the densification sintering, respectively. Therefore, a compromise between enhanced electrical resistivity, large d 33 and high T c , has been achieved by the formation of appropriate composites, which could shed light on how to obtain novel Aurivillius ferroelectrics for practical high-temperature applications.
Ceramics International, 2012
Barium titanate/silicon nitride (BaTiO 3 /xSi 3 N 4 ) powder (when x = 0, 0.1, 0.5, 1 and 3 wt%) were prepared by solid-state mixed-oxide method and sintered at 1400 8C for 2 h. X-ray diffraction result suggested that tetragonality (c/a) of the BaTiO 3 /xSi 3 N 4 ceramics increased with increasing content of Si 3 N 4 . Density and grain size of BaTiO 3 /xSi 3 N 4 ceramic were found to increase for small addition (i.e. 0.1 and 0.5 wt%) of Si 3 N 4 mainly due to the presence of liquid phase during sintering. BaTiO 3 ceramics containing such amount of Si 3 N 4 also showed improved dielectric and ferroelectric properties. #
Dielectric response on microwave sintered BaTiO 3 composite with Ni nanopowder and paste
Materials Research Bulletin
A B S T R A C T In this paper, barium titanate–nickel composite (BaTiO 3 –Ni) was synthesized using a sol–gel method and sintered by microwave furnace. Microwave sintering of BaTiO 3 –Ni (nanopowder and paste) was carried out at 1100 C for 20 min to get dense composites. XRD was performed to confirm the phases of BaTiO 3 and Ni. The morphologies of sintered BaTiO 3 –Ni using Ni nanopowder and paste were characterized by FE-SEM. Microwave sintered BaTiO 3 –Ni nanopowder showed dielectric response of e r $13,500 with tangent loss 0.04 at 10 kHz at room temperature being higher dielectric constant with less tangent loss as compared to BaTiO 3 –Ni paste. BaTiO 3 –Ni composites can not only be sintered densely at a lower temperature with rather shorter time, but also the grain growth can be suppressed by microwave sintering. ã
High density nanostructured BaTiO 3 ceramics obtained under extreme conditions
2012
High density nanostructured BaTiO 3 ceramics were synthesized by an innovative processing route, which involves high-energy ball milling and spark plasma sintering. Structural analyses showed only tetragonal (P4mm) single-phase samples. Ferroelectric measurements revealed a typical remnant polarization (3.7 lC cm À2) of nanostructured BaTiO 3 samples and a saturation polarization (20 lC cm À2) similar to that of BaTiO 3 single crystals. The potential application of nanostructured BaTiO 3 ceramics as multilayer capacitors was demonstrated by dielectric permittivity (e 0 = 3000, at 300 K and 1 kHz) measurements.
Structural, microstructural, dielectric and ferroelectric properties of BaTiO3-based ceramics
Processing and Application of Ceramics, 2019
(1-x)BaTiO 3-xCaCu 3 Ti 4 O 12 ceramic powders (where x = 0, 0.02, 0.04, 0.06, 0.08 and 1) were synthesized by solid state reaction method and sintered at up to 1250°C. Phase formation, elemental composition and microstructure of all the samples were investigated by XRD, EDX and FESEM, respectively. The BT-CCTO ceramic samples corresponding to x = 0.04 content showed the best dielectric properties. The improvement of dielectric properties was attributed to the presence of oxygen vacancies. Ferroelectricity was retained for CCTO content up to x = 0.06.
Effect of mechanical milling on the structural and dielectric properties of BaTiO3 powders
Micro & Nano Letters, 2015
Barium Titanate (BaTiO 3) is a well known ferroelectric material and widely used in electronic industries for the multi layer ceramic capacitor (MLCC). In the present study commercially available tetragonal BaTiO 3 (BT) powders were taken to study the size effect on structural and the dielectric properties of the BT ceramics during the high energy ball milling (0 to 110hrs). The same perovskite when kept under normal atmospheric condition after milling shows gradual increase of additional crystalline phase that occurred due to absorption of atmospheric CO 2 gas which is characterized as orthorhombic BaCO 3. The milled BT samples were characterized by X-ray diffraction and small angle X-ray scattering and dielectric analyzer. The purpose of the work was to study how the dielectric property of nano BaTiO 3 ceramics varies with reduction of particle size, structural changes and the absorption of carbon by this nano powders. It was observed that the dielectric constant of the BaTiO 3 powders increases with particle size reduction and the dielectric behavior of the BT ceramics significantly changes with polymorphic phase transformation in nano crystalline BaTiO 3 at different stages of milling while the capacitance significantly changes with the absorption of the carbon by the nano BT powders at humid atmosphere.