A neodymium iron boron magnet and its preparation method

Abstract

This application relates to the technical field of neodymium iron boron (NdFeB) magnets, and more specifically, to a NdFeB magnet and its preparation method. A NdFeB magnet comprises the following raw materials in parts by weight: 90-100 parts neodymium, 13-17 parts ferroboron, 160-180 parts iron, and 6-8 parts co-doped rare earth alloy; the co-doped rare earth alloy contains lanthanum, gadolinium, and dysprosium, and the weight percentage of dysprosium in the NdFeB magnet is 0.3-2.5%, and the weight percentage of lanthanum in the NdFeB magnet is 0.15-1.0%. The NdFeB magnet of this application has the effect of reducing the dysprosium content in the NdFeB magnet without affecting its high-temperature resistance.

Description

Technical Field

[0001] This application relates to the technical field of neodymium iron boron magnets, and more specifically, to a neodymium iron boron magnet and a method for preparing the same. Background Technology

[0002] Sintered NdFeB magnets are the strongest permanent magnets available today. They possess excellent properties such as high energy product and high cost-effectiveness, and are now used in aviation, aerospace, microwave communication technology, electronics, electroacoustics, electromechanical and other fields. However, as the application range of permanent magnets continues to expand, people's demand for them is also increasing. While permanent magnets meet the requirements of various equipment models, they also pose challenges to the applicable temperature range of permanent magnets.

[0003] In practical applications, the maximum operating temperature of a common magnet is used as one of the standards for measuring its temperature characteristics. Improving the operating temperature of NdFeB magnets mainly focuses on the following three aspects: increasing the Curie temperature T of the magnet. c , improve the intrinsic coercivity H of the magnet cj And reducing the temperature coefficient of the magnet, and the main way to reduce the temperature coefficient is to increase T. c and H cj .

[0004] For a long time, the widely used method in the NdFeB magnet manufacturing industry has been to add heavy rare earth elements such as Dy or Tb during the smelting stage, thereby significantly improving the intrinsic coercivity H of NdFeB magnets. cj This would increase the operating temperature of NdFeB magnets. However, because the abundance of Dy and Tb in the Earth's crust is much lower than that of Nd, their high price limits the application of high coercivity magnets. Therefore, there is an urgent need for a NdFeB magnet with low Dy and Tb content. Summary of the Invention

[0005] In order to reduce the content of Dy and Tb in NdFeB magnets without affecting their high-temperature resistance, this application provides a NdFeB magnet and its preparation method.

[0006] In a first aspect, this application provides a neodymium iron boron magnet, which adopts the following technical solution:

[0007] A neodymium iron boron magnet comprises the following raw materials in parts by weight: 90-100 parts neodymium, 13-17 parts ferroboron, 160-180 parts iron, and 6-8 parts co-doped rare earth alloy, wherein the co-doped rare earth alloy contains lanthanum, gadolinium, and dysprosium, wherein the weight percentage of dysprosium in the neodymium iron boron magnet is 0.3-2.5%, and the weight percentage of lanthanum in the neodymium iron boron magnet is 0.15-1.0%.

[0008] Compared to dysprosium, lanthanum is significantly more abundant in the Earth's crust, and therefore its price is relatively cheaper. However, the addition of large amounts of lanthanum has a certain negative impact on the intrinsic coercivity and Curie temperature of NdFeB magnets. However, a small amount of lanthanum can improve the diffusion effect of dysprosium within the NdFeB grain boundaries, thereby increasing the intrinsic coercivity of the NdFeB magnets. Gadolinium has the highest Curie temperature among the lanthanides; therefore, the addition of gadolinium can effectively compensate for the decrease in Curie temperature caused by the addition of lanthanum in NdFeB magnets, thus achieving a reduction in the dysprosium content in NdFeB magnets without affecting their high-temperature resistance.

[0009] Preferably, in the co-doped rare earth alloy, the mass ratio of lanthanum, gadolinium, and dysprosium is (1-3):(4-6):(3-5).

[0010] When lanthanum, gadolinium, and dysprosium are used in the above-mentioned mass ratio, lanthanum can enhance the diffusion effect of dysprosium without significantly affecting the intrinsic coercivity and Curie temperature of the NdFeB magnet as a whole. At the above-mentioned ratio, gadolinium can enhance the Curie temperature of the NdFeB magnet without significantly affecting the intrinsic coercivity of the NdFeB magnet as a whole. Thus, the dysprosium content in the NdFeB magnet can be reduced without affecting the high-temperature resistance of the NdFeB magnet.

[0011] Preferably, the co-doped rare earth alloy also contains cobalt, gallium, copper, and aluminum.

[0012] Cobalt has a higher Curie temperature than iron; therefore, adding cobalt helps to increase the Curie temperature and reduce the remanence temperature coefficient. Furthermore, adding cobalt forms a more stable Nd3Co grain boundary phase at the grain boundaries, replacing the previously easily corroded Nd-rich phase, thereby increasing the corrosion resistance of NdFeB magnets.

[0013] The addition of gallium can form Nd2Fe in the magnet. 14 The -XGaXB and GaNd systems increase the volume fraction of the liquid phase in the NdFeB magnet during sintering, thus aiding in sintering, increasing the magnet's density, improving coercivity, and enhancing the stability of NdFeB magnets at high temperatures.

[0014] Aluminum and copper have relatively low permeability, which can effectively reduce the magnetic coupling between the main phase grains, thereby improving the coercivity of NdFeB magnets. Moreover, the addition of copper and aluminum to the intergranular space of NdFeB magnets has almost no effect on the reversible temperature coefficient of the magnets.

[0015] Preferably, the co-doped rare earth alloy is a mixture of lanthanum-dysprosium-gallium alloy, gadolinium-cobalt-gallium alloy, and copper-aluminum-gallium alloy.

[0016] Compared to adding lanthanum, dysprosium, and gallium separately, alloying lanthanum, dysprosium, and gallium can further enhance the diffusion effect of lanthanum on dysprosium, while gallium doping can effectively compensate for the loss of intrinsic coercivity caused by excessive addition of lanthanum.

[0017] Compared to adding gadolinium, cobalt, or gallium individually, alloying gadolinium, cobalt, and gallium can effectively improve the microstructure of NdFeB magnets, enhance their magnetocrystalline anisotropy, and thus improve their coercivity. Furthermore, gadolinium, cobalt, and gallium alloys can effectively increase the Curie temperature of NdFeB magnets, reduce irreversible flux loss, and improve their thermal stability.

[0018] Compared to adding copper, aluminum, and gallium individually, alloying copper, aluminum, and gallium helps improve the wettability between the main phase and the rare-earth-rich phase of NdFeB magnets, optimizes the distribution of rare-earth-rich phases at grain boundaries, thereby increasing the coercivity of NdFeB magnets, reducing irreversible flux loss, and improving the thermal stability of NdFeB magnets.

[0019] Preferably, in the lanthanum-dysprosium-gallium alloy, the mass ratio of lanthanum, dysprosium, and gallium is (1-3):(3-5):(1-3).

[0020] When lanthanum, dysprosium, and gallium are in the above weight ratio, there is an optimal compatibility relationship between them. Lanthanum can more effectively promote the diffusion of dysprosium, and with the cooperation of gallium, the influence of the lanthanum-dysprosium-gallium alloy on the intrinsic coercivity of neodymium iron boron magnets can be minimized.

[0021] Preferably, in the gadolinium-cobalt-gallium alloy, the mass ratio of gadolinium, cobalt and gallium is (4-6):(2-4):(1-3).

[0022] When gadolinium, cobalt, and gallium are in the above mass ratio, there is an optimal compatibility among them, which further improves the magnetocrystalline anisotropy field of the NdFeB magnet, thereby enhancing the coercivity of the NdFeB magnet, effectively increasing the Curie temperature of the NdFeB magnet, reducing the irreversible flux loss of the magnet, and further increasing the thermal stability of the NdFeB magnet.

[0023] Preferably, in the terbium aluminum gallium alloy, the mass ratio of copper, aluminum and gallium in the copper aluminum gallium alloy is (5-7):(1-3):(1-3).

[0024] When copper, aluminum, and gallium are in the above mass ratio, they exhibit an optimal compatibility, further improving the wettability between the main phase and the rare-earth-rich phase of the NdFeB magnet, optimizing the distribution of the rare-earth-rich phase at grain boundaries, further enhancing the coercivity of the NdFeB magnet, reducing irreversible flux loss, and improving the thermal stability of the NdFeB magnet.

[0025] Preferably, the neodymium iron boron magnet further comprises 0.1-0.3 parts zirconium.

[0026] The addition of zirconium can effectively increase the sintering temperature of NdFeB magnets, making it less prone to abnormal grain growth. It also improves the coercivity of NdFeB magnets. In addition, the addition of zirconium greatly reduces the sensitivity of NdFeB magnets to sintering temperature, thereby enabling NdFeB magnets to obtain better temperature stability.

[0027] Secondly, this application provides a method for preparing a neodymium iron boron magnet, which adopts the following technical solution:

[0028] A method for preparing a neodymium iron boron magnet includes the following steps:

[0029] S1. Mix neodymium, ferroboron, and iron, then vacuum melt at a temperature of 1000-1100℃, cool and hydrogen break down to obtain neodymium iron boron magnet powder.

[0030] Lanthanum, dysprosium, and gallium are mixed and then vacuum melted at a temperature of 1400-1500℃. After cooling and hydrogen breaking, lanthanum-dysprosium-gallium alloy powder is obtained.

[0031] Gadolinium, cobalt, and gallium are mixed and then vacuum-melted at 1500-1600°C. After cooling and hydrogen breaking, gadolinium-cobalt-gallium alloy powder is obtained.

[0032] Copper, aluminum, and gallium are mixed and then vacuum melted at a temperature of 1500-1600℃. After cooling and hydrogen breaking, copper-aluminum-gallium alloy powder is obtained.

[0033] Lanthanum-dysprosium-gallium alloy powder, gadolinium-cobalt-gallium alloy powder, and copper-aluminum-gallium alloy powder are mixed to obtain a co-doped rare earth alloy; S2, neodymium iron boron magnet powder and the co-doped rare earth alloy are mixed, then pressed into shape, and then vacuum sintered at 1100-1200℃ and held for 2-4 hours, then vacuum tempered at 800-900℃ and held for 1-3 hours, then vacuum tempered at 400-500℃ and held for 1-3 hours, and finally cooled to obtain neodymium iron boron magnet.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. A small amount of lanthanum can enhance the diffusion effect of dysprosium in the NdFeB grain boundaries, thereby improving the intrinsic coercivity of NdFeB magnets. Gadolinium can effectively compensate for the decrease in Curie temperature caused by the addition of lanthanum in NdFeB magnets, thus achieving a reduction in the dysprosium content in NdFeB magnets without affecting the high-temperature resistance of NdFeB magnets.

[0036] 2. Lanthanum-dysprosium-gallium alloying can further improve the diffusion effect of lanthanum on dysprosium, while gallium doping can effectively compensate for the loss of intrinsic coercivity caused by excessive addition of lanthanum;

[0037] 3. Gadolinium-cobalt-gallium alloying can effectively improve the microstructure of NdFeB magnets, enhance their magnetocrystalline anisotropy, and thus improve their coercivity. Furthermore, gadolinium-cobalt-gallium alloying can effectively increase the Curie temperature of NdFeB magnets, reduce irreversible flux loss, and increase their thermal stability.

[0038] 4. Copper-aluminum-gallium alloying helps improve the wettability between the main phase and the rare-earth-rich phase of NdFeB magnets, optimizes the distribution of rare-earth-rich phase at grain boundaries, thereby improving the coercivity of NdFeB magnets, reducing irreversible flux loss of NdFeB magnets, and improving the thermal stability of NdFeB magnets. Detailed Implementation

[0039] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0040] raw material

[0041] Neodymium CAS: 7440-00-8; Boron Iron CAS: 11108-67-1; Iron CAS: 7439-89-6; Lanthanum CAS: 7439-91-0; Gadolinium CAS: 7440-54-2; Dysprosium CAS: 14692-17-2; Cobalt CAS: 7440-48-4; Gallium CAS: 7440-55-3; Copper CAS: 7440-50-8; Aluminum CAS: 7429-90-5; Zirconium CAS: 7440-67-7.

[0042] Example

[0043] Example 1

[0044] A method for preparing a neodymium iron boron magnet includes the following steps:

[0045] S1. Mix 95g of neodymium, 15g of ferroboron and 170g of iron, then vacuum melt at 1050℃ (1000-1100℃ is also suitable), then cool naturally and hydrogen break down and grind to obtain 800 mesh neodymium iron boron magnet powder.

[0046] The co-doped rare earth alloy was ground into 800-mesh co-doped rare earth alloy powder. The amount of co-doped rare earth alloy added was 7g. The co-doped rare earth alloy powder was composed of lanthanum, gadolinium and dysprosium, and the mass ratio of lanthanum, gadolinium and dysprosium was 2:5:4.

[0047] S2, NdFeB magnet powder and co-doped rare earth alloy powder are mixed, then pressed into shape, and then vacuum sintered at 1050℃ (1100-1200℃ is suitable) and held for 3h (2-4h is suitable). Then, vacuum tempering is performed at 850℃ (800-900℃) and held for 2h (1-3h is suitable). After that, vacuum tempering is performed at 450℃ (400-500℃ is suitable) and held for 2h (1-3h). Finally, it is cooled to room temperature to obtain NdFeB magnet.

[0048] Example 2-3

[0049] The difference from Example 1 is that the amount of each raw material added is different, as shown in Table 1.

[0050] Table 1. Amounts (g) of each raw material added in Examples 1-3

[0051] neodymium Boron iron iron Co-doped rare earth alloy powder Example 1 95 15 170 7 Example 2 100 13 180 8 Example 3 90 17 160 6

[0052] Examples 4-5

[0053] The difference from Example 1 is that the proportions of lanthanum, gadolinium, and dysprosium added are different, as shown in Table 2.

[0054] Table 2. Amounts (g) of lanthanum, gadolinium, and dysprosium added in Examples 1 and 4-5.

[0055] lanthanum gadolinium dysprosium Example 1 2 5 4 Example 4 3 4 5 Example 5 1 6 3

[0056] Example 6

[0057] The difference from Example 1 is that in S1, the co-doped rare earth alloy powder is composed of lanthanum, gadolinium, dysprosium, cobalt, gallium, copper, and aluminum, and the mass ratio of lanthanum, gadolinium, dysprosium, cobalt, gallium, copper, and aluminum is 2:5:4:3:6:6:2.

[0058] Example 7

[0059] A method for preparing a neodymium iron boron magnet includes the following steps:

[0060] S1. Mix 95g of neodymium, 15g of ferroboron and 170g of iron, then vacuum melt at 1050℃ (1000-1100℃ is also suitable), then cool naturally and hydrogen break down and grind to obtain 800 mesh neodymium iron boron magnet powder.

[0061] 0.5g of lanthanum, 1g of dysprosium, and 0.5g of gallium were mixed and then vacuum melted at 1450℃ (1400-1500℃ is also suitable). After cooling to room temperature, hydrogen was broken down to obtain 800-mesh lanthanum-dysprosium-gallium alloy powder.

[0062] 1.25g g of gadolinium, 0.75g of cobalt and 0.5g of gallium were mixed and then vacuum melted at 1550℃ (1500-1600℃ is also suitable). After cooling to room temperature and hydrogen breaking, 800-mesh gadolinium-cobalt-gallium alloy powder was obtained.

[0063] 1.5g of copper, 0.5g of aluminum, and 0.5g of gallium were mixed and then vacuum melted at 1550℃ (1500-1600℃ is also suitable). After cooling to room temperature, hydrogen was broken down to obtain copper-aluminum-gallium alloy powder.

[0064] Lanthanum-dysprosium-gallium alloy powder, gadolinium-cobalt-gallium alloy powder, and copper-aluminum-gallium alloy powder are mixed to obtain a co-doped rare earth alloy.

[0065] S2, NdFeB magnet powder and co-doped rare earth alloy are mixed and then pressed into shape. Then, vacuum sintering is carried out at 1050℃ (1100-1200℃ is also suitable) and held for 3h (2-4h is also suitable). Then, vacuum tempering is carried out at 850℃ (800-900℃) and held for 2h (1-3h is also suitable). Then, vacuum tempering is carried out at 450℃ (400-500℃ is also suitable) and held for 2h (1-3h). Finally, it is cooled to room temperature to obtain NdFeB magnet.

[0066] Examples 8-9

[0067] The difference from Example 7 is that the mass ratio of lanthanum, dysprosium, and gallium is different, as shown in Table 3.

[0068] Table 3. Addition ratios of lanthanum, dysprosium, and gallium in Examples 7-9

[0069] lanthanum dysprosium gallium Example 7 2 4 2 Example 8 1 5 1 Example 9 3 3 3

[0070] Examples 10-11

[0071] The difference from Example 7 is that the amounts of gadolinium, cobalt, and gallium added are different, as shown in Table 4.

[0072] Table 4. The proportions of gadolinium, cobalt, and gallium added in Examples 7 and 10-11.

[0073] gadolinium cobalt gallium Example 7 5 3 2 Example 10 6 2 3 Example 11 4 4 1

[0074] Examples 12-13

[0075] The difference from Example 7 is that the proportions of copper, aluminum and gallium added are different, as shown in Table 5.

[0076] Table 5. The proportions of copper, aluminum, and gallium added in Examples 7 and 12-13.

[0077] copper aluminum gallium Example 7 6 2 2 Example 12 7 1 3 Example 13 5 3 1

[0078] Example 14

[0079] The difference from Example 7 is that 0.2g of zirconium powder (800 mesh) is also added to S2.

[0080] Examples 15-16

[0081] The difference from Example 14 is that the amount of zirconium powder added is different, as shown in Table 6.

[0082] Table 6. Amount of zirconium added in Examples 14-16 (g)

[0083] Example 14 Example 15 Example 16 zirconium 0.2 0.1 0.3

[0084] Comparative Example

[0085] Comparative Example 1

[0086] A method for preparing a neodymium iron boron magnet includes the following steps:

[0087] S1. Mix 95g of neodymium, 15g of ferroboron and 170g of iron, then vacuum melt at 1050℃ (1000-1100℃ is also suitable), then cool naturally and hydrogen break down and grind to obtain 800 mesh neodymium iron boron magnet powder.

[0088] 7g of dysprosium was ground to obtain 800-mesh dysprosium powder;

[0089] S2, NdFeB magnet powder and dysprosium powder are mixed, then pressed into shape, and then vacuum sintered at 1050℃ (1100-1200℃ is suitable) and held for 3h (2-4h is suitable). Then, vacuum tempering is carried out at 850℃ (800-900℃) and held for 2h (1-3h is suitable). After that, vacuum tempering is carried out at 450℃ (400-500℃ is suitable) and held for 2h (1-3h). Finally, it is cooled to room temperature to obtain NdFeB magnet.

[0090] Performance testing

[0091] Detection methods

[0092] Three samples were taken from Examples 1-16 and Comparative Example 1, and then the following tests were performed and the average value was taken.

[0093] Experiment 1: Magnetic Property Test

[0094] The above samples were tested using the magnetic test methods in GB / T3217 "Permanent Magnet (Hard Magnet) Materials", and the intrinsic coercivity and Curie temperature were then obtained.

[0095] Test 2: Maximum Operating Temperature Test

[0096] The samples were tested using the highest operating temperature specified in GB / T13560-2017 "Sintered NdFeB Permanent Magnet Materials", and the highest operating temperature was subsequently obtained.

[0097] Test results: The test results of Examples 1-16 and Comparative Example 1 are shown in Table 7.

[0098] Table 7 shows the test results of Examples 1-16 and Comparative Example 1.

[0099]

[0100]

[0101] Referring to Examples 1-3 and Comparative Example 1, and in conjunction with Table 7, it can be seen that, compared to Comparative Example 1, the intrinsic coercivity of Examples 1-3 is reduced to a certain extent, but the Curie temperature of Examples 1-3 is significantly increased, thus making the maximum operating temperature of Examples 1-3 similar to that of Comparative Example 1. This effectively reduces the dysprosium content without affecting the high-temperature resistance of the neodymium iron boron magnet.

[0102] The reason for this is that a small amount of lanthanum can enhance the diffusion effect of dysprosium within the NdFeB grain boundaries, while gadolinium has the highest Curie temperature among the lanthanides. This allows for a reduction in the dysprosium content in NdFeB magnets without affecting their high-temperature resistance.

[0103] Referring to Examples 1 and 4-5 and referring to Table 7, it can be seen that the intrinsic coercivity of Examples 4-5 is significantly reduced compared to Example 1, with the reduction being more significant in Example 5. The Curie temperature of Example 4 is also reduced, while that of Example 5 is increased. However, the maximum operating temperature of Examples 4-5 is still relatively low compared to Example 1, indicating that the optimal addition ratio of lanthanum, gadolinium, and dysprosium is found in Example 1.

[0104] Referring to Examples 1 and 6 and in conjunction with Table 7, it can be seen that, compared to Example 1, the intrinsic coercivity and Curie temperature of Example 6 are significantly improved, which in turn leads to an increase in the maximum operating temperature of Example 6. This indicates that the addition of cobalt, gallium, copper, and aluminum can improve the high-temperature resistance of neodymium iron boron magnets as a whole.

[0105] The reasons for this are as follows: the addition of cobalt helps to increase the Curie temperature and reduce the remanence temperature coefficient. The addition of gallium can form Nd₂Fe₁₄-XGaXB and GaNd systems in the magnet, increasing the volume fraction of the liquid phase during the sintering process of NdFeB magnets, thus aiding sintering, increasing the magnet density, and improving coercivity and stability of NdFeB magnets at high temperatures. Aluminum and copper have relatively low permeability, thus effectively reducing magnetic coupling between the main phase grains, thereby improving the coercivity of NdFeB magnets. Furthermore, the addition of copper and aluminum to the intergranular spaces of NdFeB magnets has almost no effect on the reversible temperature coefficient of the magnet.

[0106] Referring to Examples 6-7 and Table 7, it can be seen that, compared to Example 6, the intrinsic coercivity and Curie temperature of Example 7 are further improved, thereby further increasing the maximum operating temperature of Example 7. This indicates that, compared to adding lanthanum, gadolinium, dysprosium, cobalt, gallium, copper, and aluminum alone, alloying lanthanum with dysprosium and gallium, alloying gadolinium with cobalt and gallium, and alloying copper with aluminum and gallium can further improve the intrinsic coercivity and Curie temperature of NdFeB magnets, thereby improving the high-temperature resistance of NdFeB magnets.

[0107] The reason for this is that lanthanum-dysprosium-gallium alloying can further improve the diffusion effect of lanthanum on dysprosium, while gallium doping can effectively compensate for the loss of intrinsic coercivity caused by excessive lanthanum addition.

[0108] Gadolinium-cobalt-gallium alloying can effectively improve the microstructure of NdFeB magnets, enhance their magnetocrystalline anisotropy, and thus improve their coercivity. Furthermore, gadolinium-cobalt-gallium alloys can effectively increase the Curie temperature of NdFeB magnets, reduce irreversible flux loss, and improve their thermal stability.

[0109] Copper-aluminum-gallium alloying helps improve the wettability between the main phase and the rare-earth-rich phase of NdFeB magnets, optimizes the distribution of rare-earth-rich phase at grain boundaries, thereby increasing the coercivity of NdFeB magnets, reducing irreversible flux loss, and improving the thermal stability of NdFeB magnets.

[0110] Referring to Examples 7-9 and Table 7, it can be seen that compared to Example 7, Example 8 shows a slight increase in intrinsic coercivity, Curie temperature, and maximum operating temperature; however, the amount of dysprosium added is also increased. In contrast, Example 9 shows a significant decrease in intrinsic coercivity, Curie temperature, and maximum operating temperature. In summary, the mass ratio of lanthanum, dysprosium, and gallium used in Example 7 is relatively optimal.

[0111] Referring to Examples 7, 10-11, and Table 7, it can be seen that compared to Example 7, the intrinsic coercivity, Curie temperature, and maximum operating temperature of Example 10 are slightly improved, but the improvement is not significant. In contrast, the intrinsic coercivity, Curie temperature, and maximum operating temperature of Example 11 are significantly decreased. In summary, the mass ratios of gadolinium, cobalt, and gallium used in Examples 7 and 10 are both suitable.

[0112] Referring to Examples 7 and 12-13 and referring to Table 7, it can be seen that compared with Example 7, the Curie temperatures of Examples 12-13 did not change significantly, but the intrinsic coercivity of Examples 12-13 decreased significantly, which in turn caused the maximum operating temperature of Examples 12-13 to also decrease. In summary, copper, aluminum, and gallium are relatively superior when added in the proportions of Example 7.

[0113] Referring to Examples 7, Examples 14-16 and in conjunction with Table 7, it can be seen that, compared to Example 7, although the Curie temperature of Example 14 did not change significantly, the intrinsic coercivity of Example 14 was significantly improved, which in turn led to an increase in the maximum operating temperature of Example 14.

[0114] The reason for this is that the addition of zirconium can effectively increase the sintering temperature of NdFeB magnets, making it less likely for the grains to grow abnormally. At the same time, it can improve the coercivity of NdFeB magnets. In addition, the addition of zirconium can greatly reduce the sensitivity of NdFeB magnets to sintering temperature, thereby enabling NdFeB magnets to obtain better temperature stability.

[0115] Compared to Example 14, Example 15 exhibits a slightly lower intrinsic coercivity, which in turn leads to a slightly lower operating temperature. Example 16 exhibits a slightly higher intrinsic coercivity, which in turn leads to a slightly higher operating temperature, but the increase is not significant.

[0116] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A neodymium iron boron magnet, characterized in that, The raw materials comprise the following parts by weight: 90-100 parts neodymium, 13-17 parts ferroboron, 160-180 parts iron, and 6-8 parts co-doped rare earth alloy, wherein the co-doped rare earth alloy contains lanthanum, gadolinium, and dysprosium, the weight percentage of dysprosium in the neodymium iron boron magnet is 0.3-2.5%, and the weight percentage of lanthanum in the neodymium iron boron magnet is 0.15-1.0%. The co-doped rare earth alloy also contains cobalt, gallium, copper, and aluminum; The co-doped rare earth alloy is a mixture of lanthanum-dysprosium-gallium alloy, gadolinium-cobalt-gallium alloy, and copper-aluminum-gallium alloy.

2. The neodymium iron boron magnet according to claim 1, characterized in that: In the co-doped rare earth alloy, the mass ratio of lanthanum, gadolinium, and dysprosium is (1-3):(4-6):(3-5).

3. The neodymium iron boron magnet according to claim 1, characterized in that: In the lanthanum-dysprosium-gallium alloy, the mass ratio of lanthanum, dysprosium, and gallium is (1-3):(3-5):(1-3).

4. The neodymium iron boron magnet according to claim 1, characterized in that: In the gadolinium-cobalt-gallium alloy, the mass ratio of gadolinium, cobalt and gallium is (4-6):(2-4):(1-3).

5. The neodymium iron boron magnet according to claim 1, characterized in that: In the copper-aluminum-gallium alloy, the mass ratio of copper, aluminum and gallium is (5-7):(1-3):(1-3).

6. The neodymium iron boron magnet according to claim 1, characterized in that: The neodymium iron boron magnet also includes 0.1-0.3 parts zirconium.

7. A method for preparing a neodymium iron boron magnet according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix neodymium, ferroboron, and iron, then vacuum melt at a temperature of 1000-1100℃, cool and hydrogen break down to obtain neodymium iron boron magnet powder. Lanthanum, dysprosium, and gallium are mixed and then vacuum melted at a temperature of 1400-1500℃. After cooling and hydrogen breaking, lanthanum-dysprosium-gallium alloy powder is obtained. Gadolinium, cobalt, and gallium are mixed and then vacuum-melted at 1500-1600°C. After cooling and hydrogen breaking, gadolinium-cobalt-gallium alloy powder is obtained. Copper, aluminum, and gallium are mixed and then vacuum melted at a temperature of 1500-1600℃. After cooling and hydrogen breaking, copper-aluminum-gallium alloy powder is obtained. Lanthanum-dysprosium-gallium alloy powder, gadolinium-cobalt-gallium alloy powder, and copper-aluminum-gallium alloy powder are mixed to obtain a co-doped rare earth alloy. S2. The neodymium iron boron magnet powder and co-doped rare earth alloy are mixed, then pressed into shape, and then vacuum sintered at 1100-1200℃ for 2-4 hours. Then, vacuum tempering is performed at 800-900℃ for 1-3 hours, and then vacuum tempering is performed at 400-500℃ for 1-3 hours. Finally, the magnet is cooled to obtain neodymium iron boron magnet.

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