A high T c High B s High-conductivity manganese-zinc ferrite and its preparation method

Abstract

A high T c High B s High manganese zinc ferrite and preparation method, belong to ferrite material preparation technical field. The present application adopts brand-new rich iron little zinc main formula design, through the regulation and control spinel sublattice inter super exchange, in satisfying high Curie temperature, make up the defect of starting magnetic permeability drop; Introduce a variety of additives to play the comprehensive effect, through Ti 4+ Regulate the magnetic crystal anisotropy constant, improve the magnetic permeability, promote the growth of large grain through low melting point fluxing additive, it is favorable to the formation of high magnetic permeability material, increase the density of sintered body at the same time, so as to improve the saturation magnetic induction intensity;Provide a new sintering thought in the holding stage, optimize the sintering oxygen partial pressure curve in the whole process, under the condition of little change in production cost, the comprehensive performance of the material is improved to a higher level. The present application has obtained the MnZn ferrite with high Curie temperature, high magnetic permeability and high saturation magnetization.

Description

Technical Field

[0001] This invention belongs to the field of ferrite material preparation technology, specifically relating to a MnZn ferrite material with high Curie temperature, high saturation magnetic induction intensity, and high magnetic permeability, and its preparation method. Background Technology

[0002] With the rapid development of the electronics and information industry, soft magnetic ferrite materials have been widely used and are increasingly becoming a fundamental material for national economic development. Soft magnetic ferrite materials possess unique advantages in initial permeability and saturation magnetic induction, which makes it possible for electronic components to develop towards higher power energy conversion and data transmission. At the same time, compared to metals, their resistivity is higher, which is beneficial for reducing eddy current losses at high frequencies and broadening applications in higher frequency bands. Soft magnetic ferrites are mainly classified by composition into MnZn ferrite and NiZn ferrite, with MnZn ferrite occupying the majority of the market. High permeability MnZn ferrite typically refers to MnZn ferrite with an initial permeability greater than or equal to 5000. Due to its high initial permeability, high saturation magnetic induction, and high Curie temperature, it is widely used in various electronic components and equipment.

[0003] Currently, with the rapid development of information technology and digital communication, magnetic devices used in data transmission conversion scenarios (such as transformers, filters, and EMI suppression components) are being driven towards miniaturization and integration. This places higher demands on the MnZn ferrite materials used in these applications. The high permeability of the material allows inductors to achieve higher inductance with fewer coil turns, which is beneficial for device miniaturization and reducing copper losses. A high Curie temperature can broaden the upper limit of the device's operating temperature, enriching its application scenarios. A high saturation magnetic flux density can improve saturation resistance, which is beneficial for magnetic stability at high power levels, while also increasing power density, which is conducive to device miniaturization and integration. Therefore, developing a MnZn ferrite material that simultaneously possesses high Curie temperature, high saturation magnetic flux density, and high permeability is of significant importance.

[0004] For high-permeability MnZn ferrite materials, many companies both domestically and internationally have developed various models. For example, TDK Corporation of Japan was the first to develop practical high-permeability MnZn ferrite materials, while Siemens of Germany produces the T38 material, which has an initial permeability of 10,000 and a low temperature coefficient. Domestic companies, represented by Hengdian Dongci and Tiantong, have also developed high-permeability materials such as R10K, R12K, TSR7, and TSR10, representing a relatively high level of development in the industry.

[0005] In summary, MnZn ferrite materials with a permeability of around 10,000 have received widespread attention and have a broad market. However, currently, mainstream MnZn ferrite products meeting the requirement of a permeability of around 10,000 only have a Curie temperature of 150℃~160℃, and their saturation magnetic induction intensity B... s The current level is also relatively low, which can no longer meet the increasingly demanding application requirements of automotive power modules and new energy photovoltaic modules. Therefore, it is necessary to develop a module with a Curie temperature of 190℃ and a saturation magnetic induction intensity B at 25℃. s A new generation of high-permeability MnZn ferrites with a strength of ≥510mT is urgently needed.

[0006] Regarding MnZn ferrites with high Curie temperature, high saturation magnetic induction, and high permeability, Chinese Patent Publication No. CN111039668 A discloses "Wide-Temperature High Initial Permeability High Curie Temperature Manganese-Zn Ferrite and its Preparation Method." The main components include 55.5–58 mol% Fe₂O₃, 18.0–23.5 mol% ZnO, and the remainder being MnO. Additive components include at least two of the following: CoO: 30 ppm–100 ppm, NiO: 50 ppm–200 ppm, CuO: 100 ppm–300 ppm, SiO₂: 200 ppm–1000 ppm, Bi₂O₃: 50 ppm–500 ppm, and MgO: 0–300 ppm. By utilizing a zinc-rich formulation and a composite doping system design, along with adjustments to a special mixing and sintering process, the prepared manganese-zinc ferrite exhibits ultra-high initial permeability (μ). i ≥11000, 25℃), higher Curie temperature (T c With a Curie temperature of 138℃ and a relatively wide operating temperature range (0±2~110±2℃), it exhibits excellent overall performance and can meet the requirements of miniaturization in electronic components. However, its Curie temperature is still relatively low, resulting in a narrow operating temperature range, which urgently needs improvement.

[0007] For example, Chinese Patent Publication No. CN 104529425 A discloses a wide-temperature, high-permeability MnZn ferrite material and its manufacturing method. The main components include 51.0–53.5 mol% Fe₂O₃, 18.0%–18.8 mol% ZnO, and the remainder is MnO. The auxiliary components are a combination of three compounds, A, B, and C, wherein: A is at least one of TiO₂ and Co₂O₃, B is at least one of Nb₂O₅, SiO₂, and CaCO₃, and C is at least one of Bi₂O₃ and MoO₃. The patent also provides a corresponding preparation method. The wide-temperature, high-permeability MnZn ferrite material provided by this invention exhibits an initial permeability greater than 4500 and less than 6000 over a wide temperature range of -60℃ to 100℃, and also possesses a high Curie temperature (T). c≥160℃) and high saturation magnetic induction intensity (B s (≥460mT, 25℃), however, its initial permeability is still relatively low, and its saturation magnetic induction is also slightly insufficient, which affects its overall performance.

[0008] For example, Chinese Patent Publication No. CN 115650719 A discloses "A High-T c "High-Permeability Manganese-Zinc Ferrite Materials and Their Preparation Methods", which describes high-T c High-permeability manganese-zinc ferrite material is composed of FeFe2O4, MnFe2O4, ZnFe2O4, and Li. 0.5 This patent also provides a method for preparing high-T composite ferrite materials formed by solid solution treatment of four single ferrites, Fe2O4. c Technical route for high permeability manganese-zinc ferrite materials, and high T obtained based on the above technology c The high permeability MnZn ferrite material was tested and found to have a permeability of around 10,000. The temperature T was calculated using the empirical formula for Curie temperature. c At only 160℃, and at 100℃, the saturation magnetic induction intensity B s With a temperature of approximately 320 mT, this type of material exhibits superior overall performance, but there is still room for improvement in its Curie temperature and saturation magnetic induction intensity.

[0009] For example, Chinese Patent Publication No. CN 110683841 A discloses "A High Magnetic Permeability High B..." s The invention relates to a manganese-zinc ferrite material and its preparation method. The main components include 70.0–71.0 mol% Fe₂O₃, 14.0%–16.0 mol% ZnO, with the remainder being MnO. The doping components include MoO₃, Bi₂O₃, V₂O₅, Co₂O₃, and TiO₂, accounting for 0.08–0.15% of the total mass. The resulting MnZn ferrite exhibits an initial permeability of 10,000–13,000 at 25 °C and a Curie temperature T0. c Saturation magnetic induction intensity B at ≥150℃, 25℃, and 1200A / m s Saturation magnetic induction intensity B at ≥470mT, 100℃, and 1200A / m s ≥320mT. Its overall performance is relatively comprehensive, but the saturation magnetic induction intensity and Curie temperature need to be improved.

[0010] In summary, based on the products of typical domestic and international magnetic material companies and publicly available patented technologies, obtaining MnZn ferrite materials with high magnetic permeability is relatively easy. However, currently, no product can simultaneously achieve a high initial magnetic permeability μ. i =10000±10% (25℃, f=10KHz, B<0.25mT), Curie temperature T c≥190℃, saturation magnetic induction intensity B s ≥510mT (25℃, 1KHz, 1194A / m), and under 100℃ conditions, B s ≥350mT. Therefore, to improve the upper limit of the application temperature range and saturation characteristics of high-permeability MnZn ferrite, to solve the shortcomings of poor electromagnetic properties in some mainstream products, and to enrich application scenarios, developing a new generation of MnZn ferrite material with a Curie temperature above 190℃ while maintaining high initial permeability and saturation magnetic induction has bright application prospects and practical significance. Summary of the Invention

[0011] The purpose of this invention is to address the challenge of low Curie temperature and saturation magnetic flux density in existing high-permeability MnZn soft magnetic ferrite materials used in electronic systems such as new energy vehicles and photovoltaics. Focusing on improving the overall performance of the material and overcoming the shortcomings of current technology, this invention provides a MnZn ferrite material with high Curie temperature, high saturation magnetic flux density, and high permeability, as well as its preparation method. The initial permeability μ of the MnZn ferrite material of this invention... i =10000±10% (25℃, 10KHz, B<0.25mT), Curie temperature T c ≥190℃, saturation magnetic induction intensity B s ≥510mT (25℃, 1KHz, H=1194A / m), and under 100℃ conditions, B s ≥350mT. Compared with existing similar products, the MnZn ferrite material provided by this invention has more comprehensive and superior overall performance, filling a research gap.

[0012] The core idea of ​​this invention is based on theoretical research in magnetic physics on high-permeability MnZn ferrites, showing a strong correlation between the initial permeability and Curie temperature of the material and the main formulation of MnZn ferrites. Generally, to improve the initial permeability of MnZn ferrites, a higher ZnO content in the main formulation is required; therefore, most high-permeability MnZn ferrites currently employ a zinc-rich main formulation. However, an increased ZnO content weakens the superexchange interaction in the spinel lattice, leading to a significant decrease in the Curie temperature, which contradicts the original intent of this invention. To meet the urgent demand for high-Curie-temperature ferrites in the modern electronics industry, it is essential to abandon the existing multi-zinc main formulation system and establish a completely new MnZn ferrite main formulation that satisfies the requirement of high Curie temperature. This invention employs an iron-rich, low-zinc formulation to increase the Curie temperature of the material. Simultaneously, an appropriate increase in iron content enhances the superexchange interaction at the AB sites of the spinel lattice, increasing the magnetization M... s This improves the saturation magnetic induction and initial permeability, compensating for the decrease in permeability caused by the reduction in zinc content. Simultaneously, the main formulation of this invention regulates the non-magnetic ion Zn. 2+The concentration of the additive and its occupancy ratio in the spinel sublattice increases the total magnetic moment, which is beneficial to improving the overall magnetic properties. In addition, the improvement of the overall magnetic properties of the material also depends on the combined effect of the additive system and the sintering process.

[0013] Regarding additives, considering that the initial magnetic permeability of the material depends on a combination of factors such as the magnetocrystalline anisotropy constant, magnetostriction coefficient, and grain size and density of the sintered body, a multi-effect additive scheme is adopted. First, low-melting-point fluxing additives are considered, utilizing the combined effects of Bi₂O₃, MoO₃, and V₂O₅ to control the evolution of the material's microstructure during sintering, achieving a large and uniform grain distribution. Second, TiO₂ additives are introduced, and Ti… 4+ The ions possess a large magnetocrystalline anisotropy constant, which can compensate for the negative value of MnZn ferrite itself. Simultaneously, Ti and V elements readily undergo valence changes in a reducing sintering atmosphere, which can be used to regulate electron transfer, thereby comprehensively regulating Fe. 3+ and Fe 2+ Content, Fe 2+ It can also compensate for the magnetocrystalline anisotropy constant K1, bringing it close to zero. The absolute value of K1 is inversely proportional to the initial permeability, thus increasing the initial permeability. Simultaneously, K1 affects the permeability temperature compensation point, thereby influencing the temperature characteristic curve, which is crucial for describing wide-temperature characteristics. Furthermore, introducing CaCO3 doping to regulate grain growth, optimize grain distribution, improve microstructure, and appropriately increase the sintered body density contributes to the overall improvement of magnetic properties.

[0014] Regarding the sintering process, this invention proposes a novel sintering concept. Compared to the traditional sintering approach for high-permeability MnZn ferrite, after the conventional holding time in the sintering stage, the sintering temperature is increased by a certain amount, and the holding time is continued for a period of time. Simultaneously, the oxygen partial pressure is appropriately controlled during this process. The design of the holding stage and its corresponding temperature greatly influence the solid-state reaction process of the material during sintering, thus affecting grain growth. Excessive temperature and time can lead to abnormal grain growth and deterioration of the microstructure, while insufficient temperature and time can result in insufficient grain growth, which is detrimental to achieving high permeability. Based on the above, this invention increases the temperature and continues holding for a period of time after sintering. This ensures sufficient grain growth, which is beneficial for obtaining larger and more suitable grain sizes. At the same time, the appropriate extension of the holding time promotes uniform grain distribution during growth, optimizes the microstructure, improves grain boundary characteristics, and reduces magnetization resistance. The core of the reduction sintering technology lies in the oxygen partial pressure curves during the holding and cooling stages, which affect the balance of the redox reaction, thereby controlling the Fe... 2+It makes a positive contribution to the magnetocrystalline anisotropy constant and the magnetostriction coefficient. At the same time, a suitable sintering atmosphere is conducive to the discharge of pores inside the sintered body, reducing the porosity and achieving material densification. This increases the density of the sintered body, improves the microstructure, and thus enhances the overall magnetic properties of the material.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] A high T c High B s A high-conductivity manganese-zinc ferrite comprises a main formulation and additives. The main formulation comprises 52.0–54.0 mol% Fe₂O₃ and 16.0%–18.0 mol% ZnO, with the remainder being MnO. Based on the mass of the pre-calcined material obtained after pre-calcination, the additives comprise 0.02–0.04 wt% TiO₂, 0.01–0.02 wt% V₂O₅, 0.03–0.05 wt% Bi₂O₃, 0.02–0.04 wt% MoO₃, and 0.02–0.04 wt% CaCO₃.

[0017] A high T c High B s A method for preparing high-conductivity manganese-zinc ferrite includes the following steps:

[0018] Step 1, Ingredients:

[0019] Using Fe2O3, ZnO and MnO as raw materials, the raw materials were calculated and weighed according to the main formula of "52.0-54.0 mol% Fe2O3 and 16.0-18.0 mol% ZnO, with the remainder being MnO".

[0020] Step 2, First ball milling:

[0021] The raw material weighed in step 1 is ball-milled once in a planetary ball mill for 1 to 2 hours to obtain primary ball milled material.

[0022] Step 3, Preheating:

[0023] After drying and sieving, the primary ball milling material obtained in step 2 is placed in a bell furnace and pre-fired in air atmosphere for 3-5 hours.

[0024] Step 4, Doping:

[0025] Using the mass of the pre-burned material obtained in step 3 as a benchmark, add "0.02-0.04 wt% TiO2, 0.01-0.02 wt% V2O5, 0.03-0.05 wt% Bi2O3, 0.02-0.04 wt% MoO3 and 0.02-0.04 wt% CaCO3" as additives to the pre-burned material;

[0026] Step 5: Secondary ball milling;

[0027] The mixed powder obtained in step 4 is loaded into a planetary ball mill for secondary ball milling for 2-4 hours, and the particle size is controlled and then dried.

[0028] Step 6, Granulation and Molding:

[0029] 10-15 wt% PVA binder is added to the secondary ball milling material obtained in step 5 by weight ratio, mixed and granulated, and then pressed on a press to obtain a green part of the target shape.

[0030] Step 7, Sintering:

[0031] The green blank obtained in step 6 is placed in a tube furnace for staged high-temperature sintering to obtain the manganese-zinc ferrite; wherein, the staged high-temperature sintering process is as follows:

[0032] The first stage: heating from 50℃ to 500-600℃, with an oxygen partial pressure of 21% and a heating rate of 1-2℃ / min. This stage is the stage for enhancing the debinding process.

[0033] Second stage: Continue heating to 700-800℃, oxygen partial pressure is 21%, heating rate is 1.5-2.5℃ / min, this stage is the standard debinding stage;

[0034] The third stage: continue heating to the sintering temperature of 1300-1450℃, with an oxygen partial pressure of 21% and a heating rate of 1.5-2.5℃ / min. This stage is the sintering stage.

[0035] Fourth stage: Maintain the sintering temperature at 1300-1450℃ for 5-6 hours, and keep the oxygen partial pressure at 21%; then raise the temperature by 20-40℃ (20-40℃ higher than the sintering temperature) at a rate of 1-2℃ / min, reduce the oxygen partial pressure to 10%, and keep the temperature for 2-3 hours. This stage is the holding stage.

[0036] Fifth stage: Cooling down to 1300℃, the oxygen partial pressure gradually decreases to 3.5%; then continue cooling down to 1100-1300℃, the oxygen partial pressure gradually decreases to 0.5%; continue cooling down to 950-1100℃, the oxygen partial pressure gradually decreases to 0.08%; continue cooling down to 900℃, the oxygen partial pressure is pure nitrogen atmosphere, and then cooling down to 50℃ in pure nitrogen atmosphere; the cooling rate is 1.5-2.5℃ / min, this stage is the cooling stage.

[0037] Furthermore, in step 2, the ball milling speed is 220-250 r / min; in step 3, the pre-firing temperature is 800-900℃, and the pre-firing time is 3-5 hours; in step 5, the ball milling speed is 240-280 r / min.

[0038] This invention provides a high Tc High B s This invention presents a high-conductivity manganese-zinc ferrite, employing a novel iron-rich, low-zinc main formulation design. By controlling the superexchange interaction between spinel sublattices, it compensates for the decrease in initial permeability while maintaining a high Curie temperature. Regarding the additive system, this invention introduces multiple additives to achieve a synergistic effect, utilizing Ti... 4+ By controlling the magnetocrystalline anisotropy constant and increasing the magnetic permeability, and by promoting the growth of large grains through low-melting-point fluxing agents, the formation of high-permeability materials is facilitated. Simultaneously, the density of the sintered body is increased, thereby enhancing the saturation magnetic induction intensity. Regarding the sintering process, this invention provides a novel approach to sintering during the holding stage, while optimizing the oxygen partial pressure curve throughout the entire sintering process. This significantly improves the overall performance of the material without substantial changes in production costs, making it of great practical significance.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. The high T of the present invention c High B s High-conductivity manganese-zinc ferrite is a type of material that meets the requirements of a high Curie temperature (T). c MnZn ferrite (≥190℃) possesses both high permeability and high saturation magnetization. Electronic components made from this material can adapt to a wider range of operating environments, greatly improving the reliability and compatibility of electronic systems.

[0041] 2. The high T of the present invention c High B s High-conductivity manganese-zinc ferrite, its Curie temperature T c ≥190℃, initial permeability μ i =10000±10% (25℃, 10kHz, B<0.25mT), saturation magnetic induction intensity B s ≥510mT (25℃, f=1kHz, H=1194A / m), and under 100℃ conditions, B s ≥350mT. It can meet the requirements of electronic devices for high permeability and high saturation characteristics in a wider range of applications, which is conducive to the diversified development of devices and the improvement of comprehensive performance. Compared with existing products, it has superior main electromagnetic characteristics.

[0042] 3. The new sintering concept proposed in this invention overcomes the shortcomings of the original process to a certain extent and provides a more advanced approach for the subsequent iterative development of materials. Attached Figure Description

[0043] Figure 1 SEM microstructure images of MnZn ferrites prepared in Examples 1-3; where (a) corresponds to Example 1, (b) corresponds to Example 2, and (c) corresponds to Example 3;

[0044] Figure 2 The initial permeability temperature characteristic curves of MnZn ferrites prepared in Examples 1, 4 and Comparative Example 1 are shown.

[0045] Figure 3 The complex permeability frequency response curve of the MnZn ferrite prepared in Example 1;

[0046] Figure 4 The curve of saturation magnetic induction intensity of the MnZn ferrite prepared in Example 1 as a function of temperature. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solution of the present invention, a more detailed description will be provided through specific implementations, but the scope of protection of the present invention is not limited to these embodiments.

[0048] Unless otherwise specified, the experimental or testing methods described in the following embodiments are conventional methods, and the materials and reagents described are obtained from conventional commercial channels.

[0049] This invention provides a high T c High B s High-conductivity manganese-zinc ferrite and its preparation method: Samples of Examples 1-4 and Comparative Example 1 were prepared by the following steps:

[0050] Step 1, Ingredients:

[0051] Using Fe2O3, ZnO and MnO as raw materials, the main raw materials for Examples 1 to 4 and Comparative Example 1 were weighed according to the formulations in the table below.

[0052]

[0053]

[0054] Step 2, First ball milling:

[0055] The raw material weighed in step 1 is ball-milled once in a planetary ball mill. The ball milling media is bearing steel balls, and the ball milling time is 1.5 hours to obtain primary ball milling material.

[0056] Step 3, Preheating:

[0057] The ball milling material obtained in step 2 was dried, sieved, and placed in a bell furnace. It was pre-calcined at 850°C in air atmosphere for 4 hours to obtain pre-calcined material.

[0058] Step 4, Doping:

[0059] Using the mass of the pre-sintered material obtained in step 3 as a benchmark, additives were added to the pre-sintered material, and the doping amounts are shown in the table below:

[0060]

[0061] Step 5: Secondary ball milling;

[0062] The mixed powder obtained in step 4 was loaded into a planetary ball mill for secondary ball milling for 2 hours, and the particle size was controlled and then dried.

[0063] Step 6, Granulation and Molding:

[0064] 10 wt% PVA binder was added to the secondary ball milling material obtained in step 5 by weight ratio, mixed and granulated, and then pressed on a press to obtain a green part of the target shape.

[0065] Step 7, Sintering:

[0066] The green blank obtained in step 6 is placed in a tube furnace for staged high-temperature sintering to obtain the manganese-zinc ferrite; wherein, the staged high-temperature sintering process is as follows:

[0067] The first stage: heating from 50℃ to 500-600℃, with an oxygen partial pressure of 21% and a heating rate of 1-2℃ / min. This stage is the stage for enhancing the debinding process.

[0068] Second stage: Continue heating to 800℃, oxygen partial pressure is 21%, heating rate is 1.5~2.5℃ / min, this stage is the standard debinding stage;

[0069] The third stage: continue heating to the sintering temperature of 1400℃, with an oxygen partial pressure of 21% and a heating rate of 1.5~2.5℃ / min. This stage is the sintering stage.

[0070] Fourth stage: Keep the sintering temperature constant at 1400℃ for 5-6 hours, and maintain the oxygen partial pressure at 21%; then raise the temperature by 20-40℃ (20-40℃ higher than the sintering temperature) at a rate of 1-2℃ / min, reduce the oxygen partial pressure to 10%, and hold for 2 hours. This stage is the holding stage.

[0071] Fifth stage: Cooling down to 1300℃, the oxygen partial pressure gradually decreases to 3.5%; then continue cooling down to 1100-1300℃, the oxygen partial pressure gradually decreases to 0.5%; continue cooling down to 950-1100℃, the oxygen partial pressure gradually decreases to 0.08%; continue cooling down to 900℃, the oxygen partial pressure is pure nitrogen atmosphere, and then cooling down to 50℃ in pure nitrogen atmosphere; the cooling rate is 1.5-2.5℃ / min, this stage is the cooling stage.

[0072] The process of the fourth stage, namely the heat preservation stage, is shown in the table below:

[0073]

[0074] After winding the MnZn ferrite samples prepared in Examples 1-4 and Comparative Example 1, the inductance L of the samples was measured using a Tonghui TH2826 precision LCR meter. The voltage across the samples was adjusted appropriately to ensure that B < 0.25mT. The initial permeability μ of the samples was then calculated using a formula. i The test conditions were a frequency f = 10 kHz and a typical voltage of 10 mV. Using the permeability-temperature characteristic curve obtained from the temperature-controlled oven, the Curie temperature T was calculated. c The saturation magnetic induction intensity B of the sample was measured using an Iwasaki SY-8218B-H analyzer. s A high-low temperature oven was used to test the temperature characteristics. Test conditions: frequency f = 1 kHz, external field H = 1194 A / m.

[0075] The main technical specifications of the samples from Examples 1-4 and Comparative Example 1 are shown in the table below, where d and D represent the sintered body density and average grain size, respectively:

[0076]

[0077] Figure 1 The figures show the SEM microstructure of the MnZn ferrites prepared in Examples 1-3. As can be seen from the figures, the variation in the content of each raw material in the main formulation within a certain range does not cause a significant change in the microstructure of the MnZn ferrite.

[0078] Figure 2 The figures show the initial permeability temperature characteristics of MnZn ferrites prepared in Examples 1, 4 and Comparative Example 1. As can be seen from the figures, the improved sintering method can effectively improve the initial permeability, and the effect of increasing the holding temperature on improving the initial permeability is obvious.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. The scope of protection of the present invention should be determined by the scope defined in the claims. Any modifications, substitutions, etc., made by those skilled in the art within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A high-T c High B s The method for preparing high-conductivity manganese-zinc ferrite is characterized by, Includes the following steps: Step 1, Ingredients: Using Fe2O3, ZnO and MnO as raw materials, calculate and weigh the raw materials according to the main formula of "52.0~54.0 mol% Fe2O3 and 16.0%~18.0 mol% ZnO, with the remainder being MnO". Step 2, First ball milling: The raw material weighed in step 1 is ball-milled once for 1-2 hours to obtain primary ball-milled material. Step 3, Preheating: After drying and sieving the primary ball milling material obtained in step 2, it is pre-calcined in air for 3-5 hours. Step 4, Doping: Using the mass of the pre-fired material obtained in step 3 as a benchmark, add "0.02~0.04wt% TiO2, 0.01~0.02wt% V2O5, 0.03~0.05wt% Bi2O3, 0.02~0.04wt% MoO3 and 0.02~0.04wt% CaCO3" as additives to the pre-fired material; Step 5: Secondary ball milling; The mixed powder obtained in step 4 is subjected to a second ball milling for 2-4 hours. Step 6, Granulation and Molding: PVA binder is added to the secondary ball milling material obtained in step 5, and after mixing and granulation, it is pressed on a press to obtain a green part; Step 7, Sintering: The green blank obtained in step 6 is sintered at high temperature in stages, and then cooled to obtain the manganese-zinc ferrite; wherein, the staged high-temperature sintering process is as follows: First stage: Increase the temperature from 50℃ to 500~600℃, with an oxygen partial pressure of 21%; Second stage: Continue to raise the temperature to 700~800℃, with an oxygen partial pressure of 21%; Third stage: Continue to raise the temperature to the sintering temperature of 1300~1450℃, with an oxygen partial pressure of 21%; Fourth stage: Keep the sintering temperature constant at 1300~1450℃ for 5~6 hours, and maintain the oxygen partial pressure at 21%; then raise the temperature by 20~40℃, reduce the oxygen partial pressure to 10%, and hold for 2~3 hours.

2. The high-T according to claim 1 c High B s The method for preparing high-conductivity manganese-zinc ferrite is characterized by, In step 7, the cooling process is as follows: the temperature is lowered to 1300℃, and the oxygen partial pressure gradually decreases to 3.5%; then the temperature is further lowered to 1100~1300℃, and the oxygen partial pressure gradually decreases to 0.5%; the temperature is further lowered to 950~1100℃, and the oxygen partial pressure gradually decreases to 0.08%; the temperature is further lowered to 900℃, and the oxygen partial pressure is in a pure nitrogen atmosphere, and the temperature is lowered to 50℃ in a pure nitrogen atmosphere.

3. The high-T according to claim 1 c High B s The method for preparing high-conductivity manganese-zinc ferrite is characterized by, In step 2, the ball mill speed is 220~250 r / min.

4. The high-T according to claim 1 c High B s The method for preparing high-conductivity manganese-zinc ferrite is characterized by, In step 3, the preheating temperature is 800~900℃.

5. The high-T according to claim 1 c High B s The method for preparing high-conductivity manganese-zinc ferrite is characterized by, In step 5, the ball mill speed is 240~280 r / min.

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