High-frequency low-loss composite magnetic core material and preparation method and application thereof

Abstract

The invention discloses a high-frequency low-loss composite magnetic core material and a preparation method and application thereof, and particularly relates to the technical field of soft magnetic composite materials. The composite magnetic core material is formed by pre-sintering, pressing and sintering a matrix component and a doping component, the matrix component is prepared from Fe2O3, MnO and ZnO; the doping component is prepared from BiFeO3, SrTiO3, WO3, Co2O3, CaCO3, Nb2O5 and V2O5, and the doping component is prepared from SrTiO3, WO3, Co2O3, CaCO3 According to the invention, the synergistic effect of the matrix component and the doping component is optimized, the initial magnetic conductivity is improved while the loss is inhibited, the balance of high-frequency low loss and high magnetic conductivity is realized, and the high-performance requirement of a high-frequency power electronic device on the magnetic core material is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft magnetic composite materials, and particularly relates to a high-frequency low-loss composite magnetic core material, its preparation method and application. Background Art

[0002] Soft magnetic composite materials, especially the manganese-zinc ferrite series materials, are widely used in high-frequency power electronic devices (such as transformers, inductors, etc.) due to their high magnetic permeability and low loss characteristics. However, with the development of power electronic devices towards high frequency, miniaturization and high efficiency, traditional manganese-zinc ferrite materials have exposed significant technical bottlenecks under high-frequency (such as above 100 kHz) working conditions.

[0003] Firstly, in a high-frequency environment, the eddy current loss and dielectric polarization loss of the material increase sharply. This is because the conductivity at the grain boundaries of traditional materials is relatively high, resulting in the formation of eddy current paths between grains in an alternating magnetic field; at the same time, the dielectric constant of the material is relatively large, exacerbating the polarization loss under a high-frequency electric field. These problems not only reduce the device efficiency but also cause the magnetic core to heat up, affecting the reliability and lifespan of the equipment.

[0004] Currently, researchers have tried to improve the high-frequency performance through doping modification and process optimization, but there are still deficiencies: 1. Single doping or simple compounding is difficult to form a continuous high-resistance layer at the grain boundaries, and the regulation of the dielectric constant is insufficient; 2. It is impossible to balance low loss and high magnetic permeability; 3. The traditional sintering process has inaccurate control over the grain boundary structure and component distribution, affecting the consistency of material performance, etc. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a new type of composite magnetic core material, which optimizes the grain boundary characteristics through the synergistic effect of multiple components and combines a refined preparation process to achieve an efficient balance between high-frequency low loss and high magnetic permeability.

[0006] To achieve the above purpose, the present invention discloses the following technical solutions:

[0007] In the first aspect, the present invention provides a high-frequency low-loss composite magnetic core material, which is formed by pre-sintering, pressing and sintering a matrix component and a doping component;

[0008] Calculated by 100% mole of the matrix component, the matrix component includes the following components:

[0009] Fe2O3 51 - 52 mol%;

[0010] MnO 38 - 39 mol%;

[0011] ZnO 10 - 11 mol%;

[0012] Based on the total mass ratio of the matrix components, the doping components include the following ingredients:

[0013]

[0014] Preferably, based on 100% mole of the matrix components, the matrix components include the following ingredients:

[0015] Fe2O3 51.65 mol%;

[0016] MnO 38.21 mol%;

[0017] ZnO 10.14 mol%.

[0018] In a second aspect, the present invention provides a method for preparing the high-frequency low-loss composite magnetic core material described in the first aspect. The preparation method includes the following steps:

[0019] Step 1. Weigh a certain amount of Fe2O3, MnO, and ZnO matrix components for wet ball milling. The obtained slurry is sieved, and after sieving, it is dried until the water content ≤ 0.1% to obtain pre-treated powder;

[0020] Step 2. Pre-burn the pre-treated powder at 850 - 900 °C. After rising from room temperature to the pre-burning temperature, keep it warm for 2 - 4 h. After the pre-burning is completed, cool it to obtain the manganese-zinc ferrite matrix material, where the entire pre-burning is carried out in an air atmosphere;

[0021] Step 3. Weigh the doping components. After mixing the doping components with the manganese-zinc ferrite matrix material, carry out wet ball milling. After the ball milling is completed, add a PVA binder and mix evenly. The addition amount of the PVA binder is 0.5 - 0.8% of the total mass of the slurry. Spray granulate the uniformly mixed slurry to obtain granulated material;

[0022] Step 4. Press the granulated material into a shape to obtain a green body. Sinter the green body. In the sintering process, first raise the temperature from room temperature to 450 - 500 °C at a heating rate of 0.4 - 0.5 °C / min in an air atmosphere and keep it warm for 1 h, then raise the temperature to 1300 - 1400 °C at a rate of 4 - 5 °C / min and keep it warm for 4 - 5 h in a 92 v / v% N2 / 8 v / v% O2 mixed gas atmosphere. After the sintering is completed, cool it to room temperature to obtain the high-frequency low-loss composite magnetic core material.

[0023] Preferably, the ball milling in Step 1 is to place the Fe2O3, MnO, and ZnO matrix components in a ball mill, add steel grinding balls according to a ball-to-material ratio of 5:1, add deionized water according to a solid-to-liquid ratio of 1:1.5, and carry out ball milling at a ball milling speed of 500 r / min for 3 - 4 h.

[0024] Preferably, the slurry is sieved through a 200-mesh sieve.

[0025] Preferably, in step 2, the pretreated powder is placed in a smelting instrument, and the temperature is raised from room temperature to 270-300°C at a heating rate of 2-3°C / min. After reaching 270-300°C, it is kept warm for 1 hour to promote the complete removal of moisture adsorbed on the surface of the powder. Then, the temperature is raised from 270-300°C to 850-900°C for pre-calcination at a heating rate of 10-15°C / min.

[0026] Preferably, in step 3, the doping component and the manganese zinc ferrite material are placed in a ball mill, steel grinding balls are added at a ball-to-material ratio of 5:1, deionized water is added at a solid-liquid ratio of 1:1.5, the ball milling speed is 500 r / min, and the ball milling is completed until the slurry particle size D90 is 500-700 nm;

[0027] The PVA adhesive has a concentration of 8-10%.

[0028] Preferably, the spray granulation parameters in step 3 are set to an inlet temperature of 180-220° C., an outlet temperature of 90-110° C., and an atomization pressure of 0.3-0.8 MPa.

[0029] Preferably, the density of the pressed green body in step 4 is controlled at 2.95-3.10 g / cm 3 .

[0030] In a third aspect, the present invention provides an application of the high-frequency, low-loss composite magnetic core material described in the first aspect in the preparation of high-frequency power electronic components.

[0031] Bismuth ferrite (BiFeO3) is introduced in the present invention. Since it has a rhombohedral perovskite structure and a space group R3c, which is significantly different from the crystal structure of spinel-structured manganese-zinc ferrite, bismuth ferrite cannot be dissolved in the main phase. During the sintering process, it preferentially precipitates at the grain boundaries to form an insulating barrier, reducing high-frequency eddy current losses. At the same time, the weak ferromagnetism of bismuth ferrite can partially compensate for the dilution effect of non-magnetic additives on the magnetic permeability.

[0032] The present invention introduces strontium titanate (SrTiO3), which has a perovskite structure and a space group of Pm3m. The crystal structure of the spinel structure of manganese-zinc ferrite is significantly different. Strontium titanate cannot be dissolved into the manganese-zinc ferrite lattice and can only precipitate at the grain boundaries. At the same time, strontium titanate has a high resistivity and forms a continuous high-resistance layer at the grain boundaries, blocking the conductive path between the grains. It synergizes with tungsten trioxide at the grain boundaries to significantly suppress high-frequency eddy current losses. In addition, the dielectric constant of strontium titanate is low, which can effectively reduce the dielectric polarization loss at high frequencies and avoid heating of the magnetic core.

[0033] Strontium titanate, as a non-magnetic phase, when added in excess, will dilute the concentration of magnetic ions, causing the non-magnetic dilution effect and reducing the saturation magnetization and initial permeability. Therefore, the addition amount range of strontium titanate provided by the present invention effectively avoids this problem. Meanwhile, when used in combination with bismuth ferrite, it offsets the non-magnetic dilution effect.

[0034] The crystal structure of tungsten trioxide (WO3) is monoclinic or tetragonal, and the space group is P21 / n or P4 / nmm, which is significantly different from the space group of spinel-structured manganese-zinc ferrite and is difficult to dissolve into the main lattice. It tends to precipitate at the grain boundaries. As a high-resistivity substance, tungsten trioxide can effectively block the conductive path at the grain boundaries and inhibit high-frequency eddy current loss.

[0035] Synergistic effect: When tungsten trioxide, strontium titanate and bismuth ferrite are combined, the former reduces the grain boundary loss and the latter compensates for the permeability, achieving the balance of high-frequency low loss and high permeability.

[0036] Advantages of the present invention:

[0037] 1. By introducing doping components such as BiFeO3, SrTiO3 and WO3 into manganese-zinc ferrite, the present invention forms a high-resistivity insulating layer at the grain boundaries of manganese-zinc ferrite, synergistically blocks the intergranular conductive path, inhibits high-frequency eddy current loss, and thus significantly reduces the total power loss of the material under high-frequency applications.

[0038] 2. Optimize the synergistic effect between the matrix components and the doping components, improve the initial permeability while suppressing the loss, achieve the balance of high-frequency low loss and high permeability, and meet the high-performance requirements of high-frequency power electronic devices for magnetic core materials. Specific embodiments

[0039] The following further clearly and detailedly describes the present invention in combination with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments.

[0040] Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0041] In the present invention:

[0042] The raw materials used in the examples are all commercially available.

[0043] Preparation of composite magnetic core material

[0044] Step 1. Accurately weigh the matrix components of Fe2O3, MnO, and ZnO according to the molar percentages in Table 1, place them in a ball milling tank, add steel grinding balls at a ball-to-material ratio of 5:1, add deionized water to a solid-liquid ratio of 1:1.5. The rotation speed of the ball milling tank is 500 r / min, ball mill for 3 - 4 h, pass the obtained slurry through a 200-mesh sieve, and dry it after sieving until the water content ≤ 0.1% to obtain pretreated powder materials;

[0045] Step 2. Place the pretreated powder materials in an electric smelting crucible, raise the temperature from room temperature to 285°C at a heating rate of 3°C / min, hold for 1 h after reaching 285°C, then raise the temperature from 285°C to 900°C for pre-sintering at a heating rate of 10°C / min, hold for 2 - 4 h after reaching the pre-sintering temperature, and cool after pre-sintering is completed to obtain manganese-zinc-ferrite matrix materials, where the entire pre-sintering process is carried out in an air atmosphere;

[0046] Step 3. Accurately weigh the doping components according to the mass percentages in Table 1, place the doping components and the manganese-zinc-ferrite matrix materials in a ball milling tank, add steel grinding balls at a ball-to-material ratio of 5:1, add deionized water to a solid-liquid ratio of 1:1.5. The rotation speed of the ball milling tank is 500 r / min, ball mill until the particle size D90 of the slurry is 500 - 700 nm, then add a 10% PVA binder and mix evenly. The addition amount of the PVA binder is 0.8% of the total mass of the slurry, and spray granulate the evenly mixed slurry. The spray granulation parameters are set as an inlet temperature of 200°C, an outlet temperature of 100°C, and an atomization pressure of 0.8 MPa to obtain granulated materials;

[0047] Step 4. Use a two-way press to press the granulated materials into a ring-shaped blank with an outer diameter of 18 mm, an inner diameter of 10 mm, and a height of 6 mm. The density of the blank is controlled at 2.95 - 3.10 g / cm 3 , place the blank in a sintering furnace for sintering. During the sintering process, first raise the temperature from room temperature to 500°C at a heating rate of 0.5°C / min in an air atmosphere and hold for 1 h, then quickly raise the temperature to 1340°C at a rate of 4.5°C / min. After reaching 1340°C, hold for 4 - 5 h in a 92 v / v% N2 / 8 v / v% O2 mixed gas atmosphere, and cool to room temperature after sintering is completed to obtain a high-frequency low-loss composite magnetic core material.

[0048] Table 1 Raw material composition

[0049]

[0050] To verify the effects of the key components in the doping components and the influence of the key components on the performance of the composite magnetic core material, the doping components are defaulted and the dosage is adjusted based on the formula of Example 2, as follows:

[0051] Comparative Example 1: Lack of BiFeO3, and the rest remains unchanged;

[0052] Comparative Example 2: Lack of SrTiO3, and the rest remains unchanged;

[0053] Comparative Example 3: Lack of WO3, and the rest remains unchanged;

[0054] Comparative Example 4: Increase the dosage of BiFeO3 to 0.2 wt%, and the rest remains unchanged;

[0055] Comparative Example 5: Increase the dosage of SrTiO3 to 0.01 wt%, and the rest remains unchanged;

[0056] Comparative Example 6: Increase the dosage of WO3 to 0.02 wt%, and the rest remains unchanged.

[0057] Performance Test

[0058] Perform performance tests on the composite magnetic core materials prepared in Examples 1 - 3 and Comparative Examples 1 - 6. Each group of samples has 3 replicates, and the average value is taken;

[0059] The initial permeability test is carried out using the IWATSU SY-8219 B-H tester in Japan at 25 °C and 10 kHz;

[0060] The high-frequency power loss test is carried out under the test conditions of 100 °C, 100 kHz, and 200 mT;

[0061] The specific test results are shown in Table 2.

[0062] Table 2 Performance Test Results of Examples 1 - 3 and Comparative Examples 1 - 6

[0063] Group Initial permeability, 10 kHz <![CDATA[High-frequency power loss / kW·m -3 > Example 1 3704 242 Example 2 4183 239 Example 3 3936 244 Comparative Example 1 3117 397 Comparative Example 2 3341 427 Comparative Example 3 3256 431 Comparative Example 4 3629 343 Comparative Example 5 2914 324 Comparative Example 6 2902 311 Excellent level in the current market 3500 420

[0064] Result Analysis:

[0065] The initial permeability of Comparative Example 1 is significantly lower than that of Example 2, and the high-frequency power loss increases significantly. This indicates that BiFeO3 forms an insulating barrier by precipitating grain boundaries, effectively suppressing eddy current loss, and its weak ferromagnetism compensates for the dilution effect of non-magnetic additives, thus improving the permeability.

[0066] The high-frequency power losses of Comparative Example 2 and Comparative Example 3 reach 427 kW·m -3 and 431 kW·m -3 , respectively, which are much higher than that of Example 2. It shows that the high resistivity of SrTiO3 and the grain boundary blocking effect of WO3 cooperate to reduce the high-frequency eddy current loss, and the low dielectric constant of SrTiO3 reduces the dielectric polarization loss.

[0067] The permeability and loss of Comparative Example 4 are inferior to those of Example 2, indicating that excessive BiFeO3 leads to excessive thickening of grain boundaries, affecting the movement of magnetic domains. The permeabilities of Comparative Example 5 and Comparative Example 6 are reduced to 2914 and 2902 respectively, indicating that excessive non-magnetic phases dilute the magnetic ion concentration, verifying the necessity of defining the doping amount range in the present invention.

[0068] The comprehensive performance of Example 2 is the best, with an initial permeability of 4183 and a high-frequency power loss of only 239 kW·m -3 , significantly superior to the comparative examples and the existing market level. This indicates that the synergistic optimization of the matrix components (51.65 mol% Fe2O3, 38.21 mol% MnO, 10.14 mol% ZnO) and the doping components provided by the present invention, combined with the staged temperature-controlled sintering process, realizes the balance between grain boundary control and magnetic properties.

[0069] The above specific implementation manners further elaborate in detail the objectives, technical solutions, and beneficial effects of the embodiments of the present application. It should be understood that the above are only the specific implementation manners of the embodiments of the present application and are not used to limit the protection scope of the embodiments of the present application. Any modifications, equivalent replacements, improvements, etc. made on the basis of the technical solutions of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A high-frequency and low-loss composite magnetic core material, characterized in that, The composite magnetic core material is formed by a matrix component and a doping component through pre-sintering, pressing, and sintering; Based on 100% mol of the matrix component, the matrix component includes the following components: Fe2O3 51 - 52 mol%; MnO 38 - 39 mol%; ZnO 10 - 11 mol%; Based on the total mass ratio of the matrix component, the doping component includes the following components:

2. The high-frequency low-loss composite magnetic core material according to claim 1, wherein Based on 100% mol of the matrix component, the matrix component includes the following components: Fe2O3 51.65 mol%; MnO 38.21 mol%; ZnO 10.14 mol%.

3. The preparation method of the high-frequency low-loss composite magnetic core material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: Step 1. Weigh a certain amount of Fe2O3, MnO, and ZnO matrix components for wet ball milling. The obtained slurry is sieved, and after sieving, it is dried until the water content ≤ 0.1% to obtain pre-treated powder; Step 2. Pre-sinter the pre-treated powder at 850 - 900 °C. After rising from room temperature to the pre-sintering temperature, keep it warm for 2 - 4 h. After the pre-sintering is completed, cool it to obtain the manganese-zinc ferrite matrix material, and the entire pre-sintering is carried out in an air atmosphere; Step 3. Weigh the doping component. After mixing the doping component with the manganese-zinc ferrite matrix material, carry out wet ball milling. After the ball milling is completed, add a PVA binder and mix evenly. The addition amount of the PVA binder is 0.5 - 0.8% of the total mass of the slurry. Spray granulate the evenly mixed slurry to obtain granulated material; Step 4. Press the granulated material into a shape to obtain a green body. Sinter the green body. In the sintering process, first in an air atmosphere, raise the temperature from room temperature to 450 - 500 °C at a heating rate of 0.4 - 0.5 °C / min and keep it warm for 1 h. Then raise the temperature to 1300 - 1400 °C at a rate of 4 - 5 °C / min and keep it warm for 4 - 5 h in a 92 v / v% N2 / 8 v / v% O2 mixed gas atmosphere. After the sintering is completed, cool it to room temperature to obtain a high-frequency low-loss composite magnetic core material.

4. The preparation method according to claim 3, characterized in that, The ball milling in Step 1 is to place the Fe2O3, MnO, and ZnO matrix components in a ball mill, add steel grinding balls according to a ball-to-material ratio of 5:1, add deionized water according to a solid-to-liquid ratio of 1:1.5, and carry out ball milling at a ball milling speed of 500 r / min for 3 - 4 h.

5. The preparation method according to claim 3, characterized in that, The slurry is sieved through a 200-mesh sieve.

6. The preparation method according to claim 3, wherein In Step 2, place the pre-treated powder in a melting instrument, raise the temperature from room temperature to 270 - 300 °C, raise the temperature at a heating rate of 2 - 3 °C / min. After reaching 270 - 300 °C, keep it warm for 1 h. Then raise the temperature from 270 - 300 °C to 850 - 900 °C for pre-sintering, and raise the temperature at a heating rate of 10 - 15 °C / min.

7. The preparation method according to claim 3, wherein In Step 3, place the doping component and the manganese-zinc ferrite matrix material in a ball mill, add steel grinding balls according to a ball-to-material ratio of 5:1, add deionized water according to a solid-to-liquid ratio of 1:1.5, and carry out ball milling at a ball milling speed of 500 r / min until the particle size D90 of the slurry is 500 - 700 nm to complete the ball milling; The PVA binder is a PVA binder with a concentration of 8 - 10%.

8. The preparation method according to claim 3, characterized in that, The spray granulation parameters in Step 3 are set as an inlet temperature of 180 - 220 °C, an outlet temperature of 90 - 110 °C, and an atomization pressure of 0.3 - 0.8 MPa.

9. The preparation method according to claim 3, characterized in that, The density of the green body formed by pressing in Step 4 is controlled at 2.95 - 3.10 g / cm 3 .

10. Use of the high-frequency low-loss composite magnetic core material according to claim 1 or 2 in the preparation of high-frequency power electronic components.

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