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1.
Polycrystalline Ni-Zn ferrites with a well-defined composition of Ni0.4Zn0.6Fe2-xSbxO4 synthesized using sol–gel method. Morphological characterizations on the prepared samples were performed by high resolution transmission electron and field emission scanning electron microscopy. The powders were densified using microwave sintering method. The room temperature complex permittivity (ε′ and ε″) and permeability (μ′ and μ″) were measured over a wide frequency range from 1 MHz–1.8 GHz. The real part of permittivity varies as ‘x’ concentration increases and the resonance frequency was observed at much higher frequencies and there is a significant decrease in the loss factor (tanδ). The electrical resistivity and permeability of NiZn ferrites increased with an increase of Sb content. As the concentration of ‘x’ increases from 0 to 0.08 the saturation magnetisation decreases. The saturation magnetization (Ms)?≈?52.211 A.m2/Kg for x?=?0 at room temperature. The room temperature electro paramagnetic resonance (EPR) were studied. 相似文献
2.
ABSTRACTThe spinel Ni0.7Zn0.3RE0.04Fe1.96O4 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 Ni0.7Zn0.3RE0.04Fe1.96O4 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 Ni0.7Zn0.3RE0.04Fe1.96O4 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 Ni0.7Zn0.3RE0.04Fe1.96O4 ferrites decrease and increase, respectively. The microwave-absorbing properties are better for RE-substituted Ni-Zn ferrites than Ni-Zn ferrites. For Ni0.7Zn0.3Ce0.04Fe1.96O4 ferrites, the minimum loss is ?12.5 dB at 18 GHz for an absorber thickness of 2 mm. 相似文献
3.
Hideo Saotome Shun Kuwahara 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(5):556-560
Ferrite cores are used for power electronics circuits operating under excitation conditions of frequency ranging from hundreds of kilohertz to several tens of megahertz. Development of a mathematical model enabling the estimation of the power loss of ferrites in high‐frequency regions, contributes to the designing of power circuits. The power loss in high‐frequency regions consists of hysteresis and dynamic magnetic losses. Although hysteresis loss does not depend on the excitation frequency, the dynamic magnetic loss increases with increasing excitation frequency. The dynamic magnetic loss parameter, λf, has been introduced for identifying the power loss in high‐frequency regions. In this study, λf − dB/dt characteristics are experimentally obtained by a newly introduced hysteresis model that uses a normal distribution function. It is found that the λf − dB/dt characteristics do not depend on the size of B − H loops. The instantaneous power loss of a ferrite core in the high‐frequency region can be calculated using the λf − dB/dt characteristics. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
4.
It is a well known fact that piezoelectric band-stop filters manifest not only the desired stopband at the fundamental resonant frequency of the crystal, but also additional stopbands at its spurious resonant frequencies. The greater the degree to which such parasitic attenuation peaks are to be suppressed, the more complex is the required circuitry. The most common crystal band-stop filter circuits can be considered as all-pass sections in which a capacitance is ‘disturbed’ over a narrow bandwidth by a resonant circuit. If this ‘disturbance’, possibly after conversion by means of known one-port equivalents, consists of a high impedance series resonant circuit with the inductance Ls in parallel to the entire lattice arm R/jx1, the 3 dB bandwidth of the stopband becomes Δω0= R/Ls(1+x) in the loss-free case. Sometimes the dual representation of the ‘disturbance’ is more appropriate. With a finite crystal Q-factor of Qq, the insertion loss of a desired or parasitic stopband assumes the finite maximum value ǎ ~ In (1+QqΔω0/ω∞). The width and height of the possible attenuation peaks are given in formulas, normalized curves and worked examples for seven band-stop filter circuits of increasing complexity, each with a single crystal. 相似文献
5.
采用传统氧化物陶瓷工艺制备NiCuZn铁氧体。利用扫描电子显微镜、阻抗分析仪、磁滞回线分析仪,分别对样品的微观形貌、复数磁导率频谱、静磁性能和高频功耗进行了观察和测试。结果表明,在0~0.12wt%的范围内,随Co2O3添加量的增大,样品的平均晶粒尺寸略有减小,起始磁导率逐渐下降,截止频率逐渐升高。在3MHz、10m T、25~140℃条件下,随着Co2O3添加量的增加,由于截止频率逐渐升高,磁导率虚部在高频下得到抑制,剩余损耗降低,导致磁芯功率损耗单调减小。 相似文献
6.
Mukesh C. Dimri Subhash C. Kashyap D. C. Dube S. K. Mohanta 《Journal of Electroceramics》2006,16(4):331-335
NiCuZn ferrite has recently attracted a lot of attention for its application in high frequency (up to a few GHz) multilayer
chip inductors (MLCIs) and for other microwave devices owing to their favorable electromagnetic properties and low densification
temperature. In order to study the effect of substitution of cations by cobalt in small concentration on the dielectric and
magnetic properties at low and high frequencies, bulk polycrystalline ferrite samples of starting composition (Ni0.2Cu0.2Zn0.6)1 − x
Co
x
Fe2O4, having x = 0, 0.01, 0.03 and 0.05, were prepared by citrate precursor method. Pure spinel (cubic) ferrite formation was confirmed
by powder X-ray diffraction technique. Complex permittivity and permeability were measured at microwave frequencies (X-band)
using the cavity perturbation method, which is a non-contact method. The values of real part of permittivity (ε ′) vary in
the range 7–9.6 and of the imaginary part (ε ″) vary from 0.020–0.120, whereas real part of the permeability (μ′) lies in
the range 2.6–14.0 and the imaginary part of permeability (μ″) varies from 0.5–6.0. It is observed that there is an increase
in μ′ and decrease in the magnetic loss (tan δ μ) on increasing the cobalt concentration from x = 0 to x = 0.05. The variation of these parameters, both with frequency in X-band and with the cobalt concentration, is discussed
in this paper. 相似文献
7.
Dr. ing. P. Rolicz 《Electrical Engineering (Archiv fur Elektrotechnik)》1976,58(6):333-338
Contents In this paper the inner impedance and the electrodynamic force acting on a cylindrical conductor partly filling a semi-closed slot are calculated. The investigations are made by using the separation of variables method.
Symbole A z-component of the vector potential (complex r.m.s. value) - B x, By components of the magnetic induction (complex r.m.s. value) - F electrodynamic forece - I current (r.m.s. value) - I n(z) modified Bessel function of first kind - imaginary unit - J z-component of the current density (complex r.m.s. value) - L(o) inductance for direct current - R resistance - X reactance - Z impedance - z * conjugate complex number ofz - Rez, Imz, |z| real part, imaginary part and modulus of complex numberz - 0 magnetic permeability - pulsation - Kronecker symbol - 1 atn=m o otherwise 相似文献
Übersicht Es werden die innere Impedanz und die elektrodynamische Kraft, die auf einen kreisförmigen Leiter wirkt, der eine halbgeschlossene Nut partiell ausfüllt, berechnet. Zur Berechnung wird die Methode der Trennung der Variablen angewendet. Die Ergebnisse sind in Kurvenform dargestellt.
Symbole A z-component of the vector potential (complex r.m.s. value) - B x, By components of the magnetic induction (complex r.m.s. value) - F electrodynamic forece - I current (r.m.s. value) - I n(z) modified Bessel function of first kind - imaginary unit - J z-component of the current density (complex r.m.s. value) - L(o) inductance for direct current - R resistance - X reactance - Z impedance - z * conjugate complex number ofz - Rez, Imz, |z| real part, imaginary part and modulus of complex numberz - 0 magnetic permeability - pulsation - Kronecker symbol - 1 atn=m o otherwise 相似文献
8.
9.
The measurement of the iron loss in ferrites is important for developing high‐efficiency switching power supplies. The authors have proposed the dynamic magnetic loss parameter, λf, for evaluating the iron loss in ferrites. In previous studies, the parameter was assumed to be a constant value for an individual ferrite material and defined for one period of a small B–H loop. In this paper, assuming that λf is a function of the time derivative of the magnetic flux density, dB/dt, a novel measurement method of λf of a Ni‐Zn ferrite is proposed using rectangular wave voltage excitation and the Fourier expansion of the exciting current. In order to realize an iron loss measurement system with the rectangular wave voltage excitation, a high‐frequency FET inverter has been developed. The results of measuring λf show that it is uniquely determined by dB/dt regardless of the B–H loop size. The measured dB/dt characteristics of λf are applied to practical examples for switching power supplies and sinusoidal wave voltage excitations. Their experimental and computational results coincide and it is clarified that the measured dB/dt characteristics are effective and useful. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 1–6, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20101 相似文献
10.
Kazuhiro Umetani Keisuke Yagyu Eiji Hiraki 《IEEJ Transactions on Electrical and Electronic Engineering》2016,11(Z2):S84-S90
Gallium nitride field‐effect transistors (GaN‐FETs) are attractive devices because of its low on‐state resistance and fast switching capability. However, they can suffer from false triggering caused by fast switching. Particularly, a disastrous oscillation of repetitive false triggering can occur after a turn‐off, which may deteriorate the reliability of power converters. To address this issue, we give a design guideline to prevent this phenomenon. We analyze a simple circuit model to derive the condition of occurrence of this phenomenon, which is then verified experimentally. Results show that the parasitic inductance of the gating circuit, Lg, and that of the decoupling circuit, Ld, should be designed so that the LC resonance frequency of Lg and the gate–source capacitance of the GaN‐FET does not coincide with that of Ld and the drain–source capacitance, respectively. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
11.
M. Penchal Reddy W. Madhuri N. Ramamanohar Reddy K. V. Siva Kumar V. R. K. Murthy R. Ramakrishna Reddy 《Journal of Electroceramics》2012,28(1):1-9
The effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported. The spinel
ferrite system Ni1-xZnxFe2O4 with x = 0.2, 0.3, 0.4 and 0.5 was prepared by microwave sintering method. The uniaxially pressed samples were sintered at
various temperatures such as 900°C, 1000°C and 1100°C for 30 min. X-ray diffraction patterns of the samples indicate the formation
of single-phase cubic spinel structure. SEM micrographs show that grain size increases with increasing zinc content and sintering
temperature. The elemental composition of these ferrites was analyzed by EDS. Lattice constant increases with increase in
zinc content, obeying Vegard’s law. The effect of composition and sintering temperature on initial permeability as the function
of frequency and temperature was studied. The initial permeability of NiZn ferrite increases greatly with increasing Zn content
and sintering temperature. The dependence of initial permeability with respect to temperature shows the decrease in the Curie
point with increase in zinc content, is the normal behavior of ferrites. The relative loss factor (tand