Structure and dielectric properties of Nd x Sr1−x TiO3 ceramics for energy storage application

Polycrystalline Nd-doped SrTiO₃ ceramics with the formula Nd _x Sr_1?x TiO₃ (NSTO, x = 0, 0.024, 0.056, 0.104, 0.152, 0.200) were prepared by solid state reaction route. X-ray diffraction (XRD) analysis confirmed the formation of monophasic compounds and indicated the structure to be changed from cubic to tetragonal by increasing Nd doping concentrations. A remarkable decrease in grain size from ~30 μm for un-doped SrTiO₃ ceramics to ~1 μm for Nd-doped SrTiO₃ ceramics with x = 0.024 was observed by scanning electron microscopy. The grain size had a degree of increasing with further increasing Nd doping concentration and reached ~3 μm when the x value was 0.200. The dielectric properties of NSTO ceramics were measured at 1 kHz in ambient temperature. It revealed that the dielectric constant dramatically increases for the reason of Nd doping, leading to a maximum value of 19,800 for as-sintered sample with x = 0.104. The breakdown strength of all Nd-doped SrTiO₃ samples was found to be higher than 10 kV/mm. The relationship between dielectric properties and the microstructure feature, as well as the defect structures correlated with the charge compensation induced by trivalent Nd³⁺ doping, was discussed tentatively.     

Sm doped BNT–BZT lead-free ceramic for energy storage applications with broad temperature range

Journal of Materials Science: Materials in Electronics - Dielectric ceramics with good temperature stability and excellent energy storage performances are in great demand for numerous electrical...     

Synthesis,structural and dielectric properties of 0.8PMN–0.2PT relaxor ferroelectric ceramic

A 0.8PMN–0.2PT solid-solution ceramic was synthesized by columbite processing technique. The effects of sintering temperature on the density, structure and microstructure and in turn on the dielectric properties were investigated. The ceramics sintered at and above 1050\(^{\circ }\hbox {C}\) resulted in single-phase perovskite formation. However, high density >90% is achieved only after 1170\(^{\circ }\hbox {C}\). Microstructural analysis revealed that grain size increases with increase in sintering temperature. A significant increase in the peak of dielectric permittivity only after 1150\(^{\circ }\hbox {C}\) owing to increase in density is noted in this study. The quadratic law applied to this ceramic demonstrates that the transition is diffused. The broadness in phase transition and lower dielectric relaxation obtained for the composition demonstrate that the ceramic exhibits characteristics of both relaxor and normal ferroelectrics. The ceramic of composition 0.8PMN–0.2PT exhibits excellent dielectric properties \(\varepsilon _{\mathrm{r}\text {-}\mathrm{max}} =\) 20294?27338 at 100 Hz with \(T_{\mathrm{c}} = 100\)–\(96^{\circ }\hbox {C}\) at low sintering temperature 1170–1180\(^{\circ }\hbox {C}\), respectively.     

Structure evolutions with enhanced dielectric permittivity and ferroelectric properties of Ba(1−x)(La,Li)xTiO3 ceramics

Journal of Materials Science: Materials in Electronics - Polycrystalline Ba(1?x)(La0.50Li0.50)xTiO3 (0?≤?x?≤?0.12) ceramics are fabricated via the...     

Characterization of amorphous hydrocarbon CDx films (x ∼ 0.5) for energy storage applications

Abstract

Smooth hydrocarbon films formed on the vacuum chamber walls in tokamaks under the erosion of graphite elements during deuterium plasma discharges are the main accumulators of hydrogen isotopes in carbon matrices. Therefore, they can be considered as a promising material for hydrogen storage applications. In the present work, such hydrocarbon CD_x films (x ～ 0.5) produced in T-10 tokamak (NRC Kurchatov Institute, Russia) were studied using scanning electron microscopy (SEM), NEXAFS and EXAFS spectroscopies together with thermal desorption (TD) for the films’ characterization and estimation of their hydrogen storage capacity. The C 1s X-ray absorption spectra of the CD_x films were recorded for the first time using the BESSY II storage ring facility (Germany). The obtained NEXAFS spectra were found typical for CK-spectra of sp³ + sp² hydrocarbon systems with a high H/C ratio. The role of Fe impurities from the tokamak chamber walls was elucidated as a catalytic effect “facilitating” the thermal desorption of hydrogen (deuterium) from CD_x films. The Fe K-edge spectra allowed to confirm a fractal (self-affined) structure of CD_x films, with a minimal sp² fractal aggregate ～2–3?nm, and formation of 3D carbon sp³ + sp² network, accumulated a large number of H-isotopes and C_xH_y hydrocarbons. It was found that the H storage and thermal desorption properties of the CD_x films can be improved by their inherent Fe impurities, capable to reduce the barrier of TD and to increase the H/C storage capacity by several times even at room temperature.     

Crystal structure and optimized microwave dielectric properties of (1 − x) LiZn0.5Ti1.5O4–xTiO2 ceramics for application in dielectric resonator

Microwave dielectric ceramics with the composition of (1?x) LiZn_0.5Ti_1.5O₄ (LZT)–xTiO₂ (0.05 ≤ x ≤ 0.4) were prepared by a solid-state reaction route. XRD patterns revealed that the samples consist of LiZn_0.5Ti_1.5O₄ and rutile TiO₂, and the amount of rutile TiO₂ phase increased with increasing the x values. The microwave measurements show that the dielectric properties of ceramics can be improved with increasing x values. When x = 0.1, the temperature coefficient of resonant frequency (τ _f ) of 0.9LZT–0.1TiO₂ ceramic can be adjusted to a near-zero value of ?1 ppm/°C, and permittivity (ε_r) and Q × f value are 26 and 45,000 GHz, respectively. These results indicate that 0.9LZT–0.1TiO₂ ceramic can be a candidate in microwave dielectric resonators.     

Phase structures and microwave dielectric properties of xCaTiO3–(1 − x)Sm0.9Nd0.1AlO3 ceramics

The xCaTiO₃–(1 ? x)Sm_0.9Nd_0.1AlO₃ (0.25 ≤ x ≤ 0.85) microwave dielectric ceramics were prepared by conventional solid state reaction method. The phase structures were characterized by X-ray diffraction, scanning electron microscope and Raman spectra. Solid solutions with the orthorhombic perovskite structure with octahedral tilting were formed from the x range of 0.25 to 0.85. Microwave dielectric properties of xCaTiO₃–(1 ? x)Sm_0.9Nd_0.1AlO₃ ceramics were investigated systematically. The optimum property of the ceramics was obtained for x = 0.65 sintered at 1,415 °C for 3 h: relative permittivity ε_r = 39.70, Q × f = 50,012 GHz, τ _f  = ?6.8 ppm/°C. xCaTiO₃–(1 ? x)Sm_0.9Nd_0.1AlO₃ ceramics provide a new promising material for application in the microwave technology with relative permittivity lying within the range from 39 to 44, high quality factor and near-zero τ _f .     

Effects of coupling agent on the preparation and dielectric properties of novel polymer–ceramic composites for embedded passive applications

The study was carried out to investigate the effects of silane coupling agent, γ-aminopropyl triethoxy silane (KH-550), on the preparation and dielectric properties of Barium titanate (BaTiO₃)/Bisphenol-A dicyanate (2,2′-bis (4-cyanatophenyl) isopropylidene)(BADCy) composites for embedded passive implications. It was found that KH-550 accelerated the polymerization of BADCy and was beneficial to improve the compatibility between BaTiO₃ particles and BADCy matrix. The dielectric constant (ε) and dielectric loss (tanδ) both increased at first and then decreased with the increase of the KH-550 content. With the increase of the frequency, the variation ranges of the dielectric constant and dielectric loss of these composites were not obvious since the dielectric properties of cyanate ester were stable at various frequencies.     

Microstructure and microwave dielectric properties of low-temperature sinterable (1 − x)Ba3(VO4)2–xCaWO4 composite ceramics

Low-temperature-sintered Ba₃(VO₄)₂–CaWO₄ composite ceramics were prepared by cofiring mixtures of pure-phase Ba₃(VO₄)₂ and CaWO₄. The thermo-mechanical analysis revealed that the CaWO₄ in the composite ceramic can significantly promote the densification process and lower the sintering temperature to ~900 °C. The X-ray diffraction results indicated that Ba₃(VO₄)₂ and CaWO₄ phases coexist in the sintered ceramics, and no secondary phases can be detected in the composite, implying the good chemical compatibility between the two phases. The near-zero temperature coefficients of the resonant frequency (τ_f) could be achieved by adjusting the relative content of the two phases owing to their opposite τ_f values. The composite ceramics with 60 wt% CaWO₄ sintered at 900 °C exhibited desirable microwave dielectric properties of the quality factor Q × f ~ 37,000 GHz, dielectric constant ε_r ~ 12, and τ_f ~ ?1.4 ppm/°C.     

Energy storage properties of (1 − x)(Bi0.5Na0.5)TiO3–xKNbO3 lead-free ceramics

In this study, a simple compound (1 ? x)(Bi_0.5Na_0.5)TiO₃–xKNbO₃ (x = 0 – 0.12) lead-free bulk ceramic was developed for high electric power pulse energy storage applications. The dielectric and ferroelectric properties of the ceramics were measured. The results illustrate that the energy storage density of the ceramics is enhanced by the addition of KNbO₃. The influence of applied electric field, temperature, and fatigue on the energy storage properties of the ceramics was evaluated for the composition-optimized (Bi_0.5Na_0.5)TiO₃–0.1KNbO₃ ceramic. The results demonstrate that (Bi_0.5Na_0.5)TiO₃–0.1KNbO₃ ceramic is a promising lead-free material for high power pulse capacitor applications. The excellent energy storage properties of the (Bi_0.5Na_0.5)TiO₃–0.1KNbO₃ ceramics are ascribed to the reversible relaxor–ferroelectric phase transition induced by the electric field.     

Structural, dielectric, and ferroelectric properties of the (1-x)PbTiO₃-xBiAlO₃ solid solution

Ferroelectric ceramics derived from the solid solution of (1-x)PbTiO?-xBiAlO? (x = 0, 0.05, 0.10, 0.15, and 0.18) have been synthesized by solid-state reactions. A pure perovskite phase is formed for 0 ≤ x ≤ 0.15. The tetragonality (c/a) of the solid solution decreases with the increasing amount of BiAlO?. Scanning electron microscopic images reveal a microstructure with a fine grain size of less than 1 μm for the solid solution ceramics (x ≥ 0.05). Compared with pure PbTiOPbTiO? ceramics whose high conductivity and poor densification were harmful to their dielectric performance, the ceramics of (1-x)PbTiO?-xBiAlO? are well-densified (with a relative density of up to 93%) and their dielectric and ferroelectric properties are significantly improved with the addition of BiAlO?, exhibiting reduced dielectric losses, well-developed P-E hysteresis loops (for x = 0.05, 0.10, and 0.15) and a high remnant polarization (P(r)) of 64 μC/cm2 (for x = 0.15).     

The dielectric and thermal properties of Mn-doped (1 − x) ZrTi2O6–xZnNb2O6 filled PTFE composites

High dielectric constant and low loss (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic fillers have been prepared by the conventional solid-state reaction technique. Ceramic filled polytetrafluoroethylene (PTFE) microwave composite substrates were fabricated through the hot-pressing process. The microwave dielectric properties of (1 ? x) ZrTi₂O₆–xZnNb₂O₆/PTFE composites were measured using stripline resonator method. The relative dielectric constant (ε _r) and loss tangent (tan δ) of the composites increase with an increase of x in the (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic at an optimum filler loading of 46vol%. As the x in the (1 ? x) ZrTi₂O₆–xZnNb₂O₆ ceramic increase, the coefficient of thermal expansion and temperature coefficient of dielectric constant decrease. 0.55ZrTi₂O₆–0.45ZnNb₂O₆ filled PTFE composite exhibits a dielectric constant of 7.32 with a loss tangent of 0.0015 (10 GHz) and a temperature coefficient of dielectric constant of ?84 ppm/^oC at an optimum filler loading of 46 vol%.     

Structural,dielectric, and ferroelectric properties of BaTiO3–Bi(Ni1/2Ti1/2)O3 lead-free ceramics with remarkable energy storage performance under low electric fields

Journal of Materials Science: Materials in Electronics - In order to fabricate high-performance dielectric capacitors for pulsed power applications,...     

Structure,morphology, dielectric,and impedance properties of (1-x) (Al0.2La0.8TiO3) + (x) (CuTiO3) (x = 0.2–0.8) nanocomposites

Journal of Materials Science: Materials in Electronics - (1?x) (Al0.2La0.8TiO3) + (x) (CuTiO3) (x?=?0.2–0.8) [ALTCT] nanocomposites were prepared through hydrothermal...     

Microwave dielectric properties of (1 − x)(Mg0.4Zn0.6)2SiO4–xCaTiO3 composite ceramics

Phase formation, microstructure and microwave dielectric properties of (1 ? x)(Mg_0.4Zn_0.6)₂SiO₄–xCaTiO₃ (MZS-C) composite ceramics synthesized by using the conventional solid-state method were systematically investigated. Three phase structure was observed in all samples by using X-ray diffraction and the back scattering electron images. Mg₂SiO₄ can form a solid solution with Zn₂SiO₄, which improved sinterability of the MZS-C composite ceramics. As the CaTiO₃ content was increased from 0.06 to 0.14, dielectric constant ε _r and temperature coefficient of resonant frequency τ _f values of the MZS-C ceramics sintered at 1,180 °C for 4 h increased from 6.74 to 8.35 and ?41.5 to ?6.46 ppm/°C, respectively. Zero τ _f value can be obtained by properly adjusting the x value of the (1 ? x)MZS–xC ceramics. With increasing content of CaTiO₃, densification temperatures of the composite ceramics were decreased. The composite ceramic with x = 0.14 sintered at 1,180 °C for 4 h exhibited excellent microwave dielectric properties of ε _r = 8.35, Q × f = 28,125 GHz and τ _f = ?6.46 ppm/°C.     

Investigation of optical,dielectric, and multiferroic properties of (1 − x) Bi0.9La0.1FeO3–(x) BaTiO3 composites

Journal of Materials Science: Materials in Electronics - In the present work, we synthesized composites (1???x) Bi0.9La0.1FeO3-(x) BaTiO3 with x?=?0.05, 0.10, and 0.15...     

Microwave dielectric properties of (1 − y)Nd(1−2x/3)Bax(Mg0.5Sn0.5)O3–yCa0.8Sr0.2TiO3 ceramic

The (1 ? y)Nd_(1?2x/3)Ba_x(Mg_0.5Sn_0.5)O₃–yCa_0.8Sr_0.2TiO₃ ceramics were prepared by the conventional solid-state method. The X-ray diffraction patterns of the Nd_(1?2x/3)Ba_x(Mg_0.5Sn_0.5)O₃ ceramics revealed that Nd_(1?2x/3)Ba_x(Mg_0.5Sn_0.5)O₃ is the main crystalline phase, which is accompanied by a little Nd₂Sn₂O₇ as the second phase. An apparent density of 6.89 g/cm³, a dielectric constant (ε _r ) of 19.1, a quality factor (Q × f) of 212,000 GHz, and a temperature coefficient of resonant frequency (τ _f ) of ?68 ppm/°C were obtained when the Nd_2.94/3Ba_0.03(Mg_0.5Sn_0.5)O₃ ceramics were sintered at 1,550 °C for 4 h. The temperature coefficient of resonant frequency (τ _f ) increased from ?68 to +55 ppm/°C as y increased from 0 to 0.7 when the (1 ? y)Nd_2.94/3Ba_0.03(Mg_0.5Sn_0.5)O₃–yCa_0.8Sr_0.2TiO₃ ceramics were sintered at 1,600 °C for 4 h. 0.4Nd_2.94/3Ba_0.03(Mg_0.5Sn_0.5)O₃–0.6 Ca_0.8Sr_0.2TiO₃ ceramic that was sintered at 1,600 °C for 4 h had a τ _f of ?7 ppm/°C.     

Structure and microwave dielectric properties of 5BaO–2V2O5 binary ceramic system

5BaO–2V₂O₅ ceramic has been prepared by conventional solid state reaction method. The X-ray diffraction and Laser Raman studies have been carried out to ascertain the phase purity and crystal structure of the prepared composition. The microwave dielectric properties of the well sintered ceramic compacts were measured by Hakki & Colemann post resonator and cavity perturbation techniques using a vector network analyzer. The 5BaO–2V₂O₅ ceramic exhibits a low dielectric constant of 12.1, relatively good quality factor of 26,790 GHz, and a small temperature variation of resonant frequency of 7 ppm/°C in the microwave frequency region.