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The effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported. The spinel ferrite system N i1-xZn xFe 2O 4 with x0 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 (δ/μ i of the order of 10 -2 to 10 -5 in the frequency range from 100 Hz to 1 MHz indicates that the prepared ferrites have relatively high purity. © 2012 The Author(s).

World University root node

Department of Physics

School of Advanced Sciences

Vellore Campus

Journal of Electroceramics

Magnetic properties of Ni-Zn ferrites prepared by microwave sintering method

Lead oxide sample was prepared at low temperature by the solvo-thermal method. The lead oxide samples were characterized by X-ray diffraction (XRD), FT-IR and transmission electron spectroscopy (TEM) were employed to identify the structural phases, vibrational stretching frequencies and particle nature. X-ray diffraction studies indicate the formation of stable crystalline phase at 75 °C. Transmission electron microscopy and selected area electron diffraction analysis confirms the crystalline nanorods of lead oxide of size 15 - 30 nm. The results of dielectric measurements as a function of frequency, temperature and Cole - Cole plots are reported.

Optoelectronics and Advanced Materials, Rapid Communications

Structural and electrical properties of nano structure lead oxide

Ni – Cu – Zn ferrite materials have been extensively used in multilayer chip inductors because of their remarkable properties at higher frequencies. In the present work, single phase Ni 0.35 Cu 0.05 Zn 0.60 Fe 1.98 O 4-δ ferrite, has been prepared by microwave sintered (MS) method. In comparison with the conventional sintering method (CS), the sintering temperature and time for this MS method were significantly reduced to 30 min and 950°C from 5 h and 1250°C for the CS process. The frequency dependence of the dielectric properties such as dielectric constant (ε'), dielectric loss ( tan δ) were studied. The temperature dependence of magnetic initial permeability (μi) was studied. The saturation magnetization was also studied as a function of magnetic field. These microwave sintered ferrites results were compared with the properties of ferrites prepared by conventional sintering method in normal heating. Microwave sintering improves structural as well as electromagnetic parameters measured and thus makes the ferrite more suitable in microwave applications and electromagnetic devices.

Modern Physics Letters B

STRUCTURAL, ELECTRICAL AND MAGNETIC CHARACTERIZATION OF Ni–Cu–Zn SPINEL FERRITES

This study was aimed at the low temperature synthesis of iron deficient samples of Ni-Cu-Zn ferrite using the microwave sintering technique. The samples were sintered at 950 °C for 30 min. Microstuctural and structural analyses were carried out using a scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The lattice parameter was found to increase with increasing nickel concentration. The porosity calculated using X-ray density and measured density also shows a decreasing behavior with increasing nickel concentration. The variation of saturation magnetization was studied as a function of nickel concentration. All the compositions indicate that they are ferrimagnetic in nature. Initial permeability plotted against temperature at 10 kHz showed a sharp drop at Curie transition temperature and values observed at transition are found to be dependent on the nickel concentration. The dielectric constant, dielectric loss tangent and ac conductivity of all samples were measured at room temperature as a function of frequency. These parameters decrease with increase in frequency for all of the samples. The present ferrites are well suitable for the application in multilayer chip inductor due to its low temperature sinterability, good magnetic properties and low loss at high frequency. © 2010 Elsevier B.V. All rights reserved.

GENERAL

Current Applied Physics

Microwave sintering of iron deficient Ni-Cu-Zn ferrites for multilayer chip inductors

Mg0.40Cu0.10Zn0.50Fe1.95O 4-δ ferrite samples were prepared by the microwave sintering (MS) and conventional sintering (CS) techniques. The samples were then characterized by the x-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS) techniques. All the compositions showed single-phase cubic spinel structure. The lattice constants of MS samples were found to have lower magnitude than those of CS samples. The densities of microwave-sintered samples were higher than those of conventionally sintered samples. The temperature dependence of initial permeability was studied in the temperature range 30-150 °C at 10° temperature intervals. It was noted that the initial permeability of MgCuZn ferrites prepared by the MS method was higher than that of MgCuZn ferrites prepared by the CS method. The initial permeability (μi) magnitude of about 2300 at 10 kHz is achieved for microwave-sintered (Mg0.40Cu0.10Zn 0.50Fe1.95O4-δ) ferrite, at only 950 °C sintering temperature. In addition, the sintering time of ferrites was reduced from 5 h to 20 min by using the MS technique. The low-temperature- sintered MgCuZn ferrites prepared possess good electromagnetic properties, as well as good microstructure, thus making them suitable materials for multilayer chip inductors (MLCIs) having high performance and low cost. © 2010 The Royal Swedish Academy of Sciences.

Physica Scripta

Microwave sintering of high-permeability MgCuZn ferrite at low sintering temperatures suitable for microinductor applications

Polycrystalline MgCuZn ferrites with chemical formula Mg 0.50-xCuxZn0.50Fe2O4 (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were prepared by microwave sintering method. These powders were calcined, compacted and sintered at 950 °C for 30 min. Structural, microstructural and elemental analyses were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. The sintered ferrite was characterized for initial permeability, dielectric constant and dielectric loss tangent and ac conductivity measurements. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 200 °C. The dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range of 100 Hz to 1 MHz. Initial permeability and dielectric constant were found to increase and dielectric loss decreased with Cu substitution for Mg, up to x = 0.20. The ferrite powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency. © 2010 Elsevier B.V.

Materials Science and Engineering C

Influence of copper substitution on magnetic and electrical properties of MgCuZn ferrite prepared by microwave sintering method

The low temperature microwave sintered NiCuZn and MgCuZn ferrites with compositions Ni0.35Cu0.05Zn0.60Fe 2O4 and Mg0.35Cu0.05Zn 0.60Fe2O4 were synthesized by conventional mixed oxide method. NiCuZn and MgCuZn ferrite samples obtained showed better sintered densities at 950 and 900 °C, respectively. The scanning electron micrographs of both the ferrite samples appear to be very much similar. The magnitude of initial permeability of MgCuZn ferrite samples is found to be obviously higher than those of NiCuZn ferrite samples at all sintering temperatures. This is mainly due to the fact that MgCuZn ferrite has smaller magnetocrystalline anisotropy constant and magnetostrictive constant. NiCuZn ferrites have higher saturation magnetization than MgCuZn ferrites, which is due to the higher magnetic moment of NiCuZn ferrites. Our results indicate that the microwave sintering method seems to be a potential technique in the MLCI technology. © 2010 Elsevier B.V.

Department of Mathematics

Journal of Magnetism and Magnetic Materials

Effect of sintering temperature on structural and magnetic properties of NiCuZn and MgCuZn ferrites

Polycrystalline NiCuZn soft ferrites with stoichiometric iron were prepared by a novel microwave sintering method. The powders were calcined, compacted and sintered at 950 °C for 30 min in a microwave sintering furnace. X-ray diffraction patterns confirm the formation of single phase cubic spinel structure. The grain size was estimated using SEM micrographs. The lattice constant is found to increase with increase in zinc concentration. The sintered ferrites have been investigated for their physical, magnetic and electrical properties such as bulk density, X-ray density, porosity, anisotropy constant, initial permeability, saturation magnetization, DC resistivity, dielectric constant and dielectric loss as a function of zinc concentration. Permeability, saturation magnetization, dielectric constant and dielectric loss were found to increase while DC resistivity was found to decrease with the replacement of Zn with Ni. The present series of ferrites are found to posses properties that are suitable for the core materials in multilayer chip inductors. © 2010 Elsevier Ltd. All rights reserved.

Journal of Physics and Chemistry of Solids

Structural, magnetic and electrical properties of NiCuZn ferrites prepared by microwave sintering method suitable for MLCI applications

NiCuZn ferrites are widely employed for many electronic applications, but can be replaced by MgCuZn ferrites owing to their superior properties like low magnetostriction, environmental stability, low stress sensitivity and low cost. In view of this, a series of non-stoichiometric MgCuZn ferrites (Mg 0.5-xCuxZn0.5Fe1.9O 4-δ with x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25) have been successfully synthesized by both conventional and microwave sintering techniques. The non-stoichiometry was intentionally introduced into the ferrites to ensure high resistivity of the samples. X-ray diffraction patterns confirm the single phase spinel structure in both cases. The elemental composition of these ferrites was analysed by energy-dispersive x-ray spectrometry. The samples sintered by the microwave technique were found to be denser than the conventionally sintered samples. The initial permeability of MgCuZn ferrites was studied with an increase in copper concentration from x = 0.0 to 0.25. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 150 °C. The results are discussed in the light of microstructure variations of the conventionally and microwave sintered samples. The phenomena involved in microwave sintering are also discussed. © 2009 IOP Publishing Ltd.