Journal of Electroceramics最新文献

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.

In this study, it is shown that since the distance of two adjacent inner electrodes of multilayer ceramic capacitors (MLCC) with high capacitance is close enough, the termination of the MLCCs can be made by direct plated Ni termination instead of by the existing dipped and cured Cu termination. The characteristics of termination MLCC made by direct nickel plating are characterized. Besides, Ni termination of MLCCs with high capacitance made by electroplating is shown to perfectly bond the electrodes to a nearly uniform surface with high adhesive strength. The inner and outer electrodes are made of the same nickel and the ohmic contact is very well shown, corresponding to excellent dielectric properties. The novel Ni termination of MLCCs with high capacitance made by electroplating is integrated with an inner Ni electrode at a low temperature process and shows the prefect performance of termination including an extreme low internal stress and much denser void free termination. This is completely different from the existing Cu termination connected with ceramic brick done by dipping at high temperature curing in a nitrogen atmosphere. Model analysis of electric field distribution and charge transport of electrochemical analysis were also performed for a better understanding of the electrodeposition process to make an Ni termination of MLCCs with high capacitance.

Spinel ferrites are among the most promising soft magnetic materials due to their superior coercivity, tailored band gap, high saturation magnetization, and other physical, thermal, and electrical characteristics. In the areas of cancer treatment, disease detection, magnetic resonance imaging, drug delivery, and release, soft ferrite nanoparticles (SFNPs) offer limitless potential. Ferrite nanoparticles are utilized in electronic domains to create sensors, biosensors, transducers, and transformers. Spinel ferrites are used in the treatment of wastewater, and they can be coupled with other nano materials for photocatalysis and adsorption. In this review, attention has been paid to the synthesis, distinctive characteristics, and various applications of spinel ferrites.

The pulsed electroacoustic (PEA) method is an established method for space charge measurements in polymeric dielectrics. In view of the poorly understood impact of space charge on the electrical resistivity and the dielectric breakdown behavior of ceramics, it is desirable to adapt the PEA technique to these materials. However, this adaption is non-trivial due to the constitutive properties of ceramics, which are, at least in part, very different from that of polymers. This contribution addresses a particular effect related to the electrostrictive properties of ceramics on the theoretical level. It is shown that these properties may cause an inversion of the sign of the sound wave generated by electrical voltage pulses when compared to typical polymers, which may in turn result in an incorrect interpretation of the measurement results. Using this finding, a reinterpretation of previous experimental results suggests that homo charge forms at the cathode in sheets of alumina ceramics subjected to high voltages.