Low-loss oriented BaM hexagonal ferrite material covering sub-6 GHz frequency band and preparation method of low-loss oriented BaM hexagonal ferrite material

Abstract

The invention discloses a low-loss oriented BaM hexagonal ferrite material covering a sub-6 GHz frequency band and a preparation method thereof, based on a BaM hexagonal ferrite material jointly substituted by Co < 2 + > and Ru < 4 + > ions with uniaxial anisotropy, goethite powder which is synthesized by a hydrothermal method and has a high length-diameter ratio is used as a raw material, iron oxide red (Fe2O3) required in a traditional ferrite preparation process is replaced, and the low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band and the preparation method of the low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band are obtained. And the BaM hexagonal ferrite jointly replaced by Co < 2 + > / Ru < 4 + > ions realizes orientation preferred growth, so that the magnetic resonance frequency is greatly improved, and the requirement of a low-loss sub-6GHz miniaturized antenna on high working frequency is met. Secondly, by adding low-melting-point Bi2O3, the particle size and the magnetic domain width are increased, so that the domain wall resonance relaxation frequency can be reduced, natural resonance points and domain wall resonance points are obviously separated, and the low magnetic loss characteristic of the material is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of communication equipment substrates, and relates to a ferrite material with high operating frequency and low magnetic / dielectric loss and a preparation method thereof, and specifically to a low-loss oriented BaM hexagonal ferrite material that can cover the sub-6 GHz frequency band and a preparation method thereof. Background Art

[0002] Antennas, as core components of communication systems, are indispensable for transmitting electromagnetic signals and are widely used in fields such as autonomous driving, photovoltaics, remote sensing radar, medical equipment, and the Internet of Things. Recently, the vigorous development of 5G technology has created a great demand for high-frequency miniaturized antennas. Generally speaking, the use of high-dielectric materials as antenna substrates can reduce the wavelength of electromagnetic waves in the substrate, thereby reducing the size of the antenna. However, the high-dielectric materials used in this technology not only cause serious mismatches between the material impedance and the environmental impedance, but also induce surface wave excitation. These disadvantages will deteriorate the performance of the antenna.

[0003] Compared with traditional high dielectric materials, magnetic dielectric materials with a magnetic permeability higher than 1 and a matching dielectric constant can significantly improve impedance matching characteristics and achieve miniaturization of antennas. Among many magnetic dielectric materials, microwave ferrites with high resistivity, high magnetic permeability and high cutoff frequency have received great attention in the industry. For microwave ferrites, due to the Snoek limit, a compromise needs to be made between high magnetic permeability and high magnetic resonance frequency. Maximum operating frequency ( f Performance factor at 0 PF ) is an important parameter to measure the high-frequency magnetic properties of microwave ferrites used in the field of miniaturized antennas. PF Higher values ​​indicate that the material can achieve low magnetic losses at higher frequencies.

[0004] Generally, microwave ferrites used in the field of miniaturized antennas can be divided into two categories, one is spinel ferrite and the other is hexagonal ferrite. Limited by the lower magnetocrystalline anisotropy, the magnetic loss tangent of spinel ferrite will increase significantly above 1.0 GHz. The performance factor of this type of material is usually low and is mainly suitable for HF and VHF bands. For example, patent CN110078492B uses Pr 3+ MgCd ferrite was prepared by ion doping, which has almost equal real part of magnetic permeability and real part of dielectric constant (24.0~27.0) in 1~30 MHz, and magnetic loss and dielectric loss tangent are both less than 0.1. PF The value is 7.2~8.1GHz.

[0005] According to the easy magnetization direction and the angle between the c-axis of the unit cell, hexagonal ferrite can be divided into uniaxial type, planar type and conical type. Thanks to the advantage of high magnetic permeability, researchers usually use the method of metal ion substitution to adjust the high-frequency magnetism of planar hexagonal ferrite. For example, patent CN106573848A uses Co 2+ and Ir 4+ By ion substitution, Co2Z and Co2Y hexagonal ferrite composites were prepared. In the 0.65~0.85 GHz frequency band, the real part of the magnetic permeability is 4.6~7.5, the real part of the dielectric constant is 6.5~8.1, the magnetic loss tangent is 0.07~0.29, and the dielectric loss tangent is 0.05~0.09. PF The value is 36.0 GHz. Patent US11827527B2 uses Bi 3+ 、Co 2+ And Ru 4+ The BaM hexagonal ferrite with planar anisotropy was prepared by ion joint substitution. In the 1.0~2.0 GHz frequency band, the real part of the magnetic permeability is 2.9~3.3, the real part of the dielectric constant is 10.8~11.3, the magnetic loss tangent is 0.05~0.25, and the dielectric loss tangent is 0.013~0.04. PF The value is 33.7~53.0 GHz. Recently, researchers have discovered a new type of hexagonal ferrite crystal phase - 18H hexagonal ferrite, whose magnetic resonance frequency is much higher than that of traditional planar hexagonal ferrite, which makes it possible to meet the application needs of miniaturized antenna substrates in the S and C bands. For example, patent CN117228734B has developed a low-loss CoZn-18H planar hexagonal ferrite with ultra-high magnetic resonance frequency through a chemical co-precipitation method. In the frequency band of 0.82~4.97 GHz, the real part of the magnetic permeability is 1.38~2.01, the real part of the dielectric constant is 11.0~15.5, and the magnetic loss tangent does not exceed 0.10. PF The values ​​are 16.5~68.6 GHz. The hexagonal ferrites reported above are all planar hexagonal ferrites, and their maximum operating frequencies do not exceed 6.0 GHz, which is not conducive to the miniaturization application of low-loss sub-6 GHz antennas. Summary of the invention

[0006] In view of this, the present invention discloses a lossy BaM hexagonal ferrite material with uniaxial anisotropy that can cover the entire sub-6 GHz frequency band and a preparation method thereof, so as to achieve high operating frequency and low dielectric loss of the material and meet the miniaturized application requirements of sub-6 GHz antennas.

[0007] To achieve the above object, the present invention adopts the following technical solution: A low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band, with the chemical formula of BaCo 1.2 Ru 0.2 Fe 10.9 O 19 The preparation method comprises the following steps: 1) According to the chemical formula BaCo 1.2 Ru 0.2 Fe 10.9 O 19 BaCO3, Co3O4, RuO2 and goethite powder are weighed as raw materials according to the stoichiometric ratio of each element, and then sintering aid Bi2O3 accounting for 1-5 wt% of the total weight of the raw materials is added to the raw materials and mixed evenly to form a raw material mixture; The preparation method of the goethite powder is as follows: first, a NaOH solution with a concentration of 4 to 6 M is added dropwise to a 0.3 to 0.5 M ferric nitrate solution at a rate of 1 to 2 drops per second, and the total amount of the added solution is between 69 and 84 mL to form a mixed solution; then, the mixed solution is heated to 60 to 150 ° C and kept warm for 64 to 80 hours after the reaction is completed, and then naturally cooled to room temperature, and the obtained product is repeatedly washed and centrifuged with deionized water and anhydrous ethanol for multiple times until the pH of the supernatant of the solution is neutral; finally, the precipitate after centrifugation is placed in a 60 ° C oven to dry overnight, and then taken out and ground into fine powder to obtain the goethite powder.

[0008] 2) The raw material mixture in step 1) and the polyvinyl alcohol aqueous solution are mixed and granulated at a mass ratio of 4-9:1 to obtain coarse particles; the mass concentration of the polyvinyl alcohol aqueous solution is 7%-9%.

[0009] 3) using a mold to press the coarse particles obtained in step 2) into discs or annular blocks, the molding pressure is 1000-1540 MPa, the pressure holding time is 3-30 min, and a block sample is obtained; 4) placing the block sample in step 3) in a tubular sintering furnace with oxygen flow at a ventilation rate of 0.1-0.3 L / min, heating to 900-1060°C at a rate of 1-5°C / min, and sintering for 3-5 h to obtain the low-loss oriented BaM hexagonal ferrite material.

[0010] The present invention is based on Co with uniaxial anisotropy 2+ And Ru 4+ The BaM hexagonal ferrite material with ion-combined substitution uses hydrothermally synthesized goethite powder with a high aspect ratio as raw material, replacing the iron red (Fe2O3) required in the traditional ferrite preparation process, making Co 2+ / Ru 4+The BaM hexagonal ferrite with co-substituted ions achieves orientation-preferred growth, thereby greatly improving the magnetic resonance frequency and meeting the requirements of low-loss sub-6GHz miniaturized antennas for high operating frequencies. Secondly, by adding low-melting-point Bi2O3, the particle size and magnetic domain width are increased, which can reduce the domain wall resonance relaxation frequency, resulting in a clear separation between the natural resonance point and the domain wall resonance point, ensuring the low magnetic loss characteristics of the material. Therefore, the present invention is based on a Co with uniaxial anisotropy 2+ And Ru 4+ Ion-co-substituted BaM hexagonal ferrite, achieved Co by goethite powder with high shape anisotropy 2+ / Ru 4+ The BaM hexagonal ferrite with co-ion substitution grows preferentially in an orientation, achieving an ultra-high magnetic resonance frequency. The particle size and magnetic domain width are increased by using Bi2O3 additives, achieving low magnetic loss characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The figure is a flow chart for preparing low-loss BaM hexagonal ferrite materials covering the sub-6 GHz frequency band according to the present invention; wherein: (a) is a schematic diagram for preparing goethite powders with different aspect ratios (7.3-9.0); (b) is a schematic diagram for preparing low-loss oriented BaM hexagonal ferrite materials; and (c) is a schematic diagram for the orientation arrangement of goethite powders after applying uniaxial pressure.

[0012] Figure 2 In the figure, (a) is a schematic diagram of the preparation of the composite sample by the rotating magnetic field orientation device; (b) is the X-ray diffraction pattern of the samples obtained from Comparative Example 1 (marked No. 1) and Comparative Example 2 (marked No. 6); (c) is the initial magnetization curve of the sample obtained from Comparative Example 2 (marked No. 6) along the in-plane and out-of-plane directions.

[0013] Figure 3 This is the X-ray diffraction pattern of the sample obtained in Example 1.

[0014] Figure 4 The X-ray diffraction patterns of the samples obtained in Comparative Example 1 (marked No. 1), Example 2 (marked No. 2) and Example 3 (marked No. 3) are shown.

[0015] Figure 5 The real part, imaginary part and real part of the complex magnetic permeability and the complex dielectric constant of the samples obtained in Comparative Example 1 (marked No. 1), Example 2 (marked No. 2) and Example 3 (marked No. 3).

[0016] Figure 6 The magnetic loss tangent and dielectric loss tangent of the samples obtained from Comparative Example 1 (marked No. 1), Example 2 (marked No. 2) and Example 3 (marked No. 3).

[0017] Figure 7 The real part, imaginary part and magnetic loss tangent of complex magnetic permeability of Example 3 (marked No. 3), Example 4 (marked No. 4) and Example 5 (marked No. 5). DETAILED DESCRIPTION

[0018] The present invention is further explained below with reference to specific embodiments.

[0019] Example 1 Weigh 40.0 g (0.099 mol) Fe(NO3)3∙9H2O and dissolve it in 250 mL deionized water, and mix it evenly with a stirring rod. Weigh 20.0 g (0.5 mol) NaOH and dissolve it in 100 mL deionized water, and mix it evenly with a stirring rod. Then, use a measuring cylinder to measure 79 mL of NaOH aqueous solution. Then, use a dropper to add the measured NaOH aqueous solution drop by drop into the Fe(NO3)3∙9H2O aqueous solution. After the dropwise addition is completed, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined stainless steel reactor, and place the reactor in an oven at 60, 120, and 150°C for 72 h. After the reaction is completed, cool it to room temperature with the oven. After that, use deionized water and anhydrous ethanol to repeatedly centrifuge and wash the obtained product 9 times until the pH of the supernatant of the solution is 7.0. The precipitate after centrifugation was placed in an oven at 60° C. and dried for 24 h, and ground into fine powder to obtain the sample of Example 1.

[0020] Example 2 Weigh 0.82 g (0.00415 mol) BaCO3, 0.40 g (0.00166 mol) Co3O4, 0.11 g (0.000826 mol) RuO2, and 4.03 g (0.0453 mol) of goethite powder prepared at 150 ° C in Example 1. Put all the above raw materials into a mixer and mix for 1 h to form a raw material mixture. After that, weigh 1.6 g of the raw material mixture and 0.4 g of 8% wt polyvinyl alcohol aqueous solution, mix the two and granulate to obtain coarse particles. Weigh 0.25 g of coarse particles, pour them into a mold with an outer diameter of 7.5 mm and an inner diameter of 3.0 mm, press them under an axial pressure of 1270 MPa for 4 min, and take them out to obtain a ring sample. Weigh 1.1 g of coarse particles, pour them into a circular mold with a diameter of 15 mm, press them under an axial pressure of 1270 MPa for 30 min, and take them out to obtain a disc sample. The two block samples were placed in a tubular sintering furnace with oxygen flowing at a ventilation rate of 0.1 L / min, sintered at 980 °C for 4 h, and a heating rate of 2 °C / min to obtain the sample of Example 2.

[0021] Example 3 Weigh 0.82 g (0.00415 mol) BaCO3, 0.40 g (0.00166 mol) Co3O4, 0.11 g (0.000826 mol) RuO2, 4.03 g (0.0453 mol) of goethite powder prepared at 150°C in Example 1, and 0.15 g (0.000322 mol) Bi2O3. Put all the above raw materials into a mixer and mix for 1 h to form a raw material mixture. After that, weigh 1.6 g of the raw material mixture and 0.4 g of 8% wt polyvinyl alcohol aqueous solution, mix the two and granulate to obtain coarse particles. Weigh 0.25 g of the coarse particles, pour them into a mold with an outer diameter of 7.5 mm and an inner diameter of 3.0 mm, press them for 4 minutes under an axial pressure of 1270 MPa, and take them out to obtain a ring-shaped sample. Weigh 1.1 g of the coarse particles, pour them into a circular mold with a diameter of 15 mm, press them under an axial pressure of 1270 MPa for 30 min, and then take them out to obtain a disc sample. The above two block samples are placed in a tubular sintering furnace with oxygen, the ventilation rate is 0.1 L / min, sintered at 980 °C for 4 h, and the heating rate is 2 °C / min to obtain the sample of Example 3.

[0022] Example 4 Weigh 0.82 g (0.00415 mol) BaCO3, 0.40 g (0.00166 mol) Co3O4, 0.11 g (0.000826 mol) RuO2, 4.03 g (0.0453 mol) of goethite powder prepared at 60°C in Example 1, and 0.15 g (0.000322 mol) Bi2O3. Put all the above raw materials into a mixer and mix for 1 h to form a raw material mixture. After that, weigh 1.6 g of the raw material mixture and 0.4 g of 8% wt polyvinyl alcohol aqueous solution, mix the two and granulate to obtain coarse particles. Weigh 0.25 g of the coarse particles, pour them into a mold with an outer diameter of 7.5 mm and an inner diameter of 3.0 mm, press them for 4 minutes under an axial pressure of 1270 MPa, and take them out to obtain a ring-shaped sample. Weigh 1.1 g of the coarse particles, pour them into a circular mold with a diameter of 15 mm, press them under an axial pressure of 1270 MPa for 30 min, and then take them out to obtain a disc sample. The above two samples are placed in a tubular sintering furnace with oxygen, the ventilation rate is 0.1 L / min, sintered at 980 °C for 4 h, and the heating rate is 2 °C / min to obtain the sample of Example 4.

[0023] Example 5 Weigh 0.82 g (0.00415 mol) BaCO3, 0.40 g (0.00166 mol) Co3O4, 0.11 g (0.000826 mol) RuO2, 4.03 g (0.0453 mol) of goethite powder prepared at 120 °C in Example 1, and 0.15 g (0.000322 mol) Bi2O3. Put all the above raw materials into a mixer and mix for 1 h to form a raw material mixture. After that, weigh 1.6 g of the raw material mixture and 0.4 g of 8% wt polyvinyl alcohol aqueous solution, mix the two and granulate to obtain coarse particles. Weigh 0.25 g of the coarse particles, pour them into a mold with an outer diameter of 7.5 mm and an inner diameter of 3.0 mm, press them for 4 min under an axial pressure of 1270 MPa, and take them out to obtain a ring sample. Weigh 1.1 g of the coarse particles, pour them into a circular mold with a diameter of 15 mm, press them under an axial pressure of 1270 MPa for 30 min, and then take them out to obtain a disc sample. The above two samples are placed in a tubular sintering furnace with oxygen, the ventilation rate is 0.1 L / min, sintered at 980 °C for 4 h, and the heating rate is 2 °C / min to obtain the sample of Example 5.

[0024] Comparative Example 1 Weigh 0.82 g (0.00415 mol) BaCO3, 0.40 g (0.00166 mol) Co3O4, 0.11 g (0.000826 mol) RuO2 and 3.62 g (0.0226 mol) Fe2O3. The raw material powders were placed in a ball mill and mixed evenly, with a ball-to-material ratio of 10:1, a ball mill speed of 200 r / min, and a ball milling time of 14 h to obtain a primary ball milling slurry, which was dried to obtain a primary ball milling powder; the primary ball milling powder was placed in a box muffle furnace and sintered at 1100°C for 4 h in an air atmosphere at a heating rate of 2°C / min to obtain a pre-burned material; then 3wt% of a Bi2O3 additive equivalent to the mass of the pre-burned material was added to the pre-burned material, and the material was placed in a ball mill and mixed evenly, with a ball-to-material ratio of 10:1, a ball mill speed of 250 r / min, and a ball milling time of 14 h to obtain a secondary ball milling slurry, which was dried to obtain a secondary ball milling powder; 1.6 g of the secondary ball milling powder and 0.4 g of an 8% wt polyvinyl alcohol aqueous solution were taken, and the two were mixed and granulated to obtain coarse particles. Weigh 0.25 g of the coarse particles, pour them into a mold with an outer diameter of 7.5 mm and an inner diameter of 3.0 mm, press them under an axial pressure of 1270 MPa for 4 min, and take them out to obtain a ring sample. Weigh 1.1 g of the coarse particles, pour them into a circular mold with a diameter of 15 mm, press them under an axial pressure of 1270 MPa for 30 min, and take them out to obtain a disc sample. The above two samples are placed in a tubular sintering furnace with oxygen, the ventilation rate is 0.1 L / min, sintered at 980 ° C for 4 h, and the heating rate is 2 ° C / min to obtain the sample of comparative example 1.

[0025] Comparative Example 2 The secondary ball-milled powder in Comparative Example 1 was placed in a tubular sintering furnace with oxygen, with a ventilation rate of 0.1 L / min, a sintering temperature of 980 ℃, a sintering time of 4 h, and a heating rate of 2 ℃ / min to obtain a secondary sintered powder and grind it; then 0.09 g of polyurethane particles (PU) were weighed and completely dissolved in 10 mL of acetone using an ultrasonic machine to form a mixed solution. After the PU was completely dissolved, 0.20 g of the secondary sintered powder was added to the mixed solution and ultrasonically dispersed evenly to form a suspension. When the suspension was in a semi-dry state, it was transferred to a mold, and the mold was placed in an external 2 T rotating magnetic field for orientation for 10 min, as shown in FIG. Figure 2 As shown in (a); after orientation is completed, the sample is placed in an oven to dry for 24 h.

[0026] The product structure characterization and performance evaluation are as follows: See attached Figure 1Goethite powders with different aspect ratios (7.3-9.0) (Example 1) and different BaM hexagonal ferrite material samples (Examples 2-5) were prepared. At the same time, in order to prove that the goethite powder prepared by the present invention can significantly improve the application frequency of BaM hexagonal ferrite materials, a ferrite sample prepared by a traditional ceramic method is provided (Comparative Example 1). In addition, in order to illustrate the formula (BaCo 1.2 Ru 0.2 Fe 10.9 O 19 ) itself has uniaxial anisotropy, and a composite sample prepared based on a traditional ceramic method is also provided (Comparative Example 2).

[0027] Figure 2 (b) is the X-ray diffraction pattern of the samples obtained in Comparative Example 1 (marked No. 1) and Comparative Example 2 (marked No. 6); Obviously, after the orientation treatment with the external rotating magnetic field, the diffraction peak intensity corresponding to the (006) and (008) crystal planes of the samples is significantly reduced, which indicates that the (00 l ) plane, the c-axis of the hexagonal unit cell, which is perpendicular to the plane, is mostly arranged along the in-plane direction under the action of the magnetic field orientation. Figure 2 (c) is the initial magnetization curve of the sample obtained in comparative example 2 (marked as No. 6) along the in-plane and out-of-plane directions; it can be seen that the magnetization direction is in the in-plane direction, that is, the easy magnetization direction is parallel to the c-axis direction of the hexagonal unit cell. The above results prove that the formula (BaCo 1.2 Ru 0.2 Fe 10.9 O 19 ) itself has uniaxial anisotropy.

[0028] Figure 3 1 is the X-ray diffraction pattern of goethite powder obtained at different reaction temperatures obtained in Example 1. It can be seen that the phase structures of the samples obtained at all temperatures are consistent with the standard goethite powder diffraction results (PDF#29-0713). Figure 4 The X-ray diffraction results of the samples obtained in Comparative Example 1, Example 2 and Example 3. It can be seen that compared with the samples prepared by the traditional ceramic method based on spherical Fe2O3 powder as raw material, the diffraction peak intensities of the (006), (008) and (0014) crystal planes of the samples prepared by using goethite powder as raw material are significantly enhanced, showing a significant preferred orientation.

[0029] Figure 5 (a) and (b) are the complex magnetic permeability spectra of the samples obtained in Example 1, Example 2 and Example 3. Obviously, compared with the samples prepared by the traditional ceramic method based on spherical Fe2O3 powder as raw material, the samples prepared by using goethite powder as raw material have higher magnetic resonance frequency. This is because after applying uniaxial pressure, the goethite particles are oriented (such as Figure 1(c) After high-temperature sintering, the oriented goethite particles and other raw materials react to generate oriented BaM hexagonal ferrite grains, achieving orientation-preferred growth, which leads to the enhancement of uniaxial magnetocrystalline anisotropy along the out-of-plane direction, significantly increasing the natural resonance frequency of the sample and significantly reducing the magnetic loss tangent in the sub-6GHz band, as shown in Figure 2. Figure 6 In addition, compared with the sample obtained in Example 2 without the additive Bi2O3, the sample obtained in Example 3 containing the additive Bi2O3 has a lower domain wall resonance relaxation frequency, which leads to a clear separation between the natural resonance frequency and the domain wall resonance frequency, thus ensuring the low magnetic loss characteristics of the material.

[0030] Figure 7 The real part, imaginary part and magnetic loss tangent of the complex magnetic permeability of the samples obtained in Examples 3 to 5. As the reaction temperature of the synthetic goethite raw material increases, the natural resonance frequency gradually increases, which gradually reduces the magnetic loss tangent of the sample in the sub-6GHz frequency band. This shows that by changing the reaction temperature required for the synthetic goethite raw material, the magnetic spectrum and magnetic loss characteristics of the oriented BaM hexagonal ferrite material can be effectively regulated.

[0031] Table 1 shows the real part μ′ of the magnetic permeability and the magnetic loss tangent tan of the samples prepared in Examples 2-5 and Comparative Example 1. δ μ , the real part of the dielectric constant ε′, the dielectric loss tangent tan δ ε , Maximum operating frequency f 0 and performance factor PF .

[0032] Table 1 Performance parameters of samples prepared in Examples 2-5 and Comparative Example 1 As shown in Table 1, by comparing Comparative Example 1 and Example 3, it can be seen that the use of goethite with a high aspect ratio can make f 0 from 0.82 GHz to 7.5 GHz, PF The value increased from 23.7 GHz to 98.2 GHz, which shows that the use of goethite powder as a raw material can successfully achieve the goal of covering the entire Sub-6 GHz frequency band with the highest operating frequency. Secondly, by comparing Example 2 and Example 3, it can be seen that f 0 from 4.17 GHz to 7.5 GHz, PF The value increased from 54.6 GHz to 98.2 GHz, which shows that the addition of sintering aid Bi2O3 can greatly increase the maximum operating frequency and effectively suppress the magnetic loss at high frequency. Finally, by comparing Examples 3, 4, and 5, it can be seen that as the reaction temperature of the synthetic goethite raw material increases, f0 from 1.84 GHz to 7.5 GHz, PF The value increased from 32.4 GHz to 98.2 GHz, which shows that the high-frequency magnetism of oriented BaM hexagonal ferrite materials can be effectively controlled by adjusting the synthesis temperature of goethite powder.

[0033] In summary, the present invention is based on Co with uniaxial anisotropy 2+ And Ru 4+ The BaM hexagonal ferrite material with ion co-substituted is prepared with hydrothermally prepared goethite powder as raw material, and combined with low melting point Bi2O3 addition technology, it can cover the entire sub-6 GHz frequency band with high magnetic permeability (1.3≤μ′≤1.8), low dielectric constant (5.2≤ε′≤6.6), low magnetic dielectric loss (tan δ μ ≤0.10,tan δ ε ≤0.026). Its magneto-dielectric loss in the entire sub-6 GHz frequency band is lower than that of most existing polycrystalline hexagonal ferrites. These results demonstrate the feasibility of using goethite powder with high shape anisotropy as a raw material to prepare uniaxially anisotropic low-loss oriented BaM hexagonal ferrite covering the sub-6 GHz frequency band, providing a material basis for designing miniaturized antennas based on magneto-dielectric materials that can be used in the sub-6 GHz frequency band.

Claims

1. A low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band, characterized in that: The chemical formula of the BaM hexagonal ferrite material is BaCo 1.2 Ru 0.2 Fe 10.9 O 19 .

2. A method for preparing a low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band as claimed in claim 1, characterized in that: The following steps are involved: 1) According to the chemical formula BaCo 1.2 Ru 0.2 Fe 10.9 O 19 BaCO3, Co3O4, RuO2 and goethite powder are weighed as raw materials according to the stoichiometric ratio of each element, and then sintering aid Bi2O3 accounting for 1-5 wt% of the total weight of the raw materials is added to the raw materials and mixed evenly to form a raw material mixture; 2) mixing the raw material mixture in step 1) and the polyvinyl alcohol aqueous solution in a mass ratio of 4 to 9:1 to obtain coarse particles; 3) using a mold to press the coarse particles obtained in step 2) into discs or annular blocks, the molding pressure is 1000-1540 MPa, the pressure holding time is 3-30 min, and a block sample is obtained; 4) placing the block sample in step 3) in a tubular sintering furnace with oxygen flow at a ventilation rate of 0.1-0.3 L / min, heating to 900-1060°C at a rate of 1-5°C / min, and sintering for 3-5 h to obtain the low-loss oriented BaM hexagonal ferrite material.

3. A method for preparing a low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band as claimed in claim 2, characterized in that: In step 1), the preparation method of the goethite powder is as follows: first, a NaOH solution with a concentration of 4 to 6 M is added dropwise to a 0.3 to 0.5 M ferric nitrate solution at a rate of 1 to 2 drops per second, and the total amount of the addition is between 69 and 84 mL to form a mixed solution; then the mixed solution is heated to 60 to 150 ° C and kept warm for 64 to 80 hours after the reaction is completed, and then naturally cooled to room temperature, and the obtained product is repeatedly washed and centrifuged with deionized water and anhydrous ethanol for multiple times until the pH of the supernatant of the solution is neutral; finally, the precipitate after centrifugation is placed in a 60 ° C oven to dry overnight, taken out and ground into fine powder to obtain the goethite powder.

4. A method for preparing a low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band as claimed in claim 2, characterized in that: In step 2), the mass concentration of the polyvinyl alcohol aqueous solution is 7% to 9%.

5. A use of the low-loss oriented BaM hexagonal ferrite material covering the sub-6 GHz frequency band as claimed in claim 1 in an antenna substrate.

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