High-bs low-loss megahertz mn-zn power ferrite and method for manufacturing the same

Abstract

A high Bs low-loss megahertz manganese-zinc power ferrite comprises main components and auxiliary components, the main components are 53.50-55.50 mol% Fe2O3, 3.5-5.5 mol% ZnO and 40.0-43.0 mol% MnO; and the auxiliary components are 0.01-0.03 wt% V2O5, 0.01-0.03 wt% ZrO2, 0.1-0.4 wt% Co2O3 and 0.03 wt% CaSiO3 based on the pre-sintered material after pre-sintering of the main components. The auxiliary component CaSiO3 is introduced in the application, the melting point of CaSiO3 is high, the CaSiO3 plays a role in inhibiting grain growth in the sintering process, the pores in the ferrite are easily moved from the inside of the grain to the grain boundary and escape outward through the grain boundary, the porosity is reduced, the sintering density is improved, and the CaSiO3 is enriched at the grain boundary to form a high-resistance layer, the material grain boundary resistance is improved, and the high-frequency loss is reduced.

Description

Technical Field

[0001] This invention relates to a high-Bs, low-loss megahertz manganese-zinc power ferrite and its preparation method. Background Technology

[0002] With the application of third-generation semiconductors such as SiC and GaN in switching power supplies, the operating frequency of these power supplies has expanded to above MHz, placing new demands on the power loss, permeability, and saturation magnetic flux density of magnetic materials used in switching power supply transformers. MnZn power ferrites have become a research focus due to their high resistivity, high Bs, and relatively high initial permeability. Currently, industrially applied MnZn power ferrites still exhibit high losses in the MHz frequency band and high-power applications, affecting power supply efficiency. Therefore, there is an urgent need to develop power ferrite materials with low losses and high Bs to meet the requirements of high-power switching power supplies at MHz frequencies.

[0003] In recent years, domestic and foreign magnetic material R&D companies have successively launched MnZn power ferrite materials with MHz operating frequencies. TDK Corporation of Japan launched PC200 material, which has an application frequency band of 700–4000 kHz and an initial permeability of μ. i =800, saturation magnetic induction intensity B s =410mT (100℃), Curie temperature Tc = 280℃, loss is 150kw / m under 1MHz and 50mT conditions. 3 The loss at 80℃, 2MHz, and 30mT is 160kW / m. 3 (80℃); Hitachi Metals' ML91S material, used in the 1–3 MHz frequency band, has an initial permeability μ i =900, Curie temperature Tc = 280℃, saturation magnetic induction intensity B s =430mT (100℃), loss is 700kw / m under 1MHz and 75mT conditions. 3 (100℃); The TP5E material launched by Tiantong Company in China has an application frequency band of 1-3MHz and an initial permeability μ i =1200±25%, saturation magnetic induction intensity Bs=520 (25℃), Curie temperature Tc=270℃, loss is 300kw / m under 1MHz and 50mT conditions. 3 (100℃), loss is 150kw / m under 3MHz and 10mT conditions. 3 (100℃); The DMR51 material launched by Dongci Company has an application frequency band of 1-5MHz, a saturation magnetic induction intensity Bs of 430 (100℃), and an initial permeability μ. i=900±25%, Curie temperature Tc=290℃, power loss at 1MHz and 50mT is 100kW / m 3 (100℃), at 3MHz and 30mT, the loss is 400kW / m. 3 (100℃).

[0004] Regarding MnZn power ferrites for use in the MHz frequency band, Chinese Patent No. CN 116813320 A discloses "A MnZn Ferrite for MHz Frequency," whose main components include 53.50–56.10 mol% Fe₂O₃, 0.50–1.00 mol% ZnO, 41.8–44.80 mol% MnO, and 0.15–0.5 mol% ZrO₂; its additives include 1000–2400 ppm CaCO₃, 30–50 ppm SiO₂, 600 ppm Ta₂O₅, 100–1000 ppm LiBO₂, and 1000 ppm TiO₂. It utilizes the low melting point of LiBO₂ and the high resistivity of CaCO₃ to lower the sintering temperature of the ferrite, achieving a sintering density of 4.8 g / cm³ at 1000°C. 3 At 1MHz and 30mT, the loss is 385–664 kW / m. 3 (25~140℃); Chinese Patent No. CN 108424136A discloses "MnZn Power Ferrite for MHz-level Switching Power Supply and its Preparation Method", which provides a method for preparing high-frequency MnZn power ferrite. The main components include 52~56mol% Fe2O3 and 5~11mol% ZnO, 33~43mol% MnO, and the additive components are: 0.05~0.1wt% CaCO3, 0.1~0.3wt% TiO2, 0.1~0.3wt% Co2O3, 0.01~0.1wt% SnO2 and 0.01~0.1wt% V2O5. This method of ferrite preparation lowers the sintering temperature and effectively reduces the loss of ferrite at high frequencies (MHz). The material has an initial permeability μi = 1351 and a saturation magnetic induction Bs = 425 (100℃). It exhibits low loss over a wide frequency range of 0.5–3MHz and a temperature range of 25–100℃, specifically 30–60 kW / m at 1MHz and 30mT. 3 (25~100℃), 3MHz, 10mT loss is 133~208kw / m 3(25~100℃); Chinese Patent No. CN 115196958 A discloses "A High-Frequency Wide-Temperature MnZn Ferrite and Its Preparation Method", in which the main components are 69.5~76.5mol% Fe2O3, 17.1~29.3mol% Mn3O4, and the balance is ZnO; based on the weight of the main components, the additives and auxiliary components are 0.10~0.05wt% ZrO2, 0.1-0.30wt% Co3O4, 0.04~0.14wt% CaCO3 and 0.002~0.02wt% SiO2. This invention utilizes the compensation effect of the magnetocrystalline anisotropy constant K1 of Co3O4 to reduce the temperature coefficient of loss and achieve wide-temperature characteristics. It also leverages the grain-refining effect of ZrO2 and the high resistivity of SiO2 and CaCO3 to increase grain boundary resistance and reduce loss. The resulting sample exhibits a loss of 108–150 kW / m² under conditions of 5 MHz and 9 mT. 3 (0~100℃).

[0005] Regarding high-Bs, high-frequency, low-loss MnZn ferrite materials, Chinese Patent No. CN 108911733 A discloses "A Low-Power, High-Bs, High-Frequency MnZn Ferrite Material and Its Preparation Method." The main components are Fe2O3 50.5–53.5 mol%, ZnO 6.9–12 mol%, MnO 35–39.8 mol%, and additives including CaCO3 100–700 ppm, SiO2 10–100 ppm, MoO3 300–100 ppm, Nb2O5 150–300 ppm, V2O5 150–300 ppm, and ZrO2 100–300 ppm. The optimal performance of this material is Bs = 510 mT (room temperature) and initial permeability μ. i =1600, with a loss of 120kw / m under test conditions of 500KHz and 75mT. 3 (Room temperature); Chinese Patent No. CN 109384463 B discloses "High-Frequency High-Efficiency Conversion MnZn Ferrite and its Preparation Method", the main components of which are Fe2O3 53-55 mol%, ZnO 6.5-9.5 mol%, MnO 37.2-38.5 mol%, and additive components are CaCO3 0.5-0.2 wt%, SiO2 0.05-0.2 wt%, Nb2O5 0-0.05 wt%, and Ta2O5 0.05-0.15 wt%. The saturation magnetic induction intensity Bs = 410 mT (100℃) and the initial permeability μ i =1050±20%, Curie temperature Tc=240℃, loss is 200kw / m under 1MHz and 30mT conditions. 3(100℃); Chinese Patent No. CN102311263 A discloses "High-Frequency Low-Loss High-Bs Ferrite Material for LED Lighting and Switching Power Supply Transformers and its Preparation Method," in which the main components are 40-54 mol% Fe2O3, 39-42 mol% MnO, and 5-9 mol% ZnO, and the additive components are CaCO3 250-1200 ppm, Bi2O3 100-1000 ppm, MoO 3 80-600 ppm, and NiO 200-5000 ppm. The saturation magnetic induction intensity Bs of this material is 430 mT (100℃), and the loss is 26-120 kW / m under 500 kHz and 50 mT conditions. 3 (25~100℃).

[0006] In summary, the currently published high-Bs high-frequency MnZn power ferrites have a saturation magnetic induction intensity Bs = 410–430 mT at 100℃. They exhibit low losses in high-frequency, low-power applications (500 kHz–1 MHz, B < 50 mT; 1–3 MHz, B < 30 mT), but high losses in high-frequency, high-power applications. Therefore, there is an urgent need to develop MnZn power ferrite materials that simultaneously possess high Bs and low-loss characteristics in high-frequency, high-power applications to meet the requirements of magnetic devices for high current resistance at high operating temperatures. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the background technology by proposing a high-Bs, low-loss MnZn power ferrite for use at MHz frequencies and its preparation method. This invention optimizes the formulation by doping with CaSiO3, thereby increasing Bs and reducing eddy current losses to prepare a MnZn power ferrite with high Bs and low high-frequency, low-loss performance. The saturation magnetic induction intensity Bs of this MnZn power ferrite is >530mT (25℃) and 440mT (100℃), and the loss is 5–25 kW / m² under conditions of 500 kHz and 50mT. 3 (25~120℃); loss is 50~120kw / m under 1MHz and 50mT conditions. 3 (25~120℃); loss is 210~520kw / m under 2MHz, 50mT conditions. 3 (25~120℃).

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A high-Bs, low-loss MHz manganese-zinc power ferrite comprises a main component and auxiliary components; wherein, the main component, by molar percentage of oxides, comprises: 53.50–55.50 mol% Fe₂O₃, 3.5–5.5 mol% ZnO, and 40.0–43.0 mol% MnO; based on the mass of the pre-calcined material after pre-calcination of the main component, the auxiliary components comprise: 0.01–0.03 wt% V₂O₅, 0.01–0.03 wt% ZrO₂, 0.1–0.4 wt% Co₂O₃, and 0.03 wt% CaSiO₃.

[0010] Preferably, the main components, based on the molar percentage of oxides, include: 54.50 mol% Fe2O3, 4.5 mol% ZnO, and 41.0 mol% MnO; and based on the mass of the pre-calcined material after pre-calcination of the main components, the auxiliary components include: 0.02 wt% V2O5, 0.025 wt% ZrO2, 0.3 wt% Co2O3, and 0.03 wt% CaSiO3.

[0011] The pre-calcined material is prepared using the following process: Fe2O3, ZnO, and MnO are used as raw materials. The main components are calculated and weighed according to the formula: 53.50–55.50 mol% Fe2O3, 3.5–5.5 mol% ZnO, and 40.0–43.0 mol% MnO. The weighed raw materials are placed in a planetary ball mill for one ball milling for 2–3 hours. After ball milling, the materials are dried and sieved to obtain the first-milled powder. The first-milled powder is placed in a bell-shaped furnace and pre-calcined in air atmosphere at a temperature of 800–1000℃ for 2–4 hours. After pre-calcination, the materials are sieved to obtain the pre-calcined material.

[0012] A high-Bs, low-loss megahertz manganese-zinc power ferrite includes the following steps:

[0013] Step 1, Ingredients:

[0014] Using Fe2O3, ZnO, and MnO as raw materials, the raw materials were calculated and weighed according to the main components of "53.50-55.50 mol% Fe2O3, 3.5-5.5 mol% ZnO, and 40.0-43.0 mol% MnO".

[0015] Step 2, First ball milling:

[0016] Place the raw material weighed in step 1 into a planetary ball mill, add steel balls and deionized water, and perform ball milling once for 2 to 3 hours. After ball milling, dry the raw material and pass it through a 60-mesh sieve to obtain the first-milled powder.

[0017] Step 3, Preheating:

[0018] The powder obtained in step 2 is placed in a bell furnace and pre-fired in an air atmosphere at a temperature of 800-1000℃ for 2-4 hours. After pre-fired, the powder is sieved to obtain pre-fired powder.

[0019] Step 4, Doping:

[0020] Using the mass of the pre-fired material obtained in step 3 as a benchmark, add auxiliary components equivalent to the mass of the pre-fired material: "0.01-0.03wt% V2O5, 0.01-0.03wt% ZrO2, 0.1-0.4wt% Co2O3, 0.03wt% CaSiO3" to the pre-fired material to obtain mixed powder.

[0021] Step 5, Secondary ball milling:

[0022] The mixed powder obtained in step 4 is placed in a planetary ball mill, steel balls and deionized water are added, and the mixture is milled for 3 to 5 hours. After milling, it is dried to obtain secondary milled material.

[0023] Step 6, Granulation:

[0024] The secondary ball milling material obtained in step 5 is granulated and dried to obtain granulated material with good flowability.

[0025] Step 7, hydroforming:

[0026] The granulated material obtained in step 6 is placed in a mold and extruded in a hydraulic press to obtain a green part. The mold is a Ф14×8mm ring mold.

[0027] Step 8, Sintering:

[0028] The green blank obtained in step 7 is sintered in segments to obtain the manganese-zinc power ferrite; wherein, the segmented sintering process is as follows:

[0029] First stage: After placing the green blank in the air, the temperature is raised to 500-600℃ at a heating rate of 1-2℃ / min.

[0030] Second stage: The temperature is raised to 1100-1200℃ in air at a heating rate of 2-3℃ / min;

[0031] The third stage: hold at a sintering temperature of 1100-1200℃ for 6 hours, and adjust the oxygen partial pressure to 1-3% during the holding stage;

[0032] The fourth stage is the cooling stage. The cooling process adopts the equilibrium oxygen partial pressure method to reduce the temperature from 1100-1200℃ to 500℃, while the oxygen partial pressure is reduced from 1-3% to 0%. Then, under a pure nitrogen atmosphere, the temperature is naturally cooled from 500℃ to room temperature.

[0033] The sample obtained in step 8 was tested using testing equipment to determine its Bs and high-frequency loss temperature characteristics, thus producing a high-Bs, low-loss MnZn power ferrite product at MHz frequency.

[0034] Furthermore, in step 2, the rotation speed of the ball mill is 230-250 r / min.

[0035] Furthermore, in step 5, the rotation speed of the secondary ball mill is 230–250 r / min;

[0036] Furthermore, during granulation in step 6, 10–14 wt% PVA is added to the secondary ball milling material by weight.

[0037] Furthermore, in step 7, the pressure of hydraulic forming is 110-120 MPa.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] In the preparation process of MnZn ferrite, CaCO3 and SiO2 are usually added. This is because Ca... 2+ With Si 4+ With a relatively large ionic radius, SiO2 mainly accumulates at grain boundaries in ferrites, hindering grain growth and thus controlling the microstructure. Simultaneously, SiO2 exhibits high resistivity (10⁻⁶ Ω·cm). 16 SiO2 (Ω·m) helps increase grain boundary resistance and reduce eddy current losses at high frequencies. However, studies have shown that the amount of SiO2 added should not be too high, usually not exceeding 60 ppm. This is because excessive SiO2 can generate low-melting-point FeSiO3 (melting point 1150℃), which promotes grain growth and produces abnormal grains. On the other hand, excessive SiO2 can also cause grains to aggregate at grain boundaries, resulting in discontinuous grain growth and abnormal grains. This phenomenon can be observed through SEM images of natural cross-sections, which to some extent limits the control effect of Si on resistivity.

[0040] This invention provides a high-Bs, low-loss MHz manganese-zinc power ferrite by introducing an appropriate amount of CaSiO3 auxiliary component. This method introduces silicon, and abnormal grain growth only occurs when the CaSiO3 addition reaches 0.05 wt%. Converted to introducing Si ions via SiO2 addition, this requires 0.0258 wt% SiO2, far exceeding the existing 60 ppm. Therefore, this invention effectively suppresses the negative effects of excessive SiO2 addition. Simultaneously, utilizing the high melting point of CaSiO3 (2130℃), it inhibits grain growth during sintering, making it easier for pores in the ferrite to migrate from the grain interior to the grain boundaries and escape outwards through the grain boundaries, reducing porosity and increasing sintering density. Furthermore, CaSiO3 enriches at the grain boundaries, forming a high-resistivity layer, increasing the material's grain boundary resistance and reducing high-frequency losses. Attached Figure Description

[0041] Figure 1 Here is a SEM image of the natural cross-section of MnZn ferrite in Example 1;

[0042] Figure 2 Here is a SEM image of the natural cross-section of MnZn ferrite in Example 2;

[0043] Figure 3 Here is a SEM image of the natural cross-section of MnZn ferrite in Example 3;

[0044] Figure 4 The total loss Pcv (kW / m) of the MnZn ferrite materials prepared in Example 2 and Comparative Example 3 is given by [reference to example 2]. 3 Temperature characteristic curves of 2MHz 50mT;

[0045] Figure 5 The total loss Pcv (kW / m) of the MnZn ferrite materials prepared in Example 2 and Comparative Example 3 is given by [reference to example 2]. 3 Temperature characteristic curves of 3MHz and 30mT;

[0046] Figure 6 Temperature characteristic curves of grain boundary resistance of MnZn ferrite materials prepared in Example 2 and Comparative Example 3. Detailed Implementation

[0047] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0048] This invention provides a high-Bs, low-loss megahertz manganese-zinc power ferrite and its preparation method. The samples of Examples 1-3 and Comparative Examples 1-3 are prepared through the following steps:

[0049] Step 1, Ingredients:

[0050] Using Fe2O3, ZnO, and MnO as raw materials, the raw materials were calculated and weighed according to the main components of "54.5 mol% Fe2O3, 4.5 mol% ZnO, and 41.0 mol% MnO".

[0051] Step 2, First ball milling:

[0052] Place the raw material weighed in step 1 into a planetary ball mill and perform ball milling once. The ball milling time is 2.5 hours, and the ball milling media is Ф5mm bearing steel. After ball milling, dry the material and pass it through a 60-mesh sieve to obtain the first-ground powder.

[0053] Step 3, Preheating:

[0054] The powder obtained in step 2 was placed in a bell furnace and pre-fired in an air atmosphere at a temperature of 920°C for 4 hours. After pre-fired, the powder was passed through a 40-mesh sieve to obtain pre-fired powder.

[0055] Step 4, Doping:

[0056] Using the mass of the pre-fired material obtained in step 3 as a benchmark, the auxiliary components shown in Table 1 are added to the pre-fired material to obtain a mixed powder.

[0057] Table 1. Proportion of auxiliary components

[0058]

[0059] Step 5, Secondary ball milling:

[0060] The mixed powder obtained in step 4 was placed in a planetary ball mill, deionized water was added, and the milling was carried out for 5 hours. The milling media was Ф5mm bearing steel. After the milling was completed, the powder was dried and passed through a 40-mesh sieve to obtain secondary milling material.

[0061] Step 6, Granulation:

[0062] 14 wt% PVA was added to the secondary ball milling material by weight for granulation and drying to obtain granules with good flowability.

[0063] Step 7, hydroforming:

[0064] The granulated material obtained in step 6 is placed in a mold and extruded in a hydraulic press to obtain a green part. The mold is a Ф14×8mm ring mold and the extrusion pressure is 120MPa.

[0065] Step 8, Sintering:

[0066] The green blank obtained in step 7 is sintered in segments to obtain the manganese-zinc power ferrite; wherein, the segmented sintering process is as follows:

[0067] First stage: After placing the green blank in the air, the temperature is raised to 600℃ at a heating rate of 1.5℃ / min.

[0068] Second stage: The temperature is increased to 1150℃ in air at a heating rate of 2.5℃ / min;

[0069] The third stage: hold at a sintering temperature of 1150℃ for 6 hours, and adjust the oxygen partial pressure to 1.9% during the holding stage;

[0070] The fourth stage is the cooling stage. The cooling process uses the equilibrium oxygen partial pressure method to reduce the temperature from 1150℃ to 500℃, while the oxygen partial pressure is reduced from 1.9% to 0%. Then, under a pure nitrogen atmosphere, the temperature is naturally cooled from 500℃ to room temperature.

[0071] The initial permeability μi of the samples was measured using a Tonghui TH2826 LCR digital bridge; the saturation magnetic induction Bs and volumetric power loss Pcv of the samples were measured using an Iwasaki SY-8218BH analyzer; and the sintering density ρ of the samples was measured using the water displacement method. The test results of Examples 1-3 and Comparative Examples 1-3 are shown in Tables 2 and 3:

[0072] Table 2 Test results of Examples 1-3 and Comparative Examples 1-3

[0073]

[0074] Table 3 Sintering density of Examples 1-3 and Comparative Examples 1-3

[0075]

[0076] Tests have shown that the appropriate addition of CaSiO3 can effectively improve the sintering density. This is because the high melting point (2130℃) of CaSiO3 inhibits grain growth during sintering, making it easier for pores in the ferrite to move from the inside of the grain to the grain boundary and escape outward through the grain boundary, thereby reducing the porosity, increasing the sintering density, and thus improving Bs.

[0077] Figure 1 Here is a SEM image of the natural cross-section of MnZn ferrite from Example 1; Figure 1 It can be seen that the sample obtained by adding 0.01wt% CaSiO3 in Example 1 has a grain size between 6.0 and 11 μm and is not uniform. Figure 2 Here is a SEM image of the natural cross-section of MnZn ferrite from Example 2; Figure 2 It can be seen that the sample obtained by adding 0.03wt% CaSiO3 in Example 2 has a grain size between 4 and 7 μm, and the grains are more refined and uniform. Figure 3 Here is a SEM image of the natural cross-section of MnZn ferrite in Example 3; from Figure 3It can be seen that the sample obtained by adding 0.05wt% CaSiO3 in Example 3 showed abnormal grain growth, with large, continuous, and uneven grains. Figures 1-3 This indicates that appropriate CaSiO3 doping can improve the microstructure of MnZn power ferrite, refine the grains, and increase grain uniformity.

[0078] Figure 5 The total loss Pcv (kW / m) of the MnZn ferrite materials prepared in Example 2 and Comparative Example 3 is given by [reference to example 2]. 3 Temperature characteristic curves of 3MHz and 30mT; from Figure 5 It can be seen that the sample obtained by adding 0.03wt% CaSiO3 in Example 2 can effectively reduce the loss of MnZn ferrite material at high frequencies.

Claims

1. A high-Bs, low-loss megahertz manganese-zinc power ferrite, characterized in that, It includes main components and auxiliary components; wherein, the main components, based on the molar percentage of oxides, include: 54.50 mol% Fe2O3, 4.5 mol% ZnO, and 41.0 mol% MnO; based on the mass of the pre-calcined material after pre-calcination of the main components, the auxiliary components include: 0.02 wt% V2O5, 0.025 wt% ZrO2, 0.3 wt% Co2O3, and 0.03 wt% CaSiO3; The pre-calcined material is prepared by the following process: Fe2O3, ZnO and MnO are used as raw materials, and the raw materials are calculated and weighed according to the ratio of 54.50 mol% Fe2O3, 4.5 mol% ZnO and 41.0 mol% MnO; the weighed raw materials are ball-milled once for 2 to 3 hours; after ball milling, they are dried and sieved to obtain a first-milled powder; the first-milled powder is pre-calcined in air at a temperature of 800 to 1000℃ for 2 to 4 hours; after pre-calcination, it is sieved to obtain the pre-calcined material.

2. A method for preparing a high-Bs, low-loss megahertz manganese-zinc power ferrite, characterized in that, Includes the following steps: Step 1, Ingredients: Using Fe2O3, ZnO and MnO as raw materials, the raw materials were calculated and weighed according to the ratio of 54.50 mol% Fe2O3, 4.5 mol% ZnO and 41.0 mol% MnO; Step 2, First ball milling: The raw materials weighed in step 1 are ball-milled once for 2 to 3 hours. After ball milling, they are dried and sieved to obtain the first-milled powder. Step 3, Preheating: The powder obtained in step 2 is pre-calcined in air at a temperature of 800-1000℃ for 2-4 hours. After pre-calcination, it is sieved to obtain the pre-calcined material. Step 4, Doping: Using the mass of the pre-fired material obtained in step 3 as a benchmark, 0.02wt%V2O5, 0.025wt%ZrO2, 0.3wt%Co2O3, and 0.03wt%CaSiO3 are added to the pre-fired material as auxiliary components to obtain a mixed powder. Step 5, Secondary ball milling: The mixed powder obtained in step 4 is subjected to a second ball milling for 3 to 5 hours. After the ball milling is completed, it is dried to obtain the second ball milled material. Step 6, Granulation: The secondary ball milling material obtained in step 5 is granulated and dried to obtain granulated material. Step 7, hydroforming: The granulated material obtained in step 6 is extruded and molded in a hydraulic press to obtain a green part; Step 8, Sintering: The green blank obtained in step 7 is sintered in segments to obtain the manganese-zinc power ferrite; wherein, the segmented sintering process is as follows: First stage: After placing the green blank in the air, raise the temperature to 500~600℃; Second stage: Continue to raise the temperature to 1100~1200℃; Third stage: Keep warm at 1100~1200℃ for 6 hours, and adjust the oxygen partial pressure to 1~3%; Fourth stage: The temperature is reduced from 1100~1200℃ to 500℃, and the oxygen partial pressure is reduced from 1~3% to 0%; then, under a pure nitrogen atmosphere, the temperature is naturally cooled from 500℃ to room temperature.

3. The method for preparing high-Bs, low-loss MHz manganese-zinc power ferrite according to claim 2, characterized in that, In step 2, the rotation speed of the ball mill is 230~250 r / min.

4. The method for preparing high-Bs, low-loss MHz manganese-zinc power ferrite according to claim 2, characterized in that, In step 5, the rotation speed of the secondary ball mill is 230~250 r / min.

5. The method for preparing high-Bs, low-loss MHz manganese-zinc power ferrite according to claim 2, characterized in that, In step 6, during granulation, 10-14 wt% PVA is added to the secondary ball milling material at a weight ratio.

6. The method for preparing high-Bs, low-loss MHz manganese-zinc power ferrite according to claim 2, characterized in that, In step 7, the pressure of hydraulic forming is 110~120MPa.

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