To produce a fine BaTiO microstructure3High density, high purity, stoichiometric and well distributed BaTiO ceramics.3Powder with an average grain size of 13 nm of cubic symmetry was prepared by a modified sol-gel method using hydroxide and alcoholate as precursors. The powders were hot pressed under vacuum at 1050-1150°C and an aniaxial pressure of about 30 MPa. For electrical measurements, a conductive silver paste was applied and bent at 600°C for 30 minutes. The ceramic density was measured
results and discussion
It is difficult to produce sufficiently dense ceramics with superfine grain size, because large deformations occur during the transition of the sample from cubic to tetragonal structure, which often lead to the collapse of the sediment. At the same time, the specific surface energy increases sharply with decreasing grain size and then leads to irregular growth with increasing sintering temperature. In order to obtain fine-grained samples with high density, many influencing factors must be thoroughly investigated,
The dielectric properties of barium titanate ceramics were measured by changing the grain size between 280 nm and 1.8 μm. Observations confirmed that the dielectric properties depend on grain size. A diffuse phase transition was observed when the grain size was reduced to 280 nm. In the 280 nm sample, high dielectric constant values and low dissipation factors were observed that cannot be explained by previous theories. A part of the grains showing a tetragonal structure is considered to be the
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The influence of filler permittivity on the dielectric properties of polymer-based composites
2022, Composites Science and Technology
Polymer dielectrics promise a high breakdown gain (Eb) and a low dielectric loss (Dl), but have a low permittivity (ε). The addition of a high-ε filler to the polymer is an important strategy to greatly decrease Eb and increase Dl at the same time. Lower-ε fillings could allow higher Eb and lower Dl by removing high electric field. However, this conclusion remains open due to many experimental interferences, such as B. the interface, the filler morphology and the polymer crystallization, controversial. Here, to study the influence of ε-filling systematically, nanoparticles (silica, alumina, barium titanate) with different ε are selected and surface-treated in a similar way to produce polypropylene composites. The morphology of the filler, the chemistry of the surface of the filler, the dispersion and the crystallization of the polymer are also controlled. The ε of compounds increases with ε-filling since high ε-filling contributes to higher filler polarization. Filled compounds with high ε-filling and medium ε-filling can be described by the Jaysundere-Smith model, while filled compounds with low ε-filling are higher than the models because the influence of interface polarization for the padding of low ε is evident . The DI of composites shows no relation to ε-filling since the intrinsic DI of the filler is irrelevant to ε-filling, whereas interface defects induce a similar degree of interfacial loss independent of ε-filling change. The Eb of the composite shows little relevance for the filling ε. Only if the filling ε is very low, Eb can be partially strengthened thanks to the weakened electric field. This work provides fundamental insight into the mechanism of the permittivity of fillers and provides guidelines for the selection of dielectric fillers.
Electrical characterization related to the microstructure and morphology and dielectric relaxation studies of Sb
2The 3nanocrystalline synthesized by mechanical alloying
2022, Materials Science and Engineering B: Solid State Materials for Advanced Technology
In this article, a fast and simple mechanical alloying method for synthesizing nanocrystalline Sb is explored.2Is3at room temperature with the least number of ingredients under an inert atmosphere. XRD, FESEM and TEM have characterized the structure and microstructure. The rhombohedron Sb2Is3Phase formation was checked after 3 hours milling without any contamination. The FTIR spectra show a minimal size-dependent band gap. The ionic conductivities measured in the temperature range from 300 to 473 K increase with increasing temperature and confirm the semi-metallic character of the samples. Analysis of impedance spectra reveals the electrical relaxation process and temperature-dependent transport properties. The non-Debye behavior is confirmed by the Cole-Cole diagram. The frequency-dependent AC conductivity follows Jonscher's universal power law, and a small polaron transaction is used to explain the temperature dependence of the frequency exponent. A reduced value of the dissipation factor at higher frequencies makes the material usable at higher frequencies.
Dielectric and mechanical properties of hypersonic radome materials and metamaterial design: a review
2022, Journal of the European Ceramic Society
This review article examines ten current radome ceramic materials in research and development and provides a comprehensive overview of the high-temperature and high-frequency data available from the literature. An overview of metamaterials for transparent high-frequency radomes is given and our preliminary experimental results of a high-temperature metamaterial design are presented. The radome temperatures of next-generation hypersonic vehicles will exceed 1000°C and speeds will exceed Mach 5. An ideal radome material has high flexural strength, low dielectric constant and low tangent loss, and high resistance to thermal shock and corrosion. The microstructural influence on the dielectric and mechanical properties as well as the impact of environmental factors such as rain are discussed. The influence of the metamaterial structure on important radome factors such as misalignment, gain and polarization is investigated. After examining the benefits associated with using metamaterials, our preliminary results for a possible high-temperature metamaterial design are presented.
Synthesis of (La + Nb)TiO rutile nanoparticles
2co-doped and dielectric properties of their derived ceramics composed of submicron grains
2021, International Ceramics
In this work, a sol-gel method was used to synthesize nanometer-sized rutile (La+Nb) co-doped TiO.2Powders used to prepare co-doped (La+Nb)TiO2pottery. The mean grain size of (La+Nb) co-doped TiO2The ceramic had a thickness of less than 200 nm, which is much smaller than that of conventionally produced co-doped TiO2Ceramics, which generally have micron-sized grains. The influence of the Co doping concentration (La+Nb) on the microstructures and dielectric properties of the obtained ceramics was studied in detail. At a co-doping concentration of 2%, TiO was found to be co-doped with (La+Nb).2The ceramic had a dielectric permittivity (εʹ) greater than 2 × 104for frequencies up to 1MHz and the lowest dielectric loss (tanδ) was 0.019 at 1kHz. Electron hopping and the electron-anchored defect dipole effect were thought to be the main reasons for the colossal permittivity and the low tanδ. This work provides a technique for the synthesis of co-doped TiO2Nanoparticles and co-doped TiO preparation with submicron grain size2Ceramic with good dielectric properties.
Correlation between multifunctional properties of lead-free iron-doped BCT perovskite ceramic
2020, International Ceramics
This decrease in εʹ in Tc is due to the increase in compositional perturbation with increasing doping, leading to perturbation of the ferroelectric order over long distances . In addition, the decrease in εʹ in Tc could be related to the decrease in grain size and increase in grain boundaries (as observed in SEM studies), enhancing the depolarization effect [37,38]. It can also be observed in Fig. 5 that the transition temperature (Tc) decreases with increasing Fe doping in the BCT ceramics investigated.
The present study investigates the effect of Fe doping on the structural, microstructural, dielectric, ferroelectric, piezoelectric, and magnetic properties of barium calcium titanate (BCT) ceramics synthesized via the solid-state reaction pathway. The polycrystalline tetragonal structure of the ceramic produced was confirmed by the XRD study. The analysis performed with the Rietveld refinement shows a reduction in the lattice parameters as well as the volume of the unit cell in the replacementFe3+Ions in the BCT lattice. Appearance of four different Raman bandsnamely.. 297cm−1-302cm−1, 473cm−1-475cm−1, 516cm−1-524cm−1y 729cm−1-733cm−1in Raman spectroscopic studies confirms the tetragonal phase of the prepared ceramic compositions, consistent with the XRD study. Scanning electron microscopic analysis revealed polyhedrally shaped grains, the average grain size of which decreased with increasing sizeFeContent (x) in BCT ceramics. A phase transition independent of the diffuse frequency was observed in the temperature-dependent dielectric measurements. The dielectric properties improved significantly with changing transition temperature TCnear room temperature withFeDoping These studies point to applications of these ceramics in the development of green dielectric materials that meet the X7R MLCC specifications. It has been found that the ferroelectric and piezoelectric properties of these ceramic compositions decrease with increasing temperature.FeConcentration. Weak ferromagnetism was observed at room temperature for the composition x=0.020.
Influence of spark plasma sintering temperature on microstructures, dielectric and I-V properties of CaCu ceramics
3Von 4Ö 12
2020, Alloys and Composites Magazine
our3Von4Ö12(CCTO) ceramics were manufactured using the sol-gel process and sintered at different temperatures using the spark plasma sintering (SPS) process. The temperature of the SPS process has an important influence on the microtopography of CCTO ceramics. The results of EDS and positron annihilation spectroscopy indicate that Cu2+During the high-temperature sintering process, it diffuses from the inside to the surface of the grains. The permittivity (miR) of the CCTO ceramic at the corresponding frequencies increases with increasing SPS temperature. However, the frequency stability ofmiRover the frequency range 40-106Hz gradually decreases. CCTO ceramics sintered at 900 °C and 950 °C have very low dielectric loss values (approx. 0.02) near 10 kHz. the change inmiRand tanδ for the CCTO ceramic can be explained by the internal barrier layer capacitance (IBLC) model and AC (alternating current) impedance spectra. The results ofI-VThe non-linear properties of the CCTO ceramic make it clear that the height of the potential barrier has a positive effect on the value of the non-linear coefficient.
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Structure, electrical and dielectric properties of Ca-substituted BaTiO3 ceramics
Ceramics International, Band 44, Ausgabe 10, 2018, S. 11109-11115
BaTi1xCaliforniaXÖ3xCeramic [BTC100x] was synthesized by the solid state reaction method. The influence of Ca substitution on the structure, electrical and dielectric properties of the BTC100x ceramic was systematically investigated. Calcined BTC100x powders were in the tetragonal phase at x≤0.01, whereas they became cubic at x>0.01. Furthermore, the diffraction peak (200) shifted to smaller angles with increasing x, indicating an increase in unit cell volume. In the meantime, Ba0,97California0,03TiO3[BC3T] ceramics were fabricated and studied to compare with BaTi0,97California0,03Ö2,97(BTC3). It was found that pure BaTiO3[BT] and BC3T ceramics had similar structural and dielectric properties, while BTC3 ceramics showed major differences. XRD patterns, Raman spectra, impedance spectra, and dielectric temperature spectra provided strong evidence for Ca2+Replacement at Ti location on BT network. Finally, BTC100x ceramics were manufactured and the dielectric properties were investigated. As x increased, the Curie temperature decreased from 128 °C (BT) to 42 °C (BTC5).
Dielectric properties of donor-acceptor modified BaTiO3 ceramics
Ceramics International, Band 42, Nummer 10, 2016, S. 11692-11699
Sm/Mn-encoded BaTiO3Ceramics were studied for their microstructure and dielectric properties. Powders were prepared using the conventional solid state method. S m concentration2Ö3As a donor dopant, the percentage is 0.1 to 5.0%. MnO content2as an acceptor, it remained constant at 0.05% for Mn in all samples. The samples were sintered at 1290°C, 1320°C and 1350°C for two hours in an air atmosphere.
In lightly doped samples, a predominantly smooth and homogeneous microstructure with an average grain size in the range of 0.3 µm to 2.0 µm was observed. In addition to the fine-grained matrix, the occurrence of local areas with abnormal secondary grains was observed in highly doped samples.
The dielectric properties were examined as a function of frequency and temperature. The lightly doped samples exhibit the highest dielectric permittivity value at room temperature and the largest change in Curie temperature. The highest value of the dielectric constant (miR=6800) was measured for 0.1 Sm/BaTiO3Samples sintered at 1350°C. A nearly flat permittivity-temperature response and lower values ofmiRthey were obtained in samples with 2.0 and 5.0% additive content. The dielectric constant increases with increasing sintering temperature. The loss factor was between 0.01 and 0.22 and decreases with increasing sintering temperature. Curie's constant (C), Curie-Weiss temperature (T0) and non-linearity-critical exponent (C )were calculated using a modified Curie-Weiss and Curie-Weiss law. The highest value of the Curie constant (C=9.06 105K) was measured in samples doped with 0.1% at. The Curie constant decreased with increasing dopant content. HeCThe values ranging from 1.001 to 1.58 indicate the sharp phase transition in lightly doped samples and the diffuse phase transition in heavily doped BaTiO.3rehearse
Effects of ZnO-B2O3-Bi2O3 additive of different particle sizes on the dielectric properties and microstructure of BaTiO3-based X8R ceramics
Ceramics International, Band 44, Ausgabe 1, 2018, S. 894-899
In this work the sintering temperature of BaTiO should be lowered3Ceramic based while maintaining excellent dielectric properties, submicron and nanometer ZnO-B2Ö3-Bi2Ö3(ZBB) were co-doped to fabricate medium-temperature (1150°C) BaTiO3-based ceramics. The concerted mechanism on the dielectric properties of different fractions of the submicron and nanometer ZBB additive in BaTiO3X8R-based ceramics have been systematically studied. Complex impedance spectra and activation energies calculated from the grain boundary results revealed a diffuse nanometer-scale additive excess in the BaTiO lattice.3, resulting in poor dielectric properties and low density. Resulting BaTiO3The co-doped submicron additive and the ceramic-based nanometer ceramic-based additive in a 2 to 1 ratio showed sufficient relative density and ideal X8R performance with high dielectric constant (ε).R= 3460 at 1 kHz and room temperature) low dielectric loss tanδ < 1.1%, which offers a wide application perspective in electromagnetic interference filter.See AlsoVaihtoehtojen kehittäminen mukautuvalle metsätaloudelle: Pinus-lajin puiden kasvun harvennus- ja kuivuuskestävyys korkealla rinteellä Etelä-EspanjassaMetsärakenne ja puulajien monimuotoisuus maailmanlaajuisesti merkittävän biologisen monimuotoisuuden Abasumba-alueella, GhanaParkinsonin tauti: biokemiallinen reitti, joka sopii kaikkiin geeneihin?
Production, structure and frequency-dependent electrical and dielectric properties of Sr-doped BaTiO3 ceramics
Ceramics International, Band 46, Ausgabe 2, 2020, S. 2238-2246
Lead-free strontium-doped ferroelectric ceramics having the compositional formula Ba1xSeñorXTiO3(barium strontium titanate, BST) at (x=0, 0.25, 0.3, and 0.35) are efficiently synthesized by a solid state reaction. The prepared samples are characterized by X-ray diffraction (XRD) and Raman spectroscopy. Other dielectric properties and impedance are studied in detail. XRD and Raman studies show that the lattice constant, unit cell volume, and tetragonality ratio change with Sr concentration and Curie temperature (TC), and the dielectric constant decreases along with the dissipation factor with increasing Sr2+ions in BST. A stable dielectric constant is recorded over a wide frequency range from 1 to 1000 kHz. The Curie-Weiss law and theoretical estimates indicate a large difference in the structural disorder of BaTiO3(Barium Titanate, BT) Ceramic. Depending on the applied temperature and frequency, a noticeable change in the dielectric constant and dissipation factor behavior is observed between lightly and heavily doped BT samples. The diffusivity decreases with increasing Sr2+Amount up to x=0.3. The relaxation response in BST ceramics is observed for higher x values. Impedance spectroscopy shows that oxygen vacancies (OVs) are responsible for conduction in BST ceramics. This study is a systematic investigation of the relationship between the structure, dielectric, and impedance properties of Sr.2+BT ceramic replaced.
Influence of the Ba/Ti ratio on the magnetic properties of BaTiO3 ceramics
Void, Band 159, 2019, S. 374-378
BATTLE IN BIG3Ceramics are prepared by solid-state reaction, varying the Ba/Ti ratio from 0.990 to 1.005 in steps of 0.005 to study the influence of the Ba/Ti ratio on the origin of ferromagnetism in the diamagnetic material. The structural investigation confirmed the coexistence of the structural model of two phases, tetragonal (P4mm) + orthorhombic (Amm2), using the Rietveld refinement program. For the first time, the structural defect of Ti vacancies is quantified by refinement while Ba and O are fully filled. Magnetic M-H measurements at room temperature have shown that diamagnetic and ferromagnetic loops are present in Ti-rich and Ti-poor BaTiO3The ferromagnetic behavior (Ti deficiency) is due to the intrinsic defect, namely the Ti vacancy, which plays a crucial role in the magnetic properties of the otherwise diamagnetic BaTiO.3pottery. The magneto-dielectric constant is negligible in Ti-rich samples, while a high magneto-dielectric constant value of -0.88% at 0.8 T is obtained in the Ba/Ti=1.005 sample.
Direct and inverse piezoelectric grain size effects on BaTiO3 ceramics with different Ba/Ti ratios
Journal of the European Ceramic Society, Band 38, Nummer 12, 2018, S. 4212-4219
The grain size effects of the direct piezoelectric coefficient (i.e33) and the inverse piezoelectric coefficient (i.e33*) from BaTiO3Ceramics with different Ba/Ti ratios have been systematically investigated. It was found that both33yd33* showed strong dependencies on grain size (g) for BaTiO3Ceramics with different Ba/Ti ratios. although d33showed a similar grain size dependence for all Ba/Ti ratios, except for a slight change in the critical grain size from 1 μm to 3 μm, two completely different grain size dependences of d33* were observed. By carefully studying the microstructure and ferroelectric properties of the ceramic, the variations in domain configurations, and the maximum polarization of BaTiO3Ceramics with different Ba/Ti ratios were thought to be responsible for the different grain size dependence of d33yd33*, or.
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