Influence of size on the dielectric properties of fine-grain BaTiO3 ceramics (2023)

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.

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.

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.

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.

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 T_Cnear 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.

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 (mi_R) of the CCTO ceramic at the corresponding frequencies increases with increasing SPS temperature. However, the frequency stability ofmi_Rover 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 inmi_Rand 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.

Ceramics International, Band 44, Ausgabe 10, 2018, S. 11109-11115

BaTi_1xCalifornia_XÖ_3xCeramic [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, Ba_0,97California_0,03TiO₃[BC3T] ceramics were fabricated and studied to compare with BaTi_0,97California_0,03Ö_2,97(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).

Ceramics International, Band 42, Nummer 10, 2016, S. 11692-11699

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.

Ceramics International, Band 46, Ausgabe 2, 2020, S. 2238-2246

Lead-free strontium-doped ferroelectric ceramics having the compositional formula Ba_1xSeñor_XTiO₃(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 (T_C), 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.

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.

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.