Journal of Electroceramics最新文献

We introduce a high surface area sensor composed of Co₃O₄ nanoparticles (NPs) embedded within porous ZnO nanofibers (NFs), exhibiting a notable response to acetone. Initially, we synthesized polyvinylpyrrolidone (PVP) NFs containing zinc and cobalt salts via a simple electrospinning method. Subsequently, the calcination of the PVP NFs resulted in the formation of Co₃O₄ NPs embedded within the porous ZnO NFs. The heterostructure material demonstrated a significant response to 100 ppm acetone detection, with a ratio of electrical resistance in air (R_a) to that in the presence of gas (R_g) reaching 111 at its optimal operating temperature of 275 °C. Furthermore, it exhibited stable performance under high relative humidity conditions.

This study investigates the microwave dielectric and shielding properties of MgTiO₃-based solid solutions across the K (18–26.5 GHz) and Ka (26.5–40 GHz) frequency bands. Synthesized via a conventional solid-state mixed oxide route using MgO and Mg(OH)₂ as raw materials, the dielectric properties of MgTiO₃ and Mg(Ti_0.95Sn_0.05)O₃ solid solutions varied with composition and raw material. Results showed that MgO-based materials exhibited higher relative permittivity (ɛ_r) and loss tangent (tan δ) compared to Mg(OH)₂-based materials. Furthermore, the ɛ_r of the prepared samples decreased with Sn⁴⁺ substitution, attributed to the lower dielectric polarizability of Sn⁴⁺ cations compared to Ti⁴⁺ cations. Results also indicated a decrease in tan δ with Sn⁴⁺ substitution, resulting from a reduction in octahedral tilting upon partial replacement of Ti⁴⁺ cations with Sn⁴⁺ cations in MgTiO₃. Shielding property characterization revealed that all samples exhibited frequency-selective and tunable shielding capabilities, with tuning achievable through variations in composition or shield thickness. Notably, in the K frequency band, MgO-based MgTiO₃ exhibited superior dielectric properties, with a sample thickness of 2.9 mm achieving a shielding effectiveness (SE) of up to 35.62 dB at 22.30 GHz, effectively suppressing over 99.97% of incoming radiation. Similarly, in the Ka frequency band, MgO-based Mg(Ti_0.95Sn_0.05)O₃ demonstrated remarkable SE, with a sample thickness of 1.8 mm reaching SE of 38.62 dB at 31.60 GHz, attenuating over 99.98% of incoming radiation. These findings suggest potential for frequency-selective and adjustable EMI shielding in next-gen technologies.

Raw materials were etched by nitric acid to release utterly carbon dioxide. An excess of citric acid was then employed as fuel to prime the combustion reaction for the synthesis of Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ (x = 0 (SrBi₂Nb₂O₉), 0.1, and 0.2) compounds. X-ray diffraction, Fourier-transformed infrared, and Raman techniques revealed quite certain that there is a link between dopant amounts and structural changes. One is that the cell volume was smoothly reduced. Second, the bond force constant decreased slightly when the dopant was introduced into the lattice. Even though the SrBi₂Nb₂O₉ compound is not only doped by samarium but also by barium, samarium is the only dopant that affects dielectric and electrical properties. Doping with samarium enhances the dielectric constant at room temperature by reducing the Curie temperature, and it turns ferroelectric normal into relaxor behavior. The results of AC conductivity and electrical modulus laid out that one extreme defect was that a significant amount of cation exchange occurs in Sr_0.95Ba_0.05Bi_2−xSm_xNb₂O₉ samples and a large amount of oxygen vacancies were released. Overlapping large polaron tunneling model (OLPT) mechanisms was the adequate model for these compounds.

Cerium dioxide (CeO₂) finds extensive utility in electro ceramics applications, including solid oxide fuel cells, oxygen sensors, and catalysts. However, Spark Plasma Sintering (SPS) of CeO₂ presents challenges due to the increased mobility of O²⁻ ions in the presence of an electric field, as well as its reactivity with graphite tooling. Traditionally, CeO₂ is sintered in an oxidative environment to prevent it from reducing to CeO_2−δ or Ce₂O₃. Nevertheless, oxidative atmospheres are detrimental to the graphite and steel tooling used in SPS processing. In this study, we investigated CeO₂ SPS in a CO₂ atmosphere and observed slight increase in the relative density (RD) of the as-sintered samples in comparison to those sintered in an Ar atmosphere. The improved densification is attributed to reduced formation of oxygen vacancies in the CO₂ atmosphere. Furthermore, the reaction between CeO₂ and graphite generates CO_x gases, and that reaction can be reversed in a CO₂ atmosphere. In summary, CeO₂ SPS in a CO₂ environment demonstrates superior densification, effectively mitigating the challenges associated with ionic mobility and graphite reactivity.

Over the years, there has been a relentless approach to manufacturing magnetic materials with a required magnetism whereby they could be tuned for a specific purpose such that there can be a lot of scope for pumping in new materials of technological importance. Because of its innovative uses in spintronic devices, titanate-based magnetic materials have received a lot of scientific as well as pioneering research recognition. Ba_0.6Cd_0.4TiO₃ micro rods have been prepared in the current experimental study using the simple sol-gel technique. Ba_0.6Cd_0.4TiO₃ has a rod-like morphology with a diameter of around 404–744 nm and a lattice strain (ϵ) of 5.4 × 10^− 4 and dislocation density (δ) of 1.34 × 10¹⁴ m^− 2, as seen by the W-H plot constructed from the XRD data. XPS analysis clearly indicates that the relatively small ferromagnetism perceived in Ba_0.6Cd_0.4TiO₃ is caused by Ba defects or Ti³⁺ ions. Using the absorbance spectrum, the value of 3.18 eV is computed as the optical band gap. A low saturation magnetization, M_s = 3.58 × 10^− 3 emu/g, a remanence, M_r = 2.72 × 10^− 4 emu/g, and a coercivity, H_c = 122.45 Oe are additional characteristics observed for the micro rods in room-temperature ferromagnetism (RTFM). The RTFM observed in this study suggests that the synthesized microrods would be suitable for utilization in the developing field of spintronic devices.

Serious structural irreversibility and interfacial side reactions pose major challenges for the stable operation of LiCoO₂ cathodes at high voltages. Herein, we report a polymer-based solid electrolyte (SLP) composed succinonitrile, LiTFSI and PVDF as a binder to address these issues. The SLP binder exhibits superior performance compared to traditional PVDF and PVDF binders with LiTFSI, with higher ionic conductivity (8.46 × 10^− 5 S cm^− 1 at 30 ℃), lower activation energy of 0.38 eV and excellent adhesion. Even with just 3% SLP binder, LiCoO₂ cathode operating at a cutoff voltage of 4.6 V and loaded with ~ 6.0 mg cm^− 2 active material demonstrates improved rate capability at higher compaction densities, delivering a discharge specific capacity of 146.5 mAh g^− 1 after 100 cycles at 0.5 C-rate. The SLP binder not only enhances Li⁺ conduction but also facilitates the formation of a stable cathode-electrolyte interphase, thus reducing the Li⁺ diffusion barrier and interface polarization, and enhancing battery’s performance at low temperature. Furthermore, the SPL binder’s high compatibility and elasticity with the electrolyte mitigate irreversible structural changes and volume expansion in LiCoO₂ during cycling, leading to better preservation of the layered structure and lower internal stress for stable cycling under high temperatures. This strategy provides a novel interface protection idea for electroceramic cathode materials and may facilitate commercial development.

In this study, the relationship between core electron energy band changes and chemical changes occurring at the site of positron annihilation in BaTiO₃(BTO) doped by different amounts of metallic element Eu was investigated by Coincidence Doppler broadening spectroscopy. The reduction of the background spectrum caused by a simultaneous detection system in Doppler broadening spectroscopy makes it possible to investigate the contribution of high-momentum core electrons in the process of positron annihilation in the BTO: Eu structure. The results obtained from the spectrum in the range of momenta up to 15 × 10^− 3 m₀c show that with increasing Eu, the contribution of valence electrons in the process of positron annihilation increases, but at higher momenta of the sample containing 0.05 europium compared to the samples containing 0.01 and 0.03% impurity, a higher contribution in the ratio curve in the annihilation process was observed.

In this work, nano ZnO powders, Bi₂O₃, Sb₂O₃, Cr₂O₃, Co₂O₃ and a various content of MnO₂ were blended thoroughly and pre-calcined at 800℃ and then pressed in to pellets which were sintered at 950℃ to form varistor ceramics. Subsequently, the effects of MnO₂ on the microstructure and electrical properties of the ZnO-based varistor were investigated. It was found that the amount of spinel phase (Zn₇Sb₂O₁₂) and Bi₂O₃ phase increased with the MnO₂ increasing, while the content of pyrochlore (Zn₂Bi₃Sb₃O₁₄) phase decreased. As a result, the growth of ZnO grain was reduced with the average grain size from 9.5 μm down to 5.3 μm, leading to the increase of breakdown field of ZnO-based varistor. Particularly, the ZnO-based varistor with 1.2 mol% MnO₂ exhibited the best comprehensive electrical performance with the breakdown field E_b of 901.4 V/mm, the nonlinear coefficient α of 66.7 and the leakage current density J_L of 1.1 µA/cm².

ZnO-B₂O₃-SiO₂/SiO₂ glass-ceramic composites are prepared by solid phase reaction method. The DSC curve of ZnO-B₂O₃-SiO₂ glass is analyzed and the effects of ZnO-B₂O₃-SiO₂ glass on the density, microwave dielectric properties, phase composition and microstructure of ceramic fillings are investigated. The results show that the sintering temperature of the composites can be reduced to 910 °C by adding ZBS glass. When the addition of ZBS is 65% (wt%), the dielectric properties of the sample are best when the composite is sintered in 910 °C for 1 h (εr = 4.6, tanδ = 4.85 × 10^− 4 at 9.2 GHz, τ_f = -13.78 ppm/°C). The prepared ZnO-B₂O₃-SiO₂/SiO₂ composite is promising candidates for LTCC applications.