Preparation method of ion-doped yttrium iron garnet powder

Abstract

This invention relates to a method for preparing ion-doped yttrium iron garnet powder, belonging to the field of materials preparation. The method specifies a method for preparing ion-doped yttrium iron garnet powder, wherein the chemical composition of the ion-doped yttrium iron garnet powder is Ce. a Bi b Y (3‑a‑b) Fe5O 12 Where a≤0.4, b≤0.4, and a and b are not both 0, the method includes the following process steps: first, synthesizing a polymeric network gel containing Ce, Bi, Y, and Fe ions; then calcining the obtained polymeric network gel to obtain a loose and porous oxide precursor powder; placing the obtained oxide precursor powder in a high-temperature horizontal ball mill for high-temperature controlled-pressure ball milling, and finally obtaining ion-doped yttrium iron garnet powder. The method of the present invention can obtain composite oxide powder with high phase purity, low defect density, and good compactness and grain uniformity.

Description

Technical Field

[0001] This invention relates to a method for preparing ion-doped yttrium iron garnet powder, belonging to the field of materials preparation. Background Technology

[0002] Yttrium iron garnet has a complex cubic structure and its general chemical formula is Y3Fe5O. 12 (YIG), each unit cell contains eight molecular units, and its crystal structure contains three interstitial sites: Y 3+ With a large radius, it occupies the 24c site (oxygen dodecahedral interstitial space), Fe 3+ Occupying 16a sites (oxygen octahedral interstitials) and 24d sites (oxygen tetrahedral interstitials), this multi-lattice structure provides abundant possibilities for ion doping: for example, large ions such as Bi, Ce, Dy, La, and Gd can replace c-site Y ions to improve saturation magnetization, magneto-optical Faraday effect, Curie temperature, and resistivity; while Ni and Ga ions can replace a-site or d-site Fe ions to regulate magnetic dilution and optical absorption. The key properties of YIG and its Ce, Bi, Gd, and Ga dopants are jointly determined by crystal chemistry and defect chemistry. The valence state of Fe determines the basic magneto-optical properties, while the valence state and site occupancy of Ce and Bi directly determine the effect of doping modification, as well as phase purity and density. By locking the trivalent state of variable-valence elements, the phase-stable region can be effectively defined, and the defect concentration can be controlled, thereby solidifying the material's performance indicators.

[0003] Existing technologies for the preparation of YIG powder have undergone a series of evolutions. To shorten the process and reduce costs, chemical preparation processes have become a research hotspot. For example, in Chinese patent CN117602674A published in 2024, Liu Guixiang et al. introduced a method for obtaining nano-YIG powder using nitrates, citric acid, and glycine as raw materials through sintering via sol-gel and fuel combustion methods. While these existing technologies have achieved process shortening and cost control to some extent, with the industry's continuously increasing requirements for the performance of magneto-optical ceramics, existing preparation technologies still face insurmountable thermodynamic and kinetic obstacles when dealing with complex multi-component ion doping.

[0004] To lower the synthesis temperature, Jiang Linwen disclosed a method for preparing YIG powder using citric acid as a complexing agent in his master's thesis, "Preparation of YIG Powder by Self-Propagating Combustion and Its Performance Study" (2006). Although this method attempts to improve uniformity through a wet precursor pathway, its essence still relies on the chemical complexation equilibrium between metal ions and citric acid. In multi-component systems such as Bi, Ce, Fe, and Y, the complexation constants of each ion differ greatly, making micro-segregation very likely to occur during gel drying. Chinese patent CN102942226A also indicates that the dry gel after self-propagating combustion still needs to be calcined at 800-1000℃ to obtain well-crystallized single-phase YIG. Meanwhile, the research by HA Harwig et al. in Thermochimica Acta, 1979, 28(1): 121-131. pointed out that the melting point of bismuth oxide is only about 825℃, and a violent phase transition occurs above 730℃. This means that the above approach cannot fundamentally resolve the contradiction between the volatilization of low-melting-point dopants and the high temperature required for phase formation, making it difficult to prepare powders with high Bi content and precise stoichiometry.

[0005] Chinese patent CN109133167A discloses a method for preparing copper zirconate powder using a high-temperature mechanochemical method, which promotes the reaction by introducing argon gas for protection and heating during ball milling. While this prior art reveals a "high temperature + ball milling" process, it targets zirconate systems and only employs a single inert atmosphere for control. For the Ce, Bi:YIG system, there exists an extremely complex "valence state-volatilization" contradiction: Ce... 3+ It is easily oxidized to Ce at high temperatures. 4+ , while Bi 3+ Bi is highly volatile under low pressure or high temperature. Simple argon protection processes cannot precisely prevent Ce oxidation and lack mechanisms to inhibit Bi volatilization. Chinese patent CN106517865B discloses that traditional solid-state methods typically require long-term sintering at temperatures above 1100℃, far exceeding Bi's melting point limit, leading to severe volatilization. Furthermore, chemical co-precipitation methods are limited by Fe... 3+ With Y 3+ The significant differences in precipitation behavior, as pointed out by Zhang W et al. in *Materials Chemistry and Physics*, 2011, 125(3): 646-651, lead to "stepwise precipitation," causing component stratification within the precursor particles and negating the advantages of molecular-level mixing. Therefore, a new method is urgently needed to prepare Ce and Bi ion-doped yttrium iron garnet powder. Summary of the Invention

[0006] This invention aims to provide a method for preparing ion-doped yttrium iron garnet powder. This method utilizes a polymeric network gel to lock the spatial distribution of Y, Fe, Ce, and Bi ions, suppressing microscopic segregation caused by hydrolysis differences. Subsequently, organic matter in the polymeric network gel is removed to obtain an oxide precursor. The oxide precursor is then ball-milled under controlled pressure in a high-temperature horizontal ball mill, achieving single-phase garnet formation within a temperature window of 500–700 °C. This method effectively improves the doping accuracy and the reproducibility of low-temperature phase formation in the preparation of yttrium iron garnet powder.

[0007] A method for preparing ion-doped yttrium iron garnet powder, wherein the chemical composition of the ion-doped yttrium iron garnet powder is Ce. a Bi b Y (3-a-b) Fe5O 12 Where a≤0.4, b≤0.4, and a and b are not both 0, the method includes the following process steps:

[0008] S1, based on the chemical composition Ce of the target ion-doped yttrium iron garnet powder. a Bi b Y (3-a-b) Fe5O 12 A mixed metal nitrate solution containing Y, Fe ions and Ce and Bi ions required for the target chemical composition was prepared. A complexing agent, citric acid monohydrate, was added and the pH was adjusted. Then, a hydrophilic polypolymerizable monomer, acrylamide, a crosslinking agent, N,N-methylenebisacrylamide, and an initiator, ammonium persulfate, were added. Polymerization was carried out to obtain a polymeric network wet gel, which was then dried to obtain a polymeric network dry gel.

[0009] S2, the polymeric network dry gel obtained in step S1 is treated at 300~500 °C for a period of time to obtain a loose and porous oxide precursor powder;

[0010] S3. The oxide precursor powder obtained in step S2 is placed in the grinding jar of a high-temperature horizontal ball mill, and three sizes of grinding balls are filled in. The diameters of the three sizes of grinding balls are 5 mm, 8 mm, and 12 mm, and the mass fractions of the three sizes of grinding balls are 20%~30%, 50%~55%, and 20%~30%, respectively, with the sum of the three mass fractions being 100%. The ball-to-material ratio is 40:1. After filling, ball milling begins. Ball milling includes three stages: heating, holding, and cooling. The ball milling is maintained at the same speed in all three stages. The ball milling speed is 65%~85% of the critical speed of the ball mill. The holding temperature is 500~700 ℃. The total gauge pressure of the ball mill is 0.11~0.20 MPa. The atmosphere of the ball mill is as follows: during the heating and holding stages, argon gas with an oxygen content ≤0.005% is introduced; during the cooling stage, argon gas with an oxygen content of 0.05% is introduced for 10~30 minutes at the beginning of cooling. During the remaining cooling stage, argon gas with an oxygen content ≤0.005% is introduced.

[0011] Preferably, the chemical composition of the ion-doped yttrium iron garnet powder is Ce. a Bi b Y (3-a-b) Fe5O 12 , where a≤0.2, b≤0.2.

[0012] The ion-doped yttrium iron garnet powder Ce of the present invention a Bi b Y (3-a-b) Fe5O 12 In this context, Y, Fe, Ce, and Bi ions are Y 3 + Fe 3+ Ce 3+ Bi 3+ Ce-doped ions 3+ and Bi 3+ Occupying Y in the crystal lattice 3+ The location. Accordingly, in step S1, the preparation containing Y is... 3 + Fe 3+ and the Ce required for the target chemical composition 3+ Bi 3+ A mixed metal nitrate solution.

[0013] Further, the preparation of the Y-containing 3+ Fe 3+ Ce 3+ Bi 3+The raw materials for the mixed metal nitrate solution are nitrates or nitrate hydrates of the above ions, such as Y(NO3)3·6H2O, Fe(NO3)3·9H2O, Ce(NO3)3·6H2O, Bi(NO3)3·5H2O, etc.

[0014] Step S3 of this invention employs a high-temperature horizontal ball mill with a scattering motion. Compared to the relatively disordered movement of grinding balls during the grinding process in a vertical ball mill, the horizontal ball mill allows the grinding balls to form a more stable motion state under the combined action of gravity and centrifugal force during rotation, mainly including three forms: scattering, cascading, and rolling. In the scattering motion state, the grinding balls are carried to a certain height by the rotation of the tank and then detach from the tank wall and fall, impacting the powder. Larger grinding balls play a major role in this process, facilitating the breaking down of hard porous skeletons or agglomerates formed in the oxide precursor powder, transforming them from larger agglomerates to smaller particles, thereby increasing the reaction interface and improving subsequent mixing uniformity. In the cascading and rolling motion states, the grinding balls roll, slide, and undergo interlayer shearing along the powder surface, generating continuous friction and shearing effects. Smaller and medium-sized grinding balls play a major role in this process, providing a higher contact frequency and more thorough mixing, which is beneficial for promoting powder dispersion and homogenization, and reducing the tendency for re-agglomeration caused by excessive local energy. Meanwhile, the friction and localized plastic deformation between the grinding balls and the powder help introduce certain defects, increasing the powder's reactivity and thus promoting solid-phase reactions and improving product uniformity. Therefore, this invention employs a graded ratio of large, medium, and small grinding balls to synergistically regulate the impact, shearing, and frictional effects during the ball milling process. Through this grinding ball gradation, combined with appropriate rotational speed, ball-to-material ratio, and temperature conditions, the stability and consistency of the powder processing can be improved while ensuring reaction efficiency.

[0015] In the atmosphere ball milling step of this invention, the selection of the ball milling speed has a significant impact on the mechanical activation effect. The "critical speed" mentioned in this invention refers to the theoretical speed at which the grinding balls just rotate with the inner wall of the ball mill without falling off, and its calculation formula is as follows: n c =42.4 / D 1 / 2 Where nc is the critical speed in r / min and D is the effective inner diameter of the ball mill jar in m. This invention controls the ball milling speed within 65% to 85% of the critical speed, keeping the grinding balls in a predominantly spherical motion. Within this speed range, the grinding balls can generate relatively effective impact and shearing action on the material, which is beneficial for transferring mechanical energy to the powder system, promoting solid-phase reactions and ion diffusion under low-temperature conditions. This helps to promote the phase formation of powdered garnet at 500–700 °C and improves the phase composition uniformity of the product and the repeatability of the process.

[0016] Preferably, step S1 is: according to the chemical composition Ce of the target ion-doped yttrium iron garnet powder. a Bi b Y (3-a-b) Fe5O 12 A mixed metal nitrate solution containing Y, Fe ions and Ce and Bi ions required for the target chemical composition was prepared. Citric acid monohydrate, a complexing agent, was added to the mixed metal nitrate solution and stirred until dissolved. Ammonia solution with a mass fraction of 25% was added to adjust the pH to 5.0 ± 0.1, yielding a metal-citric acid complex precursor solution. The hydrophilic polymerizable monomer acrylamide and the crosslinking agent N,N-methylenebisacrylamide were dissolved in water to obtain a monomer-crosslinking agent system. This system was added to the metal-citric acid complex precursor solution and mixed thoroughly to obtain a mixed solution, maintaining a water bath temperature of 40 °C. Ammonium persulfate, an initiator, was added to the mixed solution at 0.5%–1.5% of the mass of the hydrophilic polymerizable monomer. The mixture was stirred in a 70 °C water bath for 3 h to form a polymeric network wet gel. The polymeric network wet gel was dried at 70–90 °C for 8–32 h to obtain a polymeric network dry gel.

[0017] Furthermore, the concentration of Fe ions in the mixed metal nitrate solution is 0.5~1 mol / L.

[0018] Furthermore, the concentration of the hydrophilic polypolymerizable monomer acrylamide in water is 4.0~7.5 mol / L.

[0019] Furthermore, the concentration of the crosslinking agent N,N-methylenebisacrylamide in water is 0.4~1.2 mol / L.

[0020] Furthermore, the molar ratio of the hydrophilic polypolymerizable monomer acrylamide to all metal cations in the mixed metal nitrate solution is 5~25:1.

[0021] Furthermore, the molar ratio of the complexing agent hydrated citric acid to all metal cations in the mixed metal nitrate solution is 1.25~2:1.

[0022] Preferably, step S2 is: treating the polymeric network dry gel obtained in step S1 in a muffle furnace at 300~500 °C for 2~8 h to obtain oxide precursor powder.

[0023] Preferably, step S2 is performed in air or an oxygen-containing atmosphere.

[0024] Preferably, in step S3, the effective inner diameter of the ball mill jar is 0.15 m, and the ball milling speed is 71~93 r / min.

[0025] Preferably, in step S3, the heat-insulating ball milling time is 4~8 h.

[0026] Preferably, in step S3, the heating rate is 2.5~4 ℃ / min and the cooling rate is 80~100 ℃ / h.

[0027] Further, the temperature is increased at a rate of 2.5~4 ℃ / min, and ball milling is started simultaneously with the temperature increase. After the temperature reaches 500~700℃, ball milling is maintained at this temperature for 4~8 h. During the temperature increase and maintenance stages, argon gas with an oxygen content ≤0.005% is introduced. After ball milling for 4~8 h, the temperature is decreased at a rate of 80~100 ℃ / h, ball milling is maintained, and argon gas with an oxygen content of 0.05% is introduced for 10~30 min. During the remaining temperature decrease stages, ball milling is maintained, and argon gas with an oxygen content ≤0.005% is introduced until the temperature drops to room temperature.

[0028] Preferably, in step S3, the effective inner diameter of the ball mill jar is 0.15 m, the ball milling speed is 71~93 r / min, and the ball milling time is 4~12 h.

[0029] Preferably, in step S3, the grinding jar is a 304 austenitic stainless steel grinding jar; and the grinding balls are 304 austenitic stainless steel grinding balls.

[0030] This invention uses a stainless steel grinding jar and grinding balls, instead of conventional high-hardness inert ceramic grinding media. This is because, considering the compositional characteristics of the iron-based garnet system, the components introduced by the wear of stainless steel during the grinding process are homologous to the system's composition, thus reducing impurity contamination.

[0031] The beneficial effects of this invention are as follows: The method of this invention first uses a polymer network gel method to prepare a polymer network gel, which allows the various metal components to be uniformly dispersed in the three-dimensional network of the gel. This helps to reduce local precipitation and component segregation of components such as Fe, and shortens the phase formation diffusion path. Subsequently, the organic components are removed from the polymer network gel to obtain oxide precursor powder. This powder has a uniform composition, which can improve the low-temperature phase formation efficiency and reduce the formation of intermediate phases. Finally, the oxide precursor powder is placed in a high-temperature horizontal ball mill for ball milling. By synergistically controlling the ball milling conditions, oxygen partial pressure, and micro-positive pressure in the furnace, the low-temperature solid-phase reaction is promoted while taking into account the stability of Ce valence state and the suppression of Bi volatilization. Y participates in maintaining charge compensation, thereby improving the doping accuracy and compositional stability. XRD, SEM, EDS, and valence state analysis results show that the ion-doped yttrium iron garnet powder prepared by the method of this invention has a good degree of target phase formation, a relatively uniform element distribution, and a low tendency to agglomerate. The valence state stability of related elements is good, which is beneficial to improving the material performance consistency, long-term stability, and batch stability. Attached Figure Description

[0032] Figure 1The image shows the microstructure of the polymeric network dry gel obtained in Example 1.

[0033] Figure 2 The image shows the microstructure of the polymeric network dry gel obtained in Example 3.

[0034] Figure 3 Ce obtained in Example 1 0.2 Y 2.8 Fe5O 12 Microscopic morphology of garnet powder.

[0035] Figure 4 Ce obtained in Example 3 0.2 Bi 0.2 Y 2.6 Fe5O 12 Microscopic morphology of garnet powder.

[0036] Figure 5 Ce obtained for Comparative Example 1 0.2 Bi 0.2 Y 2.6 Fe5O 12 Microscopic morphology of garnet powder.

[0037] Figure 6 Ce obtained in Example 1 0.2 Y 2.8 Fe5O 12 XPS high-resolution energy dispersive spectroscopy of Ce 3d orbitals in garnet powder.

[0038] Figure 7 Ce obtained in Examples 1, 3 and Comparative Example 1 0.2 Bi 0.2 Y 2.6 Fe5O 12 Particle size analysis of garnet powder.

[0039] Figure 8 (a), (b), (c) and (d) are Ce obtained in Example 1, respectively. 0.2 Y 2.8 Fe5O 12 Microscopic morphology of garnet powder and scanned images of the surface distribution of Fe, Y, and Ce elements.

[0040] Figure 9 Ce obtained in Example 3 0.2 Bi 0.2 Y 2.6 Fe5O 12 XRD pattern of garnet powder.

[0041] Figure 10 Ce obtained in Comparative Example 1 and Example 3 0.2 Bi0.2 Y 2.6 Fe5O 12 XRD pattern of garnet powder. Detailed Implementation

[0042] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0043] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0044] Example 1 Preparation of Ce 0.2 Y 2.8 Fe5O 12 The method for producing garnet powder includes the following steps:

[0045] Weigh 26.81 g of Y(NO3)3·6H2O, 50.50 g of Fe(NO3)3·9H2O, and 2.171 g of Ce(NO3)3·6H2O respectively, dissolve them in 200 mL of deionized water, and stir until dissolved to obtain a mixed metal nitrate solution; weigh 52.53 g of citric acid monohydrate and add it to the mixed metal nitrate solution, stir until dissolved, and add 25% ammonia water to adjust the pH of the solution to 5.0±0.1 to obtain a metal-citric acid complex precursor solution; weigh 142.16 g of acrylamide and 38.54 g of N,N-methylenebisacrylamide, add them to 200 mL of deionized water and dissolve to obtain a monomer-crosslinking agent system; add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well to obtain a mixed solution, and maintain the water bath temperature at 40 ℃; add 1.42 g of ammonium persulfate to the mixed solution, and heat at 70 ℃. The polymeric network wet gel was formed by heating and stirring in a water bath at ℃ for 3 h. The polymeric network wet gel was then dried in a 90 ℃ drying oven for 24 h to obtain a polymeric network dry gel. The polymeric network dry gel was placed in a muffle furnace and calcined at 500 ℃ for 8 h to decompose organic matter. The furnace was then cooled to room temperature to obtain oxide precursor powder. The calcination process was carried out in an air atmosphere, and the air atmosphere inside the furnace was maintained by a ventilation device. The oxide precursor powder was mixed with stainless steel grinding balls (the grinding balls had diameters of 5 mm, 8 mm, and 12 mm, and mass fractions of 20%, 50%, and 30%, respectively) at a mass ratio of 1:40 and placed in a stainless steel ball mill jar. The mixture was then ball-milled in a high-temperature horizontal ball mill. The ball milling reaction included a heating stage, a holding stage, and a cooling stage. The ball milling speed was the same in each stage, 93 r / min; the heating rate was 2.5 ℃ / min, and the cooling rate was 80 ℃ / h. During the heating and holding stages, the atmosphere was controlled with argon gas containing 0.005% oxygen. Ball milling was carried out at 700 °C for 6 h. At the start of cooling, ball milling was maintained while argon gas containing 0.05% oxygen was introduced for 30 min. During the remaining cooling stages, ball milling was maintained while argon gas containing 0.005% oxygen was introduced. The oxygen content was monitored throughout the ball milling reaction. Ce was finally obtained. 0.2 Y 2.8 Fe5O 12 Garnet powder.

[0046] The Ce obtained in Example 1 0.2 Y 2.8 Fe5O 12 The powder has minimal particle agglomeration and good uniformity, with a particle size range of approximately 250–350 nm.

[0047] Example 2 Preparation of Ce 0.4 Y 2.6 Fe5O 12The method for producing garnet powder includes the following steps:

[0048] Weigh 24.89 g, 50.50 g, and 4.34 g of Y(NO3)3·6H2O, Fe(NO3)3·9H2O, and Ce(NO3)3·6H2O respectively, and dissolve them in 200 mL of deionized water. Stir until dissolved to obtain a mixed metal nitrate solution. Weigh 63.04 g of citric acid monohydrate and add it to the mixed metal nitrate solution. Stir until dissolved, and add 25% ammonia solution to adjust the pH of the solution to 4.0±0.1 to obtain a metal-citric acid complex precursor solution. Weigh 213.24 g of acrylamide and 57.81 g of N,N-methylenebisacrylamide, and dissolve them in 200 mL of deionized water to obtain a monomer-crosslinking agent system. Add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well to obtain a mixed solution, and maintain the water bath temperature at 50°C. Add 1.70 g of ammonium persulfate to the mixed solution and heat at 80°C. The polymeric network wet gel was formed by heating and stirring in a water bath at ℃ for 2.5 h. The polymeric network wet gel was then dried in an 80 ℃ drying oven for 8 h to obtain a polymeric network dry gel. The polymeric network dry gel was placed in a muffle furnace and calcined at 500 ℃ for 2 h to decompose organic matter. It was then cooled to room temperature with the furnace to obtain oxide precursor powder. The calcination process was carried out in an air atmosphere, and the air atmosphere inside the furnace was maintained by a ventilation device. The oxide precursor powder was mixed with stainless steel grinding balls (the grinding balls had diameters of 5 mm, 8 mm, and 12 mm, and mass fractions of 25%, 50%, and 25%, respectively) at a mass ratio of 1:40 and placed in a stainless steel ball mill jar. The mixture was then ball-milled in a high-temperature horizontal ball mill. The ball milling reaction included a heating stage, a holding stage, and a cooling stage. The ball milling speed was the same in each stage, 93 r / min; the heating rate was 4 ℃ / min, and the cooling rate was 100 ℃ / h. During the heating and holding stages, the atmosphere was controlled with argon gas containing 0.005% oxygen. Ball milling was carried out at 700 °C for 8 h. At the start of cooling, ball milling was maintained while argon gas containing 0.05% oxygen was introduced for 10 min. During the remaining cooling stages, ball milling was maintained while argon gas containing 0.005% oxygen was introduced. The oxygen content was monitored throughout the ball milling reaction. Ce was ultimately obtained. 0.4 Y 2.6 Fe5O 12 Garnet powder.

[0049] The Ce obtained in Example 2 0.4 Y 2.6 Fe5O 12 The powder has minimal particle agglomeration and good uniformity, with a particle size range of approximately 320–400 nm.

[0050] Example 3 Preparation of Ce0.2 Bi 0.2 Y 2.6 Fe5O 12 The method for producing garnet powder includes the following steps:

[0051] Weigh 24.89 g, 50.50 g, 2.17 g, and 2.42 g of Y(NO3)3·6H2O, Fe(NO3)3·9H2O, Ce(NO3)3·6H2O, and Bi(NO3)3·5H2O respectively, and dissolve them in 200 mL of deionized water. Stir until dissolved to obtain a mixed metal nitrate solution. Weigh 84.05 g of citric acid monohydrate and add it to the mixed metal nitrate solution. Stir until dissolved, and add 25% ammonia solution to adjust the pH of the solution to 5.0 ± 0.1 to obtain a metal-citric acid complex precursor solution. Weigh 113.72 g of acrylamide and 24.66 g of N,N-methylenebisacrylamide, and dissolve them in 200 mL of deionized water to obtain a monomer-crosslinking agent system. Add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well, and maintain the water bath temperature at 60°C. ℃; 1.70 g of ammonium persulfate was added to the mixed solution and heated and stirred in a water bath at 80 ℃ for 0.5 h to form a polymeric network wet gel; the polymeric network wet gel was dried in a drying oven at 70 ℃ for 12 h to obtain a polymeric network dry gel; the polymeric network dry gel was placed in a muffle furnace and calcined at 400 ℃ for 8 h to decompose organic matter, and cooled to room temperature with the furnace to obtain oxide precursor powder. The calcination process was carried out in an air atmosphere, and the air atmosphere in the furnace was maintained by a ventilation device; the oxide precursor powder was mixed with stainless steel grinding balls (the diameters of the grinding balls were 5 mm, 8 mm and 12 mm, and the mass fractions were 20%, 50% and 30% respectively) at a mass ratio of 1:40 and placed in a stainless steel ball mill jar for ball milling reaction in a high-temperature horizontal ball mill. The ball milling reaction included a heating stage, a holding stage, and a cooling stage, with the same milling speed of 83 r / min in each stage; the heating rate was 4 ℃ / min, the cooling rate was 100 ℃ / h, and the reactor pressure was set to 0.2 MPa. During the heating and holding stages, the atmosphere was controlled with argon gas containing 0.005% oxygen; the ball milling was carried out at 600℃ for 6 h; at the start of cooling, the ball milling was maintained while argon gas containing 0.05% oxygen was introduced for 20 min, and the remaining cooling stages were also maintained while argon gas containing 0.005% oxygen was introduced. The oxygen content was monitored throughout the entire ball milling reaction. Ce was ultimately obtained. 0.2 Bi 0.2 Y 2.6 Fe5O 12 Garnet powder.

[0052] The Ce obtained in Example 3 0.2Bi 0.2 Y 2.6 Fe5O 12 The powder has minimal particle agglomeration and good uniformity, with a particle size range of approximately 350~510 nm.

[0053] Example 4 Preparation of Bi 0.2 Y 2.8 Fe5O 12 The method for producing garnet powder includes the following steps:

[0054] Weigh 26.81 g of Y(NO3)3·6H2O, 50.50 g of Fe(NO3)3·9H2O, and 2.42 g of Bi(NO3)3·5H2O respectively, dissolve them in 200 mL of deionized water, and stir until dissolved to obtain a mixed metal nitrate solution; weigh 63.04 g of citric acid monohydrate and add it to the mixed metal nitrate solution, stir until dissolved, and add 25% ammonia water to adjust the pH of the solution to 5.0±0.1 to obtain a metal-citric acid complex precursor solution; weigh 142.16 g of acrylamide and 15.41 g of N,N-methylenebisacrylamide, add them to 200 mL of deionized water and dissolve to obtain a monomer-crosslinking agent system; add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well to obtain a mixed solution, and maintain the water bath temperature at 40℃; add 1.42 g of ammonium persulfate to the mixed solution, and heat at 75℃. The polymeric network wet gel was formed by heating and stirring in a water bath at ℃ for 0.5 h. The polymeric network wet gel was then dried in a 70 ℃ drying oven for 24 h to obtain a polymeric network dry gel. The polymeric network dry gel was placed in a muffle furnace and calcined at 400 ℃ for 4 h to decompose organic matter. It was then cooled to room temperature with the furnace to obtain oxide precursor powder. The calcination process was carried out in an air atmosphere, and the air atmosphere inside the furnace was maintained by a ventilation device. The oxide precursor powder was mixed with stainless steel grinding balls (the grinding balls had diameters of 5 mm, 8 mm, and 12 mm, and mass fractions of 30%, 50%, and 20%, respectively) at a mass ratio of 1:40 and placed in a stainless steel ball mill jar. The mixture was then ball-milled in a high-temperature horizontal sling mill. The ball-milling reaction included a heating stage, a holding stage, and a cooling stage. The ball milling speed was the same in each stage, 75 r / min. The heating rate was 3.5 ℃ / min, the cooling rate was 100 ℃ / h, and the pressure inside the reactor was set to 0.2 MPa. During the heating and holding stages, the atmosphere was controlled with argon gas containing 0.004% oxygen. Ball milling was carried out at 700 °C for 4 h. At the start of cooling, ball milling was maintained while argon gas containing 0.05% oxygen was introduced for 20 min. During the remaining cooling stages, ball milling was maintained while argon gas containing 0.004% oxygen was introduced. The oxygen content was monitored throughout the ball milling reaction. Bi was finally obtained. 0.2 Y 2.8Fe5O 12 Yttrium iron garnet powder.

[0055] The Bi prepared in Example 4 0.2 Y 2.8 Fe5O 12 The powder has minimal particle agglomeration and good uniformity, with a particle size range of approximately 300–500 nm.

[0056] Example 5 Preparation of Bi 0.4 Y 2.6 Fe5O 12 The method for producing yttrium iron garnet powder includes the following steps:

[0057] Weigh 24.89 g, 50.50 g, and 4.85 g of Y(NO3)3·6H2O, Fe(NO3)3·9H2O, and Bi(NO3)3·5H2O respectively, and dissolve them in 200 mL of deionized water. Stir until dissolved to obtain a mixed metal nitrate solution. Weigh 84.05 g of citric acid monohydrate and add it to the mixed metal nitrate solution. Stir until dissolved, and add 25% ammonia water to adjust the pH of the solution to 4.0±0.1 to obtain a metal-citric acid complex precursor solution. Weigh 142.16 g of acrylamide and 20.55 g of N,N-methylenebisacrylamide, and dissolve them in 200 mL of deionized water to obtain a monomer-crosslinking agent system. Add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well, and maintain the water bath temperature at 50°C. Add 1.42 g of ammonium persulfate to the mixed solution and heat at 70°C. The polymeric network wet gel was formed by heating and stirring in a water bath at ℃ for 1 h. The polymeric network wet gel was then dried in an 80 ℃ drying oven for 24 h to obtain a polymeric network dry gel. The polymeric network dry gel was placed in a muffle furnace and calcined at 300 ℃ for 8 h to decompose organic matter. It was then cooled to room temperature with the furnace to obtain oxide precursor powder. The calcination process was carried out in an air atmosphere, and the air atmosphere inside the furnace was maintained by a ventilation device. The oxide precursor powder was mixed with stainless steel grinding balls (the grinding balls had diameters of 5 mm, 8 mm, and 12 mm, and mass fractions of 25%, 55%, and 20%, respectively) at a mass ratio of 1:40 and placed in a stainless steel ball mill jar. The ball milling reaction was carried out in a high-temperature horizontal sling mill. The ball milling reaction included a heating stage, a holding stage, and a cooling stage. The ball milling speed was the same in each stage, 71 r / min. The heating rate was 4 ℃ / min, the cooling rate was 90 ℃ / h, and the pressure inside the reactor was set to 0.11 MPa. During the heating and holding stages, the atmosphere was controlled with argon gas containing 0.005% oxygen. Ball milling was carried out at 700 °C for 6 h. At the start of cooling, ball milling was maintained while argon gas containing 0.05% oxygen was introduced for 30 min. During the remaining cooling stages, ball milling was maintained while argon gas containing 0.005% oxygen was introduced. The oxygen content was monitored throughout the ball milling reaction. Bi was finally obtained. 0.4 Y 2.6 Fe5O 12 Yttrium iron garnet powder.

[0058] The Bi prepared in Example 5 0.4 Y 2.6 Fe5O 12 The powder has minimal particle agglomeration and good uniformity, with a particle size range of approximately 490~580 nm.

[0059] Comparative Example 1 Preparation of Ce 0.2 Bi 0.2 Y2.6 Fe5O 12 The method for producing garnet powder involves a polymer network structure method combined with organic matter removal treatment and high-temperature ball milling, including the following steps:

[0060] Weigh 24.89 g, 50.50 g, 2.17 g, and 2.42 g of Y(NO3)3·6H2O, Fe(NO3)3·9H2O, Ce(NO3)3·6H2O, and Bi(NO3)3·5H2O respectively, and dissolve them in 200 mL of deionized water. Stir until dissolved to obtain a mixed metal nitrate solution. Weigh 84.05 g of citric acid monohydrate and add it to the mixed metal nitrate solution. Stir until dissolved, and add 25% ammonia solution to adjust the pH of the solution to 5.0 ± 0.1 to obtain a metal-citric acid complex precursor solution. Weigh 113.72 g of acrylamide and 24.66 g of N,N-methylenebisacrylamide, and dissolve them in 200 mL of deionized water to obtain a monomer-crosslinking agent system. Add the monomer-crosslinking agent system to the metal-citric acid complex precursor solution, mix well, and maintain the water bath temperature at 60°C. ℃; 1.70 g of ammonium persulfate was added to the mixed solution and heated and stirred in a water bath at 80 ℃ for 0.5 h to form a polymeric network wet gel; the polymeric network wet gel was dried in a drying oven at 70 ℃ for 12 h to obtain a polymeric network dry gel; the polymeric network dry gel was placed in a muffle furnace and calcined at 400 ℃ for 8 h to decompose organic matter, and then cooled to room temperature with the furnace to obtain oxide precursor powder; the oxide precursor powder was mixed with stainless steel grinding balls with a diameter of 12 mm at a mass ratio of 1:40 and placed in a ball milling jar for ball milling reaction in a vertical high-energy ball mill. The ball milling reaction included a heating stage, a holding stage and a cooling stage, and the ball milling speed was the same in the heating, holding and cooling stages, all at 120 r / min. The ball milling reaction was carried out at 600 ℃ for 6 h under an argon atmosphere, with a heating rate of 4 ℃ / min and a cooling rate of 100 ℃ / h. Ce prepared in Comparative Example 1 0.2 Bi 0.2 Y 2.6 Fe5O 12 The powder exhibits particle agglomeration behavior, and the phase composition varies to some extent.

[0061] Figure 1 and 2 The figures show the microstructures of the polymeric network dry gels obtained in Examples 1 and 3, respectively. As can be seen from the figures, the polymeric network effectively confines the metal ions. Figure 3 and 4 The microstructures of the garnet powders obtained in Examples 1 and 3 are shown respectively, indicating that the present invention can obtain highly crystalline powders at low temperatures of 500~700 ℃. Figure 5Ce obtained for Comparative Example 1 0.2 Bi 0.2 Y 2.6 Fe5O 12 The microstructure of garnet powder is determined by... Figure 4 and 5 As can be seen from the comparison, the powder prepared by the high-temperature horizontal ball mill has a smaller particle size and less agglomeration. Figure 6 The Ce obtained in Example 1 is shown. 0.2 Y 2.8 Fe5O 12 The XPS high-resolution energy spectrum of Ce 3d orbitals in garnet powder shows that the strong binding energy peak corresponds to Ce³. + Characteristic spin-orbit splitting peak (3d) 5 / 2 and 3D 3 / 2 No obvious Ce was observed. 4+ The characteristic peaks indicate that Ce mainly exists in the +3 valence state. Figure 7 Particle size analysis of the garnet powders obtained in Examples 1, 3 and Comparative Example 1. Figure 8 (a), (b), (c) and (d) are Ce obtained in Example 1, respectively. 0.2 Y 2.8 Fe5O 12 The microstructure of garnet powder and the elemental surface distribution scans of Fe, Y, and Ce show that the elements in the powder are uniformly distributed without segregation. Figure 9 Ce prepared in Example 3 0.2 Bi 0.2 Y 2.6 Fe5O 12 XRD pattern of garnet powder; Figure 10 Ce obtained for Comparative Example 1 and Comparative Example 3 0.2 Bi 0.2 Y 2.6 Fe5O 12 The XRD pattern of garnet powder shows that Ce in Example 3 is... 0.2 Bi 0.2 Y 2.6 Fe5O 12 Garnet powder lacks the characteristic peak of CeO2, and compared to Y3Fe5O... 12 The leftward shift of the peak position indicates the successful synthesis of doped single-phase material with no analytes detected. In contrast, the smaller peak shift in Comparative Example 1 suggests the presence of elemental escape or lack of doping, which can lead to inaccurate doping levels and discrepancies with the target. Conventional high-temperature ball milling is limited by factors such as the inability to programmatically control pressure and atmosphere, as well as the energy input limitations imposed by the milling container and carrier, making it impossible to achieve single-phase synthesis of Ce and Bi-doped yttrium iron garnet powder under specific target conditions.

Claims

1. A method for preparing ion-doped yttrium iron garnet powder, characterized in that, The chemical composition of the ion-doped yttrium iron garnet powder is Ce. a Bi b Y (3-a-b) Fe5O 12 Where a≤0.4, b≤0.4, and a and b are not both 0, the method includes the following process steps: S1, based on the chemical composition Ce of the target ion-doped yttrium iron garnet powder. a Bi b Y (3-a-b) Fe5O 12 A mixed metal nitrate solution containing Y, Fe ions and Ce and Bi ions required for the target chemical composition was prepared. A complexing agent, citric acid monohydrate, was added and the pH was adjusted. Then, a hydrophilic polypolymerizable monomer, acrylamide, a crosslinking agent, N,N-methylenebisacrylamide, and an initiator, ammonium persulfate, were added. Polymerization was carried out to obtain a polymeric network wet gel, which was then dried to obtain a polymeric network dry gel. S2, the polymeric network dry gel obtained in step S1 is treated at 300~500 °C for a period of time to obtain a loose and porous oxide precursor powder; S3. The oxide precursor powder obtained in step S2 is placed in the grinding jar of a high-temperature horizontal ball mill, and three sizes of grinding balls are filled in. The diameters of the three sizes of grinding balls are 5 mm, 8 mm, and 12 mm, and the mass fractions of the three sizes of grinding balls are 20%~30%, 50%~55%, and 20%~30%, respectively, with the sum of the three mass fractions being 100%. The ball-to-material ratio is 40:

1. After filling, ball milling begins. Ball milling includes three stages: heating, holding, and cooling. The ball milling is maintained at the same speed in all three stages. The ball milling speed is 65%~85% of the critical speed of the ball mill. The holding temperature is 500~700 ℃. The total gauge pressure of the ball mill is 0.11~0.20 MPa. The atmosphere of the ball mill is as follows: during the heating and holding stages, argon gas with an oxygen content ≤0.005% is introduced; during the cooling stage, argon gas with an oxygen content of 0.05% is introduced for 10~30 minutes at the beginning of cooling. During the remaining cooling stage, argon gas with an oxygen content ≤0.005% is introduced.

2. The method according to claim 1, characterized in that, Step S1 is as follows: according to the chemical composition Ce of the target ion-doped yttrium iron garnet powder. a Bi b Y (3-a-b) Fe5O 12 A mixed metal nitrate solution containing Y, Fe ions and Ce and Bi ions required for the target chemical composition was prepared. Citric acid monohydrate, a complexing agent, was added to the mixed metal nitrate solution and stirred until dissolved. Ammonia solution with a mass fraction of 25% was added to adjust the pH to 5.0 ± 0.1, yielding a metal-citric acid complex precursor solution. A monomer-crosslinking agent system was obtained by dissolving the hydrophilic polymerizable monomer acrylamide and the crosslinking agent N,N-methylenebisacrylamide in water. This monomer-crosslinking agent system was added to the metal-citric acid complex precursor solution and mixed thoroughly to obtain a mixed solution, maintaining the water bath temperature at 40 °C. Ammonium persulfate, an initiator, was added to the mixed solution at 0.5%–1.5% of the mass of the hydrophilic polymerizable monomer. The mixture was stirred in a 70 °C water bath for 3 h to form a polymeric network wet gel. The polymeric network wet gel was dried at 70-90 ℃ for 8-32 h to obtain the polymeric network dry gel.

3. The method according to claim 2, characterized in that, The concentration of Fe ions in the mixed metal nitrate solution is 0.5~1 mol / L.

4. The method according to claim 2, characterized in that, The concentration of the hydrophilic polypolymerizable monomer acrylamide in water is 4.0~7.5 mol / L, and the concentration of the crosslinking agent N,N-methylenebisacrylamide in water is 0.4~1.2 mol / L.

5. The method according to claim 2, characterized in that, The molar ratio of the hydrophilic polypolymerizable monomer acrylamide to all metal cations in the mixed metal nitrate solution is 5~25:1; the molar ratio of the complexing agent monohydrated citric acid to all metal cations in the mixed metal nitrate solution is 1.25~2:

1.

6. The method according to claim 1, characterized in that, Step S2 is as follows: The polymeric network dry gel obtained in step S1 is treated in a muffle furnace at 300~500 ℃ for 2~8 h to obtain a loose and porous oxide precursor powder.

7. The method according to claim 1, characterized in that, Step S2 is performed in air or an oxygen-containing atmosphere.

8. The method according to claim 1, characterized in that, In step S3, the effective inner diameter of the ball mill jar is 0.15 m, the ball milling speed is 71~93 r / min, and the heat-preserving ball milling time is 4~8 h.

9. The method according to claim 1, characterized in that, In step S3, the heating rate is 2.5~4 ℃ / min; the cooling rate is 80~100 ℃ / h.

10. The method according to claim 1, characterized in that, In step S3, the grinding jar is a 304 austenitic stainless steel grinding jar; the grinding balls are 304 austenitic stainless steel grinding balls.

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