Gadolinium and magnesium co-substituted BaW ferrite and a preparation method thereof

Abstract

The application discloses a BaW ferrite based on gadolinium and magnesium co-substitution and a preparation method thereof, and belongs to the technical field of ferrite materials. 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 , and Bi2O3 accounting for xwt% of the mass of the pre-fired sample is added, wherein 1<=x<=5. The preparation adopts a solid phase reaction method, and experimental steps include batching, primary ball milling, drying, sieving, pre-firing, adding a sintering aid Bi2O3, secondary ball milling, orientation and sintering. The ferrite material prepared by adding the appropriate amount of sintering aid Bi2O3 has higher residual magnetism ratio and smaller line width than the ferrite material without adding the sintering aid. By adding the sintering aid, the BaW ferrite material with excellent magnetic properties and low line width is successfully prepared. The actual residual magnetism ratio of the material reaches 0.82, and the ferromagnetic resonance line width is reduced to 912 Oe.

Description

Technical Field

[0001] This invention relates to the field of ferrite materials technology, and in particular to a BaW ferrite based on gadolinium and magnesium co-substitution and its preparation method. Background Technology

[0002] In recent years, with the rapid development of communication equipment and radar, the miniaturization and planarization of electronic devices have become an irreversible trend. Traditional spinel and garnet ferrite circulators require an external permanent magnet to provide a bias field to achieve the circulator's function. However, the added external permanent magnet occupies 80% of the entire circulator volume, which is detrimental to planarization and miniaturization. Furthermore, epoxy resin is needed to prevent the permanent magnet from falling off during operation, and the volume of the added permanent magnet increases accordingly with the increase of operating frequency.

[0003] Hexagonal ferrite rings, after orientation processing, exhibit a higher remanence ratio compared to traditional spinel and garnet ferrite rings. Their gyromagnetic properties under high remanence can be used to provide a bias field, eliminating the need for external permanent magnets and greatly facilitating planarization of equipment. However, hexagonal ferrite rings increase insertion loss, and their high anisotropy field is unfavorable for operation in the low-frequency range, leading to frequency congestion. Much research on self-biasing materials focuses on M-type hexagonal ferrites. However, research on W-type hexagonal ferrites, which have a similar structure to the M-type, is limited. W-type ferromagnetism possesses higher saturation magnetization and a higher magnetocrystalline anisotropy, which could better broaden the application range of self-biasing materials. Currently, the ferromagnetic linewidth of commercially available W-type ferromagnetic rings is greater than 2000 Oe, resulting in relatively high insertion loss for self-biased rings. Therefore, improving the gyromagnetic properties of W-type hexagonal ferrites has become a crucial issue that urgently needs to be addressed. Summary of the Invention

[0004] One of the objectives of this invention is to provide a BaW ferrite based on the co-substitution of gadolinium and magnesium to solve the above-mentioned problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a BaW ferrite based on gadolinium and magnesium co-substitution, wherein the molecular formula of the material is: Ba 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 During preparation, x wt% Bi2O3 is added, where 1 ≤ x ≤ 5.

[0006] As the preferred technical solution, x = 3.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned BaW ferrite based on gadolinium and magnesium co-substitution, the technical solution of which includes the following steps: S1. Ingredients: BaCO3, ZnO, Fe2O3, Gd2O3, and MgO are selected as raw materials, according to the molecular formula Ba 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 Perform calculations and accurately weigh the ingredients; S2. First ball milling: Mix the raw material weighed in step S1 with deionized water and perform a first ball milling. After the ball milling is completed, a first ball milling slurry is obtained. S3. Pre-calcination: After drying and sieving the ball mill slurry obtained in step S2, place it in a high-temperature box furnace, heat it up and keep it at a temperature in air atmosphere, and cool it down to room temperature with the furnace to obtain pre-calcined powder. S4. Add sintering aid: Weigh the pre-sintered powder obtained in step S3, and add dispersant and Bi2O3 to mix and prepare the mixture. S5. Secondary ball milling: The mixture obtained in step S4 is mixed with deionized water and subjected to secondary ball milling. After the ball milling is completed, a secondary ball milling slurry is obtained. S6. Orientation pressing of green body: The secondary ball milling slurry obtained in step S5 is poured into a mold. While pressing it into a cylindrical green body under pressure, a magnetic field parallel to the pressure is applied to magnetize the single-domain particles and orient them in the direction of the external magnetic field to obtain the green body. S7. Sintering: The green blank obtained in step S6 is placed in a high-temperature box furnace for sintering. The temperature is raised and held in an air atmosphere, and then cooled to room temperature with the furnace.

[0008] As a preferred technical solution: In step S2, the mass of the added deionized water is 150% to 250% of the raw material, and the ball milling is carried out at a speed of 300 r / min for 12 hours.

[0009] As a preferred technical solution: In step S3, the temperature is increased to 1250°C at a rate of 2-5°C / min, and the holding time is 4 hours.

[0010] As a preferred technical solution: in step S4, the amount of dispersant added is 8 wt% of the pre-calcined powder, and the amount of Bi2O3 added is 1 wt% to 5 wt% of the pre-calcined powder.

[0011] As a preferred technical solution: In step S5, the mass of the added deionized water is 150% to 250% of the mixture, and the secondary ball milling is carried out at a speed of 500 r / min for 24 hours.

[0012] As a preferred technical solution: in step S6, the magnetic field strength during pressing is 10 kOe and the molding pressure is 4 MPa.

[0013] As a preferred technical solution: In step S7, the temperature is increased to 900°C at a rate of 2-5°C / min, and the holding time is 2 hours.

[0014] This invention first involves uniformly mixing the main components and substitutes, then ball milling them once, drying them, and then pre-firing them in a box furnace at a suitable temperature of 1250℃ for 4 hours. Next, the material is weighed and 8wt% of dispersant and 1wt% to 5wt% of sintering aid Bi2O3 are added, followed by a second ball milling. The resulting slurry is poured into a mold and pressed into a cylindrical green body while a magnetic field parallel to the pressure is applied. Finally, a suitable sintering temperature of 900℃ is selected, and the holding time is 2 hours to prepare BaW hexagonal ferrite with high remanence and low ferromagnetic resonance linewidth.

[0015] Compared with the prior art, the advantages of this invention are as follows: This invention solves the problems of low remanence and large ferromagnetic resonance lines in the prior art by adding an appropriate amount of Bi2O3 as a sintering aid on the basis of appropriate Gd and Mg ion substitution; firstly, the main material and the substituted material are mixed and ball-milled once, then dried and pre-fired at a suitable pre-fired temperature, then the pre-fired material is weighed and mixed with the sintering aid and dispersant, and ball-milled a second time after pre-fired. After ball milling, the slurry is poured into a mold for orientation and pressed into a cylindrical shape, and finally sintered at a suitable temperature, successfully preparing Ba with excellent ferromagnetic properties and high remanence. 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 Ferrite materials can achieve a remanence ratio of up to 0.82 and a ΔH as low as 912 Oe. Attached Figure Description

[0016] Figure 1 The XRD patterns are of the ferrite materials prepared in Examples 1-5 of this invention. Figure 2 The following are the remanence ratio trends of the ferrites prepared in Examples 1-5 of this invention; Figure 3 SEM images of the ferrite materials prepared in Comparative Example 1 and Examples 1-5; Figure 4 The image shows the ferromagnetic resonance linewidth fitting diagram of the ferrite material obtained in Example 3 and Comparative Example 1 of the present invention. Detailed Implementation

[0017] To explain the technical content, objectives, and effects of the present invention in detail, the following specific embodiments are provided to further illustrate the content of the present invention. However, the content of the present invention is far more than the following examples.

[0018] A method for preparing BaW ferrite materials based on gadolinium and magnesium co-substitution and Bi2O3 liquid-phase sintering with added Bi2O3 sintering aid includes the following steps: S1. Ingredients: According to Ba 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 The molecular formulas are as follows: BaCO3 (purity: 99wt%), ZnO (purity: 99wt%), Fe2O3 (purity: 99wt%), Gd2O3 (purity: 99.9wt%), MgO (purity: 99.9wt%). S2. First ball milling: The raw material weighed in step S1 is ball milled once for 12 hours; S3. Pre-calcination: After taking the material, dry it in an oven at 100℃. After drying, sieve it through a 45-mesh sieve. Put the sieved powder into a sintering furnace, heat it to 1250℃ at a rate of 2-5℃ / min and keep it at that temperature for 4 hours. Then let it cool naturally to room temperature to obtain the pre-calcined material. S4. Secondary batching: The powder obtained in step S3 is used as the main material, along with 8 wt% of dispersant (sodium methylene bis(naphthalene) sulfonate) and 1 wt% of sintering aid Bi2O3, accounting for 1.1314 g of the pre-fired powder. S5. Secondary ball milling: Using the batching obtained in step S4 as a reference, a secondary ball milling is performed for 24 hours at a speed of 500 r / min. After the ball milling is completed, the secondary ball milling material is obtained. S6. Orientation molding: The secondary ball milling slurry obtained in step S5 is pressed into cylindrical samples under an electric field strength of 10 Oe and a pressure of 4 MPa. S7. Sintering: The sample obtained in step S6 is sintered. First, it is sintered at 900℃ for 2 hours. After cooling to room temperature in the furnace, the BaW ferrite material based on gadolinium and magnesium co-substitution and Bi2O3 liquid phase sintering is obtained.

[0019] Example 2 A BaW ferrite material based on gadolinium and magnesium co-substitution and Bi2O3 liquid-phase sintering and its preparation method are basically the same as those in Example 1, except that in step S4, x=2 is weighed and 2.3792g of Bi2O3 is weighed.

[0020] Example 3 A BaW ferrite material based on gadolinium and magnesium co-substitution and Bi2O3 liquid-phase sintering and its preparation method are basically the same as those in Example 1, except that in step S4, x=3 is weighed and 3.6693g of Bi2O3 is weighed.

[0021] Example 4 A BaW ferrite material based on gadolinium and magnesium co-substitution and Bi2O3 liquid-phase sintering and its preparation method are basically the same as those in Example 1, except that in step S4, x=4 is weighed and 4.8000g of Bi2O3 is weighed.

[0022] Example 5 A BaW ferrite material based on gadolinium and magnesium co-substitution and Bi2O3 liquid-phase sintering and its preparation method are basically the same as those in Example 1, except that in step S4, the weighing value is x=5, and the mass of Bi2O3 is 5.9000g.

[0023] Comparative Example 1 This comparative example is basically the same as Example 1, except that in step S4, x=0 is weighed, that is, Bi2O3 is not added.

[0024] The performance test data is shown in Table 1.

[0025] Table 1. Remanence ratio and saturation magnetization Ms of materials prepared in different embodiments and comparative examples. Table 1 Comparison of magnetic properties of different embodiments and comparative examples project <![CDATA[M r / M s ]]> <![CDATA[M s (emu / g)]]> Comparative Example 1 79% 62.87 Example 1 82% 61.91 Example 2 79% 62.90 Example 3 82% 62.24 Example 4 57% 59.70 Example 5 36% 63.44 The characterization of the BaW ferrite materials prepared in Examples 1, 2, 3, 4, and 5, and the XRD results are as follows: Figure 1 As shown. From Figure 1 It can be seen that when x≤1, the second phase α-Fe2O3 is observed in the sample; when x>1, the W phase is observed. The presence of the second phase α-Fe2O3 when the addition of the sintering aid Bi2O3 is less than 1wt% may be because the sintering temperature decreases to 900℃ with the addition of the sintering aid. The lower sintering temperature and lower sintering aid concentration lead to insufficient reaction of the reactants. Therefore, if the addition of the sintering aid is too low, impurity phases will appear in the sample.

[0026] Ba prepared in Examples 1-5 of this invention 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 The trend of remanence ratio of ferrite is shown in the figure. Figure 2 As shown, from Figure 2 As can be seen, when the amount of Bi2O3 sintering aid added is greater than 3%, the remanence ratio decreases significantly.

[0027] SEM images of the ferrite materials prepared in Comparative Example 1 and Examples 1-5 are shown below. Figure 3 As shown, Figure 3 In the image, (a) is the SEM image of Comparative Example 1, and (b)-(f) are the Ba images prepared in Examples 1-5 of this invention. 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 SEM images of ferrite, from Figure 3 As can be seen, after the addition of the sintering aid, it melts into a liquid at low temperature to form channels, making the grain boundaries more obvious. As the channels are formed, the grain size also becomes smaller.

[0028] The ferromagnetic resonance linewidth values ​​of the ferrite materials obtained in Example 3 and Comparative Example 1 of this invention are as follows: Figure 4 As shown, Figure 4 In the diagram, (a) is the linewidth fitting graph of Comparative Example 1, and (b)-(d) are the Ba samples prepared in Example 3 of this invention. 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 Linewidth fitting plot of ferrite at frequencies of 45-55 GHz. From Figure 4 As can be seen from the results, Example 3 exhibits the lowest ferromagnetic resonance linewidth, with ΔH of 912 Oe. The experimental results demonstrate that the reduced ferromagnetic resonance linewidth ΔH meets the process requirements.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A BaW ferrite based on gadolinium and magnesium co-substitution, characterized in that, The molecular formula of the material is: Ba 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 During preparation, x wt% Bi2O3 is added, where 1 ≤ x ≤ 5.

2. The BaW ferrite based on gadolinium and magnesium co-substitution according to claim 1, characterized in that, x＝3。 3. The method for preparing BaW ferrite based on gadolinium and magnesium co-substitution as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Ingredients: BaCO3, ZnO, Fe2O3, Gd2O3, and MgO are selected as raw materials, according to the molecular formula Ba 0.9 Gd 0.1 Zn2Fe 15.9 Mg 0.1 O 27 Perform calculations and accurately weigh the ingredients; S2. First ball milling: Mix the raw material weighed in step S1 with deionized water and perform a first ball milling. After the ball milling is completed, a first ball milling slurry is obtained. S3. Pre-calcination: After drying and sieving the ball mill slurry obtained in step S2, place it in a high-temperature box furnace, heat it up and keep it at a temperature in air atmosphere, and cool it down to room temperature with the furnace to obtain pre-calcined powder. S4. Add sintering aid: Weigh the pre-sintered powder obtained in step S3, and add dispersant and Bi2O3 to mix and prepare the mixture. S5. Secondary ball milling: The mixture obtained in step S4 is mixed with deionized water and subjected to secondary ball milling. After the ball milling is completed, a secondary ball milling slurry is obtained. S6. Orientation pressing of green body: The secondary ball milling slurry obtained in step S5 is poured into a mold. While pressing it into a cylindrical green body under pressure, a magnetic field parallel to the pressure is applied to magnetize the single-domain particles and orient them in the direction of the external magnetic field to obtain the green body. S7. Sintering: The green blank obtained in step S6 is placed in a high-temperature box furnace for sintering. The temperature is raised and held in an air atmosphere, and then cooled to room temperature with the furnace.

4. The preparation method according to claim 3, characterized in that: In step S2, the mass of deionized water added is 150% to 250% of the raw material, and the ball milling is carried out at a speed of 300 r / min for 12 hours.

5. The preparation method according to claim 3, characterized in that: In step S3, the temperature is increased to 1250°C at a rate of 2-5°C / min, and the holding time is 4 hours.

6. The preparation method according to claim 3, characterized in that: In step S4, the amount of dispersant added is 8wt% to 10% of the pre-calcined powder, and the amount of Bi2O3 added is 1wt% to 5wt% of the pre-calcined powder.

7. The preparation method according to claim 3, characterized in that: In step S5, the mass of the added deionized water is 150% to 250% of the mixture, and the secondary ball milling is carried out at a speed of 500 r / min for 24 hours.

8. The preparation method according to claim 3, characterized in that: In step S6, the magnetic field strength during pressing is 10 kOe, and the molding pressure is 4 MPa.

9. The preparation method according to claim 3, characterized in that: In step S7, the temperature is increased to 900°C at a rate of 2-5°C / min, and the holding time is 2 hours.

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