Permanent magnetic ferrite with high thermal stability as well as preparation method and application of permanent magnetic ferrite

Abstract

The invention discloses a permanent magnetic ferrite with high thermal stability and a preparation method and application thereof, and belongs to the technical field of permanent magnetic ferrites.Praseodymium oxide and manganous-manganic oxide are added into a formula of the permanent magnetic ferrite, Br and Hcj indexes are high at normal temperature, and compared with the temperature coefficient, the absolute value of the temperature coefficient is smaller, and the change rate of performance along with temperature is smaller; as Mn < 2 + > and Mn < 3 + > ions occupy hexagonal crystal gaps in ferrite crystal lattices, the sensitivity coefficient of the magnetic moment to the temperature change is obviously lower than that of Fe < 3 + >, Mn < 2 + > and Mn < 3 + >, the confusion degree of magnetic domains can be inhibited, crystal lattice parameters can be finely adjusted, the stability of the crystal lattices can be improved, and the magnetocrystalline anisotropy constant is more gentle along with the change of the temperature; pr < 3 + > inhibits overgrowth of crystal grains, refines the crystal grains, adjusts magnetocrystalline anisotropy constants, enhances magnetic domain overturning resistance, improves Hcj, reduces internal pores and improves ferrite density.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet ferrite technology, and particularly relates to a permanent magnet ferrite with high thermal stability, its preparation method and application. Technical Background

[0002] With technological advancements and evolving application scenarios, permanent magnet ferrites not only need to possess high magnetic properties but also performance characteristics suitable for specific applications. In new energy vehicles, permanent magnet ferrites are primarily used in components such as drive motors, converters, and charging piles. The demand for permanent magnet ferrite materials is gradually increasing, and the requirements are becoming increasingly stringent, with the requirements for handling temperature variations being particularly crucial. While meeting the requirements for high saturation magnetization and high-frequency operation, it is also essential to ensure that the magnetic components do not crack due to expansion and contraction under repeated high and low temperature cycles. Therefore, improving the thermal shock resistance of magnetic materials plays a vital role in protecting components. However, the thermal shock resistance of existing permanent magnet ferrite technologies is insufficient to meet the demands of practical applications.

[0003] Chinese patent CN 118930242 A discloses a highly stable permanent magnet ferrite material and its preparation method. The method involves ball milling ferric oxide, silicon oxide, strontium carbonate, and water, followed by drying, pre-calcination, and crushing to obtain a pre-calcined material. This pre-calcined material is then ball-milled again with rare earth oxides to obtain a slurry. This slurry is oriented using a magnetic field, pressed into a green body, and sintered at a gradient temperature to obtain the permanent magnet ferrite. While this permanent magnet ferrite can improve overall magnetic properties, it lacks resistance to sudden drops in magnetic properties caused by temperature changes.

[0004] Therefore, researching a permanent magnet ferrite with high thermal stability, smaller performance variation with temperature, and better adaptability to temperature changes has become a problem that needs to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a permanent magnet ferrite with high thermal stability, its preparation method and application, so as to solve the problems mentioned in the background art or achieve better technical effects.

[0006] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention. This invention discloses a permanent magnet ferrite with high thermal stability, the composition of which, by mass percentage, is as follows:

[0007] The pre-burned material contains 92-98% strontium carbonate, 0.8-1.0% manganese tetroxide, 0.14-0.35% lanthanum oxide, 1.5-2.5% cobalt oxide, 0.6-1.2% bismuth oxide, 0.3-0.5% praseodymium oxide, and 0.1-0.2% silicon dioxide.

[0008] Furthermore, its composition, by mass percentage, is as follows:

[0009] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0010] Furthermore, the purity of manganese tetroxide is 99.8%, the purity of praseodymium oxide is 99.5%, the purity of cobalt oxide is 99.9%, the purity of strontium carbonate is 99.5%, and the purity of bismuth oxide is 99.5%.

[0011] Furthermore, the pre-calcined material contains 4% to 6% praseodymium oxide and 1.0% to 1.8% manganese tetroxide.

[0012] Furthermore, the formulation of the pre-fired material, by mass percentage, comprises the following components:

[0013] Iron oxide 82%~88%; manganese tetroxide 1.0%~1.8%; calcium carbonate 2%~3.8%; praseodymium oxide 4%~6.0%; cobalt oxide 1.5%~2.5%; strontium carbonate 0.5%~1.0%; boric acid 0.3%~0.5%; bismuth oxide 1%~3%.

[0014] Furthermore, the formulation of the pre-fired material, by mass percentage, comprises the following components:

[0015] Iron oxide 86%; manganese tetroxide 1.2%; calcium carbonate 2.6%; praseodymium oxide 5%; cobalt oxide 2.4%; strontium carbonate 0.5%; boric acid 0.3%; bismuth oxide 2%.

[0016] Furthermore, the preparation method of any of the above-mentioned high thermal stability permanent magnet ferrites includes the following steps:

[0017] S1: Add each component of the pre-burned material formula and deionized water to a sand mill, and obtain a mixed slurry with a particle size of 1.25 mm and a moisture content of 65~75% by wet sand milling;

[0018] S2: The slurry in S1 is dried to obtain a slurry with a moisture content of 30~35%. The slurry is then added to a pelletizer to form small balls with a radius of 3mm.

[0019] S3: Place the small balls from S2 into a muffle furnace for one sintering, cool with the furnace, and crush to obtain pre-burned material;

[0020] S4: The pre-calcined material obtained in S3 is subjected to wet ball milling with other auxiliary materials to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0021] S5: The slurry in S4 is dehydrated and pressed into shape to obtain a green body with a moisture content of 15%. The green body is then transferred to a pusher kiln for secondary sintering and cooled with the furnace to obtain a permanent magnet ferrite with high thermal stability.

[0022] Furthermore, in S3, the temperature of the first sintering is 1050~1100℃, and the holding sintering time is 2.5~3h.

[0023] Furthermore, in S5, the temperature of the secondary sintering is 1200~1220℃, and the sintering time is 45~60min.

[0024] Furthermore, the application of any of the aforementioned high thermal stability permanent magnet ferrites in new energy vehicle motors.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The formulation of this invention includes praseodymium oxide and manganese tetroxide. At room temperature, the Br and Hcj indices are relatively high. Comparing their temperature coefficients, it is found that the absolute value of the temperature coefficient is smaller, the rate of change of performance with temperature is smaller, and it is more adaptable to temperature changes because Mn 2 + Mn 3+ Ions occupy hexagonal interstitial spaces in the ferrite lattice, and their magnetic moments are significantly less sensitive to temperature changes than those of Fe. 3+ Mn 2+ Mn 3+ It can suppress the disorder of magnetic domains, fine-tune lattice parameters, improve lattice stability, make the change of magnetocrystalline anisotropy constant with temperature more gradual, and reduce the influence of temperature coefficient on ferrite properties. 3+ It inhibits excessive grain growth, refines grains, adjusts the magnetocrystalline anisotropy constant, enhances the resistance to magnetic domain flipping, increases Hcj, reduces internal porosity, and increases ferrite density.

[0027] (2) In the sintering process of this invention, it is only necessary to raise the temperature to 1050~1100℃ for heat preservation sintering. The normal sintering temperature is above 1300℃, while 1100℃ is liquid phase sintering. The melting point of bismuth oxide in the formula is relatively low, about 824℃, which is lower than the sintering temperature of ferrite. Therefore, during sintering, bismuth oxide will melt into liquid phase first. Liquid phase can fill the space gap between solid particles, accelerate the atomic diffusion on the particle surface, promote the occurrence of solid phase reaction, improve the rate and uniformity of solid phase reaction, reduce the sintering temperature of ferrite, and accelerate the densification of ferrite. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the ferrite prepared in Example 1 of the present invention. Detailed Implementation

[0029] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0030] Unless otherwise specified, the raw materials or reagents used in the following examples and comparative examples are commercially available products or products prepared using conventional techniques.

[0031] Among them, the purity of iron oxide is 99.5%, the purity of manganese tetroxide is 99.8%, the purity of calcium carbonate is 99%, the purity of praseodymium oxide is 99.5%, the purity of cobalt oxide is 99.9%, the purity of strontium carbonate is 99.5%, the purity of boric acid is 99%, and the purity of bismuth oxide is 99.5%.

[0032] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0033] Fe2O3 82%~88%; Mn3O4 1.0%~1.8%; CaCO3 2%~3.8%:; Pr2O3 4%~6.0%; Co2O3 1.5%~2.5%; SrCO3 0.5%~1.0%; H3BO3 0.3%~0.5%; Bi2O3 1%~3%;

[0034] The preparation process of this pre-fired material is as follows:

[0035] (1) Add the above components and deionized water to a sand mill in the ratio m(material):m(ball):m(water) = 1:8:2 and wet sand mill at a speed of 450 r / min for 2 h to obtain a mixed slurry with a particle size of 1.25 mm and a moisture content of 65~75%.

[0036] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 30~35%;

[0037] (3) Add the slurry obtained in step (2) to the pelletizer. The disc tilt angle is 45°~47° and the circumferential speed is 1.8~2.0m / s. Make small balls with a radius of 3mm. Place the small balls in the muffle furnace and heat them to 1050~1100℃. Hold them for sintering for 2.5~3h and then cool them to room temperature with the furnace. The normal sintering temperature is above 1300℃, while 1100℃ is liquid phase sintering. The melting point of bismuth oxide in the formula is low, about 824℃, which is lower than the sintering temperature of ferrite. Therefore, bismuth oxide will melt into liquid phase first during sintering. The liquid phase can fill the space gap between solid particles, accelerate the atomic diffusion on the particle surface, promote the occurrence of solid phase reaction, improve the rate and uniformity of solid phase reaction, reduce the sintering temperature of ferrite, and accelerate the compactness of ferrite.

[0038] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0039] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0040] The pre-burned feedstock contains 92-98% strontium carbonate, 0.8-1.0% manganese tetroxide, 0.14-0.35% lanthanum oxide, 1.5-2.5% cobalt oxide, 0.6-1.2% bismuth oxide, 0.3-0.5% praseodymium oxide, and 0.1-0.2% silicon dioxide.

[0041] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0042] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2. The ball milling media is bearing steel balls, and a slurry with a particle size of 0.65~0.8mm and a moisture content of 65~75% is obtained.

[0043] (2) The slurry obtained in step (1) is dehydrated and pressed into shape. The moisture content of the green body is controlled to be 12~20%. Then the green body is transferred to the pusher kiln and sintered at 1200~1220℃ for 45~60min. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0044] Example 1

[0045] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0046] Fe2O3 86%; Mn3O4 1.2%; CaCO3 2.6%:; Pr2O3 5%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 2%;

[0047] The preparation process of this pre-fired material is as follows:

[0048] (1) Add the above components and deionized water to a sand mill in the ratio m(material):m(ball):m(water) = 1:8:2, and wet sand mill at a speed of 450 r / min for 2 h to obtain a mixed slurry with a particle size of 1.25 mm and a water content of 70%.

[0049] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0050] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0051] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0052] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0053] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0054] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0055] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0056] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to a pusher kiln and sintered at 1210℃ for 48 min. After that, it is cooled to room temperature with the furnace to obtain a permanent magnet ferrite with high thermal stability. The microstructure is as follows: Figure 1 As shown.

[0057] Example 2

[0058] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0059] Fe2O388%; Mn3O41.0%; CaCO3 2.6%:; Pr2O3 4%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 1.2%;

[0060] The preparation process of this pre-fired material is as follows:

[0061] (1) Add the above components and deionized water to a sand mill in the ratio (m (material):m (ball):m (water) = 1:8:2) and wet sand mill at a speed of 450 r / min for 2 h to obtain a mixed slurry with a particle size of 1.25 mm and a water content of 70%.

[0062] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0063] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0064] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0065] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0066] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0067] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0068] (1) The pre-fired material and each auxiliary material are mixed and wet ball-milled in a ratio of m(material):m(ball):m(water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of (35%).

[0069] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled to be (15%). Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0070] Example 3

[0071] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0072] Fe2O3 83.4%; Mn3O4 1.8%; CaCO3 2.6%:; Pr2O3 6%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 3%;

[0073] The preparation process of this pre-fired material is as follows:

[0074] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a water content of 70%.

[0075] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and dried at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0076] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0077] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0078] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0079] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0080] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0081] (1) The pre-fired material and each auxiliary material are mixed and wet ball-milled in a ratio of m(material):m(ball):m(water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of (35%).

[0082] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled to be (15%). Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0083] Example 4

[0084] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0085] Fe2O386%; Mn3O41.2%; CaCO3 2.6%:; Pr2O3 5%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 2%;

[0086] The preparation process of this pre-fired material is as follows:

[0087] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0088] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0089] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0090] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0091] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0092] The pre-burned feedstock consists of 95.75% strontium carbonate, 1.0% manganese tetroxide, 0.25% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.3% praseodymium oxide, and 0.1% silicon dioxide.

[0093] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0094] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0095] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0096] Example 5

[0097] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0098] Fe2O386%; Mn3O41.2%; CaCO3 2.6%:; Pr2O3 5%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 2%;

[0099] The preparation process of this pre-fired material is as follows:

[0100] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0101] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0102] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0103] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0104] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0105] The pre-burned feedstock contains 94.55% strontium carbonate, 1.0% manganese tetroxide, 0.35% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.0% praseodymium oxide, and 0.1% silicon dioxide.

[0106] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0107] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0108] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0109] Comparative Example 1

[0110] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0111] Fe2O388%; Mn3O41.2%; CaCO3 2.6%:; Pr2O3 5%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%;;

[0112] The preparation process of this pre-fired material is as follows:

[0113] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0114] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0115] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1300°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0116] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0117] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0118] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0119] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0120] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0121] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0122] Comparative Example 2

[0123] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0124] Fe2O3 87.2%; CaCO3 2.6%: Co2O3 2.4%; SrCO3 5.5%; H3BO3 0.3%; Bi2O3 2%;

[0125] The preparation process of this pre-fired material is as follows:

[0126] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0127] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%;

[0128] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0129] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0130] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0131] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0132] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0133] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0134] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0135] Comparative Example 3

[0136] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following composition by weight percentage: Fe2O3 87.9%; Mn3O4 0.8%; CaCO3 2.6%; Pr2O3 3.5%; Co2O3 2.4%; SrCO3 0.5%; H3BO3 0.3%; Bi2O3 2%.

[0137] The preparation process of this pre-fired material is as follows:

[0138] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0139] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0140] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0141] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0142] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0143] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0144] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0145] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0146] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0147] Comparative Example 4

[0148] A pre-sintered material for a high thermal stability permanent magnet ferrite, with the following component formulation by weight percentage:

[0149] Fe2O3 83.7%; Mn3O4 2.0%; CaCO3 2.6%:; Pr2O3 6.5%; Co2O3 2.4%; SrCO3 0.5%; H3BO30.3%; Bi2O3 2%;

[0150] The preparation process of this pre-fired material is as follows:

[0151] (1) Add the above components and deionized water to a sand mill in a ratio of m(material):m(ball):m(water) = 1:8:2 and wet-mill at a speed of 450r / min for 2h to obtain a mixed slurry with a particle size of 1.25mm and a moisture content of 70%.

[0152] (2) The slurry obtained in step (1) is placed in a forced-air drying oven and kept at 120°C for 4 hours to obtain a slurry with a moisture content of 35%.

[0153] (3) Add the slurry obtained in step (2) to the pelletizer, with the disc tilt angle at 47° and the circumferential speed at 2.0 m / s, to produce small balls with a radius of 3 mm. Place the small balls in a muffle furnace, heat them to 1100°C, hold them at the temperature for 2.5 h, and then cool them to room temperature with the furnace.

[0154] (4) The small balls sintered in step (3) are crushed to obtain pre-fired powder with a particle size of 2~3.5mm.

[0155] A high thermal stability permanent magnet ferrite, comprising the pre-sintered material prepared above and other auxiliary materials, with the following formula by weight percentage:

[0156] The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

[0157] The preparation method of the above-mentioned high thermal stability permanent magnet ferrite includes the following steps:

[0158] (1) The pre-burned material and each auxiliary material are mixed and wet ball milled in a ratio of m (material): m (ball): m (water) = 1:6:2 to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%;

[0159] (2) The slurry obtained in step (1) is dehydrated and pressed into shape, and the moisture content of the green body is controlled at 15%. Then the green body is transferred to the pusher kiln and sintered at 1210℃ for 48 minutes. After that, it is cooled to room temperature with the furnace to obtain permanent magnet ferrite with high thermal stability.

[0160] The remanence B of the high thermal stability permanent magnet ferrites prepared in Examples 1-5 and Comparative Examples 1-4 was measured at different temperatures. r (mT) and intrinsic coercivity H cj (kA / m), using NIM-62000 equipment; and calculating the remanence B in the temperature range of 25~150℃ (taking 25℃ and 150℃ as examples). r (mT) and intrinsic coercivity H cj Temperature coefficient (kA / m);

[0161] Residual magnetism B r Temperature coefficient of (mT) (% / ℃) = [remanence B at 150℃] r Remanence B at (mT)-25℃ r (mT) / Remanence B at 25℃ r (mT) / (150℃-25℃)×100%;

[0162] Innate coercivity H cj Temperature coefficient (kA / m) (% / ℃) = [Intrinsic coercivity H at 150℃] cj Intrinsic coercivity H at -25℃ (kA / m) cj [(kA / m)] / Intrinsic coercivity H at 25℃ cj (kA / m) / (150℃-25℃)×100%;

[0163] The test results are shown in Tables 1 and 2 below.

[0164] Table 1. Permanent magnet ferrites with high thermal stability prepared in Examples 1-5 and Comparative Examples 1-4

[0165] Magnetic properties at 25℃ and 150℃

[0166] Table 2 Examples 1-5 and Comparative Examples 1-4

[0167] The temperature coefficient of the prepared high thermal stability permanent magnet ferrite

[0168]

[0169] Analysis of the data in Tables 1 and 2 shows that, compared with Comparative Example 1, Examples 1-5 have the best performance. The remanence and intrinsic coercivity of Examples 1-5 are significantly higher than those of Comparative Example 1, and the absolute value of the temperature coefficient is significantly smaller than that of Comparative Example 1. This is because the formulation of this invention includes a specific amount of bismuth oxide, which melts into a liquid phase during sintering. The liquid phase can fill the spatial gaps between solid particles, accelerate atomic diffusion on the particle surface, promote the occurrence of solid-phase reactions, improve the rate and uniformity of solid-phase reactions, reduce the sintering temperature of ferrite, accelerate the compactness of ferrite, improve lattice stability, and thus improve its temperature coefficient.

[0170] A comparison of Examples 1-5 with Comparative Example 2 reveals that when praseodymium oxide and manganese tetroxide are added to the formulation, Br and Hcj are significantly higher at room temperature. Furthermore, comparing their temperature coefficients shows that the absolute value of the temperature coefficient is smaller, indicating a lower rate of change in performance with temperature, making it more adaptable to temperature variations. This is because Mn... 2+ Mn 3+ Ions occupy hexagonal interstitial spaces in the ferrite lattice, and their magnetic moments are significantly less sensitive to temperature changes than those of Fe. 3+ Mn 2+ Mn 3+ It can suppress the disorder of magnetic domains, fine-tune lattice parameters, improve lattice stability, make the change of magnetocrystalline anisotropy constant with temperature more gradual, and reduce the influence of temperature coefficient on ferrite properties. 3+ It inhibits excessive grain growth, refines grains, adjusts the magnetocrystalline anisotropy constant, enhances the resistance to magnetic domain flipping, increases Hcj, reduces internal porosity, and increases ferrite density.

[0171] A comparison of Example 1 with Comparative Examples 3-4 reveals that when praseodymium oxide and manganese tetroxide in the formulation exceed or fall below the specified range, the magnetic properties decrease, the performance of Br and Hcj at room temperature declines, and the absolute value of their temperature coefficients increases significantly. This is because when the amount of Mn and Pr added is too small, the uniformity of the ferrite reaction decreases, leading to a decline in its performance. The lack of synergistic effect between Mn and Pr and Co results in insufficient suppression of impurities α-Fe2O3, increasing the temperature coefficient. When the amount of Mn and Pr added is too large, unreacted Mn and Pr are present in the ferrite, forming a non-magnetic impurity phase. The degree of ordered arrangement of magnetic domains decreases, resulting in a decline in magnetic properties and an increase in the temperature coefficient.

Claims

1. A permanent magnet ferrite with high thermal stability, characterized in that, Its composition, by mass percentage, is as follows: The pre-burned material contains 92-98% strontium carbonate, 0.8-1.0% manganese tetroxide, 0.14-0.35% lanthanum oxide, 1.5-2.5% cobalt oxide, 0.6-1.2% bismuth oxide, 0.3-0.5% praseodymium oxide, and 0.1-0.2% silicon dioxide.

2. The high thermal stability permanent magnet ferrite according to claim 1, characterized in that, Its composition, by mass percentage, is as follows: The pre-burned feedstock contains 95.76% strontium carbonate, 0.8% manganese tetroxide, 0.14% lanthanum oxide, 1.5% cobalt oxide, 0.7% bismuth oxide, 0.5% praseodymium oxide, and 0.1% silicon dioxide.

3. The high thermal stability permanent magnet ferrite according to claim 1 or 2, characterized in that, The purity of manganese tetroxide is 99.8%, the purity of praseodymium oxide is 99.5%, the purity of cobalt oxide is 99.9%, the purity of strontium carbonate is 99.5%, and the purity of bismuth oxide is 99.5%.

4. The high thermal stability permanent magnet ferrite according to claim 1 or 2, characterized in that, The pre-burned material contains 4% to 6% praseodymium oxide and 1.0% to 1.8% manganese tetroxide.

5. The high thermal stability permanent magnet ferrite according to claim 4, characterized in that, The pre-fired material is formulated as follows, by mass percentage: Iron oxide 82%~88%; manganese tetroxide 1.0%~1.8%; calcium carbonate 2%~3.8%; praseodymium oxide 4%~6.0%; cobalt oxide 1.5%~2.5%; strontium carbonate 0.5%~1.0%; boric acid 0.3%~0.5%; bismuth oxide 1%~3%.

6. The high thermal stability permanent magnet ferrite according to claim 5, characterized in that, The pre-fired material is formulated as follows, by mass percentage: Iron oxide 86%; manganese tetroxide 1.2%; calcium carbonate 2.6%; praseodymium oxide 5%; cobalt oxide 2.4%; strontium carbonate 0.5%; boric acid 0.3%; bismuth oxide 2%.

7. A method for preparing a permanent magnet ferrite with high thermal stability as described in any one of claims 1 to 6, characterized in that, The steps are as follows: S1: Add each component of the pre-burned material formula and deionized water to a sand mill, and obtain a mixed slurry with a particle size of 1.25 mm and a moisture content of 65~75% by wet sand milling; S2: The slurry in S1 is dried to obtain a slurry with a moisture content of 30~35%. The slurry is then added to a pelletizer to form small balls with a radius of 3mm. S3: Place the small balls from S2 into a muffle furnace for one sintering, cool with the furnace, and crush to obtain pre-burned material; S4: The pre-calcined material obtained in S3 is subjected to wet ball milling with other auxiliary materials to obtain a slurry with a particle size of 0.65~0.8mm and a moisture content of 35%; S5: The slurry in S4 is dehydrated and pressed into shape to obtain a green body with a moisture content of 15%. The green body is then transferred to a pusher kiln for secondary sintering and cooled with the furnace to obtain a permanent magnet ferrite with high thermal stability.

8. The method for preparing the high thermal stability permanent magnet ferrite according to claim 7, characterized in that, In S3, the temperature of the first sintering is 1050~1100℃, and the holding sintering time is 2.5~3h.

9. The method for preparing the high thermal stability permanent magnet ferrite according to claim 7, characterized in that, In S5, the temperature of the secondary sintering is 1200~1220℃, and the sintering time is 45~60min.

10. The application of the high thermal stability permanent magnet ferrite as described in any one of claims 1 to 6 in the motor of a new energy vehicle.

Images