High-power and low-loss LiZn microwave ferrite material and preparation method thereof

Abstract

The application belongs to the technical field of electronic materials, and discloses a high-power and low-loss LiZn microwave ferrite material, raw materials of which include main materials and dopants, the main materials include Li2CO3, ZnO, MnCO3, CuO, NiO and Fe2O3, and the dopants include Bi2O3, CaCO3 and Co2O3; a preparation method thereof includes: primary ball milling and pre-sintering of the main materials to obtain pre-sintered powder; secondary ball milling of the pre-sintered powder after adding the dopants; granulation of the secondary ball-milled material after adding an organic binder, and compression into a blank; sintering of the blank to obtain the high-power and low-loss LiZn microwave ferrite material; and the specific formula and preparation process can ensure uniform composition and grain refinement, and finally prepare a microwave ferrite material with high Curie temperature, low ferromagnetic resonance line width, low dielectric loss and high spin wave line width.

Description

Technical Field

[0001] This invention belongs to the field of electronic materials technology, and in particular relates to a high-power, low-loss LiZn microwave ferrite material and its preparation method. Background Technology

[0002] Electronic systems for radar, satellite, and communication equipment have two important development directions: low power consumption and beyond-line-of-sight (BLS) transmission and reception. Circulators and phase shifters, as key components of numerous transceiver antennas in 5G base stations and phased array radar systems, play a crucial role in the entire system. Microwave ferrite materials are the core factor for microwave ferrite devices such as circulators / phase shifters, determining their performance in terms of bandwidth, insertion loss, isolation, and high power handling capability. Therefore, to achieve the goals of low power consumption and BLS transmission and reception, it is necessary to reduce the insertion loss of circulators / phase shifters while increasing their power handling capability. This requires microwave ferrite materials to have low ferromagnetic resonance linewidth (FLR). H Low dielectric loss (tan) δ ε ) and high spin wave linewidth ( H k This is also a current hot topic and trend in microwave ferrite technology research.

[0003] LiZn ferrites possess advantages such as a wide adjustable range of saturation magnetization, high Curie temperature, and good square magnetic properties. However, their high ferromagnetic resonance linewidth and dielectric loss result in high insertion loss in the devices. Furthermore, their relatively small spin wavelinewidth makes it difficult to handle high power. Ferromagnetic resonance linewidth and spin wavelinewidth are mutually restrictive technical bottlenecks, and low loss and high power are performance indicators that are difficult to achieve simultaneously.

[0004] In existing technologies, ferrite preparation is mainly based on Li-Zn-Ti. However, Li ions are prone to volatilization during high-temperature sintering. To reduce the problem of high-temperature volatilization of Li ions, Bi2O3 is usually added as a low-temperature sintering aid to reduce the sintering temperature. For example, application number 202410208567.1. However, the saturation magnetization of its product is 3900Gs±3%, which is at a medium level and limits high-power applications. The Curie temperature Tc>300℃, which can only meet the requirements of conventional communication equipment (operating temperature -40~85℃). Under high-temperature environments, the magnetic properties will significantly decay (e.g., 4πMs decreases linearly with increasing temperature), making it unsuitable for high-temperature operating environments.

[0005] To meet the high power and low insertion loss requirements of circulators / phase shifters in 5G base stations and phased array radars, it is of great significance to develop LiZn ferrites with excellent electromagnetic properties, such as high Curie temperature, high spin linewidth, low ferromagnetic resonance linewidth, and low dielectric loss, in order to reduce the insertion loss of microwave ferrite devices and improve their power handling capability. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a high-power, low-loss LiZn microwave ferrite material and its preparation method.

[0007] To solve the above-mentioned technical problems, the core idea of ​​this invention is that low loss is mainly achieved by reducing dielectric loss and ferromagnetic resonance linewidth: wherein dielectric loss is related to the Fe content in the material. 2+ The content of ions is closely related; iron deficiency in the formula can effectively inhibit Fe. 2+ The generation of ferromagnetic resonance (FIR) materials reduces dielectric loss. The FIR linewidth is primarily influenced by intrinsic linewidth, surface roughness, magnetocrystalline anisotropy, and porosity. Increasing material density and reducing the magnetocrystalline anisotropy constant can effectively lower the FIR linewidth. High power applications require materials with high spin wave linewidths, which can be improved by refining grains and adding fast relaxor ions. This invention combines systematic technological innovations in material formulation design, microstructure control, and magnetic-dielectric performance coupling optimization, overcoming the long-standing technical bottleneck of achieving both low-loss and high-power ferrite materials.

[0008] The technical solution proposed in this invention is as follows:

[0009] A high-power, low-loss LiZn microwave ferrite material with a spin wavelinewidth H k >17Oe; its raw materials include main materials and dopants, wherein the main materials include Li2CO3, ZnO, MnCO3, CuO, NiO and Fe2O3; and the dopants include Bi2O3, CaCO3 and Co2O3.

[0010] Furthermore, based on molar percentage, the main materials include 8.7~14.1 mol% Li2CO3, 3.4~15.1 mol% ZnO, 2.8~3.6 mol% MnCO3, 0.3~1.2 mol% CuO, 1.8~10.4 mol% NiO, and 65.3~75.5 mol% Fe2O3.

[0011] This invention creatively introduces NiO and CuO into the main formulation of LiZn ferrite, forming a Li-Zn-Ni-Cu quaternary composite ferrite system. The introduction of Ni helps to reduce the magnetocrystalline anisotropy constant, thereby reducing the ferromagnetic resonance linewidth. H This achieves low loss; the introduction of Cu can lower the sintering temperature, promote densification, and reduce porosity. Simultaneously, it works synergistically with NiO in the LiZn matrix, not only helping to reduce... H This actually increases the spin wave linewidth; at the same time, the main component is still LiZn, ensuring that the material still has a high Curie temperature. T c The inherent advantages of (>420℃).

[0012] Furthermore, based on molar percentage, the dopant comprises 0.05~0.30wt% Bi2O3, 0.05~0.25wt% CaCO3 and 0.0025~0.01wt% Co2O3, which constitute 0.05~0.30wt% of the main material.

[0013] In this invention, Bi₂O₃, as a low-temperature sintering aid, forms a liquid phase, greatly promoting grain growth and densification, thereby reducing porosity and minimizing [the effects of sintering on grain density]. H CaCO3 can refine grains, increase grain boundary resistivity, and significantly reduce dielectric loss; the cobalt ions in Co2O3 are "fast relaxor ions," which can effectively increase the magnetocrystalline anisotropy field, thereby significantly increasing the spin linewidth. H k This is the key to achieving high power capacity.

[0014] These three dopants were selected and their proportions were precisely controlled. The three work synergistically to improve the material's performance.

[0015] Furthermore, its raw materials also include an organic binder, wherein the organic binder is PVA, and the amount added is 10-20% of the total mass of the main material and dopants.

[0016] Based on a general inventive concept, the present invention also provides a method for preparing the above-mentioned high-power, low-loss LiZn microwave ferrite material, comprising the following steps:

[0017] (1) The main material is ball-milled and pre-fired once to obtain pre-fired powder;

[0018] (2) Add a dopant to the pre-calcined powder and perform secondary ball milling;

[0019] (3) Add organic binder to the secondary ball milling material after step (2) for granulation and press it into blanks;

[0020] (4) The blank is sintered to obtain the high-power, low-loss LiZn microwave ferrite material.

[0021] Furthermore, in step (1), the ball milling speed is 200~400 rpm and the ball milling time is 3~6h.

[0022] Furthermore, in step (1), the pre-firing temperature is 830~920℃ and the pre-firing time is 2~4h.

[0023] Furthermore, in step (2), the rotation speed of the secondary ball mill is 200~400 rpm, and the time is 4~8h.

[0024] Furthermore, in step (3), the molding pressure is 80~150MPa and the holding pressure is 20~50s.

[0025] Furthermore, in step (4), the sintering temperature is 1000~1120℃, and the sintering holding time is 2~6h.

[0026] In the preparation method of this invention, a two-step ball milling method is adopted, which involves ball milling and pre-calcination to ensure that the main materials are fully mixed and undergo solid-phase reaction to generate the desired ferrite phase. After adding the dopant, a second ball milling is performed to uniformly disperse the dopant into the pre-calcined powder and effectively refine the grain size. This step-by-step ball milling process ensures high uniformity of composition and ideal microstructure.

[0027] In the preparation method of the present invention, the doping step is placed after pre-calcination and before secondary ball milling, rather than at the beginning. On the one hand, this can avoid the possibility that low-melting-point substances such as Bi2O3 may volatilize or become ineffective during the pre-calcination process if added too early. On the other hand, this order of addition can ensure that the dopant mainly acts on the grain boundaries, so as to better exert its modifying effect without affecting the formation of the main crystalline phase.

[0028] In the preparation method of the present invention, a relatively low sintering temperature (1000~1120℃) and a suitable holding time (2~6h) are selected, which can ensure that the dopant can play a role in assisting sintering and achieving densification, while preventing excessive grain growth.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] (1) This invention, through a specific Li-Zn-Ni-Cu main component system and Bi-Ca-Co composite dopant formulation, employs a "two-step ball milling" and "post-doping" preparation process to ensure uniform composition and refined grains, ultimately producing a high Curie temperature ( ). T c >420℃), low ferromagnetic resonance linewidth ( H <270 Oe), low dielectric loss (tan tan ) δ ε <5×10 -4) and high spin linewidth ( H k Microwave ferrite materials with >17 Oe have met the urgent needs of 5G and phased array radar for high-performance microwave devices.

[0031] (2) The microwave circulators, phase shifters and other devices prepared based on the high-power, low-loss LiZn microwave ferrite material of the present invention can simultaneously achieve low insertion loss and high power handling capability. This will help reduce the overall power consumption of 5G base stations and phased array radar systems, extend device life, and significantly improve the reliability of their beyond-line-of-sight transmission and reception. This is of great significance to promoting the development of advanced communication and radar technologies.

[0032] (3) The preparation method of the present invention adopts the traditional solid-phase process route, which does not require special or expensive equipment. The production process is stable and the parameter control is clear, which is very suitable for large-scale industrial production and has a high market transformation prospect and economic benefit potential. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the LiZn ferrite material in Example 4.

[0034] Figure 2 This is a scanning electron microscope image of the LiZn ferrite material from Example 7.

[0035] Figure 3 This is a scanning electron microscope image of the LiZn ferrite material from Example 12. Detailed Implementation

[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0039] The following section describes the properties of LiZn microwave ferrite materials, including saturation magnetization 4. πM s With Curie temperature T c The ferromagnetic resonance linewidth was measured using a VSM-300 from Changchun Yingpu Magnetoelectric Technology Development Co., Ltd. H Tested at 9.25 GHz using the DH811B from Beijing Dahua Radio Instrument Factory according to GB / T9633—2012 standard. Φ 0.8mm spherical sample, dielectric constant ε 、 With dielectric loss tan δ ε The spin wave linewidth of a cylindrical sample was measured at 9.25 GHz using a DH406B radio instrument manufactured by Beijing Dahua Radio Instrument Factory, according to the GB / T9633—2012 standard. ΔH k Tested at 9.25 GHz using the spin wave testing system of Chengdu Enchi Microwave Technology Co., Ltd. according to GB / T9633—2012 standard. Φ 0.6mm small ball sample.

[0040] Examples 1-4:

[0041] The raw material composition of the high-power, low-loss LiZn microwave ferrite materials in Examples 1-4 is shown in Table 1.

[0042] Table 1 Raw material components of Examples 1-4

[0043]

[0044] The preparation method of the high-power, low-loss LiZn microwave ferrite material in Examples 1-4 includes the following steps:

[0045] (1) Li2CO3, ZnO, MnCO3, NiO, CuO and Fe2O3 were mixed in proportion as shown in Table 1, ball milled at 300 rpm for 3 hours, mixed evenly, dried, and finally pre-calcined at 850℃ for 2.5 hours to obtain a pre-calcined material;

[0046] (2) Add 0.1wt% Bi2O3, 0.18wt% CaCO3 and 0.005wt% Co2O3 to the pre-calcined material obtained in step (1), and then ball mill the mixture for 6 hours at 300 rpm.

[0047] (3) Add 15wt% organic binder PVA to the secondary ball milling material obtained in step (2) to granulate, and press it into a blank (forming pressure is 120MPa, holding pressure for 30s).

[0048] (4) The blank is sintered at 1020℃ for 2 hours to obtain high-power, low-loss LiZn microwave ferrite material.

[0049] The performance test results of the LiZn microwave ferrite materials in Examples 1-4 are shown in Table 2. Within this ratio range, as the Ni-Cu ratio increases, the ferromagnetic resonance linewidth decreases significantly, the spin wave linewidth increases slightly, and the dielectric loss also decreases slightly. The SEM image of the LiZn microwave ferrite material prepared in Example 4 is shown below. Figure 1 As shown, the grains grow fully and uniformly, the grain pores have basically disappeared, and the microstructure is relatively dense.

[0050] Table 2 Performance test results of LiZn microwave ferrite material

[0051]

[0052] Examples 5-8:

[0053] The raw material composition of the high-power, low-loss LiZn microwave ferrite materials in Examples 5-8 is shown in Table 3.

[0054] Table 3 Raw material components of Examples 5-8

[0055]

[0056] The preparation method of the high-power, low-loss LiZn microwave ferrite material in Examples 5-8 includes the following steps:

[0057] (1) Li2CO3, ZnO, MnCO3, NiO, CuO and Fe2O3 were mixed in proportion as shown in Table 3, ball milled at 300 rpm for 3 hours, mixed evenly, dried, and finally pre-calcined at 870℃ for 2.5 hours to obtain a pre-calcined material;

[0058] (2) Add 0.15wt% Bi2O3, 0.18wt% CaCO3 and 0.005wt% Co2O3 to the pre-calcined material obtained in step (1), and then ball mill the mixture for 6 hours at a speed of 300 rpm.

[0059] (3) Add 15wt% organic binder PVA to the secondary ball milling material obtained in step (2) to granulate, and press it into a blank (forming pressure is 120MPa, holding pressure for 30s).

[0060] (4) The blank is sintered at 1050℃ for 3 hours to obtain high-power, low-loss LiZn microwave ferrite material.

[0061] The performance test results of the LiZn microwave ferrite materials in Examples 5-8 are shown in Table 4. The electromagnetic performance variation trend is consistent with that in Examples 1-4. SEM images of the LiZn microwave ferrite material prepared in Example 7 are shown below. Figure 2 As shown, the pores in the grains have basically disappeared, and the microstructure is relatively dense.

[0062] Table 4 Performance test results of LiZn microwave ferrite material

[0063]

[0064] Examples 9-12:

[0065] The raw material composition of the high-power, low-loss LiZn microwave ferrite materials in Examples 9-12 is shown in Table 5.

[0066] Table 5 Main raw material components of Examples 9-12

[0067]

[0068] The preparation method of the high-power, low-loss LiZn microwave ferrite material in Examples 9-12 includes the following steps:

[0069] (1) Li2CO3, ZnO, MnCO3, NiO, CuO and Fe2O3 were mixed in proportion as shown in Table 5, ball milled at 300 rpm for 3 hours, mixed evenly, dried, and finally pre-calcined at 920℃ for 3 hours to obtain a pre-calcined material.

[0070] (2) Add 0.3wt% Bi2O3, 0.15wt% CaCO3 and 0.012wt% Co2O3 to the pre-calcined material obtained in step (1), and then ball mill the mixture for 6 hours at 300 rpm.

[0071] (3) Add 15wt% organic binder PVA to the secondary ball milling material obtained in step (2) to granulate, and press it into a blank (forming pressure is 120MPa, holding pressure for 30s).

[0072] (4) The blank is sintered at 1100℃ for 3 hours to obtain high-power, low-loss LiZn microwave ferrite material.

[0073] The performance test results of the LiZn microwave ferrite materials in Examples 9-12 are shown in Table 6. The electromagnetic performance variation trend is consistent with that in Examples 1-4. SEM images of the LiZn microwave ferrite material prepared in Example 12 are shown below. Figure 3 As shown, the grains are fine and uniform, and the microstructure is relatively dense.

[0074] Table 6 Performance test results of LiZn microwave ferrite material

[0075]

[0076] Comparative Examples 1-3:

[0077] Comparative Example 1 is mainly compared with Example 4, Comparative Example 2 is mainly compared with Example 7, and Comparative Example 3 is mainly compared with Example 12. The raw material components of Comparative Examples 1-3 are shown in Table 7.

[0078] Table 7 Main raw material components of Comparative Examples 1-3

[0079]

[0080] The preparation method of the LiZn microwave ferrite materials in Comparative Examples 1-3 includes the following steps:

[0081] (1) Mix Li2CO3, ZnO, MnCO3 and Fe2O3 according to the proportions in Table 7, ball mill at 300 rpm for 3 hours, mix evenly, dry, and finally pre-calcine as required in Table 8 to obtain a pre-calcined material.

[0082] Table 8 Pre-firing conditions for Comparative Examples 1-3

[0083]

[0084] (2) The dopants shown in Table 9 are used to prepare the pre-burned material obtained in step (1), and then the mixture is ball-milled for 6 hours at a mixing speed of 300 rpm.

[0085] Table 9 Comparative Examples 1-3 Dopant Content

[0086]

[0087] (3) Add 15wt% organic binder PVA to the secondary ball milling material obtained in step (2) to granulate, and press it into a blank (forming pressure is 120MPa, holding pressure for 30s).

[0088] (4) The blanks were sintered according to the conditions in Table 10 to obtain LiZn microwave ferrite material.

[0089] Table 10 Sintering conditions of Comparative Examples 1-3

[0090]

[0091] The performance test results of the LiZn microwave ferrite materials in Comparative Examples 1-3 are shown in Table 11. The test data show that introducing NiO and CuO into LiZn ferrite can significantly reduce the ferromagnetic resonance linewidth and simultaneously increase the spin wave linewidth.

[0092] Table 11 Performance test results of LiZn microwave ferrite material

[0093]

[0094] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A high-power, low-loss LiZn microwave ferrite material, characterized in that, The spin waveline width of the high-power, low-loss LiZn microwave ferrite material H k > 17Oe; The raw materials include main materials and dopants. The main materials include Li2CO3, ZnO, MnCO3, CuO, NiO, and Fe2O3; the dopants include Bi2O3, CaCO3, and Co2O3. In molar percentage, the main materials include 8.7~14.1 mol% Li2CO3, 3.4~15.1 mol% ZnO, 2.8~3.6 mol% MnCO3, 0.3~1.2 mol% CuO, 1.8~10.4 mol% NiO, and 65.3~75.5 mol% Fe2O3; the dopants include 0.05~0.30 wt% Bi2O3, 0.05~0.25 wt% CaCO3, and 0.0025~0.01 wt% Co2O3, accounting for 0.05~0.30 wt% of the main materials.

2. The high-power, low-loss LiZn microwave ferrite material as described in claim 1, characterized in that, Its raw materials also include an organic binder, wherein the organic binder is PVA, and the amount added is 10-20% of the total mass of the main material and dopants.

3. A method for preparing a high-power, low-loss LiZn microwave ferrite material as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) The main material is ball-milled and pre-fired once to obtain pre-fired powder; (2) Add a dopant to the pre-calcined powder and perform secondary ball milling; (3) Add organic binder to the secondary ball milling material after step (2) for granulation and press it into blanks; (4) The blank is sintered to obtain the high-power, low-loss LiZn microwave ferrite material.

4. The preparation method according to claim 3, characterized in that, In step (1), the ball mill speed is 200~400 rpm and the ball milling time is 3~6h.

5. The preparation method according to claim 3, characterized in that, In step (1), the pre-firing temperature is 830~920℃ and the pre-firing time is 2~4h.

6. The preparation method according to claim 3, characterized in that, In step (2), the rotation speed of the secondary ball mill is 200~400 rpm and the time is 4~8h.

7. The preparation method according to claim 3, characterized in that, In step (3), the molding pressure is 80~150MPa and the holding pressure is 20~50s.

8. The preparation method according to claim 3, characterized in that, In step (4), the sintering temperature is 1000~1120℃ and the sintering holding time is 2~6h.

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