W-type barium cobalt ferrite / cobalt-iron alloy material based on desolventization method, preparation and application thereof

Abstract

The application relates to a W-type barium cobalt ferrite / cobalt-iron alloy material based on a desolventizing method and preparation and application thereof, the preparation method comprises the following steps: (1) uniformly mixing a barium source, a cobalt source, an iron source, a zinc source and polyvinylpyrrolidone, and freeze-drying to obtain a precursor powder; (2) sintering the precursor powder to obtain a W-type barium zinc cobalt ferrite with a main phase of BaZn 2– x Co x Fe 16 O 27 ; (3) carrying out controllable reduction desolventizing of the W-type barium zinc cobalt ferrite under a hydrogen-argon atmosphere to obtain a W-type barium zinc cobalt ferrite / cobalt-iron alloy (BaZn 2–x Co x Fe 16 O 27 / CoFe) material, namely a target product. The application synthesizes materials with different intrinsic resonance peak values into a composite system, thereby obtaining a composite wave-absorbing material with strong resonance wave-absorbing characteristics in a low-frequency microwave (2-8 GHz) wave band, the overall preparation process is simple, industrial application is good, and the application can be widely applied to corresponding electromagnetic absorption and microwave stealth fields.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a W-type barium cobalt ferrite / cobalt iron alloy material based on the desolvation method, its preparation and application. Background Technology

[0002] With the rapid development of industries such as metaverse, blockchain, human-computer interaction, and 5G communication, people's lives are surrounded by big data, bringing great convenience. However, at the same time, the electromagnetic pollution caused by the massive data transmission in civilian industries has also caused serious harm to human health and the environment, making the research and development of electromagnetic absorbing materials a priority. Civilian electromagnetic signal transmission is mainly concentrated in the low-frequency microwave band of 2–8 GHz. Generally, impedance matching determines the degree to which electromagnetic waves enter the absorbing material, and attenuation capability determines the ability of the absorbing material to convert electromagnetic energy into other forms of energy after the electromagnetic waves enter. In the low-frequency band, the absorption capability of ordinary electromagnetic wave absorbing materials is insufficient to meet functional requirements because their impedance matching and attenuation capabilities are often inversely coupled. To solve this problem, magnetic materials are one of the most promising candidates for low-frequency absorbing materials because their high permeability can break this inverse coupling and maintain good low-frequency absorption performance. Currently, the most representative and best-performing magnetic absorbing materials are ferrites and magnetic metals / alloys. Ferrites can be divided into spinel-type ferrites, garnet-type ferrites, and magnetoplumbine-type ferrites. Hexagonal magnetoplumbleite ferrites belong to the hexagonal crystal system and include M, X, Y, U, Z, and W-type ferrites. W-type hexagonal ferrites exhibit high response in the GHz band. Due to their high saturation magnetic susceptibility, high coercivity, and good chemical stability, they are not only suitable for electromagnetic wave absorption but also widely used in magnetic recording and electronic components. However, due to the complexity of the W-type hexagonal ferrite structure, its response capability in the low-frequency microwave band has not been fully developed, and mature low-frequency microwave absorbing materials based on W-type hexagonal ferrites are currently scarce. Some magnetic metals / alloys, such as Co, Fe, and CoFe alloys, have high response performance at low frequencies, but due to the eddy current effect and the Snooker limit, low-frequency microwave absorbing materials with high absorption rates and wide bandwidth have not yet been developed. Summary of the Invention

[0003] The purpose of this invention is to provide a W-type barium cobalt ferrite / cobalt iron alloy material based on the desolventizing method, as well as its preparation and application, to obtain composite microwave absorbing materials with strong resonant microwave absorption characteristics in the low-frequency microwave (2-8GHz) band.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] One of the technical solutions of the present invention provides a method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on a solvent extraction method, comprising the following steps:

[0006] (1) Mix barium source, cobalt source, iron source, zinc source and polyvinylpyrrolidone evenly to obtain a gel sample, and freeze dry to obtain precursor powder;

[0007] (2) The precursor powder was sintered to obtain the main phase as BaZn. 2–x Co x Fe 16 O 27 W-type barium zinc cobalt ferrite, with other impurities being negligible;

[0008] (3) W-type barium zinc cobalt ferrite was subjected to controlled reduction and solvent removal under a hydrogen and argon atmosphere to obtain W-type barium zinc cobalt ferrite / cobalt iron alloy (BaZn). 2–x Co x Fe 16 O 27 The target product is the / CoFe) material.

[0009] Furthermore, in step (1), the amount of barium source, cobalt source, iron source and zinc source added satisfies the following: the molar ratio of barium, cobalt, iron and zinc is 1:x:16:(2-x), where x ranges from 0 to 2.

[0010] Furthermore, the barium source is one or more soluble barium salts; the cobalt source is one or more soluble cobalt salts; the iron source is one or more soluble iron salts; and the zinc source is one or more soluble zinc salts.

[0011] Furthermore, the barium source is barium nitrate, the cobalt source is cobalt nitrate, the iron source is ferric nitrate, and the zinc source is zinc nitrate.

[0012] Furthermore, the freeze-drying process involves first rapidly freezing the material into a solid state in a liquid nitrogen environment, and then...

[0013] Furthermore, the molecular weight of the polyvinylpyrrolidone is 30,000 to 58,000, its concentration in the solution is 0.05 to 0.1 g / mL, and the barium source is calculated as barium nitrate, with a mass ratio of polyvinylpyrrolidone to barium source of 1:0.8-1.2.

[0014] Furthermore, in step (2), the sintering temperature is 1050–1300℃, more preferably 1100–1250℃, and the sintering time is 4–6 h. Specifically, during the first sintering process, the heating rate is 5–10℃ / min.

[0015] Furthermore, the average grain size of the W-type barium cobalt ferrite material is 2–5 μm.

[0016] Furthermore, in step (3), the temperature for controlled reduction and desolvation is 375–475°C, more preferably 425–450°C, and the time is 2–3 hours. Specifically, the heating rate is 5–10°C / min.

[0017] Furthermore, in step (3), the volume fraction of hydrogen in the hydrogen-argon atmosphere is 5%.

[0018] The second technical solution of the present invention provides a W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method, which is prepared by any of the preparation methods described above.

[0019] The third technical solution of the present invention provides the application of W-type barium cobalt ferrite / cobalt iron alloy material based on the desolvation method in the field of microwave absorption.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The synthesis method of this invention is novel. By using a simple temperature-controlled reduction and desolventizing method, W-type barium zinc cobalt ferrite with uniform cobalt-iron alloy desolventized on the surface is successfully synthesized.

[0022] (2) The synthesis method of W-type barium zinc cobalt ferrite / cobalt iron alloy material provided by the present invention has a certain degree of universality. The ratio of zinc to cobalt can be changed in the W-type barium zinc cobalt ferrite, and different desolvation degrees can be adjusted to construct W-type barium zinc cobalt ferrite / cobalt iron alloy with different composition ratios.

[0023] (3) The W-type barium zinc cobalt ferrite / cobalt iron alloy material provided by the invention is applied in the field of low frequency microwave absorption and has the advantages of high absorption rate, thin coating and wide bandwidth.

[0024] (4) Based on the above preparation method, this invention combines materials with different intrinsic resonance peaks into a composite system, thereby obtaining a composite absorbing material with strong resonant absorption characteristics in the low-frequency microwave (2-8 GHz) band. The preparation process of this invention is simple and low-cost. It can effectively adapt and adjust the raw materials and process parameters to obtain a material with a wide absorption frequency band. It also has good industrial applicability, can be mass-produced, and can be widely used in corresponding electromagnetic absorption and microwave stealth fields. Attached Figure Description

[0025] Figure 1a Scanning electron microscope image of W-type barium zinc cobalt ferrite;

[0026] Figure 1b Scanning electron microscope image of W-type barium zinc cobalt ferrite / cobalt iron alloy material;

[0027] Figure 1c Transmission electron microscopy (TEM) images showing the microstructure of W-type barium-zinc-cobalt ferrite / cobalt-iron alloys. Figure 1dHigh-resolution lattice image of the interface;

[0028] Figure 1e This maps elements to the interface.

[0029] Figure 2a For X-ray diffraction (XRD) analysis;

[0030] Figure 2b XPS energy dispersive spectroscopy analysis of BZCFO and BZCFO / CoFe (x = 0.7, 1.0, 1.5).

[0031] Figure 3 The hysteresis loops of BZCFO and BZCFO / CoFe (x = 0.7, 1.0, 1.5) at room temperature are given.

[0032] Figure 4 The microwave absorption performance diagrams are for BZCFO, BZCFO & CoFe mixture, and BZCFO / CoFe (x = 0.7, 1.0, 1.5).

[0033] Figure 5a b and b represent the absorption rates of BZCFO and BZCFO / CoFe in the frequency range of 2–8 GHz, respectively. Figure 5c This is a comparison chart showing the absorption rates of BZCFO and BZCFO / CoFe exceeding 90% in the 2–8 GHz frequency range. Figure 5d The diagram shows a comparison of the effective absorption bandwidth of the BZCFO / CoFe materials prepared in Examples 1, 2, and 3 with other single-phase W-type barium ferrite and metal / alloy materials (mainly selecting the absorption bandwidth of effective thicknesses of 2-4 mm).

[0034] Figure 6a b are scanning electron microscope images of the W-type barium zinc cobalt ferrite material BZCFO prepared in Comparative Examples 2 and 3, respectively.

[0035] Figure 7a b and b are the reflection loss (RL) values ​​of the W-type barium zinc cobalt ferrite materials prepared in Comparative Example 2 and Comparative Example 3 in the frequency range of 2 to 8 GHz, respectively. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0037] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are all conventional commercially available products or conventional processing techniques in the art.

[0038] Example 1

[0039] W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) 1.3 Co 0.7 Fe 16 O 27 Preparation of / CoFe, referred to as BZCFO / CoFe (x=0.7) in this paper:

[0040] (1) Add barium nitrate with a concentration of 0.1 g / mL to 10 ml of water, then add zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and ferric nitrate nonahydrate. The ratio of zinc, cobalt, and iron to barium is 1.3:0.7:16:1. Stir evenly, then add polyvinylpyrrolidone (PVP, Mw of about 55,000) with a concentration of 0.1 g / mL. Stir evenly to obtain a viscous gel. Place the beaker containing the gel into liquid nitrogen and freeze it into a solid state. Place it in a freeze dryer for freeze drying for 72 h.

[0041] (2) The freeze-dried powder prepared in step (1) is sintered in a muffle furnace at 1200℃ for 6 hours to obtain hexagonal W-type barium zinc cobalt ferrite BaZn. 1.5 Co 0.5 Fe 16 O 27 .

[0042] (3) W-type barium zinc cobalt ferrite BaZn 1.5 Co 0.5 Fe 16 O 27 Reduced at 425℃ for 2 hours under an H2 / Ar (5% H2) atmosphere with a heating rate of 2℃ / min, W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) was obtained. 1.3 Co 0.7 Fe 16 O 27 / CoFe).

[0043] Example 2

[0044] W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) 1.0 Co 1.0 Fe 16 O 27 Preparation of / CoFe, referred to as BZCFO / CoFe (x=1.0) in this paper:

[0045] (1) Add barium nitrate with a concentration of 0.1 g / mL to 10 ml of water, then add zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and ferric nitrate nonahydrate. The ratio of zinc, cobalt, and iron to barium is 1.0:1.0:16:1. Stir evenly, then add polyvinylpyrrolidone (PVP, Mw = ~55,000) with a concentration of 0.1 g / mL. Stir evenly to obtain a viscous gel. Place the beaker containing the gel into liquid nitrogen and freeze it into a solid state. Place it in a freeze dryer for freeze drying for 72 h.

[0046] (2) The freeze-dried powder prepared in step (1) is sintered in a muffle furnace at 1200℃ for 6 hours to obtain hexagonal W-type barium zinc cobalt ferrite BaZn. 1.0 Co 1.0 Fe 16 O 27 .

[0047] (3) W-type barium zinc cobalt ferrite BaZn 1.5 Co 0.5 Fe 16 O 27 Reduced at 425℃ for 2 hours under an H2 / Ar (5% H2) atmosphere with a heating rate of 2℃ / min, W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) was obtained. 1.0 Co 1.0 Fe 16 O 27 / CoFe).

[0048] Example 3

[0049] W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) 0.5 Co 1.5 Fe 16 O 27 Preparation of / CoFe (hereinafter referred to as BZCFO / CoFe):

[0050] (1) Add barium nitrate with a concentration of 0.1 g / mL to 10 ml of water, then add zinc nitrate hexahydrate, cobalt nitrate hexahydrate, and ferric nitrate nonahydrate. The ratio of zinc, cobalt, and iron to barium is 0.5:1.5:16:1. Stir evenly, then add polyvinylpyrrolidone (PVP, Mw = ~55,000) with a concentration of 0.1 g / mL. Stir evenly to obtain a viscous gel. Place the beaker containing the gel into liquid nitrogen and freeze it into a solid state. Place it in a freeze dryer for freeze drying for 72 h.

[0051] (2) The freeze-dried powder prepared in step (1) is sintered in a muffle furnace at 1200℃ for 6 hours to obtain hexagonal W-type barium zinc cobalt ferrite BaZn. 1.5 Co 0.5 Fe 16 O 27 .

[0052] (3) W-type barium zinc cobalt ferrite BaZn 1.5 Co 0.5 Fe 16 O 27 Reduced at 425℃ for 2 hours under an H2 / Ar (5% H2) atmosphere with a heating rate of 2℃ / min, W-type barium zinc cobalt ferrite / cobalt iron alloy material (BaZn) was obtained. 0.5 Co 1.5 Fe 16 O 27 / CoFe).

[0053] Comparative Example 1

[0054] Preparation of BZCFO & CoFe mixture materials:

[0055] Compared to Example 1, in the BZCFO & CoFe mixture, CoFe was mixed with BZCFO using a secondary loading method, and the mass ratio of the two was the same as in BZCFO / CoFe (the mass ratio of the components can be calculated by refining the XRD pattern). Preparation of BZCFO (i.e., BaZn) 0.5 Co 1.5 Fe 16 O 27 The method is the same as described above. Then, a certain amount of BZCFO and 2 ml of oleic acid are ultrasonically dissolved in 60 mL of ethylene glycol. 4 g of NaOH, and corresponding proportions of FeCl2·4H2O and CoCl2·6H2O are ultrasonically dissolved in 60 mL of ethylene glycol. The two mixtures are then mechanically stirred and heated in an oil bath to 100°C until the reactants are completely dissolved. The mixture is then heated to 180°C and maintained for 1 hour. The heating reaction requires an inert gas protection system. Finally, the product is washed with alcohol to obtain a BZCFO & CoFe mixture powder.

[0056] Comparative Example 2:

[0057] The two are largely the same as in Example 1, except that the H2 / Ar atmosphere in step (3) is replaced with a pure Ar atmosphere.

[0058] Comparative Example 3:

[0059] The majority of the results are the same as in Example 1, except that the freeze-dried powder in Example 1 is replaced with direct drying.

[0060] The microstructure of the materials in the above embodiments was characterized using scanning electron microscopy (SEM, Hitachi SEM S-4800). Sample preparation method: the powder sample was ultrasonically dispersed in ethanol, then dropped onto a conductive silicon wafer and dried for testing. The microstructure of a series of composite materials was characterized using transmission electron microscopy (TEM, JEOL JEM-2100F). Sample preparation method: the powder sample was ultrasonically dispersed in ethanol, then dropped onto a carbon-supported copper mesh and dried for testing. X-ray diffraction patterns were obtained using a Bruker D8 Advance instrument. The complex relative permittivity and permeability in the 2–8 GHz range were measured using a vector network analyzer (model N5230C).

[0061] Figure 1a This is a scanning electron microscope image of W-type barium zinc cobalt ferrite. Figure 1b Scanning electron microscope (SEM) images of W-type barium zinc cobalt ferrite / cobalt iron alloy materials. Figure 1a and Figure 1b The scale in the text is 1 micrometer. For example... Figure 1a As shown in Figures 1 and 2, after reduction and desolventizing, the W-type barium zinc cobalt ferrite still maintains its original morphology, and obvious cobalt-iron alloy nanoparticles can be seen dotting the surface of the W-type barium zinc cobalt ferrite. Figure 1c Transmission electron microscopy (TEM) images showing the microstructure of W-type barium-zinc-cobalt ferrite / cobalt-iron alloys. Figure 1d This is a high-resolution lattice image of the interface. Figure 1e The element mapping at the interface shows that cobalt and iron are concentrated on the cobalt-iron alloy side, while barium, iron, and oxygen are concentrated on the W-type barium-zinc-cobalt ferrite side.

[0062] Figure 2a X-ray diffraction (XRD) analysis was performed. The figure shows the crystal plane (PDF#19-0098) corresponding to the W-type barium zinc cobalt ferrite component. The cobalt-iron alloy component was not obvious during reduction at 375℃, but crystal planes corresponding to the cobalt-iron alloy component were produced under reduction conditions at 425℃ and 474℃, confirming the compositional integrity of the synthesized structure. Figure 2b XPS energy dispersive spectroscopy analysis of BZCFO and BZCFO / CoFe (x = 0.7, 1.0, 1.5) shows that peaks for oxygen vacancies and lattice oxygen coexist. Comparison of the peak areas of oxygen vacancies and lattice oxygen indicates that the concentration of oxygen vacancies is the highest in BZCFO / CoFe.

[0063] Figure 3 The hysteresis loops of BZCFO and BZCFO / CoFe (x = 0.7, 1.0, 1.5) at room temperature are given.

[0064] Figure 4a and b are the real and imaginary parts (ε' and ε”) of the complex permittivity of BZCFO, BZCFO & CoFe mixture, and BZCFO / CoFe (x = 0.7, 1.0, 1.5). Figure 4 c and d represent the real and imaginary parts (μ' and μ”) of the complex permeability, respectively, used to reveal the mechanism of its excellent microwave absorption performance. The microwave absorption performance of composite materials mainly originates from dielectric loss and magnetic loss. It can be found that BZCFO has the lowest dielectric parameter, and its change with frequency is relatively gradual, indicating its poor dielectric performance. The dielectric parameter of the BZCFO & CoFe mixture shows improvement in both the real and imaginary parts, which is due to the addition of CoFe improving the material's conductivity loss capability, but the improvement is still limited. The BZCFO / CoFe (x = 0.7, 1.0, 1.5) material has a higher real part of dielectric parameter, which decreases with increasing frequency in the range of 2–8 GHz. This is due to the addition of surface-desoluble CoFe nanoparticles improving the material's conductivity loss capability. The polarization loss capability is enhanced by the design of surface-desoluble nanoparticles, which construct multiple interfaces to dissipate electromagnetic waves entering the material. Simultaneously, both the real and imaginary parts of the permeability of the BZCFO / CoFe mixture are improved compared to BZCFO. For BZCFO / CoFe (x = 0.7, 1.0, 1.5) materials, the presence of surface-desoluble CoFe nanoparticles significantly increases the overall magnetic properties compared to BZCFO, thereby increasing magnetic loss. The imaginary part of the permeability exhibits broad peaks of varying degrees between 2 and 8 GHz, possibly due to abundant domain wall resonances and natural resonance phenomena within the material. The highest real permeability value for the BZCFO / CoFe material reaches 2.3, and the highest imaginary permeability value reaches 0.9.

[0065] Figure 5a b and b represent the absorption rates (AR) of BZCFO and BZCFO / CoFe in the frequency range of 2–8 GHz, respectively. It was found that BZCFO achieves an effective absorption efficiency of 92.2% at low frequencies with a thickness of 3.8 mm. At a thickness of 3.8 mm, the electromagnetic wave absorption rate of BZCFO / CoFe can reach 99.7% at 3.5 GHz. Figure 5c This is a comparison chart showing the absorption rates of BZCFO, BZCFO & CoFe, BZCFO / CoFe (x = 1.0), and BZCFO / CoFe in the 2–8 GHz frequency range, exceeding 90%. Figure 5d The diagram shows a comparison of the effective absorption bandwidth of the BZCFO / CoFe material prepared in Examples 1, 2, and 3 with other single-phase W-type barium ferrite and metal / alloy materials (mainly selecting the absorption bandwidth of effective thickness of 2-4 mm). It can be seen that the absorption bandwidth of BZCFO / CoFe is mainly concentrated in the low-frequency microwave band of 2-8 GHz, which can be used as a future civilian 5G electromagnetic wave absorbing material.

[0066] Figure 6a The image shows a scanning electron microscope (SEM) image of the W-type barium zinc cobalt ferrite material BZCFO sintered in Comparative Example 2 after the H2 / Ar atmosphere was changed to a pure Ar atmosphere. The W-type barium zinc cobalt ferrite retains its original morphology, and there are no obvious particles on the surface, indicating that no alloy reduction precipitation occurred.

[0067] Figure 6b The image shows a BZCFO scanning electron microscope image of the W-type barium zinc cobalt ferrite material, which was directly dried and then sintered by reduction and solvent removal, instead of the freeze-dried powder in Comparative Example 3. The W-type barium zinc cobalt ferrite is no longer hexagonal plate-like but rather nanoparticles without a fixed morphology. Furthermore, no obvious particles are present on the surface after reduction and solvent removal, indicating that the alloy precipitation was unsuccessful.

[0068] Figure 7a The reflection loss (RL) of the W-type barium zinc cobalt ferrite material BZCFO after sintering in a pure Ar atmosphere instead of H2 / Ar in Comparative Example 2 is given by the relationship between RL (dB) and absorptivity in the frequency range of 2–8 GHz and the absorptivity as RL (dB) = -10 log (AR).

[0069] Figure 7b The reflection loss (RL) of BZCFO, a W-type barium zinc cobalt ferrite material that was directly dried and then reduced and desolventized and sintered in Comparative Example 3, is measured in the frequency range of 2–8 GHz.

[0070] In summary, the W-type barium zinc cobalt ferrite / cobalt iron alloy material BZCFO / CoFe of this invention exhibits excellent electromagnetic wave loss capability in the low-frequency range (2–8 GHz). This invention employs a solution-reduction method to prepare the W-type barium zinc cobalt ferrite / cobalt iron alloy. By controlling the reduction temperature, the cobalt iron content in the precursor, and the content of the dissolved alloy particles, the dielectric and magnetic properties can be regulated. With a thickness of 3.8 mm, an absorption efficiency of over 99.7% can be achieved in the 2–8 GHz frequency range. Therefore, it has promising application prospects in the field of low-frequency absorption.

[0071] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on a solution-removing method, characterized in that, Includes the following steps: (1) Mix barium source, cobalt source, iron source, zinc source and polyvinylpyrrolidone evenly, and freeze dry to obtain precursor powder; (2) The precursor powder was sintered to obtain the main phase as BaZn. 2–x Co x Fe 16 O 27 W-type barium zinc cobalt ferrite; (3) W-type barium zinc cobalt ferrite is subjected to controlled reduction and solvent removal under a hydrogen and argon atmosphere to obtain W-type barium zinc cobalt ferrite / cobalt iron alloy material, which is the target product; In step (1), the amounts of barium source, cobalt source, iron source and zinc source added satisfy the following: the molar ratio of barium, cobalt, iron and zinc is 1:x:16:(2-x), where x ranges from 0.7 to 1.5; The concentration of polyvinylpyrrolidone in the solution is 0.05~0.1 g / mL, and the barium source is calculated as barium nitrate, with a mass ratio of polyvinylpyrrolidone to barium source of 1:0.8~1.

2. In step (3), the temperature for controlled reduction and desolvation is 375-475℃ and the time is 2-3h.

2. The method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method according to claim 1, characterized in that, The barium source is one or more of soluble barium salts; the cobalt source is one or more of soluble cobalt salts; the iron source is one or more of soluble iron salts; and the zinc source is one or more of soluble zinc salts.

3. The method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method according to claim 2, characterized in that, The barium source is barium nitrate, the cobalt source is cobalt nitrate, the iron source is ferric nitrate, and the zinc source is zinc nitrate.

4. The method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method according to claim 1, characterized in that, In step (2), the sintering temperature is 1050-1300 ℃ and the sintering time is 4-6 h.

5. The method for preparing W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method according to claim 1, characterized in that, In step (3), the volume fraction of hydrogen in the hydrogen-argon atmosphere is 5%.

6. A W-type barium cobalt ferrite / cobalt iron alloy material based on a solvent extraction method, which is prepared by the preparation method described in any one of claims 1-5.

7. The application of the W-type barium cobalt ferrite / cobalt iron alloy material based on the solvent extraction method as described in claim 6 in the field of microwave absorption.

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