A method for preparing Z-type ferrite ceramics

Abstract

This invention discloses a method for preparing Z-type ferrite ceramics, belonging to the field of ferrite ceramic preparation technology. The method first synthesizes Co2Z ferrite powder through a pre-sintering process, then sieves the powder to obtain particles with different size ranges. The sieved powder is placed in a mold and oriented under the influence of a rotating magnetic field provided by a NdFeB permanent magnet, followed by high-temperature sintering to obtain textured Co2Z ferrite ceramics. Based on the traditional solid-state reaction sintering process, this invention introduces a weak magnetic field-driven particle orientation strategy and enhances the magnetic orientation response capability by controlling the particle size, thus constructing a textured orientation structure. This process does not require the intervention of a strong magnetic field or the slurry treatment of the particles, significantly simplifying the magnetic field generating device and reducing the overall preparation cost. The prepared textured Z-type ferrite ceramics exhibit excellent magnetic anisotropy, high permeability, and low magnetic loss performance, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of ferrite ceramic preparation technology, specifically relating to a method for preparing Z-type ferrite ceramics. Background Technology

[0002] With the rapid development of electronic communication technology, radio frequency (RF) communication devices place higher demands on material performance. Magnetolite ferrites, due to their excellent dielectric and magnetic properties at high frequencies and their lack of Snoek limit limitation, are considered ideal materials for RF communication devices. Based on the different stacking arrangements of the R, S, and T blocks in their crystal structure, magnetolite ferrites can be classified into various types, including M-type, Y-type, Z-type, W-type, U-type, and X-type. Among them, Z-type ferrite (Ba3Co2Fe)... 24 O 41 Due to its high permeability and high natural resonant frequency, Z-type ferrite is considered a key material to meet the technical requirements of future wireless communication systems. The easy magnetization axis of Z-type ferrite is perpendicular to the c-axis. If the grains can be driven to align in this direction, the magnetocrystalline anisotropy that needs to be overcome during magnetization can be effectively reduced, thereby improving the high-frequency magnetic properties of the material. In recent years, methods for achieving the directional alignment of Z-type ferrite particles have been reported. For example, Hitachi Metals Co., Ltd. (Journal of Applied Physics 108 (2010) 3.) successfully prepared Z-type ferrite ceramics with a textured structure by applying a rotating strong magnetic field of 6000 Oe and a uniaxial pressure of 14 MPa to a slurry (a mixture of Z-type ferrite and water) and sintering it in an oxygen atmosphere. However, this method is complex to operate, requires complex equipment structures, and the cost of the strong magnetic field generator is extremely high, making large-scale industrial production difficult. Furthermore, textured Z-type ferrite ceramics can be prepared using a self-orientation process. For example, patent number 201810256240.6, entitled "A Method for Preparing a Self-Oriented Z-Type Hexagonal Ferrite Substrate," proposes first preparing a textured growth template of an M-phase precursor using a hydrothermal method, and then preparing the textured Z-type ferrite through a sintering reaction. However, this process has a long preparation cycle and complex production steps. Therefore, based on the traditional solid-state reaction sintering process, simplifying the particle orientation arrangement method and achieving the orientation of Z-type ferrite particles along the easy magnetization direction under weak magnetic field conditions will provide important support for the development of radio frequency communication devices. It is worth noting that particle size plays a key role in the magnetic field-induced orientation process. Particles within an appropriate size range can achieve effective flipping under magnetic torque, thereby significantly enhancing the degree of ceramic texture. Therefore, developing a low-cost textured ceramic preparation process that combines weak magnetic field driving and particle size control has significant practical value. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing Z-type ferrite ceramics, which solves the problems of complex processes and high costs in existing Z-type ferrite ceramic orientation technologies.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for preparing Z-type ferrite ceramics is implemented according to the following steps:

[0006] Step 1, Ingredients:

[0007] Using BaCO3, Co2O3, and Fe2O3 as raw materials, based on Co2Z ferrite (Ba3Co2Fe 24 O 41 Calculate the formula based on the stoichiometric ratio of the raw materials and weigh them to obtain a mixed raw material powder;

[0008] Step 2, First ball milling:

[0009] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:(1-1.5):(3-6), and then ball-milled in a ball mill at 300r / min-500r / min for 10-14 hours to make it uniformly mixed, so as to obtain the slurry after one ball milling.

[0010] Step 3, Preheating:

[0011] After ball milling in step 2, the slurry is dried in an oven at 50-80℃ and then sintered in a muffle furnace at 1150℃-1250℃ for 2-5 hours to obtain Co2Z ferrite pre-calcined powder.

[0012] Step 4, sieve particle size:

[0013] The pre-calcined Co2Z ferrite powder in step 3 is ground and then sieved to obtain Co2Z ferrite particles with different particle sizes.

[0014] Step 5, Secondary ball milling:

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

[0016] Step 6: Weak magnetic field drives directional alignment:

[0017] The secondary ball milling slurry obtained in step 5 is dried in an oven at 50-80℃ to obtain dry powder. The dry powder is then divided into equal portions, and 6.67-36.7 wt% of the powder from each portion is added to a mold placed above a NdFeB permanent magnet. The mold is rotated at 40-70 r / min for 3-7 min to orient the Co2Z ferrite particles in a specific direction under the action of magnetic field lines, forming a directional and flat powder. This operation is repeated until all the powder from each portion is added to the mold and directionally aligned.

[0018] Step 7, Shaping:

[0019] The oriented powder obtained in step 6 is pressed into shape 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 was sintered in a muffle furnace at 1100℃-1300℃ for 2-5 hours to obtain Co2Z ferrite ceramic.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention provides a method for preparing Z-type ferrite ceramics. This method introduces a weak magnetic field-driven particle orientation process based on the traditional solid-state reaction sintering process. By inducing particles to flip under centrifugal force and magnetic force, they are ordered to align along the direction of lowest magnetization energy. Simultaneously, a particle size control strategy is combined to effectively enhance the particle flipping and ordered orientation under magnetic torque. This invention eliminates the need for a strong magnetic field and particle slurry treatment; the process is simple and mature, significantly reducing equipment complexity and production costs. Under a weak magnetic field (100-800 Oe), Co2Z ferrite particles with a diameter of 38-50 μm can achieve effective flipping. The orientation factor of the Z-type ferrite ceramics prepared by sintering can be increased to a maximum of 0.548, exhibiting significant magnetic anisotropy. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the magnetic field driving process used in the embodiment;

[0025] Figure 2 The XRD patterns of the Co2Z ferrite ceramics obtained in Examples 1, 2, 3, 4 and the comparative examples are shown.

[0026] Figure 3 Here is a 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 are in directions perpendicular to and parallel to the c-axis.

[0028] Figure 5 The hysteresis loops of the Co2Z ferrite ceramic obtained for comparison are shown in the directions perpendicular to and parallel to the c-axis. Detailed implementation method:

[0029] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0030] Example 1

[0031] Step 1, Ingredients:

[0032] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0033] Step 2, First ball milling:

[0034] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0035] Step 3, Preheating:

[0036] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0037] Step 4, sieve particle size:

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

[0039] Step 5, Secondary ball milling:

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

[0041] Step 6: Weak magnetic field drives directional alignment:

[0042] The secondary ball-milled slurry obtained in step 5 was dried in a 60°C oven to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 6.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 400 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 40 r / min for 5 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0043] Step 7, Shaping:

[0044] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0045] Step 8, Sintering:

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

[0047] Characterize the phase composition, orientation factor, microstructure and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8.

[0048] Example 2

[0049] Step 1, Ingredients:

[0050] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0051] Step 2, First ball milling:

[0052] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0053] Step 3, Preheating:

[0054] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0055] Step 4, sieve particle size:

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

[0057] Step 5, Secondary ball milling:

[0058] The uniform Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5 and then ball-milled in a ball mill at 400 r / min for 12 h to obtain a slurry after secondary ball milling.

[0059] Step 6: Weak magnetic field drives directional alignment:

[0060] The secondary ball-milled slurry obtained in step 5 was dried in an oven at 60°C to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 16.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 400 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 50 r / min for 5 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0061] Step 7, Shaping:

[0062] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0063] Step 8, Sintering:

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

[0065] Characterize the phase composition, orientation factor, microstructure and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8.

[0066] Example 3

[0067] Step 1, Ingredients:

[0068] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0069] Step 2, First ball milling:

[0070] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0071] Step 3, Preheating:

[0072] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0073] Step 4, sieve particle size:

[0074] The pre-calcined Co2Z ferrite powder in step 3 is ground, and then Co2Z ferrite particles with a particle size range of 300 mesh to 400 mesh (corresponding to 38-50μm) are selected by particle size sieving.

[0075] Step 5, Secondary ball milling:

[0076] The uniform Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5 and then ball-milled 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 drives directional alignment:

[0078] The secondary ball-milled slurry obtained in step 5 was dried in an oven at 60°C to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 26.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 400 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 60 r / min for 5 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0079] Step 7, Shaping:

[0080] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0081] Step 8, Sintering:

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

[0083] Characterize the phase composition, orientation factor, microstructure and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8.

[0084] Example 4

[0085] Step 1, Ingredients:

[0086] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0087] Step 2, First ball milling:

[0088] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0089] Step 3, Preheating:

[0090] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0091] Step 4, sieve particle size:

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

[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 media at a mass ratio of 1:1.2:3.5 and then ball-milled in a ball mill at 400 r / min for 12 h to obtain a slurry after secondary ball milling.

[0095] Step 6: Weak magnetic field drives directional alignment:

[0096] The secondary ball-milled slurry obtained in step 5 was dried in an oven at 60°C to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 36.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 400 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 70 r / min for 5 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0097] Step 7, Shaping:

[0098] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0099] Step 8, Sintering:

[0100] The green body prepared in step 7 was sintered in a muffle furnace at 1170℃ for 3 hours to obtain Co2Z ferrite ceramic.

[0101] Characterize the phase composition, orientation factor, microstructure and magnetic anisotropy of the Co2Z ferrite ceramic obtained in step 8.

[0102] Figure 2 The XRD patterns of the Co2Z ferrite ceramics obtained in Examples 1, 2, 3, 4, and the comparative example are shown in the figures. As can be seen from the figures, the preferred orientation of the Co2Z ferrite ceramics obtained in all examples is the (00l) direction, indicating that the grains are oriented 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 embodiment and comparative example is used to characterize the texture of the ceramics. The Lotgering orientation factor calculation method is defined as follows:

[0103]

[0104] Where, ∑I 00l The sum of the (00l) peak intensities of the ceramic sample, ∑I hklThis is the sum of the (hkl) peak intensities of the sample. The sum of the (00l) peak intensities of the standard samples. Calculations show that the orientation factor for Example 1 is 0.364, for Example 2 it is 0.471, for Example 3 it is 0.548, for Example 4 it is 0.464, and for the comparative example it is 0.101.

[0105] Figure 3 The image shows a surface SEM image of the Co2Z ferrite ceramic obtained in Example 3. As can be seen from the image, the particles on the surface of the Co2Z ferrite ceramic mainly exhibit a plate-like morphology.

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

[0107] Example 5

[0108] Step 1, Ingredients:

[0109] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0110] Step 2, First ball milling:

[0111] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0112] Step 3, Preheating:

[0113] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0114] Step 4, sieve particle size:

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

[0116] Step 5, Secondary ball milling:

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

[0118] Step 6: Weak magnetic field drives directional alignment:

[0119] The secondary ball-milled slurry obtained in step 5 was dried in an oven at 60°C to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 36.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 100 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 60 r / min for 3 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0120] Step 7, Shaping:

[0121] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0122] Step 8, Sintering:

[0123] The green body prepared in step 7 was sintered in a muffle furnace at 1170℃ for 3 hours to obtain Co2Z ferrite ceramic.

[0124] Characterize the phase composition, orientation factor, microstructure and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8.

[0125] The phase composition, orientation factor, microstructure, and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 were characterized. Tests showed that the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example was 0.418, and it exhibited significant anisotropy along the hysteresis loops of the ceramic surface and cross-section.

[0126] Example 6

[0127] Step 1, Ingredients:

[0128] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0129] Step 2, First ball milling:

[0130] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then ball-milled in a ball mill at 400 r / min for 12 h to make it uniformly mixed, thus obtaining a slurry after one ball milling.

[0131] Step 3, Preheating:

[0132] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0133] Step 4, sieve particle size:

[0134] The pre-calcined Co2Z ferrite powder in step 3 is ground, and then Co2Z ferrite particles with a particle size range of 200 mesh to 300 mesh (corresponding to 50-75μm) are selected by particle size sieving.

[0135] Step 5, Secondary ball milling:

[0136] The uniform Co2Z ferrite particles obtained in step 4 were mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5 and then ball-milled 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 drives directional alignment:

[0138] The secondary ball-milled slurry obtained in step 5 was dried in an oven at 60°C to obtain a dry powder. The dried powder was then evenly divided into 0.3g portions. 36.67wt% of this 0.3g powder was added to a mold placed above a neodymium iron boron (NdFeB) permanent magnet. The magnetic field strength generated by the NdFeB permanent magnet, measured by a gaussmeter, was approximately 800 Oe, forming horizontal magnetic field lines pointing from the N pole to the S pole. The mold containing the powder was then rotated at 60 r / min for 7 minutes, allowing the powder to be driven by the magnetic torque under the horizontal magnetic field, achieving a preferred orientation of the particles along the magnetic field lines. This operation was repeated until all 0.3g of powder was added to the mold and oriented correctly.

[0139] Step 7, Shaping:

[0140] The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 5 MPa.

[0141] Step 8, Sintering:

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

[0143] The phase composition, orientation factor, microstructure, and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 8 were characterized. Tests showed that the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example was 0.536, and it exhibited significant anisotropy along the hysteresis loops of the ceramic surface and cross-section.

[0144] Comparative Example

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

[0146] Step 1, Ingredients:

[0147] Using BaCO3, Co2O3, and Fe2O3 as raw materials, according to 0.0042 mol Co2Z ferrite (Ba3Co2Fe 24 O 41 The stoichiometric ratio of the ingredients was used to calculate the proportions, and 2.537g of BaCO3, 0.711g of Co2O3 and 8.213g of Fe2O3 were weighed to obtain a mixed raw material powder.

[0148] Step 2, First ball milling:

[0149] The mixed raw material powder obtained in step 1 is mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:1.2:3.5, and then placed in a ball mill at 400 r / min for 12 hours to make it uniformly mixed, so as to obtain a slurry after one ball milling.

[0150] Step 3, Preheating:

[0151] The ball-milled slurry obtained in step 2 was dried in a 60°C oven and then sintered in a muffle furnace at 1225°C for 3 hours to obtain Co2Z ferrite pre-calcined powder.

[0152] Step 4, Secondary ball milling:

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

[0154] Step 5, Shaping:

[0155] After drying the slurry obtained from the secondary ball milling in step 4 in a 60℃ oven, 0.3g of powder was weighed and pressed into shape under a uniaxial pressure of 5MPa to obtain a green body.

[0156] Step 6, Sintering:

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

[0158] The phase composition, orientation factor, microstructure, and magnetic anisotropy of the polycrystalline Co2Z ferrite ceramic obtained in step 6 were characterized. Testing showed that the orientation factor of the Co2Z ferrite ceramic prepared in the comparative example was 0.101, and its cross-sectional particles were not oriented along the easy magnetization direction. Figure 5 The figures show the hysteresis loops of the Co2Z ferrite ceramics obtained for comparison, in directions perpendicular to and parallel to the c-axis. As can be seen from the figures, the Co2Z ferrite ceramics do not exhibit significant magnetic anisotropy.

[0159] In summary, this invention, based on the traditional solid-state reaction sintering process, introduces a weak magnetic field-driven and particle size-controlled preferred orientation process to achieve the preparation of textured Co2Z ferrite ceramics. This process induces particles to align along the easily magnetized direction under the combined action of centrifugal force and magnetic force by rotating a mold in a weak magnetic field provided by a NdFeB permanent magnet. Combined with particle size control, the magnetic response and tumbling ability of the particles are optimized, and (00l) preferred-oriented Co2Z ferrite ceramics are prepared by sintering. The particles in this textured ceramic are oriented along the easily magnetized direction and exhibit significant magnetic anisotropy. These results fully demonstrate that the weak magnetic field-driven and particle size-controlled process of this invention can effectively construct textured Co2Z ferrite ceramics, providing a new approach and key technical path for the low-energy, low-cost preparation of high-performance magnetic dielectric materials.

[0160] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing Z-type ferrite ceramics, characterized in that, The specific steps are as follows: Step 1, Ingredients: Using BaCO3, Co2O3, and Fe2O3 as raw materials, based on Co2Z ferrite Ba3Co2Fe 24 O 41 The formula is calculated by stoichiometry and the raw materials are weighed to obtain 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 at a mass ratio of 1:(1-1.5):(3-6), and then ball-milled in a ball mill at 300 r / min-500 r / min for 10-14 hours to make it uniformly mixed, so as to obtain the slurry after one ball milling. Step 3, Preheating: The ball-milled slurry obtained in step 2 is dried in an oven at 50-80℃, and then sintered in a muffle furnace at 1150℃-1250℃ for 2-5 hours to obtain Co2Z ferrite pre-calcined powder. Step 4, sieve particle size: The pre-calcined Co2Z ferrite powder from step 3 is ground and then sieved to obtain Co2Z ferrite particles of 38-50μm. Step 5, Secondary ball milling: The uniform Co2Z ferrite particles obtained in step 4 are mixed with deionized water and zirconium dioxide grinding media at a mass ratio of 1:(1-1.5):(3-6), and then ball-milled in a ball mill at 300 r / min-500 r / min for 10-14 hours to obtain a slurry after secondary ball milling. Step 6: Weak magnetic field drives directional alignment: The secondary ball-milled slurry obtained in step 5 is dried in an oven at 50–80°C to obtain a dry powder. The dry powder is then divided into equal portions, and 6.67–36.7 wt% of the powder from each portion 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 measured to be 100 Oe–800 Oe by a gaussmeter. The mold is rotated at 40–70 r / min for 3–7 minutes to cause the Co2Z ferrite particles to align in a specific direction under the action of the magnetic field lines, forming an oriented powder. This operation is repeated until all the powder from each portion is added to the mold and oriented. Step 7, Shaping: The oriented powder obtained in step 6 is pressed into a green body under a uniaxial pressure of 4-10 MPa. Step 8, Sintering: The green body prepared in step 7 was sintered in a muffle furnace at 1100℃-1300℃ for 2-5 hours to obtain Co2Z ferrite ceramic.

2. The method for preparing Z-type ferrite ceramics according to claim 1, characterized in that, In step 4, Co2Z ferrite particles of 38-50μm are obtained by particle size sieving. The specific operation method is as follows: the particles are sieved through 200-mesh, 300-mesh and 400-mesh stainless steel screens in sequence to obtain Co2Z ferrite particles of 38-50μm.

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