Low-frequency wide-temperature low-loss manganese-zinc ferrite material, preparation method and application thereof

Abstract

The application belongs to the field of soft magnetic ferrite material, and discloses a low-frequency wide-temperature low-loss manganese-zinc ferrite material, a preparation method and application thereof, the preparation method comprises the following steps: taking main components Fe2O3, ZnO and MnO according to a proportion, and performing sand grinding treatment to obtain mixed powder; pre-sintering to obtain pre-sintered material; adding auxiliary component high-purity metal Cu powder, performing secondary sand grinding treatment, realizing uniform wrapping of the metal Cu powder on the surface of the pre-sintered material, and obtaining doped powder with D50 of 0.9-1.3 microns; granulating and pressing to obtain a green body; sintering to obtain the manganese-zinc ferrite material. The application realizes cooperation of Cu doping and temperature and oxygen control, obtains a microstructure with uniform crystal grains, high crystal boundary resistance and low porosity, and significantly reduces the loss of the material in a wide temperature range of 25-50 kHz, and is suitable for low-frequency magnetic components such as solid-state transformers.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic ferrite materials, specifically relating to a wide-temperature, low-loss manganese-zinc ferrite material suitable for low-frequency operation at 25-50kHz, its preparation method, and its application. Background Technology

[0002] Manganese-zinc ferrite, as an important soft magnetic material, is widely used in electronic components such as switching power supplies, transformers, and inductors. With the rapid development of photovoltaic inverters, new energy vehicles, and charging piles, the market has placed higher demands on magnetic components: not only must they maintain low power loss over a wide temperature range, but they also require materials to have good long-term stability. However, most traditional manganese-zinc ferrite materials in existing technologies are optimized for high-frequency applications above 100kHz, and the proportions in their main formulations are not designed for low-frequency, high-power scenarios, resulting in insufficient magnetic performance at low frequencies.

[0003] Especially in the high-temperature range of 80-120℃, power loss increases significantly, making it difficult to meet the market's urgent demand for low-loss at high temperatures. Therefore, there is an urgent need to develop a manganese-zinc ferrite material with wide-temperature-range low-loss characteristics for low-frequency operating conditions.

[0004] Currently, the most common method to improve loss characteristics is oxide doping. However, conventional oxide doping has limitations in terms of microscopic uniformity, making it difficult to simultaneously meet multiple performance requirements such as wide temperature range, low loss, and high stability. Therefore, there is still considerable room for improvement in the precise control of grain boundary structure.

[0005] Patent CN117843357A discloses an ultra-low loss, high-Bs, wide-temperature, wide-frequency manganese-zinc ferrite material. It employs a synergistic optimization of multiple dopants, including CaO, SiO2, Nb2O5, Co2O3, TiO2, SnO2, ZrO2, V2O5, MoO3, and CuO. Through doping with low-melting-point materials and low-temperature sintering, it effectively improves the internal resistivity of the material and reduces eddy current losses. However, this technology is primarily geared towards wide-frequency applications and lacks specific optimization for the higher proportion of hysteresis losses under low-frequency operating conditions (25-50kHz). Furthermore, the multi-component doping leads to complex formulations, narrow process windows, and significant challenges in batch stability control. Patent CN107555984B discloses a method for controlling the atmosphere during the sintering process of high-frequency, wide-temperature, low-loss MnZn ferrite. This method reduces zinc loss and suppresses elemental valence changes and impurity phase precipitation at high temperatures by adjusting the oxygen partial pressure at different temperatures and during temperature variations, combined with the design of the holding time. However, this method is mainly aimed at high-frequency applications of 0.1-5MHz. For low-frequency hysteresis loss-dominated scenarios of 25-50kHz, the matching and specificity of its oxygen partial pressure curve are uncertain, making it difficult to operate in practice.

[0006] The present invention aims to overcome the problems of high loss, complex preparation process and difficulty in controlling stability of manganese zinc ferrite materials under low frequency (25-50kHz) and wide temperature operating conditions in the prior art. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for preparing low-frequency, wide-temperature, low-loss manganese-zinc ferrite materials. The low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by this method exhibits significantly reduced core loss power within a low-frequency range of 25kHz-50kHz and a temperature range of 80℃-120℃.

[0008] This invention provides a method for preparing a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material, comprising the following steps: (1) Weigh the main components Fe2O3, ZnO and MnO according to the ratio and perform sand milling to obtain mixed powder; (2) Pre-firing: The mixed powder obtained in step (1) is pre-firing to obtain pre-fired material; (3) Doping: Add high-purity metal Cu powder as an auxiliary component to the pre-sintered material obtained in step (2), and perform secondary sand milling to achieve uniform coating of metal Cu powder on the surface of the pre-sintered material, and obtain doped powder with D50 of 0.9-1.3μm; (4) Granulation and molding: Add glue to the doped powder obtained in step (3), granulate to obtain manganese zinc ferrite granules, and then press to obtain green blanks; (5) Sintering: The green blank obtained in step (4) is sintered to obtain manganese zinc ferrite material.

[0009] This invention is the first to introduce high-purity metallic Cu powder as a dopant into low-frequency, wide-temperature manganese-zinc ferrite. The metallic Cu powder uniformly coats the surface of the pre-sintered material, acting as a highly efficient flux during sintering, promoting particle rearrangement and densification, resulting in higher material density and lower porosity. This avoids the agglomeration or uneven distribution that may occur with traditional direct CuO doping. Simultaneously, Cu… 2+ It can uniformly occupy B sites, thereby optimizing the magnetocrystalline anisotropy constant and effectively reducing hysteresis loss.

[0010] Furthermore, the sintering process employs segmented temperature and oxygen control, and the sintering process is divided into the following segments: Heating phase: Increase the temperature from room temperature to 950-1050℃ at a rate of 2.0-3.0℃ / min, then continue heating at a low rate of 0.5-1.0℃ / min to 1300-1400℃. During this phase, the oxygen content is controlled at 0.05-0.1%. Insulation stage: Increase the oxygen content to 4.0-6.0% and maintain the temperature at the target temperature for 4-8 hours; Cooling phase: The oxygen content is 1.5-3.0%, and the temperature is reduced to 950-1050℃ at a rate of 1.5-2.5℃ / min, and finally reduced to room temperature at a rate of 3-5℃ / min.

[0011] The preparation method of this invention provides sufficient kinetic conditions for the full diffusion of metallic Cu by setting a heat preservation platform at around 1000℃ and using an extremely low heating rate, avoiding local Cu enrichment or CuO phase residue caused by rapid heating. Simultaneously, during the densification stage, a large amount of liquid phase is formed and grains grow rapidly, resulting in more thorough particle rearrangement. Pores trapped between grains have sufficient time to migrate along the liquid phase channels and be expelled. The significant reduction in porosity brings the density of the sintered body close to the theoretical value, while also reducing the number of pores that act as magnetic domain wall pinning centers, significantly reducing hysteresis loss. During the cooling stage, the oxygen content is controlled at a low to medium level of 1.5-3.0%, combined with a slow cooling rate of 1.5-2.5℃ / min, effectively suppressing Fe during the cooling process. 2+ Excessive oxidation.

[0012] The low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by the method of this invention achieves low loss in the 25-50kHz and 80-120℃ high-temperature range through the synergistic effect of metal Cu doping and sintering process.

[0013] Further, in step (3), the preparation and doping of metallic Cu powder includes the following steps: commercial high-purity Cu blocks and anhydrous ethanol are ball-milled for 15-25 hours at a ratio of 1g:10-20ml under a ball-to-material ratio of 20-30:1 to obtain uniform Cu powder. The powder is then mixed with anhydrous ethanol and ultrasonically dispersed to obtain uniform Cu slurry. In the secondary sand milling process of the pre-burned material, the slurry is added in 5-10 batches, with an interval of 10-15 minutes between each batch, so that the Cu slurry is uniformly coated on the surface of the main material particles.

[0014] This invention achieves uniform dispersion of Cu powder through a stepwise wet mixing process.

[0015] Furthermore, in the manganese-zinc ferrite material prepared by the above preparation method, the mass concentration of Cu powder is 100-500 ppm, based on the pre-sintered material.

[0016] Further, in step (3), the process conditions for secondary sand milling include a rotation speed of 300-500 rpm, a grinding time of 60-100 min, and a ratio of the total mass of the pre-burned material and auxiliary components to the total mass of the steel balls used for grinding of 1:4-8.

[0017] Furthermore, in step (1), the amount of each component of the main component includes 52.0-55.5 mol% Fe2O3, 8.5-12.0 mol% ZnO and the balance MnO.

[0018] Furthermore, in step (2), the pre-firing temperature is 700-1000℃, the holding time is 3-4h, and the pre-firing atmosphere is air.

[0019] Further, in step (3), the auxiliary components also include at least one of CaCO3, Nb2O5, Co2O3, Al2O3, Bi2O5, and SiO2. Preferably, in the prepared manganese-zinc ferrite material, based on the pre-calcined material, the mass concentrations of each component are as follows: CaCO3 200-800ppm, Nb2O5 200-400ppm, Co2O3 3000-6000ppm, Al2O3 100-300ppm, Bi2O5 200-600ppm, and SiO2 50-100ppm.

[0020] Further, in step (4), the glue is polyvinyl alcohol, and its amount is 7-15 wt% of the mass of the abrasive; after granulation, the granules are sieved using a 100-150 mesh screen; in the pressing process, the pressing pressure is controlled at 60-220 N.

[0021] The present invention also aims to provide a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by the above-mentioned preparation method.

[0022] The present invention also aims to provide an application of the above-mentioned low-frequency, wide-temperature, low-loss manganese-zinc ferrite material in magnetic components operating at frequencies of 25-50kHz.

[0023] The preparation method of this invention includes ingredient mixing, pre-firing, doping, granulation and molding, and sintering. Cu powder is ball-milled and ultrasonically processed to form a Cu slurry, which is then added in stages during secondary sand milling. Sintering employs segmented temperature and oxygen control: the heating stage has a holding platform at 1000℃, with a heating rate of 0.5-1.0℃ / min to promote Cu production. 2+ Occupying the B site also facilitates pore discharge; the oxygen content in the insulation section is increased to 4.0-6.0%, thus forming a high-resistivity grain boundary layer; the oxygen content in the cooling section is 1.5-3.0%, preventing Fe... 2+ Excessive oxidation. This invention achieves a microstructure with uniform grains, high grain boundary resistance, and low porosity through Cu doping combined with temperature and oxygen control, resulting in ultra-low losses in the material over a wide temperature range of 25-50kHz, making it suitable for low-frequency magnetic components such as solid-state transformers.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by the method of the present invention has a core loss power P in the low-frequency range of 25kHz-50kHz and the temperature range of 80℃-120℃. cv Significantly reduced, down to as low as 129kW / m 3 the following; (2) This invention introduces high-purity metallic Cu powder as a dopant into low-frequency, wide-temperature manganese-zinc ferrite for the first time. Uniform dispersion of Cu powder is achieved through a stepwise wet mixing process. The metallic Cu powder plays a unique fluxing role during sintering, promoting particle rearrangement and densification, resulting in higher material density and lower porosity. This avoids the agglomeration or uneven distribution that may occur with traditional direct CuO doping. Simultaneously, Cu… 2+ Entering the B position helps to adjust the magnetocrystalline anisotropy constant to a better range and effectively reduce hysteresis loss; (3) The present invention constructs a low-oxygen atmosphere platform (oxygen content <0.5%) after reaching about 1000℃, and passes through the key temperature zone of 1000-1300℃ at an extremely low heating rate (0.5-1.0℃ / min), which ensures the chemical uniformity and micro-density of the material. At the same time, the oxygen content is increased to 4.0-6.0% in the high-temperature heat preservation section, which is conducive to the formation of a high-resistivity grain boundary layer, reducing eddy current loss, and promoting the combination of Cu and O2, accelerating the transfer of pores, thereby further improving the density of the material. Attached Figure Description

[0025] Figure 1 SEM image (1000×) of the manganese-zinc ferrite material prepared in Example 1. Figure 2 SEM image (1000×) of the manganese-zinc ferrite material prepared in Comparative Example 1. Figure 3 SEM image (1000×) of the manganese-zinc ferrite material prepared in Comparative Example 3. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] In order to overcome the problems of high loss, complex preparation process and difficulty in controlling stability of manganese zinc ferrite materials under low frequency (25-50kHz) and wide temperature conditions in the prior art, the present invention aims to provide a preparation method and application of low frequency wide temperature low loss manganese zinc ferrite materials.

[0028] The present invention provides a method for preparing and applying a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material. The core idea is as follows: (1) By ball milling commercial high-purity Cu blocks with anhydrous ethanol in a specific ratio for 15-25 hours, combined with ultrasonic dispersion, a uniform Cu slurry is prepared. The slurry is then added in 5-10 batches during the secondary sand milling process to achieve a highly uniform coating of metallic Cu powder on the surface of the pre-sintered material. The metallic Cu powder plays an efficient fluxing role in the sintering process, promoting particle rearrangement and densification. At the same time, Cu... 2+ It can uniformly occupy B sites, thereby optimizing the magnetocrystalline anisotropy constant and effectively reducing hysteresis loss; (2) By setting a heat preservation platform at 1000℃ and using an extremely low heating rate, sufficient kinetic conditions are provided for the full diffusion of metal Cu, avoiding local Cu enrichment or CuO phase residue caused by rapid heating; at the same time, during the heating densification stage, a large amount of liquid phase is formed and the grains grow rapidly, making the particle rearrangement more complete, and the pores sealed between the grains have sufficient time to migrate along the liquid phase channel and be discharged from the body. The significant reduction in porosity makes the density of the sintered body close to the theoretical value, and at the same time reduces the number of pores that serve as the pinning center of the magnetic domain wall, which has a significant effect on reducing hysteresis loss; while in the cooling stage, the oxygen content is controlled at a low level of 1.5-3.0%, combined with a slow cooling rate of 1.5-2.5℃ / min, which effectively suppresses Fe during the cooling process. 2+ Excessive oxidation.

[0029] This invention provides a method for preparing a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material, comprising the following steps: Step 1, Ingredients and Mixing: The main components consist of 52.0-55.5 mol% Fe2O3, 8.5-12.0 mol% ZnO and the balance MnO. After weighing according to the above proportions, the mixture is wet-milled using a planetary vertical sand mill to obtain the mixed powder. The milling time is 10-30 min. Step 2, Pre-firing: The mixed powder obtained in Step 1 is pre-firing and then naturally cooled in the furnace to obtain pre-fired material; Step 3, Doping: The pre-burned material obtained in Step 2 is sieved, and then auxiliary components are added. Based on the mass of the pre-burned material, the auxiliary components include CaCO3, Nb2O5, Co2O3, Al2O3, Bi2O5, SiO2 and high-purity metallic Cu powder. They are weighed in proportion and mixed in a sand mill to obtain doped powder with a D50 of 0.9-1.3μm. Step 4, Granulation and molding: Add glue to the doped powder obtained in step 3, granulate and sieve to obtain manganese zinc ferrite powder, and then press to obtain green body; Step 5, Sintering: The green body obtained in Step 4 is sintered. The specific sintering process is controlled in the following segments: Heating phase: Increase the temperature from room temperature to 1000℃ at a rate of 2.0-3.0℃ / min, then continue heating at a low rate of 0.5-1.0℃ / min to 1300-1400℃. During this phase, the oxygen content is controlled at 0.05-0.1%. Insulation stage: Increase the oxygen content to 4.0-6.0% and maintain the temperature at the target temperature for 4-8 hours; Cooling phase: The oxygen content is 1.5-3.0% and the temperature is reduced to 1000℃ at a rate of 1.5-2.5℃ / min, and finally reduced to room temperature at a rate of 3-5℃ / min.

[0030] Furthermore, in step 2, the pre-firing temperature is 700-1000℃, the holding time is 3-4h, and the pre-firing atmosphere is air.

[0031] Furthermore, in step 3, the content of auxiliary components is CaCO3: 200-800ppm, Nb2O5: 200-400ppm, Co2O3: 3000-6000ppm, Al2O3: 100-300ppm, Bi2O5: 200-600ppm, SiO2: 50-100ppm, and the content of added metallic Cu powder is 100-500ppm.

[0032] Furthermore, in step 3, the preparation and doping of the metallic Cu powder are carried out according to the following steps: First, commercial high-purity Cu blocks and anhydrous ethanol are added to a ball mill at a ratio of 1g:(10-20ml), and ground for 15-25 hours at a ball-to-material ratio of 25:1 to obtain uniform granular Cu powder. Next, take an appropriate amount of the obtained Cu powder and mix it with a small amount of anhydrous ethanol. Disperse the mixture by ultrasonication for 20-40 minutes to prepare a uniformly dispersed Cu slurry. Finally, during the secondary sand milling process, the prepared Cu slurry is added to the ball mill jar for wet mixing in 5-10 batches (each batch 10-15 minutes apart). Through batch addition and process control, the Cu slurry is uniformly coated on the surface of the main material particles.

[0033] Furthermore, in step 3, the process conditions for secondary sand milling are as follows: rotation speed is 300-500 rpm, grinding time is 60-100 min; and the ratio of the total mass of the pre-burned material and auxiliary components to the total mass of the steel balls used is 1:(4-8).

[0034] Furthermore, in step 4, the added adhesive is polyvinyl alcohol, and its dosage is 7-15 wt% of the mass of the abrasive; after granulation, the granules are sieved using a 100-150 mesh screen; in the pressing process, the pressing pressure is controlled at 60-220 N.

[0035] The low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by the above method achieves low loss at 25-50kHz through the synergistic effect of Cu doping and sintering process, and can be applied to magnetic components with operating frequencies of 25-50kHz.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0037] (1) This invention provides a method for preparing a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material. The loss performance of the prepared low-frequency, wide-temperature, low-loss manganese-zinc ferrite material is as follows: P cv ≤129kW / m 3 (25kHz, 300mT, 80℃); P cv ≤138kW / m 3 (25kHz, 300mT, 100℃); P cv ≤143kW / m 3 (25kHz, 300mT, 120℃); P cv ≤320kW / m 3 (50kHz, 300mT, 80℃); P cv ≤339kW / m 3 (50kHz, 300mT, 100℃); P cv ≤368kW / m 3 (50kHz, 300mT, 120℃).

[0038] (2) This invention is the first to introduce high-purity metallic Cu powder as a dopant into low-frequency, wide-temperature manganese-zinc ferrite, achieving uniform dispersion of Cu powder through a stepwise wet mixing process. The metallic Cu powder plays a unique fluxing role during sintering, promoting particle rearrangement and densification, resulting in higher material density and lower porosity, avoiding the agglomeration or uneven distribution that may occur with traditional direct CuO doping. Simultaneously, Cu… 2+ Entering position B helps to adjust the magnetocrystalline anisotropy constant to a better range, effectively reducing hysteresis loss.

[0039] (3) This invention constructs a low-oxygen atmosphere platform (oxygen content <0.5%) after 1000℃ and passes through the critical temperature range of 1000-1300℃ at an extremely low heating rate (0.5-1.0℃ / min), ensuring the chemical homogeneity and micro-density of the material. At the same time, increasing the oxygen content to 4.0-6.0% in the high-temperature holding section is beneficial for the formation of a high-resistivity grain boundary layer, reducing eddy current loss, and promoting the combination of Cu and O2, accelerating the transfer of pores and thus improving the density of the material.

[0040] Example 1

[0041] 1. Ingredients and mixing: Weigh the raw materials according to the ratio of Fe2O3 53.8mol%, ZnO 10.6mol%, MnO 35.6mol%, add them to a planetary vertical sand mill, and wet sand mill them for 14 minutes with anhydrous ethanol as the medium to obtain mixed powder.

[0042] 2. Pre-firing: The mixed powder is pre-firing at 850℃ for 3.5 hours in air atmosphere, and then cooled in the furnace to obtain pre-fired material.

[0043] 3. Doping: After sieving the pre-burned material, add CaCO3: 550ppm, Nb2O5: 350ppm, Co2O3: 4600ppm, Al2O3: 250ppm, Bi2O5: 450ppm, SiO2: 90ppm, and 300ppm of metallic Cu powder according to the mass of the pre-burned material.

[0044] The metallic Cu powder is prepared and doped using the following method: First, commercial high-purity Cu blocks and anhydrous ethanol were added to a ball mill at a ratio of 1g:18ml, with a ball-to-material ratio of 25:1, and milled for 20 hours to obtain granular Cu powder (D50 approximately 1.2μm). Next, take an appropriate amount of Cu powder and a small amount of anhydrous ethanol, mix them, and ultrasonically disperse them for 35 minutes to prepare Cu slurry. Finally, during the secondary sand milling and mixing, Cu slurry was added to the ball mill jar in 8 batches (each 13 min apart), with a sand milling speed of 420 rpm and a time of 90 min. The material-to-ball ratio was 1:6, resulting in doped powder with a D50 of 1.1 μm.

[0045] 4. Granulation and molding: Add 12wt% polyvinyl alcohol adhesive to the doped powder, granulate, pass through a 120-mesh sieve, and press into a ring-shaped green body with a diameter of 25mm × 15mm × 7.5mm under a pressure of 150kN.

[0046] 5. Sintering: Place the green billet in a sintering furnace and heat it to 1000℃ at a rate of 2.5℃ / min, then heat it to 1350℃ at a rate of 0.8℃ / min, during which the oxygen content is controlled at 0.08%; then increase the oxygen content to 5.0% and hold it at 1350℃ for 6 hours; when cooling down, control the oxygen content at 2.0% and cool down to 1000℃ at a rate of 2.0℃ / min, and finally cool down to room temperature at a rate of 4℃ / min.

[0047] Example 2

[0048] The results are basically the same as in Example 1, except that: the main components are Fe2O3 52.8mol%, ZnO 9.6mol%, MnO 37.6mol%; the amount of Cu powder doped is 150ppm; the maximum sintering temperature is 1320℃; and the oxygen content is controlled as follows: 0.06% in the low oxygen section and 4.5% in the heat preservation section.

[0049] Example 3

[0050] The results are basically the same as in Example 1, except that: the main components are Fe2O3 54.8 mol%, ZnO 11.6 mol%, MnO 33.6 mol%; the amount of Cu powder doped is 450 ppm; the maximum sintering temperature is 1390℃; and the oxygen content is controlled as follows: 0.06% in the low oxygen section and 4.5% in the heat preservation section.

[0051] Comparative Example 1 (without copper powder doping) Compared with Example 1, the only difference is that no metallic Cu powder is added, while all other conditions are the same.

[0052] Comparative Example 2 (Conventional CuO doping replaces metallic Cu powder) Compared with Example 1, the difference is that the metallic Cu powder is replaced with an equimolar amount of CuO (about 375 ppm), while other conditions are the same.

[0053] Comparative Example 3 (Traditional Sintering Process) Compared with Example 1, the difference is that a low-oxygen platform and segmented temperature control are not used during sintering, but the temperature is directly raised to 1350°C in the air and held.

[0054] Performance testing 1. The manganese-zinc ferrite toroidal samples prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to tests on their initial permeability μi and power loss P. cv Testing. μi was measured using a ring-shaped sample at 25°C, 10kHz, and 5mV using a KEYSIGHT E4980A. P cvThe same ring-shaped sample was used for the test. The BH analyzer (Iwasaki 8218) was used to measure the magnetic flux density at specified frequencies (25 kHz, 50 kHz) and magnetic flux density (300 mT) at different temperature points such as 25℃, 80℃, 100℃, and 120℃.

[0055] The test results are shown in Table 1.

[0056] Table 1. Power loss test data for each test case (25kHz, 300mT; 50kHz, 300mT)

[0057] The data in the table show that Examples 1-3 all exhibited low power loss within a wide temperature range of 25-120℃ under the corresponding test conditions, with Example 3 showing the best performance. Compared with Comparative Example 1, the addition of metallic Cu powder significantly reduced losses (approximately 23% reduction at 100℃); compared with Comparative Example 2, the doping effect of metallic Cu powder was superior to conventional CuO doping; and compared with Comparative Example 3, the sintering process of this invention significantly reduced losses.

[0058] Figure 1 , Figure 2 and Figure 3 The images show SEM images of manganese-zinc ferrites prepared in Example 1, Comparative Example 1, and Comparative Example 3, respectively. It can be seen that the ferrite grains obtained in Example 1 have better size uniformity, higher material density, straighter and clearer continuous grain boundary morphology, and significantly reduced porosity compared to Comparative Example 1 and Comparative Example 3.

[0059] In summary, this invention achieves a microstructure with uniform grains, high grain boundary resistance, and low porosity through Cu doping and synergistic temperature and oxygen control, enabling the material to exhibit ultra-low losses in a wide temperature range of 25-50kHz, making it suitable for low-frequency magnetic components such as solid-state transformers.

[0060] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention and should be defined by the claims.

Claims

1. A method for preparing a low-frequency, wide-temperature, low-loss manganese-zinc ferrite material, characterized in that, Includes the following steps, (1) Weigh the main components Fe2O3, ZnO and MnO according to the ratio and perform sand milling to obtain mixed powder; (2) Pre-firing: The mixed powder obtained in step (1) is pre-firing to obtain pre-fired material; (3) Doping: Add high-purity metal Cu powder as an auxiliary component to the pre-sintered material obtained in step (2), and perform secondary sand milling to achieve uniform coating of metal Cu powder on the surface of the pre-sintered material, and obtain doped powder with D50 of 0.9-1.3μm; (4) Granulation and molding: Add glue to the doped powder obtained in step (3), granulate to obtain manganese zinc ferrite granules, and then press to obtain green blanks; (5) Sintering: The green blank obtained in step (4) is sintered to obtain manganese zinc ferrite material.

2. The preparation method according to claim 1, characterized in that, In step (5), sintering is carried out using segmented temperature and oxygen control. The sintering process is divided into the following segments: Heating phase: Increase the temperature from room temperature to 950-1050℃ at a rate of 2.0-3.0℃ / min, then continue heating at a low rate of 0.5-1.0℃ / min to 1300-1400℃. During this phase, the oxygen content is controlled at 0.05-0.1%. Insulation stage: Increase the oxygen content to 4.0-6.0% and maintain the temperature at the target temperature for 4-8 hours; Cooling phase: The oxygen content is 1.5-3.0%, and the temperature is reduced to 950-1050℃ at a rate of 1.5-2.5℃ / min, and finally reduced to room temperature at a rate of 3-5℃ / min.

3. The preparation method according to claim 1, characterized in that, In step (3), the preparation and doping of metallic Cu powder includes the following steps: commercial high-purity Cu blocks and anhydrous ethanol are ball-milled for 15-25 hours at a ratio of 1g:10-20ml under a ball-to-material ratio of 20-30:1 to obtain uniform Cu powder. The powder is then mixed with anhydrous ethanol and ultrasonically dispersed to obtain uniform Cu slurry. This slurry is added to the pre-calcined material in the secondary sand milling process in 5-10 batches, with an interval of 10-15 minutes between each batch, so that the Cu slurry is uniformly coated on the surface of the main material particles.

4. The preparation method according to claim 3, characterized in that, The process conditions for secondary sand milling include a rotation speed of 300-500 rpm, a grinding time of 60-100 min, and a ratio of the total mass of the pre-burned material and auxiliary components to the total mass of the steel balls used for grinding of 1:4-8.

5. The preparation method according to claim 1, characterized in that, In the manganese-zinc ferrite material prepared by the preparation method, based on the pre-burned material, the mass concentration of metal Cu powder is 100-500ppm; in step (1), the amount of each component of the main component includes 52.0-55.5mol% Fe2O3, 8.5-12.0mol% ZnO and the balance MnO.

6. The preparation method according to claim 1, characterized in that, In step (3), the auxiliary components also include at least one of CaCO3, Nb2O5, Co2O3, Al2O3, Bi2O5, and SiO2; based on the pre-burned material, the mass concentrations of each component are as follows: CaCO3 200-800ppm, Nb2O5 200-400ppm, Co2O3 3000-6000ppm, Al2O3 100-300ppm, Bi2O5 200-600ppm, and SiO2 50-100ppm.

7. The preparation method according to claim 1, characterized in that, In step (4), the glue is polyvinyl alcohol, and its amount is 7-15 wt% of the mass of the abrasive; after granulation, the granules are sieved using a 100-150 mesh screen; in the pressing process, the pressing pressure is controlled at 60-220 N.

8. A low-frequency, wide-temperature, low-loss manganese-zinc ferrite material prepared by the preparation method according to any one of claims 1-7.

9. The application of the low-frequency, wide-temperature, low-loss manganese-zinc ferrite material as described in claim 8 in magnetic components operating at frequencies of 25-50kHz.

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