Wide-temperature-range low-loss manganese-zinc ferrite material and preparation method thereof

Abstract

The present application relates to a kind of wide temperature range low-loss manganese-zinc ferrite material and its preparation method, belong to soft magnetic ferrite ceramic material technical field, solve the problem that the magnetic permeability of existing manganese-zinc ferrite material is unstable in wide temperature range, magnetic loss is larger, magnetic flux density is low.According to mass percentage, the content of each component in the ferrite material is respectively:Fe2O366wt%-69wt%, MnO 14wt%-16wt%, ZnO 16wt%-19wt%, Co2O3 0.25wt%-0.38wt%, V2O5 0.06wt%-0.12wt%, MoO3 0.06wt%-0.08wt%, Ce2O3 0.05wt%-0.08wt%, Sm2O3 0.03wt%-0.06wt%.Co2O3 can reduce hysteresis loss;V2O5 can reduce sintering temperature and can avoid the decrease of magnetic permeability;Ce2O3 can realize ferrite liquid phase sintering, improve amplitude permeability, reduce hysteresis loss;Sm2O3 can refine grain, reduce magnetic loss;MoO3 can improve ferrite microstructure density, reduce porosity, improve mechanical properties.The manganese-zinc ferrite material of the present application can be widely used in aerospace environment.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic ferrite ceramic materials technology, and in particular to a wide-temperature-range, low-loss manganese-zinc ferrite material and its preparation method. Background Technology

[0002] Soft magnetic ferrites mainly include three series: manganese-zinc, nickel-zinc, and magnesium-zinc ferrite materials. They are primarily used in the power, electronics, communications, electrical appliances, and automotive industries. Compared to the other two ferrite materials, manganese-zinc ferrites are mainly used in the low-to-medium-high frequency range, possessing advantages such as high initial permeability, low power loss, high saturation flux density, and excellent temperature stability. Benefiting from the growing demand from electric vehicles, 5G communications, and industrial automation, the future development of manganese-zinc ferrite cores will focus on higher frequencies, energy efficiency, multi-functionality, and customization, placing higher demands on the operating temperature and losses of ferrite materials.

[0003] However, the magnetic properties of existing manganese zinc ferrites are greatly affected by temperature changes, and there are many problems with their wide temperature range (-55℃ to 125℃). The initial permeability (μi), saturation magnetic flux density (Bs), and power loss (Pcv) of manganese zinc ferrites will decrease significantly when the operating temperature is too high or too low. In addition, although the Curie temperature Tc of ferrite materials can be increased by ion substitution, this usually comes at the expense of other electromagnetic properties, resulting in unstable permeability and relatively large magnetic loss.

[0004] Therefore, there is an urgent need for a ferrite with stable magnetic permeability and low magnetic loss over a wide temperature range. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a wide-temperature-range, low-loss manganese-zinc ferrite material and its preparation method, in order to solve at least one of the problems of existing manganese-zinc ferrite materials, namely, unstable magnetic permeability, large magnetic loss, and low magnetic flux density over a wide temperature range.

[0006] In a first aspect, embodiments of the present invention provide a wide-temperature-range, low-loss manganese-zinc ferrite material, the ferrite material comprising a main component and additives, wherein the main component comprises Fe2O3, MnO, and ZnO; and the additives comprise Co2O3, V2O5, and MoO. 3、The contents of Ce2O3 and Sm2O3 in the ferrite material, by mass percentage, are as follows: Fe2O3 66wt%~69wt%, MnO 14wt%~16wt%, ZnO 16wt%~19wt%, Co2O3 0.25wt%~0.38wt%, V2O5 0.06wt%~0.12wt%, MoO3 0.06wt%~0.08wt%, Ce2O3 0.05wt%~0.08wt%, and Sm2O3 0.03wt%~0.06wt%.

[0007] Furthermore, the content of Co2O3 is 0.25wt% to 0.35wt%.

[0008] Furthermore, the grain size of the ferrite material is 8-12 μm.

[0009] Furthermore, the density of the ferrite material is 48-55 kg / m³.

[0010] Secondly, embodiments of the present invention provide a method for preparing a wide-temperature-range, low-loss manganese-zinc ferrite material, wherein the wide-temperature-range, low-loss manganese-zinc ferrite material is the ferrite according to any one of claims 1-3, and the method includes:

[0011] (1) The main component raw materials are mixed and ball-milled to obtain mixture A;

[0012] (2) The mixture A is pre-sintered to obtain a pre-sintered material;

[0013] (3) The pre-calcined material is mixed with the additive raw materials and ball-milled a second time to obtain mixture B;

[0014] (4) Spray granulation of the mixture B and drying to obtain granules;

[0015] (5) Press the granular material into shape and sinter it.

[0016] Furthermore, in steps (1) and (3), the ball milling uses yttrium-stabilized zirconia balls with a particle size of 5-15 mm.

[0017] Furthermore, in step (3), the particle size of the mixture B obtained after the secondary ball milling is 1μm to 5μm.

[0018] Furthermore, in step (2), the pre-sintering temperature is 700℃~900℃ and the time is 4h~6h.

[0019] Furthermore, in step (4), after adding adhesive and defoamer to the mixture B, spray granulation is performed, wherein the amount of adhesive added is 0.3-1.0% of the mixture B, and the amount of defoamer added is 0.01-0.25% of the mixture B;

[0020] Furthermore, the particle size of the granules is 60–300 μm, and the specific gravity is 1.32 g / cm³. 3 ~1.65g / cm 3 .

[0021] Furthermore, in step (5), the pressing pressure is 400 MPa to 500 MPa, and the pressing density is 4.0 g / cm³. 3 ~4.8g / cm 3 .

[0022] Furthermore, the sintering temperature is 1000-1200℃, and the time is 4-6 hours.

[0023] Thirdly, the present invention provides an application of a ferrite material in the aerospace environment. The ferrite material is the ferrite material described in the present invention, wherein the application frequency of the ferrite material is 100kHz~10MHz and the application temperature is -55~125℃.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] 1. Compared with existing manganese-zinc ferrites, the manganese-zinc ferrite of this invention is doped with five elements: Co, V, Mo, Ce, and Sm. The addition of Co creates uniaxial anisotropy, increasing K1 and thus reducing hysteresis loss. The addition of V promotes grain growth, thereby lowering the sintering temperature and preventing a decrease in permeability. Ce enables liquid-phase sintering of the ferrite, increasing sintering activity, improving its microstructure, increasing amplitude permeability, and reducing hysteresis loss. Sm refines the grains and reduces magnetic loss. Mo increases the microstructure density of the ferrite, reduces coercivity, promotes grain growth, reduces porosity, and improves the mechanical properties of the ferromagnetic material. By controlling the various doping elements and their proportions, this invention enables the manganese-zinc ferrite to achieve stable permeability, low magnetic loss, and high saturation flux density over a wide temperature range.

[0026] 2. This invention regulates the addition of various doping elements and their amounts to alter the microstructure during the ferrite preparation process. This not only improves the electromagnetic properties of ferrite over a wide temperature range but also enhances its mechanical properties, making it less prone to cracking or damage during processing and use. Specifically, the particle size of the manganese-zinc ferrite doped with various elements in this invention is 8-12 μm.

[0027] 3. This invention, through the design of ferrite composition elements, allows CeO2 to not only improve resistivity, reduce high-frequency core loss, and improve the temperature stability of magnetic properties through lattice distortion and enrichment at grain boundaries during ferrite sintering, but also to act as a sintering aid, promoting the liquid phase sintering of ferrite, filling the pores between grains, and, in conjunction with V2O5, promoting grain growth, increasing sintering activity, lowering the sintering temperature, and avoiding the decrease in ferrite permeability and increase in magnetic loss caused by excessively high sintering temperatures. Simultaneously, it improves the overall density of the material, contributing to the improvement of the mechanical strength of the ferromagnetic material.

[0028] 4. This invention uses a lower sintering temperature to prepare manganese-zinc ferrite, which can not only prevent core cracking during sintering, but also reduce energy consumption and cost in the production process.

[0029] 5. The density of the manganese-zinc ferrite material of this invention is 48-55 kg / m³. 3 The Curie temperature is 160-170℃; the specific temperature coefficient is 6×10⁻⁶ within the range of -55℃ to +125℃. -6 ~8×10 -6 / ℃; the quality factor Q at 10MHz is 5.4-6.0; the sintering crack rate is ≤11‰.

[0030] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0031] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0032] Figure 1 Images showing the microstructure of existing manganese-zinc ferrites;

[0033] Figure 2 This is a microstructure image of the manganese-zinc ferrite of the present invention. Detailed Implementation

[0034] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0035] Manganese-zinc ferrite materials are mainly composed of oxides of manganese (Mn), zinc (Zn), and iron (Fe), with the typical chemical formula Mn. 0.6 Zn 0.4 While Fe2O4 is a common component, this isn't absolute, and its composition ratio can be adjusted as needed. The ratio of manganese to zinc affects the magnetic properties and Curie temperature of the ferrite. Generally, increasing the zinc content lowers the Curie point and increases saturation magnetization, but also reduces permeability and resistivity. Conversely, increasing the manganese content improves the resistivity and reduces losses. Furthermore, iron is a key component for ensuring the material's magnetic properties. Benefiting from the growing demand from electric vehicles, 5G communications, and industrial automation, the future development of manganese-zinc ferrite cores will focus on high-frequency operation, energy efficiency, multi-functionality, and customization, placing higher demands on the operating temperature and losses of ferrite materials.

[0036] The magnetic properties of existing manganese-zinc ferrite materials are greatly affected by temperature changes, and there are many problems when applying them to a wide temperature range. For example, the initial permeability (μi), saturation flux density (Bs), and power loss (Pcv) of manganese-zinc ferrite will decrease significantly when the operating temperature is too high or too low. In addition, although the Curie temperature Tc of ferrite materials can be increased by ion substitution, this usually comes at the expense of other electromagnetic properties (such as initial permeability and saturation flux density).

[0037] Therefore, the present invention provides a wide-temperature-range, low-loss manganese-zinc ferrite material, the ferrite material comprising a main component and additives, wherein the main component comprises Fe2O3, MnO, and ZnO; and the additives comprise Co2O3, V2O5, and MoO. 3、 The contents of Ce2O3 and Sm2O3 in the ferrite material, by mass percentage, are as follows: Fe2O3 66wt%~69wt%, MnO 14wt%~16wt%, ZnO 16wt%~19wt%, Co2O3 0.25wt%~0.38wt%, V2O5 0.06wt%~0.12wt%, MoO3 0.06wt%~0.08wt%, Ce2O3 0.05wt%~0.08wt%, and Sm2O3 0.03wt%~0.06wt%.

[0038] Compared with existing manganese-zinc ferrite materials, the manganese-zinc ferrite of this invention is doped with five elements: Co, V, Mo, Ce, and Sm. By controlling the various doping elements and their ratios, the manganese-zinc ferrite achieves stable magnetic permeability, low magnetic loss, and high saturation magnetic flux density over a wide temperature range.

[0039] The addition of Co2O3 creates uniaxial anisotropy, increasing K1 and thus reducing hysteresis loss; the addition of V2O5 promotes grain growth, thereby lowering the sintering temperature and preventing a decrease in permeability; Ce2O3 enables ferrite to achieve liquid-phase sintering, increasing sintering activity, thereby improving its microstructure, increasing amplitude permeability, and reducing hysteresis loss; Sm refines grains and reduces magnetic loss; Mo increases the microstructure density of ferrite, reduces coercivity, promotes grain growth, reduces porosity, and improves the mechanical properties of ferromagnetic materials.

[0040] It should be noted that manganese-zinc ferrite itself exhibits negative anisotropy over a wide temperature range. The ion possesses a large positive uniaxial magnetocrystalline anisotropy when it replaces a molecule in the crystal lattice. When located at the octahedral B site, a positive anisotropic component is introduced into the material, increasing the K1 value of the ferrite and even offsetting the negative anisotropy of the manganese-zinc ferrite itself, thereby improving the temperature stability of the magnetic properties and reducing power loss.

[0041] Specifically, in the raw materials for preparing the manganese-zinc ferrite of the present invention, the content of Co2O3 is 0.25wt% to 0.38wt%, preferably 0.25wt% to 0.35wt%. If the content is too low, it cannot fully compensate for the negative anisotropy of the manganese-zinc ferrite, resulting in poor improvement in temperature stability; if the content is too high, it will lead to overcompensation, and even if the net anisotropy becomes positive, the temperature stability will actually worsen.

[0042] According to some preferred embodiments of the present invention, the content of Co2O3 in the raw materials for preparing the manganese zinc ferrite of the present invention is any value in the range of 0.25wt% to 0.38wt%, such as 0.25%, 0.28%, 0.30%, 0.33%, 0.35%, and 0.38%.

[0043] It should be noted that V2O5 has a melting point of 680℃. During the sintering preparation of manganese-zinc ferrite, it reacts with Fe2O3 to form other multi-element eutectic compounds such as ferrovanadate with a lower melting point. These eutectic compounds melt at temperatures far below the temperature required for complete solid-state sintering of ferrite grains, forming a liquid glass phase. This facilitates the dissolution of smaller ferrite particles. The dissolved substances diffuse through the liquid phase and precipitate on the surface of larger (lower surface energy) particles, ultimately resulting in high-density, large and uniform grains with clean grain boundaries. Therefore, adding V2O5 can significantly reduce the sintering temperature of MnZn ferrite.

[0044] It is important to note that the microstructure of manganese-zinc ferrite optimized by V2O5 (clean grain boundaries) can greatly weaken the internal stress, pores, impurities and other domain wall pinning points in the material, and enhance the domain wall mobility (manifested as a smoother magnetization process). Ultimately, the macroscopic manifestation is a significant increase in the magnetic permeability of the material. Therefore, within a certain range of addition, using V2O5 to lower the sintering temperature can avoid a decrease in magnetic permeability.

[0045] Additionally, V 5+ Its radius is 0.059 nm, which is greater than that of Fe. 3+ The radius of 0.064 nm is small, while V 5＋ Prefers to enter the tetrahedral position, high-priced V 5＋ This increases oxygen vacancies, resulting in severe lattice distortion and significantly increasing the energy barrier for grain boundary movement. This, in turn, inhibits grain growth during sintering, increases the number of grain boundaries, improves material resistivity, and reduces losses.

[0046] Specifically, in the raw materials for preparing the manganese-zinc ferrite of the present invention, the content of V2O5 is 0.06wt% to 0.12wt%, which can be 0.06wt%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12%. If the content is too low, it will affect the increase of ferrite resistivity, the reduction of power loss, and the reduction of magnetic permeability. If the content is too high, it will easily disrupt the continuity of the magnetic circuit, leading to abnormal grain growth or the formation of closed pores, thus affecting the magnetic properties of the ferrite.

[0047] It should be noted that the role of Ce2O3 differs from that of V2O5 (which forms a continuous, abundant low-melting-point liquid phase). Ce2O3 primarily achieves functional regulation through "grain boundary engineering" and "lattice manipulation," inhibiting abnormal grain growth, purifying grain boundaries, and controlling lattice defects to obtain a uniform, dense microstructure with low internal stress. This improves the amplitude permeability of the ferrite and reduces hysteresis loss. Ce2O3 not only enhances resistivity and reduces high-frequency core loss through lattice distortion and enrichment at grain boundaries, improving the temperature stability of magnetic properties, but also acts as a sintering aid, promoting the sintering of the ferrite liquid phase, filling the pores between grains, and, in conjunction with V2O5, increasing sintering activity and lowering the sintering temperature. This prevents excessively high sintering temperatures from causing a decrease in ferrite permeability and an increase in magnetic loss, while simultaneously increasing the overall density of the material, which helps improve the mechanical strength of the ferromagnetic material.

[0048] Specifically, in the raw materials for preparing the manganese-zinc ferrite of the present invention, the content of Ce2O3 is 0.05wt% to 0.08wt%, such as 0.05%, 0.06%, 0.07%, or 0.08%. If the Ce2O3 content is too low, it will affect the increase of ferrite resistivity, the reduction of power loss, and the reduction of magnetic permeability; if the content is too high, it will disrupt the continuity of the magnetic circuit, resulting in excessively low magnetic permeability and significantly reducing the saturation magnetic flux density Bs.

[0049] It should be noted that MoO3 has a melting point of 795℃ and a boiling point of 1195℃. During sintering, MoO3 exists in a liquid state at the grain boundaries, which lowers the activation energy for grain growth, increases the rate of grain boundary movement, and accelerates grain growth. This reduces the number of grain boundaries per unit volume, meaning that domain walls have fewer obstacles to overcome during magnetization reversal, making them easier to move. This results in larger grains, lower total porosity, higher sintering density, and lower resistivity in the sintered sample; increased initial permeability and lower losses; increased grain size reduces the resistance to domain wall movement during magnetization, thus reducing hysteresis losses; and lower porosity means fewer stress concentration sources, making the material less prone to cracking during pressing and sintering.

[0050] Specifically, in the raw materials for preparing the manganese-zinc ferrite of the present invention, the content of MoO3 is 0.06wt% to 0.08wt%, such as 0.06%, 0.07%, or 0.08%. If the content of MoO3 is too low, the effect is not significant; if the content is too high, it will disrupt the continuity of the magnetic circuit, leading to a catastrophic decrease in Bs and μi. Excessive MoO3 is prone to volatilization at high temperatures, causing uneven composition and performance deterioration.

[0051] It should be noted that the addition of Sm2O3 at the grain boundaries forms a second phase, which refines the magnetic domains and "pins" the domain walls, inhibits grain growth, controls excessive grain growth, and can significantly reduce high-frequency core loss (Pcv) and improve the frequency stability of the initial permeability (μi).

[0052] Specifically, in the raw materials for preparing the manganese-zinc ferrite of the present invention, the content of Sm2O3 is 0.03wt% to 0.06wt%, such as 0.03%, 0.04%, 0.05%, or 0.04%. If the content of Sm2O3 is too low, the effect will not be obvious; excessive doping will lead to a sharp deterioration of μi and Bs due to the formation of too many non-magnetic second phases, and will also increase the cost.

[0053] It should be noted that this invention regulates the addition of various doping elements and their amounts to control the lattice characteristics (intrinsic properties) and microstructure (extrinsic properties) of manganese-zinc ferrite, thereby achieving an optimal balance among multiple key performance parameters. This invention changes the microstructure during the ferrite preparation process by element doping, which not only improves the electromagnetic properties of ferrite over a wide temperature range, but also enhances its mechanical properties, making it less prone to cracking or damage during processing and use.

[0054] Specifically, the average grain size of the multi-element doped manganese-zinc ferrite of this invention is approximately 10 μm; it can be 8 μm, 10 μm, or 12 μm. Grain size directly affects the movement of magnetic domain walls and the domain structure, which is crucial to the performance of soft magnetic materials. If the grain size of the manganese-zinc ferrite is too small, the number of grain boundaries hindering domain wall movement will be too large, leading to a decrease in permeability. If the grain size of the manganese-zinc ferrite is too large, it can easily lead to increased losses.

[0055] Specifically, the density of the manganese-zinc ferrite doped with multiple elements is 48-55 kg / m³. If the proportion of closed pores is too high, it will block the conductive path between grains, which is not conducive to magnetization and will lead to a decrease in mechanical strength. In this invention, while obtaining a high-density ferromagnet, the residual micropores distributed at the grain boundaries can improve the resistivity.

[0056] The density of the manganese-zinc ferrite material of this invention is 48-55 kg / m³. 3 The Curie temperature is 160-170℃; the specific temperature coefficient is 6×10⁻⁶ within the range of -55℃ to +125℃. -6 ~8×10 -6 / ℃; the quality factor Q at 10MHz is 5.4-6.0; the sintering crack rate is ≤11‰.

[0057] Secondly, embodiments of the present invention provide a method for preparing a wide-temperature-range, low-loss manganese-zinc ferrite material, wherein the wide-temperature-range, low-loss manganese-zinc ferrite material is the ferrite, and the method includes:

[0058] (1) The main component raw materials are mixed and ball-milled to obtain mixture A;

[0059] (2) The mixture A is pre-sintered to obtain a pre-sintered material;

[0060] (3) The pre-calcined material is mixed with the additive raw materials and ball-milled a second time to obtain mixture B;

[0061] (4) Spray granulation of the mixture B and drying to obtain granules;

[0062] (5) Press the granular material into shape and sinter it.

[0063] It should be noted that, in order to achieve the desired effect on specific harmful impurities ( Strict control of the purity of raw materials (such as CaO, MgO, and alkali metals) is required in this invention.

[0064] Specifically, the purity of the raw material Fe2O3 is controlled to be above 99%, and the purity of MnO is above 96%.

[0065] It should be noted that, in order to ensure the overall composition ratio of the raw materials to the greatest extent, the composition of the grinding balls needs to be limited during the ball milling process.

[0066] Specifically, in steps (1) and (3), the ball mill uses yttrium-stabilized zirconia balls with a particle size of 5-15 mm, and controls the raw material loss per hour to below 0.5 ppm.

[0067] It should be noted that, in order to ensure the uniformity of mixing, maintain the overall composition ratio of raw materials, and reduce energy consumption, the present invention requires limiting the ball milling time.

[0068] Specifically, in step (1), the ball milling time of this invention is 1-3 hours. It can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. If the time is too short, the raw material size will be too large after ball milling and the mixing will be uneven; if the time is too long, it will increase energy consumption.

[0069] Specifically, in step (3), the secondary ball milling time of this invention is 5-6 hours. It can be 5 hours, 5.5 hours, or 6 hours; if the raw material size is too large after ball milling, the mixing will be uneven; if the time is too long, it will increase energy consumption.

[0070] Specifically, in step (3), the particle size of the mixture B obtained after the secondary ball milling is 1μm to 5μm. Particles of this size have higher sintering activity. At the same time, due to the uniform dispersion of the trace amount of additives at the nanoscale under the action of secondary ball milling, it is beneficial to control the grain size and grain boundary characteristics of the final product.

[0071] It should be noted that, in order to reduce subsequent sintering shrinkage and inhibit abnormal grain growth, the present invention requires pre-sintering of the main component raw materials.

[0072] Specifically, in step (2), the pre-sintering temperature is 700℃~900℃ and the time is 4h~6h.

[0073] According to some preferred embodiments of the present invention, the pre-sintering temperature is 700℃, 750℃, 800℃, 850℃, or 900℃, and the time is 4h, 4.5h, 5h, 5.5h, or 6h.

[0074] It should be noted that in order to form spherical, free-flowing, and controllable particle size powder particles from the mixed raw materials after secondary ball milling, the present invention performs spray granulation on the mixed raw materials. At the same time, in order to ensure the key aspects of particle forming quality, pressing performance and final sintering performance, binders and defoamers need to be added in the spray granulation process of manganese zinc ferrite.

[0075] Specifically, in step (4), after adding the binder and defoamer to the mixture B, spray granulation is performed. The amount of the binder added is 0.6-1.2% of the mixture B. The binder of the present invention can provide interparticle bonding force, enhance the green strength, improve the fluidity and formability during pressing, decompose and volatilize in the early stage of sintering, leaving a small amount of residual carbon, which has little impact on magnetic properties. However, excessive binder will lead to incomplete sintering and debinding, resulting in pores or cracks.

[0076] Specifically, in step (4), the amount of defoamer added is 0.1-0.4% of the mixture B; the defoamer can eliminate the bubbles generated by the slurry during the spraying process, prevent the formation of hollow or broken shell structures inside the particles, improve the density and surface smoothness of the particles, and facilitate subsequent pressing and sintering; however, excessive defoamer may affect the stability of the slurry, or even cause the surface of the particles to become hydrophobic.

[0077] According to some preferred embodiments of the present invention, the adhesive is a mixture of polyvinyl alcohol, water, and formaldehyde in a mass ratio of 1:1:0.6, and the total content can be 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.9%, 1.0%, 1.1%, or 1.2% of mixture B; the defoamer is polymethylsiloxane, and the content can be 0.10%, 0.12%, 0.15%, 0.17%, 0.20%, 0.23%, 0.25%, 0.28%, 0.30%, 0.33%, 0.36%, or 0.4%.

[0078] It should be noted that, in order to ensure the compactness of the granules and the smooth venting during the subsequent pressing process, this invention requires controlling the size and specific gravity of the granules obtained by spray granulation.

[0079] Specifically, in step (4), the particle size of the granules obtained by spray granulation is 60-300 μm, and the specific gravity is 1.32 g / cm³. 3 ~1.65g / cm 3 .

[0080] According to some preferred embodiments of the present invention, the particle size of the granules obtained by spray granulation can be 60μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, 220μm, 250μm, 280μm, or 300μm.

[0081] It should be noted that in order to achieve dehydration and molding of the material and prepare it for subsequent pressing, the present invention requires drying the granules obtained by spray granulation.

[0082] Specifically, in step (4), the granules obtained by spray granulation are dried. The specific method is as follows: first, heat drying is performed, and then cooling drying is performed. The moisture content of the dried granules can be controlled within ±0.05%. Heat drying can achieve rapid dehydration of the material, which not only has high dehydration efficiency, but also maintains the shape of the granules obtained by spray drying. Cooling drying is mainly to keep the hot material stable and achieve deep drying, specifically to prevent the material from agglomerating, maintain its fluidity, protect the stability of the binder, control the final moisture content of the material, and reduce pressing and sintering defects.

[0083] It should be noted that because the granules produced by spray granulation already contain binder (PVA), additional lubricant is added to ensure smooth demolding and to obtain high-quality green bodies.

[0084] Specifically, in step (5), before pressing the granules into shape, zinc stearate lubricant needs to be added to the granules, with a content of 0.1% to 0.5%, and the lubricant is used after being mixed evenly with the powder.

[0085] It should be noted that, in order to ensure the shape and size of the pressed product, the present invention needs to limit the pressure during the pressing process.

[0086] Specifically, in step (5), the pressing pressure is 400 MPa to 500 MPa, which can be 400 MPa, 430 MPa, 450 MPa, 480 MPa, or 500 MPa. Higher pressure can overcome the internal friction of the particles and ensure that all corners of the complex shape are fully filled and compacted. However, when the pressure reaches a certain value, because the particles are already highly compacted, further increasing the pressure will cause the density increase to become slow. Excessive pressure (above 500 MPa) may cause overpressure, which will cause the binder / lubricant in the particles to fail and instead cause delamination.

[0087] It should be noted that, by adjusting the pressing pressure, and while avoiding delamination failure in the billet after pressing, the pressing density of the billet obtained by this invention is 4.0 g / cm³. 3 ~4.8g / cm 3 A high and uniform density in the green body ensures consistent sintering shrinkage, resulting in high dimensional accuracy and minimal deformation of the product. However, the density cannot be too high, as it can hinder the release of gas during sintering.

[0088] It should be noted that by adjusting the doping elements and their ratios in the ferrite, the sintering temperature and time of the ferrite were reduced, further promoting the improvement of various magnetic properties of the ferrite.

[0089] Specifically, in step (5), the sintering temperature is 1000-1200℃ and the time is 4-6h. This invention uses a lower sintering temperature to prepare manganese-zinc ferrite, which can not only prevent core cracking during sintering, but also reduce energy consumption and cost in the production process.

[0090] According to some preferred embodiments of the present invention, the sintering temperature can be 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃, and the sintering time can be 4h, 4.5h, 5h, 5.5h, or 6h.

[0091] By controlling the amount of various doping elements added and adjusting the preparation method of this invention, the lattice characteristics (intrinsic properties) and microstructure (extrinsic properties) of manganese-zinc ferrite can be controlled, thereby achieving the best balance among multiple key performance parameters. This invention changes the microstructure of ferrite during the preparation process by element doping, which can not only improve the electromagnetic properties of ferrite over a wide temperature range, but also improve the mechanical properties of ferrite, making it less prone to cracking or damage during processing and use.

[0092] The method of this invention produces manganese-zinc ferrites with multi-element doping, with a particle size of 8–12 μm and a density of 48–55 kg / m³. The grain size is directly related to the movement of magnetic domain walls and the magnetic domain structure, which is crucial to the performance of soft magnetic materials. Higher density is beneficial to the magnetization of ferrites and can ensure high mechanical strength of the material. In addition, residual micropores distributed at the grain boundaries can improve resistivity.

[0093] The density of the manganese-zinc ferrite material of this invention is 48-55 kg / m³. 3 The Curie temperature is 160-170℃; the specific temperature coefficient is 6×10⁻⁶ within the range of -55℃ to +125℃. -6 ~8×10 -6 / ℃; the quality factor Q at 10MHz is 5.4-6.0; the sintering crack rate is ≤11‰.

[0094] Thirdly, the present invention also provides an application of a ferrite material in a space environment, wherein the ferrite material is the ferrite material described in the present invention. The application frequency of the ferrite material is 100kHz to 10MHz, and the application temperature is -55 to 125℃.

[0095] The technical solution of the present invention will be further explained and illustrated below through examples and comparative examples.

[0096] Examples 1-5

[0097] (1) Fe2O3 with a purity of 99% or higher, MnO and ZnO with a purity of 96% or higher are mixed in a certain proportion and ground by wet ball milling. Yttrium stabilized zirconia balls with a diameter of 5 mm to 15 mm are used in the ball milling process. The loss per hour is controlled to be less than 0.5 ppm and the ball milling time is 1 h to 3 h to obtain mixture A.

[0098] (2) Transfer the mixture A to a sintering furnace for pre-firing at a temperature of 700℃~900℃ for 4h~6h to obtain pre-fired material;

[0099] (3) Add a specific proportion of Co2O3, V2O5, MoO3, Ce2O3 and Sm2O3 to the pre-burned material and perform secondary ball milling. The secondary ball milling time is 5h to 6h, and the particle size of the secondary ball milling slurry is controlled at 1μm to 5μm to obtain mixture B.

[0100] (4) Add a mixture of polyvinyl alcohol, water and formaldehyde (mass ratio: 1:1:0.6) to mixture B as a binder. The amount of polyvinyl alcohol added is 0.3% to 1.0% of the content of rare earth oxides Ce2O3 and Sm2O3 mixture. Add polymethylsiloxane as a defoaming agent for spray granulation. The amount of polymethylsiloxane added is 0.01% to 0.25 wt% of the solid content of mixture B in S3. The resulting granules are dried.

[0101] The granulated material has a particle diameter of 60–300 μm and a specific gravity of 1.32 g / cm³. 3 ~1.65g / cm 3 The drying method for the granules is as follows: first, heat drying is carried out, followed by cooling drying. The moisture content of the dried granules can be controlled within ±0.05%.

[0102] (5) The granules are pressed into blanks on a powder molding machine using a mold. The pressing pressure is controlled at 400 MPa to 500 MPa, and the pressing density is controlled at 4.0 g / cm³. 3 ~4.8g / cm 3 Zinc stearate is used as a lubricant, with its content controlled at 0.1% to 0.5%, and the lubricant is used after being mixed evenly with the powder.

[0103] The blank is transferred into a sintering furnace for sintering at a temperature of 1100℃±25℃ for 5h±1h. After sintering, it is rapidly cooled to obtain the wide-temperature-range low-loss ferrite core.

[0104] The raw material ratios and process parameters for each embodiment are shown in Table 1:

[0105] Table 1 Raw material ratios and key process parameters for Examples 1-5

[0106]

[0107] Following the material ratios and process parameters set in Examples 1-5, manganese-zinc ferrite was fabricated into a 3mm×2mm×2mm magnetic core. The performance of the magnetic core was tested, and the results are shown in Table 2.

[0108] Table 2 Performance of the magnetic cores prepared in Examples 1-5

[0109]

[0110] Comparative Examples 1-4

[0111] The same method as in Example 1 was used, except that the raw material ratios and / or process parameters were changed in the comparative examples. The raw material ratios and process parameters in each example are shown in Table 3.

[0112] Table 3. Raw material ratios and key process parameters for Comparative Examples 1-4

[0113]

[0114] Following the material ratios and process parameters set in Comparative Examples 1-4, manganese-zinc ferrite was fabricated into a 3mm×2mm×2mm magnetic core. The performance of the magnetic core was tested, and the results are shown in Table 4.

[0115] Table 4 shows the performance of the magnetic cores prepared in Comparative Examples 1-4.

[0116]

[0117] Comparing the performance of the ferrites shown in Tables 2 and 4 above, it can be seen that the ferrite cores produced using the raw material ratio and manufacturing process of this invention have higher initial permeability, saturation flux density and quality factor in a wide temperature range between -55℃ and 125℃, lower magnetic loss and improved mechanical strength.

[0118] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A wide temperature range low loss Mn-Zn ferrite material with an application frequency of 100 KHZ-10 MHz and an application temperature of -55-125℃, characterized in that, The ferrite material comprises a main component and an additive component, the main component comprises Fe2O3, MnO and ZnO; the additive component comprises Co2O3, V2O5, MoO 3、 Ce2O3, Sm2O3, the content of each component in the ferrite material is respectively Fe2O3 66wt%-69wt%, MnO 14wt%-16wt%, ZnO 16wt%-19wt%, Co2O3 0.25wt%-0.35wt%, V2O5 0.06wt%-0.08wt%, MoO3 0.06wt%-0.08wt%, Ce2O3 0.05wt%-0.08wt%, Sm2O3 0.03wt%-0.06wt% according to mass percentage; the ferrite material has the following properties: (1) mixing and ball-milling main component raw materials to obtain a mixture A; (2) pre-sintering the mixture A to obtain a pre-sintered material; (3) mixing the pre-sintered material with additive component raw materials, and performing secondary ball-milling to obtain a mixture B, wherein the particle size of the mixture B is 1-5 μm; (4) spray granulating and drying the mixture B to obtain a granular material; (5) the granulated material is compression molded and sintered, wherein the compression density of the blank obtained after compression molding is 4.0 g / cm 3 ~ 4.8 g / cm 3 and the sintering temperature is 1050-1150℃, and the sintering cracking rate is ≤11‰; In the process of sintering the ferrite, CeO2 not only increases the resistivity, reduces the high-frequency magnetic core loss, and improves the temperature stability of the magnetic properties by lattice distortion and enrichment at the grain boundaries, but also acts as a sintering aid to promote the liquid-phase sintering of the ferrite, fill the pores between the grains, and increase the sintering activity in cooperation with V2O5 to promote the grain growth. Sm2O3 is added to form a second phase at the grain boundaries to refine the magnetic domains and pin the magnetic domain walls. The Curie temperature of the manganese zinc ferrite material is 160 170°C; in the range from 55°C to +125°C, the specific temperature coefficient is 6 x 10 6 ~8 x 10 6 / °C; the quality factor Q at 10 MHz is 5.4 6.

0.

2. The ferrite material according to claim 1, characterized in that, The grain size of the ferrite material is 8-12 μm.

3. The ferrite material of claim 1, wherein In steps (1) and (3), yttrium-stabilized zirconia balls with a particle size of 5-15 mm are used for ball-milling.

4. The ferrite material of claim 1, wherein In step (2), the pre-sintering temperature is 700-900 °C, and the time is 4-6 h.

5. The ferrite material of claim 1, wherein In step (4), after adding a binder and a defoaming agent to the mixture B, spray granulation is performed, wherein the binder is added in an amount of 0.6-1.2 wt% of the mixture B, and the defoaming agent is added in an amount of 0.1-0.4 wt% of the mixture B, both calculated by mass percentage. And / or, the particle size of the granules is 60-300 μm, and the specific gravity is 1.32 g / cm 3 ~ 1.65 g / cm 3 .

6. The ferrite material of claim 1, wherein In step (5), the pressure for the press forming is 400-500 MPa. The sintering time is 4-6 h.

7. Use of a ferrite material in a space environment, characterized in that The ferrite material is the ferrite material according to any one of claims 1-6. The ferrite material is the ferrite material according to any one of claims 1-6.

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