A NdFeB rotor magnet with high magnetic properties and high resistivity and its preparation and application

Abstract

The present invention discloses a NdFeB rotor magnet with high magnetic properties and high resistivity, and its preparation and application. The present invention mixes light rare earth low melting point alloy powder and non-rare earth oxide powder in a mass ratio of 1: (1-4), and then mixes with an organic binder to obtain a mixed diffusant; the mixed diffusant is applied to the surface of the NdFeB magnet and subjected to diffusion heat treatment to obtain the rotor magnet. The method of the present invention effectively improves the coercive force and resistivity, and has little negative impact on the magnetic energy product; the diffusant does not contain heavy rare earth elements Dy and Tb, which not only greatly reduces the material cost and improves the cost performance of the product, but also helps to promote the balanced utilization of rare earth resources.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of NdFeB permanent magnets, and in particular relates to a NdFeB rotor magnet with high magnetic properties and high resistivity, and preparation and application thereof. Background Art

[0002] NdFeB rare earth permanent magnet materials have been widely used in new energy and intelligent communications due to their excellent magnetic properties. During the service of NdFeB permanent magnet motors, NdFeB rotor magnets need to work stably under alternating electric fields. Sintered NdFeB without heavy rare earths has a low magnetic phase transition temperature (~312°C) and low resistivity. When eddy current heating is generated, it is easy to cause local temperature rise of the magnet and lead to local demagnetization. At present, the most commonly used solution is to increase the coercive force of the magnet and the Curie temperature of the main phase (2:14:1 phase) by adding or surface infiltration of heavy rare earth elements dysprosium (Dy) and terbium (Tb), thereby improving the thermal stability of the magnet. Among them, the surface infiltration technology has the advantage of less heavy rare earth usage, and can produce NdFeB magnets with high coercive force and high magnetic energy product. Another method is to add oxides and fluorides and other substances with high resistivity to the grain boundaries of the magnet to increase the overall resistivity of the magnet and reduce eddy current heating.

[0003] However, these two methods have the following problems: (1) Heavy rare earth elements are low in abundance and expensive, so the manufacturing cost of magnets with the addition or infiltration of Dy and Tb is high, and the product cost performance is low; (2) Although the addition of oxides and fluorides to the grain boundaries can increase the resistivity, a large amount of non-magnetic substances are introduced, causing the magnetic properties of the magnet to deteriorate, including coercivity and magnetic energy product. Therefore, the industry urgently needs a simple, efficient, and low-cost method to stably prepare commercial NdFeB magnets with high coercivity, high magnetic energy product, and high resistivity. Summary of the invention

[0004] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity.

[0005] Another object of the present invention is to provide a NdFeB rotor magnet with high magnetic properties and high resistivity obtained by the above method.

[0006] Another object of the present invention is to provide an application of the above-mentioned NdFeB rotor magnet with high magnetic properties and high resistivity.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity comprises the following steps:

[0009] (1) mixing light rare earth low melting point alloy powder and non-rare earth oxide powder uniformly to obtain a mixed powder;

[0010] (2) uniformly mixing the mixed powder and the organic binder to obtain an alloy mixed grain boundary diffusion agent;

[0011] (3) uniformly coating the mixed grain boundary diffusing agent on the surface of the NdFeB magnet and drying the mixture to obtain a magnet to be diffused;

[0012] (4) Placing the magnet to be diffused under vacuum or oxygen-free conditions for diffusion heat treatment to obtain a NdFeB rotor magnet.

[0013] Preferably, the mass ratio of the light rare earth low-melting point alloy powder to the non-rare earth oxide powder in step (1) is 1:(1-4); more preferably 1:(2-3).

[0014] Preferably, the light rare earth low melting point alloy powder in step (1) is at least one of LRE-M powders, wherein LRE is at least one of Pr, Nd, La and Ce, and M is at least one of Al, Cu, Ni, Co, Mg and Zn.

[0015] More preferably, the light rare earth low melting point alloy powder in step (1) is Pr 89.35 Al 4.89 Cu 5.76 Alloy, and La 87.68 Al 6.89 Cu 5.43 At least one alloy, all alloying elements are expressed in mass percentage.

[0016] Preferably, the non-rare earth oxide powder in step (1) is at least one of ZnO, MgO, Al2O3, Cr2O3 and Zr2O3.

[0017] More preferably, the non-rare earth oxide powder in step (1) is at least one of ZnO, MgO and Al2O3; most preferably, it is at least one of ZnO and Al2O3.

[0018] Preferably, the particle sizes of the light rare earth low-melting point alloy powder and the non-rare earth oxide powder in step (1) are both between 30 and 300 meshes; more preferably, between 50 and 200 meshes.

[0019] Preferably, the organic binder in step (2) is a composition of 35-60 wt% PVA glue, 37-64.5 wt% ethanol and 0.5-3 wt% polyethyleneimine.

[0020] Preferably, the mass ratio of the mixed powder to the organic binder in step (2) is 1:0.5-1.

[0021] Preferably, the NdFeB magnet in step (3) is a sintered, hot-pressed or hot-deformed NdFeB magnet, and the magnet is in the shape of a sheet or a tile.

[0022] Preferably, the thickness of the NdFeB magnet in step (3) is between 2 and 8 mm.

[0023] Preferably, the mixed grain boundary diffusion agent in step (3) is evenly coated on both surfaces of the NdFeB magnet.

[0024] Preferably, the drying temperature in step (3) is 50-70° C. and the drying time is 10-30 min.

[0025] Preferably, the coating amount in step (3) is based on the mixed powder in the mixed grain boundary diffusion agent accounting for 0.5-3.0% of the mass of the NdFeB magnet.

[0026] Preferably, the vacuum condition in step (4) is 5×10 -2 ~5×10 -3 Pa.

[0027] Preferably, the diffusion heat treatment in step (4) is divided into primary heat treatment and secondary heat treatment, the temperature of the primary heat treatment is 650-1000°C, and the insulation time is 1-20 hours; the temperature of the secondary heat treatment is 400-550°C, and the insulation time is 1-5 hours.

[0028] More preferably, the diffusion heat treatment in step (4) is divided into primary heat treatment and secondary heat treatment. For sintered magnets, the primary heat treatment temperature is 800-1000°C, and the heat preservation is 3-20 hours; the secondary heat treatment temperature is 400-550°C, and the heat preservation is 1-5 hours; for hot pressed or hot deformed magnets, the primary heat treatment temperature is 650-750°C, and the heat preservation is 1-8 hours; the secondary heat treatment temperature is 400-550°C, and the heat preservation is 1-5 hours.

[0029] The method is used to prepare a NdFeB rotor magnet with high magnetic properties and high resistivity.

[0030] The application of the above-mentioned high magnetic performance and high resistivity neodymium iron boron rotor magnet.

[0031] Preferably, the application is in new energy vehicle electric drive systems, wind power generator sets, servo motors and air-conditioning compressors.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The diffusant does not contain heavy rare earth elements Dy and Tb, which not only greatly reduces material costs and improves the cost performance of products, but also helps promote the balanced utilization of rare earth resources;

[0034] (2) The eddy current generated by the alternating current on the magnet surface has a certain skin depth; therefore, compared with the process of adding oxides and fluorides at the grain boundaries, the present method focuses on improving the resistivity of the magnet surface without strengthening the core of the magnet, and the amount of diffusant used is small; and under the premise of improving the resistivity of the magnet, it not only has a beneficial effect on the coercive force, but also has little negative impact on the magnetic energy product;

[0035] (3) Light rare earth low melting point alloy forms more liquid phase, providing a smoother diffusion channel for non-rare earth oxides to promote penetration, allowing non-rare earth oxides to diffuse more fully at the grain boundaries, increasing their diffusion depth, and allowing the grain boundary phase with high oxygen content to better wrap the hard magnetic grains; the diffusion of non-rare earth oxides increases the resistivity of the grain boundary phase, making the grains with low resistivity "connected in series" with the grain boundaries with high resistivity, thereby increasing the overall resistivity of the magnet;

[0036] (4) The light rare earth low melting point alloy promotes the formation of a continuous thin layer of grain boundary phase inside the magnet, so that the two hard magnetic grains are separated more effectively, which has a beneficial effect on the improvement of coercivity;

[0037] (5) Compared with fluoride-containing diffusants or additives, the diffusant of this method does not contain the F element, and the preparation method is environmentally friendly and in line with the environmental protection concept of green development. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a comparison chart of the magnetic properties of the mixed diffused magnet and the original magnet in Example 1.

[0039] Figure 2 This is the surface eddy current distribution diagram of the mixed diffused magnet and the original magnet in Example 1. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0041] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially.

[0042] The organic binder described in the embodiment of the present application is a composition of 60wt% PVA glue, 38wt% ethanol and 2wt% polyethyleneimine, and the mass ratio of the total mass of the mixed powder after the light rare earth low-melting point alloy powder and the non-rare earth oxide powder are mixed to the organic binder is 1:1.

[0043] Example 1

[0044] This embodiment uses a mixed diffusion agent of Pr-Al-Cu and ZnO to prepare a NdFeB magnet with high magnetic properties and high resistivity:

[0045] (1) Preparation of light rare earth-based Pr by arc melting 89.35 Al 4.89 Cu 5.76 (wt%) low melting point alloy ingot;

[0046] (2) remelting and spray-casting the alloy ingot obtained in step (1) to obtain a corresponding alloy strip;

[0047] (3) coarsely crushing the alloy strip obtained in step (2) to obtain powder passing through a 50-mesh sieve;

[0048] (4) mixing the alloy powder obtained in step (3) and ZnO powder sieved through a 100-mesh sieve in a mass ratio of 1:3, and then mixing with an organic binder to obtain a mixed diffusing agent;

[0049] (5) Using N54 sintered NdFeB tile magnets as diffusion substrates with a thickness of 3 mm; polishing them to a mirror surface, and then ultrasonically cleaning them in acetone and anhydrous ethanol for 15 minutes each;

[0050] (6) applying the mixed diffusing agent obtained in step (4) uniformly to the two surfaces of the magnet obtained in step (5), and drying in an oven at 50° C. to obtain a magnet to be diffused; wherein the amount of the mixed diffusing agent powder (i.e., the mixed powder of the alloy powder and the ZnO powder in step (4)) is controlled to be about 1 wt% of the mass of the magnet;

[0051] (7) The magnet to be diffused obtained in step (6) is placed in a vacuum heat treatment furnace, and the pressure in the furnace is reduced to 3×10 -2 Pa, and then two-stage heat treatment is carried out; the temperature of the first-stage heat treatment is 800℃, and the heat preservation is 6h, and the temperature of the second-stage heat treatment is 500℃, and the heat preservation is 3h; after the two-stage heat treatment is completed, the magnet is cooled and taken out from the furnace to obtain a diffused magnet.

[0052] In this embodiment, after diffusion of the mixed powder of Pr-Al-Cu and ZnO, the coercivity of the magnet increased from 1101 kA / m to 1545 kA / m, an increase of 40%, the remanence and magnetic energy product decreased slightly, and the magnet quality increased from N54 to 50H (see Figure 1 ). The resistivity of the magnet increased from 213μΩ·cm to 862μΩ·cm. After electromagnetic simulation, it was found that the surface diffusion of the Pr-Al-Cu and ZnO mixed powders can effectively reduce the eddy current density of the magnetic tile at the magnetic pole surface (see Figure 2), reducing local heating of the magnet and achieving the effect of reducing temperature rise. This example proves that the grain boundary diffusion of the mixed powder has a good diffusion effect in the thin rotor magnets commonly used in the industry at this stage. Under the same conditions, using a single Pr-Al-Cu alloy diffuser (the dosage is controlled at about 0.25wt% of the magnet mass), the coercive force of the magnet is increased from 1101kA / m to 1513kA / m, an increase of 37%, the remanence and magnetic energy product are slightly reduced, and the magnet quality is improved from N54 to 50H; the resistivity of the magnet is only slightly increased from 213μΩ·cm to 253μΩ·cm. Using only a ZnO diffuser (the dosage is controlled at about 0.75wt% of the magnet mass), the coercive force of the magnet is slightly reduced from 1101kA / m to 1065kA / m, and the resistivity of the magnet is only slightly increased from 213μΩ·cm to 471μΩ·cm. In contrast, the diffusion of Pr-Al-Cu and ZnO mixed powders has a more obvious effect on improving coercivity and resistivity.

[0053] Example 2

[0054] This embodiment uses a mixed diffusion agent of Pr-Al-Cu and Al2O3 to prepare a NdFeB magnet with high magnetic properties and high resistivity:

[0055] (1) Preparation of light rare earth-based Pr by arc melting 89.35 Al 4.89 Cu 5.76 (wt%) low melting point alloy ingot;

[0056] (2) remelting and spray-casting the alloy ingot obtained in step (1) to obtain a corresponding alloy strip;

[0057] (3) coarsely crushing the alloy strip obtained in step (2) to obtain powder passing through a 50-mesh sieve;

[0058] (4) mixing the alloy powder obtained in step (3) and Al2O3 powder sieved through a 200-mesh sieve in a mass ratio of 1:2, and then mixing with an organic binder to obtain a mixed diffusing agent;

[0059] (5) Using N54 sintered NdFeB tile magnets with a thickness of 5 mm as the diffusion substrate; polishing it to a mirror surface, and then ultrasonically cleaning it in acetone and anhydrous ethanol for 15 minutes each;

[0060] (6) applying the mixed diffusing agent obtained in step (4) uniformly to the two surfaces of the magnet obtained in step (5), and drying in an oven at 50° C. to obtain a magnet to be diffused; wherein the amount of the mixed diffusing agent powder (i.e., the mixed powder of the alloy powder and the Al2O3 powder in step (4)) is controlled to be about 1 wt% of the mass of the magnet;

[0061] (7) The magnet to be diffused obtained in step (6) is placed in a vacuum heat treatment furnace, and the pressure in the furnace is reduced to 3×10 -2 Pa, and then two-stage heat treatment is carried out; the temperature of the first heat treatment is 850℃, and the heat preservation is 10h, and the temperature of the second heat treatment is 550℃, and the heat preservation is 3h; after the two-stage heat treatment, the magnet is cooled and taken out from the furnace to obtain a diffused magnet.

[0062] In this embodiment, after the diffusion of the mixed powder of Pr-Al-Cu and Al2O3, the coercive force of the magnet is increased from 1101kA / m to 1378kA / m, an increase of 25%, the remanence and magnetic energy product are slightly reduced, and the magnet quality is improved from N54 to 52H. The resistivity of the magnet is increased from 213μΩ·cm to 957μΩ·cm. After electromagnetic simulation, it is found that the surface diffusion of the mixed powder of Pr-Al-Cu and Al2O3 can effectively reduce the eddy current density of the magnetic tile at the surface of the magnetic pole, reduce the local heating of the magnet, and play a role in reducing the temperature rise. This embodiment proves that the grain boundary diffusion of the mixed powder also has a better diffusion effect in rotor magnets with thicker thickness and larger size. Under the same conditions, using Pr-Al-Cu single alloy diffuser (the dosage is controlled at about 0.33wt% of the magnet mass), the coercive force of the magnet is increased from 1101kA / m to 1353kA / m, an increase of 23%, the remanence and magnetic energy product are slightly reduced, and the magnet quality is improved from N54 to 50H; the resistivity of the magnet is only slightly increased from 213μΩ·cm to 247μΩ·cm. Using only Al2O3 diffuser (the dosage is controlled at about 0.67wt% of the magnet mass), the coercive force of the magnet is reduced from 1101kA / m to 1033kA / m, and the resistivity of the magnet is only slightly increased from 213μΩ·cm to 342μΩ·cm. In comparison, the diffusion of Pr-Al-Cu and Al2O3 mixed powder has a more obvious effect on improving coercive force and resistivity.

[0063] Example 3

[0064] This embodiment uses La-Al-Cu and MgO mixed diffusion agents to prepare NdFeB magnets with high magnetic properties and high resistivity:

[0065] (1) Preparation of light rare earth-based La by arc melting 87.68 Al 6.89 Cu 5.43 (wt%) low melting point alloy ingot;

[0066] (2) remelting and spray-casting the alloy ingot obtained in step (1) to obtain a corresponding alloy strip;

[0067] (3) coarsely crushing the alloy strip obtained in step (2) to obtain powder passing through a 50-mesh sieve;

[0068] (4) mixing the alloy powder obtained in step (3) and MgO powder sieved through a 200-mesh sieve in a mass ratio of 1:4, and then mixing with an organic binder to obtain a mixed diffusing agent;

[0069] (5) Using N54 sintered NdFeB tile magnets as diffusion substrates with a thickness of 3 mm; polishing them to a mirror surface, and then ultrasonically cleaning them in acetone and anhydrous ethanol for 15 minutes each;

[0070] (6) applying the mixed diffusing agent obtained in step (4) uniformly to the two surfaces of the magnet obtained in step (5), and drying in an oven at 50° C. to obtain a magnet to be diffused; wherein the amount of the mixed diffusing agent powder (i.e., the mixed powder of the alloy powder and the MgO powder in step (4)) is controlled to be about 1 wt% of the mass of the magnet;

[0071] (7) The magnet to be diffused obtained in step (6) is placed in a vacuum heat treatment furnace, and the pressure in the furnace is reduced to 3×10 -2 Pa, and then two-stage heat treatment is carried out; the temperature of the first-stage heat treatment is 800℃, and the heat preservation is 6h, and the temperature of the second-stage heat treatment is 500℃, and the heat preservation is 3h; after the two-stage heat treatment is completed, the magnet is cooled and taken out from the furnace to obtain a diffused magnet.

[0072] In this embodiment, after diffusion of La-Al-Cu and MgO mixed powder, the coercive force of the magnet is increased from 1101kA / m to 1277kA / m, an increase of 16%, the remanence and magnetic energy product are slightly reduced, and the magnet quality is improved from N54 to 50M. The resistivity of the magnet is increased from 213μΩ·cm to 562μΩ·cm. Under the same conditions, using La-Al-Cu single alloy diffusion agent (the dosage is controlled at about 0.2wt% of the magnet mass), the coercive force of the magnet is increased from 1101kA / m to 1266kA / m, an increase of 15%, the remanence and magnetic energy product are slightly reduced, and the magnet quality is improved from N54 to 50M; the resistivity of the magnet is only slightly increased from 213μΩ·cm to 251μΩ·cm. When only MgO diffusion agent is used (the dosage is controlled at about 0.8wt% of the mass of the magnet), the coercivity of the magnet is slightly increased from 1101kA / m to 1124kA / m, and the resistivity of the magnet is only slightly increased from 213μΩ·cm to 372μΩ·cm. In contrast, the diffusion of La-Al-Cu and MgO mixed powder has a more obvious effect on improving the coercivity and resistivity. This example proves that the grain boundary diffusion of the mixed powder replaces Pr in the light rare earth low melting point alloy with La with higher abundance and lower price, which can still improve the coercivity and resistivity of the magnet and improve the service performance of the rotor magnet.

[0073] Comparative Example 1

[0074] This embodiment uses a mixed diffusion agent of Pr-Al-Cu and ZnO to prepare a NdFeB magnet with high magnetic properties and high resistivity:

[0075] (1) Preparation of light rare earth-based Pr by arc melting 89.35 Al 4.89 Cu 5.76 (wt%) low melting point alloy ingot;

[0076] (2) remelting and spray-casting the alloy ingot obtained in step (1) to obtain a corresponding alloy strip;

[0077] (3) coarsely crushing the alloy strip obtained in step (2) to obtain powder passing through a 50-mesh sieve;

[0078] (4) mixing the alloy powder obtained in step (3) and ZnO powder sieved through a 100-mesh sieve in a mass ratio of 1:0.8, and then mixing with an organic binder to obtain a mixed diffusing agent;

[0079] (5) Using N54 sintered NdFeB tile magnets as diffusion substrates with a thickness of 3 mm; polishing them to a mirror surface, and then ultrasonically cleaning them in acetone and anhydrous ethanol for 15 minutes each;

[0080] (6) applying the mixed diffusing agent obtained in step (4) uniformly to the two surfaces of the magnet obtained in step (5), and drying in an oven at 50° C. to obtain a magnet to be diffused; wherein the amount of the mixed diffusing agent powder (i.e., the mixed powder of the alloy powder and the ZnO powder in step (4)) is controlled to be about 1 wt% of the mass of the magnet;

[0081] (7) The magnet to be diffused obtained in step (6) is placed in a vacuum heat treatment furnace, and the pressure in the furnace is reduced to 3×10 -2 Pa, and then two-stage heat treatment is carried out; the temperature of the first-stage heat treatment is 800℃, and the heat preservation is 6h, and the temperature of the second-stage heat treatment is 500℃, and the heat preservation is 3h; after the two-stage heat treatment is completed, the magnet is cooled and taken out from the furnace to obtain a diffused magnet.

[0082] In this comparative example, after diffusion of the mixed powder of Pr-Al-Cu and ZnO, the coercive force of the magnet increased from 1101kA / m to 1550kA / m, an increase of 41%, the remanence and magnetic energy product decreased slightly, and the magnet quality increased from N54 to 50H. However, the resistivity of the magnet only increased from 213μΩ·cm to 467μΩ·cm. Compared with Example 1, this comparative example shows that when the proportion of non-rare earth oxides in the mixed powder is relatively large, it is better to improve the resistivity of the NdFeB rotor magnet.

[0083] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity, characterized in that: The following steps are involved: (1) mixing light rare earth low melting point alloy powder and non-rare earth oxide powder uniformly to obtain a mixed powder, and then mixing with an organic binder to obtain an alloy mixed grain boundary diffusion agent; (2) After the mixed grain boundary diffusing agent is uniformly coated on the surface of the NdFeB magnet, the NdFeB magnet is placed in a vacuum or oxygen-free condition for diffusion heat treatment to obtain a NdFeB rotor magnet; The mass ratio of the light rare earth low melting point alloy powder to the non-rare earth oxide powder in step (1) is 1:(1-4); The coating amount in step (2) is based on the mixed powder in the mixed grain boundary diffusion agent accounting for 0.5-3.0% of the mass of the NdFeB magnet; The light rare earth low melting point alloy powder in step (1) is at least one of LRE-M powders, wherein LRE is at least one of Pr, Nd, La and Ce, and M is at least one of Al, Cu, Ni, Co, Mg and Zn; The non-rare earth oxide powder in step (1) is at least one of ZnO, MgO, Al2O3, Cr2O3 and Zr2O3.

2. The method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity according to claim 1, characterized in that: The light rare earth low melting point alloy powder in step (1) is Pr 89.35 Al 4.89 Cu 5.76 Alloy, and La 87.68 Al 6.89 Cu 5.43 At least one of the alloys, all alloying elements are expressed in mass percentage; The non-rare earth oxide powder in step (1) is at least one of ZnO, MgO and Al2O3.

3. The method for preparing a high magnetic performance and high resistivity NdFeB rotor magnet according to claim 1, characterized in that: In step (1), the particle sizes of the light rare earth low melting point alloy powder and the non-rare earth oxide powder are both between 30 and 300 meshes.

4. The method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity according to claim 1, characterized in that: The vacuum condition in step (2) is 5×10 -2 ~5×10 -3 Pa; the diffusion heat treatment in step (2) is divided into primary heat treatment and secondary heat treatment, the temperature of the primary heat treatment is 650-1000°C, and the insulation time is 1-20h; the temperature of the secondary heat treatment is 400-550°C, and the insulation time is 1-5h.

5. The method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity according to claim 1, characterized in that: Step (2) the mixed grain boundary diffusion agent is evenly coated on both surfaces of the NdFeB magnet; The thickness of the NdFeB magnet in step (2) is between 2 and 8 mm.

6. The method for preparing a NdFeB rotor magnet with high magnetic properties and high resistivity according to claim 1, characterized in that: The organic binder in step (1) is 35-60wt% PVA glue, 37-64.5wt% ethanol and 0.5-3wt% polyethyleneimine composition; the mass ratio of the mixed powder to the organic binder is 1:0.5-1; The NdFeB magnet in step (2) is a sintered, hot-pressed or hot-deformed NdFeB magnet, and the magnet is in the shape of a sheet or a tile.

7. A NdFeB rotor magnet with high magnetic properties and high resistivity obtained by the preparation method according to any one of claims 1 to 6.

8. Application of the high magnetic properties and high resistivity NdFeB rotor magnet as claimed in claim 7 in electric drive systems of new energy vehicles, wind power generator sets, servo motors and air-conditioning compressors.

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