High-voltage permanent magnet ferrite and method for manufacturing the same

Abstract

The application provides a high-voltage-resistant permanent magnet ferrite and a preparation method thereof, and belongs to the technical field of permanent magnet ferrite. 1‑m‑y R y Sr m Fe 2n‑z‑ x M z B x O 1+3n The application also provides a preparation method of the high-voltage-resistant permanent magnet ferrite, which comprises the following steps: mixing and blending, pre-sintering, crushing, forming and sintering. 预烧 The application optimizes the pre-sintering temperature matched with the starting raw materials, adopts the sintering process of "slow temperature rising and fast temperature falling" for the formed compact, and adopts the sintering technology of controlling the oxygen content in the atmosphere to be 18-21% when the formed compact is sintered at 1100-1180 DEG C, so that the high-voltage-resistant permanent magnet ferrite with good microstructure, voltage resistance, magnetic performance, stability of the magnetic parameters of the magnet under dynamic working conditions and the like is finally obtained, and the actual demand is met.

Description

TECHNICAL FIELD

[0001] The application relates to a permanent magnet ferrite and a preparation method thereof, in particular to a high-voltage-resistant permanent magnet ferrite and a preparation method thereof, and belongs to the technical field of permanent magnet ferrites. BACKGROUND

[0002] The permanent magnet ferrite is widely applied to the fields of automobiles, motorcycles, televisions, audios, computers, communication terminal machines and medical instruments due to high magnetic performance and excellent corrosion resistance.

[0003] At present, the permanent magnet ferrite is generally obtained by a traditional process, and the permanent magnet ferrite is mainly strontium ferrite (SrFe 12 O 19 ) with an M-type magnetoplumbite structure. The permanent magnet ferrite is manufactured by a powder metallurgy method. First, iron oxide raw materials and strontium carbonate raw materials are mixed, a preliminary solid-phase reaction is generated through pre-sintering, and pre-sintered material blocks (or material balls) are obtained; second, the pre-sintered material blocks (or material balls) are coarsely crushed, and the average particle size is controlled to be 3-5 microns; then, the material is further finely crushed to particles with an average particle size of 0.5-1.0 microns by taking water as a medium; in the fine crushing process, additives such as SiO2, SrCO3, CaCO3, H3BO3, Al2O3 and Cr2O3 which can control the grain growth of the product, improve the density of the product and thus improve the magnetic performance of the material are often added; finally, the ground material slurry is formed into a green body in a magnetic field, and the obtained formed green body is sintered and ground to obtain a permanent magnet ferrite element with a specified size and shape.

[0004] With the development of miniaturization and light weight of electronic components and devices, higher magnetic performance and higher reliability are required for the permanent magnet ferrite components. Compared with the traditional strontium ferrite, the permanent magnet ferrite material obtained by the La-Co or Ca-La-Co ion composite substitution technology, the SiO2 doping technology for refining the grain size and the CaCO3-SiO2 doping technology has higher coercivity, remanence and magnetic energy product. For example, the ferrite magnet A 1-x R x (Fe 12- y Me y z is disclosed in the prior art “CN109155175A”, but a large amount of rare earth lanthanum oxide and a large amount of cobalt oxide are added, for example, A=Sr, R=La and Me=Co in Example 1; in addition, x=0.82, y=0.39 and z=0.94, the production cost is relatively high, and the large amount of Fe 2+ directly leads to poor voltage resistance of the product; and the H CJ ​Not high, Example 1 shows 2500 Oe. The composition of the ferrite sintered magnet in CN106977191A is Ca 1-w-x La w A x Fe z Co m Mn a O 19 , and its typical composition in the embodiment is A = Sr, w = 0.39, x = 0.14, z = 9.05, m = 0.25, w / m = 1.6, SiO2 = 0.81 mass%, a large amount of SiO2 is added, and production practice shows that the existing La-Co or Ca-La-Co ion composite substitution technology, SiO2 doping technology for refining grains, and CaCO3-SiO2 doping technology will all cause the pressure resistance of the permanent magnet ferrite to decrease significantly, and the permanent magnet ferrite element usually works in a state close to magnetic saturation. If the pressure resistance of the permanent magnet ferrite used by the rotor is low, the external voltage or static voltage of the micro motor during operation can form a loop through the motor bearing, the iron core, and the permanent magnet ferrite element, and discharge and break down the chip of the core component of the controller, thereby causing the overall failure of the intelligent control system. In addition, the existing technologies such as CN109155175A and CN106977191A do not mention the pressure resistance of the permanent magnet ferrite and its control method, nor do they mention the stability control method of the magnetic parameter of the magnet under dynamic working conditions.

[0005] When the magnetic performance of the magnet material reaches a certain level, it is difficult to further improve. If further improvement is required, the usual approach is to further grind the slurry, but in fact, if the average particle size of the slurry obtained by wet micro-pulverization is ≤0.7 μm, the drainage time will increase significantly when the slurry is formed in a magnetic field, and the forming efficiency will decrease greatly, which will increase the manufacturing cost of the magnet of the magnetoplumbite type sintered permanent magnet ferrite. If a slurry with an average particle size of >0.7 μm is used for forming in a magnetic field, the forming efficiency will be significantly improved, but as known in the art, the magnetic performance of the permanent magnet ferrite will decrease with the increase of the average particle size of the slurry. The existing technology CN111470858A mentions a high-pressure-resistant permanent magnet ferrite magnet and its manufacturing method, and its molecular formula is SrFe 2n O 19 , where n = (5.8-6.2), and in its embodiment, the slurry for forming is 0.7 μm; and when the La addition amount is 3%, the magnetic performance of the product is improved to a certain extent, Br = 418 mT (4.18 kGs), intrinsic coercive force H CJ = 346 kA / m (4.325 kOe), and the comprehensive performance M* = 5.62 (industry common practice, when the magnetic material H CJ is lower than 4 KOe, the CGS unit is used, and M *The value comparison material has a comprehensive performance, wherein M * =B r + (1 / 3) H CJ ).

[0006] In summary, a permanent ferrite and a preparation method thereof are sought, which has good stability of magnetic parameters under dynamic working conditions, and excellent magnetic properties and voltage resistance characteristics. SUMMARY

[0007] In order to overcome the deficiencies of the prior art, the application provides a high-voltage-resistant permanent ferrite and a preparation method thereof. The application not only provides a high-voltage-resistant permanent ferrite with excellent magnetic properties, but also provides a corresponding preparation method, thereby ensuring excellent characteristics of the permanent ferrite.

[0008] In order to achieve the above technical purposes, the following technical solutions are provided:

[0009] The first purpose of the technical solutions is to provide a high-voltage-resistant permanent ferrite, which is of formula Ca 1-m- y R y Sr m Fe 2n-z-x M z B x O 1+3n represents;

[0010] wherein R is at least one element selected from La, Nd, and Pr, and must contain La; M is at least one element selected from Co, Zn, Ni, Mn, and Cu, and must contain Co;

[0011] x, y, z, m, and n respectively represent the addition ratio of each metal oxide or salt,

[0012] x is 0.001-0.1,

[0013] y is 0.2-0.5,

[0014] 1-m-y is 0.3-0.5,

[0015] z is 0.2-0.4,

[0016] m is 0.001-0.2,

[0017] n is 4.6-5.6,

[0018] δ= y / m=1.0-1.4.

[0019] Further, the high-voltage-resistant permanent ferrite is of formula Ca 0.45 La 0.40Sr 0.15 Fe 2n- 0.303 Co 0.3 B 0.003 O 1+3n Ca 0.85-y La y Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 1+3n or Ca 0.45 La 0.40 Sr 0.15 Fe 10.27 Co 0.3 B 0.0 3O 16.9 express.

[0020] Furthermore, the high-pressure-resistance permanent magnet ferrite, when tested at room temperature (20°C), exhibits Br ≥ 4.4 kGs and coercivity H. CB ≥4.0kOe, intrinsic coercivity H CJ ≥4.9kOe, H k / H CJ ≥85%, overall performance M*≥6.03; simulated installation circuit test, AC1500V, duration 1s, permanent magnet ferrite element leakage current ≤3mA; especially, AC1800V, duration 1s, permanent magnet ferrite element leakage current ≤3mA.

[0021] The second objective of this technical solution is to provide a method for preparing a permanent magnet ferrite with high pressure resistance, specifically including the following steps:

[0022] S1 Ingredients and Mixing: Using Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The oxides or salts corresponding to each element are taken as starting materials and mixed evenly using wet or dry methods (generally for 2-4 hours, preferably 3-4 hours) to obtain a mixture.

[0023] Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3nIn the formula, R is at least one element selected from La, Nd and Pr, and must contain La; M is at least one element selected from Co, Zn, Ni, Mn and Cu, and must contain Co; x, y, z, m and n respectively represent the addition ratio of each metal oxide, x is 0.001-0.1, y is 0.2-0.5, 1-m-y is 0.3-0.5, z is 0.2-0.4, m is 0.001-0.2, and n is 4.6-5.6, δ= y / m = 1.0-1.4;

[0024] In addition, a part of each starting material can be added in the fine crushing stage after pre-sintering.

[0025] In addition, a part of each starting material can be added in the fine crushing stage after pre-sintering.

[0026] S2 pre-sintering: the mixture obtained in step S1 is kept in air for 1-2 h, preferably 1.5-2 h, at T 预烧 = T0- (6.3-n-0.5y) x 50℃, to obtain pre-sintered material;

[0027] wherein T0 is 1280-1310℃, and preferably T0 is 1300-1310℃.

[0028] S3 crushing: the pre-sintered material obtained in step S2 is coarsely crushed by dry method to an average particle size of 2-4 μm, preferably 1-2 μm; then, an additive (such as dispersant, calcium gluconate, sorbitol, etc.) is added; and the material is finely crushed by wet method to an average particle size of 0.7-1.2 μm, preferably 0.8-1.0 μm, to obtain crushed material;

[0029] In the fine crushing process, the remaining part of the starting material described above can be added, and a known dispersant such as calcium gluconate, sorbitol, etc. can be added to improve the orientation degree of the slurry.

[0030] S4 forming: the crushed material obtained in step S3 is drained by a dehydrator or natural sedimentation combined with siphon drainage, and the water content is controlled to 30-45%, preferably 35-42%; then, the material is formed under the action of a magnetic field, and the magnetic field for magnetization during forming is 10000 Oe or more, preferably 12000 Oe or more, to obtain a formed body (also referred to as a formed compact);

[0031] In the process, the control of the moisture content of the crushed material mainly ensures the performance index of the subsequent obtained product, for example, if the moisture content of the crushed material is too low, the molding orientation is poor, and the molded compact is prone to layer cracking; if the moisture content of the crushed material is too high, the side surface and the end surface of the molded compact are prone to cracking, and the magnetic field during molding is too low, and the orientation of the molded body is insufficient, etc.

[0032] S5 sintering: the molded body obtained in step S4 is heated at 200-400 DEG C for 2-4 h to fully remove the moisture and organic matter in the molded body, so as to: in the temperature rising stage above 400 DEG C, the unremoved moisture is discharged from the surface of the molded compact, resulting in cracking of the product; then, the oxygen content between 1100 DEG C and the highest sintering temperature is controlled to be 18-21%, and the sintering is carried out in air at the highest sintering temperature of 1180-1240 DEG C for 0.1-4 h, so that the magnet with good magnetic properties, magnetic stability and pressure resistance can be obtained;

[0033] In the sintering process of the molded body at 1100-1180 DEG C, the sintering process of "slow heating and fast cooling" is adopted, the slow heating refers to the heating rate of 1-2 DEG C / min, and the fast cooling refers to the cooling rate of 5-10 DEG C / min, preferably 8-10 DEG C / min.

[0034] The beneficial technical effects brought by the technical scheme are:

[0035] The application optimizes the components of Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The optimization design of the components of Ca 3+ The introduction of appropriate B 预烧The sintering process is "slowly increasing temperature and quickly decreasing temperature" between 1100 DEG C and 1180 DEG C of the shaped compact, and the oxygen content of the atmosphere during sintering of the shaped compact is controlled to be 18-21% between 1100 DEG C and 1180 DEG C, compared with the ion substitution technology used in the production of traditional magnets, the microstructure, pressure resistance, magnetic performance, stability of magnetic parameters of the permanent magnet ferrite product under dynamic working conditions, etc. are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is the product physical map of the high pressure resistance permanent magnet ferrite obtained in the embodiment 1;

[0037] Figure 2 It is the magnetic parameter detection report of the high pressure resistance permanent magnet ferrite obtained in the embodiment 1;

[0038] Figure 3 It is the pressure resistance detection report of the high pressure resistance permanent magnet ferrite obtained in the embodiment 1;

[0039] Figure 4 It is the microstructure diagram of the high pressure resistance permanent magnet ferrite obtained in the embodiment 1;

[0040] Figure 5 It is the microstructure diagram of the sintered body obtained in the comparative example 2;

[0041] Figure 6 It is the magnetic parameter detection report of the high pressure resistance permanent magnet ferrite obtained in the embodiment 6. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0043] The existing permanent magnet ferrite cannot meet the current needs of electronic components and the like due to the deficiencies in performance (such as stability of magnetic parameters under dynamic working conditions, magnetic performance, pressure resistance), preparation process (such as formula, pre-sintering, sintering) and the like. Therefore, the present application provides a high pressure resistance permanent magnet ferrite and a preparation method thereof. The Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3nThe optimization design of the ingredients, especially the appropriate amount of B 3+ The introduction of Sr (BO2) 2, avoiding the adverse effects caused by the addition of SiO2 in the prior art (such as: external voltage or electrostatic voltage forms a loop through the micro motor bearing and the iron core, the permanent magnet oxide element, discharges the core chip of the controller core component, and breaks the chip); and the pre-sintering temperature (T 预烧 = T0- (6.3-n-0.5y) x 50℃) optimization design, the sintering process of the shaped green body “slow heating, fast cooling”, and the sintering technology combined with the atmosphere control of the oxygen content of the shaped green body during sintering between 1100℃ and 1180℃, which is controlled at 18-21%, compared with the ion substitution technology used in the production of traditional magnets, the microstructure, pressure resistance, magnetic performance, and stability of the magnetic parameters of the permanent magnet oxide product under dynamic working conditions have been significantly improved. Further, the following examples are used to illustrate.

[0044] In addition, in the following examples, the CS9914AX voltage withstand tester (Nanjing Changsheng Instrument Co., Ltd.) is used for the performance detection of the high pressure resistance permanent magnet oxide, which involves the following settings: AC 1500V, duration 1s, analog installed loop, detect the leakage current of the sample, the larger the leakage current, the worse the pressure resistance of the product;

[0045] And the NIM-2000F permanent magnet oxide measuring instrument (China Institute of Metrology) is used to detect the magnetic performance of the product, which uses CGS units, that is, the residual magnetic induction Br / Gs, the coercive force H CB / Oe, the intrinsic coercive force H CJ / Oe; H K is the demagnetizing field strength value corresponding to B i (J) = 0.9 B r on the J-H intrinsic demagnetization curve, the squareness of the demagnetization curve is calculated by H k / H CJ , which represents the stability of the magnetic parameters of the magnet under dynamic working conditions; the comprehensive performance of the material is compared by M * value, where M * = B r + (1 / 3) H CJ ;

[0046] The high pressure resistance permanent magnet oxide prepared by crushing the ferrite element sample, adding oxalic acid and concentrated phosphoric acid to heat and dissolve, then adding deionized water, and titrating with K2Cr2O7 solution, monitoring the Fe 2+ content of the ferrite sintered magnet.

[0047] Example 1

[0048] The raw materials used in the embodiment are as follows:

[0049] Fe2O3 powder with mass fraction of 99% or more, wherein the mass fraction of SiO2 is ≤0.015%, the mass fraction of its chloride (Cl - ) is ≤0.15%, and the average particle size of the Fe2O3 powder is 0.90 μm;

[0050] SrCO3 powder with mass fraction of 98% or more and average particle size of 1.5 μm;

[0051] CaCO3 powder with mass fraction of 98.5% or more and average particle size of 2.5 μm;

[0052] La2O3 powder with mass fraction of 99% or more and average particle size of 2.5 μm;

[0053] CoO powder with Co content of 72% or more and average particle size of 2.7 μm;

[0054] Sr(BO2)2 powder with mass fraction of 99% or more and average particle size of 1 μm

[0055] Then, the high-pressure-resistant permanent ferrite is prepared by the following steps:

[0056] S1: mixing: the raw materials are mixed according to the mass ratio of Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The addition amount of each main starting material is calculated, wherein M is Co, R is La, x=0.03, y=0.4, z=0.3, m=0.04, n=5.3, m=0.15, and the corresponding oxides or salts of each element are weighed as starting materials. 0.6% of CaCO3 and 0.25% of Sr(BO2)2 are added in the crushing process after pre-sintering in step S3;

[0057] The mixture is obtained by mixing the raw materials in water for 3 hours by wet method;

[0058] S2: pre-sintering: the mixture obtained in step S1 is pre-sintered in air at T 预烧 =1300-(6.3-5.3-0.5*0.4)×50=1260℃ for 2 hours, and a pre-sintered material is obtained;

[0059] S3 crushing: the pre-sintered material obtained in step S2 is coarsely broken by dry method to an average particle size of 2.5 μm, and 0.5% by mass of dispersant-sorbitol, 0.6% by mass of CaCO3 and 0.25% by mass of Sr(BO2)2 are added;

[0060] The crushing material is obtained by fine crushing to an average particle size of 0.8 μm in a wet grinding manner with water as the medium;

[0061] S4 forming: the slurry of the crushing material obtained in step S3 is drained by a dehydrator or natural sedimentation combined with siphon method, and the water content is controlled to be 36%, and then the slurry is formed under the action of a magnetic field, and the magnetizing magnetic field during the forming is 12000 Oe, and a formed body is obtained;

[0062] S5 sintering: the formed body obtained in step S4 is kept at 200-400 ℃ for 2 h to remove water and organic matter in the formed body, and the oxygen content between 1100 ℃ and the highest sintering temperature is controlled to be 20%, and the sintering is performed in air at the highest sintering temperature of 1200 ℃ for 2 h, wherein, in the sintering process, a slow heating and fast cooling sintering process is adopted during the sintering process at 1100-1180 ℃, that is, the slow heating refers to a heating rate of 2 ℃ / min, and the fast cooling refers to a cooling rate of 8 ℃ / min, and a sintered magnet is obtained, and the finished product obtained after grinding is shown in Figure 1 ; then, the CS9914AX voltage withstand tester is used for testing (AC 1500V, duration 1 s, simulation of installed loop, detection of leakage current of the sample); in addition, the upper and lower surfaces of the obtained sintered magnet are ground flat, and fine grinding is performed by using a 135-mesh fine grinding wheel, and then the NIM-2000F permanent magnet ferrite measuring instrument is used to test the magnetic properties of the product, wherein the magnetic properties and leakage current of the sintered magnet product are shown in Table 9, Figure 2 , and the voltage withstand test results are shown in Figure 3 ;

[0063] In addition, after the surface of the sintered magnet sample is treated by using 30% hydrofluoric acid, the JEOL JSM-6490LV scanning electron microscope (SEM) is used to observe the cross-sectional morphology of the sample, and the microstructure of the sintered magnet is shown in Figure 4 , and it is concluded that the SEM analysis of the cross section of the sintered magnet shows that the crystal structure is closely arranged, and the grain size is relatively uniform.

[0064] Example 2

[0065] In this example, Ca 0.45 La 0.40 Sr 0.15 Fe2n-0.33 Co 0.3 B 0.03 O 3n+1 Calculate the addition amount of each main starting material, where n = 4.6-5.6; the pre-firing temperature is based on T. 预烧 =1300-(6.3-n-0.5*0.4)×50℃ control, the rest is the same as in Example 1.

[0066] Different permanent magnet ferrites with different properties were obtained when n was different, as shown in Table 1 below.

[0067]

[0068] Example 3

[0069] This embodiment is based on Ca 0.45 La 0.40 Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 3n+1 Calculate the addition amount of each main starting material, where n = 4.6-5.6; the pre-firing temperature is based on T. 预烧 =1290-(6.3-n-0.5*0.4)×50℃ control, the rest is the same as in Example 1.

[0070] Different permanent magnet ferrites with different properties were obtained when n was different, as shown in Table 2 below.

[0071]

[0072] As shown in Table 1-2 above, with n=4.6-5.6, permanent magnet ferrites with good magnetic properties can be obtained within a relatively wide pre-firing temperature range. Among them, H... k / H CJ Above 85%, the leakage current is less than 0.3mA; and, the larger n is, the more Fe in the permanent magnet ferrite... 2+ The content increased slightly.

[0073] In the M-type magnetoplumbium structure, a considerable number of ion vacancies can be allowed to exist, Fe 3+ If ions are partially replaced by divalent cations, oxygen ion vacancies will appear accordingly. Appropriately low n components still exist in a single phase, which creates conditions for iron-deficient formulations and additives to improve performance. When n is slightly less than 6, Fe will appear in the unit cell. 3+ and O 2- The introduction of vacancies promotes ion transport during the reaction, which is beneficial to the solid-phase reaction during sintering. As a result, the shrinkage rate increases, the density rises, and the magnetic properties are improved.

[0074] Furthermore, the leakage current of the sintered magnet gradually increases with the increase of n. This is because the magnetic ions within the ferrite cell of the permanent magnet are Fe. 3+ , respectively located in 2 a 2 b 12 k 4 f 1, 4 f 2, Fe 3+ With the O around it 2- This will form sites of different shapes, 2 a 4 f 2, 12 k Crystal sites are octahedral sites, 4 f 1. The crystal site is a tetrahedral site, 2. b The crystal sites are triangular bipyramidal sites. Electron transport in M-type permanent magnet ferrite grains mainly depends on the Fe between tetrahedral and octahedral crystal sites. 3+ and Fe 2+ The charge transfer between Fe and n increases. 3+ and Fe 2+ The amount of charge transfer between them increases, the resistivity of the sintered body decreases, the leakage current increases, and the withstand voltage characteristics deteriorate.

[0075] Example 4

[0076] This embodiment is based on Ca 0.85-y La y Sr 0.15 Fe 10.27 Co 0.3 B 0.03 O 16.9 Calculate the addition amount of each main starting material, where y = 0.2 - 0.5, z = 0.3, and δ= y / z = 1.0-1.4, the rest is the same as in Example 1.

[0077] Different permanent magnet ferrites with different properties were obtained when y was of different values, as shown in Table 3 below.

[0078]

[0079] As shown in Table 3 above, with La 3+ Increasing the substitution amount y significantly improves the magnetic properties of the sintered magnet; however, when δ=y / z is less than 1, the magnetic properties decrease significantly. Excessive substitution, however, will lead to… B r A significant decline. In order to maintain electricity price balance, La 3+ After entering the crystal lattice, it will cause Fe 3+ The change in valence of ions is mainly due to the 2... a Fe at position 3+ Transformed into Fe 2+ Due to Fe2+ The magnetic moment ratio of ions to Fe 3+ The ions need to be small, so when La 3+ Excessive substitution can lead to magnetic dilution and spin tilting, causing M... S The decrease, (BH) MAX The decrease.

[0080] In addition, too much La 3+ The introduction of Fe caused 2+ The increase of Fe 2+ When present, the conductivity mechanism is mainly Fe 2+ ⇌Fe 3+ The diffusion of +e electrons results in different valence electrons conducting electricity at octahedral positions. This leads to low activation energy, increased conductivity, increased leakage current, and poorer breakdown voltage characteristics.

[0081] Example 5

[0082] This embodiment is based on Ca 0.45 La 0.4 Sr 0.15 Fe 10.57-z Co z B 0.03 O 16.9 Calculate the addition amount of each main starting material, where z = 0.1 - 0.5, y = 0.4, and δ= y / z = 1.0-1.4, the rest is the same as in Example 1.

[0083] Different permanent magnet ferrites with different z values ​​were obtained, as shown in Table 4 below.

[0084]

[0085] As shown in Table 4 above, with Co 2+ With the increase of the substitution amount z, the magnetic properties of the sintered magnet are significantly improved. When δ=y / z is less than 1, the magnetic energy product decreases significantly. k / H CJ The electromagnetic properties of the sintered magnet also decrease significantly when δ=y / z is too large. k / H CJ The decrease is due to Co 2+ Entering Octahedron 4 f 2 to enter tetrahedron 4 f The spatial steric hindrance of 1 is much smaller, therefore, it preferentially enters 4. f 2nd place, Co 2 + (3μB) replaces 4 fThe Fe (5μB) at the two subsites reduces the magnetic moment of the antiparallel ferrite ions, thereby increasing the difference between the spin-up and spin-down magnetic moments, resulting in increased saturation magnetization. M S Increase, this is important for materials B r The improvement is extremely beneficial. However, too much Co 2+ With the introduction of [the substance], impurity phases (non-M-type magnetolite phase) begin to appear, affecting the material's magnetic properties and H [other properties]. k / H CJ All began to decrease, with the excess Co not entering the crystal lattice 2+ with Fe 3+ Electron diffusion between them intensifies, leakage current increases, and withstand voltage characteristics gradually deteriorate. Additionally, when δ=y / z is too large, La... 3+ The amount was relatively excessive, resulting in Fe 2+ The increase of Fe 2+ When present, the conductivity mechanism is mainly Fe 2+ ⇌Fe 3+ The diffusion of +e electrons results in different valence electrons conducting electricity at octahedral positions. This leads to low activation energy, increased conductivity, increased leakage current, and poorer breakdown voltage characteristics.

[0086] Example 6

[0087] This embodiment is based on Ca 0.45 La 0.4 Sr 0.15 Fe 10.3-x Co 0.3 B x O 16.9 Calculate the amount of each main starting material to be added, where m = 0, 0.02, 0.04, 0.06, 0.08, 0.10, and the rest are the same as in Example 1.

[0088] Different permanent magnet ferrites with different properties were obtained when m was set to different values, as shown in Table 5 below. When x = 0.04, the magnetic properties of the product are as follows: Figure 6 As shown.

[0089]

[0090] As shown in Table 5 above, with B 3+ With the increase of substitution, H CJ Significantly increased, but B 3+ When too much is added, Br decreases significantly. That is, B... 3+ Too much or too little substitution is detrimental to improving pressure resistance.

[0091] Example 7

[0092] This embodiment is based on Ca 1-m-y Ry Sr m Fe 2n-z-x M z B x O 1+3n The addition amount of each main starting material is calculated, wherein M is Co, R is La, x = 0.03, y = 0.4, z = 0.3, m = 0.04, n = 5.3, and m = 0.15; in the sintering process, the oxygen content in the temperature range of 1100-1180°C is controlled, and the rest is the same as in Example 1.

[0093] The temperature rising rate, the temperature falling rate, and the permanent magnet ferrite with different properties obtained are shown in Table 6 as follows.

[0094]

[0095] As shown in Table 6 above, the performance of sample 4 related to the traditional process (i.e. the same temperature rising rate and temperature falling rate) is slightly lower than that of samples 1-3 related to the technical solution, the leakage current is obviously increased, and the voltage resistance characteristic is deteriorated. This is because the sintering magnet product crystallization and densification are rapidly carried out in the temperature range of 1100-1180°C, which easily causes discontinuous growth of the crystal grains, forms more encapsulated pores, and the “slow temperature rising and fast temperature falling” process is beneficial to the further ferritization and composition homogenization of the sintered magnet, and facilitates the escape of the gas in the crystal grains during the grain production process, which is helpful to the improvement of the microstructure of the product.

[0096] Example 8

[0097] In this example, Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The addition amount of each main starting material is calculated, wherein M is Co, R is La, x = 0.03, y = 0.4, z = 0.3, m = 0.04, n = 5.3, and m = 0.15; in the sintering process, the oxygen content in the temperature range of 1100-1180°C is controlled, and the rest is the same as in Example 1.

[0098] The permanent magnet ferrite with different properties is obtained when the oxygen content is different, and is shown in Table 7 as follows.

[0099]

[0100] From the above Table 7, it is shown that the control of oxygen content in the temperature range of 1100-1180°C where the crystallization and densification of the sintered magnet product rapidly proceed is advantageous to the improvement of the magnetic properties of the product, to the improvement of the H k / H CJ , to the reduction of the leakage current, and to the improvement of the voltage withstand characteristic. This is because the product releases oxygen during the reduction of the ferrite. The condition for the release of oxygen is that the oxygen partial pressure in the atmosphere surrounding the product is lower than the equilibrium oxygen pressure of the product, i.e. lower than the oxygen decomposition pressure of the product. According to this feature, if the oxygen partial pressure in the surrounding atmosphere is increased during sintering, which can be achieved by introducing air or oxygen into the furnace, the release of oxygen from the product is inhibited, and the reduction is prevented, and the Fe 2+ is oxidized to Fe 3+ . During high-temperature sintering, even if divalent iron ions are present in the product, as long as the oxygen partial pressure in the furnace is sufficient to make the oxygen partial pressure in the atmosphere surrounding the product higher than the oxygen partial pressure in the product, the Fe 2+ is oxidized to Fe 3+ .

[0101] Example 9

[0102] This example is for Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The amounts of the main starting materials were calculated, where M is Co, R is La, x=0.03, y=0.4, z=0.3, n=5.3, m=0, 0.1, 0.15, 0.2, 0.25. The obtained products were tested using a NIM-2000F permanent magnet ferrite measuring instrument and a CS9914AX voltage withstand tester (AC 1800V, duration 1s, simulated installed loop, leakage current of the sample was detected). The rest was the same as in Example 1.

[0103] Different properties of permanent magnet ferrite were obtained when the amount of Sr was different, as shown in the following Table 8.

[0104]

[0105] Table 8 shows that with the increase of the amount of Sr, Br, H CJ increased significantly, but too much or too little amount of Sr caused the Br, H CJ and the comprehensive magnetic properties to decrease. In addition, too much or too little amount of Sr caused the leakage current to increase significantly, the voltage withstand characteristic to deteriorate, and the H k / H CJdecrease. This is due to the low m, Ca 2+ content, part of the Ca 2+ mainly acts as flux, i.e. produces low melting point products (containing Fe 2+ salt) in the sintering process, resulting in excessive grain growth of the sintered magnet, producing abnormal growth grains. With the increase of m, SrO acts as a dense ferrite, which is due to the increase of liquid phase surrounding the ferrite periphery, but excessive SrO leads to excessive liquid phase, which is also easy to cause excessive grain growth of the sintered magnet, producing abnormal growth grains.

[0106] Comparative Example 1

[0107] This comparative example is a comparative example of Example 1, and the difference from Example 1 is that:

[0108] S1: batching and mixing: according to Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The amount of each main starting material is calculated, wherein M is Co, R is La, x = 0, y = 0.4, z = 0.3, m = 0.04, n = 5.3, m = 0.15, and the corresponding oxides or salts of each element are weighed as starting materials. The starting materials with a mass fraction of 0.6% CaCO3 are added in the crushing process after pre-sintering step S3;

[0109] S3: crushing: the pre-sintered material obtained in step S2 is coarsely broken by dry method to an average particle size of 2.5 μm, 0.5% dispersant-sorbitol, 0.6% CaCO3 and 0.10% silicon dioxide (purity 99.5%, average particle size 0.8 μm) are added.

[0110] Then, the preparation of permanent magnet ferrite is carried out. The performance of the prepared permanent magnet ferrite is detected, and the results are shown in Table 9.

[0111] Comparative Example 2

[0112] This comparative example is a comparative example of Example 1, and the difference from Example 1 is that:

[0113] S1: batching and mixing: according to Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3nThe addition amount of each main starting material was calculated, wherein M was Co, R was La, x = 0, y = 0.4, z = 0.3, m = 0.04, n = 5.3, m = 0.15, and the oxides or salts corresponding to each element were weighed as starting materials. The starting material with a mass ratio of 0.6% CaCO3 was added in the crushing process after pre-sintering in step S3;

[0114] S3 crushing: the pre-sintered material obtained in step S2 was coarsely broken by dry method to an average particle size of 2.5 μm, and a dispersant-sorbitol with a mass ratio of 0.5%, CaCO3 with a mass ratio of 0.6%, and silicon dioxide (purity 99.5%, average particle size 0.8 μm) with a mass ratio of 0.20% were added

[0115] Then, the preparation of permanent magnet ferrite was carried out. The prepared permanent magnet ferrite was subjected to performance detection, and the results are shown in Table 9 below, and the microstructure of the sintered body is shown in Figure 5 The magnet section SEM analysis showed that the crystal structure was closely arranged, but abnormal growth of local grains occurred.

[0116] Comparative Example 3

[0117] This comparative example is a comparative example of Example 1, and the difference from Example 1 is that:

[0118] S1 batching and mixing: Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n The addition amount of each main starting material was calculated, wherein M was Co, R was La, x = 0, y = 0.4, z = 0.3, m = 0.04, n = 5.3, m = 0.15, and the oxides or salts corresponding to each element were weighed as starting materials. The starting material with a mass ratio of 0.6% CaCO3 was added in the crushing process after pre-sintering in step S3;

[0119] S3 crushing: the pre-sintered material obtained in step S2 was coarsely broken by dry method to an average particle size of 2.5 μm, and a dispersant-sorbitol with a mass ratio of 0.5%, CaCO3 with a mass ratio of 0.6%, and silicon dioxide (purity 99.5%, average particle size 0.8 μm) with a mass ratio of 0.30% were added

[0120] Then, the preparation of permanent magnet ferrite was carried out. The prepared permanent magnet ferrite was subjected to performance detection, and the results are shown in Table 9 below.

[0121] As shown in Table 9 above, after adding silicon dioxide, the HCJ Further improvement was made, but Br slightly decreased, (BH)max, H k / H C , M * slightly decreased, and the leakage current was obviously higher than that of the permanent ferrite described in Example 1;

[0122] The electron transportation in the M-type permanent ferrite grain mainly depends on the charge transfer between Fe 3+ and Fe 2 + Table 9 shows the influence of the SiO2 addition amount on the magnetic properties of the sintered body. With the increase of the SiO2 addition amount, the material H CJ gradually increased, because SiO2 reacted with the excess SrO to become liquid phase above 1127°C, and SiO2 reacted with Fe2O3 to generate low-melting-point (1150°C) FeSiO3. These liquid phases can inhibit the grain growth, refine the grains, and the liquid phase flow promotes the densification of the sintered body, so the magnetic properties of the material are obviously improved. However, the appearance and flow of the liquid phase easily cause abnormal grain growth, and in addition, part of the Si 4+ enters the gap between the ferrite lattices, which will cause part of Fe 3+ to change into Fe 2+ , and finally form silicate non-magnetic phase, so the purity of M phase decreases, and the comprehensive magnetic properties decrease. Too much Si 4+ will also cause part of the ferrite to decompose, and the magnetic properties deteriorate sharply;

[0123] From Table 9, it can also be seen that with the increase of the SiO2 addition amount, the leakage current of the material rapidly increases, so the voltage resistance characteristics deteriorate sharply. This is because the liquid phase sintering, the porosity decreases, the density increases, the resistivity decreases, and the leakage current increases. On the other hand, with the increase of Si 4+ , part of Fe 3+ changes into Fe 2+ , and the electron diffusion conduction mechanism of Fe 2+ ⇌ Fe 3+ + e causes the leakage current to increase, and the voltage resistance characteristics to deteriorate.

[0124] Comparative Example 4

[0125] This comparative example is a comparative example of Example 1, and the difference from Example 1 is that:

[0126] Ca 0.45 La 0.40 Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 3n+1Calculate the addition amounts of each major starting material, where n=4.5 and n=5.7. The pre-firing temperature is based on T. 预烧 =1300-(6.3-n-0.5*0.4)×50℃ control.

[0127] Next, permanent magnet ferrite was prepared. The performance of the prepared permanent magnet ferrite was tested, and the results are shown in Table 10 below.

[0128]

[0129] As shown in Table 10 above, when n is less than 4.6 or greater than 5.6, Br is below 4400 Gs, and H... k / H CJ The value is below 85%, because both excessively high and low n values ​​will cause the sintering temperature range of the sintered body to narrow and the magnetic properties to decrease.

[0130] Comparative Example 5

[0131] This comparative example is a comparative example of Example 1, and the difference between it and Example 1 is that:

[0132] According to Ca 0.45 La 0.40 Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 3n+1 Calculate the amount of each main starting material to be added, where n = 4.6-5.6. The pre-firing temperature is controlled according to the traditional pre-firing temperature of 1290℃.

[0133] Next, permanent magnet ferrite was prepared. The performance of the prepared permanent magnet ferrite was tested, and the results are shown in Table 11 below.

[0134]

[0135] As shown in Table 11, in the traditional pre-sintering process, excessively high pre-sintering temperatures will lead to abnormal grain production in the sintered body after the pre-sintered material is broken, resulting in thinner grain boundaries, rapid expansion of pores, increased porosity, and the appearance of impurity phases (such as ω phase) in the sintered body. In some cases, the pre-sintered material may even partially melt, leading to Fe content in the sintered body. 2+ The increased content leads to a decrease in the magnetic parameters and resistivity of the sintered body, an increase in leakage current, and a deterioration in withstand voltage characteristics.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method of producing a high-voltage-resistant permanent magnet ferrite, characterized by, The method comprises the following steps: S1 ingredient and mixing: take the oxide or salt corresponding to each element as starting material, mix uniformly, and obtain a mixture; 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n Count, take the oxide or salt corresponding to each element as starting material, mix uniformly, and obtain a mixture; Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n wherein R is at least one element selected from the group consisting of La, Nd and Pr, and contains La; M is at least one element selected from the group consisting of Co, Zn, Ni, Mn and Cu, and contains Co; x, y, z, m and n respectively represent the addition ratio of each metal oxide, x is 0.001-0.1, y is 0.2-0.5, 1-m-y is 0.3-0.5, z is 0.2-0.4, m is 0.001-0.2, n is 4.6-5.6, δ= y / m = 1.0-1.4; S2 preheating: in T 预烧 = T0-(6.3-n-0.5y)×50℃, the mixture obtained in step S1 is kept in air for 1-2 hours to obtain pre-burned material; where T0 is 1280-1310℃; S3: crushing the pre-sintered material obtained in step S2 to obtain crushed material; S4: controlling the water content of the crushed material obtained in step S3 to be 30-45%, and then forming the crushed material under the action of a magnetic field to obtain a formed body; S5: controlling the oxygen content between 1100°C and the highest sintering temperature to be 18-21%, and sintering the formed body obtained in step S4 in air at the highest sintering temperature of 1180-1240°C for 0.1-4h to obtain a high-pressure-resistant permanent magnet ferrite; In the sintering process of the formed body at 1100-1180°C, a slow heating and fast cooling sintering process is adopted, the slow heating refers to a heating rate of 1-2°C / min, and the fast cooling refers to a cooling rate of 5-10°C / min.

2. The method of producing a high-voltage characteristic permanent magnet ferrite according to claim 1, characterized by, In step S1, the starting material comprises Fe2O3, and the average particle size of Fe2O3 is ≤2μm; the average particle size of the remaining starting material is ≤5μm.

3. The method of producing a high-voltage characteristic permanent magnet ferrite according to claim 1, characterized by, In step S3, the average particle size of the coarse crushing is 2-4μm, and the average particle size of the fine crushing is 0.7-1.2μm.

4. The method of producing a high-voltage characteristic permanent magnet ferrite according to claim 3, characterized by, In step S3, the additive is added after coarse crushing, and then fine crushing is performed.

5. The method of producing high coercivity permanent ferrite according to claim 1, wherein In step S4, the water content of the crushed material obtained in step S3 is controlled to be 30-45%, and then the crushed material is formed under the action of a magnetic field.

6. The method of producing a high-voltage characteristic permanent magnet ferrite according to claim 5, characterized by, In step S4, the magnetizing magnetic field during forming is 10000Oe or more.

7. The method of producing a high-voltage characteristic permanent magnet ferrite according to claim 6, characterized by, In step S5, the formed body obtained in step S4 is sintered after being kept at 200-400°C for 2-4h.

8. A high coercivity permanent magnetic ferrite produced by the method of any one of claims 1 to 7, characterized by, in the formula Ca 1-m-y R y Sr m Fe 2n-z-x M z B x O 1+3n denotes; R is at least one element selected from La, Nd and Pr, and must contain La; M is at least one element selected from Co, Zn, Ni, Mn and Cu, and must contain Co; x, y, z, m and n respectively represent the addition ratio of each metal oxide or salt; x is 0.001-0.1, y is 0.2-0.5, 1-m-y is 0.3-0.5, z is 0.2-0.4, m is 0.001-0.2, n is 4.6-5.6, δ= y / m = 1.0-1.

4.

9. The high-temperature-resistant permanent magnet ferrite according to claim 8, characterized in that, in the formula Ca 0.45 La 0.40 Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 1+3n , Ca 0.85-y La y Sr 0.15 Fe 2n-0.33 Co 0.3 B 0.03 O 1+3n or Ca 0.45 La 0.40 Sr 0.15 Fe 10.27 Co 0.3 B 0.03 O 16.9 .

10. The high voltage characteristic permanent magnet ferrite according to claim 8, characterized by, The high-voltage permanent magnet ferrite has Br≥4.4kGs, coercivity H CB ≥4.0kOe, intrinsic coercivity H CJ ≥4.9kOe, H k / H CJ ≥85%, comprehensive performance M*≥6.03; simulation of installed loop test, AC1500V, duration 1s, permanent magnet ferrite element leakage current≤3mA.

Images