A permanent magnet ferrite material, a method for preparing the same and use thereof

Abstract

The present application belongs to the field of magnetic materials. The present application provides a permanent magnet ferrite material and its preparation method and use. The preparation method adds a small amount of ferrite powder as a crystallization seed to the permanent magnet ferrite raw material, thereby accelerating the solid phase reaction, reducing the pre-sintering temperature, preparing a high-performance permanent magnet ferrite material without the addition of lanthanum cobalt; the ferrite crystalline particles in the obtained permanent magnet ferrite material are more uniform, and the generation of coarse crystalline particles is effectively avoided, and the comprehensive magnetic performance is obviously better than that of the same kind of material prepared by the traditional process.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials, and relates to a permanent magnet ferrite material, its preparation method and application. Background Technology

[0002] Permanent magnet ferrite is one of the basic functional materials for permanent magnet DC motors. It can meet the requirements of motor use in various environments, has high sensitivity and stability, and can be widely used in various types of motors with high power, high speed and high torque, such as high-end automotive motors (ABS motors, starter motors, etc.), motorcycle starter motors, household appliances and power tool motors.

[0003] The magnetic properties of permanent magnet ferrites are mainly determined by two crucial parameters: remanent magnetic flux density (B0). r ) and intrinsic coercivity (H cj The initial permanent magnet ferrite materials were mainly strontium ferrite (SrO·6Fe2O3) and barium ferrite (BaO·6Fe2O3) with a magnetoplumb hexagonal structure. To further improve magnetic properties, since the beginning of this century, ion substitution formulation technology, represented by La-Co substitution, has been developed and applied, resulting in a significant improvement in the performance of permanent magnet ferrites. Researchers both domestically and internationally have successively developed permanent magnet ferrite materials with remanence reaching approximately 4500 Gs and intrinsic coercivity reaching 5000 Oe.

[0004] However, as the lowest-cost permanent magnet material, permanent magnet ferrites prepared using La-Co ion substitution technology suffer from significantly increased costs and reduced cost-effectiveness due to the addition of expensive rare earth and rare metal oxides, thus limiting their application range. In recent years, the preparation technology of high-performance permanent magnet ferrites without lanthanum and cobalt has seen significant development. This technology balances magnetic performance and low cost, offering excellent cost-effectiveness and a very broad market application prospect.

[0005] CN104003704B discloses a method for preparing lanthanum- and cobalt-free permanent magnet ferrite. This method uses molten salt as a medium for solid-phase reaction and controls the sintering process by adjusting the type and ratio of molten salt to obtain permanent magnet ferrite materials with higher magnetic properties than those produced by traditional processes without adding lanthanum and cobalt.

[0006] CN101209920B discloses a sintered permanent magnet ferrite and its preparation method, and CN104496444B discloses a low-cost sintered permanent magnet ferrite material and its preparation method. Both use relatively inexpensive Al2O3 or Cr2O3 to replace expensive Co oxides, while significantly reducing or even completely eliminating the addition of rare earth elements, greatly reducing the direct material cost. The prepared sintered permanent magnet ferrite can obtain high magnetic induction intensity and good intrinsic coercivity, which meets the requirements of mid-to-high-end magnet applications.

[0007] CN109836148B discloses a permanent magnet ferrite material without La and Co elements and its preparation method. By optimizing the material composition, improving the uniformity of ferrite grains, and reducing the pre-sintering temperature, the intrinsic coercivity of the material is effectively improved. Under the condition of not adding La and Co elements, a sintered ferrite permanent magnet material with high coercivity and high remanence is prepared.

[0008] Although the optimization solutions provided by the existing technologies can improve material performance to some extent without adding lanthanum and cobalt additives, they are mainly achieved by continuing the ion substitution technology to optimize the formula. Some solutions also extend the process flow and increase energy consumption. Moreover, the improvement of magnetic properties by the existing solutions is relatively limited. Therefore, it is necessary to further develop new technical solutions to achieve higher practical application prospects. Summary of the Invention

[0009] In view of the problems existing in the prior art, the purpose of the present invention is to provide a permanent magnet ferrite material, its preparation method and uses. The preparation method accelerates the solid-state reaction, reduces the pre-calcination temperature, and reduces energy consumption during the pre-calcination process by adding a small amount of permanent magnet ferrite powder as a crystal seed for the ferrite solid-state reaction. Through the improvement of the preparation method, a permanent magnet ferrite material with excellent magnetic properties is obtained without the need for the addition of lanthanum and cobalt.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a permanent magnet ferrite material, the method comprising:

[0012] A permanent magnet ferrite seed crystal is provided, and the permanent magnet ferrite seed crystal is mixed with a permanent magnet ferrite raw material, and then pre-fired and sintered in sequence to obtain a permanent magnet ferrite material.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0014] As a preferred technical solution of the present invention, the permanent magnet ferrite seed crystals include pre-calcined permanent magnet ferrite powder and / or waste permanent magnet ferrite material powder.

[0015] It should be noted that the pre-calcined permanent magnet ferrite powder can be obtained using the pre-calcined material (hereinafter referred to as permanent magnet ferrite main phase material) powder obtained by the preparation method described in this invention (i.e., using seed crystals). When using the pre-calcined material obtained by the preparation method described in this invention, it means that the preparation method of this invention requires the use of an initial seed crystal at the beginning. This initial seed crystal can be the pre-calcined powder obtained by pre-calcining the permanent magnet ferrite raw material using existing technologies, or the pre-calcined powder obtained by pre-calcining the permanent magnet ferrite raw material using processes other than seed crystals in this invention (e.g., batching and mixing, wet grinding, pre-calcination, and dry pulverization). Compared with the pre-calcination temperature in the preparation method of this invention using seed crystal technology, the pre-calcination temperature is relatively higher when the seed crystal technology of this invention is not used to prepare the initial seed crystal.

[0016] It should also be noted that the preparation method described in this invention uses the addition of a small amount of permanent magnet ferrite powder as a seed crystal for the solid-state reaction of ferrite. Therefore, it is not limited to permanent magnet ferrite powder in the pre-sintered powder stage. Using pre-sintered powder as a seed crystal simplifies the process and reduces energy consumption and cost. However, the finished permanent magnet ferrite material obtained after sintering or the waste powder after appropriate treatment can also serve as the seed crystal in the preparation method described in this invention. That is, the permanent magnet ferrite seed crystal described in this invention can also be prepared using conventional methods or waste powder can be selected.

[0017] Preferably, the average particle size of the permanent magnet ferrite seed crystals is 0.8 to 10 μm, such as 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, and more preferably 1 to 5 μm.

[0018] Preferably, the amount of the permanent magnet ferrite seed crystal accounts for 1% to 10% of the total mass of the permanent magnet ferrite raw material, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, and more preferably 2% to 5%.

[0019] In this invention, the main function of adding seed crystals is to ensure uniform dispersion of the seed crystals within the raw material powder during the subsequent pre-calcination process. This allows the seed crystals to adsorb surrounding raw material particles, accelerating the solid-state reaction and promoting rapid ferrite formation. This helps lower the pre-calcination reaction temperature, reduces the number of large ferrite particles in the pre-calcined material, and ultimately results in uniformly crystalline ferrite particles, improving the overall magnetic properties of the material. Simultaneously, it also helps reduce energy consumption during the pre-calcination process. If too few seed crystals are added, they will be ineffective, and the uniformity of the pre-calcined material's crystallization will be relatively low, hindering magnetic property improvement. Conversely, if too many seed crystals are added, the relatively dense ferrite seed powder will be difficult to mix uniformly with the raw material powder during mixing, resulting in uneven ferrite particle size during pre-calcination, with a relatively higher proportion of coarse particles, which also negatively impacts magnetic property improvement.

[0020] As a preferred technical solution of the present invention, the permanent magnet ferrite theoretically generated from the permanent magnet ferrite raw material and the permanent magnet ferrite seed crystal belong to the same permanent magnet ferrite system.

[0021] Preferably, the permanent magnet ferrite system includes lanthanum- and cobalt-free strontium ferrite, lanthanum- and cobalt-free barium ferrite, or lanthanum- and cobalt-free barium strontium ferrite. Lanthanum- and cobalt-free strontium ferrite is preferred.

[0022] Preferably, the chemical formula of the lanthanum- and cobalt-free strontium ferrite includes SrFe. 2n O 19 And 5.5≤n≤6.0, for example, n can be 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0, etc.

[0023] Preferably, the permanent magnet ferrite raw material includes an iron source and a strontium source.

[0024] Preferably, the iron source includes iron oxide.

[0025] Preferably, the strontium source includes strontium carbonate.

[0026] As a preferred embodiment of the present invention, the chemical formula of the lanthanum- and cobalt-free strontium ferrite includes Sr 1-x M x Fe 2n O 19 M is a dopant element, which includes Ca, and 0.05≤x≤0.4, for example, x can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4, etc.; 5.5≤n≤6.0, for example, n can be 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0, etc.

[0027] Preferably, the permanent magnet ferrite raw material further includes a dopant containing M.

[0028] Preferably, the dopant containing M includes calcium carbonate.

[0029] As a preferred technical solution of the present invention, the average particle size of the permanent magnet ferrite raw material is <2μm, for example, 1.9μm, 1.7μm, 1.5μm, 1.2μm, 1μm, 0.8μm, etc.

[0030] Preferably, the mixing method includes wet mixing for 3 to 5 hours (1 hour represents 1 hour or 60 minutes), such as 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, to obtain a first slurry with an average particle size of 0.6 to 1.0 μm, such as 0.90 μm, 0.85 μm, 0.80 μm, 0.75 μm, 0.70 μm, 0.65 μm or 0.60 μm, etc., and then drying the first slurry and pelletizing it to obtain pelletized material, and pre-calcining the pelletized material.

[0031] In the relevant batching steps of the preparation method described in this invention, the average particle size of each raw material is preferably at least below 2 μm. If the batching is further processed by wet mixing to form a slurry, the average particle size of the slurry is preferably at least no greater than 0.6–1 μm. In particular, for the first slurry before pre-firing, if the average particle size of the first slurry is too large, it is easy to cause insufficient pre-firing during the pre-firing process, resulting in an excessively low content of the generated M-phase ferrite.

[0032] Preferably, the pre-firing is carried out in an oxygen-containing atmosphere, and more preferably in air.

[0033] Preferably, the preheating temperature is 1100–1300°C, such as 1100°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, 1200°C, 1220°C, 1240°C, 1260°C, 1280°C, or 1300°C, etc., more preferably 1120–1250°C, and more preferably 1150–1180°C, for a time of 0.5–3 hours, such as 0.5 hours, 0.8 hours, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, or 3 hours, etc.

[0034] In this invention, the addition of permanent magnet ferrite seed powder during the pre-firing process allows for the adsorption of uniformly mixed raw material particles at a relatively low temperature, accelerating the ferrite formation process of the raw material composition and improving crystallization uniformity. Furthermore, it enables pre-firing at a lower temperature to minimize the formation of coarse crystalline particles, thereby improving the overall magnetic properties of the material. Simultaneously, the lower pre-firing temperature also reduces energy consumption during the pre-firing process, thus lowering the manufacturing cost of the pre-firing material.

[0035] As a preferred technical solution of the present invention, the pre-calcined material is dry-pulverized to obtain the permanent magnet ferrite main phase material, which is then sintered and / or used as the permanent magnet ferrite seed crystal.

[0036] Preferably, before the permanent magnet ferrite main phase material is sintered, it is first mixed with secondary additives and wet-milled to obtain a second slurry. The second slurry is then shaped to obtain a molded body, and the molded body is then sintered.

[0037] In this invention, the main formula is composed of permanent magnet ferrite raw materials and seed crystals to obtain the main phase material; this invention further ensures a reduction in pre-firing temperature by optimizing the main formula and the secondary additive formula.

[0038] Preferably, the secondary additive includes at least one of SiO2, CaCO3, Al2O3, Cr2O3, ZnO, SrCO3, or H3BO3.

[0039] Preferably, the total amount of the secondary additives accounts for 1.0% to 5.0% of the mass of the permanent magnet ferrite main phase, for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, or 5%, etc.

[0040] Preferably, based on the mass of the permanent magnet ferrite main phase material as 100%, the amount of SiO2 is 0.05% to 3%, the amount of CaCO3 is 0.4% to 3%, the amount of Al2O3 is 0% to 3%, the amount of Cr2O3 is 0% to 1.5%, the amount of ZnO is 0% to 0.6%, the amount of SrCO3 is 0.1% to 1%, and the amount of H3BO3 is 0% to 0.8%.

[0041] Preferably, the average particle size of the secondary additive is <2μm, for example, 1.9μm, 1.7μm, 1.5μm, 1.3μm, 1μm, 0.8μm, etc.

[0042] Preferably, the average particle size of the second slurry is 0.6 to 1 μm, for example, 0.90 μm, 0.85 μm, 0.80 μm, 0.75 μm, 0.70 μm, 0.65 μm or 0.60 μm, and the solid content is 65 wt% to 80 wt%, for example, 65 wt%, 68 wt%, 70 wt%, 72 wt%, 74 wt%, 76 wt%, 78 wt% or 80 wt%.

[0043] In this invention, the solid content (water content) of the resulting slurry can be adjusted using pure water.

[0044] Preferably, the forming method includes magnetic field forming.

[0045] Preferably, the magnetic field strength of the magnetic field forming is >10000Oe, such as 11000Oe, 13000Oe, 15000Oe or 18000Oe.

[0046] In this invention, if the magnetic field strength of the magnetic field forming is too low, the orientation of the magnetic particles in the formed body will be too low, thereby affecting the remanence of the final magnet.

[0047] As a preferred embodiment of the present invention, the sintering method includes first performing a first sintering at 100–600°C, for example, 100°C, 130°C, 150°C, 180°C, 200°C, 230°C, 250°C, 280°C, 300°C, 320°C, 350°C, 380°C, 400°C, 430°C, 450°C, 480°C, 500°C, 530°C, 550°C, 580°C, or 600°C, for 0.5–2 hours, for example, 0.5 hours, 0.8 hours, or 1 hour. The second sintering is carried out at 1180–1230°C, for example, 1180°C, 1190°C, 1200°C, 1210°C, 1220°C, or 1230°C, preferably 1190–1220°C, for 0.5–3 hours, for example, 0.5 hours, 0.8 hours, 1 hour, 1.3 hours, 1.5 hours, 1.8 hours, 2 hours, 2.3 hours, 2.5 hours, 2.8 hours, or 3 hours.

[0048] Preferably, the second sintering is carried out in an oxygen-containing atmosphere, and more preferably in air.

[0049] As a preferred technical solution of the present invention, the preparation method includes:

[0050] (1) Synthesizing initial permanent magnet ferrite seed crystals, wherein the initial permanent magnet ferrite seed crystals are pre-calcined powders of lanthanum- and cobalt-free strontium ferrite, and the chemical formula of the lanthanum- and cobalt-free strontium ferrite is SrFe. 2n O 19 The raw materials for preparing the initial permanent magnet ferrite seed crystals include iron source iron oxide and strontium source strontium carbonate, which are measured and mixed according to the chemical formula, and then wet-milled to obtain an initial slurry with an average particle size of 0.6 to 1 μm. The initial slurry is then pre-calcined in air at 1120 to 1200°C for 0.5 to 3 hours, and then dry-milled until the average particle size is 0.8 to 10 μm. The pre-calcined powder is then used as the initial permanent magnet ferrite seed crystal.

[0051] (2) Prepare the permanent magnet ferrite raw materials, including iron source iron oxide, strontium source strontium carbonate, and calcium carbonate dopant containing calcium elements, according to the chemical formula Sr1-x Ca x Fe 2n O 19 The mixture is measured and mixed with 0.05≤x≤0.4 and 5.5≤n≤6.0. At the same time, the initial permanent magnet ferrite seed crystals are added at 1% to 10% of the total mass of the permanent magnet ferrite raw materials and wet-mixed for 3 to 5 hours to obtain a first slurry with an average particle size of 0.6 to 1 μm. The first slurry is then dried and pelletized to obtain pelletizing material.

[0052] (3) The first slurry is pre-fired at 1120-1200℃ for 0.5-3 hours in an oxygen-containing atmosphere and then dry coarsely crushed to obtain permanent magnet ferrite main phase material. A portion of the obtained permanent magnet ferrite main phase material is used for subsequent sintering, and the other portion of the obtained permanent magnet ferrite main phase material is further crushed to an average particle size of 0.8-10μm as permanent magnet ferrite seed crystals.

[0053] (4) The permanent magnet ferrite main phase material for sintering is mixed with secondary additives, including at least one of SiO2, CaCO3, Al2O3, Cr2O3, ZnO, SrCO3 or H3BO3. The total amount of the secondary additives accounts for 1% to 5% of the mass of the permanent magnet ferrite main phase material for sintering. The mixture is wet-milled to obtain a second slurry with an average particle size of 0.6 to 1 μm and a solid content of 65 wt% to 80 wt%. Then, the mixture is magnetically formed under a magnetic field strength of >10000 Oe to obtain a shaped body.

[0054] (5) The obtained molded body is first sintered at 200-400℃ for 0.5-2 hours, and then sintered in air at 1180-1230℃ for 0.5-3 hours to obtain permanent magnet ferrite material.

[0055] In a second aspect, the present invention provides a permanent magnet ferrite material, obtained according to the preparation method described in the first aspect.

[0056] Thirdly, the present invention provides an application of the permanent magnet ferrite material described in the second aspect, the application including an electric motor.

[0057] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0058] This invention accelerates the solid-state reaction and reduces the pre-calcination temperature by adding a small amount of ferrite powder as a crystal seed to the permanent magnet ferrite raw material, thereby preparing a high-performance permanent magnet ferrite material without the need for the addition of lanthanum and cobalt. The resulting permanent magnet ferrite material has more uniform ferrite crystal particles, and because the generation of coarse crystal particles is effectively avoided, its comprehensive magnetic properties are significantly better than those of similar materials prepared by traditional processes.

[0059] This invention further optimizes the main formula and the secondary additive formula, thereby ensuring a lower pre-firing temperature and effectively reducing the energy consumption during the pre-firing process, thus further improving the cost-effectiveness of the material. Detailed Implementation

[0060] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0061] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0062] Example 1

[0063] This embodiment provides a method for preparing permanent magnet ferrite, including:

[0064] (1) Synthesizing initial permanent magnet ferrite seed crystals, wherein the initial permanent magnet ferrite seed crystals are pre-calcined powders of lanthanum- and cobalt-free strontium ferrite, and the chemical formula of the lanthanum- and cobalt-free strontium ferrite is SrFe. 12 O 19 The raw materials for preparing the initial permanent magnet ferrite seed crystals include 5.0 kg of iron source red iron with a purity of 99.5% and 0.78 kg of strontium source strontium carbonate with a purity of 98.5%. These are placed in a sand mill, and about 7 kg of tap water is added. The mixture is then wet-milled for 2 hours to obtain an initial slurry with an average particle size of 0.6-1 μm. The initial slurry is then pre-calcined in air at 1250°C for 2 hours, and then dry-milled until the average particle size is 5 μm. The pre-calcined powder is then used as the initial permanent magnet ferrite seed crystal.

[0065] (2) Prepare permanent magnet ferrite raw materials, including iron source red iron with a purity ≥99.0wt% and an average particle size of 1.6μm, strontium source strontium carbonate with a purity ≥97.0wt% and an average particle size of 1.8μm (main impurities include BaCO3≤1.0wt%, CaCO3≤0.6wt%), and calcium carbonate dopant with a purity ≥98.5wt% and an average particle size of 1.5μm. The chemical formula of the permanent magnet ferrite generated according to the theory of permanent magnet ferrite raw materials is Sr 1-x Ca x Fe 2n O 19 The mixture was metered and mixed with 0.05≤x≤0.4 and 5.5≤n≤6.0. At the same time, the initial permanent magnet ferrite seed crystals (as shown in Table 1) were added at 1% to 10% of the total mass of the permanent magnet ferrite raw materials. The mixture was then wet-milled in a ball mill for 5 hours to obtain a first slurry with an average particle size of 0.85μm. The first slurry was dried in an oven and then pelletized to obtain pelletized material.

[0066] (3) The pelletizing material is pre-fired at 1140°C for 1.5 hours in an oxygen-containing atmosphere and then dry coarsely crushed to obtain permanent magnet ferrite main phase material (pre-fired material), and then dry coarsely crushed to obtain 450g of crushed material.

[0067] (4) The pulverized material is mixed with secondary additives, including SiO2, CaCO3 and Cr2O3, which account for 0.5%, 0.75% and 0.4% of the mass of the pulverized material, respectively. Then, 680 mL of tap water is added and the mixture is wet-milled in a ball mill for 20 hours until the average particle size is 0.74 μm. The water content is adjusted by using tap water to obtain a second slurry with a solid content of 70 wt%. The second slurry is then magnetically shaped under a magnetic field strength of 11000 Oe to obtain a shaped body. The shaped body is a cylinder with a diameter of 43.2 mm and a height of 12 mm, and the molding pressure is 10 MPa.

[0068] (5) The obtained molded body is first sintered at 300°C for 1 hour, and then the heating rate is set to 150°C / hr, and the second sintering is carried out in air at 1220°C for 1.5 hours to obtain permanent magnet ferrite material.

[0069] Characterization and Testing I

[0070] The upper and lower surfaces of the permanent magnet ferrite material obtained in Example 1 were ground, and its remanent magnetic induction (Br), coercivity (Hcb), intrinsic coercivity (Hcj), and maximum energy product (BH)m at room temperature (20℃) were measured. The results are shown in Table 1.

[0071] Table 1

[0072]

[0073] As can be seen from Table 1, by optimizing and adjusting the formula and adding different proportions of ferrite powder as crystal seeds, relatively superior comprehensive magnetic properties can be obtained under certain process technology conditions.

[0074] Example 2

[0075] This embodiment provides a method for preparing permanent magnet ferrite. Compared with embodiment 1, this embodiment adjusts the average particle size of the initial permanent magnet ferrite seed in step (1), adjusts the amount of initial permanent magnet ferrite seed added in step (2), and adjusts the pre-firing temperature in step (3). The specific details are shown in Table 2. Except for the above, the other conditions are exactly the same as those in embodiment 1.

[0076] Characterization and Testing II

[0077] The upper and lower surfaces of the permanent magnet ferrite material obtained in Example 2 were ground, and its remanent magnetic induction (Br), coercivity (Hcb), intrinsic coercivity (Hcj), and maximum magnetic energy product (BH)m at room temperature (20℃) were measured. The results are shown in Table 2.

[0078] Table 2

[0079]

[0080] As can be seen from Table 2, by optimizing and adjusting the formula and adding different proportions of ferrite powder as crystal seeds, under certain process conditions, adding more than 2% can obtain relatively excellent comprehensive magnetic properties.

[0081] Examples 3 and 4

[0082] This embodiment provides a method for preparing permanent magnet ferrite. Compared with embodiment 1, this embodiment does not prepare the initial permanent magnet ferrite seed in step (1). Instead, in embodiment 3, a portion of the permanent magnet ferrite main phase material (pre-burned material) obtained in step (3) of embodiment 1 is used and then pulverized to an average particle size of 5.8 μm as permanent magnet ferrite seed. In embodiment 4, the permanent magnet ferrite material obtained in embodiment 1 is used and then recycled into waste magnetic powder with an average particle size of 2.8 μm as permanent magnet ferrite seed. At the same time, the amount of permanent magnet ferrite seed added in step (2) of embodiment 3 and embodiment 4 is adjusted, and the pre-burning temperature in step (3) is also adjusted. The specific details are shown in Table 3. Except for the above, the other conditions are exactly the same as in embodiment 1.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing permanent magnet ferrite, which does not include step (1) and does not use any permanent magnet ferrite seed crystals. Except for the above, the other conditions are exactly the same as in Example 1.

[0085] Characterization and Testing III

[0086] The upper and lower surfaces of the permanent magnet ferrite materials obtained in Examples 3, 4 and Comparative Example 1 were ground, and their remanent magnetic induction (Br), coercivity (Hcb), intrinsic coercivity (Hcj) and maximum energy product (BH)m at room temperature (20℃) were measured. The results are shown in Table 3.

[0087] Table 3

[0088]

[0089] As can be seen from Table 3, by optimizing and adjusting the formula and adding different proportions of ferrite powder as crystal seeds, under certain process conditions, adding more than 2% can obtain relatively excellent comprehensive magnetic properties.

[0090] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0091] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0092] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method of producing a permanent magnet ferrite material, characterized by, The preparation method includes: A permanent magnet ferrite seed crystal is provided, and the permanent magnet ferrite seed crystal is mixed with a permanent magnet ferrite raw material, and then pre-fired and sintered in sequence to obtain a permanent magnet ferrite material. The amount of the permanent magnet ferrite seed crystal accounts for 1% to 10% of the total mass of the permanent magnet ferrite raw material; The permanent magnet ferrite seed crystals include pre-calcined permanent magnet ferrite powder and / or waste permanent magnet ferrite material powder. The permanent magnet ferrite theoretically generated from the permanent magnet ferrite raw material and the permanent magnet ferrite seed crystal belong to the same permanent magnet ferrite system; The permanent magnet ferrite system includes lanthanum- and cobalt-free strontium ferrite, lanthanum- and cobalt-free barium ferrite, or lanthanum- and cobalt-free barium strontium ferrite. The pre-firing temperature is 1100~1300℃.

2. The production method according to claim 1, characterized by, The average particle size of the permanent magnet ferrite seed crystals is 0.8~10μm.

3. The preparation method according to claim 1, characterized in that, The average particle size of the permanent magnet ferrite seed crystals is 1~5μm.

4. The production method according to claim 1, characterized by, The amount of the permanent magnet ferrite seed crystals used accounts for 2% to 5% of the total mass of the permanent magnet ferrite raw materials.

5. The preparation method according to claim 1, characterized in that, The chemical formula of the lanthanium-free cobalt-free strontium ferrite includes SrFe 2n O 19 , and 5.5≤n≤6.0; the permanent ferrite raw material includes an iron source and a strontium source.

6. The preparation method according to claim 5, characterized in that, The iron source includes iron oxide.

7. The preparation method according to claim 5, characterized in that, The strontium source includes strontium carbonate.

8. The method of claim 1, wherein, The chemical formula of the lanthanum- and cobalt-free strontium ferrite includes Sr 1-x M x Fe 2n O 19 M is a dopant element, M includes Ca, and 0.05≤x≤0.4, 5.5≤n≤6.0; the permanent magnet ferrite raw material also includes a dopant containing M.

9. The production method according to claim 8, characterized by, The dopant containing M includes calcium carbonate.

10. The method of claim 1, wherein, The average particle size of the permanent magnet ferrite raw material is <2μm.

11. The method of claim 1, wherein, The mixing method includes wet mixing for 3-5 hours to obtain a first slurry with an average particle size of 0.6-1 μm, drying the first slurry and then pelletizing it to obtain pelletized material, and pre-firing the pelletized material.

12. The method of claim 1, wherein, The pre-firing is carried out in an oxygen-containing atmosphere.

13. The method of claim 1, wherein, The pre-firing is carried out in air.

14. The method of claim 1, wherein, The preheating time is 0.5 to 3 hours.

15. The method of claim 1, wherein, The pre-calcined material is then dry-pulverized to obtain the main phase of permanent magnet ferrite, which is then sintered and / or used as seed crystals for the permanent magnet ferrite.

16. The method of claim 15, wherein, Before the permanent magnet ferrite main phase material is sintered, it is first mixed with secondary additives and wet-milled to obtain a second slurry. The second slurry is then shaped to obtain a molded body, which is then sintered.

17. The method of claim 16, wherein the method further comprises, The secondary additives include at least one of SiO2, CaCO3, Al2O3, Cr2O3, ZnO, SrCO3, or H3BO3.

18. The method of claim 16, wherein, The total amount of the secondary additives is 1.0% to 5.0% of the mass of the permanent magnet ferrite main phase.

19. The method of claim 16, wherein, The average particle size of the secondary additive is <2μm.

20. The method of claim 16, wherein, The average particle size of the second slurry is 0.6~1μm, and the solid content is 65wt%~80wt%.

21. The method of claim 16, wherein, The forming method includes magnetic field forming.

22. The method of claim 21, wherein, The magnetic field strength for the magnetic field shaping is >10000Oe.

23. The method of claim 1, wherein, The sintering method includes first sintering at 100~600℃ for 0.5~2h, and then sintering at 1180~1230℃ for 0.5~3h.

24. The method of claim 23, wherein, The second sintering is carried out in an oxygen-containing atmosphere.

25. The preparation method according to claim 23, characterized in that, The second sintering is carried out in air.

26. The method of claim 1, wherein, The preparation method includes: (1) Synthesizing initial permanent magnet ferrite seed crystals, wherein the initial permanent magnet ferrite seed crystals are pre-calcined powders of lanthanum- and cobalt-free strontium ferrite, and the chemical formula of the lanthanum- and cobalt-free strontium ferrite is SrFe 2n O 19 The raw materials for preparing the initial permanent magnet ferrite seed crystals include iron source iron oxide and strontium source strontium carbonate, which are measured and mixed according to the chemical formula, and then wet-milled to obtain an initial slurry with an average particle size of 0.6~1μm. The initial slurry is pre-calcined in air at 1100~1300℃ for 0.5~3h, and then dry-pulverized until the average particle size is 0.8~10μm. The pre-calcined powder is then used as the initial permanent magnet ferrite seed crystal. (2) Prepare the raw materials for the permanent magnet ferrite, including iron source iron oxide, strontium source strontium carbonate, and calcium carbonate dopant containing calcium element, according to the chemical formula Sr 1-x Ca x Fe 2n O 19 The mixture is measured and mixed with 0.05≤x≤0.4 and 5.5≤n≤6.

0. At the same time, the initial permanent magnet ferrite seed crystals are added at 1%~10% of the total mass of the permanent magnet ferrite raw materials and wet-mixed for 3~5 hours to obtain a first slurry with an average particle size of 0.6~1μm. The first slurry is then dried and pelletized to obtain pelletizing material. (3) The pelletizing material is pre-fired at 1100~1300℃ for 0.5~3h in an oxygen-containing atmosphere and then dry coarsely crushed to obtain permanent magnet ferrite main phase material. A portion of the obtained permanent magnet ferrite main phase material is used for subsequent sintering, and the other portion of the obtained permanent magnet ferrite main phase material is further crushed to an average particle size of 0.8~10μm as permanent magnet ferrite seed crystals. (4) The permanent magnet ferrite main phase material for sintering is mixed with secondary additives, including at least one of SiO2, CaCO3, Al2O3, Cr2O3, ZnO, SrCO3 or H3BO3, and the total amount of the secondary additives accounts for 1.0% to 5.0% of the mass of the permanent magnet ferrite main phase material for sintering. The mixture is wet-milled to obtain a second slurry with an average particle size of 0.6 to 1 μm and a solid content of 65 wt% to 80 wt%. Then, the mixture is magnetically formed under a magnetic field strength of >10000 Oe to obtain a shaped body. (5) The obtained molded body is first sintered at 100~600℃ for 0.5~2h, and then sintered in air at 1180~1230℃ for 0.5~3h to obtain permanent magnet ferrite material.

27. A permanent magnet ferrite material, characterized by, The preparation method according to any one of claims 1-26 is obtained.

28. Use of the permanent ferrite material of claim 27, characterized in that The applications include motors.

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