A medium-high frequency low-loss mnzn ferrite material and a preparation method thereof

Abstract

The application relates to a medium-high-frequency low-loss MnZn ferrite material and a preparation method thereof. The MnZn ferrite particles or modified MnZn ferrite particles are pressed into a magnetic ring under 300-500 MPa, then the magnetic ring is subjected to multi-section partition sintering, and after sintering is completed, the magnetic ring is cooled to obtain the medium-high-frequency low-loss MnZn ferrite material. The preparation method provided by the application is used for carrying out multi-section partition sintering on the magnetic ring pressed by the MnZn ferrite particles or the modified MnZn ferrite particles, the sintering process is controlled in the aspects of the heating rate, the heating environment, the holding temperature, the holding time, the sintering temperature and the sintering environment, the grain size of the MnZn ferrite material is reduced, the eddy current loss and the residual loss are limited, and the medium-high-frequency low-loss MnZn ferrite material prepared by the application has the characteristics of medium-high frequency and low loss.

Description

TECHNICAL FIELD

[0001] The application relates to a medium-high-frequency low-loss MnZn ferrite material and a preparation method thereof, and belongs to the technical field of magnetic material preparation. BACKGROUND

[0002] With the wide application of 5G communication technology and the third generation wide band gap semiconductor, power electronic devices (such as switching power supply transformers, inverters, AC-DC converters and the like) are rapidly developing towards miniaturization, high efficiency and high frequency. As the main component material of power electronic devices, MnZn ferrite has been widely concerned in the medium-high-frequency performance with the development of technology. Generally, when the working frequency rises to 500 kHz or even 1 MHz, the power loss of MnZn power ferrite will sharply rise, which will cause the heating and efficiency reduction of electronic components, and even make the device unable to work normally under the condition of medium-high-frequency, thereby restricting the development of high-frequency power devices. Therefore, it is crucial to develop a low-loss MnZn power ferrite working under medium-high-frequency. Generally, MnZn power ferrite needs to be sintered at high temperature for a long time to show good performance, but high-temperature long-time sintering will make the MnZn ferrite grain grow, and the eddy current loss and residual loss will be high in the medium-high-frequency range, thereby increasing the total loss. Moreover, high-temperature long-time sintering has high energy consumption and high cost, therefore, it is urgent to design a new sintering preparation process to obtain MnZn power ferrite which can be applied in the medium-high-frequency range.

[0003] Chinese patent document CN116813320A discloses a sintering preparation method of MnZn ferrite material for MHz frequency, and the material has a loss of 385-664 kW / m 3 at 1 MHz, 30 mT, in the temperature range of 25 DEG C-140 DEG C. The loss of the material obtained by the patent at 1 MHz is still high, and it is not mentioned whether the MnZn ferrite material obtained by the sintering process can be applied in the frequency range other than 1 MHz.

[0004] Therefore, it is of great significance to develop a suitable sintering process to prepare MnZn power ferrite material with lower loss in the medium-high-frequency range for the application of MnZn power ferrite material. SUMMARY

[0005] In view of the deficiencies of the prior art, the application provides a medium-high-frequency low-loss MnZn ferrite material and a preparation method thereof.

[0006] The technical scheme of the application is as follows:

[0007] A preparation method of a medium-high-frequency low-loss MnZn ferrite material, comprising the following steps:

[0008] The MnZn ferrite particles or modified MnZn ferrite particles are pressed into a magnetic ring under 300-500 MPa, and then the magnetic ring is sintered in multiple sections, and after sintering, the magnetic ring is cooled to obtain a medium-high frequency low-loss MnZn ferrite material;

[0009] The multiple-section sintering is as follows: the magnetic ring is placed in a sintering device, heated to 350-450 DEG C at a rate of 1.5-2 DEG C / min, kept at 350-450 DEG C in air for 25-35 min, and then heated to 650-750 DEG C at a rate of 1.5-2 DEG C / min, and vacuumized; then heated to 980-1120 DEG C at a rate of 2-4 DEG C / min, kept at 980-1120 DEG C in vacuum for 25-35 min; and then heated to 1150-1250 DEG C at a rate of 2-3 DEG C / min, and nitrogen-oxygen mixed gas is introduced 10 min before reaching 1150-1250 DEG C, and kept at 1150-1250 DEG C in the nitrogen-oxygen mixed gas for 25-35 min.

[0010] According to the application, the MnZn ferrite particles are preferably existing materials, which can be prepared according to the published method or obtained by market.

[0011] According to the application, the modified MnZn ferrite particles are prepared as follows:

[0012] The MnZn ferrite particles and CaTiO3 powder are added into ethanol, the container containing the powder and ethanol is placed in a water bath crucible, and the powder is stirred at a water bath temperature of 50 DEG C and a rotation speed of 300 r / min for 2 h by using an electronic stirring rod; the ethanol is substantially completely volatilized; the stirred powder is dried in an oven at 80 DEG C for 45-75 min until the ethanol is completely volatilized; and the powder is cooled to room temperature to obtain the modified MnZn ferrite particles.

[0013] Further preferably, the mass ratio of the MnZn ferrite particles to CaTiO3 powder is 1000:(0.4-1.2); and the mass-volume ratio of the MnZn ferrite particles to ethanol is 65:(80-120) g / mL.

[0014] According to the application, the multiple-section sintering is as follows: the magnetic ring is placed in a sintering device, heated to 400 DEG C at a rate of 2 DEG C / min, kept at 400 DEG C in air for 30 min, and then heated to 700 DEG C at a rate of 2 DEG C / min, and vacuumized; then heated to 1100 DEG C at a rate of 3 DEG C / min, kept at 1100 DEG C in vacuum for 30 min; and then heated to 1150 DEG C at a rate of 3 DEG C / min, and nitrogen-oxygen mixed gas is introduced 10 min before reaching 1150 DEG C, and kept at 1150 DEG C in the nitrogen-oxygen mixed gas for 30 min.

[0015] Further preferably, the oxygen accounts for 3.5% in the nitrogen-oxygen mixed gas.

[0016] According to the application, the cooling is performed at a rate of 0.5-1.5 ℃ / min to 1100 ℃, then at a rate of 4-6 ℃ / min to 1000 ℃, and finally naturally to 200 ℃, while nitrogen gas is filled into the sintering equipment during the cooling until the cooling is completed.

[0017] The application also provides the medium-high frequency low-loss MnZn ferrite material prepared by the method.

[0018] The parts not described in detail in the application can be implemented according to the prior art.

[0019] The application has the following technical features and advantages:

[0020] 1. The preparation method provided by the application performs multi-section interval sintering on the magnetic ring pressed by the MnZn ferrite particles or the modified MnZn ferrite particles, controls the heating rate, heating environment, holding temperature, holding time, sintering temperature and sintering environment of the sintering process, changes the grain size of the MnZn ferrite material, limits the eddy current loss and the residual loss due to the reduction of the grain size, effectively improves the use performance of the MnZn ferrite material, solves the problems of high energy consumption in the production of the MnZn ferrite material and high loss of the conventional MnZn ferrite material at medium-high frequency, makes the medium-high frequency low-loss MnZn ferrite material prepared by the application have the characteristics of medium-high frequency and low loss, and provides a new idea for industrial production.

[0021] 2. The medium-high frequency low-loss MnZn ferrite material provided by the application has a loss of 118 mW·cm -3 and 122 mW·cm -3 at 500 kHz, 50 mT and 1 MHz, 30 mT, and can be used in the application field of medium-high frequency. In particular, the high-frequency low-loss MnZn ferrite material prepared by using the modified MnZn ferrite particles as raw materials has a loss of only 90 mW·cm -3 and 94 mW·cm -3 at 500 kHz, 50 mT and 1 MHz, 30 mT, which greatly reduces the use loss of the MnZn ferrite material. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The temperature curve diagram of the multi-section interval sintering in Examples 1-2.

[0023] Figure 2Temperature curve of the multi-stage interval sintering in the comparative example 1.

[0024] Figure 3 Temperature curve of the multi-stage interval sintering in the comparative example 2.

[0025] Figure 4 XRD pattern of the MnZn ferrite material prepared in the examples 1-2 and the comparative examples 1-2.

[0026] Figure 5 Cross-section morphology of the MnZn ferrite material prepared in the example 1.

[0027] Figure 6 Cross-section morphology of the MnZn ferrite material prepared in the example 2.

[0028] Figure 7 Cross-section morphology of the MnZn ferrite material prepared in the comparative example 1.

[0029] Figure 8 Cross-section morphology of the MnZn ferrite material prepared in the comparative example 2. DETAILED DESCRIPTION

[0030] The present application will be further described in the following specific examples and the accompanying drawings, but is not limited to the scope of the claimed protection. The raw materials used in the examples are all conventional raw materials, and the equipment used is all conventional equipment, which can be obtained from the market.

[0031] Among them, the MnZn ferrite particles are existing materials, which can be prepared according to the Production Process and Control Technology of Soft Magnetic Ferrite or obtained from the market.

[0032] Example 1

[0033] A preparation method of a medium-high frequency low-loss MnZn ferrite material, comprising the following steps:

[0034] The MnZn ferrite particles are pressed into a magnetic ring under 400 MPa, and then the magnetic ring is sintered in multiple stages and intervals;

[0035] As Figure 1As shown, the multi-stage interval sintering is specifically as follows: the magnetic ring is placed in a bell jar type vacuum atmosphere sintering furnace, heated to 400℃ at a rate of 2℃ / min, kept at 400℃ in air atmosphere for 30min, and then the furnace is vacuumized after being continuously heated to 700℃ at a rate of 2℃ / min; then heated to 1100℃ at a rate of 3℃ / min, kept at 1100℃ in vacuum for 30min; then heated to 1150℃ at a rate of 3℃ / min, and nitrogen-oxygen mixed gas is introduced 10min before reaching 1150℃, kept at 1150℃ in nitrogen-oxygen mixed gas for 30min; wherein the oxygen content in the nitrogen-oxygen mixed gas is 3.5%;

[0036] After sintering, cooling is performed;

[0037] The cooling is specifically as follows: the temperature is lowered to 1100℃ at a rate of 1℃ / min, then continuously lowered to 1000℃ at a rate of 5℃ / min, and finally naturally lowered to 200℃, while flowing nitrogen is filled into the sintering equipment during the cooling process until the cooling is completed;

[0038] After the cooling is completed, the ventilation is stopped, the furnace is opened, and the sample is taken out, thereby obtaining the medium-high frequency low-loss MnZn ferrite material.

[0039] The medium-high frequency low-loss MnZn ferrite material prepared in this embodiment is numbered as 1.

[0040] Example 2

[0041] A preparation method of a medium-high frequency low-loss MnZn ferrite material, including the following steps:

[0042] (1) 65g of MnZn ferrite and 0.078g of CaTiO3 powder are added to 100mL of ethanol, the container containing the powder and ethanol is placed in a water bath crucible, and the electronic stirring rod is stirred at a speed of 300r / min for 2h in a 50℃ water bath, and the ethanol is basically completely volatilized, the stirred powder is dried in an 80℃ oven for 60min until the ethanol is completely volatilized, and the powder is taken out and cooled to room temperature, thereby obtaining modified MnZn ferrite particles;

[0043] (2) the modified MnZn ferrite particles are pressed into a magnetic ring at 400MPa, and then the magnetic ring is subjected to multi-stage interval sintering;

[0044] As Figure 1As shown, the multi-stage interval sintering is specifically as follows: the magnetic ring is placed in a bell-type vacuum atmosphere sintering furnace, the temperature is raised to 400°C at a rate of 2°C / min, the temperature is kept at 400°C in an air atmosphere for 30 minutes, the temperature is further raised to 700°C at a rate of 2°C / min, and the furnace is vacuumed; then the temperature is raised to 1100°C at a rate of 3°C / min, and the temperature is kept at 1100°C in a vacuum for 30 minutes; then the temperature is raised to 1150°C at a rate of 3°C / min, and a nitrogen-oxygen mixture is introduced 10 minutes before reaching 1150°C, and the temperature is kept at 1150°C in the nitrogen-oxygen mixture for 30 minutes; wherein, the oxygen content in the nitrogen-oxygen mixture is 3.5%;

[0045] Cooling after sintering is completed;

[0046] The cooling is specifically as follows: cooling to 1100°C at a rate of 1°C / min, then continuing to cool to 1000°C at a rate of 5°C / min, and finally naturally cooling to 200°C, while flowing nitrogen is filled into the sintering equipment during the cooling process until cooling is completed;

[0047] After cooling is completed, ventilation is stopped, the furnace is opened and the sample is taken out to obtain a medium-high frequency low-loss MnZn ferrite material.

[0048] The medium-high frequency low-loss MnZn ferrite material prepared in this embodiment is numbered 2.

[0049] Comparative Example 1

[0050] A method for preparing a medium-high frequency, low-loss MnZn ferrite material, the steps are as described in Example 1, except that the multi-stage interval sintering is specifically as follows: placing the magnetic ring in a bell-type vacuum atmosphere sintering furnace, heating it to 400°C at a rate of 1°C / min, keeping it warm at 400°C in an air atmosphere for 60 minutes, and continuing to heat it to 700°C at a rate of 1°C / min, and then evacuating the furnace; then heating it to 1100°C at a rate of 3°C / min, keeping it warm at 1100°C in a vacuum for 60 minutes; then heating it to 1250°C at a rate of 1.5°C / min, introducing a nitrogen-oxygen mixture 10 minutes before reaching 1250°C, and keeping it warm at 1250°C in the nitrogen-oxygen mixture for 60 minutes; wherein the oxygen content in the nitrogen-oxygen mixture is 3.5%, specifically as follows Figure 2 shown.

[0051] The medium-high frequency low-loss MnZn ferrite material prepared in this comparative example is numbered 3.

[0052] Comparative Example 2

[0053] A preparation method of a medium-high frequency low-loss MnZn ferrite material, the steps are as shown in the embodiment 1, the difference is that the multi-section interval sintering is specifically: the magnetic ring is placed in a bell jar type vacuum atmosphere sintering furnace, heated to 400 DEG C at a rate of 1 DEG C / min, and kept at 400 DEG C for 60 min in air atmosphere, and then the furnace is vacuumized after heating to 700 DEG C at a rate of 1 DEG C / min; then heated to 1100 DEG C at a rate of 3 DEG C / min, and kept at 1100 DEG C for 60 min in vacuum; then heated to 1150 DEG C at a rate of 1.5 DEG C / min, and kept at 1150 DEG C for 60 min in nitrogen-oxygen mixed gas, wherein the oxygen content in the nitrogen-oxygen mixed gas is 3.5%, and the specific process is as shown in Figure 3 .

[0054] The medium-high frequency low-loss MnZn ferrite material prepared in the present comparative example is numbered as 4.

[0055] Test example

[0056] 1, the products prepared in the embodiments 1-2 and comparative examples 1-2 are characterized by XRD and loss (P cv ) test, and the results are shown in table 1 and Figure 4 .

[0057] The specific test method is: the loss P cv of the products prepared in the embodiments 1-2 and comparative examples 1-2 is tested at 500 kHz, 50 mT and 1 MHz, 30 mT by using power consumption instrument. The L s and R s of the products prepared in the embodiments 1-2 and comparative examples 1-2 are tested by using LCR tester, and the complex permeability and cutoff frequency f r are obtained by calculation.

[0058] Table 1, product performance of embodiments 1-2 and comparative examples 1-2

[0059]

[0060] As shown in table 1, compared with comparative examples 1-2, the loss of the medium-high frequency low-loss MnZn ferrite material prepared in the embodiments 1-2 at 500 kHz, 50 mT and 1 MHz, 30 mT is obviously reduced, the loss of the embodiment 1 is reduced to 118 mW·cm -3 and 122 mW·cm -3 , respectively, and the loss of the embodiment 2 is reduced to 90 mW·cm -3 and 94 mW·cm -3The performance of the product under the same test condition can be compared with that of the PC500 product of the Japanese TDK company, which shows that the preparation method provided by the application effectively improves the use performance of the MnZn ferrite material by controlling the heating rate, heating environment, holding temperature, holding time, sintering temperature and sintering environment of the sintering process, so that the medium-high frequency low-loss MnZn ferrite material prepared by the application has the characteristics of medium-high frequency and low loss, and at the same time solves the problems of high energy consumption in the production process of the MnZn ferrite material and high loss of the conventional MnZn ferrite material at medium-high frequency. And experiments prove that if the modified MnZn ferrite particles are used as raw materials, the loss at medium-high frequency will be further reduced.

[0061] And the medium-high frequency low-loss MnZn ferrite material prepared in Example 2 is modified by using CaTiO3 as an auxiliary component for the MnZn ferrite, so that Ca 2+ ions form a high-resistance layer at the grain boundary, improve the grain boundary resistivity, make the grain boundary obvious, refine the grain, and reduce the eddy current loss; Ti 4+ partially exists at the grain boundary and partially enters the crystal lattice, and the Ti 4+ that enters the crystal lattice will cause the B site of the MnZn ferrite to appear 2Fe 3+ →Fe 2+ +Ti 4+ transformation, not only increases Fe 2+ (K1>0), but also changes the magnetic field characteristics of the crystal because the ionic radius of Ti 4+ is larger than that of Fe 3+ , so that the magnetic crystal anisotropy has a significant K1>0 effect, further improves the magnetic permeability and the temperature coefficient of the magnetic permeability, reduces the eddy current loss and the hysteresis loss.

[0062] As Figure 4 can be seen, the samples prepared in Examples 1-2 and Comparative Examples 1-2 of the application have only one phase of MnZn ferrite after XRD detection, which shows that the preparation method provided by the application can successfully prepare the MnZn ferrite material.

[0063] 2, the morphology of the products prepared in Examples 1-2 and Comparative Examples 1-2 was observed by using an electron scanning electron microscope (SEM), and the results are shown in Figures 5 to 8 .

[0064] As Figures 5 to 8It can be seen that the grain size of the MnZn ferrite material prepared in Example 1 is obviously smaller than that in Comparative Examples 1-2, which is due to the change of the grain growth caused by the adjustment of the sintering process. The reduction of the grain size helps to reduce the eddy current loss and the residual loss, thereby reducing the loss of the MnZn ferrite material at medium and high frequencies. In Example 2, the grain size is further reduced compared with Example 1 due to the improvement of the sintering process and the addition of CaTiO3, which helps to reduce the total loss, and the addition of CaTiO3 helps to improve the magnetic properties of the material. 2+ ions and Ti 4+ The addition of ions changes the microstructure of the ferrite material, which changes the electromagnetic properties of the material and helps to reduce the loss.

[0065] Finally, it should be noted that the above description is only for the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify or equivalently replace the technical solutions of the present application without departing from the essence and scope of the present application.

Claims

1. A method for preparing a medium-high frequency low-loss MnZn ferrite material, characterized in that: The steps are as follows: The MnZn ferrite particles or modified MnZn ferrite particles are pressed into a magnetic ring at 300-500 MPa, and then the magnetic ring is sintered in multiple sections. After the sintering is completed, the magnetic ring is cooled to obtain a medium-high frequency low-loss MnZn ferrite material. The multi-stage interval sintering is as follows: placing the magnetic ring in a sintering device, heating it to 350-450°C at a rate of 1.5-2°C / min, keeping it warm at 350-450°C in an air atmosphere for 25-35 minutes, continuing to heat it to 650-750°C at a rate of 1.5-2°C / min and then evacuating; then heating it to 980-1120°C at a rate of 2-4°C / min, keeping it warm at 980-1120°C in a vacuum for 25-35 minutes; then heating it to 1150-1250°C at a rate of 2-3°C / min, introducing a nitrogen-oxygen mixture 10 minutes before reaching 1150-1250°C, and keeping it warm at 1150-1250°C in a nitrogen-oxygen mixture for 25-35 minutes.

2. The preparation method according to claim 1, wherein The modified MnZn ferrite particles are prepared according to the following method: MnZn ferrite particles and CaTiO3 powder are added to ethanol, and the container containing the powder and ethanol is placed in a water bath crucible. The mixture is stirred for 2 hours using an electronic stirring rod in a 50°C water bath at a rotation speed of 300 r / min until the ethanol is basically evaporated. The stirred powder is placed in an 80°C oven and dried for 45 to 75 minutes until the ethanol is completely evaporated. The mixture is then cooled to room temperature to obtain modified MnZn ferrite particles.

3. The preparation method according to claim 2, wherein The mass ratio of the MnZn ferrite particles to the CaTiO3 powder is 1000:(0.4-1.2); the mass volume ratio of the MnZn ferrite particles to ethanol is 65:(80-120), unit: g / mL.

4. The preparation method according to claim 1, wherein The multi-stage interval sintering is as follows: placing the magnetic ring in a sintering device, heating it to 400°C at a rate of 2°C / min, keeping it at 400°C in an air atmosphere for 30 minutes, continuing to heat it to 700°C at a rate of 2°C / min and then evacuating; then heating it to 1100°C at a rate of 3°C / min, keeping it at 1100°C in a vacuum for 30 minutes; then heating it to 1150°C at a rate of 3°C / min, introducing a nitrogen-oxygen mixture 10 minutes before reaching 1150°C, and keeping it at 1150°C in the nitrogen-oxygen mixture for 30 minutes.

5. The preparation method according to claim 4, wherein The oxygen content in the nitrogen-oxygen mixture is 3.5%.

6. The preparation method according to claim 1, wherein The cooling is as follows: cooling to 1100°C at a rate of 0.5-1.5°C / min, then continuing to cool to 1000°C at a rate of 4-6°C / min, and finally naturally cooling to 200°C. Simultaneously, flowing nitrogen is filled into the sintering equipment during the cooling process until cooling is completed.

7. A medium-high frequency low-loss MnZn ferrite material, characterized in that: It is prepared according to the preparation method according to any one of claims 1 to 6.

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