NiCuZn ferrite with high magnetic conductivity and preparation method thereof

Abstract

The invention provides NiCuZn ferrite with high magnetic conductivity and a preparation method thereof. The preparation method comprises the following steps: (1) carrying out primary ball milling on raw materials of the NiCuZn ferrite, and pre-sintering to obtain a pre-sintered material; and (2) the pre-sintered material and a doping agent are subjected to secondary ball milling, and after granulation, molding and sintering, the NiCuZn ferrite is obtained, and the doping agent comprises WO3 and TiO2. Through combined doping of WO3 and TiO2, the sample density can be improved, the magnetic conductivity, the Curie temperature and the saturation flux density can be improved, meanwhile, the magnetic loss is reduced, and the final ferrite can be suitable for electronic elements with high requirements for the magnetic conductivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic materials, and relates to a NiCuZn ferrite with high magnetic permeability and a preparation method thereof. Background Art

[0002] In the past 20 years, with the development of various information networks of wired and wireless electronic devices, mobile phones, and transformers, etc., electronic components have been developing towards miniaturization, personalization, and high frequency. Among them, the laminated inductor, as a very mature technology, has been widely used in the manufacture of LC composite components such as chip capacitors. NiZn ferrite has high resistivity and high magnetic permeability, but its sintering temperature is usually 1100 - 1300 °C, and it is difficult to achieve low-temperature co-firing with the Ag electrode in the laminated inductor. In order to reduce its sintering temperature, CuO is usually added to the main formula, and fluxes such as V 2 O 5 etc. can be doped to reduce the sintering temperature to about 900 °C.

[0003] For example, CN115925405A discloses a NiCuZn soft magnetic ferrite material with high magnetic permeability and high Curie temperature. Its main components include Fe 2 O 3 , ZnO, NiO, and CuO, and its doping components include Y 2 O 3 , MoO 3 , V 2 O 5 , and MnCO 3 . Among them, Y 2 O 3 is 0.05 wt% - 0.1 wt% of the mass of the main components, the content of MoO 3 is 0.06 wt% - 0.18 wt% of the mass of the main components, the content of V 2 O 5 is 0.05 wt% - 0.15 wt% of the mass of the main components, and the content of MnCO 3 is 0.55 wt% of the mass of the main components. At a test frequency of 100 kHz, the initial magnetic permeability is 2011, the specific loss factor is 28.78×10 -6 , the Curie temperature is 145 °C, and the saturation magnetic induction intensity Bs = 352 mT (10 kHz, 4000 A / m).

[0004] CN104030669A discloses a pressure filtration molding preparation method for NiZn ferrite. The main components include Fe 2 O 3 , ZnO, NiO, and CuO; the dopant is calculated by mass percentage: V 2 O 5: 0 to 3 wt%. The optimal magnetic properties obtained are as follows: the initial permeability is 2100, the specific loss factor is 5×10 -4 , the Curie temperature Tc = 98 °C, and the saturation magnetic induction intensity Bs = 240 mT.

[0005] In the above patents, some have a relatively low Curie temperature Tc, some have a relatively low initial permeability or a relatively low saturation magnetic induction intensity Bs, making it difficult to achieve high magnetic conductance, high Tc, high Bs, and low loss simultaneously, and thus they cannot be applied to some inductors, capacitors, and transformers with high requirements. Additionally, some doping materials are too complex, making production inconvenient.

[0006] Therefore, there is an urgent need to provide a doping method that can not only reduce the sintering temperature but also enable the ferrite to have high magnetic conductance, high Tc, high Bs, and low loss simultaneously. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a NiCuZn ferrite with high magnetic permeability and its preparation method. The present invention can reduce the sintering temperature through the combined doping of WO 3 and TiO 2 , and can also improve the magnetic permeability, Curie temperature, and saturation magnetic induction intensity, while reducing the magnetic loss, so that the final ferrite can be applicable to electronic components with high requirements for magnetic permeability.

[0008] In the first aspect, the present invention provides a preparation method of a NiCuZn ferrite with high magnetic permeability, and the preparation method includes:

[0009] (1) Conduct primary ball milling on the raw materials of the NiCuZn ferrite, and obtain a pre-sintered material after pre-sintering;

[0010] (2) Conduct secondary ball milling on the pre-sintered material and the dopant, and obtain the NiCuZn ferrite after granulation, forming, and sintering, wherein the dopant includes WO 3 and TiO 2 .

[0011] The present invention provides a preparation method of a NiCuZn ferrite with high magnetic permeability, which uses WO 3 and TiO 2 to co-dope the NiCuZn ferrite. Among them, the doping of WO 3 can cause an increase in cation vacancies near the grain boundaries of the NiCuZn ferrite, thereby accelerating the grain boundary movement, promoting the grain size to become larger. At the same time, the W ions have a strong ability to occupy the A site and replace Fe 3+The trend is that appropriate addition is beneficial to improving the saturation magnetization intensity of the material and increasing the magnetic permeability; Ti ions can be localized between grain boundaries, which is beneficial to promoting the displacement of magnetic domain walls and thus increasing the magnetic permeability. Under the action of W ions, the sintering temperature can be reduced and the saturation magnetization intensity can be increased. At the same time, Ti ions can promote the displacement of magnetic domain walls to enhance the magnetic permeability. Through the combined doping of WO 3 and TiO 2 , the sintering temperature can be reduced, and the magnetic permeability, Curie temperature and saturation magnetic induction intensity can be increased. At the same time, the magnetic loss can be reduced, so that the final ferrite can be applicable to electronic components with high requirements for magnetic permeability.

[0012] Preferably, the raw materials of the NiCuZn ferrite include Fe 2 O 3 , ZnO, NiO and CuO.

[0013] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of Fe 2 O 3 is 59 - 66.7%, for example, it can be 59.75%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of ZnO is 18.3 - 21.3%, for example, it can be 20.3%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of NiO is 10.6 - 11.6 wt%, for example, it can be 10.6%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In the present invention, after the mass fractions of Fe 2 O 3 , ZnO and NiO are satisfied, the balance is CuO.

[0017] Preferably, the ball - to - material ratio of the first ball - milling in step (1) is (3 - 4):1, for example, it can be 3:1 or 4:1, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] Preferably, the time of the first ball - milling in step (1) is 2 - 2.5 h, for example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] Preferably, the pre-sintering in step (1) is carried out in steps, and the stepwise pre-sintering includes primary pre-sintering and secondary pre-sintering carried out in sequence.

[0020] Preferably, the temperature of the primary pre-sintering is 300-400 °C, for example, it can be 300 °C, 320 °C, 340 °C, 360 °C, 380 °C or 400 °C, etc., and the time of the primary pre-sintering is 3-3.5 h, for example, it can be 3 h, 3.2 h, 3.4 h or 3.5 h, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0021] Preferably, the temperature of the secondary pre-sintering is 750-780 °C, for example, it can be 750 °C, 760 °C, 770 °C or 780 °C, etc., and the time of the secondary pre-sintering is 2-3 h, for example, it can be 2 h, 2.2 h, 2.3 h, 2.5 h or 2.8 h, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0022] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of the dopant is 0-0.41%, and it is not 0, for example, it can be 0.01, 0.02, 0.05, 0.07, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.41, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0023] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the 3 mass fraction of WO is 0-0.16%, and it is not 0, for example, it can be 0.01, 0.02, 0.05, 0.07, 0.08, 0.1, 0.12, 0.15 or 0.16, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0024] Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the 2 mass fraction of TiO is 0-0.25%, and it is not 0, for example, it can be 0.01, 0.02, 0.05, 0.07, 0.08, 0.1, 0.15, 0.18, 0.2, 0.22 or 0.25, etc., but it is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0025] Preferably, the 3 WO 2The mass ratio is (0.4 - 3.2):1. For example, it can be 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.64:1, 0.68:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1 or 3.2:1, etc. Preferably, it is (0.64 - 0.8):1, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In the present invention, if the mass ratio of WO 3 and TiO 2 is too low, it is difficult to reduce the sintering temperature, and since Ti 4+ will occupy the B site, excessive TiO 2 may cause a decrease in saturation magnetization intensity and a decline in performance; if the mass ratio of WO 3 and TiO 2 is too high, it may lead to non-uniform grain growth and a reduction in magnetic permeability.

[0027] Preferably, the ball-to-material ratio of the secondary ball milling in step (2) is (3 - 4):1. For example, it can be 3:1 or 4:1, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] Preferably, the time of the secondary ball milling in step (2) is 2 - 2.5 h. For example, it can be 2 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h or 2.5 h, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] Preferably, in step (2), between the secondary ball milling and granulation, the steps of ultra-fine grinding and drying are carried out in sequence.

[0030] In the present invention, the purpose of ultra-fine grinding is to make the particle size distribution more uniform, reduce the porosity of the sintered sample, and can cooperate with the co-doping of WO 3 and TiO 2 to synergistically improve the magnetic permeability.

[0031] Preferably, the rotation speed of the ultra-fine grinding is 2400 - 2500 r / min. For example, it can be 2400 r / min or 2450 r / min, etc. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0032] Preferably, the D50 particle size of the product after ultrafine grinding is 0.9 - 1.1 μm. For example, it can be 1.0 μm, 1.05 μm, 1.1 μm, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0033] Preferably, the binder used for granulation in step (2) includes a polyvinyl alcohol solution.

[0034] Preferably, the pressure for molding in step (2) is 5 - 7 MPa. For example, it can be 6 MPa, 6.5 MPa, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0035] Preferably, the sintering in step (2) is stepwise sintering, and the stepwise sintering includes primary sintering and secondary sintering carried out in sequence.

[0036] Preferably, the temperature for debinding is 200 - 300 °C. For example, it can be 200 °C, 220 °C, 250 °C, 280 °C, 300 °C, etc. The time for primary sintering is 3 - 4 h. For example, it can be 3 h, 3.2 h, 3.4 h, 3.8 h, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0037] Preferably, the temperature for secondary sintering is 900 - 910 °C. For example, it can be 900 °C, 905 °C, etc. The time for secondary sintering is 5 - 6 h. For example, it can be 5 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0038] Preferably, the atmosphere for sintering in step (2) is an oxygen-containing atmosphere, and the gas in the oxygen-containing atmosphere includes air.

[0039] As a preferred technical solution of the present invention, the preparation method specifically includes:

[0040] (I) Perform primary ball milling on the raw materials of NiCuZn ferrite. After drying, pre-sinter at 300 - 400 °C for 3 - 3.5 h, and then pre-sinter at 750 - 780 °C for 2 - 3 h to obtain a pre-sintered material;

[0041] (II) Perform secondary ball milling on the pre-sintered material and the dopant, and then perform ultrafine grinding on the product after secondary ball milling. After drying, granulating, and molding, obtain a product to be sintered. Then, sinter at 200 - 300 °C for 3 - 4 h, and then sinter at 900 - 910 °C for 5 - 6 h to obtain the NiCuZn ferrite, wherein the dopant includes WO 3 and TiO 2 .

[0042] In a second aspect, the present invention provides a NiCuZn ferrite with high magnetic permeability, which is prepared by the preparation method described in the first aspect.

[0043] Preferably, the magnetic permeability of the NiCuZn ferrite is 2150 - 2800, and can be, for example, 2150, 2200, 2500, 2800, etc.

[0044] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The present invention provides a preparation method for a NiCuZn ferrite with high magnetic permeability. WO 3 and TiO 2 are used to co-dope the NiCuZn ferrite. Among them, the doping of WO 3 can cause an increase in cation vacancies near the grain boundaries of the NiCuZn ferrite, thereby accelerating the grain boundary movement and promoting the increase in grain size. At the same time, the W ions have a strong tendency to occupy the A site and replace Fe 3+ . The addition of an appropriate amount is beneficial to improving the saturation magnetization intensity of the material and increasing the magnetic permeability; the Ti ions can be localized between the grain boundaries, which is beneficial to promoting the displacement of magnetic domain walls and thus increasing the magnetic permeability. Under the action of the W ions, the sintering temperature can be reduced and the saturation magnetization intensity can be increased. At the same time, the Ti ions can promote the displacement of magnetic domain walls to enhance the magnetic permeability. Through the combined doping of WO 3 and TiO 2 , the sintering temperature can be reduced, and the magnetic permeability, Curie temperature, and saturation magnetic induction intensity can be increased. At the same time, the magnetic loss can be reduced, so that the final ferrite can be applied to electronic components with high requirements for magnetic permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a graph of the magnetic permeability test results of Examples 1 - 8 and Comparative Examples 1 - 8 of the present invention.

[0048] Figure 2 It is a graph of the magnetic permeability test results of Examples 9 - 15 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0049] The technical solutions of the present invention will be further described below through specific embodiments.

[0050] Example 1

[0051] This embodiment provides a preparation method of NiCuZn ferrite with high magnetic permeability, including:

[0052] (1) Weigh raw materials of Fe 2 O 3 , ZnO, NiO and CuO with a total mass of 1 kg. Based on the total mass of the raw materials being 100%, the mass fraction of Fe 2 O 3 is 59.75%, the mass fraction of ZnO is 20.3%, the mass fraction of NiO is 10.6%, and the mass fraction of CuO is 9.35%. Put the raw materials prepared according to the above ratio into a ball milling tank, add deionized water and zirconia balls, with a ball-to-material ratio of 3:1, and ball mill for two and a half hours at 300 r / min;

[0053] (2) After drying the ball milling product obtained in step (1) and sieving it through a 50-mesh sieve, put it into a muffle furnace for pre-sintering. The pre-sintering process is: heat from room temperature to 300 °C in 3 h, then continue to heat to 750 °C in 5 h and pre-sinter for 2 h to obtain the pre-sintered material;

[0054] (3) After the pre-sintered material is cooled to room temperature and sieved through a 50-mesh sieve, dope WO 3 with a mass fraction of 0.04% and TiO 2 (based on the total mass of the raw materials being 100%). Put it into a ball milling tank, add deionized water and zirconia balls, with a ball-to-material ratio of 3:1, and perform the second ball milling for two and a half hours at a rotation speed of 300 r / min;

[0055] (4) Pour the slurry after the second ball milling obtained in step (3) into an ultrafine grinding device and perform 4 times of ultrafine grinding at a rotation speed of 2400 r / min. The particle size D50 of the product after ultrafine grinding is 0.9 - 1.1 μm, and pour out the slurry for drying;

[0056] (5) After the dried slurry is sieved through a 50-mesh sieve, drop 7% of the PVA glue based on the mass of the powder, stir and granulate, then use a mold with an outer diameter of 20 mm and an inner diameter of 10 mm to press into a sample ring at a pressure of 6 MPa. Put the sample ring into a muffle furnace for sintering. The sintering process is: heat from room temperature to 200 °C in 2 h, then continue to heat to 450 °C in 4 h, and finally heat to 900 °C in 5 h and sinter for 5 h to obtain the NiCuZn ferrite magnetic ring.

[0057] Examples 2 - 15 and Comparative Examples 1 - 8 are based on the steps of Example 1 with parameter changes. The specific changed parameters are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] Performance test

[0062] (1) Permeability test: Using an Agilent E4991A analyzer, the real part of the permeability μ of the magnetic rings of Examples 1-15 and Comparative Examples 1-8 was measured at 100 kHz i .

[0063] The test results of Examples 1-8 and Comparative Examples 1-8 are as Figure 1 shown. The curves at the bottom of the figure show the results of Comparative Examples 1-8. It can be seen that as the doping amount of WO 3 increases, the initial permeability first increases and then decreases, reaching a maximum value of 2526 when the doping amount is 0.16%; the curves at the top of the figure show the results of Examples 1-8. It can be seen that after adding 0.1% of TiO 2 , the permeability has increased significantly, with a promotion rate of about 4-5%, and after doping with TiO 2 , as the doping amount of WO 3 increases, the initial permeability still first increases and then decreases.

[0064] The test results of Examples 9-15 are as Figure 2 shown. It can be seen that as the doping amount of TiO 2 increases, the permeability also first increases and then decreases, and the permeability reaches a maximum value of 2736 when the doping amount is 0.25%.

[0065] (2) Curie temperature test: The magnetic rings of Example 1, Examples 11-13, and Comparative Example 1 were each evenly wound with 25 turns of copper wire with a diameter of 0.4 mm. Applying an alternating current with a frequency of 100 kHz and a voltage of 1 V, the permeability was measured at 20 °C, 40 °C, 60 °C, 80 °C, 100 °C, 110 °C, 120 °C, and 140 °C respectively, and the Curie temperature Tc was obtained according to the μ-T curve. The test results are shown in Table 2.

[0066] (3) Hysteresis loop test: The magnetic rings of Example 1, Examples 11-13, and Comparative Example 1 were each evenly wound with 30 turns of copper wire with a diameter of 0.4 mm. The hysteresis loop was tested under the conditions of 50 Hz and 100 °C to obtain the saturation magnetic induction intensity Bs and the coercive force Hc. The test results are shown in Table 2.

[0067] The permeability test results of Examples 11-13 are also summarized in Table 2.

[0068] Table 2

[0069]

[0070] As can be seen from Table 2, the magnetic rings prepared in Examples 11 - 13 all have a relatively high initial permeability μ i a relatively high Curie temperature Tc and a relatively high saturation magnetization, and at the same time, the coercivity Hc is relatively low, which is beneficial to reducing the hysteresis loss and increasing the Q value, and the comprehensive performance is excellent.

[0071] From the data of Example 1 and Examples 11 - 13, it can be seen that if the mass ratio of WO 3 and TiO 2 is relatively low, since Ti 4+ will occupy the B site, excessive TiO 2 may lead to a decrease in saturation magnetization and a decline in performance; if the mass ratio of WO 3 and TiO 2 is relatively high, it may lead to non-uniform grain growth and a slightly lower permeability.

[0072] From the data of Example 1 and Comparative Example 1, it can be seen that if TiO 2 is not doped, it will lead to a decrease in permeability.

[0073] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of NiCuZn ferrite with high magnetic permeability, characterized in that, the preparation method includes: (1) Conduct primary ball milling on the raw materials of NiCuZn ferrite, and obtain a pre-sintered material after pre-sintering; (2) The pre-sintered material and the dopant are subjected to secondary ball milling, and after granulation, molding and sintering, the NiCuZn ferrite is obtained, wherein the dopant includes WO 3 and TiO 2 .

2. The preparation method according to claim 1, characterized in that, The raw materials of the NiCuZn ferrite include Fe 2 O 3 , ZnO, NiO and CuO; Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of 2 O 3 is 59 - 66.7%; preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of ZnO is 18.3 - 21.3%; preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of NiO is 10.6 - 11.6 wt%.

3. The preparation method according to claim 1 or 2, characterized in that, the ball-to-material ratio of the primary ball milling in step (1) is (3 - 4):1; preferably, the time of the primary ball milling in step (1) is 2 - 2.5 h.

4. The preparation method according to any one of claims 1 - 3, characterized in that, the pre-sintering in step (1) is stepwise pre-sintering, and the stepwise pre-sintering includes primary pre-sintering and secondary pre-sintering carried out in sequence; preferably, the temperature of the primary pre-sintering is 300 - 400 °C, and the time of the primary pre-sintering is 3 - 3.5 h; preferably, the temperature of the secondary pre-sintering is 750 - 780 °C, and the time of the secondary pre-sintering is 2 - 3 h.

5. The preparation method according to any one of claims 1 - 4, characterized in that, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of the dopant is 0 - 0.41%, and not 0; Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of the WO 3 is 0 - 0.16%, and not 0; Preferably, based on the total mass of the raw materials of the NiCuZn ferrite being 100%, the mass fraction of TiO 2 is 0 - 0.25%, and not 0; Preferably, the mass ratio of WO 3 and TiO 2 is (0.4 - 3.2):1, preferably (0.64 - 0.8):

1.

6. The preparation method according to any one of claims 1 - 5, characterized in that, the ball-to-material ratio of the secondary ball milling in step (2) is (3 - 4):1; preferably, the time of the secondary ball milling in step (2) is 2 - 2.5 h; preferably, in step (2), between the secondary ball milling and granulation, steps of ultrafine grinding and drying are carried out in sequence; preferably, the particle size D50 of the product after ultrafine grinding is 0.9 - 1.1 μm.

7. The preparation method according to any one of claims 1 - 6, characterized in that, the binder used for granulation in step (2) includes polyvinyl alcohol solution; preferably, the pressure of molding in step (2) is 5 - 7 MPa.

8. The preparation method according to any one of claims 1 - 7, characterized in that, the sintering in step (2) is stepwise sintering, and the stepwise sintering includes primary sintering and secondary sintering carried out in sequence; preferably, the temperature of the primary sintering is 200 - 300 °C, and the time of the primary sintering is 3 - 4 h; preferably, the temperature of the secondary sintering is 900 - 910 °C, and the time of the secondary sintering is 5 - 6 h; preferably, the atmosphere of sintering in step (2) is an oxygen-containing atmosphere, and the gas in the oxygen-containing atmosphere includes air.

9. The preparation method according to any one of claims 1 - 8, characterized in that, the preparation method specifically includes: (Ⅰ) The raw materials of NiCuZn ferrite are ball-milled once. After drying, they are pre-fired at 300 - 400 °C for 3 - 3.5 h first, and then pre-fired at 750 - 780 °C for 2 - 3 h to obtain the pre-fired material; (Ⅱ) Secondary ball milling is carried out on the pre-sintered material and the dopant, and then the product after secondary ball milling is subjected to ultrafine grinding. After drying, granulation and molding, the product to be sintered is obtained. Then, it is first sintered at 200 - 300 °C for 3 - 4 h, and then sintered at 900 - 910 °C for 5 - 6 h to obtain the NiCuZn ferrite. Among them, the dopant includes WO 3 and TiO 2 .

10. A NiCuZn ferrite with high magnetic permeability, characterized in that, the NiCuZn ferrite is prepared by the preparation method described in any one of claims 1 - 9; Preferably, the magnetic permeability of the NiCuZn ferrite is 2150 - 2800.

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