High-frequency low-loss manganese zinc ferrite magnetic core and preparation method thereof

Abstract

The invention provides a high-frequency low-loss manganese zinc ferrite magnetic core and a preparation method thereof, and the preparation method comprises the following steps: (1) mixing base material Fe2O3 powder, MnO powder and ZnO powder, and sequentially carrying out first ball milling treatment, first sintering treatment and spray granulation to obtain granulated powder; and (2) mixing the granulated powder and an additive, and sequentially carrying out second ball milling, compression molding and second sintering treatment to obtain the high-frequency low-loss manganese zinc ferrite magnetic core. The manganese-zinc ferrite magnetic core prepared by the method is relatively low in magnetic loss under the condition of 3-5MHz, and has a wide-range popularization and application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of soft magnetic materials, and particularly relates to a low-loss Mn-Zn ferrite magnetic core for high frequency and a preparation method thereof. Background Art

[0002] Soft magnets themselves do not carry magnetism. Only when an externally applied energized solenoid is present will a magnetic field be generated. When the externally applied current is removed, the magnetic field no longer exists. Ferrite is a type of soft magnet, which refers to a functional ceramic material mainly composed of Fe2O3 and sintered together with other metal oxides such as Mn-Zn, Cu-Zn, Ni-Zn, etc. Among them, Mn-Zn ferrite has the largest output and usage. Ferrite has good magnetic conductivity. Compared with general metals, it has the advantages of weaker coercive force and small residual magnetism after the externally applied current is removed. However, existing ferrites have problems such as high magnetic core loss in high-frequency application scenarios, low conversion rate and easy heating when used for a long time.

[0003] CN110304913A discloses a high-frequency ultra-low-loss Mn-Zn soft ferrite material and a preparation method thereof. The composition of the high-frequency ultra-low-loss Mn-Zn soft ferrite material is mainly composed of 140 parts - 146 parts of Fe2O3, 39 parts - 48 parts of Mn3O4, and 8 parts - 15 parts of ZnO by mass. Trace amounts of CaCO3, CoO, and Cr2O3 are added for the first time; trace amounts of Y2O3, Sm2O3, SiO2, and V2O5 are added for the second time; using the solid-phase method, through batching, sanding, doping, granulation, molding, and atmosphere sintering, a magnetic core material with high-frequency ultra-low loss is prepared.

[0004] CN115724656A discloses a Mn-Zn power ferrite material, a preparation method thereof, and a switching power supply transformer. An iron-containing oxide, a zinc-containing oxide, and a manganese-containing compound are mixed, and first ground and pulverized, and pre-sintered to obtain a pre-sintered powder; doping additives including NiO, In2O3, TiO2, CaO, SiO2, and La2O3 are added to the pre-sintered powder to obtain a secondary powder; the secondary powder is ground and pulverized for the second time to obtain a first precursor, and the first precursor is granulated and pressed to obtain a green body with a specific shape; the green body is subjected to secondary sintering to obtain an MHz-level ultra-high-frequency low-loss Mn-Zn power ferrite material.

[0005] CN107540363A discloses a wide-temperature high-frequency low-loss Mn-Zn soft magnetic ferrite material, which includes a main component, an auxiliary component A and an auxiliary component B. Calculated by weight percentage, the main component includes Fe2O3, MnO and ZnO; based on the weight of the main component, the auxiliary component A is at least two of CaCO3, V2O5, TiO2, Co3O4, and the auxiliary component B is at least three of CaCO3, Nb2O5, TiO2, Co3O4, CuO, MoO, SiO2. The content of SiO2 in the auxiliary component B is determined according to the total amount of impurity SiO2 contained in the main component, ensuring that the percentage of SiO2 in the total weight of the main component in the whole material is 0.025-0.035%. The preparation method of the above material successively includes main component analysis, primary batching, primary sanding, pre-sintering, secondary batching, forming, and sintering.

[0006] However, when the above Mn-Zn ferrite material is used under high-frequency conditions of 3-5 MHz, there is still a problem of relatively high core loss. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a low-loss Mn-Zn ferrite core for high frequency and its preparation method. After the matrix material is subjected to the first sintering treatment and then mixed with a specific additive, the second sintering treatment is carried out, effectively reducing the magnetic loss of the Mn-Zn ferrite core under high-frequency conditions and being suitable for wide-range popularization and application.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of a low-loss Mn-Zn ferrite core for high frequency, and the preparation method includes the following steps:

[0010] (1) After the matrix materials Fe2O3 powder, MnO powder and ZnO powder are mixed, they are successively subjected to the first ball milling treatment, the first sintering treatment and spray granulation to obtain granulated powder;

[0011] (2) After mixing the granulated powder and the additive, they are successively subjected to the second ball milling, pressing and forming and the second sintering treatment to obtain the low-loss Mn-Zn ferrite core for high frequency;

[0012] Based on the granulated powder, the additive includes 2000-5000 ppm CaO powder, 1000-2000 ppm SiO2 powder, 500-1000 ppm Ta2O5 powder, 500-1000 ppm V2O5 powder, 1200-1800 ppm Co3O4 powder and 2200-3000 ppm Al2O3 powder.

[0013] The preparation method of the low-loss Mn-Zn ferrite magnetic core for high frequency first performs a first sintering treatment on the matrix material to reduce the volume shrinkage of the powder raw material during the second sintering treatment, so that the volume of the finally prepared Mn-Zn ferrite magnetic core is controllable; after the first sintering treatment, there is an agglomeration phenomenon in the powder raw material, so spray granulation treatment is carried out to make the particle size of the powder after the first sintering uniform, which is convenient for mixing evenly with the additives. The additives used in the present invention include 2200-3000 ppm Al2O3 powder, which can ensure that the prepared Mn-Zn ferrite magnetic core has a high saturation magnetic flux density and also has a low magnetic loss under high-frequency conditions.

[0014] The additives described in the present invention include 2000-5000 ppm CaO powder. For example, it can be 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable;

[0015] 1000-2000 ppm SiO2 powder. For example, it can be 1000 ppm, 1200 ppm, 1500 ppm, 1700 ppm, 1800 ppm, 1900 ppm or 2000 ppm, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable;

[0016] 500-1000 ppm Ta2O5 powder. For example, it can be 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 950 ppm or 1000 ppm, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable;

[0017] 500-1000 ppm V2O5 powder. For example, it can be 500 ppm, 600 ppm, 650 ppm, 700 ppm, 800 ppm, 900 ppm or 1000 ppm, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable;

[0018] 1200-1800 ppm Co3O4 powder. For example, it can be 1200 ppm, 1300 ppm, 1500 ppm, 1600 ppm, 1650 ppm, 1700 ppm or 1800 ppm, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable;

[0019] and 2200 - 3000 ppm Al2O3 powder, for example, it can be 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2800 ppm or 3000 ppm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0020] Preferably, in terms of mole percentage, the matrix material described in step (1) includes 53.3 - 54.8 mol% Fe2O3 powder, for example, it can be 53.3 mol%, 53.5 mol%, 53.7 mol%, 54 mol%, 54.3 mol%, 54.5 mol% or 54.8 mol%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable;

[0021] 6.5 - 6.9 mol% MnO powder, for example, it can be 6.5 mol%, 6.55 mol%, 6.58 mol%, 6.6 mol%, 6.7 mol%, 6.8 mol% or 6.9 mol%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable; the balance is MnO powder.

[0022] Preferably, the particle sizes of the Fe2O3 powder, MnO powder and ZnO powder described in step (1) are each independently 5 - 50 μm, for example, it can be 5 μm, 10 μm, 20 μm, 30 μm, 35 μm, 40 μm or 50 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable;

[0023] Preferably, the particle sizes D of the Fe2O3 powder, MnO powder and ZnO powder 50 are each independently < 10 μm, for example, it can be 9.9 μm, 9.5 μm, 9 μm, 8 μm, 6 μm, 5 μm or 3 μm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0024] Preferably, the time of the first ball milling treatment described in step (1) is 12 - 20 h, for example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, 18 h or 20 h, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0025] In the present invention, it is preferred that the time of the first ball milling treatment is 12 - 20 h to fully mix and homogenize various powder raw materials in the matrix material.

[0026] Preferably, the temperature of the first sintering treatment is 1350 - 1420°C. For example, it can be 1350°C, 1360°C, 1380°C, 1400°C, 1410°C, 1415°C, 1420°C, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0027] Preferably, in the present invention, the temperature of the first sintering treatment is 1350 - 1420°C, so that a partial spinel - structured ferrite phase is formed in the matrix material, providing a reaction basis for the subsequent second sintering treatment. When the temperature of the first sintering treatment is too low, the formation of the ferrite phase is insufficient. The second sintering treatment requires a higher temperature or a longer time, increasing energy consumption and cost. Moreover, the volatile components are not completely removed, resulting in a decrease in the density, mechanical strength, and magnetic properties of the finally prepared Mn - Zn ferrite magnetic core. When the temperature of the first sintering treatment is too high, some grains grow excessively, resulting in an uneven microstructure and deteriorated magnetic properties of the finally prepared Mn - Zn ferrite magnetic core.

[0028] Preferably, the heat - preservation time of the first sintering treatment is 5 - 6h. For example, it can be 5h, 5.2h, 5.4h, 5.5h, 5.7h, 5.9h, 6h, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0029] Preferably, the particle size of the powder after granulation in step (1) is 5 - 50μm. For example, it can be 5μm, 10μm, 20μm, 30μm, 35μm, 40μm, 50μm, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0030] Preferably, the particle size D of the powder after granulation 50 <10μm. For example, it can be 9.9μm, 9.5μm, 9μm, 8μm, 6μm, 5μm, 3μm, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0031] Preferably, the temperature of the second sintering treatment in step (2) is 1420°C - 1470°C. For example, it can be 1420°C, 1430°C, 1440°C, 1450°C, 1455°C, 1460°C, 1470°C, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0032] Preferably, the heat - preservation time of the second sintering treatment is 6 - 8h. For example, it can be 6h, 6.3h, 6.5h, 6.8h, 7h, 7.5h, 8h, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0033] Preferably, the oxygen partial pressure during the insulation process of the second sintering treatment is 11-13%, for example, it can be 11%, 11.3%, 11.5%, 12%, 12.5%, 12.8% or 13%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] The present invention preferably has an oxygen partial pressure of 11-13% during the heat preservation process of the second sintering treatment to ensure that the manganese-zinc ferrite core finally prepared has low magnetic loss under high frequency conditions. When the oxygen partial pressure is low, it will cause lattice distortion, affect the movement of magnetic domain walls, and increase magnetic loss; when the oxygen partial pressure is high, it will cause Fe 2+ Oxidized to Fe 3+ , destroying the chemical balance of the spinel structure and deteriorating the magnetic properties of the finally prepared manganese-zinc ferrite core.

[0035] Preferably, in step (2), the temperature is increased before the second sintering treatment.

[0036] Preferably, the heating process includes: a heating rate of ≤5°C / h, for example, 5°C / h, 4.8°C / h, 4.5°C / h, 4.3°C / h, 4°C / h, 3.5°C / h or 2°C / h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0037] When the temperature is increased from 20°C to 1100°C, the oxygen partial pressure in the process is ≤0.05%, and may be, for example, 0.05%, 0.048%, 0.045%, 0.043%, 0.04%, 0.035% or 0.03%, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable; then the temperature is increased from 1100°C to the second sintering treatment temperature at a heating rate of ≤3°C / h, and the oxygen partial pressure in the process is 0.05-0.5%, and may be, for example, 0.05%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4% or 0.5%, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0038] Preferably, in step (2), the second sintering treatment is followed by cooling;

[0039] Preferably, the cooling process includes: a cooling rate of ≤2.5°C / h, for example, 2.5°C / h, 2.4°C / h, 2.3°C / h, 2°C / h, 1.8°C / h, 1.5°C / h or 1°C / h, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0040] Cool down from the second sintering treatment temperature to 1150°C, with the oxygen partial pressure during the process ≤ 0.5%, for example, it can be 0.5%, 0.45%, 0.4%, 0.38%, 0.3%, 0.25% or 0.2%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; then at a cooling rate ≤ 5°C / h, for example, it can be 5°C / h, 4.8°C / h, 4.5°C / h, 4.3°C / h, 4°C / h, 3.5°C / h or 2°C / h, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0041] Cool down from 1150°C to 800°C, with the oxygen partial pressure during the process ≤ 0.5%, for example, it can be 0.05%, 0.048%, 0.045%, 0.043%, 0.04%, 0.035% or 0.03%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; then at a cooling rate ≤ 10°C / h, for example, it can be 10°C / h, 9.5°C / h, 9°C / h, 8.5°C / h, 8°C / h, 7.5°C / h or 6°C / h, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0042] Cool down from 800°C to 20°C, with the oxygen partial pressure during the process ≤ 5%; for example, it can be 5%, 4.5%, 4%, 3.8%, 3%, 2.5% or 2%, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] Preferably, grinding is also performed after the cooling.

[0044] Preferably, the grinding includes treating the MnZn ferrite magnetic core after the second sintering treatment with a grinding wheel of 320 mesh or more, for example, it can be 320 mesh, 330 mesh, 350 mesh, 360 mesh, 380 mesh, 400 mesh or 500 mesh, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0045] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0046] (1) In terms of mole percentage, 53.3 - 54.8 mol% of Fe2O3 powder, 6.5 - 6.9 mol% of MnO powder, and the balance being the matrix material of MnO powder are mixed, and then successively subjected to the first ball milling treatment for 12 - 20 h, the first sintering treatment at a temperature of 1350 - 1420°C and a holding time of 5 - 6 h, and spray granulation to obtain granulated powder;

[0047] The particle sizes of the Fe2O3 powder, MnO powder, and ZnO powder are each independently 5 to 50 μm; the particle size D of the Fe2O3 powder, MnO powder, and ZnO powder 50 is each independently <10 μm; the particle size of the granulated powder is 5 to 50 μm; the particle size D of the granulated powder 50 <10 μm;

[0048] (2) After mixing the granulated powder and the additive, second ball milling and pressing are carried out in sequence; then, with a heating rate ≤5 °C / h, the temperature is raised from 20 °C to 1100 °C, and the oxygen partial pressure during the process is ≤0.05%; then, with a heating rate ≤3 °C / h, the temperature is raised from 1100 °C to the second sintering treatment temperature, and the oxygen partial pressure during the process is 0.05 to 0.5%;

[0049] Then, second sintering treatment is carried out; the temperature of the second sintering treatment is 1420 °C to 1470 °C, the holding time is 6 to 8 h, and the oxygen partial pressure during the holding process is 11 to 13%;

[0050] Then, cooling is carried out. With a cooling rate ≤2.5 °C / h, the temperature is cooled from the second sintering treatment temperature to 1150 °C, and the oxygen partial pressure during the process is ≤0.5%; then, with a cooling rate ≤5 °C / h, the temperature is cooled from 1150 °C to 800 °C, and the oxygen partial pressure during the process is ≤0.5%; then, with a cooling rate ≤10 °C / h, the temperature is cooled from 800 °C to 20 °C, and the oxygen partial pressure during the process is ≤5%;

[0051] After cooling, the manganese-zinc ferrite core after the second sintering treatment is subjected to grinding treatment with a grinding wheel of 320 mesh or more to obtain the low-loss manganese-zinc ferrite core for high frequency;

[0052] Based on the granulated powder, the additive includes 2000 to 5000 ppm CaO powder, 1000 to 2000 ppm SiO2 powder, 500 to 1000 ppm Ta2O5 powder, 500 to 1000 ppm V2O5 powder, 1200 to 1800 ppm Co3O4 powder, and 2200 to 3000 ppm Al2O3 powder.

[0053] Second, the present invention also provides a manganese-zinc ferrite core prepared by the preparation method of the low-loss manganese-zinc ferrite core for high frequency as described in the first aspect.

[0054] The manganese-zinc ferrite core prepared by the preparation method of the low-loss manganese-zinc ferrite core for high frequency of the present invention has a magnetic loss ≤150 kW / m under the conditions of 100 °C, 3 MHz, and 3 mT 3 ; under the conditions of 100 °C, 5 MHz, and 9 mT, the magnetic loss ≤100 kW / m 3, it can be applied to high-frequency usage scenarios, still maintaining low core loss, and there will be no problems such as low conversion rate and easy heating during long-term use, and it can replace ordinary ferrites on the current market.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] The preparation method of the low-loss Mn-Zn ferrite core for high frequency provided by the present invention is simple in operation. After mixing the matrix materials, first ball milling, first sintering, and spray granulation are carried out in sequence to improve the mixing uniformity of the matrix materials and initially form a ferrite phase; then it is mixed with specific additives, and second ball milling, pressing and forming, and second sintering are carried out in sequence to obtain a Mn-Zn ferrite core with low magnetic loss under the conditions of 3-5 MHz, which has a wide range of application prospects. Specific embodiments

[0057] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0058] The present invention will be further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0059] Example 1

[0060] This example provides a preparation method of a low-loss Mn-Zn ferrite core for high frequency, and the preparation method includes the following steps:

[0061] (1) Based on mole percentage, 54 mol% of Fe2O3 powder, 6.8 mol% of MnO powder, and the balance of ZnO powder are mixed, and then first ball milling for 15 h, first sintering at a temperature of 1380 °C and a holding time of 5.6 h, and spray granulation are carried out in sequence to obtain granulated powder;

[0062] The particle size of the Fe2O3 powder is 30 μm, D 50 is 8 μm; the particle size of the MnO powder is 20 μm, D 50 is 6 μm; the particle size of the ZnO powder is 40 μm, D 50 is 3 μm; the particle size of the granulated powder is 20 μm, D 50 is 6 μm;

[0063] (2) After mixing the granulated powder and the additives, second ball milling and pressing are carried out in sequence; then, it is heated from 20 °C to 1100 °C at a heating rate of 5 °C / h, and the oxygen partial pressure during the process is 0.05%; then it is heated from 1100 °C to the second sintering treatment temperature at a heating rate of 3 °C / h, and the oxygen partial pressure during the process is 0.1%;

[0064] Then, a second sintering treatment is carried out; the temperature of the second sintering treatment is 1450 °C, the holding time is 6.8 h, and the oxygen partial pressure during the holding process is 11.5%;

[0065] Then, cooling is carried out. It is cooled from the second sintering treatment temperature to 1150 °C at a cooling rate of 2.5 °C / h, and the oxygen partial pressure during the process is 0.5%; then it is cooled from 1150 °C to 800 °C at a cooling rate of 5 °C / h, and the oxygen partial pressure during the process is 0.5%; then it is cooled from 800 °C to 20 °C at a cooling rate of 4 °C / h, and the oxygen partial pressure during the process is 5%;

[0066] After the cooling, the manganese-zinc ferrite magnetic core after the second sintering treatment is subjected to grinding treatment with a 350-mesh grinding wheel to obtain the low-loss manganese-zinc ferrite magnetic core for high frequency;

[0067] Based on the granulated powder, the additives include 3000 ppm CaO powder, 1300 ppm SiO2 powder, 700 ppm Ta2O5 powder, 600 ppm V2O5 powder, 1600 ppm Co3O4 powder and 2600 ppm Al2O3 powder.

[0068] Example 2

[0069] This example provides a preparation method of a low-loss manganese-zinc ferrite magnetic core for high frequency. The preparation method includes the following steps:

[0070] (1) In terms of mole percentage, 53.3 mol% Fe2O3 powder, 6.9 mol% MnO powder, and the balance being the matrix material of MnO powder are mixed, and then first ball milling treatment for 12 h, first sintering treatment at a temperature of 1420 °C and a holding time of 6 h, and spray granulation are carried out in sequence to obtain the granulated powder;

[0071] The particle size of the Fe2O3 powder is 5 μm, D 50 is 5 μm; the particle size of the MnO powder is 50 μm, D 50 is 8.5 μm; the particle size of the ZnO powder is 30 μm, D 50 is 4 μm; the particle size of the granulated powder is 50 μm, D 50 is 7 μm;

[0072] (2) After mixing the granulated powder and the additives, second ball milling and pressing are carried out in sequence; then, it is heated from 20 °C to 1100 °C at a heating rate of 3 °C / h, and the oxygen partial pressure during the process is 0.03%; then it is heated from 1100 °C to the second sintering treatment temperature at a heating rate of 2 °C / h, and the oxygen partial pressure during the process is 0.5%;

[0073] Then, second sintering treatment is carried out; the temperature of the second sintering treatment is 1420 °C, the holding time is 6 - 8 h, and the oxygen partial pressure during the holding process is 11%;

[0074] After that, cooling is carried out. It is cooled from the second sintering treatment temperature to 1150 °C at a cooling rate of 2 °C / h, and the oxygen partial pressure during the process is 0.3%; then it is cooled from 1150 °C to 800 °C at a cooling rate of 4 °C / h, and the oxygen partial pressure during the process is 0.2%; then it is cooled from 800 °C to 20 °C at a cooling rate of 6 °C / h, and the oxygen partial pressure during the process is 4%;

[0075] After cooling, the manganese - zinc ferrite magnetic core after the second sintering treatment is subjected to grinding treatment with a 400 - mesh grinding wheel to obtain the low - loss manganese - zinc ferrite magnetic core for high - frequency use;

[0076] Based on the granulated powder, the additives include 2000 ppm CaO powder, 2000 ppm SiO2 powder, 1000 ppm Ta2O5 powder, 1000 ppm V2O5 powder, 1200 ppm Co3O4 powder and 2200 ppm Al2O3 powder.

[0077] Example 3

[0078] This example provides a preparation method of a low - loss manganese - zinc ferrite magnetic core for high - frequency use, and the preparation method includes the following steps:

[0079] (1) In terms of mole percentage, 54.8 mol% Fe2O3 powder, 6.5 mol% MnO powder, and the balance being the matrix material of MnO powder are mixed, and then first ball milling treatment for 20 h, first sintering treatment at a temperature of 1350 °C and a holding time of 5 h, and spray granulation are carried out in sequence to obtain the granulated powder;

[0080] The particle size of the Fe2O3 powder is 35 μm, D 50 is 3 μm; the particle size of the MnO powder is 50 μm, D 50 is 8 μm; the particle size of the ZnO powder is 25 μm, D 50 is 4 μm; the particle size of the granulated powder is 5 μm, D 50 is 2 μm;

[0081] (2) After mixing the granulated powder and the additives, perform secondary ball milling and press forming in sequence; then, heat from 20 °C to 1100 °C at a heating rate of 1 °C / h, with an oxygen partial pressure of 0.01% during the process; then, heat from 1100 °C to the second sintering treatment temperature at a heating rate of 1 °C / h, with an oxygen partial pressure of 0.1% during the process;

[0082] Then perform the second sintering treatment; the temperature of the second sintering treatment is 1470 °C, the holding time is 6 - 8 h, and the oxygen partial pressure during the holding process is 13%;

[0083] Then perform cooling. Cool from the second sintering treatment temperature to 1150 °C at a cooling rate of 1 °C / h, with an oxygen partial pressure of 0.1% during the process; then cool from 1150 °C to 800 °C at a cooling rate of 1 °C / h, with an oxygen partial pressure of 0.1% during the process; then cool from 800 °C to 20 °C at a cooling rate of 2 °C / h, with an oxygen partial pressure of 1% during the process;

[0084] After cooling, use a 500 - mesh grinding wheel to perform grinding processing on the manganese - zinc ferrite magnetic core after the second sintering treatment to obtain the low - loss manganese - zinc ferrite magnetic core for high - frequency use;

[0085] Based on the granulated powder, the additives include 5000 ppm CaO powder, 1000 ppm SiO2 powder, 500 ppm Ta2O5 powder, 500 ppm V2O5 powder, 1800 ppm Co3O4 powder, and 3000 ppm Al2O3 powder.

[0086] From a comprehensive view of Examples 1 - 3, it can be seen that the preparation method of the low - loss manganese - zinc ferrite magnetic core for high - frequency use provided by the present invention is simple to operate. The finally obtained manganese - zinc ferrite magnetic core, under the conditions of 100 °C, 3 MHz, and 3 mT, has a magnetic loss ≤ 150 kW / m 3 ; under the conditions of 100 °C, 5 MHz, and 9 mT, the magnetic loss ≤ 100 kW / m 3 , and it can be applied to high - frequency usage scenarios. The magnetic core has low loss and will not have problems such as low conversion rate and easy heating during long - term use.

[0087] Example 4

[0088] This example provides a preparation method of a low - loss manganese - zinc ferrite magnetic core for high - frequency use. Except that the temperature of the first sintering treatment is 1300 °C, the rest are the same as in Example 1.

[0089] Example 5

[0090] This example provides a preparation method of a low - loss manganese - zinc ferrite magnetic core for high - frequency use. Except that the temperature of the first sintering treatment is 1450 °C, the rest are the same as in Example 1.

[0091] From a comprehensive comparison of Example 1 with Examples 4 to 5, it can be seen that in Example 4, due to the relatively low temperature of the first sintering treatment, insufficient formation of the ferrite phase occurs, resulting in the need for a higher temperature or longer time for the second sintering treatment, which increases energy consumption and costs. Moreover, since the volatile components are not completely removed, the magnetic loss of the finally prepared MnZn ferrite core under high-frequency conditions is relatively high. In Example 5, due to the relatively high temperature of the first sintering treatment, some grains grow excessively, leading to an uneven microstructure of the finally prepared MnZn ferrite core, and also resulting in a relatively high magnetic loss of the finally prepared MnZn ferrite core under high-frequency conditions.

[0092] Example 6

[0093] This example provides a method for preparing a low-loss MnZn ferrite core for high frequency. Except that the oxygen partial pressure during the heat preservation process of the second sintering treatment is 10%, the rest are the same as in Example 1.

[0094] Example 7

[0095] This example provides a method for preparing a low-loss MnZn ferrite core for high frequency. Except that the oxygen partial pressure during the heat preservation process of the second sintering treatment is 15%, the rest are the same as in Example 1.

[0096] From a comprehensive comparison of Example 1 with Examples 6 to 7, it can be seen that in Example 6, due to the relatively low oxygen partial pressure, lattice distortion occurs, affecting the movement of magnetic domain walls and increasing magnetic loss. In Example 7, due to the relatively high oxygen partial pressure, Fe 2+ is oxidized to Fe 3+ , disrupting the chemical balance of the spinel structure and increasing the magnetic loss of the finally prepared MnZn ferrite core.

[0097] Example 8

[0098] This example provides a method for preparing a low-loss MnZn ferrite core for high frequency. Except that before the second sintering treatment, the temperature is increased from 20 °C to the second sintering treatment temperature at a heating rate of 5 °C / h in one step, the rest are the same as in Example 1.

[0099] Example 9

[0100] This example provides a method for preparing a low-loss MnZn ferrite core for high frequency. Except that after the second sintering treatment, the temperature is decreased from the second sintering treatment temperature to 20 °C at a cooling rate of 2.5 °C / h in one step, the rest are the same as in Example 1.

[0101] From a comprehensive comparison of Example 1 with Examples 8 to 9, it can be seen that in Example 8, a one-time temperature increase leads to insufficient chemical reactions, uneven phase composition, and abnormal grain growth, resulting in deterioration of the magnetic properties of the finally obtained Mn-Zn ferrite magnetic core and an increase in magnetic loss under high-frequency conditions. In Example 9, a one-time temperature decrease leads to insufficient phase transformation, and the finally obtained Mn-Zn ferrite magnetic core cracks due to thermal stress, and the magnetic loss is also relatively large.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing a low-loss Mn-Zn ferrite magnetic core for high-frequency use. Except for not performing the various treatment operations in step (1) and directly mixing the matrix materials Fe2O3 powder, MnO powder, and ZnO powder with the additives, the rest are the same as in Example 1.

[0104] In this comparative example, the matrix materials are not treated and directly mixed with the additives for the preparation of the Mn-Zn ferrite magnetic core, which results in poor removal of volatile impurities. The matrix materials shrink rapidly during the second sintering treatment, causing a large volume change in the finally prepared Mn-Zn ferrite magnetic core, cracking or deformation, and also increasing the magnetic loss of the Mn-Zn ferrite magnetic core.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing a low-loss Mn-Zn ferrite magnetic core for high-frequency use. Except for not adding Al2O3 powder to the additives in step (2), the rest are the same as in Example 1.

[0107] In this comparative example, due to the absence of Al2O3 powder, the finally prepared Mn-Zn ferrite magnetic core has a relatively high magnetic loss when used under high-frequency conditions.

[0108] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived within the technical scope disclosed by the present invention by those skilled in the art all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a low-loss manganese-zinc ferrite core for high frequency use, characterized in that: The preparation method comprises the following steps: (1) After the matrix material Fe2O3 powder, MnO powder and ZnO powder are mixed, a first ball milling treatment, a first sintering treatment and spray granulation are performed in sequence to obtain a granulated powder; (2) after mixing the granulated powder and the additive, performing a second ball milling, a press molding and a second sintering treatment in sequence to obtain the low-loss manganese-zinc ferrite core for high frequency; Based on the granulated powder, the additives include 2000-5000 ppm CaO powder, 1000-2000 ppm SiO2 powder, 500-1000 ppm Ta2O5 powder, 500-1000 ppm V2O5 powder, 1200-1800 ppm Co3O4 powder and 2200-3000 ppm Al2O3 powder.

2. The preparation method according to claim 1, characterized in that: In terms of molar percentage, the matrix material in step (1) comprises 53.3-54.8 mol % Fe2O3 powder, 6.5-6.9 mol % MnO powder, and the remainder is MnO powder.

3. The preparation method according to claim 1 or 2, characterized in that: The particle sizes of the Fe2O3 powder, MnO powder and ZnO powder in step (1) are independently 5 to 50 μm; Preferably, the particle size D of the Fe2O3 powder, MnO powder and ZnO powder is 50 Each independently <10 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Step (1) The first ball milling treatment time is 12 to 20 hours; Preferably, the temperature of the first sintering treatment is 1350-1420°C; Preferably, the holding time of the first sintering treatment is 5 to 6 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The particle size of the powder after granulation in step (1) is 5 to 50 μm; Preferably, the particle size D of the powder after granulation is 50 <10μm.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (2) The temperature of the second sintering treatment is 1420° C. to 1470° C.; Preferably, the holding time of the second sintering treatment is 6 to 8 hours; Preferably, the oxygen partial pressure during the heat preservation process of the second sintering treatment is 11-13%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (2) heating before the second sintering process; Preferably, the heating process includes: heating from 20°C to 1100°C at a heating rate of ≤5°C / h, with an oxygen partial pressure of ≤0.05% during the process; and then heating from 1100°C to a second sintering treatment temperature at a heating rate of ≤3°C / h, with an oxygen partial pressure of 0.05-0.5% during the process.

8. The preparation method according to any one of claims 1 to 7, characterized in that: Step (2) cooling after the second sintering treatment; Preferably, the cooling process includes: cooling from the second sintering treatment temperature to 1150°C at a cooling rate of ≤2.5°C / h, and the oxygen partial pressure during the process is ≤0.5%; then cooling from 1150°C to 800°C at a cooling rate of ≤5°C / h, and the oxygen partial pressure during the process is ≤0.5%; then cooling from 800°C to 20°C at a cooling rate of ≤10°C / h, and the oxygen partial pressure during the process is ≤5%; Preferably, grinding is performed after the cooling; Preferably, the grinding process includes using a grinding wheel with a mesh size of 320 or above to process the manganese-zinc ferrite core after the second sintering process.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: (1) After mixing, in terms of molar percentage, a matrix material of 53.3-54.8 mol% Fe2O3 powder, 6.5-6.9 mol% MnO powder, and the remainder MnO powder is subjected to a first ball milling treatment for 12-20 h, a first sintering treatment at a temperature of 1350-1420° C. and a holding time of 5-6 h, and spray granulation to obtain a granulated powder; The particle sizes of the Fe2O3 powder, MnO powder and ZnO powder are independently 5 to 50 μm; the particle sizes of the Fe2O3 powder, MnO powder and ZnO powder are D 50 Each independently <10 μm; the particle size of the powder after granulation is 5 to 50 μm; the particle size of the powder after granulation D 50 <10 μm; (2) after mixing the granulated powder and the additive, performing a second ball milling and pressing molding in sequence; then, heating from 20° C. to 1100° C. at a heating rate of ≤5° C. / h, with an oxygen partial pressure of ≤0.05% during the process; and then heating from 1100° C. to a second sintering treatment temperature at a heating rate of ≤3° C. / h, with an oxygen partial pressure of 0.05-0.5% during the process; Then, a second sintering treatment is performed; the temperature of the second sintering treatment is 1420°C to 1470°C, the holding time is 6 to 8 hours, and the oxygen partial pressure during the holding process is 11 to 13%; Then, the temperature is lowered from the second sintering treatment temperature to 1150°C at a cooling rate of ≤2.5°C / h, and the oxygen partial pressure during the process is ≤0.5%; then, the temperature is lowered from 1150°C to 800°C at a cooling rate of ≤5°C / h, and the oxygen partial pressure during the process is ≤0.5%; then, the temperature is lowered from 800°C to 20°C at a cooling rate of ≤10°C / h, and the oxygen partial pressure during the process is ≤5%; After the temperature is lowered, the manganese-zinc ferrite core after the second sintering treatment is ground using a grinding wheel with a mesh size of 320 or more to obtain the low-loss manganese-zinc ferrite core for high frequency; Based on the granulated powder, the additives include 2000-5000 ppm CaO powder, 1000-2000 ppm SiO2 powder, 500-1000 ppm Ta2O5 powder, 500-1000 ppm V2O5 powder, 1200-1800 ppm Co3O4 powder and 2200-3000 ppm Al2O3 powder.

10. A manganese-zinc ferrite core prepared by the method for preparing a low-loss manganese-zinc ferrite core for high frequency use as claimed in any one of claims 1 to 9.