Journal of Electroceramics最新文献

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.

This research study explores the magnetic and magnetocaloric properties of La_0.67-xEu_xBa_0.33Mn_0.85Fe_0.15O₃ (x = 0 and 0.1) magnetic compounds elaborated using the Sol–Gel method, based on a phenomenological approach proposed by Mahmoud Aly Hamad. The studied compounds exhibit a second-order ferromagnetic (FM) to paramagnetic (PM) transition with increasing temperature. A correlation between the experimental measurements and the theoretical analysis is established. Indeed, the value of the magnetocaloric effect was determined from the theoretical model based on magnetization as a function of temperature at several magnetic fields. Under an applied magnetic field of 5T, the absolute values of the maximum magnetic entropy change are evaluated at 0.92 and 0.60 J kg⁻¹ K⁻¹ for x = 0 and 0.1 respectively. This reduction may be attributed to a Curie temperature distribution implying also a decrease in the relative cooling power (RCP). The RCP and the specific heat capacity values are also estimated thanks to this model. The results predicted by this model allow us to propose these compounds as promising candidates for magnetic refrigeration.

Piezoelectric ceramics, as an essential electronic material, are widely used in various actuators and ultrasonic transducers. In this study, piezoceramics in the formula Pb_0.94Sr_0.04Ba_0.02(Mg_1/3Nb_2/3)_0.025(Sb_1/2Nb_1/2)_0.025(Ni_1/3Nb_2/3)_x(Zr_0.48Ti_0.52)_0.95−xO₃ + 0.2wt%Li₂CO₃, where x = 0.21 − 0.17(abbreviated as PMN-PSN-xPNN-(0.95-x)PZT) were investigated. By changing the PNN content from 0.21 to 0.17, high piezoelectric coefficient d₃₃ from 860 pC/N to 700 pC/N, high Curie temperature T_c from 137 ℃ to 168 ℃ were obtained. All the ceramics show excellent electrical properties. It is 15 − 20% better than PNN-PZT or doped PNN-PZT piezoelectric ceramics in certain aspects. What’s more, the ceramics also carry extraordinary electromechanical coupling factor k_p (from 67 to 73%). Hence, this is an excellent candidate for actuators and transducers applications.

The fatigue behavior of Bi_0.5Na_0.4K_0.1TiO₃-based ceramics depends on the polarity. While the non-ergodic relaxor ceramics have large residual polarization but poor fatigue behavior, the ergodic relaxor ceramics have excellent fatigue resistance but tiny residual polarization. Therefore, obtaining ferroelectric ceramics with high residual polarization and excellent fatigue resistance is challenging due to the trade-off between non-ergodic relaxor and ergodic relaxor. Here, we modulate the free energy barrier by doping relaxant Nb to achieve the coexistence of non-ergodic and ergodic relaxor phases. At 0.6% Nb doping, the residual polarization is large at 2P_r = 49.3 µC/cm², increased to 54.23 µC/cm² after 10² cycles and decreased to 53.04 µC/cm² after 10⁵ cycles, indicating good fatigue resistance behavior. The large residual polarization is due to the metastable ferroelectric state, while the excellent fatigue resistance may be attributed to the field-induced ferroelectric-relaxor phase transition.

(Bi_0.5La_0.5)FeO₃ Orthoferrite ceramics were prepared by a conventional solid-state reaction method on a bulk scale and on a nano range by sol–gel auto combustion and Hydrothermal methods, respectively. The phase purity and crystallinity of the prepared ceramics have been examined by X–ray diffraction study. Broadening of the maximum intensity peak (hkl) and smaller crystallite size has been noticed in both chemical methods i.e., sol–gel and hydrothermal. Rietveld refinement confirmed the presence of orthorhombic symmetry with a space group (Pnma) for the ceramics synthesized through all three processes. The crystallite size, particle morphology, and grain microstructure formation mechanism were correlated for prepared ceramics with FESEM and XRD results. The influence of synthesis conditions on structure, microstructure, and magnetic studies has been studied. The M-H hysteresis loop study reflects that tuning of particles or crystallite size might induce a productive enhancement in magnetization response for chemically synthesized ceramics.