Low-temperature sintered high-frequency low-loss mnzn power ferrite and preparation method thereof

Abstract

The application discloses a low-temperature sintering high-frequency low-loss MnZn power ferrite, and belongs to the technical field of ferrite preparation. The MnZn power ferrite comprises main components and auxiliary components. The main components comprise 54.5-56.5 mol% Fe2O3 and 4.5-7.5 mol% ZnO, and the rest is MnO. The auxiliary components comprise 0.001-0.05 wt% Sb2O3, 0.01-0.03 wt% Nb2O5, 0.1-0.4 wt% Co2O3, 0.02-0.10 wt% CaCO3 and 0.00-0.01 wt% SiO2, and the pre-sintered material after pre-sintering of the main components is used as a reference. The Sb2O3 with high resistivity and low melting point is used as a fluxing agent in the application, the Sb2O3 replaces the traditional V2O5, the sintering temperature is reduced, the high-frequency loss of the MnZn ferrite is improved, and the low-temperature sintering MnZn ferrite has important significance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ferrite preparation, and particularly relates to a low-temperature sintering high-frequency low-loss MnZn power ferrite and a preparation method. BACKGROUND

[0002] With the industrial electronic products miniaturization and high frequency becoming mainstream, the integration of devices is getting higher and higher, and the corresponding magnetic components need to consider the performance under high frequency and the performance under wide temperature. Therefore, the main development direction of future MnZn power ferrite is high frequency and low loss and high temperature and low loss, and its important application fields cover new energy, cloud computing, 5G communication, Internet of Things and high-end consumer electronic products. It can be seen that the market demand is huge. The sintering temperature of MnZn ferrite is usually 1200-1300℃, the sintering period is as long as 26-36 hours, the holding time is about 4-8 hours, and nitrogen needs to be introduced during the sintering process to control the oxygen partial pressure. Therefore, the production of MnZn ferrite belongs to a high energy consumption industry. If the performance can be maintained, the sintering temperature can be reduced and the holding time can be shortened, the energy can be greatly saved, and more green production can be realized. Therefore, low-temperature sintering MnZn power ferrite is of great significance.

[0003] For low-temperature sintering high-frequency MnZn ferrite, a patent with the patent number CN 110937887 B discloses a high-frequency low-loss MnZn ferrite material and a preparation sintering method thereof. The main components include 68.5-73.5wt% Fe2O3, 2.5-5.5wt% ZnO, and the rest is Mn3O4. The auxiliary components, calculated based on the total weight of the main components, include CaCO3200-800ppm, V2O5200-600ppm, ZrO2100-500ppm, Nb2O5100-800ppm, Co2O31000-2500ppm, and NiO100-500. The application changes the pre-sintering temperature to control the activity of the pre-sintering material and reduce the sintering temperature. The sintering temperature of this method is about 1100℃. The optimal sample has an initial magnetic permeability μ0 of 980, a saturation magnetic induction Bs of 552mT, and a loss of 93kw / m3 at 1MHz and 50mT. i 3 ​(100℃). Chinese Patent No. CN 112456994 A discloses a "Low-Temperature Sintering High-Frequency Low-Loss MnZn Soft Magnetic Ferrite and its Preparation Method," in which the main components include 53.5–56.5 mol% Fe₂O₃, 3.2–5.5 mol% ZnO, and the remainder being MnO; the auxiliary components include 400–1000 ppm nano-CaCO₃, 100–350 ppm nano-Nb₂O₅, 400–1000 ppm nano-V₂O₅, 1500–3500 ppm nano-Co₂O₃, 30–150 nano-SiO₂, and 100–500 ppm nano-CuO. The sintering temperature of this method is approximately 1080℃, with a holding time of 6 hours and an oxygen partial pressure of 1.8%. The initial permeability μ of the sample at room temperature is... i The magnetic flux density is 975–1100 mT, the saturation magnetic flux density Bs is 545–550 mT, and the loss at 3 MHz and 80 mT is 6710–6930 kW / m. 3 (100℃), at 5MHz and 50mT, the loss is 7530~7730kw / m 3 (100℃). Professor Che Shenglei's team at Zhejiang University of Technology disclosed a method for low-temperature sintering of MnZn power ferrites (Ying Y, Xiong XB, Wang NC, et al. Low temperature sintered MnZn ferrites for power applications at the frequency of 1MHz[J]. Journal of the European Ceramic Society, 2021, 41(12): 5924-5930.). This method involves adding low-melting-point LiBO2 (melting point 845℃) during the sintering process to form a sintering with a liquid phase, thereby reducing the sintering temperature. Studies have shown that the sintered sample exhibits the best magnetic properties when the LiBO2 addition is 500ppm and the sintering temperature is 1020℃, with a loss of 310kW / m under test conditions of 1MHz and 30mT. 3 (25℃).

[0004] In summary, lowering the sintering temperature and improving the high-frequency performance of MnZn ferrite can be achieved through methods such as pre-sintering temperature, doping with low-melting-point oxides, and nanoscale oxide doping. Appropriate processes can yield better performance. The most common method is to use low-melting-point oxides as fluxes to achieve sintering with a liquid phase. V₂O₅ (melting point 690℃) is the most widely used flux in conventional MnZn ferrite sintering, but it is a highly toxic oxide. Therefore, finding a flux that can achieve low-temperature sintering, high frequency, low loss, and is environmentally friendly has significant practical value. Summary of the Invention

[0005] The application aims at the problems in the prior art, and provides a low-temperature sintering high-frequency low-loss MnZn power ferrite and a preparation method. 9 Ω·cm) and a low melting point (655 DEG C), the Sb2O3 is used to replace the traditional V2O5, which is of great significance for the low-temperature sintering MnZn ferrite to reduce the sintering temperature and improve the high-frequency loss.

[0006] To achieve the above object, the technical scheme adopted by the application is as follows:

[0007] The low-temperature sintering high-frequency low-loss MnZn power ferrite comprises main components and auxiliary components; the main components comprise, in terms of oxide mole percentage, 54.5-56.5 mol% Fe2O3 and 4.5-7.5 mol% ZnO, and the rest is MnO; and the auxiliary components comprise, based on the mass of the pre-sintered material after pre-sintering of the main components, 0.001-0.05 wt% Sb2O3, 0.01-0.03 wt% Nb2O5, 0.1-0.4 wt% Co2O3, 0.02-0.10 wt% CaCO3 and 0.00-0.01 wt% SiO2.

[0008] The pre-sintered material is prepared by the following process: Fe2O3, ZnO and MnO are used as raw materials, and the raw materials are calculated and weighed according to the main components of 54.5-56.5 mol% Fe2O3 and 4.5-7.5 mol% ZnO, with the rest being MnO; the weighed raw materials are placed in a planetary ball mill, deionized water is added, and one-time ball milling is performed under the condition that the ball milling speed is 245-255 r / min, the ball milling time is 3-4 hours, and the ball milling medium is a steel ball with a diameter of 5 mm; after the ball milling is completed, the obtained slurry is dried at 85 DEG C for 24 hours, and then sieved through a 40-50 mesh sieve to obtain a first ground powder; the obtained first ground powder is placed in a bell jar furnace, and pre-sintering is performed in an air atmosphere, the pre-sintering temperature is 800-900 DEG C, and the pre-sintering time is 2 hours; after the pre-sintering is completed, the pre-sintered powder is sieved through a 40-50 mesh sieve.

[0009] The preparation method of the low-temperature sintering high-frequency low-loss MnZn power ferrite comprises the following steps:

[0010] Step 1, batching:

[0011] Fe2O3, ZnO and MnO are used as raw materials, and the raw materials are calculated and weighed according to the main components of 54.5-56.5 mol% Fe2O3 and 4.5-7.5 mol% ZnO, with the rest being MnO;

[0012] Step 2, first ball milling:

[0013] The raw materials weighed in step 1 are placed in a planetary ball mill, deionized water is added, and first ball milling is performed at a ball mill speed of 245-255 r / min, a ball milling time of 3-4 hours, and a ball milling medium of Ф5 mm steel balls; after the ball milling is completed, the obtained slurry is dried at 85°C for 24 hours, and then sieved through a 40-50 mesh sieve to obtain a first-milling powder;

[0014] Step 3, pre-sintering:

[0015] The first-milling powder obtained in step 2 is placed in a bell jar furnace, and pre-sintering is performed in an air atmosphere at a pre-sintering temperature of 800-900°C for 2 hours; after the pre-sintering is completed, the pre-sintered powder is sieved through a 40-50 mesh sieve to obtain a pre-sintered powder;

[0016] Step 4, second ball milling:

[0017] The mass of the pre-sintered powder obtained in step 3 is taken as a basis, and “0.001-0.05wt% Sb2O3, 0.01-0.03wt% Nb2O5, 0.1-0.4wt% Co2O3, 0.02-0.10wt% CaCO3, and 0.00-0.01wt% SiO2” are added to the pre-sintered powder as auxiliary components to obtain a mixed powder;

[0018] Step 5, second ball milling:

[0019] The mixed powder obtained in step 4 is placed in a planetary ball mill, deionized water is added, and ball milling is performed for 6-8 hours using a ball milling medium of Ф5 mm bearing steel; after the ball milling is completed, the obtained slurry is dried at 85°C for 24 hours to obtain a second-milling powder;

[0020] Step 6, granulation:

[0021] The second-milling powder obtained in step 5 is granulated by adding 11.5-14.5wt% PVA, and after being left to dry naturally, a granulated powder with good flowability is obtained;

[0022] Step 7, forming:

[0023] The granulated powder obtained in step 6 is pressed into a circular ring with an inner diameter x outer diameter x height of 14mm x 8mm x 4mm at a pressing pressure of 150-170MPa, and a green body density of 3.1-3.2g / cm3 is obtained; 3 ;

[0024] Step 8, sintering:

[0025] The green body obtained in step 7 is subjected to balanced oxygen partial pressure sintering to obtain the MnZn power ferrite; wherein the process of balanced oxygen partial pressure sintering is:

[0026] First stage: after putting the green body, the temperature is increased to 500-600 DEG C at the temperature increasing rate of 1-2 DEG C / min under the air atmosphere, and this stage is the standard degassing stage;

[0027] Second stage: the temperature is increased to 900 DEG C at the temperature increasing rate of 2-3 DEG C / min under the air atmosphere, and the temperature is kept for 2 hours, and this stage is the enhanced degassing stage;

[0028] Third stage: the temperature is increased to 1050-1100 DEG C at the temperature increasing rate of 2-3 DEG C / min under the air atmosphere, the oxygen partial pressure is adjusted to 1.5-1.7%, and the temperature is kept for 5-8 hours, and this stage is the sintering stage;

[0029] Fourth stage: after the sintering keeping is finished, the temperature is decreased from 1050-1100 DEG C to 500 DEG C, and the oxygen partial pressure is decreased from 1.5-1.7% to 0%; finally, the temperature is naturally cooled to room temperature from 500 DEG C under the pure nitrogen atmosphere, and this stage is the temperature decreasing stage.

[0030] Compared with the prior art, the low-temperature sintering high-frequency low-loss MnZn power ferrite and the preparation method have the beneficial effects that:

[0031] The low-temperature sintering high-frequency low-loss MnZn power ferrite and the preparation method have the beneficial effects that: 1) lower melting point, the melting point of V2O5 is 690 DEG C, the boiling point is 1750 DEG C, the melting point of Sb2O3 is 655 DEG C, and the boiling point is 1425 DEG C; 2) higher resistivity, the resistivity of V2O5 is 10 2 ~10 3 Ω·cm at normal temperature, the resistivity of Sb2O3 is 10 9 Ω·cm, and 3) more environmentally friendly, V2O5 is a toxic metal oxide, and the toxicity of Sb2O3 is far lower than that of V2O5. The low-temperature sintering high-frequency low-loss MnZn power ferrite and the preparation method have the beneficial effects that: BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is the SEM graph of the section of the MnZn ferrite obtained by the comparative example 1;

[0033] Figure 2 It is the SEM graph of the section of the MnZn ferrite obtained by the embodiment 1 of the application;

[0034] Figure 3 It is the SEM graph of the section of the MnZn ferrite obtained by the embodiment 2 of the application;

[0035] Figure 4SEM image of a cross section of the MnZn ferrite obtained in Example 3 of the present application;

[0036] Figure 5 Curve of average grain size of the samples obtained in Comparative Example 1 and Examples 1-3;

[0037] Figure 6 Loss temperature curve of the samples obtained in Comparative Example 1 and Examples 1-3 under test conditions of 1 MHz, 50 mT;

[0038] Figure 7 Curve of direct current resistance of the samples obtained in Comparative Example 1 and Examples 1-3. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described in detail below in combination with the drawings and examples.

[0040] The present application provides a low-temperature sintered high-frequency low-loss MnZn power ferrite and a preparation method. The samples of Examples 1-3 and Comparative Examples 1-3 are prepared by the following steps:

[0041] Step 1, main component batching:

[0042] Fe2O3, ZnO and MnO are used as raw materials, and the raw materials are calculated and weighed according to the proportions of "55.5 mol% Fe2O3, 6.0 mol% ZnO, 38.5 mol% MnO";

[0043] Step 2, first ball milling:

[0044] The raw materials weighed in Step 1 are placed in a planetary ball mill, deionized water is added, and first ball milling is carried out under the condition that the ball milling speed is 250 r / min, the ball milling time is 3 hours, and the ball milling medium is Ф5 mm steel ball; after ball milling, the obtained slurry is dried at 85℃ for 24 hours, then sieved through a 50 mesh sieve to obtain a first-milling powder;

[0045] Step 3, pre-sintering:

[0046] The first-milling powder obtained in Step 2 is placed in a bell jar furnace, and pre-sintering is carried out in an air atmosphere, the pre-sintering temperature is 890℃, the pre-sintering time is 2 hours, and after pre-sintering, the pre-sintered powder is sieved through a 50 mesh sieve;

[0047] Step 4, second ball milling:

[0048] The mass of the pre-sintered material obtained in Step 3 is used as a reference, and the auxiliary components shown in Table 1 are added to the pre-sintered material to obtain a mixed powder;

[0049] Table 1 Component Proportion of Auxiliary Components

[0050]

[0051] It is worth noting that Sb203 in Comparative Examples 2-3 is replaced by V2O5.

[0052] Step 5, secondary ball milling:

[0053] The mixed powder obtained in Step 4 is placed in a planetary ball mill, deionized water is added, and ball milling is performed for 7 hours with a ball milling medium of Ф5mm bearing steel. After the ball milling is completed, the obtained slurry is dried at 85°C for 24 hours to obtain a secondary ball milling material;

[0054] Step 6, granulation:

[0055] The secondary ball milling material obtained in Step 5 is granulated by adding 12.5wt% PVA, and after natural drying, a granulated material with good flowability is obtained;

[0056] Step 7, molding:

[0057] The granulated material obtained in Step 6 is pressed into a circular ring with an inner diameter x outer diameter x height of 14mm x 8mm x 4mm, and the pressing pressure is 160MPa. The green density of the obtained green body is 3.1-3.2g / cm 3 ;

[0058] Step 8, sintering:

[0059] The green body obtained in Step 7 is subjected to balanced oxygen partial pressure sintering to obtain the MnZn power ferrite; wherein the process of balanced oxygen partial pressure sintering is as follows:

[0060] First stage: after placing the green body, the temperature is raised to 600°C at a heating rate of 1.25°C / min in an air atmosphere, and this stage is a standard degassing stage;

[0061] Second stage: the temperature is raised to 900°C at a heating rate of 2°C / min in an air atmosphere, and the temperature is maintained for 2 hours, and this stage is an enhanced degassing stage;

[0062] Third stage: the temperature is raised to 1100°C at a heating rate of 2°C / min in an air atmosphere, the oxygen partial pressure is adjusted to 1.6%, and the temperature is maintained for 7 hours, and this stage is a sintering stage;

[0063] Fourth stage: after the sintering and maintaining is completed, the temperature is lowered from 1100°C to 500°C, and at the same time, the oxygen partial pressure is lowered from 1.6% to 0%; finally, in a pure nitrogen atmosphere, the temperature is naturally cooled from 500°C to room temperature, and this stage is a cooling stage.

[0064] The starting magnetic permeability μ of the sample is measured using the same Hui TH2826 LCR digital bridge iTest; the saturation magnetic induction intensity Bs and the volume power loss Pcv of the sample were tested by using rockzaki SY-8218B-H analyzer; the sintering density d of the sample was tested by using drainage method. The test results of examples 1-3 and comparative examples 1-3 are shown in table 2:

[0065] Table 2 test results of examples 1-3 and comparative examples 1-3

[0066]

[0067]

[0068] It can be known through test that the grain growth can be promoted by adding Sb2O3, because of the low melting point characteristic of Sb2O3, liquid phase appears in the sintering process, sintering with liquid phase is formed, because the material migration of liquid phase flow is faster than solid phase diffusion and the diffusion coefficient of ion in liquid phase is large, therefore the interface reaction and the material migration between particles are faster than that of sintering without solid phase, adding Sb2O3 can be beneficial to complete solid phase reaction at lower sintering temperature.

[0069] Figure 5 The average grain size curve of the samples obtained from comparative example 1 and examples 1-3; from Figure 5 It can be known that the average grain size increases with the increase of Sb2O3 fluxing agent, and the uniformity is best when the adding amount is 0.01wt%. Figure 6 The loss temperature curve of the samples obtained from comparative example 1 and examples 1-3 under the test condition of 1MHZ, 50mT; from Figure 6 It can be known that the loss of the sample at high frequency significantly decreases after adding Sb2O3, because of the high resistivity characteristic of Sb2O3, the high frequency loss of MnZn ferrite is reduced.

Claims

1. A low-temperature sintered high-frequency, low-loss MnZn power ferrite, characterized in that, It includes main components and auxiliary components; wherein, the main components, based on the molar percentage of oxides, include: 55.5 mol% Fe2O3, 6 mol% ZnO, and 38.5 mol% MnO; based on the mass of the pre-calcined material after pre-calcination of the main components, the auxiliary components include: 0.01 wt% Sb2O3, 0.025 wt% Nb2O5, 0.3 wt% Co2O3, 0.08 wt% CaCO3, and 0.005 wt% SiO2; The pre-calcined material is prepared by the following process: Fe2O3, ZnO and MnO are used as raw materials, and the raw materials are calculated and weighed according to the ratio of "55.5 mol% Fe2O3, 6 mol% ZnO and 38.5 mol% MnO"; the weighed raw materials are ball-milled, dried and sieved to obtain a first-mill powder; the first-mill powder is pre-calcined in air atmosphere at a pre-calcination temperature of 800-900℃ for 2 hours, and then sieved after pre-calcination to obtain the pre-calcined material.

2. A method for preparing low-temperature sintered high-frequency, low-loss MnZn power ferrite, characterized in that, Includes the following steps: Step 1, Ingredients: Using Fe2O3, ZnO, and MnO as raw materials, calculate and weigh the raw materials according to the ratio of "55.5 mol% Fe2O3, 6 mol% ZnO, and 38.5 mol% MnO"; Step 2, First ball milling: The raw materials weighed in step 1 are subjected to ball milling once. The ball milling speed is 245-255 r / min and the ball milling time is 3-4 hours. After the ball milling is completed, the raw materials are dried and sieved to obtain the first-milled powder. Step 3, Preheating: The powder obtained in step 2 is pre-calcined at a temperature of 800-900℃ for 2 hours. After pre-calcination, it is sieved to obtain the pre-calcined material. Step 4, Second Grinding and Batching: Using the mass of the pre-fired material obtained in step 3 as a benchmark, add "0.01wt% Sb2O3, 0.025wt% Nb2O5, 0.3wt% Co2O3, 0.08wt% CaCO3 and 0.005wt% SiO2" as auxiliary components to the pre-fired material to obtain a mixed powder. Step 5, Secondary ball milling: The mixed powder obtained in step 4 is subjected to a second ball milling for 6 to 8 hours. After the ball milling is completed, it is dried to obtain the secondary ball milled material. Step 6, Granulation: The secondary ball milling material obtained in step 5 is granulated to obtain granulated material; Step 7, Shaping: The granulated material obtained in step 6 is pressed into green body with a pressing pressure of 150-170 MPa. Step 8, Sintering: The green body obtained in step 7 is subjected to equilibrium oxygen partial pressure sintering to obtain the MnZn power ferrite; wherein, the equilibrium oxygen partial pressure sintering process is as follows: First stage: After placing the green body in the air, raise the temperature to 500-600℃; Second stage: Continue to raise the temperature to 900℃ and keep it warm for 2 hours; The third stage: continue to raise the temperature to 1050-1100℃, adjust the oxygen partial pressure to 1.5-1.7%, hold for 5-8 hours, and then sinter. Fourth stage: After sintering and heat preservation, the temperature is reduced from 1050-1100℃ to 500℃, and the oxygen partial pressure is reduced from 1.5-1.7% to 0%. Finally, under a pure nitrogen atmosphere, the temperature is naturally cooled from 500℃ to room temperature.

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