共查询到20条相似文献,搜索用时 15 毫秒
1.
Dong-Wan Kim Do-Kyun Kwon Kug Sun Hong Deug Joong Kim 《Journal of the American Ceramic Society》2003,86(5):795-799
Samples of 1/6Ba5 Nb4 O15 ·5/6BaNb2 O6 along with the pure end members, Ba5 Nb4 O15 and BaNb2 O6 , were sintered under low oxygen partial pressure. The degradation mechanisms of dielectric loss in this reducing atmosphere have been studied. We found that the degradation occurred primarily due to the formation of oxygen vacancies caused by the reduction of Nb5+ . This was determined by measuring the electrical conductivity, and through X-ray photoelectron spectroscopy. More importantly, the dielectric loss of 1/6Ba5 Nb4 O15 ·5/6BaNb2 O6 samples with higher temperature stability was further decreased on sintering in a reducing atmosphere. This observation has been explained by considering the increased porosity and formation of a reduced second phase, Ba0.65 NbO3 . 相似文献
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Jen-Yan Hsu Nan-Chung Wu Shu-Cheng Yu 《Journal of the American Ceramic Society》1989,72(10):1861-1867
The sintering temperature of multilayer ceramic substrates must decrease to 1000° or below to avoid melting the conductors (Pd-Ag, Au, or Cu) during sintering. In this study, SiO2 , CaO, B2 O3 , and MgO were used as additives to Al2 O3 to decrease the firing temperature by liquid-phase sintering. Compositions with 18.0 and 22.5 wt% B2 O3 were sintered at around 1000° in an air atmosphere to yield dense ceramics with good properties: relative dielectric contant between 6 to 7 (1 MHz), tan δ≤× 3 × 10−4 (1 MHz), insulating resistivity > 1014 ω cm, coefficient of thermal expansion ∼ 7.0 × 10−6 /°, and thermal conductivity ∼ 4.1 W/(m · K). 相似文献
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Da Xu Wenhan Xu Thomas Seery Haibo Zhang Chenyi Zhou Jinhui Pang Yunhe Zhang Zhenhua Jiang 《大分子材料与工程》2020,305(3)
High‐temperature polymer dielectrics are in great demand for harsh‐environment applications. Maintaining high‐energy storage density and low loss at elevated temperatures remains a major challenge for polymer dielectrics. In this work, a new type of polymer dielectric material is designed, which exhibits comparable dielectric properties in the start‐of‐the‐art dielectric nanocomposites and a superior potential for scale up. A soluble, glassy state polymer with a polarizing group is designed by introducing a weakly polar group into the polyaramid (PA) backbone to dilute the hydrogen bonding of the PA parent species. This increases the mobility of the molecular dipole within the polymer in the glassy state, thereby increasing its dielectric constant while maintaining the high‐temperature performance. The result of this design is a polymer with a glass transition temperature of 251 °C, a dielectric constant of up to 4.5, and a dielectric loss of 1%, while maintaining 2.1 J cm?3 energy density and 86.8% efficiency at 200 °C. This polymer, with its excellent, intrinsic, electrical‐energy‐storage properties can also be adapted for a roll‐to‐roll capacitor film production. Breaking intermolecular hydrogen bonds to enhance the electrical‐energy‐storage properties of polymers is an excellent path for designing polymer dielectrics with high‐temperature capabilities. 相似文献
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Zhu Jiang Xinyi Li Yi Jin Xiaosong Zhang Lige Tong Li Wang Yulong Ding 《化学,工程师,技术》2023,95(1-2):40-58
This article reviews the state of the art of the formulation and fabrication of sensible, latent, and thermochemical thermal energy storage (TES) materials with special focus on the role of particle technology in enhancing the performance of these materials. Molten salt-based sensible TES materials have been intensively studied, particularly the use of doped nanoparticles for enhancing specific heat capacity and thermal conductivity. For latent TES, the inclusion of property enhancers is among the most effective approaches to address the low thermal conductivity and supercooling issues of phase change materials (PCMs), whereas the encapsulation of PCMs and structurally stabilized composite PCMs are the favorable methods to address leakage and chemical incompatibility challenges. Thermochemical TES materials are often incorporated with an inert or an active host matrix for structural stabilization. 相似文献
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Klaus Prume Rainer Waser Klaus Franken Horst R. Maier 《Journal of the American Ceramic Society》2000,83(5):1153-1159
The opportunities are introduced to calculate the electrical, mechanical, and thermal couplings of ceramic multilayer capacitors (MLCs) with the finite-element method. The results may lead to improvements in the production, integration, and operation of MLCs. In this paper, a comparison is given of calculations and measurements of electromechanical resonances in the impedance spectra of MLCs. The simulation of defective capacitors with three different types of assumed faults reveals the changes in the impedance spectra due to these defects. This allows the prediction of flaws in MLCs based on measurement of the impedance spectra. 相似文献
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Reaction-controlled binder burnout of ceramic multilayer capacitors (CMCs) is conducted in a series of small-scale experiments. the burnout process is followed by monitoring the weight of the CMCs. The observed maximum weight loss rate, obtained with a conventional linear heating process, is used to design a weight-time program for a reaction-controlled process. In this process the actual CMC weight is controlled to closely follow the weight program by means of continuous control with the batch temperature. The advantages of this procedure are discussed. The results of the present study, although being restricted to oxidative burnout of a special product, are thought to be of some use for other ceramic burnout situations. The relevant parts of controller design are discussed together with some comments on scale-up. 相似文献
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Current Understanding of Structure–Processing–Property Relationships in BaTiO3–Bi(M)O3 Dielectrics 下载免费PDF全文
Michaela A. Beuerlein Nitish Kumar Tedi‐Marie Usher Harlan James Brown‐Shaklee Natthaphon Raengthon Ian M. Reaney David P. Cann Jacob L. Jones Geoff L. Brennecka 《Journal of the American Ceramic Society》2016,99(9):2849-2870
As part of a continued push for high permittivity dielectrics suitable for use at elevated operating temperatures and/or large electric fields, modifications of BaTiO3 with Bi(M)O3, where M represents a net‐trivalent B‐site occupied by one or more species, have received a great deal of recent attention. Materials in this composition family exhibit weakly coupled relaxor behavior that is not only remarkably stable at high temperatures and under large electric fields, but is also quite similar across various identities of M. Moderate levels of Bi content (as much as 50 mol%) appear to be crucial to the stability of the dielectric response. In addition, the presence of significant Bi reduces the processing temperatures required for densification and increases the required oxygen content in processing atmospheres relative to traditional X7R‐type BaTiO3‐based dielectrics. Although detailed understanding of the structure–processing–property relationships in this class of materials is still in its infancy, this article reviews the current state of understanding of the mechanisms underlying the high and stable values of both relative permittivity and resistivity that are characteristic of BaTiO3‐Bi(M)O3 dielectrics as well as the processing challenges and opportunities associated with these materials. 相似文献
9.
Jun Gao Do‐Kyun Kwon Steven Perini Jeffery Long Shihai Zhang Michael T. Lanagan 《Journal of the American Ceramic Society》2016,99(12):4045-4049
Thin and flexible glass ribbons can be rolled into a film capacitor structures for power electronic circuits. Glass has excellent electrical properties and is a leading candidate to replace polymer films for high‐temperature applications. The dielectric properties of a low‐alkali aluminoborosilicate glass were characterized up to temperatures of 400°C. Low‐field permittivity values of 6 with dielectric loss below 0.01 were found for temperatures below 300°C. The dielectric breakdown strength exceeded 5 MV/cm for temperature of 400°C and high‐field polarization measurements showed that glass has over 95% energy efficiency at temperatures of 200°C, which is a target temperature for high‐temperature power electronic circuits driven by wide bandgap semiconductor devices. 相似文献
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John G. Pepin William Borland Patrick O'Callaghan Richard J. S. Young 《Journal of the American Ceramic Society》1989,72(12):2287-2291
Delaminations are a principal quality problem in the manufacture of multilayer ceramic capacitors (MLC's). They are defined as a separation of the electrode and dielectric layers and can result in electrical shorts and/or life failures. Delaminations originate from many sources in MLC manufacture, but we have identified four which are caused by the electrode. High levels of organic resin in the electrode paste lead to high resin content in dried electrode prints, requiring removal of large amounts of organic residues during burnout, causing delaminations. Catalysis of these organics by the precious metals also causes delaminations from rapid evolution of gas and heat release during burnout. Poor adhesion of the dielectric tape layers to dried electrode prints during MLC buildup can cause "green-state" delaminations which remain through firing. Sintering shrinkage mismatch between the electrode and dielectric layers leads to internal stresses in MLC's, resulting in delaminations. We discuss these electrode-based mechanisms of delamination and the design of electrode pastes which solve these problems. 相似文献
11.
Jacob Lasri Peelamedu D. Ramesh Levi Schächter 《Journal of the American Ceramic Society》2000,83(6):1465-1468
A quasi-analytic model has been developed to examine energy conversion during the microwave sintering of a ceramic that is surrounded by a susceptor. Low-loss ceramics, such as ZrO2 , couple poorly with microwave radiation at low temperatures; however, because the dielectric loss usually increases rapidly as temperature increases, coupling improves dramatically at high temperatures. To improve heat transfer at low temperatures, susceptors are used. Three processes of energy flow are considered: microwave absorption due to dielectric losses, blackbody radiation, and heat convection. As expected, the susceptor (SiC) heats rapidly, relative to the ceramic (ZrO2 ), at low temperatures; however, the ceramic attains higher temperatures after a prolonged period of microwave exposure. Below a critical temperature (800°C), the primary heat-transfer mechanism to the ZrO2 is blackbody radiation from the susceptor. Above this temperature, microwave radiation is the main source that contributes to the temperature increase of the ceramic. The results of the simulation are in reasonable agreement with recent experimental data. 相似文献
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《Journal of the European Ceramic Society》2020,40(15):5450-5457
BiFeO3-BaTiO3-based relaxor ferroelectric ceramic has attracted increasing attention for energy storage applications. However, simultaneously achieving high recoverable energy storage density (Wrec) and efficiency (η) under low electric field has been a longstanding drawback for their practical applications. Herein, a novel relaxor ferroelectric material was designed by introducing (Sr0.7Bi0.2)TiO3 (SBT) into the composition 0.67BiFeO3-0.33BaTiO3 (BF-BT-xSBT). A large Wrec of ∼2.40 J/cm3 and a high η of ∼90.4 % were simultaneously realized under a low electric field of 180 kV/cm, which is superior to that of most previously reported lead-free ceramics. Moreover, moderate temperature endurance and excellent frequency stability were also obtained. More importantly, this ceramic has a large discharge current density (∼289.18 A/cm2), a discharge power density (∼14.46 MW/cm3) and short discharge time (<0.25 μs). These results not only demonstrate superior potential in BF-BT-SBT ceramics, but also offer a new design to tune the energy storage performance of lead-free relaxor ferroelectric ceramics. 相似文献
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SiO2陶瓷基体的复合相变储能材料主要是由SiO2陶瓷基体和Na2SO4相变材料组成。通过实验探讨基体材料的粒度、成型压力、烧成温度对结果的影响。采用示差扫描量热仪(DSC)测定所制备的样品的融解热,采用热重分析仪(TG)表征样品的热稳定性。 相似文献
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采用熔融法制备了钛酸锶钡(barium strontium titanate,BST)基玻璃,然后将此玻璃样品在不同的温度下进行热处理得到BST基玻璃陶瓷,采用差热分析研究了BST基玻璃陶瓷析晶过程中的热力学特征,用扫描电子显微镜和X射线衍射分别分析了玻璃陶瓷的显微结构和相结构,并且系统研究了该玻璃陶瓷的介电特性以及耐击穿电场强度。结果表明:0.3%(质量分数)Ag+掺杂时,BST基玻璃中BST相的析晶温度从885℃下降到840℃,有利于玻璃体中BST晶体的析出。另外,Ag+的掺杂有利于提高BST基玻璃陶瓷的介电常数,同时能维持较低的介电损耗。此外,Ag+掺杂能够提高BST基玻璃的耐击穿电场强度,其在800℃热处理后,可达96.3 kV/mm,高于未掺杂Ag+的BST基玻璃的52.5kV/mm。 相似文献
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综述了用于节能领域的相变储能材料的分类及其性能、优缺点;重点论述了新型相变材料的研究发展;并探讨了相变材料在太阳能利用、医疗、建筑节能等领域的应用;展望了未来相变材料的发展方向和应用前景。 相似文献
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High‐Energy Storage Performance in (Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 AFE Thick Films Fabricated via a Rolling Process 下载免费PDF全文
(Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 antiferroelectric (AFE) thick films with a thickness of about 85 μm were successfully fabricated via a rolling process using an improved sintering method, and all specimens showed high‐energy‐storage performance. The X‐ray diffraction, SEM pictures, and hysteresis loops confirmed that the sintering temperature had an important influence on the microstructures, dielectric properties and energy storage performance of AFE thick films. The grain size and the storage efficiency increased with the increasing sintering temperature, the energy storage performance was enlarged by the rolling process. As a result, a maximum recoverable energy density of 7.09 J/cm3 with an efficiency of 88% was achieved at room temperature, together with stable energy‐storage behavior, which was almost three times higher than that (2.43 J/cm3) of the bulk ceramics counterparts. The results demonstrated that the improved method was an effective way to improve the breakdown strength and energy storage performance of AFE thick films, and (Pb0.98La0.02)(Zr0.45Sn0.55)0.995O3 AFE thick films were a promising material for high‐power energy storage. 相似文献
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