Manganese zinc ferrite and method for producing the same

Abstract

The application discloses a manganese-zinc ferrite and a preparation method thereof, and the method comprises the following steps: mixing manganese-zinc ferrite powder and a polyvinyl alcohol solution to obtain a mixture, and grinding the mixture; performing a compression molding treatment on the ground mixture to obtain a compression molding product; and performing a sintering treatment on the compression molding product to obtain the manganese-zinc ferrite; wherein the sintering treatment comprises a temperature rising treatment stage, and the temperature rising treatment stage comprises a plurality of temperature rising stages, at least two of which have different temperature rising rates. The manganese-zinc ferrite prepared by the application can have a high saturation magnetic flux density and a low residual magnetism while keeping a low loss at a high frequency, that is, the manganese-zinc ferrite with a large magnetic induction intensity change amount is prepared.

Description

Technical Field

[0001] This application relates to the field of ferrite materials technology, and more specifically to a manganese-zinc ferrite and its preparation method. Background Technology

[0002] With the trend towards miniaturization of power supply products, the application of GaN (gallium nitride) devices and high-frequency switching technology has rapidly become widespread. However, the development of high-frequency, low-power soft magnetic materials has lagged far behind the technological demands of high-frequency power devices, which are being accelerated by the application of third-generation semiconductors such as GaN, becoming a bottleneck restricting the development of magnetic devices such as switching power supplies.

[0003] To ensure the magnetic core exhibits good DC superposition characteristics, it is necessary to increase the ΔB of the core material (ΔB = Bs - Br, where ΔB is the change in magnetic flux density, Bs is the saturation magnetic flux density, and Br is the remanent magnetization). A larger ΔB results in a more inclined hysteresis loop, allowing the core to withstand a larger DC bias field without rapidly saturating.

[0004] Therefore, there is a need for a manganese-zinc ferrite that can maintain low loss at high frequencies while having high saturation flux density and low remanence, i.e., a large ΔB. Summary of the Invention

[0005] This application is made to address at least one of the aforementioned problems. According to one aspect of this application, a method for preparing manganese-zinc ferrite is provided, the method comprising: mixing manganese-zinc ferrite powder with a polyvinyl alcohol solution to obtain a mixture, and grinding the mixture; pressing the ground mixture into a molded product to obtain a molded product; and sintering the molded product to obtain manganese-zinc ferrite; wherein the sintering process includes a heating stage, the heating stage comprising: a plurality of heating stages, at least two of the plurality of heating stages having different heating rates.

[0006] In one embodiment of this application, the concentration of the polyvinyl alcohol solution is 9.5% to 10.5%, the degree of alcoholysis of the polyvinyl alcohol is 87.0% to 89.0%, and the mixing ratio of the manganese zinc ferrite powder to the polyvinyl alcohol is (8.5 to 9.5):1.

[0007] In one embodiment of this application, the pressing pressure during the compression molding process is 4.5 to 5.5 MPa, and the holding time is 8 to 12 seconds.

[0008] In one embodiment of this application, the density of the compressed product is 2.7–3.1 g / cm³. 3 .

[0009] In one embodiment of this application, the sintering process further includes a heat preservation stage and a cooling stage, wherein the heat rise stage involves raising the temperature from the initial temperature to the heat preservation temperature of the heat preservation stage.

[0010] In one embodiment of this application, the heating stage including the initial temperature is the initial heating stage, and the heating stage including the holding temperature is the final heating stage; the heating rates of the plurality of heating stages are arranged in a pulsed stepwise manner, and the heating rate of the initial heating stage is greater than the heating rate of the final heating stage.

[0011] In one embodiment of this application, the temperature range of the initial heating stage is 25–200°C, and the heating rate of the initial heating stage is 9.5–10.5°C / min; the temperature range of the final heating stage is 900–1200°C, and the heating rate of the final heating stage is 3.5–4.5°C / min; between the initial heating stage and the final heating stage, the plurality of heating stages further include: a first intermediate heating stage, the temperature range of the first intermediate heating stage is 200–500°C, and the heating rate of the first intermediate heating stage is 3.5–4.5°C / min; and a second intermediate heating stage, the temperature range of the second intermediate heating stage is 500–900°C, and the heating rate of the second intermediate heating stage is 9.5–10.5°C / min.

[0012] In one embodiment of this application, the heat preservation temperature during the heat preservation treatment stage is 1180-1220°C, the heat preservation time is 6.5-7.5 hours, and the atmosphere during the heat preservation treatment stage is a nitrogen-oxygen mixed gas atmosphere.

[0013] In one embodiment of this application, the oxygen content in the nitrogen-oxygen mixture is 4.5% to 5.5% by volume.

[0014] In another aspect, this application provides a manganese-zinc ferrite, which is obtained by the method for preparing manganese-zinc ferrite described in any one of the above-mentioned methods.

[0015] According to an embodiment of this application, a manganese-zinc ferrite and its preparation method are described. The pressed product is sintered through multiple heating stages, with different heating rates in at least two stages. This allows moisture and polyvinyl alcohol in the pressed product to volatilize at a rate appropriate to the degree of sintering as the sintering temperature increases. The volatilized gas is also discharged at a rate appropriate to the degree of sintering. This ensures timely volatilization of moisture and polyvinyl alcohol, and timely discharge of gas from the pressed product, forming uniform pores and gaps in the manganese-zinc ferrite. Simultaneously, this results in a uniform and dense microstructure of the manganese-zinc ferrite, improving the uniformity of pores and gaps, increasing the sintering density, and making the grains in the manganese-zinc ferrite more uniform and refined. Consequently, the prepared manganese-zinc ferrite maintains low loss at high frequencies while also possessing high saturation magnetic flux density and low remanence, thus obtaining a manganese-zinc ferrite with a large change in magnetic induction intensity. Attached Figure Description

[0016] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0017] Figure 1 A flowchart illustrating a method for preparing manganese-zinc ferrite according to an embodiment of this application is shown.

[0018] Figure 2 The graph shows the relationship between the concentration of the polyvinyl alcohol solution and the core loss. Detailed Implementation

[0019] The following description provides numerous specific details to offer a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with this application.

[0020] To fully understand the present invention, a detailed description will be set forth in the following description. It should be understood that these embodiments are provided so that the disclosure of the present invention is thorough and complete, and that the concept of these exemplary embodiments is fully conveyed to those skilled in the art. Obviously, the implementation of embodiments of the present invention is not limited to the specific details familiar to those skilled in the art. Preferred embodiments of the present invention are described in detail below; however, in addition to these detailed descriptions, the present invention may have other embodiments.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated ingredients, conditions, features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other ingredients, conditions, features, integrals, steps, operations, elements, components, and / or combinations thereof.

[0022] With the trend towards miniaturization of power supply products, the application of GaN (gallium nitride) devices and high-frequency switching technology has rapidly become widespread. However, the development of high-frequency, low-power soft magnetic materials has lagged far behind the technological demands of high-frequency power devices, which are being accelerated by the application of third-generation semiconductors such as GaN, becoming a bottleneck restricting the development of magnetic devices such as switching power supplies.

[0023] To ensure the magnetic core exhibits good DC superposition characteristics, it is necessary to increase the ΔB of the core material (ΔB = Bs - Br, where ΔB is the change in magnetic flux density, Bs is the saturation magnetic flux density, and Br is the remanent magnetization). A larger ΔB results in a more inclined hysteresis loop, allowing the core to withstand a larger DC bias field without rapidly saturating.

[0024] Currently, some manganese-zinc ferrite materials can achieve a loss of 130 mW / cm² under conditions of 25℃, 50 mT, and 500 kHz. 3 However, its remanence reached 140mT, so its ΔB was only 330mT.

[0025] Therefore, there is a need for a manganese-zinc ferrite that can maintain low loss at high frequencies while having high saturation flux density and low remanence, i.e., a large change in magnetic induction intensity.

[0026] This application provides a method for preparing manganese-zinc ferrite, the method comprising: mixing manganese-zinc ferrite powder with a polyvinyl alcohol solution to obtain a mixture, and grinding the mixture; pressing the ground mixture into a molded product to obtain a molded product; and sintering the molded product to obtain manganese-zinc ferrite; wherein the sintering process includes a heating stage, the heating stage comprising multiple heating stages, at least two of the multiple heating stages having different heating rates.

[0027] It is understandable that moisture and polyvinyl alcohol in the pressed product can volatilize during the heating process, forming pores and gaps in the manganese-zinc ferrite. The formation of pores and gaps is related to the degree of sintering of the pressed product, the evaporation rate of moisture and polyvinyl alcohol, and the gas discharge rate. For example, if the evaporation rate of moisture and polyvinyl alcohol does not change as the degree of sintering of the pressed product increases, and / or the gas discharge rate does not change, the moisture and polyvinyl alcohol cannot volatilize in time, and / or the gas cannot be discharged in time, resulting in defects such as uneven pore size and density in the obtained manganese-zinc ferrite product. In this application, by adopting different heating rates in at least two heating stages, the evaporation rate of moisture and polyvinyl alcohol and / or the gas discharge rate can be adaptively adjusted to different sintering degrees of the pressed product, so that the evaporation rate of moisture and polyvinyl alcohol and / or the gas discharge rate are adapted to the sintering degree of the pressed product. Moisture and polyvinyl alcohol can evaporate in time, and gas can be discharged in time, thereby forming pores and gaps of uniform size and density in the manganese zinc ferrite product, making the microstructure of manganese zinc ferrite uniform and dense.

[0028] According to the method for preparing manganese-zinc ferrite of this application, the pressed product is sintered through multiple heating stages, and different heating rates are adopted in at least two heating stages. This allows the moisture and polyvinyl alcohol in the pressed product to volatilize at a rate adapted to the degree of sintering as the sintering temperature increases, and the gases generated by volatilization can be discharged at a rate adapted to the degree of sintering. In other words, the moisture and polyvinyl alcohol can volatilize in a timely manner, and the gases can be discharged from the pressed product in a timely manner, so as to form uniform pores and gaps in the manganese-zinc ferrite. At the same time, the microstructure of the manganese-zinc ferrite is made uniform and dense, which can improve the uniformity of pores and gaps in the manganese-zinc ferrite, increase the sintering density of the manganese-zinc ferrite, and make the grains in the manganese-zinc ferrite more uniform and refined. Thus, the prepared manganese-zinc ferrite can maintain low loss at high frequency while also having high saturation magnetic flux density and low remanence, that is, a manganese-zinc ferrite with a large change in magnetic induction intensity is prepared.

[0029] To fully understand this application, detailed steps will be presented in the following description to illustrate the technical solutions proposed in this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0030] In the examples, some of the reagents used were sourced from the following sources:

[0031] Reagents: Polyvinyl alcohol (PVA, type 1788, degree of alcoholysis: 87.0-89.0% (mol / mol)) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; manganese zinc ferrite powder (LP10 type) was purchased from Nanjing Xinkangda Magnetic Industry Co., Ltd.

[0032] Example 1

[0033] As attached Figure 1 The illustration shows a method 100 for preparing manganese-zinc ferrite according to an embodiment of this application. The method 100 for preparing manganese-zinc ferrite includes:

[0034] In step S110, manganese zinc ferrite powder is mixed with polyvinyl alcohol solution to obtain a mixture, and the mixture is then ground.

[0035] In step S120, the ground mixture is subjected to compression molding to obtain a compressed product;

[0036] In step S130, the pressed product is sintered to obtain manganese zinc ferrite.

[0037] The sintering process includes a heating stage, which comprises multiple heating stages, at least two of which have different heating rates.

[0038] The pressed product is sintered through multiple heating stages, with different heating rates in at least two stages. This allows the moisture and polyvinyl alcohol in the pressed product to volatilize at a rate appropriate to the degree of sintering as the sintering temperature increases. The volatilized gases are also promptly discharged from the pressed product, forming uniform pores and gaps in the manganese-zinc ferrite. This results in a uniform and dense microstructure of the manganese-zinc ferrite, improving the uniformity of pores and gaps, increasing the sintering density, and making the grains in the manganese-zinc ferrite more uniform and refined. Consequently, the prepared manganese-zinc ferrite maintains low loss at high frequencies while also possessing high saturation magnetic flux density and low remanence, thus producing a manganese-zinc ferrite with a large change in magnetic induction intensity.

[0039] In one embodiment of this application, the concentration of the polyvinyl alcohol solution is 9.5% to 10.5%, the degree of alcoholysis of polyvinyl alcohol is 87.0% to 89.0%, and the mixing ratio of manganese zinc ferrite powder to polyvinyl alcohol is (8.5 to 9.5):1.

[0040] Regarding the concentration of the polyvinyl alcohol (PVA) solution, during the preparation of the PVA solution, for normal viscosity PVA, the maximum concentration can reach 12%. Exceeding 12% results in excessively high viscosity and low water content, which is detrimental to solution preparation, ferrite granulation, and subsequent processing. Furthermore, increasing the concentration of the PVA solution can reduce the core loss of the prepared manganese-zinc ferrite. The relationship between the PVA solution concentration and core loss can be found in [reference needed]. Figure 2 Therefore, the concentration of the polyvinyl alcohol solution in this application is selected to be 9.5% to 10.5%, and preferably 10%.

[0041] Regarding the degree of alcoholysis of polyvinyl alcohol (PVA), as the degree of alcoholysis increases, its solubility in cold water decreases while its solubility in hot water increases. Taking PVA with a degree of alcoholysis of 87%–89% and 99% as examples, PVA with a degree of alcoholysis of 87%–89% exhibits the best water solubility, dissolving rapidly in both cold and hot water; PVA with a degree of alcoholysis of 99% and above is only soluble in hot water above 95°C. For PVA with excessively high degrees of alcoholysis, the required temperature for solution preparation is high, which is detrimental to production; therefore, PVA with a lower degree of alcoholysis is preferred.

[0042] For polyvinyl alcohol with a low degree of hydrolysis, such as polyvinyl alcohol with a degree of hydrolysis of 78%, the viscosity of the solution after dissolution is low, which is not conducive to reducing the loss of the magnetic core. Therefore, this application prefers polyvinyl alcohol with a degree of hydrolysis of 87.0% to 89.0%.

[0043] Polyvinyl alcohol is added as a binder to manganese-zinc ferrite powder, which can increase the bonding force between the manganese-zinc ferrite powders, thereby effectively improving the strength of the compressed product, avoiding cracking of the compressed product, and improving the formability of the compressed product.

[0044] Furthermore, by adding polyvinyl alcohol, the decomposition of polyvinyl alcohol during sintering produces more and smaller pores and gaps, resulting in a stronger demagnetizing field generated by the pores and gaps, which effectively reduces the remanence of the prepared manganese-zinc ferrite.

[0045] In one embodiment of this application, the preparation process of the polyvinyl alcohol solution is as follows: weigh an appropriate amount of polyvinyl alcohol and deionized water and add them to a beaker. Stir the mixture in a water bath at 90°C for 1 hour. After the polyvinyl alcohol dissolves, sieve the polyvinyl alcohol solution through a 100-mesh sieve to obtain a polyvinyl alcohol solution with a concentration of 9.5% to 10.5%.

[0046] In one embodiment of this application, after the manganese zinc ferrite powder is mixed with polyvinyl alcohol in step S110, it can be ground by grinding with a grinding rod and mortar, ball mill or other grinding methods, and there is no limitation on this.

[0047] In one embodiment of this application, the method 100 for preparing manganese-zinc ferrite after grinding the mixture further includes: screening the ground mixture using a sieve with an aperture range of 100 mesh to 200 mesh. Particles between 100 mesh and 200 mesh can be screened through the sieve, and the screened particles are the granulated powder.

[0048] In one embodiment of this application, in step S120, a certain amount of granulated powder is weighed and added to a mold, for example, with an outer diameter of 20 mm and an inner diameter of 12 mm. Then, a pressure device, such as a hydraulic powder tablet press, can be used to press and shape the granulated powder. During the pressing and shaping process, the pressure is gradually increased from the initial pressure to a set pressing pressure. After reaching the set pressing pressure, the pressure is held for a certain period of time to allow the powder to be pressed and shaped. The set pressing pressure is 4.5–5.5 MPa, and the holding time is 8–12 seconds. After pressing, a density of 2.7–3.1 g / cm³ is obtained. 3 The pressed product (also known as green body). A reasonable pressing density can increase the sintering density, promote solid-phase reaction, reduce porosity, and finally obtain a sintered body with fine crystal structure and more uniform grain size, thereby reducing the total material loss.

[0049] In one embodiment of this application, step S130 includes three stages of sintering: a heating stage, a holding stage, and a cooling stage. The pressed product can be sintered in a sintering furnace to form manganese-zinc ferrite. The heating stage involves raising the temperature from an initial temperature to the holding temperature of the holding stage. This heating stage can be performed in an air atmosphere, where the pressed product is heated from its initial temperature to the set holding temperature. The holding stage can be performed in a nitrogen-oxygen mixed gas atmosphere, where the pressed product is held at the set holding temperature for a certain period, transforming the pressed product from a green blank into a cooked blank. After the holding stage, nitrogen gas is introduced, and a cooling stage is performed in a nitrogen atmosphere, allowing the cooked blank to cool with the furnace to obtain manganese-zinc ferrite.

[0050] In one example, the volume of oxygen in the nitrogen-oxygen mixture is 4.5% to 5.5% (i.e., the oxygen partial pressure is 4.5% to 5.5%).

[0051] In one example, the initial temperature could be room temperature.

[0052] In one example, the insulation temperature during the insulation treatment stage is 1180–1220℃, and the insulation time is 6.5–7.5 hours.

[0053] In one embodiment of this application, the heating stage including the initial temperature is the initial heating stage, and the heating stage including the holding temperature is the final heating stage. The heating rates of the multiple heating stages are arranged in a pulsed, stepped manner, and the heating rate of the initial heating stage is greater than that of the final heating stage. The heating stage may include two heating stages (initial and final), or three heating stages (initial, intermediate, and final), or more heating stages; the specific number is not limited. By arranging the heating rates of the multiple heating stages in a pulsed, stepped manner, the sintering temperature can be adapted to the degree of sintering, avoiding excessively high or low sintering temperatures at different degrees of sintering. This effectively improves sintering density, refines and homogenizes grains, and reduces energy consumption. Moreover, by making the heating rate in the final heating stage lower than that in the initial heating stage, problems such as increased intergranular porosity, excessively large size, poor grain uniformity, and deterioration of material properties caused by excessively rapid heating in the final stage can be avoided.

[0054] In one embodiment of this application, the temperature range of the initial heating stage is 25–200°C, and the heating rate of the initial heating stage is 9.5–10.5°C / min; the temperature range of the final heating stage is 900–1200°C, and the heating rate of the final heating stage is 3.5–4.5°C / min; between the initial heating stage and the final heating stage, the multiple heating stages further include: a first intermediate heating stage, the temperature range of the first intermediate heating stage is 200–500°C, and the heating rate of the first intermediate heating stage is 3.5–4.5°C / min; and a second intermediate heating stage, the temperature range of the second intermediate heating stage is 500–900°C, and the heating rate of the second intermediate heating stage is 9.5–10.5°C / min.

[0055] Example 2

[0056] One embodiment of this application provides a method for preparing manganese-zinc ferrite, the method comprising:

[0057] First, manganese zinc ferrite powder is mixed with polyvinyl alcohol solution to obtain a mixture, and then the mixture is ground.

[0058] The concentration of the polyvinyl alcohol solution is 10%, the degree of alcoholysis of polyvinyl alcohol is 87.0% to 89.0%, and the mixing ratio of manganese zinc ferrite powder to polyvinyl alcohol is 9:1.

[0059] Secondly, the ground mixture is pressed into shape to obtain a pressed product.

[0060] The pressing pressure for the compression molding process is 5 MPa, and the holding time is 10 seconds.

[0061] The pressed product is then sintered to obtain manganese-zinc ferrite.

[0062] The sintering process includes three stages: heating, holding, and cooling.

[0063] The heating process was carried out in an air atmosphere. In the initial heating stage, the temperature was increased from room temperature to 200℃ at a rate of 10℃ / min. In the first intermediate heating stage, the temperature was increased from 200℃ to 500℃ at a rate of 4℃ / min. In the second intermediate heating stage, the temperature was increased from 500℃ to 900℃ at a rate of 10℃ / min. In the final heating stage, the temperature was increased from 900℃ to 1200℃ at a rate of 4℃ / min.

[0064] After the heating stage, the heat preservation stage begins. The heat preservation stage is carried out in a nitrogen-oxygen mixed gas atmosphere in which oxygen occupies 5% of the volume (i.e., oxygen partial pressure is 5%), the heat preservation temperature is 1200℃, and the heat preservation time is 7 hours.

[0065] After the heat preservation stage, the cooling stage begins, which is carried out under high-purity nitrogen. The billet is cooled along with the furnace to obtain manganese-zinc ferrite.

[0066] The remaining details and conditions of each step in this embodiment can be referred to in Embodiment 1, and will not be repeated here.

[0067] Example 3

[0068] This application also provides a manganese-zinc ferrite, which is obtained by the method described in any of the above embodiments. The prepared manganese-zinc ferrite has a loss of 130 mW / cm² under the conditions of 25°C, 50 mT, and 500 kHz. 3 At 25℃, 1194 A / m, and 500 Hz, Bs reaches 457 mT, Br is 91.2 mT, and ΔB is 366 mT; the core density at room temperature is greater than 4.70 g / cm³. 3 .

[0069] In summary, the manganese-zinc ferrite and its preparation method according to the embodiments of this application involve sintering the pressed product through multiple heating stages, with different heating rates adopted in at least two heating stages. This allows the moisture and polyvinyl alcohol in the pressed product to volatilize at a rate adapted to the degree of sintering as the sintering temperature increases, and the gases generated by volatilization to be discharged at a rate adapted to the degree of sintering. In other words, the moisture and polyvinyl alcohol can volatilize in a timely manner, and the gases can be discharged from the pressed product in a timely manner, thereby forming uniform pores and gaps in the manganese-zinc ferrite. At the same time, this makes the microstructure of the manganese-zinc ferrite uniform and dense, which can improve the uniformity of pores and gaps in the manganese-zinc ferrite, increase the sintering density of the manganese-zinc ferrite, and make the grains in the manganese-zinc ferrite more uniform and refined. As a result, the prepared manganese-zinc ferrite maintains low loss at high frequencies while also having high saturation magnetic flux density and low remanence, that is, a manganese-zinc ferrite with a large change in magnetic induction intensity is prepared.

[0070] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of this application. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of this application. All such changes and modifications are intended to be included within the scope of this application as claimed in the appended claims.

[0071] Similarly, it should be understood that, in order to simplify this application and aid in understanding one or more aspects of the application, various features of this application may sometimes be grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of this application. However, this approach should not be construed as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the corresponding claims, the point of application is that the corresponding technical problem can be solved with fewer features than all of a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0072] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0073] It should be noted that the above embodiments are illustrative of this application and not limiting of it, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A method for preparing manganese-zinc ferrite, characterized in that, The method includes: Manganese-zinc ferrite powder is mixed with a polyvinyl alcohol solution to obtain a mixture, and the mixture is then ground; the concentration of the polyvinyl alcohol solution is 9.5%~10.5%, the degree of alcoholysis of the polyvinyl alcohol is 87.0%~89.0%, and the mixing ratio of the manganese-zinc ferrite powder to the polyvinyl alcohol is (8.5~9.5):1; The ground mixture is then subjected to compression molding to obtain a compressed product. The pressed product is subjected to sintering treatment to obtain manganese zinc ferrite; The sintering process includes a heating stage, which comprises multiple heating stages, at least two of which have different heating rates. The multiple heating stages include an initial heating stage, a first intermediate heating stage, a second intermediate heating stage, and a final heating stage. The heating rate of the initial heating stage is greater than the heating rate of the final heating stage, and the heating rates of the multiple heating stages are arranged in a pulsed stepwise pattern. The temperature range of the initial heating stage is 25~200℃, and the heating rate of the initial heating stage is 9.5~10.5℃ / min. The temperature range of the final heating stage is 900~1200℃, and the heating rate of the final heating stage is 3.5~4.5℃ / min; Between the initial heating phase and the final heating phase, the plurality of heating phases further include a first intermediate heating phase and a second intermediate heating phase: The temperature range of the first intermediate heating stage is 200~500℃, and the heating rate of the first intermediate heating stage is 3.5~4.5℃ / min; The temperature range of the second intermediate heating stage is 500~900℃, and the heating rate of the second intermediate heating stage is 9.5~10.5℃ / min.

2. The method as described in claim 1, characterized in that, The pressing pressure during the compression molding process is 4.5~5.5MPa, and the holding time is 8~12s.

3. The method as described in claim 1, characterized in that, The density of the compressed product is 2.7~3.1 g / cm³. 3 .

4. The method as described in claim 1, characterized in that, The sintering process also includes a heat preservation stage and a cooling stage, wherein the heat rise stage involves raising the temperature from the initial temperature to the heat preservation temperature of the heat preservation stage.

5. The method as described in claim 4, characterized in that, The initial heating stage, which includes the initial temperature rise, is the initial heating stage, and the final heating stage, which includes the heat preservation temperature rise, is the final heating stage.

6. The method as described in claim 4, characterized in that, The heat preservation stage has a heat preservation temperature of 1180~1220℃ and a heat preservation time of 6.5~7.5 hours. The atmosphere of the heat preservation stage is a nitrogen-oxygen mixed gas atmosphere.

7. The method as described in claim 6, characterized in that, The oxygen content in the nitrogen-oxygen mixture is 4.5% to 5.5% by volume.

8. A manganese-zinc ferrite, characterized in that, The manganese-zinc ferrite is obtained by the method for preparing manganese-zinc ferrite as described in any one of claims 1 to 7.

Images