Complex permeability of polycrystalline Mn-Zn and Ni-Zn ferrites

The complex permeability of ferrites is frequency dependent. The real part of the complex permeability deteriorates in a high frequency range and the imaginary part has a peak after starting the deterioration. This paper examines the possibility that the frequency characteristics for some ferrites can be approximately derived from a first-order linear differential equation for the magnetic field intensity and magnetic flux density. The first-order differential equation is expressed by the reciprocal of the complex permeability and provides first-order magnetic and electric circuits for ferrite cores. In contrast with the commonly used series R_s-L_s, circuit for the cores, obtained from B = (μ′ − jμ′)H, the first-order electric circuit derived consists of an inductance (L) and resistance connected in parallel. In this paper, it is demonstrated that the inductance L remains constant, whereas Ls decrease with the increase in frequency. In other words, the real part of the reciprocal of the complex permeability remains constant for an increase in frequency. In addition, it is found that the imaginary part of the reciprocal of the complex permeability is approximately proportional to the frequency. © 1998 Scripta Technica, Electr Eng Jpn, 123(2): 1–7, 1998     

Synthesis and characterization of rare-earth elements substituted Ni-Zn ferrites

ABSTRACT

The spinel Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites with RE?Ce and Y are fabricated by the polyacrylamide gel method. The effect of rare earth ions substitution for iron ions on the structure, morphology, electromagnetic and microwave-absorbing properties of Ni-Zn ferrites are investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric and differential thermal analysis (TG-DTA) and HP8510B network analyzer, respectively. The results indicate that Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites form a pure cubic spinel structure, and Ce³⁺ and Y³⁺ substitute into the crystal lattice. Both the real ?′ and imaginary ?″ parts values of complex permittivity for Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites are higher than those for Ni-Zn ferrites in X-band (8.2-12.4 GHz) frequency range. When RE ions substitute for iron ions, the real μ′ and imaginary μ″ parts values of complex permeability for Ni_0.7Zn_0.3RE_0.04Fe_1.96O₄ ferrites decrease and increase, respectively. The microwave-absorbing properties are better for RE-substituted Ni-Zn ferrites than Ni-Zn ferrites. For Ni_0.7Zn_0.3Ce_0.04Fe_1.96O₄ ferrites, the minimum loss is ?12.5 dB at 18 GHz for an absorber thickness of 2 mm.     

La-Zn取代对六角型锶铁氧体的显微结构及磁性能的影响

采用固相反应法制备Sr_(1-x)La_x Fe_(11.8-x) Zn_x O_(19)(0≤x≤0.42)M型六角铁氧体磁粉和磁体。X射线衍射(XRD)分析表明,La-Zn取代量x在0~0.42范围内磁粉是单一的磁铅石型相。磁体的FESEM观察表明,不同La-Zn取代量的磁体形成了均匀的六角片状结构。随La-Zn取代量的增大,磁体的剩磁B_r和最大磁能积(BH)_(max)先增后降,最大值对应的取代量为0.3,而其内禀矫顽力H_(cj)和磁感应矫顽力H_(cb)则单调下降。     

Microstructural and piezoelectric properties of PZN substituted PMN-PZT ceramics for multilayer piezoelectric transformer

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformers, Pb[(Mn_1/3,Nb_2/3)_0.07(Zn_1/3Nb_2/3)_a (Zr_0.48Ti_0.52)_1-0.07-aO₃] ceramics were prepared with the variations of PZN from 2 to 14 mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 940 to 1000^∘C. At 8 mol% PZN substituted specimen sintered at 970^∘C, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant(d₃₃) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N], respectively, for multilayer piezoelectric transformer application.     

影响热电池用矿物二硫化铁热稳定性的因素

研究了热电池正极材料常用的矿物二硫化铁粉末的特性。通过扫描电子显微镜法(SEM,Scanning Electron Microscope)形貌观察、等离子体能谱分析方法(ICP,Inductively Coupled Plasma)杂质成分分析、粒度分布测试、X射线衍射法(XRD,X-ray Diffraction)物相分析、热重分析法(TGA,Thermo Gravimetric Analysis)等分析测试手段,分别从矿物二硫化铁粉末中的杂质、粒度分布、以及矿源产地等几个方面出发,讨论了影响矿物二硫化铁粉末热稳定性的因素。结果得出影响矿物二硫化铁热稳定性的主要因素是可在酸中溶解的杂质;粒度分布对矿物二硫化铁粉末热稳定性的影响较小,是次要因素;不同矿源的二硫化铁矿石粉末并不能显著影响矿物二硫化铁的热稳定性,为次要因素。经酸液洗涤、纯化处理工艺后,矿物二硫化铁的热稳定性几乎提高了85℃,换言之,用该种工艺材料生产的热电池的工作温度区间拓宽了85℃,能有效地提高热电池的性能。     

La-Co取代钙铁氧体制备及优越性

采用陶瓷法,使用La、Co分别取代部分Ca和Fe,制成以分子式Ca_(1-x-x')LaxSr_(x')Fe_(2n-y)Co_yO_(19)(x,x',y和n分别满足关系式:0.2≤x≤0.7,0≤x'≤0.3,0≤y≤0.5和4.5≤n≤6.0)为主相的六方晶系铁氧体。采用该铁氧体制备的磁体其Br/G+1/3H_(cj)/Oe在6200以上。磁性能为:剩磁B_r=449 m T,矫顽力H_(cb)=339 k A/m,内禀矫顽力H_(cj)=424 k A/m,最大磁能积(BH)max=39.2 k J/m~3。相比La-Co取代各向异性锶铁氧体,La-Co取代各向异性钙铁氧体在磁性能上表现出明显的优越性。     

Design and analysis of thick-film integrated inductors for powerconverters

This paper describes the design procedures followed to obtain a thick-film inductor for its application in DC/DC power microconverters. The main characteristics of the new technology used are commented upon and design equations are given. Results are compared to those obtained by means of finite-element analysis tools. Details of some thick-film inductors developed with this technique (within the framework of the IMPASS Esprit Project (number 23910), financed by the European Community) are also given. The inclusion of one of these inductors in a 5-to-3.3-V DC/DC converter contributes to obtaining a very high power density: 6.25 W/cm³     

掺杂Co、Zn、Y氢氧化亚镍的合成与性能

采用均匀沉淀法制备了掺杂钴、锌、钇高比表面氢氧化亚镍,对该材料进行了SEM、XRD等结构测试及分析。测试了采用该氢氧化亚镍材料的氢镍电池性能。所制备的氢氧化亚镍为α-Ni(OH)2和β-Ni(OH)2的混合物,颗粒粒径为亚微米级。将该材料掺杂在普通球形氢氧化亚镍中作为碱性二次电池的正极材料制成氢镍电池,电池在容量、高功率性能、高温性能等方面都有所提高。     

用于高磁导率MnZn软磁铁氧体的高纯Fe2O3性能分析与比较

采用当前电子材料领域先进的分析仪器和分析方法,对应用于MnZn高磁导率软磁铁氧体的几种高纯氧化铁的纯度、杂质、比表面积、粒度大小及分布、微观形貌等进行了详尽的分析和比较.并用这几种高纯氧化铁分别制备预烧料和高磁导率软磁铁氧体,对预烧料的物相组成和铁氧体的电磁性能进行了对比分析.     

热电池薄膜组件制备及其应用现状

轻型化是武器系统未来的发展趋势,这对作为军用电源的热电池而言也是非常重要的发展方向。在保证比能量的前提下,热电池的尺寸越小越好。热电池薄膜组件能有效地缩小热电池体积,提高比能量,是热电池小型化设计的发展方向之一。综述了热电池薄膜组件主要的制备方法和应用现状,并对薄膜组件的发展方向进行了展望。     

Dielectric behavior of hexagonal and orthorhombic YFeO3 prepared by modified sol-gel method

Polycrystalline YFeO₃ ceramic powders were synthesized by modified polyacrylamide sol-gel method. X-ray diffraction analysis demonstrated that the crystal structures of YFeO₃ could be controlled from hexagonal phase (h-YFeO₃) to orthorhombic phase (o-YFeO₃) through the calcined temperature. Temperature-dependent dielectric constants (ε _r) and losses (tanδ) show that strong frequency dispersion phenomena occur in whole measuring temperature. Both the h-YFeO₃ and o-YFeO₃ exhibit dielectric relaxation behavior at T?<?250 K and at T?>?340 K, which could be attributed to thermal activation. Whereas, only h-YFeO₃ shows an anomaly dielectric peak at T _m ?=?297 K fitted with Curie-Weiss law and modified Curie-Weiss law, indicating a possible P6 ₃ mc-P6 ₃ cm transition with slightly diffuse characteristics.     

Preparation and properties of borosilicate glass-coated Cu powder for internal electrode of multilayer ceramic device

In this study, a process was proposed which allows a base metal electrode to be burnt-out in an oxidative atmosphere for fabrication of multilayer ceramic device. To protect Cu in an oxidative atmosphere, the Cu powder was coated with borosilicate glass via a sol-gel process. The oxidation resistance and shrinkage of the glass-coated Cu were investigated. When a 10% glass-coated Cu was heated up to 500°C under an oxidative atmosphere, the Cu could survive without formation of copper oxide. The oxidation of the Cu was observed when heating at temperatures above 700°C. This might be due to exposure of Cu to oxidative atmosphere related to softening behavior of glass. The glass-coated Cu exhibited a shrinkage behavior which follows the shrinkage behavior of glass in the low temperature range and the shrinkage of pure Cu in the high temperature range. To measure the electrical conductivity of the glass-coated Cu electrode, the Cu pastes were prepared and printed onto alumina substrate. The binder-burn-out process of the glass-coated Cu was carried out at 550°C under an air atmosphere, and was then sintered at 1000°C under a nitrogen atmosphere. The electrical conductivity of the Cu electrode measured was above 10⁴ /Ωcm which means that it can be used as the internal electrode of a multilayer device.     

添加Bi_2O_3与玻璃对NiCuZn铁氧体磁导率及其温度特性的影响

采用传统陶瓷工艺制备了NiCuZn铁氧体材料,研究了添加Bi2O3、玻璃对NiCuZn铁氧体材料的磁导率及其温度稳定性和居里温度的影响。研究表明,单独添加Bi2O3时,随着Bi2O3添加量的增加,磁导率先升后降,磁导率的温度系数αμ呈负值且绝对值增大,居里温度TC几乎不变;复合添加等量Bi2O3和玻璃时,磁导率下降,随温度的变化不明显,居里温度TC随添加量增大而先升后降,但添加后的TC均高于不添加的。适量添加Bi2O3、玻璃可以改善材料的温度稳定性。     

热电池用正极-电解质一体化复合薄膜的制备及性能研究

面向新一代小型化轻量化武器装备对热电池电源的实际需求,通过流延涂布工艺制备了正极-电解质一体化复合薄膜极片.所制备的一体化薄膜具有良好的机械强度,极片厚度仅为180 mm,远小于传统粉末压片工艺制得极片的厚度.将一体化薄膜极片与锂硼负极组装成单体电池进行放电,放电结果表明,在100 mA/cm2的电流密度下,450℃时...     

预烧、烧结及预处理对Z型六角铁氧体结构与性能的影响

用固相反应法制备了(Ba3Co2Fe24O41) Z型六角铁氧体材料.对烧成过程(预烧温度、烧结温度及保温时间、降温方式)及预处理工艺进行了研究.提出了制备该类材料的理想工艺条件,即适当延缓预烧升温速度、降低烧结温度、缩短保温时间、控制合理的降温方式可使材料性能明显改善.     

Redox behavior and electrical properties of Sr and Zr substituted BaTiO3

The oxidation and reduction behavior of Sr and Zr substituted BaTiO₃ has been studied by measuring equilibrium electrical conductivities as a function of oxygen activity. The substitution of Sr⁺² and Zr⁺⁴ for Ba²⁺ and Ti⁴⁺ in BaTiO₃ shifted the conductivity profiles to lower oxygen partial pressures. The replacement of Ba with smaller Sr ions suppresses the oxygen dissociation from the lattice, consequently increasing the enthalpy for reduction (ΔH _n ), whereas the Sr substitution requires less energy for oxidation (ΔH _p ). The increase in reduction enthalpy at lower oxygen activities suppresses the formation of oxygen vacancies, the materials becoming resistant to reduction process. Such a reduction resistant behavior gave rise to greater electrical resistivities for (Ba_0.9Sr_0.1)(Ti_0.9Zr_0.1)O₃ than for Ba(Ti_0.9Zr_0.1)O₃ when the samples were sintered at lower P(O₂).     

电网输电断面动态热稳定限值在线计算方法

提出了一种利用实时气象环境和电网运行方式进行稳定断面功率限值在线计算方法,将静态的稳定断面限值转变为根据实时数据变化的动态限值,为电网精益化调控提供支撑。基于动态增容技术将外部系统的微气象数据接入调控系统进行线路动态载流量计算。基于电网模型和实时运行方式,采用支路开断分布因子计算输电断面的潮流动态转移比。基于节点对支路的功率转移分布因子实时分析稳控装置动作对开断后输电断面潮流的影响,对断面限值进行动态修正。提出的方法在南京地区调控系统进行了在线应用,基于实际运行数据对结果进行验证,证明了算法对于高峰时段提升断面输送能力的有效性。     

锂离子电池有机电解液热稳定性研究

从有机电解液自身热稳定性以及电极／有机电解液相互作用的热稳定性两个方面综述了锂离子电池有机电解液的热稳定性;认为,正极／有机电解液的反应对锂离子电池安全性的影响是最主要因素。并分别从抑制LiPF6分解、使用不燃或阻燃溶剂阐述了改善有机电解液热稳定性的方法。     

Oxygen permeability, stability and electrochemical behavior of \Pr _{2} {\text{NiO}}_{{4 + \delta }} -based materials

The high-temperature electronic and ionic transport properties, thermal expansion and stability of dense $ \Pr _{2} {\text{NiO}}_{{4 + \delta }} ,\Pr _{2} {\text{Ni}}_{{0.9}} {\text{Fe}}_{{0.1}} {\text{O}}_{{4 + \delta }} $ and $ \Pr _{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ ceramics have been appraised in comparison with K₂NiF₄-type lanthanum nickelate. Under oxidizing conditions, the extensive oxygen uptake at temperatures below 1073–1223 K leads to reversible decomposition of Pr₂NiO₄-based solid solutions into Ruddlesden–Popper type Pr₄Ni₃O₁₀ and praseodymium oxide phases. The substitution of nickel with copper decreases the oxygen content and phase transition temperature, whilst the incorporation of iron cations has opposite effects. Both types of doping tend to decrease stability in reducing atmospheres as estimated from the oxygen partial pressure dependencies of total conductivity and Seebeck coefficient. The steady-state oxygen permeability of $ \Pr _{2} {\text{NiO}}_{{4 + \delta }} $ ceramics at 1173–1223 K, limited by both surface-exchange kinetics and bulk ionic conduction, is similar to that of $ {\text{La}}_{2} {\text{NiO}}_{{4 + \delta }} $ . The phase transformation on cooling results in considerably higher electronic conductivity and oxygen permeation, but is associated also with significant volume changes revealed by dilatometry. At 973–1073 K, porous $ \Pr _{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ electrodes deposited onto lanthanum gallate-based solid electrolyte exhibit lower anodic overpotentials compared to $ {\text{La}}_{2} {\text{Ni}}_{{0.8}} {\text{Cu}}_{{0.2}} {\text{O}}_{{4 + \delta }} $ , whilst cathodic reduction decreases their performance.