Dielectric Degradation and Microstructures of Heterogeneous Interfaces in Cofired Multilayer Ceramic Capacitors

The compatibility of electrodes and dielectrics in cofired MLCCs with both Ni and Ag/Pd electrodes was characterized by transmission electron microscopy (TEM) using tripod polished samples. Tripod polishing procedures can reduce entire devices to a thickness of less than 1 m. After low angle ion milling for a short time, many regions across several dielectric and electrode layers are electron transparent, which makes it possible to characterize the cofired interfacial microstructures. When analyzed by convergent beam electron diffraction (CBED) and energy dispersive X-ray spectrometry (EDS), NiO lamellae and P-rich intermediate layers were found in highly accelerated life tested (HALT) MLCCs with Ni electrodes. CBED confirmed that the P-rich layers had a Ba₄Ti₁₃O₃₀ (B₄T₁₃) structures. Oxidized Ni layers containing Mn were also found in the HALT samples. It is believed that Mn ions were reduced by the Ni electrodes, as P-rich and Mn-rich segregated layers were observed in the virginal non-life tested MLCCs. Grains with stacking faults, containing dopants such as Mn, Si, and Mg, had the BaTi₄O₉ (BT₄) structure. No silver diffusion was found in either the BaTiO₃ based perovskite lattices or the flux phases in air-fired X7R type MLCCs.     

Microstructural Analysis of X7R-Type BaTiO<Subscript>3</Subscript> Multilayer Ceramic Capacitors (MLCCs)

The microstructures of typical commercial X7R MLCCs were characterized by transmission electron microscopy (TEM), using tripod polished specimens and ion milled samples. Core-shell structures were clearly observed in the TEM specimens, and glass phases located at the grain boundaries and triple points were frequently observed. Their chemical composition was analyzed using energy dispersive X-ray spectrometry (EDS), which showed bismuth ions diffused into the shell regions, while the cores were pure BaTiO₃. X-ray diffraction (XRD) suggested that the predominant phase in the microstructure had pseudocubic global symmetry, while ferroelectric domains were observed in TEM bright field (BF) images. The internal electrodes in the devices were an alloy of Ag/Pd, and these regions were found to have twinned crystal structures. The stress states in the interfaces between the electrodes and the dielectric layers were revealed, and no silver migration in the flux at the electrode-dielectric interfaces was observed.     

Copper Cofire X7R Dielectrics and Multilayer Capacitors Based on Zinc Borate Fluxed Barium Titanate Ceramic

Copper cofired dielectrics may give new opportunities for high temperature capacitors. To demonstrate feasibility, BaTiO₃ has been formulated into X7R dielectrics with copper inner electrodes. This requires the development of a formulation that permits sintering at temperatures below 1000°C, and then firing in a reducing environment in atmospheres pO₂ 10^–8 atms. ZnO—B₂O₃ chemistries were explored with additional dopants to modify densification and the temperature coefficient of capacitance of the BaTiO₃ dielectric anomaly. X7R characteristics with relative dielectric permittivities 2750 and tan 0.01 at 1 kHz were obtained at room temperature. Multilayer capacitors were fabricated in 3.2 mm × 1.6 mm size multilayers with an acrylic binder system and oxidation resistive copper inner electrodes.     

Effect of Interactions at the Cofired Interface of Electrode/Ceramics on the Reliability of Lead-Based Multilayer Ceramic Capacitors

The increase of silver content in the internal electrodes was found to have a negative influence on accelerated-test life of lead magnesium niobate-based multilayer ceramic capacitors under direct current-voltage. Transmission electron microscopy (TEM) and auger electron spectroscopy (AES) analyses were carried out on the cofired electrode/ceramics interfaces to demonstrate the effect of Ag content in the electrode on the reliability of capacitors. The result showed that Ag could diffuse into the ceramic layers for more than one micrometer. We designed Ag-doping experiments to study the interactions between the ceramics and Ag. Temperature-humidity-bias (THB) tests on Ag-doped disc specimens revealed that the failure rate of the specimens increased with the Ag content in the ceramics. Based on these results, it was inferred that the deterioration of the multilayer ceramic capacitors with the increase of Ag content in the electrodes should be attributed to the Ag diffusion from the electrodes into the oxide ceramics.     

电容型直流断路器拓扑结构研究

高压直流断路器是多端直流输电及直流电网技术中的核心设备之一。文中对现有的各类电容型直流断路器进行了比较分析,指出了各类电容型断路器方案的优缺点及其应用场合;在此基础上,提出了一种基于预充电电容的组合式直流断路器方案;在详细描述了所提方案的拓扑结构、工作原理及控制策略后通过在PLECS中搭建三端环网模型对其可行性和有效性进行了验证;最后指出了电容型直流断路器未来的研究方向和需要解决的问题。     

特高压串补线路沿线电压分布及串补布置方案研究

提出一种基于传输线理论的特高压串补输电线路电压分布的快速算法。首先,将线路的传输参数矩阵转化为两端口节点导纳矩阵,得到∏型等值模型集总参数。然后将其填入潮流计算软件,对目标电网进行潮流计算。再将计算的结果作为末端边界条件,用传输参数矩阵就可快速得出线路上的电压分布。该算法可精确计算特高压串补线路的沿线电压分布情况,而且还可以计及线路两侧的无功补偿能力,工程适用性很强。最后,还从理论上研究特高压串补的集中／分散布置方案以及串补和高压电抗的相对布置位置,指出高压电抗位于母线侧且串补分散布置的方案比高压电抗位于线路侧且串补集中布置的方案更有利于抑制工频稳态过电压,为特高压输电工程规划给出了指导性建议。     

Luminescence Characteristics of YAG Glass–Ceramic Phosphor for White LED

Luminescence characteristics of Ce:Y₃Al₅O₁₂ (YAG) glass-ceramic (GC) phosphor for a white LED were investigated. The GC phosphor was obtained by a heat treatment of a Ce-doped SiO₂-Al₂ O₃-Y₂O₃ mother glass between 1300degC and 1500degC for the prescribed time period. The quantum efficiency (QE) of Ce³⁺ fluorescence in the GC materials, the color coordinate, and the luminous flux of electroluminescence of LED composite were evaluated with a blue LED (465 nm) set in an integrating sphere. The QE increased with increasing ceramming temperature of the as-made glass. The color coordinates (x, y) of the composite were increased with increasing thickness of the GC mounted on a blue LED chip. The effect of Gd₂O₃ substitution on the optical properties of the GC materials was also investigated. The excitation and emission wavelengths shifted to longer side up to Gd/(Y + Gd) = 0.40 in molar composition. As a result, the color coordinate of the LED with GdYAG-GC of various thickness shifted to closer to the Planckian locus for the blackbody radiation. These results were explained by partial substitution of Gd³⁺ ions in the precipitated YAG microcrystals, leading to the increase of lattice constant of unit cell, which was confirmed by XRD.     

Thermal and Mechanical Analysis of High-Power LEDs With Ceramic Packages

In this paper, we present the thermal and mechanical analysis of high-power light-emitting diodes (LEDs) with ceramic packages. Transient thermal measurements and thermomechanical simulations were performed to study the thermal and mechanical characteristics of ceramic packages. Thermal resistances from the junction to the ambient were decreased from 79.6 to 46.7degC/W by replacing the plastic mold with a ceramic mold for LED packages. Thermomechanical stress induced in the heat-block test was simulated using a finite-element method. Higher level of thermomechanical stress in the chip was found for LEDs with ceramic packages, despite less mismatching coefficients of thermal expansion, compared with that with plastic packages. The thermomechanical-stress components in the direction of the thickness were found to be larger than that in other two directions. The results suggest that the thermal performance of LEDs can be improved by using ceramic packages, but the mounting process of the high-power LEDs with ceramic packages is critically important and should be the reason for causing delaminating interface layers in the packages.     

XPS Studies of PZT Films Deposited by Metallic Lead and Ceramic PZT Dual Target Co-Sputtering

The dependence of the chemical states of the constituent elements of a PZT thin film prepared by RF magnetron co-sputtering using ceramic PZT and metallic Pb dual target materials on the Ar⁺ etching time was studied using XPS. The metallic Pb, lead oxide and Pb in PZT led to the different binding energies of the Pb lines. The intensity of binding energy of metallic Pb relative to that of bulk Pb increased with the depth of the film. The peak position and the line shape of the O_1s electron was associated with the different binding energies of oxygen, which interacts with Pb and Ti and Zr atoms to form the metal oxides, and the softening of the O_1s bonds by the bonding interaction in Ti–O, Zr–O and Pb–O. The broad Ti_2p3/2 line in the PZT film could has been associated with the various charge state of Ti and no spectral changes of Ti_2p and Zr_3d were observed as the Ar⁺ ion sputtering time was increased.     

电感耦合等离子体发射光谱法测定陶瓷制品中铅、镉迁移量的不确定度评定

对电感耦合等离子体发射光谱法测定陶瓷制品中铅,镉迁移量的不确定度进行评定,分析不确定度的主要来源,评估检测过程中不确定度分量。检测结果的不确定度主要来源于测量重复性和标准曲线的非线性。     

Design Optimization of Wind Power Planning for a Country With Low–Medium-Wind-Speed Profile

The emerging energy crisis resulting from a high price of crude oil has drawn attention about renewable energy all over the world. Thailand is a developing country located at the heart of Southeast Asia, with about 66 million of population as of 2006. The electricity supply industry structure under the government of Thailand has been managed by the Electricity Generating Authority of Thailand, the Metropolitan Electricity Authority, and the Provincial Electricity Authority for almost 50 years. According to the 2004 Power Development Plan, the country would have generation reserve at a marginal of 15%. Due to the rapid economic growth and difficulty in building new centralized generating facilities, this has the potential to create a security issue of electricity energy shortage and may develop a severe system blackout. Renewable energy issues have been widely discussed and debated over the country. Although solar energy is the most prominent renewable energy source due to the appropriate geographic of Thailand, it is still considered as a low-density energy source which requires a large area of installation. Therefore, for the long-term investment, wind power seems to be a good candidate because it is quick to install, needs no fuel cost, and is environment friendly. Therefore, this paper investigates the impact of the penetration level of wind power generation to be integrated into the Thailand system. System stability has been observed in various system configuration changes due to different control strategies of wind farms. The economic analysis of wind-farm investment has been also considered.      

多层均压结构可加工陶瓷真空沿面耐电特性的实验与仿真研究

真空中沿固体绝缘材料表面的闪络电压通常远低于绝缘材料自身及相同长度真空间隙的击穿电压,这一现象极大地限制了高压真空设备的发展。将一种具有优良可加工性能和良好耐电性能的可加工陶瓷引入真空绝缘领域,结合工程实际中的绝缘堆结构,加工制作了多层均压结构;在纳秒脉冲电压下对不同多层均压结构的样品进行了真空沿面耐电性能的测试,并分析了不同均压结构对样品沿面电场和电子运动轨迹的影响。结果表明：多层均压结构样品的耐压强度要高于圆柱形样品,且其闪络场强随着绝缘层与金属层比例的增大有增大的趋势,径向电场随该比例的增大而减小;使用圆台形绝缘子组成多层均压绝缘结构时,电子难以与样品表面发生碰撞,闪络的稳定性得到了一定程度的提高。     

Generation and classification of Kerwin–Huelsman–Newcomb circuits using the DVCC

New circuits realizing the Kerwin–Huelsman–Newcomb (KHN) and using three or four differential voltage current conveyor (DVCC) are generated from the basic KHN and inverted KHN block diagrams. The circuits are classified into two types, type A employs three DVCC and type B employs four DVCC. Each type includes four classes of circuits depending on the four possible integrator polarities. Each class can be realized by several circuits as will be demonstrated in the paper. All the eight possible sign combinations of the output voltages polarities are obtainable from the two types; four sign combinations from each type. The eight block diagrams are included to demonstrate the difference between each class of circuits. Spice simulation results demonstrating the practicality of the proposed filters are included. Copyright © 2008 John Wiley & Sons, Ltd.     

Structure,Ferroelectric, Dielectric and Energy Storage Studies of Ba0.70Ca0.30TiO3, Ba(Zr0.20Ti0.80)O3 Ceramic Capacitors

Ba_0.70Ca_0.30TiO₃-(BCT),Ba(Zr_0.2Ti_0.8)O₃-(BZT) ceramics were fabricated by conventional mixed oxide route to develop inorganic dielectric materials suitable for use as an insulator with high dielectric constant and low energy loss for capacitor applications. The structural phase transition, ferroelectric, dielectric and energy storage properties of BCT, BZT ceramic capacitors were investigated. Room temperature X-ray diffraction (XRD) patterns revealed prominent peaks corresponding to tetragonal perovskite crystal structure for both BCT, BZT solid solutions. Slim ferroelectric hysteresis (P-E) loops were observed for BCT, BZT solid solutions. Temperature dependent dielectric property measurements of BCT, BZT solid solutions have shown a high dielectric constant and low dielectric loss. Room temperature (300K) breakdown field strength and energy densities were obtained from the integral area of P-E loops. For the BCT ceramics, the largest recoverable energy (unreleased energy) density is 1.41 J/cm³ with dielectric breakdown strength as high as 150 kV/cm. For the BZT ceramics, the largest recoverable energy (unreleased energy) density is 0.71 J/cm³ with dielectric breakdown strength as high as 150 kV/cm. Bulk BCT, BZT ceramics have shown interesting energy densities; these might be the strong candidate materials for capacitor applications.     

Interfacial electrostatic phenomena and capacitance–voltage characteristics of ultrathin polyimide Langmuir–Blodgett films

Capacitance–voltage (C–V) characteristic of ultrathin polyimide (PI) Langmuir–Blodgett (LB) films is discussed theoretically and experimentally taking into account the interfacial electrostatic phenomena and interfacial electronic states at the metal/PI LB film interface. It was found that the apparent film thickness decreases due to the charge exchange phenomena at the metal/film interface. It was also found that electrical insulating properties of the Au/PI LB film/Al device depended on the polarity of external voltage, probably due to the formation of the electrostatic interfacial electric field of 10⁸ to 10⁹ V/m. © 2000 Scripta Technica, Electr Eng Jpn 134(3): 9–15, 2001     

Evaluation of Head Orientation and Neck Muscle EMG Signals as Command Inputs to a Human–Computer Interface for Individuals With High Tetraplegia

We investigated the performance of three user interfaces for restoration of cursor control in individuals with tetraplegia: head orientation, electromyography (EMG) from face and neck muscles, and a standard computer mouse (for comparison). Subjects engaged in a 2-D, center-out, Fitts' Law style task and performance was evaluated using several measures. Overall, head orientation commanded motion resembled mouse commanded cursor motion (smooth, accurate movements to all targets), although with somewhat lower performance. EMG commanded movements exhibited a higher average speed, but other performance measures were lower, particularly for diagonal targets. Compared to head orientation, EMG as a cursor command source was less accurate, was more affected by target direction and was more prone to overshoot the target. In particular, EMG commands for diagonal targets were more sequential, moving first in one direction and then the other rather than moving simultaneous in the two directions. While the relative performance of each user interface differs, each has specific advantages depending on the application.      

IEC 60384-14:2013中抑制电源电磁干扰用电容器的分类及电气安全测试方法介绍

本文详细介绍了标准IEC 60384-14:2013中抑制电源电磁干扰电容器的分类及涉及电气安全的测试项目,强调了抑制电源电磁干扰用电容器在电气安全上的重要性,为企业选用电容器提供指引。     

Systematic Study of the Dopant-Dependent Properties of Electrically Programmable Fuses With Silicided Poly-Si Links Through a Series of I– V Measurements

Electrically programmable/writable fuses (e-fuses) with a Ni-silicided polycrystalline silicon narrow link and fabricated with four doping conditions were studied using two successive I-V measurements. The initial I-V sweeps can change e-fuses into targeted programmed states and display all of the programming processes where the currents change by many orders of magnitude. The second set of I-V curves can show stability and conduction in the programmed states for both bias polarities. Through the series of I-V measurements, the two-step programming with moderate blowing conditions could be reproduced and studied systematically. The programming processes of incompletely programmed states, before complete programming (CP), were found to be strongly dependent on the dopant conditions. The origin of the dopant dependency was considered within a simple electrical equivalent circuit model. At least two or three programmed states were identified among the completely programmed states in terms of the characteristic spreads of the final resistance and conduction behavior. The most distinctive currents after CP are similar to those in varistors. The stability of every programmed state is strongly dependent on the dopant conditions.     

Non‐invasive chaos control of DC–DC converter and its optimization

The frequency‐domain‐based realization condition related to a novel non‐invasive chaos control is presented in this paper. According to the common piecewise‐linear characteristics of PWM‐controlled DC–DC converter system, a general expression for its Jacobian matrix is derived for optimizing the control parameters of the proposed non‐invasive chaos control. The relevant simulation and experiment results about the application of the chaos control to a voltage‐mode Buck converter are given, which confirm the feasibility of the parameter‐optimization method and the validity of the proposed non‐invasive chaos control. Copyright © 2010 John Wiley & Sons, Ltd.     

Strain–magnetization properties and domain structures of silicon steel sheets

The effects of tensile stress and strain on magnetization and magnetic domains in silicon steel sheets were investigated. In the elastic deformation region, magnetization decreased with an increase in strain, while in the plastic deformation region, strain–magnetization properties under stress showed a peculiar characteristic, namely, an increase of magnetization when strain was decreased. We observed lancet and other domains in the specimens after removing the stress applied in the plastic deformation region, especially near grain boundaries. This phenomenon can be explained by changes in the domain structures, which were observed in this study. The features observed in this investigation can be applied to the nondestructive detection of fatigue in metal magnetic materials. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 10–17, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20002