A Strontium Ferrite Microwave Absorbing Material, Its Preparation Method and Application

Abstract

This invention relates to a strontium ferrite microwave absorbing material, its preparation method, and its application, belonging to the technical field of electromagnetic wave absorbing materials. The chemical formula of the strontium ferrite microwave absorbing material of this invention is: Sr a Ba b Fe z Pr x Ce y O 19 The strontium ferrite material is prepared by mixing raw materials and dissolving them in water, adding citric acid to form a solution; adjusting the pH, heating and stirring to form a wet gel; drying, self-propagating combustion to obtain precursor powder; calcining at a higher temperature, and cooling in the furnace to obtain the strontium ferrite material. The strontium ferrite absorbing material of this invention can cover low, medium, and high frequency bands, has a wide absorption bandwidth, thin absorption thickness, and high coercivity and saturation magnetization, meeting the current electronic product requirements for absorbing materials that are "thin, light, wide, and strong," and has high application value.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorbing materials, and in particular to a strontium ferrite absorbing material, its preparation method, and its application. Background Technology

[0002] With the rapid development of high technology, the original absorbing materials can no longer meet the current development needs. The development and demand for new multifunctional absorbing materials that are lightweight, thin, have a wide absorption bandwidth, and strong absorption capacity are becoming increasingly urgent.

[0003] M-type magnetic lead type strontium ferrite (SrFe) 12 O 19 SFO (Saturated Magnetization-Fluoride) is a magnetic material with excellent chemical stability, which limits its practical application. It is also one of the few microwave absorbing materials that simultaneously possesses magnetic and dielectric losses, indicating significant absorption potential. Furthermore, it has attracted widespread attention due to its relatively low price, high saturation magnetization (MS), high coercivity, high resistivity, corrosion resistance, and excellent chemical stability. However, as a single microwave absorber, it also suffers from drawbacks such as high density and low dielectric loss, which restrict its practical application.

[0004] Improving the microwave absorption performance of M-type ferrites by doping with rare earth ions is a research hotspot. Araz synthesized Ce using ceramic technology. 3+ Substituted hexaferrite Ba 1-x Ce X Fe 12 O 19 (x = 0.25, 0.5, 0.75) ferrite samples. The results show that, through Ba... 2+ Ce-1 substitution 3+ Ions can enhance the magnetic properties of materials, significantly improving Ce. 3+ Microwave absorption properties of praseodymium-doped barium ferrites were investigated. Karamveer Chahal et al. studied the magnetic dielectric behavior of praseodymium-doped barium ferrites, showing that variations in grain size and grain boundaries under different heat treatments led to a decrease in the electrical constant and dielectric tangent loss of the praseodymium-doped barium ferrites with increasing calcination temperature. However, the absorption intensity and bandwidth of these ferrites still need improvement.

[0005] Therefore, in order to meet the current electronic equipment's demand for "thin, light, wide, and strong" characteristics of absorbing materials, it is necessary to develop a new strontium ferrite material, improve its chemical composition and optimize its preparation process, optimize its absorption performance, broaden its absorption bandwidth, and reduce its absorption thickness, which has great application value in electromagnetic microwave absorption. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a strontium ferrite absorbing material, its preparation method, and its applications. The strontium ferrite absorbing material of this invention is co-doped with Pr, Ce, and Ba elements. Within a specific composition ratio range, Pr and Ce can exert a synergistic effect, broadening the bandwidth of the absorbing material and reducing its thickness. Simultaneously, it possesses high coercivity and high saturation magnetization, meeting the requirements of electronic devices for absorbing materials with the characteristics of "thin, light, wide bandwidth, and strong," and has broad application prospects.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a strontium ferrite microwave absorbing material, the chemical formula of which is: Sr a Ba b Fe z Pr x Ce y O 19 Where 0.5≤a≤1.0, 0≤b≤0.5, 10.4≤z≤11.8, 0.1≤x≤0.8, and 0.1≤y≤0.8. The composition of the strontium ferrite microwave absorbing material of the present invention conforms to the molar ratio of each element in the chemical formula.

[0009] Microwave absorber M-type strontium ferrite SrFe 12 O 19 Based on this, Ba, Pr, and Ce are doped into the strontium ferrite lattice to exert a synergistic effect, thereby changing the dielectric loss, regulating the absorption frequency band and broadening the total absorption bandwidth, significantly improving the microwave absorption performance of the material, and reducing the cost. Adjusting the doping amount of Ba, Pr, and Ce can change the saturation magnetization and coercivity, regulate its static magnetic properties, and give the material more possibilities.

[0010] Pr materials are relatively expensive, while Ce materials are cheaper and have abundant reserves in my country. However, strontium ferrite materials doped with Ce alone have no microwave absorption effect. Only at specific Pr-Ce doping levels can they exhibit a synergistic effect, enhancing the microwave absorption and magnetic properties of the ferrite. Ce doping can cause strontium ferrite lattice expansion, increasing the lattice constant and physical activity; due to the variable valence characteristics of Pr and Ce (+3 to +4), co-doping is beneficial for increasing oxygen vacancies and Fe. 2+ The generation of these particles enables simultaneous absorption across low, medium, and high frequency bands, broadening the absorption bandwidth, significantly improving the dielectric properties of the material, and enhancing the absorption intensity across all wavebands. Furthermore, it generates a certain amount of heterogeneous CeO2 particles, which are compressed around the M-phase. The interfacial polarization between the M-phase and the heterogeneous phase increases dielectric loss, which is also beneficial to the absorption effect.

[0011] This strontium ferrite microwave absorbing material also incorporates Ba. Since Ba and Sr have similar radii, Ba can replace some of the Sr sites and dope into the crystal lattice, reducing the material's magnetocrystalline anisotropy and broadening the high-frequency absorption bandwidth to 4 GHz, with a corresponding absorption thickness as low as 2 mm. This improves high-frequency magnetic loss and enhances the material's high-frequency absorption effect.

[0012] The strontium ferrite absorbing material provided by this invention is a spherical polyhedron with a uniform particle size distribution of 50-800 nm. It has high coercivity and saturation magnetization, as well as good absorption performance. It broadens the bandwidth of the absorbing material and reduces the thickness of the absorbing material, which meets the requirements of electronic devices for absorbing materials with the characteristics of "thin, light, wide bandwidth and strong". It has broad application prospects.

[0013] Preferably, in the chemical formula of the strontium ferrite absorbing material, x = y. In this case, the doping ratios of Pr and Ce in the strontium ferrite absorbing material are the same, resulting in a thinner sample absorption thickness and improved absorption performance. At this ratio, Fe... 3+ Better conversion to Fe 2+ To maintain the electroneutrality of strontium ferrite; with Fe 2+ As the amount of ions increases, Fe appears. 3+ and Fe 2+ Exchange coupling between ions contributes a new loss factor, increasing dielectric loss. Furthermore, iron deficiency promotes the generation of oxygen vacancies, leading to more vacancy defects and increasing defect polarizability. Different doping levels of Pr and Ce significantly increase the absorption thickness of the material, which is detrimental to its practical application in electronic products.

[0014] More preferably, in the chemical formula of the strontium ferrite absorbing material, 11.5≤z≤11.8, 0.1≤x=y≤0.25. With this Pr-Ce doping ratio, the strongest absorption of the strontium ferrite absorbing material is between -31.61 and -43.51 dB, corresponding to a minimum absorption thickness of 2-2.5 mm. It exhibits good absorption strength, thin material thickness, and strong overall absorption performance. Further increasing the Pr-Ce co-doping ratio actually worsens the absorption performance of the strontium ferrite absorbing material.

[0015] More preferably, in the chemical formula of the strontium ferrite absorbing material, z = 11.7, x = y = 0.15. When the content of Fe, Pr, and Ce in the strontium ferrite absorbing material conforms to the molar ratio of this chemical formula, Pr and Ce can exert a synergistic effect, achieving simultaneous absorption at low, medium, and high frequencies with a wide coverage range at a relatively low doping level, broadening the absorption bandwidth to over 4GHz, and reducing the material thickness to 2-2.5mm, thus improving the overall absorption performance. Simultaneously, the saturation magnetization can reach over 70 emu / g, and the coercivity is over 4400 Oe, exhibiting good magnetic properties. The overall effect is significantly better than that of single-element doped strontium ferrite materials with the same doping level. Increasing or decreasing the Pr-Ce doping level actually narrows the coverage range of the material's absorption frequency band and thickens the thinnest absorption layer.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned strontium ferrite microwave absorbing material, comprising the following steps:

[0017] (1) Mix the strontium source, barium source, iron source, praseodymium source, cerium source, complexing agent and solvent to obtain a mixed solution;

[0018] (2) Adjust the pH of the mixed solution obtained in step (1) to 6-8, heat and stir at 80-105℃ to form a wet gel;

[0019] (3) The wet gel obtained in step (2) is dried at 105-120℃ and then subjected to self-propagating combustion to obtain precursor powder;

[0020] (4) The precursor powder from step (3) is heated to 1100-1260℃ and calcined, held for 4-10 hours, and then cooled to room temperature in the furnace to obtain strontium ferrite microwave absorbing material.

[0021] The ratios of the strontium, barium, iron, praseodymium, and cerium sources mentioned above are based on the molar ratios of the metal elements in the chemical formula of the strontium ferrite microwave absorbing material. A complexing agent is added, and the pH is adjusted to 6-8. Under stirring at 80-105℃, the metal ions from the barium, strontium, iron, praseodymium, and cerium sources are thoroughly mixed and reacted with the complexing agent to form a stable gel, allowing each metal ion to be dispersed and arranged within the gel network structure.

[0022] If heating is not performed or the mixing is uneven, the metal ions will not be able to disperse sufficiently, and some particles will easily agglomerate, resulting in poor absorption effect. If the pH is not adjusted, the solution will be acidic, and the metal ions will not be able to arrange themselves tightly, resulting in loose ferrite particles and poor absorption effect.

[0023] First, the precursor is dried and synthesized through self-propagating combustion, which initially converts the metal ions into metal oxides and solid metal salts, improving the conversion rate and product purity while saving energy. The precursor is then calcined at 1100-1260℃ for 4-10 hours to further allow the phases to interact and react at high temperatures and remove impurities. The resulting strontium ferrite microwave absorbing material has a good microwave absorption effect and a uniform and compact structure.

[0024] The above preparation method has low production cost, simple process, low energy consumption, no environmental pollutants, high conversion rate, and the obtained microwave absorbing material has good dispersion, and has the advantages of adjustable absorption frequency band, large absorption intensity, and high operating temperature.

[0025] Preferably, the ratio of the total molar amount of strontium source, barium source, iron source, praseodymium source, and cerium source to the molar amount of complexing agent is 1:1; the complexing agent is citric acid. The strontium source, barium source, iron source, praseodymium source, and cerium source are soluble salts of their respective metal elements. When citric acid is added as a complexing agent to the solution of the metal salt, and its molar amount is equal to the total molar amount of each metal ion, it can undergo sufficient hydrolysis and condensation reactions with the metal ions after heating, and after drying, a uniform, fluffy dry gel is formed, thus preparing strontium ferrite with moderate particle size and good microwave absorption performance.

[0026] Preferably, the self-propagating combustion conditions are: reaction at 200-250℃ for 6-12 minutes. Under these conditions, the dry gel is ignited, and it undergoes a self-propagating combustion reaction within a short time, yielding a fluffy, coral-like brown powder. This powder is then ground into fine, uniform particles to obtain the precursor. The combustion reaction is sustained and completed rapidly using the heat released by the chemical reaction itself, eliminating the need for a high-temperature heat source, saving energy, and offering simple operation. It also removes the complexing agent from the gel, resulting in high conversion rate and fast speed.

[0027] Preferably, the heating rate is 4-6℃ / min. At this heating rate, the growth time of the crystal particles is controlled to obtain nanoscale grains, resulting in a more compact strontium ferrite structure, higher coercivity, higher dielectric loss, and better microwave absorption.

[0028] Preferably, the temperature is raised to 600℃, held for 2 hours, and then raised to the calcination temperature. An intermediate temperature is set: at 600℃, the γ-Fe₂O₃ phase reacts with SrCO₃ / SrO to form spinel-type SrFe₂O₄, which then continues to interact with the γ-Fe₂O₃ phase to form SrFe. 12 O 19 The process releases CO2, and holding at this temperature for 2 hours allows for the complete decomposition of SrCO3, ensuring the stable and uniform growth of the strontium ferrite matrix particles. This allows the dopant elements to enter the crystal lattice and continue reacting during further heating and calcination. The full crystal growth reduces the resistivity between grain boundaries, thereby increasing dielectric loss and resulting in a wider absorption bandwidth and better performance.

[0029] Thirdly, the strontium ferrite absorbing material provided by this invention has the advantages of wide absorbing bandwidth, thin absorbing thickness, high coercivity, and high saturation magnetization, which meets the requirements of electronic devices for absorbing materials with the characteristics of "thin, light, wide, and strong", and has broad application prospects.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] Strontium ferrites are prepared by co-doping with Pr, Ce and Ba elements. This method is low in cost and energy consumption. Within a specific ratio range, Pr-Ce can play a synergistic role, broadening the bandwidth of the absorbing material and reducing its thickness. It has good absorption effect, high coercivity, high saturation magnetization and high operating temperature, which meets the requirements of electronic devices for absorbing materials with the characteristics of "thin, light, wide bandwidth and strong", and has broad application prospects. Attached Figure Description

[0032] Figure 1 Here is a 1μm-scale SEM image of the strontium ferrite absorbing material from Example 1;

[0033] Figure 2 Here is a 500nm SEM image of the strontium ferrite absorbing material from Example 1;

[0034] Figure 3 This is a diagram illustrating the microwave absorption effect of the strontium ferrite absorbing material in Example 1.

[0035] Figure 4 Here is a 1μm-scale SEM image of the strontium ferrite absorbing material from Example 2;

[0036] Figure 5 This is a 500nm SEM image of the strontium ferrite absorbing material from Example 2.

[0037] Figure 6 This is a diagram illustrating the microwave absorption effect of the strontium ferrite absorbing material in Example 2.

[0038] Figure 7 Here is a 1μm-scale SEM image of the strontium ferrite absorbing material from Example 3;

[0039] Figure 8 This is a 500nm SEM image of the strontium ferrite absorbing material from Example 3.

[0040] Figure 9 The image shows the microwave absorption effect of the strontium ferrite absorbing material in Example 3. Detailed Implementation

[0041] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available reagents and materials.

[0042] In the following examples and comparative examples, the testing methods for the microwave absorption performance parameters of strontium ferrite materials are as follows:

[0043] The electromagnetic parameters of the material were measured using a Keysight N5224B vector network analyzer. Special test rings were prepared from powder samples, which were made by uniformly mixing the sample and paraffin in different proportions and then pressing them into tablets. The preparation steps for the test rings were as follows: Strontium ferrite absorbing material was ground in a mortar to obtain the test powder. Paraffin and the test powder were added to an appropriate amount of n-hexane at a mass ratio of 3:7, and ultrasonically dispersed to ensure uniform mixing of the powder and paraffin. After the n-hexane evaporated, a dry sample was obtained, which was then pressed into a test ring using a mold. The test frequency was 2-18 GHz, and the dynamic electromagnetic parameters were measured using the coaxial method. The reflection loss at different thicknesses was calculated.

[0044] In the following examples and comparative examples, the magnetic properties of the strontium ferrite material were tested using a magnetic measurement system of model MPMS3.

[0045] In the following examples and comparative examples, the particle size of the strontium ferrite material was tested by observing the microstructure of the material using a high-resolution field emission scanning electron microscope (model [JSM-IT800]). This instrument is also equipped with an energy dispersive spectroscopy (EDS) analyzer for elemental analysis of the material surface.

[0046] Example 1

[0047] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 .

[0048] The method for preparing the strontium ferrite microwave absorbing material in this embodiment includes the following steps:

[0049] (1) The raw materials strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, cerium nitrate hexahydrate and deionized water were mixed in a molar ratio of 1:11.7:0.15:0.15. Then, an aqueous solution of citric acid monohydrate was added, wherein the molar ratio of citric acid to the total molar ratio of metal salt was 1:1. The mixture was stirred for 4 hours to obtain a mixed solution.

[0050] (2) Add 25% ammonia water dropwise to the mixed solution until the pH value of the mixed solution is 7, and then place it in an oil bath constant temperature bath and stir at 90℃ for 9 hours to obtain a viscous gel.

[0051] (3) The viscous gel was dried in a forced-air drying oven at 105°C for 5 hours and then subjected to self-propagating combustion at 200°C for 12 minutes to obtain powder. The powder was then ground to obtain the precursor.

[0052] (4) The precursor powder was heated to 1100°C at a heating rate of 5°C / min, calcined and held for 4 hours, and then cooled to room temperature in the furnace to obtain strontium ferrite microwave absorbing material.

[0053] Figure 1-2 This is a SEM image of the strontium ferrite microwave absorbing material in this embodiment. As can be seen from the image, the particle size of the absorbing material is 50-200 nm, and it has a polyhedral structure with a dense and uniform arrangement.

[0054] Figure 3 The obtained absorption effect diagram shows that the strontium ferrite absorbing material has strong absorption in both low and high frequency bands, with the strongest absorption reaching -31.61dB and a matching thickness of 5.5mm. At the same time, the absorption bandwidth reaches 4.13GHz. The thinnest absorption is 2.5mm, corresponding to the mid-frequency absorption band. It has good absorption effect in all frequency bands.

[0055] Example 2

[0056] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.8 Pr 0.1 Ce 0.1 O 19 .

[0057] The preparation method of the strontium ferrite microwave absorbing material in Example 2 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.8:0.1:0.1, the self-propagating combustion conditions are 250℃ for 6 min, calcination and holding for 6 h, and the remaining steps are the same as in Example 1.

[0058] Figure 4-5 This is a SEM image of the strontium ferrite microwave absorbing material in this embodiment. As can be seen from the image, the particle size of the absorbing material is 50-200 nm, and it has a polyhedral structure with a dense and uniform arrangement.

[0059] Figure 6The obtained absorption effect diagram shows that the strontium ferrite absorbing material has strong absorption in both low and high frequency bands, with the strongest absorption reaching -43.51dB, a matching thickness of 5.5mm, and an absorption bandwidth of 3.79GHz; the thinnest absorption is 2.5mm, corresponding to the low frequency absorption band, which shows good absorption effect.

[0060] Example 3

[0061] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.5 Pr 0.25 Ce 0.25 O 19 .

[0062] The preparation method of the strontium ferrite microwave absorbing material in Example 3 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.5:0.25:0.25, the self-propagating combustion conditions are 220℃ for 10 min and calcination for 8 h, and the remaining steps are the same as in Example 1.

[0063] Figure 7-8 This is a SEM image of the strontium ferrite microwave absorbing material in this embodiment. As can be seen from the image, the particle size of the absorbing material is 50-200 nm, and it has a polyhedral structure with a dense and uniform arrangement.

[0064] Figure 9 The obtained absorption effect diagram shows that the strontium ferrite absorbing material has strong absorption in both low and high frequency bands, with the strongest absorption reaching -43.95dB, a matching thickness of 5.5mm, and an absorption bandwidth of 3.52GHz; the thinnest absorption is 2.5mm, corresponding to the low frequency absorption band, which has a good absorption effect.

[0065] Example 4

[0066] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11 Pr 0.5 Ce 0.5 O 19 .

[0067] The preparation method of the strontium ferrite microwave absorbing material in Example 4 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11:0.5:0.5; the pH of the sol is adjusted to 6; a wet gel is formed by constant-temperature stirring at 80°C; and the drying temperature is 110°C. All other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0068] Example 5

[0069] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 10.8 Pr 0.6 Ce 0.6 O 19 .

[0070] The preparation method of the strontium ferrite microwave absorbing material in Example 5 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:10.8:0.6:0.6; the pH of the sol is adjusted to 8; a wet gel is formed by constant-temperature stirring at 105°C; and the drying temperature is 120°C. All other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0071] Example 6

[0072] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.5 Pr 0.3 Ce 0.2 O 19 .

[0073] The preparation method of the strontium ferrite microwave absorbing material in Example 6 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.5:0.3:0.2. The material is heated to 1100℃ at a heating rate of 4℃ / min, calcined, and held at that temperature for 10 hours. All other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0074] Example 7

[0075] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.5 Pr 0.4 Ce 0.1 O 19 .

[0076] The preparation method of the strontium ferrite microwave absorbing material in Example 7 differs from that in Example 1 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.5:0.4:0.1. The material is heated to 1260℃ at a heating rate of 6℃ / min, calcined, and held at that temperature for 6 hours. All other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0077] Example 8

[0078] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 .

[0079] The preparation method of the strontium ferrite microwave absorbing material in Example 8 differs from that in Example 1 in that it is calcined at 1200℃, while the remaining steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0080] Example 9

[0081] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.7 Pr 0.15 Ce 0.15 O 19 .

[0082] The preparation method of the strontium ferrite microwave absorbing material in Example 9 differs from that in Example 1 in that the temperature is raised to 600℃ and held for 2 hours, then raised to 1260℃ and held for 10 hours. All other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0083] Example 10

[0084] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.4 Pr 0.3 Ce 0.3 O 19 .

[0085] The preparation method of the strontium ferrite absorbing material in Example 10 differs from that in Example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.4:0.3:0.3. All other steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0086] Example 11

[0087] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11.2 Pr 0.4 Ce 0.4 O 19 .

[0088] The preparation method of the strontium ferrite absorbing material in Example 11 differs from that in Example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:11.2:0.4:0.4. All other steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic properties are shown in Table 2.

[0089] Example 12

[0090] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 11 Pr 0.5 Ce 0.5 O 19 .

[0091] The preparation method of the strontium ferrite microwave absorbing material in Example 12 differs from that in Example 4 in that the temperature is raised to 600℃ and held for 2 hours, then raised to 1260℃ and held for 10 hours. All other steps are the same as in Example 4. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0092] Example 13

[0093] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 10.8 Pr 0.6 Ce 0.6 O 19 .

[0094] The preparation method of the strontium ferrite microwave absorbing material in Example 13 differs from that in Example 5 in that the temperature is raised to 600℃ and held for 2 hours, then further raised to 1260℃ and held for 10 hours; the remaining steps are the same as in Example 5. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0095] Example 14

[0096] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is SrFe 10.4 Pr 0.8 Ce 0.8 O 19 .

[0097] The preparation method of the strontium ferrite absorbing material in Example 14 differs from that in Example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 1:10.4:0.8:0.8. All other steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0098] Example 15

[0099] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is Sr 0.5 Ba 0.5 Fe 11.7 Pr 0.15 Ce 0.15 O 19 .

[0100] The preparation method of the strontium ferrite absorbing material in Example 15 differs from that in Example 9 in that the raw materials also include barium nitrate. The molar ratio of strontium nitrate, barium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 0.5:0.5:11.7:0.15:0.15. The remaining steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0101] Example 16

[0102] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is Sr 0.75 Ba 0.25 Fe 11.7 Pr 0.15 Ce 0.15 O 19 .

[0103] The preparation method of the strontium ferrite absorbing material in Example 16 differs from that in Example 9 in that the raw materials also include barium nitrate. The molar ratio of strontium nitrate, barium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 0.75:0.25:11.7:0.15:0.15. The remaining steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0104] Example 17

[0105] One embodiment of the strontium ferrite microwave absorbing material of the present invention, wherein the strontium ferrite microwave absorbing material described in this embodiment is Sr 0.85 Fe 11.85 Pr 0.15 Ce 0.15 O 19 .

[0106] The preparation method of the strontium ferrite absorbing material in Example 17 differs from that in Example 9 in that the molar ratio of strontium nitrate, ferric nitrate nonahydrate, praseodymium nitrate hexahydrate, and cerium nitrate hexahydrate is 0.85:11.85:0.15:0.15. All other steps are the same as in Example 9. The microwave absorption performance parameters of the strontium ferrite absorbing material in this example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0107] Comparative Example 1

[0108] The preparation method of the strontium ferrite absorbing material in Comparative Example 1 differs from that in Example 1 in that praseodymium nitrate and cerium nitrate hexahydrate were not added; all other steps were the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite absorbing material in this comparative example are shown in Table 1; the particle size and magnetic properties are shown in Table 2.

[0109] Comparative Example 2

[0110] The preparation method of the strontium ferrite absorbing material in Comparative Example 2 differs from that in Example 1 in that praseodymium nitrate was not added; all other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite absorbing material in this comparative example are shown in Table 1; the particle size and magnetic properties are shown in Table 2.

[0111] Comparative Example 3

[0112] The preparation method of the strontium ferrite absorbing material in Comparative Example 3 differs from that in Example 1 in that cerium nitrate hexahydrate was not added; all other steps are the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite absorbing material in this comparative example are shown in Table 1; the particle size and magnetic properties are shown in Table 2.

[0113] Comparative Example 4

[0114] The preparation method of the strontium ferrite microwave absorbing material in Comparative Example 4 differs from that in Example 14 in that, after adjusting the pH, the sample was not heated and stirred at a constant temperature, but instead placed in a drying oven for constant temperature and static setting to carry out a sol-gel reaction, resulting in a viscous gel. The remaining steps were the same as in Example 1. The microwave absorption performance parameters of the strontium ferrite microwave absorbing material in this comparative example are shown in Table 1; the particle size and magnetic property parameters are shown in Table 2.

[0115] The chemical formulas and microwave absorption performance parameters of the strontium ferrite microwave absorbing materials in Examples 1-17 and Comparative Examples 1-4 are shown in Table 1; the particle size and magnetic performance parameters of the strontium ferrite microwave absorbing materials in Examples 1-9 and Comparative Examples 1-3 are shown in Table 2.

[0116] Table 1

[0117]

[0118]

[0119] Table 2

[0120]

[0121] The following points can be drawn from the results in Tables 1 and 2:

[0122] (1) As can be seen from Examples 1-17, the strontium ferrite absorbing material of the present invention has good absorbing performance. It has a certain absorbing effect in low, medium and high frequency bands, wide bandwidth, thin thickness, high coercivity and saturation magnetization, which meets the current requirements for the characteristics of absorbing materials that are "thin, light, wide and strong".

[0123] (2) Comparison of Examples 3, 6 and 7 shows that when the molar ratio of Pr to Ce is 1:1, the thickness of the strontium ferrite absorbing material is significantly reduced, while maintaining a good absorbing intensity, making it more suitable for the actual application of electronic products.

[0124] (3) In the chemical formula of strontium ferrite absorbing material, when 11.5≤z≤11.8 and 0.1≤x=y≤0.25, the Pr-Ce doping with this chemical formula ratio has a wide absorption frequency band, which can reach more than 4GHz, and the absorption frequency band covers the widest range. It has strong absorption in low, medium and high frequencies, and the corresponding material thickness is thin, in the range of 2-2.5mm. The saturation magnetization and coercivity are high, and the overall absorption performance and magnetic properties are superior.

[0125] (4) A comparison of Example 1 and Comparative Examples 1-3 shows that undoped strontium ferrite has a high natural resonant frequency, which has its own limitations and poor absorption effect; Ce-doped strontium ferrite has no absorption effect; Pr-doped strontium ferrite has a weak absorption intensity; when Pr and Ce are co-doped in equal amounts, the absorption intensity is significantly improved, corresponding to a thinner material thickness, and it has a certain absorption effect in low, medium, and high frequency bands, resulting in good overall absorption performance. It can be seen that samples doped with a single element have fewer absorption loss mechanisms, which is unfavorable for oxygen vacancies and Fe. 2+ The formation of certain components results in a thicker absorption thickness and a narrower absorption width, leading to poor absorption performance. However, when z = 11.7 and x = y = 0.15 in the chemical formula, Pr-Ce co-doping can reduce costs, exert a better synergistic effect, significantly improve absorption performance, broaden the absorption coverage frequency band and bandwidth, and reduce material thickness, making it more suitable for practical applications of absorbing materials.

[0126] (5) Comparing Example 9 with Examples 15 and 16, it can be seen that the introduction of Ba is beneficial to reduce the magnetocrystalline anisotropy of the material and broaden the absorption bandwidth of the strontium ferrite absorbing material in the high-frequency band, which can reach 4.05 GHz; at the same time, the thickness of the corresponding material is reduced to as low as 2 mm, which is beneficial to improve the high-frequency magnetic loss.

[0127] (6) As can be seen from the comparison between Example 17 and Example 9, under a specific strontium ferrite matrix ratio environment, the absorption effect is better: Pr-Ce can interact better and dop into the lattice, and some Ce can precipitate CeO2 heterogeneous particles, which are distributed around the M phase and undergo interface polarization, thereby increasing dielectric loss.

[0128] (7) Optimized calcination process in Examples 9-13. Comparison of Examples 12 and 13 with Examples 4 and 5: When other conditions remain unchanged, setting the intermediate temperature to 600℃ and extending the holding time results in sufficient crystal growth, which reduces the resistivity between grain boundaries, increases dielectric loss, significantly enhances the absorption intensity of the material, and also broadens the absorption frequency band.

[0129] (8) As can be seen from the comparison between Example 14 and Comparative Example 4, when the dry gel is obtained by standing without constant temperature stirring, the molecules cannot be fully mixed, which easily causes some particles to agglomerate, resulting in poor microwave absorption effect.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A strontium ferrite microwave absorbing material, characterized in that, The chemical formula of the strontium ferrite microwave absorbing material is: Sr a Ba b Fe z Pr x Ce y O 19 Where 0.5≤a≤1.0, 0≤b≤0.5, 10.4≤z≤11.8, 0.1≤x≤0.8, 0.1≤y≤0.8; x=y; The preparation method of the strontium ferrite microwave absorbing material includes the following steps: (1) Mix the strontium source, barium source, iron source, praseodymium source, cerium source, complexing agent and solvent to obtain a mixed solution; (2) Adjust the pH of the mixed solution obtained in step (1) to 6-8, heat and stir at 80-105℃ to form a wet gel; (3) The wet gel obtained in step (2) is dried at 105-120℃ and then subjected to self-propagating combustion to obtain precursor powder; (4) The precursor powder from step (3) is heated to 1100-1260℃ and calcined, held for 4-10 hours, and then cooled to room temperature in the furnace to obtain the strontium ferrite microwave absorbing material.

2. The strontium ferrite microwave absorbing material according to claim 1, characterized in that, In the chemical formula of the strontium ferrite microwave absorbing material, 11.5≤z≤11.8, 0.1≤x=y≤0.

25.

3. The strontium ferrite microwave absorbing material according to claim 2, characterized in that, In the chemical formula of the strontium ferrite microwave absorbing material, z = 11.7 and x = y = 0.

15.

4. The method for preparing the strontium ferrite microwave absorbing material according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Mix the strontium source, barium source, iron source, praseodymium source, cerium source, complexing agent and solvent to obtain a mixed solution; (2) Adjust the pH of the mixed solution obtained in step (1) to 6-8, heat and stir at 80-105℃ to form a wet gel; (3) The wet gel obtained in step (2) is dried at 105-120℃ and then subjected to self-propagating combustion to obtain precursor powder; (4) The precursor powder from step (3) is heated to 1100-1260℃ and calcined, held for 4-10 hours, and then cooled to room temperature in the furnace to obtain the strontium ferrite microwave absorbing material.

5. The method for preparing the strontium ferrite microwave absorbing material according to claim 4, characterized in that, In step (1), the ratio of the total molar amount of the strontium source, barium source, iron source, praseodymium source, and cerium source to the molar amount of the complexing agent is 1:

1.

6. The method for preparing the strontium ferrite microwave absorbing material according to claim 4 or 5, characterized in that, The complexing agent is citric acid.

7. The method for preparing the strontium ferrite microwave absorbing material according to claim 4, characterized in that, In step (3), the conditions for self-propagating combustion are: reaction at 200-250℃ for 6-12 minutes.

8. The method for preparing the strontium ferrite microwave absorbing material according to claim 4, characterized in that, In step (4), the heating rate is 4-6℃ / min.

9. The method for preparing the strontium ferrite microwave absorbing material according to claim 4, characterized in that, In step (4), the temperature is raised to 600℃ and held for 2 hours, and then raised to the calcination temperature.

10. The application of the strontium ferrite absorbing material according to claim 1 in electromagnetic microwave absorption of electronic devices.

Images