Soft magnetic ferrite material and preparation method thereof

Abstract

The invention provides a manganese zinc ferrite material and a preparation method thereof, and belongs to the technical field of electronic component materials. The manganese zinc ferrite material is prepared from main components and auxiliary components, based on the total mass of the main components being 100%, the main components comprise 38-72 wt% of Fe2O3, 5-9 wt% of ZnO and the balance MnO2; the auxiliary components comprise the following components in percentage by mass accounting for the total mass of the main components: 2500 ppm to 2500 ppm of SnO, 400 ppm to 2500 ppm of Co3O4, 500 ppm to 2500 ppm of In2O3 and 2500 ppm to 2500 ppm of TiO2; the grain size distribution of the manganese zinc ferrite material is 2-5 microns, and the density is greater than or equal to 95%. The manganese zinc ferrite material provided by the invention has the advantages of fine grain structure, uniform grain size, high density, higher working frequency and lower power loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic component materials, and particularly relates to a manganese-zinc ferrite material and a preparation method thereof. Background Art

[0002] Manganese-zinc ferrite is mainly used for preparing various inductors, transformers, filters and chokes, and is an important component material, which is widely used in modern power and electronic information fields, such as computers and their peripheral devices, office automation devices, digital communication and analog communication devices, the Internet, household appliances, electromagnetic compatibility devices, green lighting devices, industrial automation and automotive, aviation, aerospace and military fields. Manganese-zinc ferrite is sintered at high temperature by oxides such as iron oxide, zinc oxide, and manganese oxide. Since its resistivity is several orders of magnitude higher than that of other soft magnetic materials, it can effectively suppress the generation of high-frequency eddy currents, so that the working frequency of the ferrite is greatly improved compared with that of metal-based soft magnetic materials.

[0003] With the rapid development of the third-generation semiconductors, the working frequency of power devices has been increased to MHz, and electronic components such as inductors and transformers are also developing towards high frequency and miniaturization. This requires manganese-zinc ferrite to have a higher working frequency and lower power loss. By reducing the grain size of the ferrite to the single-domain state (≤5 μm), the high-frequency domain wall resonance of the manganese-zinc ferrite can be effectively eliminated, thereby increasing the working frequency and reducing the loss.

[0004] Traditional technologies mainly reduce the grain size of manganese-zinc ferrite by doping grain growth inhibitors, reducing the sintering temperature, etc. However, the existing technical methods generally use pre-sintered powder with a particle size of ≤0.5 μm to increase the sintering activity by increasing the powder surface area, and their sintering temperature is generally still higher than 1100 °C. The too high sintering temperature will lead to abnormal grain growth (the grain size will reach more than 20 μm), uneven grain size, and high porosity, thus deteriorating the high-frequency magnetic properties of the material. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a manganese-zinc ferrite material and a preparation method thereof. The manganese-zinc ferrite material provided by the present invention has a fine crystal structure (grain size of 2-5 μm), uniform grain size, high density (i.e., low porosity), and at the same time has a higher working frequency and lower power loss.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The present invention provides a manganese-zinc ferrite material, and the preparation raw materials include main components and auxiliary components; based on the total mass of the main components being 100%, the main components include: Fe 2 O 368 to 72 wt%, ZnO 5 to 9 wt%, MnO 2 the balance;

[0008] In terms of the percentage of the total mass of the main components, the secondary components include: SnO 2 500 to 2500 ppm, Co 3 O 4 400 to 2500 ppm, In 2 O 3 500 to 2500 ppm, TiO 2 500 to 2500 ppm;

[0009] The grain size of the manganese-zinc ferrite material is distributed in 2 to 5 μm, and the relative density is ≥95%.

[0010] Preferably, the total mass of the secondary components is ≤1 wt% of the total mass of the main components.

[0011] Preferably, the cut-off frequency of the manganese-zinc ferrite material is ≥5 MHz, the initial permeability is >600, and the loss at 5 MHz and 30 mT is ≤2000 kW / m 3 .

[0012] The present invention provides a preparation method of the manganese-zinc ferrite material described in the above solution, including the following steps:

[0013] Mix and ball-mill the main components and the secondary components to obtain a ball-milled material;

[0014] Pre-burn the ball-milled material to obtain a pre-burned material; the temperature of the pre-burning is 1100 to 1300 °C;

[0015] Crush and screen the pre-burned material in sequence to obtain a mixed powder;

[0016] Mix the mixed powder and an activation solvent, activate and granulate to obtain a granular material; the activation solvent includes water, a binder and an acidic activator;

[0017] Mold the granular material to obtain a blank;

[0018] Sinter the blank to obtain a manganese-zinc ferrite material; the temperature of the sintering is 850 to 1000 °C.

[0019] Preferably, the particle size of the mixed powder is 2 to 5 μm.

[0020] Preferably, the heat preservation time of the pre-burning is 1 to 3 h; the heat preservation time of the sintering is 4 to 10 h.

[0021] Preferably, the total mass of the activation solvent is 5 to 15% of the mass of the mixed powder.

[0022] Preferably, the acidic activator includes acid ammonium salt; the binder includes polyvinyl alcohol; in the activation solvent, the concentration of the binder is 3-10 wt%, and the concentration of the acidic activator is 1-5 wt%.

[0023] Preferably, the density of the blank is 3.0-3.8 g / cm 3 .

[0024] Preferably, the oxygen partial pressure of the sintering is <2%.

[0025] The present invention provides a manganese-zinc ferrite material, and the preparation raw materials include main components and auxiliary components; based on the total mass of the main components being 100%, the main components include: Fe 2 O 3 68-72 wt%, ZnO 5-9 wt%, MnO 2 the balance; based on the percentage of the total mass of the main components, the auxiliary components include: SnO 2 500-2500 ppm, Co 3 O 4 400-2500 ppm, In 2 O 3 500-2500 ppm, TiO 2 500-2500 ppm; the grain size of the manganese-zinc ferrite material is distributed in 2-5 μm, and the relative density is ≥95%. The present invention uses the main components as the magnetic source and adjusts the components by adding auxiliary components. The two are combined to obtain a manganese-zinc ferrite material with the advantages of high resistivity and low coercive force.

[0026] The present invention provides a preparation method of the manganese-zinc ferrite material described in the above scheme. By high-temperature pre-sintering (1100-1300 °C), the crystallinity and spinel phase purity of the pre-sintered material can be improved (the spinel phase is the crystal structure of ferrite), and the existence of other impurity oxides is avoided. After the sieved mixed powder is surface-activated by an acidic activator, even if the specific surface area of the mixed powder is small, it has sufficient sintering activity and can be sintered below 1000 °C and densified; at the same time, the grain size of the obtained manganese-zinc ferrite material still remains in 2-5 μm, avoiding abnormal grain growth and effectively maintaining the single-domain structure, so as to ensure the acquisition of the high cut-off frequency of the manganese-zinc ferrite material.

[0027] The traditional method is low-temperature pre-sintering + high-temperature secondary sintering. The powder obtained by low-temperature pre-sintering has high activity, but poor crystallinity and spinel phase purity. High-temperature secondary sintering is required to improve the purity and crystallinity to obtain high magnetic properties. However, when high-activity powder is sintered at high temperature, the grains are very easy to grow abnormally, which will instead deteriorate the magnetic properties. The present invention adopts the method of high-temperature pre-sintering + low-temperature secondary sintering. The powder obtained by high-temperature pre-sintering has good crystallinity and high purity, but poor sintering activity. By activating the surface of the pre-sintered powder, the sintering activity is improved, and sintering densification can be carried out at low temperature, and the grain size will not grow abnormally, which is beneficial to obtaining a manganese-zinc ferrite material with high-frequency magnetic properties.

[0028] Furthermore, the present invention activates the surface of the powder by adding an acidic activator. The acidic activator undergoes some slight chemical reactions with the surface of the mixed powder, so that the mixed powder exposes a fresh surface, increases the surface defect concentration, and further improves the sintering activity, enabling it to sinter at low temperature, thereby avoiding abnormal grain growth and having a high density at the same time. Brief Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is the scanning electron microscope image of the manganese-zinc ferrite material obtained in Example 1 of the present invention;

[0031] Figure 2 It is the scanning electron microscope image of the ferrite material prepared in Comparative Example 1 (traditional solid-phase sintering method). Detailed Embodiments

[0032] The present invention provides a manganese-zinc ferrite material, and the preparation raw materials include main components and sub-components; taking the total mass of the main components as 100%, the main components include: Fe 2 O 3 68 - 72 wt%, ZnO 5 - 9 wt%, MnO 2 the balance;

[0033] The mass content of each component in the sub-components relative to the total mass of the main components is: SnO 2 500 - 2500 ppm, Co 3 O 4 400 - 2500 ppm, In 2 O 3 500 - 2500 ppm, TiO2 500 - 2500 ppm;

[0034] The grain size of the manganese - zinc ferrite material is distributed within 2 - 5 μm, and the relative density ≥ 95%.

[0035] Based on the total mass of the main components being 100%, the main components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include 68 - 72 wt% of Fe 2 O 3 , and in the embodiments of the present invention, it can specifically be 68 wt%, 69 wt%, 70 wt%, 71 wt% or 72 wt%.

[0036] Based on the total mass of the main components being 100%, the main components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include 5 - 9 wt% of ZnO, and in the embodiments of the present invention, it can specifically be 5 wt%, 5.5 wt%, 6 wt%, 7 wt%, 8 wt% or 9 wt%.

[0037] Based on the total mass of the main components being 100%, the main components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include the balance of MnO 2 .

[0038] Based on the percentage of the total mass of the main components, the secondary components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include 500 - 2500 ppm of SnO 2 , and in the embodiments of the present invention, it can specifically be 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm or 2500 ppm.

[0039] Based on the percentage of the total mass of the main components, the secondary components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include 400 - 2500 ppm of Co 3 O 4 , and in the embodiments of the present invention, it can specifically be 400 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm or 2500 ppm.

[0040] Based on the percentage of the total mass of the main components, the secondary components in the raw materials for preparing the manganese - zinc ferrite material provided by the present invention include 500 - 2500 ppm of In 2 O 3, in the embodiments of the present invention, it may specifically be 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm or 2500 ppm.

[0041] Calculated as a percentage of the total mass of the main components, the secondary components in the raw materials for preparing the manganese-zinc ferrite material provided by the present invention include 500-2500 ppm of TiO 2 , in the embodiments of the present invention, it may specifically be 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm or 2500 ppm.

[0042] In the present invention, the total mass of the secondary components is preferably ≤1 wt% of the total mass of the main components. In the embodiments of the present invention, it may specifically be 1 wt%, 0.7 wt%, 0.57 wt%, 0.38 wt%, 0.19 wt%, 0.15 wt% or 0.1 wt%.

[0043] In the present invention, the grain size of the manganese-zinc ferrite material is distributed in 2-5 μm, the relative density is ≥95%, the cut-off frequency is preferably ≥5 MHz, the initial permeability is preferably >600, and the loss at 5 MHz and 30 mT is preferably ≤2000 kW / m 3 .

[0044] The present invention uses the main components as the magnetic source and adjusts the composition by adding secondary components. The combination of the two results in a manganese-zinc ferrite material with the advantages of high resistivity and low coercivity.

[0045] The present invention provides a method for preparing the above-mentioned manganese-zinc ferrite material, comprising the following steps:

[0046] Mix and ball-mill the main components and secondary components to obtain a ball-milled material;

[0047] Pre-sinter the ball-milled material to obtain a pre-sintered material; the temperature of the pre-sintering is 1100-1300 °C;

[0048] Crush and screen the pre-sintered material in sequence to obtain a mixed powder;

[0049] Mix the mixed powder and an activating solvent, activate and granulate to obtain a granular material; the activating solvent includes water, a binder and an acidic activator;

[0050] Mold the granular material to obtain a green body;

[0051] Sinter the green body to obtain a manganese-zinc ferrite material; the temperature of the sintering is 850-1000 °C.

[0052] Unless otherwise specified, the raw materials and equipment used in the present invention are all commercially available products.

[0053] In the present invention, the main component and the auxiliary component are mixed and ball-milled to obtain a ball-milled material.

[0054] In the present invention, the rotation speed of the mixed ball milling is preferably 200 - 500 r / min. In the embodiments of the present invention, it can specifically be 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, or 500 r / min; the time of the mixed ball milling is preferably 3 - 10 h. In the embodiments of the present invention, it can specifically be 3 h, 5 h, 8 h, or 10 h. In the present invention, the particle size of the ball-milled material is preferably < 0.5 μm

[0055] After obtaining the ball-milled material, the present invention pre-sinter the ball-milled material to obtain a pre-sintered material.

[0056] In the present invention, the temperature of the pre-sintering is 1100 - 1300 °C. In the embodiments of the present invention, it can specifically be 1100 °C, 1150 °C, 1200 °C, 1250 °C, or 1300 °C; the heat preservation time of the pre-sintering is preferably 1 - 3 h. In the embodiments of the present invention, it can specifically be 1 h, 2 h, or 3 h. The present invention preferably heats up from room temperature to the temperature of the pre-sintering at a rate of 200 - 300 °C / h. In the embodiments of the present invention, it can specifically be 200 °C / h, 250 °C / h, or 300 °C / h. In the present invention, the atmosphere of the pre-sintering is preferably a nitrogen atmosphere. By adopting a nitrogen atmosphere, the present invention can avoid the oxidation of Fe 2+ and Mn 2+ from generating plasma oxidation.

[0057] After completing the pre-sintering, the present invention preferably cools the obtained material in the furnace to room temperature.

[0058] After obtaining the pre-sintered material, the present invention sequentially crushes and sieves the pre-sintered material to obtain a mixed powder.

[0059] In the present invention, the crushing preferably includes mechanical crushing and jet milling. The present invention does not particularly limit the methods of mechanical crushing and jet milling, and they can be set according to the performance of the equipment. In the present invention, the particle size of the mixed powder is preferably 2 - 5 μm. The particle size of the mixed powder in the present invention is close to the grain size of the final product. In the traditional process, it is required that the particle size of the powder after pre-sintering is less than 1 μm or even finer, so as to improve the sintering activity and facilitate obtaining a dense product. However, if the original particle size is too fine and the activity is too high, abnormal grain growth is likely to occur during sintering. The present invention controls the particle size of the mixed powder within 2 - 5 μm. The sintering activity of the powder itself is low, and then the sintering activity is improved by activating the powder, so that both the density can be increased and the abnormal grain growth can be inhibited.

[0060] After obtaining the mixed powder, the present invention mixes the mixed powder with an activating solvent, activates and granulates it to obtain granular material.

[0061] In the present invention, the activating solvent includes water, a binder and an acidic activator; the acidic activator preferably includes acid ammonium salts; the acid ammonium salts preferably include ammonium nitrate, ammonium carbonate or ammonium bicarbonate; the binder preferably includes polyvinyl alcohol.

[0062] In the present invention, the total mass of the activating solvent is 5 - 15% of the mass of the mixed powder. In the embodiments of the present invention, it can specifically be 5%, 8%, 10%, 12% or 15%; in the activating solvent, the concentration of the binder is preferably 3 - 10 wt%, and in the embodiments of the present invention, it can specifically be 3 wt%, 5 wt%, 6 wt%, 8 wt% or 10 wt%; the concentration of the acidic activator is preferably 1 - 5 wt%, and in the embodiments of the present invention, it can specifically be 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%.

[0063] The present invention performs surface activation on the powder by adding an acidic activator. The acidic activator undergoes some slight chemical reactions with the surface of the mixed powder, so that the mixed powder exposes a fresh surface, increases the surface defect concentration, and further improves the sintering activity, enabling it to sinter at low temperature, thereby avoiding abnormal grain growth and having a high density at the same time.

[0064] By adding a binder in the present invention, the green body can have a certain strength when pressing the green body.

[0065] After obtaining the granular material, the present invention forms the granular material to obtain a green body.

[0066] In the present invention, the forming includes pressing forming; the pressure for forming is preferably 400 - 600 MPa, and in the embodiments of the present invention, it can specifically be 400 MPa, 450 MPa, 500 MPa, 550 MPa or 600 MPa; the pressure holding time for forming is preferably 30 s. In the present invention, the density of the blank is preferably 3.0 - 3.8 g / cm 3 , and in the embodiments of the present invention, it can specifically be 3.0 g / cm 3 , 3.2 g / cm 3 , 3.5 g / cm 3 or 3.8 g / cm 3 .

[0067] After obtaining the blank, the present invention sinters the blank to obtain a manganese-zinc ferrite material.

[0068] In the present invention, the temperature for sintering is 850 - 1000 °C, and in the embodiments of the present invention, it can specifically be 850 °C, 880 °C, 900 °C, 950 °C, 980 °C or 1000 °C; the heat preservation time for sintering is preferably 4 - 10 h, and in the embodiments of the present invention, it can specifically be 4 h, 6 h, 8 h or 10 h; the oxygen partial pressure for sintering < 2%. The present invention preferably adds nitrogen to make the oxygen partial pressure < 2%. By maintaining the oxygen partial pressure < 2% during sintering, the present invention can maintain the spinel phase of the ferrite and avoid the formation of other oxide impurities.

[0069] After completing the sintering, the present invention preferably cools the obtained material and takes it out of the furnace.

[0070] The present invention can improve the crystallinity and spinel phase purity of the pre-sintered material (the spinel phase is the crystal structure of the ferrite) through high-temperature pre-sintering (1100 - 1300 °C), avoiding the existence of other impurity oxides. After the sieved mixed powder is surface-activated by an acidic activator, even if the specific surface area of the mixed powder is small, it has sufficient sintering activity and can be sintered and densified below 1000 °C; at the same time, the grain size of the obtained manganese-zinc ferrite material still remains at 2 - 5 μm, avoiding abnormal grain growth and effectively maintaining the single-domain structure, thereby ensuring the acquisition of a high cut-off frequency of the manganese-zinc ferrite material.

[0071] The present invention adopts the method of high-temperature pre-sintering + low-temperature secondary sintering. The powder obtained by high-temperature pre-sintering has good crystallinity and high purity, but poor sintering activity; by improving the sintering activity after surface-activating the pre-sintered powder, it can be sintered and densified at low temperature, and the grain size will not grow abnormally, which is beneficial to obtaining a manganese-zinc ferrite material with high-frequency magnetic properties.

[0072] To further illustrate the present invention, a manganese-zinc ferrite material and its preparation method provided by the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0073] Example 1

[0074] Taking the total mass of the main components as 100%, the main components are: Fe 2 O 3 70 wt%, ZnO 5.5 wt%, MnO 2 the balance;

[0075] Taking the percentage of the total mass of the main components, the secondary components are: SnO 2 500 ppm, Co 3 O 4 400 ppm, In 2 O 3 500 ppm, TiO 2 500 ppm;

[0076] Weigh the main components and secondary components according to the above ratios, put them into a ball mill, with a ball milling speed of 250 r / min, ball mill for 5 h, and mix evenly to obtain ball milled material;

[0077] Pre-burn the ball milled material under a nitrogen atmosphere, heat it from room temperature to 1100 °C at a rate of 200 °C / h, hold for 3 h, and cool it to room temperature with the furnace to obtain pre-burned material;

[0078] Mechanically crush and then air mill crush the pre-burned material, and then use an air classifier to screen out powders with a particle size of 2 - 5 μm to obtain mixed powders;

[0079] Mix the mixed powders with an activation solvent, stir well, carry out activation, knead and granulate. According to the mass of the mixed powders being 100%, add 8 wt% of the activation solvent. The activation solvent is water, polyvinyl alcohol and the acidic activator ammonium nitrate, where the concentration of polyvinyl alcohol is 5 wt% and the concentration of the acidic activator is 1 wt% to obtain granular material;

[0080] Press the granular material into a blank. The pressure for pressing is 400 MPa, the pressure holding time is 30 s, and the density of the blank is 3.0 g / cm 3 ;

[0081] Place the blank in an atmosphere sintering furnace for sintering. The sintering temperature is 850 °C, the holding time is 10 h, nitrogen is introduced during the sintering process to make the oxygen partial pressure less than 2%, and it is cooled to room temperature and taken out of the furnace to obtain a manganese-zinc ferrite material. The specific test results are summarized in Table 1.

[0082] Example 2

[0083] Based on the total mass of the main components being 100%, the main components are: Fe 2 O 3 68 wt%, ZnO 7 wt%, MnO 2 the balance;

[0084] Based on the percentage of the total mass of the main components, the minor components are: SnO 2 1000 ppm, Co 3 O 4 800 ppm, In 2 O 3 1000 ppm, TiO 2 1000 ppm;

[0085] Weigh the main components and minor components according to the above ratios, put them into a ball mill, and ball mill for 10 h at a ball mill rotation speed of 300 r / min to mix evenly, obtaining ball-milled material;

[0086] Pre-calcine the ball-milled material in a nitrogen atmosphere, heat from room temperature to 1200 °C at a rate of 250 °C / h, hold for 3 h, and cool to room temperature with the furnace, obtaining pre-calcined material;

[0087] Mechanically crush and then air-mill crush the pre-calcined material, and then use an air classifier to screen out powders with a particle size of 2 - 5 μm to obtain mixed powders;

[0088] Mix the mixed powders and an activation solvent, stir well, perform activation, knead and granulate. Based on the mass of the mixed powders being 100%, add 10 wt% of the activation solvent. The activation solvent is water, polyvinyl alcohol, and the acidic activator ammonium carbonate, where the concentration of polyvinyl alcohol is 6 wt% and the concentration of the acidic activator is 2 wt%, obtaining granular material;

[0089] Press the granular material into shape to obtain a green product. The pressure for pressing into shape is 450 MPa, the pressure holding time is 30 s, and the green density is 3.5 g / cm 3 ;

[0090] Place the green product in an atmosphere sintering furnace for sintering. The sintering temperature is 900 °C, the holding time is 8 h, nitrogen is introduced during the sintering process to make the oxygen partial pressure less than 2%, and it is cooled to room temperature and taken out of the furnace to obtain a manganese-zinc ferrite material. The specific test results are summarized in Table 1.

[0091] Example 3

[0092] Based on the total mass of the main components being 100%, the main components are: Fe 2 O 3 71 wt%, ZnO 8 wt%, MnO 2Margin;

[0093] Taking the percentage of the total mass of the main components, the secondary components are: SnO 2 1500 ppm, Co 3 O 4 1200 ppm, In 2 O 3 1500 ppm, TiO 2 1500 ppm;

[0094] Weigh the main components and secondary components according to the above ratios, put them into a ball mill, and ball mill at a speed of 350 r / min for 8 h to mix evenly and obtain ball-milled material;

[0095] Pre-burn the ball-milled material in a nitrogen atmosphere, heat it from room temperature to 1300 °C at a rate of 250 °C / h, hold for 2 h, and cool it to room temperature with the furnace to obtain pre-burned material;

[0096] Mechanically crush and air-mill crush the pre-burned material in sequence, and then use an air classifier to screen out powders with a particle size of 2 - 5 μm to obtain mixed powders;

[0097] Mix the mixed powders and an activation solvent, stir well, activate, knead and granulate. According to the mass of the mixed powders being 100%, add 12 wt% of the activation solvent. The activation solvent is water, polyvinyl alcohol, and the acidic activator ammonium bicarbonate, where the concentration of polyvinyl alcohol is 8 wt% and the concentration of the acidic activator is 3 wt% to obtain granular material;

[0098] Press the granular material into a blank. The pressure for pressing is 500 MPa, the pressure holding time is 30 s, and the density of the blank is 3.8 g / cm 3 ;

[0099] Place the blank in an atmosphere sintering furnace for sintering. The sintering temperature is 950 °C, the holding time is 6 h. Nitrogen is introduced during the sintering process to make the oxygen partial pressure less than 2%. Cool it to room temperature and take it out of the furnace to obtain a manganese-zinc ferrite material. The specific test results are summarized in Table 1.

[0100] Example 4

[0101] Taking the total mass of the main components as 100%, the main components are: Fe 2 O 3 72 wt%, ZnO 9 wt%, MnO 2 Margin;

[0102] Taking the percentage of the total mass of the main components, the secondary components are: SnO 2 2500 ppm, Co 3 O 41500 ppm, In 2 O 3 2000 ppm, TiO 2 1000 ppm;

[0103] Weigh the main components and auxiliary components according to the above ratios, put them into a ball mill, and ball mill at a speed of 400 r / min for 10 h to mix evenly, obtaining ball-milled material;

[0104] Pre-calcine the ball-milled material in a nitrogen atmosphere, heat it from room temperature to 1250 °C at a rate of 250 °C / h, hold for 3 h, and cool it to room temperature in the furnace to obtain pre-calcined material;

[0105] Mechanically crush and then air-mill crush the pre-calcined material, and then use an air classifier to screen out powders with a particle size of 2 - 5 μm to obtain mixed powders;

[0106] Mix the mixed powders and an activation solvent, stir well, activate, knead and granulate. Based on the mass of the mixed powders being 100%, add 15 wt% of the activation solvent. The activation solvent is water, polyvinyl alcohol and the acidic activator ammonium bicarbonate, where the concentration of polyvinyl alcohol is 10 wt% and the concentration of the acidic activator is 5 wt% to obtain granular material;

[0107] Press the granular material into a blank. The pressure for pressing is 600 MPa, the pressure holding time is 30 s, and the density of the blank is 3.5 g / cm 3 ;

[0108] Place the blank in an atmosphere sintering furnace for sintering. The sintering temperature is 980 °C, the holding time is 8 h, nitrogen is introduced during the sintering process to make the oxygen partial pressure less than 2%, and it is cooled to room temperature and taken out of the furnace to obtain a manganese-zinc ferrite material. The specific test results are summarized in Table 1.

[0109] Comparative Example 1

[0110] The preparation steps are the same as those in Example 1, except that the acidic activator ammonium nitrate is not added. The specific test results are summarized in Table 1.

[0111] Comparative Example 2

[0112] The preparation steps are the same as those in Example 2, except that the acidic activator ammonium carbonate is not added. The specific test results are summarized in Table 1.

[0113] Table 1 Performance test results of the manganese-zinc ferrite materials in Examples 1 - 4 and Comparative Examples 1 - 2

[0114]

[0115] As can be seen from Example 1 and Comparative Example 1 in Table 1, when the main components, secondary components, sintering and other processes are the same, in Example 1, due to the introduction of ammonium nitrate for solvent surface activation, with the grain size remaining unchanged, the relative density has been significantly improved compared to Comparative Example 1 (68% → 96%), resulting in a significant improvement in magnetic permeability (143 → 620), and the loss has also been significantly reduced (6550 kW / m 3 → 1950 kW / m 3 ).

[0116] As can be seen from Example 2 and Comparative Example 2 in Table 1, when the main components, secondary components, sintering and other processes are the same, in Comparative Example 2, due to the introduction of ammonium carbonate for solvent surface activation, with the grain size remaining unchanged, the relative density has been significantly improved compared to Comparative Example 2 (76% → 96%), resulting in a significant improvement in magnetic permeability (180 → 680), and the loss has also been significantly reduced (5920 kW / m 3 → 1800 kW / m 3 ).

[0117] Figure 1 This is the scanning electron microscope image of the manganese-zinc ferrite material obtained in Example 1 of the present invention. It shows that solvent surface activation can effectively increase the sintering activity and improve the relative density.

[0118] Figure 2 This is the scanning electron microscope image of the ferrite material prepared by Comparative Example 1 (traditional solid-phase sintering method). It shows that the grains of the ferrite prepared by the traditional method grow abnormally and the relative density is poor.

[0119] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all of them. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A manganese-zinc ferrite material, characterized in that: The raw materials include a main component and a secondary component; based on the total mass of the main component being 100%, the main component includes: 68-72wt% of Fe2O3, 5-9wt% of ZnO, and the balance of MnO2; In terms of percentage of the total mass of the main component, the auxiliary components include: SnO2500-2500ppm, Co3O4400-2500ppm, In2O3500-2500ppm, TiO2500-2500ppm; The grain size of the manganese-zinc ferrite material is distributed in the range of 2 to 5 μm, and the density is ≥95%.

2. The manganese-zinc ferrite material according to claim 1, characterized in that: The total mass of the auxiliary components is ≤1 wt % of the total mass of the main components.

3. The manganese-zinc ferrite material according to claim 1 or 2, characterized in that: The cut-off frequency of the manganese-zinc ferrite material is ≥5MHz, the initial magnetic permeability is >600, and the loss at 5MHz and 30mT is ≤2000kW / m 3 .

4. The method for preparing the manganese-zinc ferrite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: The main component and the auxiliary component are mixed and ball-milled to obtain a ball-milled material; Pre-sintering the ball mill material to obtain a pre-sintered material; the pre-sintering temperature is 1100-1300° C.; The pre-sintered material is crushed and sieved in sequence to obtain a mixed powder; The mixed powder and an activation solvent are mixed, activated and granulated to obtain a granular material; the activation solvent comprises water, a binder and an acidic activator; forming the granular material to obtain a blank; The blank is sintered to obtain a manganese-zinc ferrite material; the sintering temperature is 850-1000°C.

5. The preparation method according to claim 4, characterized in that: The particle size of the mixed powder is 2 to 5 μm.

6. The preparation method according to claim 4 or 5, characterized in that: The pre-firing heat preservation time is 1 to 3 hours; the sintering heat preservation time is 4 to 10 hours.

7. The preparation method according to claim 4, characterized in that: The total mass of the activation solvent is 5-15% of the mass of the mixed powder.

8. The preparation method according to claim 4 or 7, characterized in that: The acidic activator includes acidic ammonium salt; the binder includes polyvinyl alcohol; in the activation solvent, the concentration of the binder is 3-10wt%, and the concentration of the acidic activator is 1-5wt%.

9. The preparation method according to claim 4, characterized in that: The density of the blank is 3.0-3.8 g / cm 3 .

10. The preparation method according to claim 4 or 9, characterized in that: The oxygen partial pressure of the sintering is less than 2%.

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