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Lead-free Ag <sub/> 1-3 <i>x</i> </sub> La <sub/><i>x</i> </sub> NbO <sub/>3</sub> Antiferroelectric Ceramics with High Energy Storage Density and Efficiency
摘要： Environmentally benign lead-free bulk ceramics with high recoverable energy density (Wrec) are very attractive in advanced pulsed power capacitors. In this work, composition engineering was adopted by La3+ modification to improve the energy storage performance of Ag1-3xLaxNbO3 ceramics. It was found the antiferroelectric (AFE) phase was stabilized after La3+ substitution, as a result of the reduced tolerance factor t. Significant improvement of Wrec and energy storage efficiency (η) were achieved with value of 3.12 J/cm3 and 0.63 for x=0.02 at an electric field of 230 kV/cm, more than 1.5 times the value of pure AgNbO3 (Wrec=1.9 J/cm3, η=0.40). The excellent energy storage properties are resulted from the increased antiferroelectric-ferroelectric phase transition electric field (EF), ferroelectric-antiferroelectric phase transition electric field (EA) and breakdown electric field (Eb). The enhanced Eb was ascribed to the decreased grain size and increased electrical resistivity upon La3+ modification. The feature makes Ag1-3xLaxNbO3 a potential candidate for energy storage applications.
关键词： energy storage,ferroelectricity/ferroelectric materials,lead-free ceramics,dielectric materials/properties
更新于2025-09-23 15:22:29
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Giant Dielectric Constant and Tunable Phase-Transition Characteristics of ZnF <sub/>2</sub> /BaF <sub/>2</sub> -Modified BaTiO <sub/>3</sub> Thick Films
摘要： High performance capacitors have been investigated to meet higher integration density with optimized charge-storing capability. Here we introduce nonconventional thick film dielectric compositions based on 95BaTiO3-xZnF2-(2-x)BaF2-3glass (x=0.5, 1.0 and 1.5) where the relative content of ZnF2/BaF2 is critical in controlling dielectric behavior. The thick films were prepared on Cu foils by regular screen-printing and then firing at 950oC in inert atmosphere. As an optimal example, thick film composition modified with 1.0ZnF2/1.0BaF2 exhibited a dielectric constant of ~1,903 and a dielectric loss of ~0.04 at 1 MHz with dispersive dielectric relaxation behavior, which are far better than any reported corresponding values so far. Particularly, it was very interesting to observe that Curie Temperature was tunable from -19 oC to +34 oC, depending on the relative content of fluoride additives only within the 2 mol% range. Dependency of the relative contents of the fluorides is primarily investigated in regard to microstructure and dielectric properties.
关键词： dielectric materials/properties,printing,titanates
更新于2025-09-23 15:21:01
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Deficient or excessive CuO-TiO <sub/>2</sub> phase influence on dielectric properties of CaCu <sub/>3</sub> Ti <sub/>4</sub> O <sub/>12</sub> ceramics
摘要： The influence of the CuO–TiO2 phase (CT) on dielectric properties of the CCTO ceramic was investigated. CaCuXTiYO12 (CCXTYO) powders were prepared based on the coprecipitated method, where 2.70 ≤ x ≤ 3.30 and 3.25 ≤ y ≤ 4.75. XRD patterns confirmed the presence of CCTO and also the secondary phases as CuO, TiO2 and CaTiO3 for each sample and aided in its quantification. Scanning Electron Microscopy (SEM) shows secondary phases evolution in the grain boundaries, and its influence on size and morphology of the grains. Impedance spectroscopy measurements showed that the ceramics with lower amount of CuO and TiO2 phases (CT/deficient ceramics) exhibited the highest ?′ values (2.1x104 at 1kHz for CC2.9T3.75O ceramic). Also, CT/deficient ceramics showed lower tanδ values (0.090 at 1kHz for CC2.9T3.75O ceramic) than ceramics prepared with excessive CuO–TiO2 phase (0.241 at 1kHz for CC3.1T4.25O ceramics). The deficiency of CuO and TiO2 phases associated with high percentage of CCTO and CaTiO3 phases resulted in ceramics with the higher ?′ values.
关键词： CaCu3Ti4O12,titanates,dielectric materials properties,microstructure
更新于2025-09-10 09:29:36
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Structure development and dielectric properties of Zn-doped Pb([Mg,Fe],W)O <sub/>3</sub> perovskite ceramics
摘要： Ceramic samples of a pseudo-binary system Pb(Mg1/2W1/2)O3-Pb(Fe2/3W1/3)O3 (PMW-PFW) were prepared by solid-state reaction. In addition, their compositions were modified by 20 mol% Pb(Zn1/2W1/2)O3 (PZW) doping in order to investigate the role of zinc in the perovskite formation and dielectric properties. The perovskite contents were ≥95.1% at the overall composition range, except for a significantly low value of 79.0% at 0.8PFW-0.2PZW. The extension of sintering time for PMW accelerated superstructure formation, resulting in the ordering factor increased up to 0.40 after 12 h heat treatment. The maximum dielectric constant values increased with increasing PFW fractions. In comparison, the phase transition temperatures decreased sharply (by up to 161 ℃) at low concentrations of PFW, followed by mild changes (by up to 47 ℃) afterwards. The dielectric constant spectra were analyzed in terms of diffuseness characteristics, which reflected the phase transition modes quite well.
关键词： dielectric materials/properties,perovskites,ferroelectricity/ferroelectric materials,reaction
更新于2025-09-09 09:28:46