Preparation method of Z-type ferrite ceramic

Abstract

The invention discloses a Z-type ferrite ceramic preparation method, and belongs to the technical field of ferrite ceramic preparation. The method comprises the following steps: firstly, synthesizing Co2Z ferrite powder through a pre-sintering process, and then carrying out particle size screening on the powder to obtain particles with different particle size ranges; and putting the screened powder into a mold, directionally arranging under the action of a rotating magnetic field provided by a neodymium iron boron permanent magnet, and sintering at high temperature to obtain the textured Co2Z ferrite ceramic. On the basis of a traditional solid-phase reaction sintering process, a particle directional arrangement strategy driven by a low-intensity magnetic field is introduced, the magnetic directional response capability is improved by regulating and controlling the particle size, and a texture orientation structure is constructed. According to the technological process, intervention of a high-intensity magnetic field is not needed, slurrying treatment on the particles is not needed either, a magnetic field generation device is remarkably simplified, and the overall preparation cost is reduced. The prepared textured Z-type ferrite ceramic shows excellent magnetic anisotropy, high magnetic conductivity and low magnetic loss performance, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ferrite ceramic preparation, and particularly relates to a Z-type ferrite ceramic preparation method. BACKGROUND

[0002] With the rapid development of electronic communication technology, the performance of radio frequency communication devices has higher requirements. Magnetoplumbite-type ferrite is considered as an ideal radio frequency communication device material because it has good dielectric and magnetic properties at high frequencies and is not limited by the Snoek limit. According to the stacking mode of R block, S block and T block in the crystal structure, the magnetoplumbite-type ferrite can be divided into M-type, Y-type, Z-type, W-type, U-type and X-type and other types. Among them, Z-type ferrite (Ba3Co2Fe 24 O 41 ) is considered as a key material to meet the technical requirements of future wireless communication systems because of its high permeability and high natural resonance frequency. The easy magnetization axis of Z-type ferrite is perpendicular to the c-axis direction, and if the grain can be driven to arrange in this direction, the magnetic crystal anisotropy energy that needs to be overcome in the magnetization process can be effectively reduced, thereby improving the high-frequency magnetic properties of the material. In recent years, methods for realizing the directional arrangement of Z-type ferrite particles have been reported. For example, Hitachi Metals, Inc. (Journal of Applied Physics 108 (2010) 3.) successfully prepared a textured Z-type ferrite ceramic by applying a rotating strong magnetic field of 6000 Oe and a uniaxial pressure of 14 MPa in the slurry (a mixture of Z-type ferrite and water) and sintering in an oxygen atmosphere. However, this method is complex to operate, the device structure is complex, the cost of the strong magnetic field generating device is extremely high, and it is difficult to realize large-scale industrial production. In addition, textured Z-type ferrite ceramics can be prepared by self-orientation process. For example, the patent with the patent number 201810256240.6 and the patent name "Preparation method of self-oriented Z-type hexagonal ferrite substrate" proposes to first prepare an M-phase precursor textured growth template by hydrothermal method, and then prepare a textured Z-type ferrite by sintering reaction. However, this process has a long preparation period and complex production steps. Therefore, on the basis of the traditional solid-phase reaction sintering process, if the means for directional arrangement of particles can be simplified and the Z-type ferrite particles can be driven to arrange in the easy magnetization direction under the condition of weak magnetic field, it will provide important support for the development of radio frequency communication devices. It is worth noting that the particle size plays a key role in the process of magnetic field-induced orientation. Particles with appropriate particle size range can effectively flip under the driving of magnetic moment, thereby significantly enhancing the degree of ceramic texturing. Therefore, it is of important practical value to develop a low-cost textured ceramic preparation process combining weak magnetic field driving and particle size control. SUMMARY

[0003] The application aims to provide a Z-type ferrite ceramic preparation method, and solve the problems of complex process and high cost in the existing Z-type ferrite ceramic orientation technology.

[0004] The technical scheme adopted by the application is as follows:

[0005] A Z-type ferrite ceramic preparation method is specifically implemented according to the following steps:

[0006] Step 1, batching:

[0007] BaCO3, Co2O3 and Fe2O3 are used as raw materials, the formula is calculated according to the stoichiometric ratio of Co2Z ferrite (Ba3Co2Fe 24 O 41 ) and the raw materials are weighed to obtain mixed raw material powder;

[0008] Step 2, primary ball milling:

[0009] The mixed raw material powder obtained in step 1, deionized water and zirconium dioxide grinding medium are mixed in a mass ratio of 1:(1-1.5):(3-6), and then placed in a ball mill at 300r / min-500r / min for 10-14 hours to uniformly mix, to obtain the primary ball-milled slurry;

[0010] Step 3, pre-sintering:

[0011] The primary ball-milled slurry obtained in step 2 is placed in an oven at 50-80℃ for drying, and then placed in a muffle furnace at 1150℃-1250℃ for sintering for 2-5 hours to obtain Co2Z ferrite pre-sintered powder;

[0012] Step 4, particle size screening:

[0013] The pre-sintered Co2Z ferrite powder in step 3 is ground, and then screened by particle size to obtain Co2Z ferrite particles with different particle size ranges;

[0014] Step 5, secondary ball milling:

[0015] The uniform Co2Z ferrite particles obtained in step 4, deionized water and zirconium dioxide grinding medium are mixed in a mass ratio of 1:(1-1.5):(3-6), and then placed in a ball mill at 300r / min-500r / min for 10-14 hours to obtain the secondary ball-milled slurry;

[0016] Step 6, weak magnetic field driven directional arrangement:

[0017] The secondary ball-milled slurry obtained in step 5 is placed in an oven at 50-80 DEG C for drying treatment to obtain a dry powder; then the dry powder is equally divided, and 6.67-36.7 wt% of the single divided powder is added to a mold placed above a neodymium-iron-boron permanent magnet, and the mold is rotated at a speed of 40-70 r / min for 3-7 min, so that the Co2Z ferrite particles are oriented and arranged in a specific direction under the action of the magnetic induction lines to form a powder arranged in a specific direction and laid flat; the operation is repeated until the single divided powder is all added to the mold and oriented and arranged.

[0018] Step 7, molding:

[0019] The oriented and arranged powder obtained in step 6 is pressed and molded under a uniaxial pressure of 4-10 MPa to obtain a green body.

[0020] Step 8, sintering:

[0021] The green body prepared in step 7 is placed in a muffle furnace at 1100 DEG C-1300 DEG C for sintering for 2-5 hours to obtain a Co2Z ferrite ceramic.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The present application provides a preparation method of Z-type ferrite ceramic, which introduces a weak magnetic field driven particle directional arrangement process based on the traditional solid phase reaction sintering process. The particles are induced to flip under the action of centrifugal force and magnetic force, and are arranged in an order along the direction of the lowest magnetization energy. At the same time, the particle size control strategy is combined to effectively enhance the particle flipping and directional arrangement order under the driving of the magnetic moment. The present application does not need to apply a strong magnetic field and perform slurry treatment on the particles, and the process is simple and mature, which significantly reduces the complexity of the equipment and the production cost. Under the action of a weak magnetic field (100-800 Oe), the Co2Z ferrite particles with a particle size of 38-50 mu m can be effectively flipped, and the orientation factor of the Z-type ferrite ceramic prepared by sintering can be increased to 0.548 at most, which shows a significant magnetic anisotropy. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Schematic diagram of the magnetic field driven process used for the examples;

[0025] Figure 2 XRD pattern of the Co2Z ferrite ceramic obtained in examples 1, 2, 3, 4 and comparative examples;

[0026] Figure 3 Surface SEM image of the Co2Z ferrite ceramic obtained in example 3;

[0027] Figure 4The hysteresis loops of the Co2Z ferrite ceramic obtained in Example 3 in the directions perpendicular to and parallel to the c-axis;

[0028] Figure 5 The hysteresis loops of the Co2Z ferrite ceramic obtained in the comparative example in the directions perpendicular to and parallel to the c-axis. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be described in detail below in combination with the drawings and examples.

[0030] Example 1

[0031] Step 1, batching:

[0032] BaCO3, Co2O3 and Fe2O3 as raw materials, and the batching calculation is performed according to the stoichiometric ratio of 0.0042 mol of Co2Z ferrite (Ba3Co2Fe 24 O 41 ), 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 are respectively taken to obtain the mixed raw material powder;

[0033] Step 2, primary ball milling:

[0034] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400r / min for 12h to uniformly mix, to obtain the primary ball-milled slurry;

[0035] Step 3, pre-sintering:

[0036] The primary ball-milled slurry obtained in step 2 is placed in a 60℃ oven for drying, and then placed in a 1225℃ muffle furnace for sintering for 3 hours to obtain the Co2Z ferrite pre-sintered powder;

[0037] Step 4, particle size screening:

[0038] The pre-sintered Co2Z ferrite powder in step 3 is ground, and then the Co2Z ferrite particles with a particle size range of less than 200 mesh (corresponding to <75μm) are selected through particle size screening;

[0039] Step 5, secondary ball milling:

[0040] The uniform Co2Z ferrite particles obtained in step 4 are mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400r / min for 12h to obtain the secondary ball-milled slurry;

[0041] Step 6, weak magnetic field driven directional arrangement:

[0042] The secondary ball-milling slurry obtained in step 5 was placed in a 60℃ oven for drying treatment to obtain a dry powder. Then the dry powder was equally divided by 0.3g per portion, and 6.67wt% of the 0.3g powder was added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet was about 400Oe detected by a gauss meter, which formed a horizontal magnetic field line distribution above it pointing from the N pole to the S pole. Thereafter, the mold with the powder was rotated at a speed of 40r / min, and the rotation time was 5min, so that the powder was driven by the magnetic moment under the action of the horizontal magnetic field to realize the preferred orientation arrangement of the particles along the magnetic field lines; the operation was repeated until all the 0.3g powder was added to the mold and completed the directional arrangement.

[0043] Step 7, molding:

[0044] The directional arrangement powder obtained in step 6 was pressed and molded under a uniaxial pressure of 5MPa to obtain a green body.

[0045] Step 8, sintering:

[0046] The green body prepared in step 7 was placed in a muffle furnace at 1170℃ for sintering for 3h to obtain a Co2Z ferrite ceramic.

[0047] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 were characterized.

[0048] Example 2

[0049] Step 1, batching:

[0050] BaCO3, Co2O3 and Fe2O3 were used as raw materials, and the batching calculation was performed according to the stoichiometric ratio of 0.0042mol Co2Z ferrite (Ba3Co2Fe 24 O 41 ) to obtain 2.537g BaCO3, 0.711g Co2O3 and 8.213g Fe2O3, respectively, to obtain a mixed raw material powder;

[0051] Step 2, primary ball-milling:

[0052] The mixed raw material powder obtained in step 1 was mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400r / min for 12h to obtain a primary ball-milling slurry;

[0053] Step 3, pre-sintering:

[0054] The slurry after the first ball milling in step 2 is dried in an oven at 60℃, and then sintered in a muffle furnace at 1225℃ for 3 hours to obtain the pre-sintered Co2Z ferrite powder;

[0055] Step 4, screening particle size:

[0056] The pre-sintered Co2Z ferrite powder in step 3 is ground, and then the Co2Z ferrite particles with a particle size range of 200-300 mesh (corresponding to 50-75 μm) are selected by particle size screening;

[0057] Step 5, second ball milling:

[0058] The uniform Co2Z ferrite particles obtained in step 4 are mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain the slurry after the second ball milling;

[0059] Step 6, weak magnetic field driven directional arrangement:

[0060] The slurry after the second ball milling in step 5 is dried in an oven at 60℃ to obtain the dry powder. Then, the dry powder is equally divided by 0.3 g per portion, and 16.67 wt% of the powder in 0.3 g is added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet is about 400 Oe detected by a gauss meter, which forms a horizontal magnetic field line distribution above the magnet pointing from the N pole to the S pole. Then, the mold with the powder is rotated at a speed of 50 r / min, and the rotation time is 5 min, so that the powder is driven by the magnetic torque under the action of the horizontal magnetic field, and the particles are preferentially oriented and arranged along the magnetic field line direction; the operation is repeated until all the 0.3 g powder is added to the mold and the directional arrangement is completed.

[0061] Step 7, molding:

[0062] The directional arrangement powder in step 6 is pressed and molded under a uniaxial pressure of 5 MPa to obtain a green body.

[0063] Step 8, sintering:

[0064] The green body prepared in step 7 is sintered in a muffle furnace at 1170℃ for 3 h to obtain a Co2Z ferrite ceramic.

[0065] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8 are characterized.

[0066] Example 3

[0067] Step 1, batching:

[0068] BaCO3, Co2O3 and Fe2O3 as raw materials, and according to the stoichiometric ratio of 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 ) to calculate the batching, 2.537 g of BaCO3, 0.711 g of Co2O3 and 8.213 g of Fe2O3 were weighed respectively to obtain a mixed raw material powder;

[0069] Step 2, primary ball milling:

[0070] The mixed raw material powder obtained in step 1 was mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to make it uniformly mixed, obtaining a slurry after primary ball milling;

[0071] Step 3, pre-sintering:

[0072] The slurry after primary ball milling obtained in step 2 was placed in an oven at 60°C for drying, and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-sintered powder;

[0073] Step 4, particle size screening:

[0074] The Co2Z ferrite powder after pre-sintering in step 3 was ground, and then the Co2Z ferrite particles with a particle size range of 300-400 mesh (corresponding to 38-50 μm) were selected by particle size screening;

[0075] Step 5, secondary ball milling:

[0076] The uniformly mixed Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain a slurry after secondary ball milling;

[0077] Step 6, weak magnetic field driven directional arrangement:

[0078] The secondary ball milling slurry obtained in step 5 was placed in an oven at 60°C for drying treatment to obtain dry powder. Then the dry powder was evenly divided by 0.3 g per portion, and 26.67 wt% of the powder in 0.3 g was added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet was about 400 Oe detected by a gauss meter, which formed a horizontal magnetic field line distribution above the magnet pointing from the N pole to the S pole. Then, the mold with the powder was rotated at a speed of 60 r / min, and the rotation time was 5 min, so that the powder was driven by the magnetic torque under the action of the horizontal magnetic field, and the particles were preferentially oriented and arranged along the magnetic field line direction; the operation was repeated until 0.3 g of powder was added to the mold and the directional arrangement was completed;

[0079] Step 7, molding:

[0080] The oriented arrangement powder obtained in step 6 is molded by pressing under a uniaxial pressure of 5 MPa to obtain a green body;

[0081] Step 8, sintering:

[0082] The green body prepared in step 7 is sintered in a muffle furnace at 1170℃ for 3h to obtain a Co2Z ferrite ceramic.

[0083] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8 are characterized.

[0084] Example 4

[0085] Step 1, batching:

[0086] BaCO3, Co2O3 and Fe2O3 are used as raw materials, and the batching calculation is performed according to the stoichiometric ratio of 0.0042 mol of Co2Z ferrite (Ba3Co2Fe 24 O 41 ) to obtain 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3, respectively, and obtain a mixed raw material powder;

[0087] Step 2, primary ball milling:

[0088] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400r / min for 12h to uniformly mix to obtain a primary ball-milled slurry;

[0089] Step 3, pre-sintering:

[0090] The primary ball-milled slurry obtained in step 2 is dried in an oven at 60℃, and then sintered in a muffle furnace at 1225℃ for 3h to obtain a Co2Z ferrite pre-sintered powder;

[0091] Step 4, particle size screening:

[0092] The pre-sintered Co2Z ferrite powder in step 3 is ground, and then the Co2Z ferrite particles with a particle size range of less than 400 mesh (corresponding to <38μm) are selected by particle size screening;

[0093] Step 5, secondary ball milling:

[0094] The uniform Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain a secondary ball-milled slurry;

[0095] Step 6, weak magnetic field driving directional arrangement:

[0096] The secondary ball-milled slurry obtained in step 5 was placed in an oven at 60°C for drying treatment to obtain a dry powder. Then, the dry powder was equally divided by 0.3 g per portion, and 36.67 wt% of the 0.3 g powder was added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet was about 400 Oe detected by a gauss meter, which formed a horizontal magnetic field line distribution above the neodymium-iron-boron permanent magnet pointing from the N pole to the S pole. Subsequently, the mold with the powder was rotated at a speed of 70 r / min, and the rotation time was 5 min, so that the powder was driven by the magnetic torque under the action of the horizontal magnetic field to realize the preferred orientation arrangement of the particles along the direction of the magnetic field lines; the operation was repeated until all the 0.3 g powder was added to the mold and the directional arrangement was completed.

[0097] Step 7, molding:

[0098] The directional arrangement powder obtained in step 6 was molded under a uniaxial pressure of 5 MPa to obtain a green body.

[0099] Step 8, sintering:

[0100] The green body prepared in step 7 was placed in a muffle furnace at 1170°C for sintering for 3 h to obtain a Co2Z ferrite ceramic.

[0101] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8 were characterized.

[0102] Figure 2 The XRD patterns of the Co2Z ferrite ceramics obtained in Examples 1, 2, 3, 4 and Comparative Examples are shown in the figure. As can be seen from the figure, the preferred orientation of the Co2Z ferrite ceramics obtained in all examples is (00l) direction, indicating that the grains are directionally arranged along the easy magnetization direction. The Lotgering orientation factor method was used to calculate Figure 2 The (00l) orientation factor of the Co2Z ferrite ceramics prepared in each example and comparative example in the table was used to characterize the texture degree of the ceramic. The Lotgering orientation factor calculation method is defined as:

[0103]

[0104] wherein, ∑I 00l is the sum of the (00l) peak intensities of the ceramic sample, and ∑I hklThe sum of the (hkl) peak intensities of the sample, The sum of the (00l) peak intensities of the standard sample. By calculation, the orientation factor of Example 1 is 0.364, the orientation factor of Example 2 is 0.471, the orientation factor of Example 3 is 0.548, the orientation factor of Example 4 is 0.464, and the orientation factor of the comparative example is 0.101.

[0105] Figure 3 The surface SEM image of the Co2Z ferrite ceramic obtained in Example 3. As can be seen from the figure, the particles on the surface of the Co2Z ferrite ceramic are mainly in the form of platelets.

[0106] Figure 4 The magnetic hysteresis loop of the Co2Z ferrite ceramic obtained in Example 3 in the direction perpendicular to and parallel to the c-axis direction. The Co2Z ferrite ceramic obtained in Example 3 exhibits obvious magnetic anisotropy when magnetized in different directions. When the direction of the applied magnetic field is along the surface of the ceramic, the material is more easily magnetized, and the saturation magnetization reaches 51.8 Oe / g.

[0107] Example 5

[0108] Step 1, batching:

[0109] BaCO3, Co2O3 and Fe2O3 as raw materials, according to the stoichiometric ratio of 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 ) is calculated, 2.537 g of BaCO3, 0.711 g of Co2O3 and 8.213 g of Fe2O3 are respectively weighed, and the mixed raw material powder is obtained;

[0110] Step 2, primary ball milling:

[0111] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a 400 r / min ball mill for 12 h to make it uniformly mixed, and the primary ball-milled slurry is obtained;

[0112] Step 3, pre-sintering:

[0113] The primary ball-milled slurry obtained in step 2 is placed in a 60°C oven for drying, and then placed in a 1225°C muffle furnace for sintering for 3 hours to obtain Co2Z ferrite pre-sintered powder;

[0114] Step 4, particle size screening:

[0115] The Co2Z ferrite powder pre-fired in step 3 is ground, and Co2Z ferrite particles with a particle size range of 200-300 mesh (corresponding to 50-75 μm) are selected by particle size screening;

[0116] Step 5, secondary ball milling:

[0117] The uniform Co2Z ferrite particles obtained in step 4 are mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain a secondary ball-milled slurry;

[0118] Step 6, weak magnetic field driven directional arrangement:

[0119] The secondary ball-milled slurry obtained in step 5 is placed in an oven at 60°C for drying treatment to obtain a dry powder. Then, the dry powder is equally divided at 0.3 g per portion, and 36.67 wt% of the powder in 0.3 g is added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet is about 100 Oe detected by a gauss meter, which forms a horizontal magnetic field line distribution above the magnet pointing from the N pole to the S pole. Subsequently, the mold with the powder is rotated at a speed of 60 r / min, and the rotation time is 3 min, so that the powder is driven by the magnetic torque under the action of the horizontal magnetic field to realize the preferred orientation arrangement of the particles along the magnetic field line direction; the operation is repeated until all the 0.3 g powder is added to the mold and the directional arrangement is completed.

[0120] Step 7, molding:

[0121] The directional arrangement powder obtained in step 6 is pressed and molded under a uniaxial pressure of 5 MPa to obtain a green body.

[0122] Step 8, sintering:

[0123] The green body prepared in step 7 is placed in a muffle furnace at 1170°C and sintered for 3 h to obtain a Co2Z ferrite ceramic.

[0124] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 are characterized.

[0125] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 are characterized. Through testing, the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example is 0.418, and the magnetic hysteresis loop along the surface and cross section of the ceramic shows obvious anisotropy.

[0126] Example 6

[0127] Step 1, batching:

[0128] BaCO3, Co2O3 and Fe2O3 as raw materials, and according to the stoichiometric ratio of 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 ) to calculate the batching, 2.537 g of BaCO3, 0.711 g of Co2O3 and 8.213 g of Fe2O3 were weighed respectively to obtain a mixed raw material powder;

[0129] Step 2, primary ball milling:

[0130] The mixed raw material powder obtained in step 1 was mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to make it uniformly mixed, obtaining a slurry after primary ball milling;

[0131] Step 3, pre-sintering:

[0132] The slurry after primary ball milling obtained in step 2 was placed in an oven at 60°C for drying, and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-sintered powder;

[0133] Step 4, particle size screening:

[0134] The Co2Z ferrite powder after pre-sintering in step 3 was ground, and then the Co2Z ferrite particles with a particle size range of 200-300 mesh (corresponding to 50-75 μm) were selected by particle size screening;

[0135] Step 5, secondary ball milling:

[0136] The uniformly mixed Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding medium in a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain a slurry after secondary ball milling;

[0137] Step 6, weak magnetic field driven directional arrangement:

[0138] The secondary ball milling slurry obtained in step 5 was placed in an oven at 60°C for drying treatment to obtain dry powder. Then the dry powder was evenly divided by 0.3 g per portion, and 36.67 wt% of the powder in 0.3 g was added to a mold placed above a neodymium-iron-boron permanent magnet. The magnetic field strength generated by the neodymium-iron-boron permanent magnet was about 800 Oe detected by a gauss meter, which formed a horizontal magnetic field line distribution above the magnet pointing from N pole to S pole. Then, the mold with the powder was rotated at a speed of 60 r / min, and the rotation time was 7 min, so that the powder was driven by the magnetic torque under the action of the horizontal magnetic field, and the particles were preferentially oriented and arranged along the direction of the magnetic field line; the operation was repeated until 0.3 g of powder was added to the mold and the directional arrangement was completed;

[0139] Step 7, forming:

[0140] The oriented arrangement powder obtained in step 6 is formed by pressing under a uniaxial pressure of 5 MPa to obtain a green body;

[0141] Step 8, sintering:

[0142] The green body prepared in step 7 is placed in a muffle furnace at 1170℃ for sintering for 3 hours to obtain Co2Z ferrite ceramic.

[0143] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 are characterized. It is tested that the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example is 0.536, and the magnetic hysteresis loops along the surface and cross section of the ceramic exhibit obvious anisotropy.

[0144] Comparative example

[0145] The comparative example is a polycrystalline Co2Z ferrite ceramic prepared by a traditional solid-phase sintering method, specifically comprising the following steps:

[0146] Step 1, batching:

[0147] BaCO3, Co2O3 and Fe2O3 are used as raw materials, and the stoichiometric ratio of 0.0042 mol of Co2Z ferrite (Ba3Co2Fe 24 O 41 ) is calculated for batching, and 2.537 g of BaCO3, 0.711 g of Co2O3 and 8.213 g of Fe2O3 are respectively weighed to obtain mixed raw material powder;

[0148] Step 2, primary ball milling:

[0149] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for ball milling for 12 hours to uniformly mix, to obtain a primary ball-milled slurry;

[0150] Step 3, pre-sintering:

[0151] The primary ball-milled slurry obtained in step 2 is placed in a 60℃ oven for drying, and then placed in a muffle furnace at 1225℃ for sintering for 3 hours to obtain Co2Z ferrite pre-sintered powder;

[0152] Step 4, secondary ball milling:

[0153] The Co2Z ferrite particles obtained in step 3 are mixed with deionized water and zirconium dioxide grinding medium at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 h to obtain a secondary ball-milled slurry;

[0154] Step 5, molding:

[0155] After the secondary ball-milled slurry obtained in step 4 is dried in an oven at 60℃, 0.3 g of the powder is weighed and molded under a uniaxial pressure of 5 MPa to obtain a green body.

[0156] Step 6, sintering:

[0157] The green body prepared in step 5 is sintered in a muffle furnace at 1170℃ for 3 hours to obtain a Co2Z ferrite ceramic.

[0158] The phase composition, orientation factor, micro-morphology and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 6 are characterized. It is tested that the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example is 0.101, and the cross-section particles do not realize directional arrangement along the easy magnetization direction. Figure 5 The magnetic hysteresis loops of the Co2Z ferrite ceramic obtained in the comparative example in the directions perpendicular to and parallel to the c-axis direction are shown in the figure. As can be seen from the figure, the Co2Z ferrite ceramic does not exhibit obvious magnetic anisotropy.

[0159] In summary, the present application introduces a preferred orientation process of weak magnetic field driving and particle size control on the basis of the traditional solid-phase reaction sintering process, and realizes the preparation of textured Co2Z ferrite ceramic. The process rotates the mold in the weak magnetic field provided by the neodymium-iron-boron permanent magnet, induces the particles to arrange directionally along the easy magnetization direction under the synergistic action of centrifugal force and magnetic force, optimizes the magnetic response and flipping ability of the particles by controlling the particle size, and prepares the (00l) preferred orientation Co2Z ferrite ceramic through sintering. The particles in the textured ceramic arrange directionally along the easy magnetization direction and exhibit obvious magnetic anisotropy. The above results fully prove that the weak magnetic field driving and particle size control process of the present application can effectively construct the textured Co2Z ferrite ceramic, and provides a new idea and key technical path for the low-energy-consumption and low-cost preparation of high-performance magnetic dielectric materials.

[0160] The above-described embodiments only express the specific implementation of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing Z-type ferrite ceramics, characterized in that: Please follow the steps below to implement: Step 1. Ingredients: BaCO3, Co2O3 and Fe2O3 are used as raw materials, according to Co2Z ferrite (Ba3Co2Fe 24 O 41 ) and weighing the raw materials to obtain a mixed raw material powder; Step 2: First ball milling: The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media in a mass ratio of 1: (1-1.5): (3-6), and then placed in a ball mill at 300 rpm to 500 rpm for 10-14 hours to uniformly mix the mixed raw material powder to obtain a primary milled slurry; Step 3: Pre-burning: The slurry after the primary ball milling obtained in step 2 is placed in an oven at 50-80°C for drying, and then placed in a muffle furnace at 1150°C-1250°C for 2-5 hours to obtain a pre-sintered Co2Z ferrite powder; Step 4: Screening particle size: The Co2Z ferrite powder pre-sintered in step 3 is ground and then sieved to obtain Co2Z ferrite particles of different particle size ranges; Step 5: Secondary ball milling: The uniform Co2Z ferrite particles obtained in step 4 are mixed with deionized water and zirconium dioxide grinding media in a mass ratio of 1: (1-1.5): (3-6), and then placed in a ball mill at 300 rpm to 500 rpm for 10-14 hours to obtain a secondary ball-milled slurry; Step 6: Weak magnetic field driven directional alignment: The secondary ball-milled slurry obtained in step 5 is placed in an oven at 50-80° C. for drying to obtain a dry powder; the dry powder is then divided equally in equal proportions, and 6.67-36.7 wt % of the powder in the single divided powder is added to a mold placed above a NdFeB permanent magnet, wherein the magnetic field strength generated by the NdFeB permanent magnet is approximately 100 Oe-800 Oe as measured by a Gauss meter, and the mold is rotated at a speed of 40-70 r / min for 3-7 minutes to orient the Co2Z ferrite particles in a specific direction under the action of magnetic flux lines to form an aligned powder; this operation is repeated until all the single divided powders are added to the mold and the alignment is completed; Step 6: Molding: The aligned powder obtained in step 6 is pressed under a uniaxial pressure of 4-10 MPa to obtain a green body; Step 7: Sintering: The green body prepared in step 7 is placed in a muffle furnace at 1100° C.-1300° C. and sintered for 2-5 hours to obtain Co2Z ferrite ceramics.

2. The method for preparing Z-type ferrite ceramics according to claim 1, characterized in that: The step 4 includes obtaining pre-sintered Co2Z ferrite particles of different particle size ranges by particle size screening. The specific operation method is: crushing and grinding the pre-sintered Co2Z ferrite powder with a mortar, and screening it through 200 mesh, 300 mesh and 400 mesh stainless steel sieves in turn to obtain Co2Z ferrite particles of different particle size ranges.

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