High-permeability MnZn Ferrites Research Articles

Substitution of Sn in the high-permeability MnZn ferrite for wide temperature applications

To meet the challenge of varied working temperatures of inductance components in new energy vehicle and 5G communication, the high-TC high-permeability MnZn ferrite with excellent temperature stability was developed by the addition of SnO2. In this series of samples, initial permeability μi maintains large values in a wide temperature range. With increasing the SnO2 content, the temperature of the second permeability peak Tsp decreases and meanwhile Curie temperature TC maintains as high as 160 °C. For the best sample with 6000 ppm SnO2, μi at 25 °C is 7244 and exhibits the excellent temperature stability with the low specific temperature coefficient of 0.35 × 10−6 °C−1 between 25 and 130 °C. The addition of SnO2 generates Fe2+ and adjusts the magneto-crystalline anisotropy constant K1 = 0 point, which is responsible for the wide-temperature high permeability. The effect of SnO2 addition on magnetization process has also been clarified.

Ferrite materials with high saturation magnetic induction intensity and high permeability for magnetic field energy harvesting: Magnetization mechanism and Brillouin function temperature characteristics

Manganese-zinc (MnZn) ferrites play an indispensable role in energy transform and harvesting. It is notable to mention that the combined enhancement of initial permeability (μi), saturation magnetic induction (Bs) and Curie temperature (Tc) is conducive to improving the output power and safety of magnetic field energy harvesting devices. In this paper, high permeability MnZn ferrites were synthesized by a conventional oxide ceramic method. The thermomagnetic curves of MnZn ferrites were fitted according to the Néel molecular field theory (NMFT) and the Brillouin function. Then the molecular field coefficient γaa, γab, γbb, and Tc were calculated. Aiming at the magnetization mechanism of permeability, the contributions of domain wall motion and spin rotation were analyzed by fitting the complex permeability spectrum. Furthermore, the temperature characteristics of μi and Bs are analyzed, and we simulated and compared the effect of different magnetic properties of MnZn ferrites on the output of non-invasive magnetic field harvester. The MnZn ferrites with superior comprehensive performance own potential applications for non-invasive magnetic field harvester.

Influence of Particle Size Distribution on the Consistency of High Permeability MnZn Ferrite

High-permeability MnZn ferrite cores were sintered under various sintering temperatures and atmospheres by using powders of different particle size distributions. It has been found that electromagnetic performance of cores sintered from powders with finer particle size and narrower size distribution varies less upon the change of sintering temperature and atmosphere. This suggests that the permeability consistency of MnZn ferrite can be improved by using fine powder with better uniformity in mass production.

Process and material parameters towards the design of fast firing cycles for high permeability MnZn ferrites

In this article the design of a fast sintering cycle of high permeability (ui>5000) MnZn ferrites is described. This has been accomplished through the optimization of selected parameters in the manufacturing process. The ferrites were prepared following the solid state reaction method and the sintered specimens were electromagnetically evaluated. As found, the combination of the morphology of the raw materials, the incorporation of In2O3 as a dopant, the atmosphere profile, as well as the cooling rates play a major role in the determination of the magnetic performance of the sintered core. The combined optimization of these parameters led to the design of a sintering profile that is 34% faster, while at the same time the initial permeability of the MnZn ferrite is increased by 35% and the magnetic losses are decreased by 14–34%, depending on the frequency level.

Effect of multi-additives on the microstructure and magnetic properties of high permeability Mn–Zn ferrite

The Mn–Zn ferrite precursor prepared by the hydrometallurgical route is used as raw material to prepare high permeability Mn–Zn ferrite through traditional ceramic process. The influences of three different categories of additives on the initial permeability and microstructure of Mn–Zn ferrites are investigated. Meanwhile the corresponding possible mechanisms are proposed to interpret the effect of the dopants on the magnetic properties of ferrite materials. The results show that additives CaCO3/SiO2 can significantly improve the frequency stability of permeability by creating a high resistivity grain-boundary; Bi2O3 can promote the ferrite grain growth and affect microstructure development; proper amount of SnO2 and V2O5 can increase the initial permeability effectively, while excessive SnO2/V2O5 concentration results in the abnormal grain growth and the decrease of initial permeability. Based on the doping experiment, the Mn–Zn ferrite sample doped with 0.02wt.% CaCO3,0.03wt.% Bi2O3, 0.02wt.% V2O5 and 0.02wt.% SnO2 displays higher magnetic properties including high initial permeability, wide frequency stability and temperature stability of permeability, indicating that the sample can compete with the R12K (a competitive product) made in Hengdian corporation of China.

Effect of Milling on the Properties of High Permeability Mn-Zn Ferrite Powders

High permeability Mn-Zn ferrites with broad frequency characteristic were prepared by the traditional ceramic method using the pre-sintering powders of Mn-Zn ferrite wastes. ICP Atomic Emission Spectrophotometer, scanning electron microscopy (SEM), Particle Sizer and LCR broadband digital bridge were used to investigate the influence of milling on the microstructure and properties of sintered Mn-Zn ferrite. During the milling, the impurities such as silicon and chromium were introduced into the powders as using steel balls. The particle size of powders decreased to a †minimum size with the increasing of milling time. As the particle size after milling was about 1 um, the initial permeability of Mn-Zn ferrites with small internal porosity, high density and uniform structure could reach 10000. Furthermore, the value were unaffected by the change in frequency 0 to 150 kHz.

On Preparation of High Permeability Mn-Zn Ferrite

With the development of electronic information technology, the electronic equipment are required to be smaller, lighter and more reliable, which puts forwards a higher request to the electronic elements with ferrite materials. In this dissertation, high permittivity MnZn ferrite are fabricated by solid state reaction method with Fe2O3,MnOand ZnO as starting raw material.The effects of formulation and sintering technique on the properties of the samples were studied. Finally, the results showed that: the best formula of high permeability Mn-Zn ferrite is Fe2O3: MnO: ZnO = 51:25:24mol%;the best sintering temperature is 1360 °C.

The effect of heating rate on the microstructure and properties of high magnetic permeability MnZn-ferrites

In this paper the effect of the heating rate, during the final firing step, on the microstructure and initial magnetic permeability of high permeability MnZn-ferrites is reported. Increased heating rates result in higher density, coarser microstructure and higher magnetic permeability, independent of the particularly chosen process conditions such as prefiring temperature or compaction pressure. As also found, increased heating rates retard densification and grain growth, thus sintering, during the heating stage. This has the consequence that more powder sintering activity is being preserved within the microstructure of the compact. Subsequently, during the dwell time at the top temperature, densification and grain growth take place at higher rates resulting finally to increased density, coarser microstructure and higher magnetic permeability. The results indicate that shortening of the duration of the firing curves in high permeability MnZn-ferrites, without deteriorating the magnetic properties is possible through the heating rate.

Cathodic Electrophoretic Deposition of Ceramic Nano-Particle Manganese Zinc Ferrite

The electrophoretic deposition (EPD) of micro/nano-particle manganese zinc ferrite (Mnx Zn1-xFe2O4) material has been carried out on silicon substrates. EPD is performed in isopropanol (IPA) solutions containing charging and adhesion agents. The ferrite powders were prepared by grinding ceramic sintered toroids of a commercial high permeability Mn-Zn ferrite. The ferrite film has been deposited up to 4μm in thickness in 30 minutes showing good selectivity to silicon patterned with 250nm thermally grown silicon dioxide. Additionally, selective deposition has been observed on heavily doped p-type regions in n-type silicon substrates. The deposition process is a self limiting process with the initial high elerophoretic current declining to 10% of its value in 10 minutes. This result suggests that majority of ferrite deposition occurs in first 10 minutes. The deposition rate and zeta potential measurements indicate a high particle velocity on the order 5.7x10-3 cm/s with an electric field of 160V/cm generated across the 2 cm electrode spacing. An amorphous like interfacial layer is observed in as deposited substrates. The scanning electron micrographs indicate pattern filling and conformal deposition on copper planar micro-inductors fabricated by chemical mechanical planarization. These results are promising for powder ferrite material (hard and soft) to be selectively deposited for a wide variety of applications in microelectronics passive components and in MEM’s based applications

Effects of SnO 2 addition on the magnetic properties of manganese zinc ferrites

SnO 2 was added to high-permeability MnZn ferrites and MnZn ferrites for high-frequency power supplies. The effects of the SnO 2 addition were studied. Sn 4+ ions can dissolve into the spinel lattice and form stable Fe 2+–Sn 4+ pairs and hence can compensate the magneto-crystalline anisotropy constant K 1 and improve the initial permeability effectively. The initial permeability of ferrites is also improved as abnormal grain growth caused by ion vacancy is controlled with SnO 2 doping. In addition, the SnO 2 doping also leads to a decrease in the relative loss factor and an increase in density. The power loss and minimum power loss temperature decrease with SnO 2 doping.

Self-propagating high-temperature synthesis of MnZn-ferrites for inductor applications

The self-propagating high-temperature synthesis (SHS) route is evaluated for the synthesis of MnZn-ferrite powders that are subsequently processed towards the manufacturing of high initial magnetic permeability polycrystalline specimens for inductor applications. The conditions for the synthesis of particular phases by SHS reactions between iron metal and oxide powders were optimized and the effects of the synthesis parameters on ignition and propagation characteristics were studied. By “fine-tuning” the synthesis parameters, products of a wide spectrum of phases from single-phase, pure and well crystallized (MnxZny)Fe2+δO4 to the oxide of the divalent metals (Mnx′Zny′Fe1−x′−y′)O could be controllably synthesized. Advantages of the synthesis route are demonstrated by tests on properties of merit on final products: combustion powder products were subsequently pressed to torroids, sintered and characterized with respect to their magnetic properties, in comparison to conventionally synthesized samples of the same composition. When sintered under appropriate schedules of oxygen partial pressure profile to avoid phase oxidation at 600°C, SHS powders could be processed to high permeability MnZn-ferrites. At equal average particle sizes SHS powders exhibit higher reactivity and grain growth compared to conventionally synthesized powders. This advantage can be utilized in the manufacturing of high permeability MnZn-ferrites with shorter firing schedules and thus all associated advantages in terms of productivity, production costs or zinc evaporation loss.

Magnetoelastic Villari effect in high-permeability Mn–Zn ferrites and modeling of this effect

The results of magnetoelastic investigation in Mn 0.51Zn 0.44Fe 2.05O 4 high-permeability ferrite are presented. The obtained results are compared with the energy-based Jiles–Atherton–Sablik model of the magnetization process. Dependence of model's parameters on compressive stress up to 60 MPa is presented.

Development of a flyback polymer thick film planar transformer using Mn-Zn ferrite for HF switch mode DC-DC converter

In this work, air core and ferrite core polymer transformers were developed using polymer thick film screen-printing technology. These transformers were printed on 5 × 5cm alumina substrate. The magnetic core material was home-made high permeability Mn–Zn ferrite. An efficiency of 93% and a coupling factor of 0.9 at 500kHz were achieved. This transformer design has five primary turns connected in series and one secondary turn consisting of five turns connected in parallel, the primary and the secondary windings being fully interleaved. All the layers, including the magnetic (Mn–Zn), isolative and conductive layers of the transformers, are made from polymer paste materials. Due to their higher heat radiation, higher power density and lower profile over conventional transformers, these transformers can be used in DC–DC converters for switch mode power supply (SMPS) applications.

Mn-Zn ferrite with MoO/sub 3/ and other oxide additives

We studied the effects of mixing a high-permeability Mn-Zn ferrite with two different additives simultaneously-MoO/sub 3/ (known to promote grain growth) and another oxide having a low melting point. We found that, paired with MoO/sub 3/, V/sub 2/O/sub 5/ had an effect of speeding up ferrite shrinkage, thereby enabling the sintering of ferrites in a shorter time or at a lower temperature. Similarly coupled with MoO/sub 3/, PbO had an effect of increasing the ferrite shrinkage rate, resulting in a higher permeability of the ferrite with an initial-permeability measurement of 25,500.

The Manufacture of High Permeability Mn-Zn Ferrites by Atmospherical Protect

For the manufacture of high permeability Mn-Zn ferrite cores, the zinc loss from the surface of sintering cores causes poor yield rate of final products. This experiment uses the atmospherical protection to reduce the evaporation of zinc. The control of the oxygen partial pressure and flow rate precisely can reduce the zinc loss about 20% to 35%, but it is not enough to get a good distribution of permeability of products, i.e. the distribution of initial permeability from 12000 to 15000 per products about 14% before atmospherical control and 25% after atmospherical control, respectively. Combination with precise control and zinc vapor compensation can increase the yield rate 9% to 15%. Another experiment to manufacture high permeability Mn-Zn ferrite cores for 15000±30% in a batch type furnace(about 13 Kg / batch), is to use a new engineering method to protect sintering core to avoid vaporizing zinc vapor, the yield rate can be rapidly increased from 25% to 75% and the effective capacity of furnace can be at least twofold. It is successful to manufacture homogeneous and high permeability of MnZn ferrites both increasing the quality of products and decreasing the operating costs.

Effects of MoO/sub 3/ addition on manganese zinc ferrites

We examined the effect of added MoO/sub 3/ on the initial permeability and other material characteristics in order to develop Mn-Zn ferrites with a high permeability. It was found that although MoO/sub 3/ addition could expand the diameters of crystalline grains, it could also promote porosity, thereby impeding grain growth. When the amount of MoO/sub 3/ was increased, the grain diameter expanded, peaked, and then gradually declined under the influence of porosity. However, by prolonging the top-temperature sintering period to curb porosity, it was possible to realize the grain-growth-promotion effect of MoO/sub 3/. Thus, we confirmed that high-permeability Mn-Zn ferrites could be obtained using a sintering technique which would enhance ferrite density.

Effect of sintering parameters on Zn loss for preparation of high permeability MnZn ferrites

The significant effects of sintering atmosphere and setter materials on the zinc loss of Mn-Zn ferrites are shown. It is demonstrated that the zinc loss will reduce the initial permeability from 11000 to 6000. The key sintering parameters increasing this zinc loss are low oxygen atmosphere in high temperature, high gas flow rate in the furnace, and the reaction of zinc oxide with Al/sub 2/O/sub 3/. Minimizing zinc loss during sintering is of paramount importance to the successful preparation of high permeability Mn-Zn ferrites.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-permeability MnZn ferrites with flat &amp;#181;-T curves

For various applications ferrite materials are required with a high permeability and a small variation of the permeability in a temperature range from 0 to 60°C. From a discussion of the theoretical conditions necessary for the occurrence of a high permeability and a flat μ-T curve in MnZn ferrites, it is clear that these two requirements are controversial. However, by a proper choice of the composition and a correct application of the method of reoxidation during sintering, a good compromise can be obtained. In the laboratory a permeability variation Δμ of less than 5 percent has been realized for a permeability level of 7500 in the above temperature range.