Microstructure Of Mn-Zn Ferrites Research Articles

Influence of Particle Size and Ca Addition on the Magnetic Performance and Microstructure of MnZn Ferrite

In this work, the influence of Ca addition on the power loss of MnZn ferrites was investigated. Mn–Zn ferrites were prepared by conventional oxide ceramic process from calcined powders of different particle sizes in equilibrium sintering atmosphere. It has been found that the optimal amount of Ca addition varies for the Mn–Zn ferrites synthesized by using powders of different particle size.

Integration of MnZn-ferrite tapes in LTCC multilayer

For co-firing of MnZn-ferrite tapes and LTCC dielectric tapes, the sintering shrinkage curves and the coefficient of thermal expansion of ferrite and dielectric tapes were matched. Highly densified embedded ferrite without any cracks could be manufactured by co-firing at 900 °C in nitrogen atmosphere. However, the permeability of MnZn-ferrite co-fired between dielectric tapes is significantly reduced (μ´=100) compared to that of the separately sintered ferrite (μ´=500). Changes in the phase stability and microstructure of MnZn-ferrite were investigated to explain the permeability reduction in the embedded ferrite. It is supposed that early densification of the dielectric tapes on the top and bottom of the ferrite layer prevent the gas exchange during sintering which is necessary for (Mn,Zn)Fe2O4 spinel formation. As a result, high amount of Fe2O3 secondary phase and a Mn-rich spinel phase with low permeability remain in the embedded ferrite layer.

Influence of Boron Content in Iron Oxide on Performance of Mn-Zn Ferrites

The ferrites of PC30 (Mn-Zn ferrites) were prepared by using a dry processing route. The effect of Mn-Zn ferrites doped with H 3BO 3 was investigated on the basis of microstructure analysis. The results of the samples doped with H 3BO 3 less than 5×10 −5 showed that the doping had no significant effect on power loss, initial permeability, fine grain microstructure, and density of Mn-Zn ferrites. With the further increase in H 3BO 3 doping (up to 1×10 −4), the microstructure of Mn-Zn ferrites is in the critical state between fine grain and “sandwich”, and the initial permeability and density of Mn-Zn ferrites begin falling quickly; the increased H 3BO 3 doping also results in deteriorated power loss properties. Thus, the control of the boron content in iron oxide is of utmost importance for the quality of Mn-Zn ferrites in producing process.

Study of Mn 3O 4 doping to improve the magnetic properties of MnZn ferrites

The effect of Mn 3O 4 doping on the magnetic properties of MnZn ferrites is studied. It is found that adding Mn 3O 4 as a dopant after pre-sintering, in contrast with the traditional approach of adjusting Mn 3O 4 content in the main composition, results in different magnetic properties of MnZn ferrites. Compared to its corresponding sample, 500 ppm Mn 3O 4 addtion raises the initial permeability of MnZn ferrite sample by 12.97%, and the saturated magnetic induction by 7.45%, and reduces its power loss by up to 23%. The improvement of magnetic properties will be strengthened with the increase of Mn 3O 4 doping amount before it reaches 0.5 wt%, continue increasing the doping amount, and the improvement will be gradually impaired. It is also found that suitable amount of Mn 3O 4 addition mainly reduces the hysteresis loss of MnZn ferrites at frequencies below 200 kHz, and when it is above 200 kHz, the eddy current loss can be considerably reduced. XRD and SEM data reveal that Mn 3O 4 doping results in no obvious change in the microstructure of MnZn ferrites.

Relationship between Power Loss at High Frequency and the Microstructure of Mn-Zn Ferrites

Relationship between Power Loss at High Frequency and the Microstructure of Mn-Zn Ferrites

Microstructure of Mn-Zn Ferrite on MoO3 Addition

The microstructure of Mn-Zn ferrite on MoO3 addition was studied. It was found that although MoO3 addition expanded the diameters of crystalline grains, it also promoted porosity, thereby impeding grain growth. When the amount of MoO3 was increased, the grain diameter expanded, peaked, and then gradually declined under the influence of the porosity. It is important to note that it forms a fine microstructure that has large grains and a low level of porosity. We studied the effect of the sintering parameters−sintering time, heating rate, and oxygen partial pressure−on the microstructure of the ferrite. As a result, we obtained a high-initial-permeability Mn-Zn ferrite with μiac = 24,400.

Relationship between Residual Loss and Microstructure of Mn-Zn Ferrites

The core loss characteristics of the Mn-Zn ferrite cores with various grain sizes, electric conductivities and cross sectional areas are analyzed. A part of the residual loss depends on the grain size. It is 4 orders of magnitude larger than the intragrain eddy current loss estimated classically. On the other hand, the core loss calculated by using the dynamic magnetic loss parameter recently introduced by Saotome and Sakaki includes the part. This indicates that the part of the residual loss is related to the interaction between the applied field and the induced magnetic flux.

Influence of hydrothermal powder morphology on the sintered microstructure of MnZn ferrites

The influence of hydrothermal powder morphology on the sintered microstructure of MnZn ferrites has been analysed. Changes in lattice parameter, particle size, density, size and total volume of pores and in the surface area of the particles were studied as functions of hydrothermal temperature and time. The ferrites were sintered at 1250 °C in a dry nitrogen atmosphere. High density and surface homogeneous ceramic bodies were obtained, without zinc loss by volatilisation. It has been observed that small differences on the properties of the hydrothermal powders gave rise to rather different microstructures after sintering. The effects of the surface chemistry of the nanosized ferrite particles and of the sintering atmosphere employed are discussed, in order to explain this behaviour. Finally, the magnetic character of the ferrite powders as well as of the sintered bodies was analysed at different conditions of temperature and applied magnetic field.

Optimum power-loss and microstructure of MnZn ferrites under consideration of particle size

This report deal with the influence of particle size of MnZn ferrite powder on the preparation of monodomain structure. It is found that when samples were sintered at low temperature (1170/spl deg/C), the power loss and microstructure of MnZn ferrite prepared from powder particle size above 1.3 /spl mu/m are dominated by sample density. On the other hand, the existence of silica still induce exaggerated grain growth for samples prepared from powder below 1 /spl mu/m and added with CaO-SiO/sub 2/ more than 0.1 wt.%. In this study, sample prepared from powder with particle size of 1 /spl mu/m and added by 0.07 wt.% CaO-SiO/sub 2/ exhibits optimum power loss.

The solid state single crystal growth from MnZn ferrite polycrystal with additives

Among grain growth enhancing additives, the effect of B on the microstructure of Mn-Zn ferrites was studied. By adhering a seed single crystal plate on the B doped ferrite with ethylsilicate adhesive solution, the polycrystal was converted into a single crystal under the suitable heat treatment conditions, and the mechanism of this conversion was investigated.

Effect of the presintering process on the microstructure and initial permeability of Mn-Zn ferrite

It was found that cooling treatment during the presintering process had considerable influence on the initial permeability of Mn 0.516Zn 0.395Fe 2.089O 4 ferrite. The initial permeability increased to a large extent for the samples obtained from quenched powders. This phenomenon was not connected with the microstructure of the Mn-Zn ferrite.