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1.
(Na1/2 La1/2 )(Mg1/3 Nb2/3 )O3 undergoes a series of phase transitions that involve cation order on the A- and B-sites of the parent perovskite structure. At high temperatures both sites contain a random distribution of cations; below 1275°C a 〈111〉 layering of Mg and Nb leads to the formation of a 1:2 ordered structure with a monoclinic supercell. A second transition was observed at 925°C, where the Na and La cations order onto alternate A-site positions along the 〈001〉 direction of the parent subcell. By quenching samples from above 1275°C to preserve the disorder on the B-site, a fourth variant of this compound was obtained by inducing A-site order through a subsequent anneal at 900°C. Although the changes in structure do not produce significant alterations in the relative permittivity (ɛr ∼ 35), they do have a significant effect on the value of the temperature coefficient of the capacitance. 相似文献
2.
The temperature coefficient of the resonant frequency (TCF) of complex perovskite (Pb1−xCax)[Fe0.5(Nb1−yTay)0.5]O3 ceramics (x= 0.5, 0.55; 0.0 ≤y≤ 1.0) was investigated, relative to the bond valence of the A- and B-site ions in the ABO3 perovskite structure (such as the barium-, strontium-, and calcium-based complex perovskites). The TCF of these complex perovskite compounds varied with the bond valence of the A- and B-sites and the tolerance factor (t) in the perovskite structure. In the tilted region (t < 1.0), the tilting of the oxygen octahedra increased and the TCF decreased, because of the increased bond valence of the B-site. Also, the dependence of TCF on the bond valence of the A-site was similar to its dependence on t. 相似文献
3.
Do-Kyun Kwon Clive A. Randall Thomas R. Shrout Michael T. Lanagan 《Journal of the American Ceramic Society》2004,87(6):1088-1092
The dielectric properties and frequency dispersion associated with a dielectric relaxation were evaluated within the perovskite (1− x )BiScO3 – x Ba(Mg1/3 Nb2/3 )O3 solid solution systems (0.7 ≤ x ≤ 1). With increasing BiScO3 , the room-temperature dielectric permittivity at low frequency (100 Hz) increased up to 115 at x = 0.7, and a dielectric relaxation phenomenon was evident. Relaxation parameters were analyzed using several Arrhenius-type equations, and the microwave dielectric property measurement using rectangular wave-guide method enabled confirmation of the extrapolated value of the Arrhenius plot. The result of the microwave dielectric property measurement was also checked with J -function fitting based on the frequency-dependent Gaussian distribution of the associated dielectric loss data at low frequency. 相似文献
4.
Perovskite developments in the Pb(Zn1/3 Ta2/3 )O3 –PbTiO3 system were explored. Formation yields and lattice parameters of the perovskite were determined from X-ray diffractometry results. Weak-field low-frequency dielectric properties of the system ceramics were investigated, followed by microstructure examination. Perovskite started to develop in Pb(Zn1/3 Ta2/3 )O3 after the introduction of 30 mol% PbTiO3 , whereas complete stabilization was accomplished at 60% substitution. Dielectric relaxation behavior was not substantial across the entire composition range, whereas phase transition modes changed from diffuse to sharp with increased PbTiO3 fraction. 相似文献
5.
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 hours heat treatment. The maximum dielectric constant values increased with increasing PFW fractions. In comparison, the phase transition temperatures decreased sharply (by up to 161°C) at low concentrations of PFW, followed by mild changes (by up to 47°C) afterward. The dielectric constant spectra were analyzed in terms of diffuseness characteristics, which reflected the phase transition modes quite well. 相似文献
6.
Yuanhua Lin Ce-Wen Nan Jianfei Wang Gang Liu Junbo Wu Ning Cai 《Journal of the American Ceramic Society》2004,87(4):742-745
The dielectric properties of Na0.5 Bi0.5 TiO3 (NBT) -based composites incorporating silver particles prepared by sintering at a low temperature of ∼900°C are reported. The dielectric constant increases with the amount of metal silver particles in the measured frequency range (150 Hz to 1 MHz), and could be enhanced up to ∼20 times higher than that of pure NBT ceramics, which was ascribed to the effective electric fields developed between the dispersed particles in the matrix and the percolation effect. Further investigation revealed that the dielectric constant of the composites has weak frequency and temperature dependence (−50°C to +50°C). 相似文献
7.
Beecher H. Watson III Michael J. Brova Mark A. Fanton Richard J. Meyer Jr Gary L. Messing 《Journal of the American Ceramic Society》2020,103(11):6319-6329
The effects of acceptor doping with manganese as either MnO2 or MnNb2O6 (MnN) with CuO on the dielectric, ferroelectric, and piezoelectric properties of PIN-PMN-PT ceramics were investigated. The 2% MnNb2O6-doped PIN-PMN-PT (6Pb(Mn1/3Nb2/3)O3-25Pb(In1/2Nb1/2)O3-34Pb(Mg1/3Nb2/3)O3-35PbTiO3) ceramics possessed hard properties such as high coercive field (EC) of 11.7 kV/cm, low dielectric loss (tan δ) of 0.7%, and high electromechanical quality factor (QM) of 1011. These properties were diminished in MnO2-doped ceramics because of lower oxygen vacancy defect concentration, and exaggerated grain growth resulted in >20 µm grain size. Co-doping with 2 mol% MnNb2O6 and 0.5 mol% CuO retained hardened properties such as high EC of 9.6 kV/cm, low tan δ of 0.6%, and high QM of 1029. MnNb2O6-doped and MnNb2O6 + Cu co-doped ceramics display excellent figures of merit for resonance and off-resonance applications as well as high energy conversion efficiencies which make them promising candidates for high-power transducer elements. 相似文献
8.
CaTiO3 linear dielectric ceramics with greatly enhanced dielectric strength and energy storage density
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Hai Yang Zhou Xiao Qiang Liu Xiao Li Zhu Xiang Ming Chen 《Journal of the American Ceramic Society》2018,101(5):1999-2008
CaTiO3 is a typical linear dielectric material with high dielectric constant, low dielectric loss, and high resistivity, which is expected as a promising candidate for the high energy storage density applications. In the previous work, an energy density of 1.5 J/cm3 was obtained in CaTiO3 ceramics, where the dielectric strength was only 435 kV/cm. In fact, the intrinsic dielectric strength of CaTiO3 is predicted as high as 4.2 MV/cm. Therefore, it should be a challenge issue to enhance the dielectric strength and energy storage density of CaTiO3 ceramics by optimizing the microstructures. In the present work, dense CaTiO3 ceramics with fine and uniform microstructures are prepared by spark plasma sintering, and the greatly enhanced dielectric strength (910 kV/cm) and energy storage density (6.9 J/cm3) are obtained. This can be ascribed to the improved resistivity and thermal conductivity, associated with the fine and uniform microstructures. The different post‐breakdown features of CaTiO3 ceramics prepared by different process well interpret why the enhanced dielectric strength is achieved in the SPS sample. The energy storage density can be further improved to 11.8 J/cm3 by introducing the amorphous alumina thin films as the charge blocking layer, where the dielectric strength is 1188 kV/cm. 相似文献
9.
Takaaki Tsurumi Young-Bae Kil Kouhei Nagatoh Hirofumi Kakemoto Satoshi Wada Sadayuki Takahashi 《Journal of the American Ceramic Society》2002,85(8):1993-1996
The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ∼50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses. 相似文献
10.
Qiang Li Jianxin Wei Tinglong Tu Jinrong Cheng Jianguo Chen 《Journal of the American Ceramic Society》2017,100(12):5573-5583
Effects of quenching process on dielectric, ferroelectric, and piezoelectric properties of 0.71BiFeO3?0.29BaTiO3 ceramics with Mn modification (BF–BT?xmol%Mn) were investigated. The dielectric, ferroelectric, and piezoelectric properties of BF–BT?xmol%Mn were improved by quenching, especially to the BF–BT?0.3 mol%Mn ceramics. The dielectric loss tanδ of quenched BF–BT?0.3 mol%Mn ceramics was only 0.28 at 500°C, which was half of the slow cooling one. Meanwhile, the remnant polarization Pr of quenched BF–BT?0.3 mol%Mn ceramics increased to 21 μC/cm2. It was notable that the piezoelectric constant d33 of quenched BF–BT?0.3 mol%Mn ceramics reached up to 191 pC/N, while the TC was 530°C, showing excellent compatible properties. The BF–BT?xmol%Mn system ceramics showed to obey the Rayleigh law within suitable field regions. The Rayleigh law results indicated that the extrinsic contributions to the dielectric and piezoelectric responses of quenched BF–BT?xmol%Mn ceramics were larger than the unquenched ceramics. These results presented that the quenched BF–BT?xmol%Mn ceramics were promising candidates for high‐temperature piezoelectric devices. 相似文献
11.
12.
The compositional dependence of microwave dielectric properties has been investigated in the (1 − x )(Na1/2 Nd1/2 )TiO3 − x Nd(Mg1/2 Ti1/2 )O3 (NNT-NMT) system. The addition of NMT results in significant improvement in the quality factor and the temperature coefficient of frequency, but gradually decreases the dielectric constant from ∼100 for pure NNT to ∼25 for pure NMT. The single perovskite phase is observed with various { hkl } superlattice reflections over the entire compositional range. The increasing tendency of peak splitting with increasing x at some perovskite reflections strongly suggests that the crystal structure of the system changes to lower symmetry structures. This is confirmed using infrared reflectivity spectra. The superlattice reflections related to structural deviation become more predominant as the composition reaches pure NMT. Particularly, {111} superlattice reflections are believed to be associated with the 1:1 cation ordering and responsible for the observed abrupt increase in quality factor at x > 0.7. 相似文献
13.
Effect of Ba2+ substitution for Pb2+ on the dielectric and electric-field-induced strain characteristics of the PMN–PZ–PT ceramics has been investigated in the compositions of the tetragonal-rich 0.2PMN–0.36PZ–0.44PT and rhombohedral-rich 0.2PMN–0.4PZ–0.4PT ceramics. The phase approached cubic structure from the tetragonal and rhombohedral, and grain size was reduced when the Ba2+ cation was substituted. As Ba2+ content increased, frequency-dependent relaxor-like behavior of the dielectric constant was observed at temperatures below the dielectric maximum ( T max ) for compositions with 20 and 25 mol% Ba2+ . Electric-field-induced strain was maximized in the 12 mol% Ba2+ -substituted 0.2PMN–0.4PZ–0.4PT specimen ( S max = 0.15%), and maximum piezoelectric, d 31 , was 300 in the 14 mol% Ba2+ -substituted 0.2PMN–0.4PZ–0.4PT specimen. 相似文献
14.
X. M. Chen D. Liu R. Z. Hou X. Hu X. Q. Liu 《Journal of the American Ceramic Society》2004,87(12):2208-2212
Ca(Zn1/3 Nb2/3 )O3 microwave dielectric ceramics were prepared using a solid-state reaction process, and their microwave dielectric properties were evaluated as functions of sintering and postdensification annealing conditions. The relationship between microwave dielectric properties and processing was interpreted through the variation of microstructures. The dielectric constant showed slight variation with sintering and annealing conditions, but the Q × f value increased at first and then decreased with increased sintering temperature, and annealing in oxygen indicated significant improvement in Q × f , especially for the specimens sintered at higher temperatures. The good microwave dielectric properties were obtained in the ceramics sintered at 1225°C in air for 3 h and annealed at 1100°C in oxygen for 8 h: ɛ= 34.1, Q × f = 15 890 GHz, τf =−48 ppm/°C. 相似文献
15.
The present research describes synthesis of perovskite lead zirconate titanate (PZT) nanocrystalline mesoporous powders from the aqueous solutions of Pb2+ , Zr4+ , and Ti4+ metal ions using sucrose as a template material. Sucrose retains the metal ions in solution through complex formation. Dehydration and thermal decomposition of the metal ion–sucrose mass produces a large amount of gas, which helps to create porosity and high surface area in the final products. The particle size of the synthesized powder is between 50 and 60 nm, with a average specific surface area between 20 and 25 m2 /g. The surface area increases as the amount of sucrose increases. Nanocrystalline PZT powder with high surface area can be useful for low-temperature sintering. 相似文献
16.
Yong S. Cho Steven M. Pilgrim Herbert Giesche Keith Bridger 《Journal of the American Ceramic Society》2000,83(10):2473-2480
A particulate coating process incorporating small amounts of several additives such as titanium, zinc, barium, strontium and iron was used to modify the composition and resultant dielectric and electromechanical properties of a commercially available 0.96(0.91Pb(Mg1/3 Nb2/3 )O3 ·0.09PbTiO3 )·0.04BaTiO3 . This method led to intimate mixing of the additives at the nanoscale without an additional ball-mixing process. Low- and high-field characteristics including dielectric properties, induced strain and polarization, and associated hystereses were evaluated for the samples sintered at 1200°C for 4 h. All properties were found to depend on the chemical additives and temperature. Specifically, the addition of small quantities of titanium and barium tended to increase strain and Q eff while maintaining a low dielectric constant which is a promising result for room temperature transducer applications. The addition of titanium with zinc or iron raised dielectric constant, strain, and polarization with significant increases in the temperature of maximum permittivity. On the other hand, the electromechanical properties of the samples containing barium or zinc with titanium did not exhibit a transition to piezoelectric behavior at the temperature expected from the dielectric measurements. 相似文献
17.
Perovskite-phase developments in partially/fully substituted (Ba,Pb)(Zn1/3 Nb2/3 )O3 , synthesized via B-site precursor routes, were investigated. The pyrochlore structure, present at no barium content, was immediately replaced by perovskite with a small amount (≥8 at.%) of barium substitution. Variations in the lattice parameters of the pyrochlore and perovskite structures were studied. The weak-field radio-frequency dielectric constants and losses of the system ceramics were examined. A highest maximum dielectric constant of 9000 (76°C, 1 MHz) was observed at 8 at.% barium substitution. The dielectric-constant spectra were analyzed further in terms of diffuseness characteristics (e.g., diffuseness exponent and degree of diffuseness). The dielectric hysteresis loops of the ceramics were measured. The microstructures of the sintered ceramics also were observed. 相似文献
18.
The effects of calcium substitution on the structural and microwave dielectric characteristics of [(Pb1− x Ca x )1/2 La1/2 ](Mg1/2 Nb1/2 )O3 ceramics (with x = 0.01–0.5) were investigated. All the materials were observed to have an ordered A(B1/2 ' B1/2 " )O3 -type perovskite structure; however, the space group of the structure changed from Fm 3 m to Pa 3 as the calcium content increased to x = 0.1, and then from Pa 3 to R 3¯ at the x = 0.5 composition. During the structural evolution, the lattice parameter of the perovskite cell decreased linearly, and the dielectric constant ( k ) also decreased, from k = 80 to k = 38. However, the product of the quality factor and the resonant frequency ( Q × f ) increased from 50 000 GHz to 90 000 GHz as the calcium content increased. Also, the temperature coefficient of resonant frequency (τƒ ) gradually changed from 120 ppm/°C to −40 ppm/°C as the calcium content increased. At the x = 0.3 composition, a combination of properties— k ∼ 50, Q × f ∼ 86 000 GHz, and τƒ ∼ 0 ppm/°C—can be obtained. 相似文献
19.
Hung C. Ling Man F. Yan Warren W. Rhodes 《Journal of the American Ceramic Society》1991,74(2):287-289
The aging behavior of a series of lead perovskite dielectrics with the compositions x Pb(Fe2/3 W1/3 )O3 ·(1 – x )Pb(Fe1/2 -Nb1/2 )O3 , where 0 ≤ x ≤ 1, and the effect of dopants were studied. Below the Curie temperature ( T c ), the capacitance and the dissipation factor (tan δ) decrease approximately linearly with logarithmic time. The aging rate depends on the temperature difference, Δ T , between the aging temperature and T c , and on the dopant concentration, but is independent of the measurement frequency between 1 and 1000 kHz. The maximum aging rate is about 3% per decade of time for capacitance and 5% per decade for tan δ at 1 mol% dopant concentration, and increases to 6.3% for capacitance and 8.5% for tan δ at 0.7 mol% dopant concentration. These results are consistent with an aging mechanism caused by changing ferroelectric domain structure with time, as proposed for BaTiO3 . 相似文献
20.
Functional and structural effects of layer periodicity in chemical solution‐deposited Pb(Zr,Ti)O3 thin films
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Steven J. Brewer Samuel C. Williams Carmen Z. Deng Aaron B. Naden Sabine M. Neumayer Brian J. Rodriguez Amit Kumar Nazanin Bassiri‐Gharb 《Journal of the American Ceramic Society》2017,100(12):5561-5572
This work investigates the role of crystallization layers’ periodicity and thickness on functional response in chemical solution‐deposited lead zirconate titanate thin films, with periodic, alternating Zr and Ti gradients normal to the surface of the film. The films were processed with a range of layer periodicities and similar total film thickness, in order to relate the number of layers and compositional oscillations to structural and functional response changes. Trends of increased extrinsic contributions to the dielectric and ferroelectric responses are observed with increasing layer periodicity, but are counterpointed by simultaneous reduction in intrinsic contributions to the same. Transmission electron microscopy reveals in‐plane crystallographic discontinuity at individual crystallization interfaces. Samples with smaller periodicity, and thus thinner layers, potentially suffer from grain size refinement and subsequent reduction in domain size, thereby limiting extrinsic contributions to the response. The strong compositional oscillations in samples with larger periodicity result in deep fluctuations to the tetragonal side of the phase diagram, potentially reducing intrinsic contributions to the response. Conversely, piezoresponse force microscopy results suggest that large chemical oscillations in samples with larger periodicity also result in closer proximity to the morphotropic phase boundary, as evidenced by local acoustic softening at switching, signaling potential field‐induced phase transitions. 相似文献