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

Abstract

The invention 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 thereof. The material comprises main components and auxiliary components, the main components comprise Fe2O3, ZnO and MnO, and the auxiliary components comprise CoMe < x > Fe < 2-x > O < 4 > (wherein Me is a metal element), Nb2O5, ZrO2, TiO2, SnO2, and at least one of CaCO3, SiO2, CuO and Bi2O3. Wherein the CoMe < x > Fe < 2-x > O < 4 > takes CoFe2O4 as a matrix and is obtained through ion doping, the CoMe < x > Fe < 2-x > O < 4 > has the characteristics of high resistivity and low coercive force, and dual functions of regulating magnetocrystalline anisotropy constants and forming a high-resistance-state magnetic grain boundary layer between grains are realized. The MnZn ferrite material prepared by the method has excellent electromagnetic characteristics of low loss, high magnetic conductivity and high saturation flux density at a high temperature of 140 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and in particular relates to a high-temperature, low-loss, high-magnetic-permeability MnZn ferrite material and a preparation method thereof. Background Art

[0002] With the rapid development of communications, computers, and automotive electronics, such as 5G communications, servers, and new energy vehicles, as well as the impending emergence of flying cars, the demand for magnetic materials is increasing. The trend toward flatter, smaller, and more integrated modern devices is also placing higher demands on the performance of magnetic materials, such as higher operating frequencies, lower power loss, higher saturation magnetic induction, and wider operating temperatures and temperature stability. Research on MnZn ferrites, which account for over 70% of the total soft ferrite production, has been a focus of research both domestically and internationally, particularly in new energy vehicles and servers. High levels of integration and miniaturization are reducing the size of electronic devices and increasing the heat flux density within each unit during operation. This heat generation, due to inadequate heat dissipation, increases the ambient operating temperature of the device. This forces some magnetic components, such as inductors and transformers, to exhibit lower losses at higher temperatures and higher permeability to address the low inductance resulting from their small size and limited number of winding turns.

[0003] Against this backdrop, research is focusing on improving the wide-temperature characteristics of MnZn ferrites. For example, TDK's PC95 offers low power loss between 25°C and 100°C, while TDG's TPG33B exhibits good power loss performance in the low-temperature range. However, optimizing high-temperature loss performance is less than ideal because high-temperature electron transitions increase eddy current losses.

[0004] Patent CN109836146A discloses a MnZn ferrite with ultra-low high-temperature power loss and its preparation method. The main component molar percentage is: Fe2O3 is 52.9~53.4mol%, ZnO is 9.0~9.8mol%, and MnO is the balance; its additive auxiliary components are: 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 separation, as well as granulation, pressure molding and sintering under atmosphere / temperature control conditions to prepare 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 at 25℃ i It is 2600±25%.

[0005] Patent CN104591712B discloses a low-loss manganese-zinc ferrite material for use at temperatures between -20°C and 140°C and a method for its manufacture. The ferrite material comprises a main component and auxiliary components, the main component being 54.5-55.5 mol% Fe2O3, 7.5-9.5 mol% ZnO, and the remainder being MnO. The auxiliary components, based on the total weight of the main components, are 0.25-0.45 wt% Co2O3 and 0.3-0.9 wt% NiO. The remaining auxiliary components include SiO2, CaCO3, V2O5, Nb2O5, ZrO2, Ta2O5, and In2O3. The material is manufactured through a process involving batching, mixing, pre-sintering, secondary grinding, granulation, molding, and sintering. The sintered density of the material reaches 97% of the theoretical density. Within a wide temperature range of -20°C to 140°C, the power loss of the magnetic core made of this material at 100 kHz and 200 mT is less than 380 kW / m. 3 The loss at 100℃ is less than 300kW / m 3 However, its PCV performance deteriorates seriously (greater than 360kW / m 3 ).

[0006] Patent CN118271076A discloses a high-resistivity, wide-temperature, low-loss MnZn ferrite, as well as its preparation method and application. By regulating the ratio of the main components and adding high-resistivity auxiliary components (CaCO3, ZrO2, HfO2, TiO2), high-resistance grain boundaries are constructed to improve the overall resistivity of the material. Combined with a segmented, multi-step, heat-insulating sintering process, a MnZn ferrite with uniform grain size distribution, minimal pores, thin grain boundaries, and high resistance is obtained. The resistance is increased to 13.77Ω·m, thereby reducing high-temperature losses. The PCV at 100kHz, 200mT, and 120°C is 360kW / m 3 The starting magnetic permeability is about 3154. Although the material resistance is increased, the high-temperature loss performance of this patent does not show a significant advantage compared with other disclosed patents.

[0007] In summary, the development of a high-temperature, ultra-low-loss, and high-permeability MnZn ferrite has important applications and market value. Summary of the Invention

[0008] The object of the present invention is to provide a high-temperature, low-loss, high-permeability MnZn ferrite material and a preparation method thereof.

[0009] The present invention provides a novel auxiliary component CoMe x Fe 2-x O4 (Me is a doping metal element, x is the molar amount of Me replacing Fe) is used to optimize the power loss performance of MnZn ferrite, where CoMe x Fe 2-xO4 is based on CoFe2O4 and is obtained by metal ion doping. The core idea is: (1) to optimize the electrical and magnetic properties of CoFe2O4 through metal ion doping, increase the resistivity of CoFe2O4 and reduce its coercivity; (2) to use CoMe x Fe 2-x The positive magnetocrystalline anisotropy constant of O4 complements the negative magnetocrystalline anisotropy constant of MnZn ferrite, obtaining a high initial magnetic permeability while optimizing the hysteresis loss; (3) CoMe located between MnZn grains x Fe 2-x O4 acts as a high-resistance grain boundary layer, which increases the grain boundary resistance and reduces eddy current loss; (4) Compared with the traditional non-magnetic high-resistance grain boundary, ferrimagnetic CoMe x Fe 2-x When O4 is located at the grain boundary, it can effectively increase the magnetic exchange between the MnZn ferrite grains, increase the initial magnetic permeability of the material, and achieve the enhancement of the overall magnetic properties of the MnZn ferrite. Different from the general Co oxides such as CoO, Co3O4, etc., which mainly play the role of magnetocrystalline anisotropy complementation, the CoMe x Fe 2-x In addition to the functions of general Co oxide, the auxiliary component O4 also has the functions of increasing grain boundary resistance and enhancing magnetic exchange between grains.

[0010] A method for preparing a high-temperature, low-loss, high-permeability MnZn ferrite material comprises the following steps:

[0011] Step 1: Preparation of high resistivity CoMe x Fe 2-x O4 powder:

[0012] Co3O4 and Fe2O3 are mixed evenly by wet ball milling according to the stoichiometric ratio, dried and pre-fired at 750~950℃ in air atmosphere for 1~2h to obtain a pre-fired material; then impurities are added to the pre-fired material, mixed evenly by wet ball milling, dried and sintered at 1300℃~1400℃ in oxygen atmosphere, and crushed, ground and sieved to obtain high resistance doped CoMe with a particle size of 0.5~1μm. x Fe 2-x O4 powder;

[0013] Step 2: Prepare MnZn ferrite pre-sintered material:

[0014] The main components of Fe2O3, ZnO and MnO are mixed according to the stoichiometric ratio, wherein Fe2O3 accounts for 52.5-53.5 mol%, ZnO accounts for 7.9-8.9 mol%, and the rest is MnO. A wet mixing process is adopted, and a uniform mixed slurry is obtained by wet ball milling. After drying and crushing, it is pre-sintered at 800-900°C in an air atmosphere and cooled in the furnace to obtain a MnZn ferrite pre-sintered material with an active spinel structure.

[0015] Step 3: Doping

[0016] Add the designed amount of auxiliary components to the MnZn ferrite pre-calcined material, add deionized water in a ratio of deionized water: the total mass of the pre-calcined material and auxiliary components = 1:1, wet ball mill for 20-40 minutes, and obtain the doped powder after drying;

[0017] Step 4: Granulation and pressing:

[0018] 12-15 wt% PVA was added to the obtained doped powder for granulation, which was then sieved and dried at 120°C for 9-10 minutes to obtain granules with uniform size and good fluidity. The granules were then biaxially pressed into green rings of 25 × 15 × 8 mm using a 16-ton press.

[0019] Step 5: Sintering:

[0020] The obtained green ring is placed in a bell furnace for sintering. The sintering holding temperature is 1200-1300° C., the holding time is 3-6 hours, and the sintering is carried out under a balanced oxygen partial pressure.

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

[0022] Preferably, in step 3, the auxiliary component includes CoMe x Fe 2-xO4, Nb2O5, ZrO2, TiO2, SnO2, and also includes a flux, wherein the flux is at least one of CaCO3, SiO2, CuO, and Bi2O3;

[0023] Furthermore, as a preferred embodiment, based on the total weight of the main components Fe2O3, ZnO, and MnO as 100%, the amount of the auxiliary components added is 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 step 3, the D of the doped powder obtained by wet ball milling is 50 1.2~1.5μm;

[0025] Preferably, in step 4, the powder is sieved through 60-mesh and 120-mesh sieves to remove large and small particles, improve the size uniformity, fluidity and bulk density of the powder, and the density of the pressed green ring is controlled at 2.9-3.1 g / cm 3 ;

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

[0027] A high-temperature, low-loss, high-magnetic-permeability MnZn ferrite material is prepared by the method for preparing the high-temperature, low-loss, high-magnetic-permeability MnZn ferrite material.

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

[0029] (1) A method for preparing a high-temperature, low-loss, high-permeability MnZn ferrite material is provided by doping CoMe with positive magnetocrystalline anisotropy constant, high resistivity, and ferrimagnetism. x Fe 2-x O4 forms a solid solution with MnZn ferrite. On the one hand, it complements the positive magnetocrystalline anisotropy constant of MnZn ferrite to reduce hysteresis loss. On the other hand, it forms a high-resistance grain boundary layer between MnZn grains, effectively reducing the eddy current loss of MnZn ferrite material, improving the initial magnetic permeability, and optimizing the overall magnetic properties.

[0030] (2) Provided a MnZn ferrite material with high temperature ultra-low loss characteristics and good magnetic properties, at 140℃&100kHz&200mT, Pcv: 298kW / m 3 , initial magnetic permeability μi: 3380, saturation magnetic induction intensity Bs at 100℃: 456mT. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 CoAl with different Al2O3 doping amounts x Fe 2-x Resistivity of O4;

[0032] Figure 2 is the loss of MnZn ferrite at different Al2O3 doping levels;

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

[0034] Figure 4 This is the TOF-SIMS image of the MnZn ferrite of Example 4. DETAILED DESCRIPTION

[0035] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0036] Examples 2 to 5 and Comparative Examples 1*, 6* to 9* were prepared 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 evenly by wet ball milling in a stoichiometric ratio, dried and pre-calcined at 850℃ in air atmosphere for 2h to obtain pre-calcined material. The pre-calcined material powder was mixed with 0.01wt%, 0.02wt%, 0.03wt% and 0.04wt% Al2O3 by wet ball milling for a second time, dried and sintered at 1350℃ in O2 atmosphere. After crushing, grinding and screening, high resistance doped CoAl with a particle size of 0.5~1μm was obtained. x Fe 2-x O4 powder, where 0.01wt%, 0.02wt%, 0.03wt%, and 0.04wt% of Al2O3 correspond to x=0.0005, 0.0009, 0.0014, and 0.0018, respectively. Figure 1 It shows the different Al2O3 doping levels of CoAl x Fe 2- x The resistivity of O4, CoAl x Fe 2-x The resistivity of O4 increases with the increase of Al2O3 doping amount; Figure 2 The loss of MnZn ferrite prepared at different Al2O3 doping amounts at 100kHz, 200mT and different temperatures is shown. It can be seen that the loss in the high temperature section first increases and then decreases. The loss of MnZn ferrite is the lowest when the Al2O3 doping amount is 0.03wt%, corresponding to CoAl 0.0014 Fe 1.9986 O4, so CoAl is selected 0.0014 Fe 1.9986 O4 for subsequent experiments.

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

[0040] The ingredients were prepared according to the measured ratio of 53.07 mol% Fe2O3, 8.74 mol% ZnO and 38.19 mol% MnO. After a wet ball milling process (300 rpm, 10 min), a uniform mixed slurry was obtained. After drying and pulverization, the mixed slurry was pre-calcined at 850°C for 2 h in an air atmosphere. The mixed slurry was cooled in the furnace. After the reaction, an active spinel-structured MnZn ferrite pre-calcined material was obtained.

[0041] Step 3: Doping

[0042] The auxiliary components are added to the MnZn ferrite pre-sintered material prepared in step 2: 0.02wt% Nb2O5, 0.01wt% ZrO2, 0.08wt% TiO2, 0.12wt% SnO2, 0.04wt% CaCO3, 0.004wt% SiO2; in Examples 2 to 5, different mass percentages of CoAl as shown in Table 1 are added. 0.0014 Fe 1.9986 O4, as comparative examples 6*~9*, cobalt oxide (CoO) of the same mass percentage was added. Cobalt oxide is an oxide commonly used 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 0.0014 Fe 1.9986 O4 is not added with CoO. Deionized water equal to the total mass of the MnZn ferrite pre-sintered material and auxiliary components is added, and the doped powder is obtained after secondary wet ball milling for 35 minutes and drying in a drying oven at 120℃ for 4 hours. 50 =1.2~1.5μm;

[0043] Table 1 Addition amount of auxiliary components in different examples and comparative examples

[0044] Note: Numbers with * are comparative examples, i.e. 2 to 5 are examples, and 1*, 6* to 9* are comparative examples.

[0045] Step 4: Granulation and pressing:

[0046] The doped powder obtained in step 3 was crushed and sieved, and then 15 wt% PVA was added to granulate. The powder was sieved through 60 mesh and 120 mesh respectively to remove large and small particles. After drying at 120 ° C for 9.5 minutes, granules with uniform size and good fluidity were obtained. Then, a 16-ton press was used to press the powder into a 25×15×8 mm green ring with a green density of 3.0 g / cm 3 ;

[0047] Step 5: Sintering:

[0048] The pressed green ring obtained in step 4 was placed in a bell furnace for sintering. The sintering holding temperature was 1250° C. and the holding time was 3 h. The sintering was carried out under equilibrium oxygen partial pressure, and the oxygen content in the holding section was 4.0 vol%.

[0049] Electromagnetic performance test.

[0050] The sample ring prepared by the above steps was tested for power consumption Pcv and saturation magnetic flux density Bs on an SY8218 instrument from Iwasaki, Japan. The test conditions were: Pcv at 100kHz and 200mT; Bs at 1kHz and 1194A / m. The results are recorded in Table 2 below:

[0051] Table 2 Properties of MnZn ferrite materials obtained from different examples and comparative examples

[0052] Note: Numbers with * are comparative examples, i.e. 2 to 5 are examples, and 1*, 6* to 9* are comparative examples.

[0053] From the test data in the above table, we can see that:

[0054] Examples 2-5, doping CoAl into MnZn ferrite 0.0014 Fe 1.9986 When O4 is added, the power loss in the high temperature section is significantly improved. At a concentration of 0.3wt%, the performance is optimal. At 140℃, Pcv is reduced to 298kW / m 3 .

[0055] Comparative Examples 6*~9*, CoO is used to improve the power loss of MnZn ferrite. It can be seen that in the low temperature range, as the CoO content increases, Pcv gradually decreases, and the performance gradually becomes better than CoAl 0.0014 Fe 1.9986 O4, for the high temperature range, Pcv first decreases and then increases, and the performance is inferior to CoAl 0.0014 Fe 1.9986 O4.

[0056] Comparative Example 1*, without adding CoAl 0.0014 Fe 1.9986 The power loss of O4 and CoO auxiliary components is relatively large at both room temperature and high temperature.

[0057] In summary, combined with the analysis of Examples 2 to 5 and Comparative Examples 6* to 9*, it can be seen that CoAl 0.0014 Fe 1.9986 O4 forms a solid solution with MnZn ferrite, while Co 2+ Entering the lattice and replacing Fe 2+ Forming CoFe2O4, the power loss and magnetic properties are optimized by using the compensation effect of the positive and negative magnetocrystalline anisotropy constants. 0.0014 Fe 1.9986 O4 begins to appear at the grain boundaries, forming a grain boundary layer with high magnetic resistance, reducing eddy current loss, and thus obtaining high temperature and low loss characteristics. Figure 4 The TOF-SIMS diagram of the element distribution of MnZn ferrite obtained in Example 4 shows that Fe 3 + 、Co 2+ and Al 3+ However, the Co of CoO 2+ Continuing to enter the MnZn lattice, the magnetocrystalline anisotropy is further corrected, so that the high-temperature loss shows a trend of first decreasing and then increasing, and the low-temperature loss gradually decreasing.

[0058] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention 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: The following steps are involved: Step 1: Prepare CoMe x Fe 2-x O4 powder: Co3O4 and Fe2O3 are wet-milled in proportion, pre-calcined, and then the oxide impurities of the metal element Me are added and wet-milled, and then sintered; Step 2: Preparing MnZn ferrite pre-sintered material: wet-milling the main components Fe2O3, ZnO and MnO in proportion, and then pre-sintering; Step 3, doping: add auxiliary components to the MnZn ferrite pre-sintered material, the auxiliary components include 0.1~0.4wt% CoMe x Fe 2-x O4, doped powder obtained after wet ball milling; Step 4, granulation and pressing: granulating the doped powder and pressing to obtain a green body; Step 5: Sintering: Sintering the green body to obtain a high-temperature, low-loss, high-permeability MnZn ferrite material.

2. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 1, characterized in that: In the step 1, the oxide impurities are a combination of one or more of Al2O3, TiO2, GeO2, Ga2O3, Cr2O3, ZnO, and Mn2O3; after sintering, the mixture is crushed, ground, and sieved to obtain CoMe x Fe 2-x The particle size of O4 powder is 0.5~1μm.

3. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 2, characterized in that: In the step 1, the powder obtained after pre-sintering is used as the basis, the oxide impurity is 0.01~0.04wt% of Al2O3, and the CoAl x Fe 2-x In O4, x=0.0005~0.0018.

4. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 1, characterized in that: In the step 1, the pre-firing atmosphere is air, the pre-firing temperature is 750-950° C., and the pre-firing time is 1-2 hours; the sintering atmosphere is oxygen, and the sintering temperature is 1300-1400° C.

5. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 1, characterized in that: In step 2, the main components are 52.5-53.5 mol% of Fe2O3, 7.9-8.9 mol% of ZnO, and the rest is MnO; the pre-firing atmosphere is air, and the pre-firing temperature is 800-900°C.

6. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 1, characterized in that: In the step 3, the auxiliary components also include Nb2O5, ZrO2, TiO2, SnO2, and at least one of CaCO3, SiO2, CuO, and Bi2O3; during ball milling, deionized water equal to the total mass of the pre-sintered material and the auxiliary components is added, and the ball milling time is 20 to 40 minutes. The D 50 1.2~1.5μm.

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

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

9. The method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to claim 1, characterized in that: In step 5, sintering is performed in a bell furnace under a balanced oxygen partial pressure, the holding temperature is 1200-1300° C., the holding time is 3-6 hours, and the O 2 content during the holding stage is 3.5-4.2 vol%.

10. A high-temperature, low-loss, high-permeability MnZn ferrite material, characterized in that: The ferrite is prepared by the method for preparing the high-temperature, low-loss, high-permeability MnZn ferrite material according to any one of claims 1 to 9.

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