Journal of Electroceramics最新文献

This work highlights the electrocaloric (EC) and energy storage (ES) properties of 1-x(0.6Ba(Zr_0.2Ti_0.8)O₃-0.4(Ba_0.7Ca_0.3)TiO₃)-x(BiTa_0.5La_0.5)O₃ (1-xBZCT-xBTL) ceramics with x = 0 to 0.05. The XRD studies revealed that inclusion of BTL content in BZCT does not induce any impurity phase. The peak splitting of BZCT near 2θ = 45(^circ) and 66(^circ) confirms the presence of morphotropic phase boundary corresponding to tetragonal and rhombohedral phases. Further, the solid solution formation of BZCT-BTL has suppressed its morphotropic phase boundary behaviour. The XRD, Raman and temperature dependent dielectric studies suggest the presence of pseudocubic phase in 1-xBZCT-xBTL at higher values of x = 0.025 and 0.05. Moreover, the inclusion of BTL boosts the diffused phase transition behaviour of BZCT ceramics. Further, BTL strengthened its relaxor nature due to a reduction in grain size as evidenced from SEM analysis. It is observed that the 0.99BZCT-0.01BTL ceramics show 95% efficiency and a maximum recoverable energy density of 479 mJ/cm³ at 100 kV/cm. Moreover, the electrocaloric temperature change and responsivity are found to be 1.06 K and 0.01 Kcm/kV near the transition temperature.

In this paper, the Ca²⁺ ion was chosen to substitute the Mg²⁺ ion of Li₂MgSiO₄ ceramics. Li₂Mg_1 − xCa_xSiO₄ (x = 0.0, 0.03, 0.06, 0.09, 0.12) ceramics materials were prepared by solid state reaction at low temperature (925 °C) with 2.5wt% Bi₂O₃ sintering aid. X-ray diffraction (XRD) results showed the ceramics presented the standard Lithium Magnesium Silicate phase formation, and no secondary phases appeared. Scanning electron microscopy (SEM) suggested that Ca²⁺ ions affected the densification of the prepared ceramics. Ca²⁺ ion substitution resulted in increasing relative density, enhancing microwave properties. Ca²⁺ ion substituted Mg²⁺ ion and formed a CaO4 structure, which affected microwave dielectric properties. With the substituted amount increase, the values of dielectric constant ε’ and quality factor Q×f gradually increased, and τ_f values increased from negative to positive values. When x = 0.09 and sintered at 925 °C, Ca²⁺ ion substitution gave ceramics excellent microwave properties: bulk density ρ = 2.479 g/cm³, relative density was 98.68%, dielectric constant ε’=6.59, dielectric loss tanδ_ε = 0.0018, quality factor Q×f = 8976.9 GHz and temperature coefficient τ_f = 1.9 ppm/°C. This ceramic material has excellent microwave dielectric properties and holds a potential for use in integrated antenna and other electronic devices.

The present research work aims to address the rising demand for microwave-absorbing materials (MAMs) due to the relentless growth of detrimental electromagnetic wave pollution. Herein, the absorption behavior of manganese-zirconium co-substituted zinc-cobalt spinel ferrites with chemical composition Zn_0.25Co_0.75(MnZr)_xFe_2−2xO₄ (0.05 ≤ x ≤ 0.25, ∆x = 0.05) were investigated in the Ku (12.4–18 GHz) and K (18-26.5 GHz) frequency bands. Samples of Mn-Zr-Zn-Co ferrites were successfully synthesized via the sol-gel citrate route with sintering at a temperature of 1000 °C for 6 h. Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of two vibrational peaks in the spinel lattice structure. The complex dielectric permittivity and complex magnetic permeability were measured using a vector network analyzer (VNA). The composition MZ 0.15 outperformed all the prepared compositions by exhibiting a minimum reflection loss of -34.55 dB at a matching frequency of 15.09 GHz and a matching thickness of 2.7 mm in Ku-band and a reflection loss as low as -30.40 dB at a matching frequency of 25.48 GHz and a matching thickness of 1.5 mm in K-band. The obtained results indicate that the fabricated specimens have the potential for designing efficient microwave-absorbing materials in the Ku and K frequency bands.

Synthesis of metal oxides is typically the first step of any materials science research in a field or application involving oxides materials. However, the synthesis is rarely the prime focus in materials science, which usually describe properties and characterizations of said materials. Consequently, synthesis protocols are often given too little attention in the literature and hence poorly described. For scientists starting in the field, it becomes confusing to make the right choice of synthesis route and conditions to successfully prepare what will be the base of their research, which is a pure, single phase, complex oxide powder. With this tutorial article, we are giving basic knowledge on the underlying chemistry of oxide synthesis, and simple explanations on what motivates the need of various synthesis routes. Then, four main synthesis routes are described, namely the solid state reaction route, the Pechini route, the combustion route, and the precipitation route. For each routes, the approach is described, and the relevant parameters to be considered are developed. Finally, a step by step general protocol for each route is proposed, which can serve as a solid foundation for unexperienced researchers to become more confident when approaching metal oxide synthesis.

In this work, phenolic resin (PR) -based carbon aerogel composites reinforced with aluminum silicate ceramic fibers were obtained using the conventional sol-gel method with the carbonization technique. The experiment results showed that carbon aerogel with stable morphology was obtained by drying the PR wet gel at room temperature. Reactant ratios affected the microstructure and overall performance of carbon aerogels. The overall discharge capacity of the obtained carbon aerogel specimens was maintained at 330 mAh g⁻¹ when the mass ratio of phenolic resin to curing agent was 8:1. The growth of aerogel particles was guided during the curing reaction. A three-dimensional network structure with ceramic fibers as the core was formed in PR/CF. The ceramic fibers suppressed the shrinkage of the samples, and the ceramic fibers improved the mechanical properties of the samples.

The ion diffusion phenomenon in ferroelectric-dielectric composite ceramics will deteriorate its dielectric properties. In this paper, Ba_0.5Sr_0.5TiO₃-CuGa₂O₄ composite ceramics were prepared at different sintering heating rates. The phase composition, microstructure and dielectric properties were tested and analyzed. The effects of grain growth and the different degrees of ion diffusion on the properties of ferroelectric-dielectric composite ceramics at various heating rates were studied. The results show two crystal phases including perovskite structure BST and spinel structure GuGa₂O₄ in the composite ceramics. With the increase of the heating rate, the dielectric permittivity decreased, the tunability showed a decreasing trend, and the Q value also appeared to decrease after a slight increase. The inhomogeneity of grain size is apparent when the heating rate is higher. Moreover, as the grain size heterogeneity increases, the density decreases, adversely affecting the dielectric property of the samples.

BaFe_0.5Ta_0.5O₃ceramics has been successfully prepared by a solid state reaction method and structural analysis revealed that single perovskite phase was obtained in the ceramic sample. Room temperature magnetodielectric and magnetoimpedance properties of ceramics were investigated. Variations in the dielectric permittivity, loss tangent and impedance were evident. This confirms that a room temperature magnetoelectric effect can be obtained in BaFe_0.5Ta_0.5O₃ ceramics. Also, a higher grain boundary contribution than a grain contribution in the magnetoelectric effect was confirmed. The magnetoelectric voltage response as a function of H_bias suggested a room temperature nonlinear magnetoelectric coupling in BaFe_0.5Ta_0.5O₃ ceramic.

Perovskite-type oxides (ABO₃) are potential alternatives as electrode materials for IT-SOFC. Their properties of electronic conduction, catalytic activity, and stability in oxidative and reductive atmospheres arouse this interest. Due to their electronic conduction properties, both LaNiO₃ perovskites, commonly used as a cathode, and LaCrO₃ perovskites, commonly used as interconnectors, can also be developed to be used as an anode. Thus, this work describes the results of experiments carried out on Cr-doped LaNiO₃ compositions aiming at their use as fuel cell anodes. The compositions of LaNi_1 − xCr_xO₃ (0 ≤ x ≤ 0.7) were synthesized by a modified Pechini method, and the effects of replacing Ni with Cr in LaNiO₃, mainly perovskite phase formation and structural stability, beyond microstructure and electrical properties were analyzed. Phases with a perovskite-like structure were obtained via calcination at 900 °C. For the sintered samples, it was observed that an increase in the amount of Cr led to an increase in porosity. The compositions with x = 0.7 and x = 0.5 sintered at 1300 and 1400 °C remained single-phase after sintering, while the composition x = 0.3 sintered at 1500 °C and the composition x = 0.0 sintered at 1250 °C decomposed into secondary phases. Concerning electrical properties, the activation energy values obtained were consistent with electronic conductivity, 0.03 eV, indicating p-type conduction in an oxidizing atmosphere.

The piezoelectric thick film of the active component that works at high temperatures for space and aeronautics has been in significant demand. The thick film has great technological importance as its thickness lies between the thin film and bulk material. The application, such as sensors and actuators, require a thickness that is not less than thin film or not more than bulk to be sufficiently powerful and sensitive. While the thick film is exposed to a temperature higher than room temperature, the piezoelectricity and elastic properties should not be degraded. Thus researchers have been investigating high-temperature thick films for the past decade. This review focuses on the detailed study of high-temperature piezoelectric thick films of lead-based and lead-free based materials and their composites, highlighting fabrication methods. Other important areas, such as substrates for thick film properties achieved and targeted applications, are also discussed. This discussion shows that selecting the high-temperature piezoelectric material, fabrication method, substrates, etc., are essential for fabricating a high-temperature piezoelectric transducer.