A high-temperature low-loss high-permeability MnZn ferrite material and a preparation method thereof

Abstract

The application relates to the field of MnZn ferrite materials, in particular to a high-temperature low-loss high-permeability MnZn ferrite material and a preparation method. x Fe 2‑x O4 (wherein Me is a metal element), Nb2O5, ZrO2, TiO2, SnO2, and at least one of CaCO3, SiO2, CuO and Bi2O3. Among them, CoMe x Fe 2‑x O4 is a CoFe2O4 matrix and is obtained through ion doping, has high resistivity and low coercivity characteristics, realizes the double functions of regulating the magnetic crystal anisotropy constant and forming a high-resistance state magnetic grain boundary layer between the crystal grains. The MnZn ferrite material prepared by the method has excellent electromagnetic characteristics of low loss, high permeability and high saturation magnetic induction intensity at 140 DEG C high temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic materials, and particularly relates to a high-temperature low-loss high-permeability MnZn ferrite material and a preparation method. BACKGROUND

[0002] With the rapid development of communication, computer, automobile electronics such as 5G communication, server, new energy vehicle, and the upcoming air car, the demand for magnetic materials is increasing day by day. With the development trend of modern devices towards flatness, miniaturization and integration, higher requirements are put forward for the performance of magnetic materials, such as higher working frequency, lower power loss, higher saturation magnetic induction intensity, wider working temperature and temperature stability. The research on MnZn ferrite, which accounts for more than 70% of the total production of soft magnetic ferrite, has been the focus of research at home and abroad, especially in the application fields of new energy vehicles and servers. The high degree of integration and miniaturization reduces the volume of electronic devices and increases the heat flux density in the unit during operation. The heat generated due to the delay in heat dissipation increases the environmental temperature of the device during operation, forcing some magnetic components such as inductors and transformers to have lower loss at higher temperature and higher permeability to cope with the problem of low inductance value caused by limited winding turns in small volume.

[0003] Based on this background, more research focuses on how to improve the wide temperature characteristics of MnZn ferrite, such as TDK's PC95, which has a lower power loss at 25-100℃, and TDK's TPG33B, which has good power loss performance at low temperature. The electron transition caused by high temperature increases the eddy current loss, and the optimization of high temperature loss performance is not ideal.

[0004] Patent CN109836146A discloses a MnZn ferrite with ultra-low high-temperature power loss and a preparation method. The main components are as follows: Fe2O3 is 52.9-53.4mol%, ZnO is 9.0-9.8mol%, and MnO is the balance; the additive auxiliary components are as follows: CaCO3 is 0.03-0.05%, Nb2O5 is 0.02-0.03%, Co2O3 is 0.3-0.4%, ZrO2 is 0.01-0.03%, and KHCO3 is 0.0050-0.020%. The pre-sintered material is subjected to secondary grinding and particle cyclone sorting, and then subjected to processes such as granulation, pressure forming and sintering under atmosphere / temperature control conditions, to obtain a MnZn ferrite with ultra-low high-temperature power loss. Under the test conditions of 100kHz&200mT, the Pcv at 140℃ is 345kW / m 3 , but the initial permeability μ i at 25℃ is 2600±25%.

[0005] Patent CN104591712B discloses a low-loss MnZn ferrite material for -20~140℃ and its manufacturing method. The ferrite material includes main components and auxiliary components. The main components are Fe2O3: 54.5~55.5mol%, ZnO: 7.5~9.5mol%, and the rest is MnO. The auxiliary components are Co2O3: 0.25~0.45wt% and NiO: 0.3~0.9wt% based on the total weight of the main components, and the rest of the auxiliary components include SiO2, CaCO3, V2O5, Nb2O5, ZrO2, Ta2O5, In2O3. It is made through the process steps of batching, mixing, pre-burning, two grinding, granulation, molding, sintering, etc. The sintering density of the material reaches 97% of the theoretical density. The power loss of the magnetic core made of the material is less than 380kW / m 3 at 100kHz, 200mT in the wide temperature range of -20~140℃ 3 . However, its Pcv performance at higher temperature (140℃) deteriorates seriously (more than 360kW / m 3 ).

[0006] Patent CN118271076A discloses a high-resistivity wide-temperature low-loss MnZn ferrite and its preparation method and application. By adjusting the proportion of the main components and adding high-resistivity auxiliary components (CaCO3, ZrO2, HfO2, TiO2), a high-resistance grain boundary is constructed, the overall resistivity of the material is improved, and a sintering process with segmented multi-step holding is combined to obtain a MnZn ferrite with uniform grain size distribution and few pores, thin and high-resistance grain boundaries. The resistance is increased to 13.77Ω·m, thereby reducing the high-temperature loss. The Pcv at 100kHz&200mT&120℃ is about 360kW / m 3 , and the initial permeability is 3154. Although the material resistance is increased, the high-temperature loss performance of this patent does not show obvious advantages compared with other disclosed patents.

[0007] In summary, it is of important application and market value to develop a high-temperature ultra-low-loss MnZn ferrite with high magnetic permeability. SUMMARY

[0008] The purpose of the present application is to provide a high-temperature low-loss high-magnetic-permeability MnZn ferrite material and a preparation method.

[0009] The present application provides a new auxiliary component CoMe x Fe 2-x O4 (Me is a doped metal element, and x is the substitutional mole amount of Me for Fe) for optimizing the power loss performance of MnZn ferrite. The CoMe x Fe 2-xO4 is based on CoFe2O4, and is obtained by metal ion doping. The core idea is: (1) optimizing the electrical and magnetic properties of CoFe2O4 through metal ion doping process, increasing the resistivity of CoFe2O4 and reducing the coercivity thereof; (2) using CoMe x Fe 2-x O4 has the positive magnetic crystal anisotropy constant and the negative magnetic crystal anisotropy constant of the MnZn ferrite, which are complementary, obtaining a high initial permeability, and optimizing the hysteresis loss; (3) CoMe x Fe 2-x O4 at the position between MnZn grains acts as a high-resistance state grain boundary layer, improving the grain boundary resistance and reducing the eddy current loss; (4) compared with the traditional non-magnetic high-resistance state grain boundary, the ferrimagnetic CoMe x Fe 2-x O4 at the grain boundary can effectively increase the magnetic exchange effect between MnZn ferrite grains, increase the initial permeability of the material, and realize the enhancement of the overall magnetic properties of the MnZn ferrite. Unlike general Co oxides such as CoO and Co3O4, which mainly play the role of magnetic crystal anisotropy complementation, the CoMe x Fe 2-x O4 auxiliary component has the functions of general Co oxides, and simultaneously has the functions of improving the grain boundary resistance and enhancing the magnetic exchange effect between grains.

[0010] A preparation method of a high-temperature low-loss high-permeability MnZn ferrite material, comprising the following steps:

[0011] Step 1, preparing high-resistivity CoMe x Fe 2-x O4 powder:

[0012] Co3O4 and Fe2O3 are mixed uniformly in a stoichiometric ratio by wet ball milling, dried, and pre-sintered at 750-950 DEG C in an air atmosphere for 1-2 hours to obtain a pre-sintered material; then impurities are added to the pre-sintered material, wet ball milling is performed to mix uniformly, dried, and sintered at 1300 DEG C-1400 DEG C in an oxygen atmosphere, and after crushing, grinding, and screening, high-resistance doped CoMe x Fe 2-x O4 powder with a particle size of 0.5-1 μm is obtained;

[0013] Step 2, preparing a MnZn ferrite pre-sintered material:

[0014] The main components Fe2O3, ZnO and MnO are proportioned according to stoichiometric ratio, wherein Fe2O3 is 52.5-53.5 mol%, ZnO is 7.9-8.9 mol%, and the rest is MnO, a uniform mixed slurry is obtained by wet mixing process through wet ball milling, and after drying and crushing, pre-sintering is carried out at 800-900℃ in air atmosphere, and the furnace is cooled to obtain MnZn ferrite pre-sintered material with active spinel structure;

[0015] Step 3, doping:

[0016] The designed amount of auxiliary components is added to the MnZn ferrite pre-sintered material, deionized water is added according to the ratio of deionized water: total mass of pre-sintered material and auxiliary components = 1:1, wet ball milling is carried out for 20-40 min, and after drying, a doped powder is obtained;

[0017] Step 4, granulation and pressing:

[0018] The obtained doped powder is added with 12-15wt% PVA for granulation, and sieved, and dried at 120℃ for 9-10min to obtain granules with uniform size and good flowability, and then the granules are bidirectionally pressed into green body rings with a size of 25×15×8mm using a 16-ton press;

[0019] Step 5, sintering:

[0020] The obtained green body rings are placed in a bell jar furnace for sintering, the sintering holding temperature is 1200-1300℃, the holding time is 3-6h, and the sintering is carried out under balanced oxygen partial pressure.

[0021] Preferably, in step 1, CoMe x Fe 2-x O4, the metal element Me can be at least one of Al 3+ , Ti 4+ , Ge 4+ , Ga 3+ , Cr 3 + , Zn 2+ , Mn 3+ and the like which can improve the resistivity of CoMe x Fe 2-x O4, and the corresponding oxide impurities can be a combination of one or more of Al2O3, TiO2, GeO2, Ga2O3, Cr2O3, ZnO, Mn2O3;

[0022] Preferably, in step 3, the auxiliary components include CoMe x Fe 2-xO4, Nb2O5, ZrO2, TiO2, SnO2, and fluxes, wherein the fluxes are at least one of CaCO3, SiO2, CuO, Bi2O3;

[0023] Further, as a preferred, the total weight of the main components Fe2O3, ZnO, and MnO is 100%, and the addition amount of the auxiliary component CoMe x Fe 2-x O4: 0.1-0.4wt%, Nb2O5: 0.015-0.035wt%, ZrO2: 0.01-0.02wt%, TiO2: 0.08-0.12wt%, SnO2: 0.12-0.2wt%, and CaCO3: 0.03-0.05wt%, SiO2: 0.002-0.004wt%;

[0024] Preferably, in the step 3, the D 50 of the wet ball-milled doped powder is 1.2-1.5μm;

[0025] Preferably, in the step 4, the sieving is performed through 60-mesh and 120-mesh sieves respectively to remove large and small particles, improve the size uniformity, flowability, and bulk density of the powder, and control the density of the green body ring at 2.9-3.1g / cm 3 ;

[0026] Preferably, in the step 5, the holding temperature of the sintering is 1200-1300℃, which is lower than the sintering temperature of CoMe x Fe 2-x O4, and the O2 content is controlled at 3.5-4.2vol% under the equilibrium oxygen partial pressure in the holding stage.

[0027] A high-temperature low-loss high-permeability MnZn ferrite material is prepared by a preparation method of the high-temperature low-loss high-permeability MnZn ferrite material.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] (1) A preparation method of a high-temperature low-loss high-permeability MnZn ferrite material is provided, CoMe x Fe 2-x O4 with positive magnetic crystal anisotropy constant, high resistivity, and ferrimagnetism is doped to form a solid solution with the MnZn ferrite, which on one hand forms a complementary reduction of the positive magnetic crystal anisotropy constant of the MnZn ferrite to reduce the hysteresis loss, and on the other hand forms a high-resistance state grain boundary layer between the MnZn grains to effectively reduce the eddy current loss of the MnZn ferrite material, improve the initial permeability, and optimize the overall magnetic performance;

[0030] (2) A MnZn ferrite material with high temperature and ultra-low loss characteristics and good magnetic properties is provided. At 140℃, 100kHz and 200mT, the Pcv is 298kW / m. 3 Initial permeability μi: 3380, saturation magnetic induction Bs at 100℃: 456mT. Attached Figure Description

[0031] Figure 1 CoAl under different Al2O3 doping concentrations x Fe 2-x The resistivity of O4;

[0032] Figure 2 The loss of MnZn ferrite under different Al2O3 doping concentrations;

[0033] Figure 3 Here is a SEM image of the MnZn ferrite from Example 4;

[0034] Figure 4 The image shows the TOF-SIMS diagram of the MnZn ferrite in Example 4. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Examples 2-5 and Comparative Examples 1*, 6*-9* prepared MnZn ferrite materials according to the following method:

[0037] Step 1: Preparation of high resistivity CoMe x Fe 2-x O4 powder:

[0038] Co3O4 and Fe2O3 were mixed uniformly by wet ball milling in stoichiometric ratio. After drying, the mixture was pre-calcined at 850℃ for 2 hours in air to obtain a pre-calcined material. The pre-calcined material powder was then mixed with 0.01wt%, 0.02wt%, 0.03wt%, and 0.04wt% Al2O3 by wet ball milling, respectively. After drying, the mixture was sintered at 1350℃ in an O2 atmosphere. After crushing, grinding, and sieving, high-resistivity doped CoAl with a particle size of 0.5~1μm was obtained. x Fe 2-x O4 powder, wherein 0.01wt%, 0.02wt%, 0.03wt%, and 0.04wt% Al2O3 correspond to x=0.0005, 0.0009, 0.0014, and 0.0018, respectively.Figure 1 This shows the CoAl content at different Al2O3 doping levels. x Fe 2- x The resistivity of O4, as seen in CoAl x Fe 2-x The resistivity of O4 increases with increasing Al2O3 doping concentration; Figure 2 The loss of the prepared MnZn ferrite at 100 kHz, 200 mT, and different temperatures is shown for different Al2O3 doping concentrations. It can be seen that the loss first increases and then decreases at high temperatures. The MnZn ferrite with the lowest Al2O3 doping concentration (0.03 wt%) has the lowest loss, corresponding to CoAl... 0.0014 Fe 1.9986 O4, therefore CoAl was chosen. 0.0014 Fe 1.9986 O4 was used for subsequent experiments.

[0039] Step 2: Preparation of MnZn ferrite pre-sintered material:

[0040] The ingredients were prepared according to the metering of 53.07 mol% Fe2O3, 8.74 mol% ZnO and 38.19 mol% MnO. After one wet ball milling (300 rpm, 10 min), a uniform slurry was obtained. After drying and pulverizing, it was pre-calcined at 850℃ for 2 h in an air atmosphere. The furnace was cooled. After the reaction, a pre-calcined MnZn ferrite material with an active spinel structure was obtained.

[0041] Step 3, Doping:

[0042] Auxiliary components were added to the MnZn ferrite pre-calcined material prepared in step 2: 0.02wt% Nb2O5, 0.01wt% ZrO2, 0.08wt% TiO2, 0.12wt% SnO2, 0.04wt% CaCO3, and 0.004wt% SiO2; CoAl was added in different mass percentages as shown in Table 1 in Examples 2-5. 0.0014 Fe 1.9986 O4, as comparative examples 6*~9*, was added with an equal mass percentage of cobalt oxide (CoO). Cobalt oxide is a commonly used oxide in MnZn ferrite to change the power loss temperature point, in order to study the effect of both on the high-temperature loss of MnZn; as comparative example 1*, neither CoAl nor CoO was added. 0.0014 Fe 1.9986 O4 without CoO. Add deionized water equal in mass to the MnZn ferrite pre-calcined material and auxiliary components, and perform a second wet ball milling for 35 minutes. Dry in a 120℃ drying oven for 4 hours to obtain the doped powder. D 50 =1.2~1.5μm;

[0043] Table 1. Amount of auxiliary ingredients added in different embodiments and comparative examples

[0044]

[0045] Note: Numbered with * indicates comparative examples, i.e., 2~5 are examples, and 1*, 6*~9* are comparative examples.

[0046] Step 4, Granulation and Compression:

[0047] The doped powder obtained in step 3 was crushed and sieved, then 15 wt% PVA was added for granulation. After passing the granules through 60-mesh and 120-mesh sieves to remove large and small particles, the powder was dried at 120℃ for 9.5 minutes to obtain uniformly sized, free-flowing granules. These granules were then bidirectionally pressed into 25×15×8mm green rings using a 16-ton press, with a green density of 3.0 g / cm³. 3 ;

[0048] Step 5, Sintering:

[0049] The pressed green ring obtained in step 4 was placed into a bell furnace for sintering. The sintering temperature was 1250℃ and the holding time was 3h. Sintering was carried out under balanced oxygen partial pressure and the oxygen content in the holding section was 4.0 vol.

[0050] Electromagnetic performance testing.

[0051] The sample rings prepared according to the above steps were tested for power consumption Pcv and saturation flux density Bs using a SY8218 instrument from Iwasaki Corporation, Japan. The test conditions were as follows: Pcv was tested at 100 kHz and 200 mT; Bs was tested at 1 kHz and 1194 A / m. The results are recorded in Table 2 below.

[0052] Table 2. Performance of MnZn ferrite materials obtained in different embodiments and comparative examples

[0053]

[0054] Note: Numbered with * indicates comparative examples, i.e., 2~5 are examples, and 1*, 6*~9* are comparative examples.

[0055] The test data in the table above shows that:

[0056] Examples 2-5: Doping CoAl into MnZn ferrite 0.0014 Fe 1.9986 O4 significantly improves power loss in the high-temperature range, with optimal performance at a concentration of 0.3 wt%, resulting in a Pcv reduction to 298 kW / m² at 140°C. 3 .

[0057] Comparative examples 6* to 9* show that using CoO to improve the power loss of MnZn ferrites reveals that in the low-temperature range, as the CoO content increases, Pcv gradually decreases, and the performance gradually becomes superior to CoAl. 0.0014 Fe 1.9986 For O4, at high temperatures, Pcv initially decreases and then increases, with performance consistently inferior to CoAl. 0.0014 Fe 1.9986 O4.

[0058] Comparative Example 1*, without CoAl added 0.0014 Fe 1.9986 The auxiliary components O4 and CoO have relatively large power losses in Pcv at both room temperature and high temperature.

[0059] In summary, based on the analysis of Examples 2-5 and Comparative Examples 6*-9*, it can be concluded that CoAl 0.0014 Fe 1.9986 O4 forms a solid solution with MnZn ferrite, while CoO forms a Co solution. 2+ It entered the lattice and replaced Fe 2+ CoFe₂O₄ is formed, and the power loss and magnetic properties are optimized by utilizing the compensating effect of the positive and negative magnetocrystalline anisotropy constants of both. With increasing impurity concentration, some CoAl... 0.0014 Fe 1.9986 O4 begins to appear at the grain boundaries, forming a grain boundary layer with high magnetic resistance, which reduces eddy current loss and thus achieves high-temperature, low-loss characteristics. Figure 4 The TOF-SIMS plot of the elemental distribution of the MnZn ferrite obtained in Example 4 shows the Fe content. 3 + Co 2+ And Al 3+ The distribution of CoO. However, the CoO of CoO 2+ Continuing to enter the MnZn lattice further corrects the magnetocrystalline anisotropy, resulting in a trend where high-temperature losses first decrease and then increase, while low-temperature losses gradually decrease.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-temperature, low-loss, high-permeability MnZn ferrite material, characterized in that, Includes the following steps: Step 1: Preparation of CoAl x Fe 2-x O4 powder: Co3O4 and Fe2O3 were wet-milled in a certain proportion, pre-calcined, and then Al2O3 impurities were added for wet-milling. Finally, the mixture was sintered to obtain CoAl. x Fe 2-x In O4, x = 0.0005~0.0018; Step 2: Preparation of MnZn ferrite pre-calcined material: The main components include 52.5~53.5 mol% Fe2O3, 7.9~8.9 mol% ZnO, and the remainder is MnO. The material is wet ball-milled according to the proportion and then pre-calcined. Step 3, Doping: Add auxiliary components to the MnZn ferrite pre-calcined material, including 0.1~0.4wt% CoAl. x Fe 2-x O4, after wet ball milling, yields doped powder; Step 4, Granulation and pressing: Granulate the doped powder and press it to obtain a green body; Step 5, Sintering: Sinter the green blank to obtain high-temperature, low-loss, high-permeability MnZn ferrite material.

2. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 1, after sintering, the material is crushed, ground into powder, and sieved to obtain CoAl. x Fe 2-x The particle size of O4 powder is 0.5~1μm.

3. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 1, the pre-firing atmosphere is air, the pre-firing temperature is 750~950℃, and the pre-firing time is 1~2h; the sintering atmosphere is oxygen, and the sintering temperature is 1300℃~1400℃.

4. The preparation method of the high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 2, the pre-firing atmosphere is air, and the pre-firing temperature is 800~900℃.

5. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 3, the auxiliary components also include Nb2O5, ZrO2, TiO2, SnO2, and at least one of CaCO3, SiO2, CuO, and Bi2O3; during ball milling, the amount of deionized water added is equal to the mass of the powder, and the ball milling time is 20-40 minutes. The resulting doped powder has a D... 50 The thickness is 1.2~1.5μm.

6. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 5, characterized in that, In step 3, based on the main component, the auxiliary components are: 0.015~0.035wt% Nb2O5, 0.01~0.02wt% ZrO2, 0.08~0.12wt% TiO2 and 0.12~0.2wt% SnO2, 0.03~0.05wt% CaCO3 and 0.002~0.004wt% SiO2.

7. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 4, the amount of PVA binder added for granulation is 12-15 wt%. After granulation, the particles are passed through 60-mesh and 120-mesh sieves to remove large and small particles. The particles are then dried at 120℃ for 9-10 minutes and then bidirectionally pressed into 25×15×8mm green rings using a 16-ton press. The density of the green rings is 2.9-3.1 g / cm³. 3 .

8. The method for preparing high-temperature, low-loss, high-permeability MnZn ferrite material as described in claim 1, characterized in that, In step 5, sintering is carried out in a bell-shaped furnace under balanced oxygen partial pressure, with a holding temperature of 1200~1300℃ and a holding time of 3~6h. The O2 content during the holding stage is 3.5~4.2 vol.

9. A high-temperature, low-loss, high-permeability MnZn ferrite material, characterized in that, It was prepared using the preparation method of high-temperature, low-loss, high-permeability MnZn ferrite material as described in any one of claims 1-8.

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