High-frequency manganese-magnesium ferrite as well as preparation method and application thereof

Abstract

The invention relates to a high-frequency manganese-magnesium ferrite and a preparation method and application thereof, the high-frequency manganese-magnesium ferrite comprises main components and auxiliary components, and the main components comprise 57.4-59.6 mol% of Fe2O3, more than 0 and less than or equal to 2.0 mol% of MgO and the balance of MnO according to molar percentage content. During preparation, the raw materials in the main components are mixed and pre-sintered in proportion, then the raw materials in the auxiliary components are added to be ground, the binder is added to be granulated, and a formed body is obtained; and sintering the molded body, and cooling the molded body to room temperature in a protective gas atmosphere to obtain the high-frequency manganese-magnesium ferrite, during sintering, the oxygen partial pressure concentration from 700 DEG C to the sintering temperature is controlled to be smaller than or equal to 0.5%. The specific content of magnesium ferrite is used for partially replacing manganese ferrite, so that the resistivity of the composite material is improved, and the high-frequency loss is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ferrites, and in particular to a manganese-magnesium ferrite for high frequency use, a preparation method thereof and an application thereof. Background Art

[0002] Soft ferrite materials and cores made from them are widely used in high-frequency power electronics due to their high resistivity and low power loss at high frequencies. Low-power-loss cores can reduce the temperature rise of electronic devices and improve their energy conversion efficiency. Furthermore, to reduce the size of electronic devices, the operating frequency of ferrite cores is increasing, with some cores exceeding 1MHz. To date, in-depth research has been conducted on the formulation, preparation process optimization, and structural design of traditional MnZn or Mn-based ferrite materials to achieve high-frequency, low-power-loss soft ferrite cores.

[0003] Chinese invention patent publication number CN115536379A discloses a high-frequency, low-loss soft ferrite material, its preparation method, and its application. The material comprises a main ingredient and auxiliary ingredients. The main ingredient comprises, by molar percentage, 58-62 mol% of ferric oxide and 38-42 mol% of manganese oxide. The main components of this Mn-based ferrite, calculated as oxides, are Fe₂O₃ and MnO. While this material overcomes the problem of reduced resonant frequency in MnZn-based ferrites caused by the addition of ZnO, high-frequency losses remain high, prompting a demand for further reduction. Summary of the Invention

[0004] The purpose of the present invention is to provide a manganese magnesium ferrite for high frequency use, a preparation method and an application thereof, by partially replacing manganese ferrite with a specific content of magnesium ferrite to improve the resistivity of the composite material and reduce high frequency loss.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: The first aspect of the present invention provides a manganese magnesium ferrite for high frequency use, wherein the main components comprise 57.4 to 59.6 mol% of Fe2O3, >0 and ≤2.0 mol% of MgO, and the remainder is MnO, calculated by molar percentage; the auxiliary components comprise 400 to 1200 ppm of CaO, 50 to 400 ppm of SiO2, and 200 to 500 ppm of ZrO2, calculated on the total weight of the main components.

[0006] Furthermore, in terms of molar percentage, the ratio of (Fe2O3mol%-50mol%) / MgOmol% in the main component ranges from 4.8 to 14.8.

[0007] Furthermore, the main component consists of 57.4~59.6mol% Fe2O3, >0 and ≤2.0mol% MgO, and the balance is MnO; the auxiliary component, based on the total weight of the main component, consists of 400~1200ppm CaO, 50~400ppm SiO2 and 200~500ppm ZrO2.

[0008] The second aspect of the present invention provides a method for preparing manganese magnesium ferrite for high frequency use, comprising the following steps: S1: mixing the raw materials of the main component in proportion, pre-calcining, then adding the raw materials of the auxiliary components and grinding them, and then adding a binder and granulating them to obtain a molded body; S2: After sintering the molded body, cooling it to room temperature under a protective gas atmosphere to obtain the manganese magnesium ferrite for high frequency use; during sintering, controlling the oxygen partial pressure concentration from 700° C. to the sintering temperature to be ≤0.5%.

[0009] Furthermore, in step S2, the sintering temperature is 1000-1200°C, and the sintering time is 2-10 hours.

[0010] Furthermore, in step S1, the pre-firing temperature is 750-1050° C., and the pre-firing time is 1-6 hours.

[0011] Furthermore, in step S1, the mixing is wet mixing, the mixing medium of the wet mixing is water, and the wet mixing time is 1 to 3 hours; the grinding is wet grinding, the grinding medium of the wet grinding is water, and the wet grinding time is 1 to 3 hours.

[0012] Furthermore, in step S1, the binder is a mixture of one or more selected from polyvinyl alcohol, carboxymethyl cellulose and polyvinyl acetate, and the amount of the binder used is 0.5% to 1.5% based on dry powder.

[0013] Furthermore, in step S1, the granulation is spray granulation.

[0014] Furthermore, in step S2, the protective gas is N2 or Ar.

[0015] A third aspect of the present invention provides an application of manganese-magnesium ferrite for high frequency use, wherein the manganese-magnesium ferrite for high frequency use is used to manufacture a toroidal magnetic core.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The high-frequency manganese magnesium ferrite of the present invention is prepared by adding a specific content of MgO to the main component and partially replacing the manganese ferrite with magnesium ferrite. After the replacement, the resistivity of the composite ferrite is improved, the eddy current loss is reduced, and the problem of high high-frequency loss of manganese ferrite is overcome.

[0017] The present invention also strictly controls the content of accessory components. This is because accessory components can be present at grain boundaries, increasing grain boundary resistivity and reducing eddy current losses, thereby reducing overall losses. When the content of these accessory components is below the disclosed lower limit, the grain boundary resistivity cannot be effectively increased, failing to reduce losses. When the content of these accessory components is above the upper limit, abnormal grain growth can easily occur, exacerbating losses.

[0018] Furthermore, the present invention's method for preparing high-frequency manganese-magnesium ferrite is fully compatible with existing MnZn ferrite preparation processes. By controlling the temperature and oxygen partial pressure during the sintering process, the material's loss performance can be further controlled. When the temperature is below 700°C, the oxygen partial pressure is too low, which not only hinders the discharge of the forming binder but also increases production costs due to the premature introduction of inert protective gas. When the temperature is above 700°C, the excessively high oxygen partial pressure hinders the completion of the solid-phase reaction of the sintered body, resulting in low densification, high porosity, and worsening loss.

[0019] The high-frequency manganese magnesium ferrite of the present invention is used to make a toroidal magnetic core, and is prepared into a standard magnetic core of Φ12×7×5. The saturation magnetic flux density at 100°C is above 430mT, and the power loss of the magnetic core at 1MHz / 50mT and 100°C is below 180kW / m 3 the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 This is the X-ray diffraction (XRD) spectrum of the high-frequency manganese magnesium ferrite of the present invention; Figure 2 This is a scanning electron microscope (SEM) image of the cross section of the high-frequency manganese-magnesium ferrite sintered core of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] The manganese magnesium ferrite for high-frequency use disclosed in this invention comprises a main component and a secondary component. The main component comprises, by mole percentage, 57.4-59.6 mol% Fe₂O₃, >0 and ≤2.0 mol% MgO, with the balance being MnO. By adding a specific amount of MgO to the main component, the material overcomes the drawback of excessive MgO leading to a decrease in the saturation magnetic flux density of the ferrite material and the high high-frequency losses of manganese ferrite. The mole percentage ratio of (Fe₂O₃mol%-50mol%) to (MgO mol%) in the main component ranges from 4.8 to 14.8.

[0023] Based on the total weight of the main components, the secondary components include 400-1200 ppm of CaO, 50-400 ppm of SiO2, and 200-500 ppm of ZrO2. The content of the secondary components is strictly controlled in the present invention because these secondary components can be present at grain boundaries, increasing grain boundary resistivity and reducing eddy current losses, thereby reducing total losses. When the content of these secondary components is below the lower limit, the grain boundary resistivity cannot be effectively increased, and the loss reduction effect cannot be achieved. When the content of these secondary components is above the upper limit, it is easy to cause abnormal grain growth, which worsens the loss.

[0024] The method for preparing the above-mentioned high-frequency manganese magnesium ferrite comprises the following steps: S1: Mix the raw materials of the main component in proportion, pre-sinter, add the raw materials of the auxiliary components, grind them, and then add a binder to granulate to obtain a molded body; S2: After sintering the formed body in step S1, it is cooled to room temperature under a protective gas atmosphere to obtain manganese magnesium ferrite for high frequency use; during sintering, the oxygen partial pressure concentration is controlled to be ≤0.5% from 700° C. to the sintering temperature.

[0025] This preparation method is fully compatible with existing MnZn ferrite preparation processes and further controls the material's loss performance by controlling the temperature and oxygen partial pressure during the sintering process. When the temperature is below 700°C, the oxygen partial pressure is too low, which not only hinders the discharge of the molding binder, but also increases production costs due to the premature introduction of inert protective gas. When the temperature is above 700°C, the excessively high oxygen partial pressure hinders the completion of the solid-phase reaction of the sintered body, resulting in low densification, high porosity, and worsening loss.

[0026] In step S2, the sintering temperature is preferably 1000-1200°C, and the sintering time is preferably 2-10 hours. In step S1, the pre-calcining temperature is preferably 750-1050°C, and the sintering time is preferably 1-6 hours.

[0027] In step S1, wet mixing is adopted, the mixing medium of the wet mixing is water, and the wet mixing time is 1 to 3 hours; wet grinding is adopted during grinding, the grinding medium of the wet grinding is water, and the wet grinding time is 1 to 3 hours.

[0028] In step S1, the binder is a mixture of one or more selected from polyvinyl alcohol, carboxymethyl cellulose and polyvinyl acetate, and the amount of the binder used is 0.5% to 1.5% based on dry powder.

[0029] In step S1, the granulation is spray granulation; in step S2, the protective gas is N2 or Ar.

[0030] The above-mentioned high-frequency manganese magnesium ferrite can be used to make toroidal magnetic cores. For example, the saturation flux density of a standard core of Φ12×7×5 at 100°C is above 430mT, and the power loss of the core at 1MHz / 50mT and 100°C is below 180kW / m 3 the following.

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Example 1 This embodiment provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, comprising the following steps: Step S1: 58.0 mol% of Fe2O3 (272.2 g weighed as Fe2O3), 1.0 mol% of MgO (1.2 g weighed as MgO), and 41.0 mol% of MnO (92.4 g weighed as Mn3O4) as raw materials were wet-ground in a sand mill (grinding medium: water) for 1 h, and then pre-calcined at 900°C for 3 h.

[0033] Based on the mass of the pre-calcined powder, auxiliary components (800 ppm CaO, 200 ppm SiO2, and 400 ppm ZrO2) were added to the pre-calcined material, and secondary sand grinding was performed for 3 hours (wet grinding, with water as the grinding medium). Polyvinyl alcohol (1.0% based on dry powder) was then added, and spray granulation was performed (controlling the inlet temperature at 300°C and the outlet temperature at 100°C) to obtain a molded body. Step S2: Sintering the formed body: During the sintering process, the first heating stage: in this stage, the temperature is first raised from room temperature to 700°C at a heating rate of 2.0°C / min, and the heating is carried out in an atmospheric atmosphere; the second heating stage: the temperature is raised from 700°C to 1150°C at a heating rate of 1.0°C / min, and the oxygen partial pressure in this heating stage is maintained at 0.3%; then, the temperature is kept at 1150°C for 5 hours, and the oxygen partial pressure is maintained at 2.0%; finally, the temperature is cooled to room temperature while maintaining the equilibrium oxygen partial pressure under the protection of N2 to obtain manganese magnesium ferrite for high frequency use.

[0034] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 436mT and the power loss at 1MHz / 50mT was 164kW / m 3 .

[0035] Example 2 This embodiment provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, comprising the following steps: Step S1: 59.6 mol% of Fe2O3 (277.0 g weighed as Fe2O3), 2.0 mol% of MgO (2.3 g weighed as MgO) and 38.4 mol% of MnO (85.7 g weighed as Mn3O4) as raw materials were wet-ground in a sand mill (grinding medium: water) for 1 h, and then pre-calcined at 950°C for 2 h.

[0036] Based on the mass of the pre-calcined powder, auxiliary components (1200 ppm CaO, 100 ppm SiO2, and 300 ppm ZrO2) were added to the pre-calcined material, and secondary sand grinding was performed for 3 hours (wet grinding, with water as the grinding medium). Polyvinyl alcohol (1.0% based on dry powder) was then added, and spray granulation was performed (the inlet temperature was controlled at 300°C and the outlet temperature was controlled at 100°C) to obtain a molded body. Step S2: Sintering the formed body: During the sintering process, the first heating stage is: in this stage, the temperature is first raised from room temperature to 700°C at a heating rate of 2.0°C / min, and the heating is carried out in an atmospheric atmosphere; the second heating stage is: then raised from 700°C to 1130°C at a heating rate of 1.0°C / min, and the oxygen partial pressure in this heating stage is maintained at 0.3%; then, it is kept at 1130°C for 6 hours, and the oxygen partial pressure is maintained at 1.5%; finally, it is cooled to room temperature while maintaining the equilibrium oxygen partial pressure under the protection of N2 to obtain manganese magnesium ferrite for high frequency use.

[0037] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 432mT and the power loss at 1MHz / 50mT was 172kW / m 3 .

[0038] Example 3 This embodiment provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, comprising the following steps: Step S1: 57.4 mol% of Fe2O3 (269.6 g weighed as Fe2O3), 0.5 mol% of MgO (0.6 g weighed as MgO) and 42.1 mol% of MnO (94.9 g weighed as Mn3O4) as raw materials were wet-ground in a sand mill (grinding medium: water) for 1 h, and then pre-calcined at 900°C for 3 h.

[0039] Based on the mass of the pre-calcined powder, auxiliary components (400 ppm CaO, 300 ppm SiO2, and 500 ppm ZrO2) were added to the pre-calcined material, and secondary sand grinding was performed for 2 hours (wet grinding, with water as the grinding medium). Polyvinyl alcohol (1.0% based on dry powder) was then added, and spray granulation was performed (the inlet temperature was controlled at 300°C and the outlet temperature was controlled at 100°C) to obtain a molded body. Step S2: Sintering the formed body: During the sintering process, the first heating stage is: in this stage, the temperature is first raised from room temperature to 700°C at a heating rate of 2.0°C / min, and the heating is carried out in an atmospheric atmosphere; the second heating stage is: then raised from 700°C to 1060°C at a heating rate of 1.0°C / min, and the oxygen partial pressure in this heating stage is maintained at 0.3%; then, it is kept at 1060°C for 5 hours, and the oxygen partial pressure is maintained at 1.0%; finally, it is cooled to room temperature while maintaining the equilibrium oxygen partial pressure under the protection of N2 to obtain manganese magnesium ferrite for high frequency.

[0040] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 444mT and the power loss at 1MHz / 50mT was 117kW / m 3 .

[0041] Comparative Example 1 This example provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, which is basically the same as Example 2, except that the secondary component only contains 1400 ppm CaO.

[0042] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 434mT and the power loss at 1MHz / 50mT was 228kW / m 3 .

[0043] Comparative Example 2 This example provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, which is basically the same as Example 2, except that the secondary component only contains 500 ppm SiO2.

[0044] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 413mT and the power loss at 1MHz / 50mT was 426kW / m 3 .

[0045] Comparative Example 3 This example provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, which is basically the same as Example 3, except that in the second heating stage: from 700°C to 1060°C, the heating rate is 1.0°C / minute, but the oxygen partial pressure in the heating stage is maintained at 2.0%.

[0046] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 405mT and the power loss at 1MHz / 50mT was 233kW / m 3 .

[0047] Comparative Example 4 This example provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, which is basically the same as Example 3, except that during the heat preservation, the temperature is kept at 1060°C for 5 hours and the oxygen partial pressure is maintained at 9.0%.

[0048] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 421mT and the power loss at 1MHz / 50mT was 532kW / m 3 .

[0049] Comparative Example 5 This example provides a manganese magnesium ferrite for high frequency use and a preparation method thereof, which is basically the same as Example 1, except that 59 mol% Fe2O3 (276.1 g weighed as Fe2O3), 3 mol% MgO (3.5 g weighed as MgO) and 38 mol% MnO (85.4 g weighed as Mn3O4) are used as raw materials, and MgO is in excess at this time.

[0050] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core of Ø12×7×5. Then the saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 397mT and the power loss at 1MHz / 50mT was 633kW / m 3 .

[0051] Comparative Example 6 This example provides a preparation method of manganese magnesium ferrite for high frequency use, which is basically the same as Example 1, except that 60 mol% Fe2O3 (278.1 g weighed as Fe2O3), 2 mol% MgO (2.3 g weighed as MgO) and 38 mol% MnO (84.5 g weighed as Mn3O4) are used as raw materials (Fe2O3 is in excess at this time).

[0052] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 445mT and the power loss at 1MHz / 50mT was 369kW / m 3 .

[0053] Comparative Example 7 This example provides a preparation method of manganese magnesium ferrite for high frequency use, which is basically the same as Example 1, except that 58 mol% Fe2O3 (272.5 g weighed as Fe2O3), 2 mol% MgO (2.4 g weighed as MgO) and 40 mol% MnO (90.2 g weighed as Mn3O4) are used as raw materials (in this case, the ratio of (Fe2O3mol%-50mol%) / MgOmol% is 4).

[0054] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 425mT and the power loss at 1MHz / 50mT was 289kW / m 3 .

[0055] Comparative Example 8 This example provides a preparation method of manganese magnesium ferrite for high frequency use, which is basically the same as Example 1, except that 53.2 mol% Fe2O3 (249.7 g weighed as Fe2O3), 0.2 mol% MgO (0.24 g weighed as MgO) and 46.6 mol% MnO (105 g weighed as Mn3O4) are used as raw materials (in this case, the ratio of (Fe2O3mol%-50mol%) / MgOmol% is 16).

[0056] The high frequency manganese magnesium ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 415mT and the power loss at 1MHz / 50mT was 296kW / m 3 .

[0057] Comparative Example 9 This example provides a preparation method of manganese-magnesium-zinc ferrite for high frequency use, which is basically the same as Example 1, except that 58 mol% Fe2O3 (272.5 g weighed as Fe2O3), 1 mol% MgO (1.2 g weighed as MgO), 38.4 mol% MnO (85.7 g weighed as Mn3O4) and 2.6 mol% ZnO (6.2 g weighed as ZnO) are used as raw materials (in this case, the ratio of (Fe2O3mol%-50mol%) / MgOmol% is 8).

[0058] The high frequency manganese magnesium zinc ferrite prepared above was made into a standard magnetic core with a size of 12×7×5. The saturation flux density and power loss of the magnetic core at 100°C were tested using a SY8219 BH analyzer. The results showed that the saturation flux density was 384mT and the power loss at 1MHz / 50mT was 645kW / m 3 .

[0059] In summary, the manganese magnesium ferrite for high frequency disclosed in the present invention partially replaces manganese ferrite with magnesium ferrite by adding a specific content of MgO to the main component. After the replacement, the resistivity of the composite ferrite is improved, the eddy current loss is reduced, and the problem of high high-frequency loss of manganese ferrite is overcome. The manganese magnesium ferrite for high frequency of the present invention is prepared into a standard magnetic core of Φ12×7×5, the saturation magnetic flux density of which is above 430mT at 100°C, and the power loss of the magnetic core at 1MHz / 50mT and 100°C is below 180kW / m 3 the following.

[0060] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A manganese magnesium ferrite for high frequency use, comprising a main component and a subsidiary component, characterized in that: In terms of molar percentage, the main component comprises 57.4-59.6 mol% of Fe2O3, >0 and ≤2.0 mol% of MgO, and the balance is MnO; the auxiliary components, based on the total weight of the main components, comprise 400-1200 ppm of CaO, 50-400 ppm of SiO2, and 200-500 ppm of ZrO2.

2. The high frequency manganese magnesium ferrite according to claim 1, characterized in that: In terms of molar percentage, the ratio of (Fe2O3mol%-50mol%) / MgOmol% in the main component ranges from 4.8 to 14.

8.

3. The high frequency manganese magnesium ferrite according to claim 2, characterized in that: In terms of molar percentage, the main component consists of 57.4-59.6 mol% of Fe2O3, >0 and ≤2.0 mol% of MgO, and the balance is MnO; the secondary component, based on the total weight of the main component, consists of 400-1200 ppm of CaO, 50-400 ppm of SiO2, and 200-500 ppm of ZrO2.

4. The method for preparing high-frequency manganese magnesium ferrite according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: mixing the raw materials of the main component in proportion, pre-calcining, then adding the raw materials of the auxiliary components and grinding them, and then adding a binder and granulating them to obtain a molded body; S2: After sintering the molded body, cooling it to room temperature under a protective gas atmosphere to obtain the manganese magnesium ferrite for high frequency use; during sintering, controlling the oxygen partial pressure concentration from 700° C. to the sintering temperature to be ≤0.5%.

5. The method for preparing high frequency manganese magnesium ferrite according to claim 4, characterized in that: In step S2, the sintering temperature is 1000-1200°C, and the sintering time is 2-10 hours.

6. The method for preparing high frequency manganese magnesium ferrite according to claim 5, characterized in that: In step S1, the pre-firing temperature is 750-1050° C., and the pre-firing time is 1-6 hours.

7. The method for preparing high frequency manganese magnesium ferrite according to claim 4, characterized in that: In step S1, the mixing is wet mixing, the mixing medium of the wet mixing is water, and the wet mixing time is 1 to 3 hours; the grinding is wet grinding, the grinding medium of the wet grinding is water, and the wet grinding time is 1 to 3 hours.

8. The method for preparing high frequency manganese magnesium ferrite according to claim 4, characterized in that: In step S1, the binder is a mixture of one or more selected from polyvinyl alcohol, carboxymethyl cellulose and polyvinyl acetate, and the amount of the binder used is 0.5% to 1.5% based on dry powder.

9. The method for preparing high frequency manganese magnesium ferrite according to claim 4, characterized in that: In step S1, the granulation is spray granulation.

10. Use of the high frequency manganese magnesium ferrite according to any one of claims 1 to 3, characterized in that: The high frequency manganese magnesium ferrite is used to make a toroidal magnetic core.

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