Preparation method of Sc-substituted M-type Ba ferrite single crystal material

Abstract

The application relates to a preparation method of an Sc-substituted M-type Ba ferrite single crystal material, and belongs to the technical field of ferrite material preparation. The application takes BaCO3, Fe2O3 and Sc2O3 as raw materials, adopts an Sc substitution strategy according to ion occupation and anisotropy origin of the M-type Ba ferrite material, controls the temperature difference in the growth process furnace according to a non-uniform nucleation mechanism in the crystal growth process, forms a temperature gradient, controls the nucleation efficiency of the M-type Ba ferrite, provides driving force for the melt flow through rotation of a supporting table, controls the nucleation range of the M-type ferrite, and provides sufficient raw materials for the crystal growth, so that the Sc-substituted M-type Ba ferrite single crystal material with a single side size of more than 8 mm, low anisotropy field and low ferromagnetic resonance line width is prepared.

Description

Technical Field

[0001] This invention belongs to the field of ferrite material preparation technology, specifically relating to a method for preparing Sc-substituted M-type Ba ferrite single crystal material. Background Technology

[0002] Compared to polycrystalline materials, the advantages of M-type Ba ferrite single-crystal materials prepared by the molten salt method in applications such as microwave devices mainly stem from their long-range ordered lattice structure. In contrast to polycrystalline materials, single-crystal materials exhibit a highly ordered lattice structure, with atoms arranged in a long-range order. This ordered arrangement optimizes the formation and magnetization process of magnetic domains, enabling them to respond more efficiently to applied magnetic fields. Furthermore, single-crystal materials have fewer pores and defects, resulting in a higher density than polycrystalline materials and thus higher 4πM... s For polycrystalline materials, the main sources of excessively high ferromagnetic resonance linewidth (ΔH) are porosity and anisotropy. This linewidth is inherent to polycrystalline materials and cannot be eliminated, which is also the reason why polycrystalline M-type Ba ferrite often exhibits significant losses in microwave device applications. Therefore, the low anisotropy of single-crystal M-type Ba ferrite leads to a wider ΔH. a and low porosity leading to widening ΔH p This results in an extremely low overall ΔH, which is particularly effective in reducing device losses during microwave device applications. However, existing pure M-type Ba ferrite single crystal materials have a high anisotropic field (approximately 18 kOe) and a ferromagnetic resonance frequency f. r Its high frequency band (Ka band and above) makes it difficult to match with many practical application scenarios (K band and below). In single-crystal systems, non-magnetic ions are often used to replace Fe. 3+ The anisotropic field of M-type Ba ferrite can be modulated in a way that reduces its application frequency. Using non-magnetic Sc... 3+ For example, in the raw materials required for replacing M-type Ba ferrite single crystal materials with Sc, some of the Fe2O3 (melting point 1539℃) needs to be replaced with Sc2O3 (melting point 2458℃), which has a higher melting point. High-melting-point raw materials affect the melting degree of the melt during the molten salt process, thus inhibiting the uniform distribution of raw material molecules and the mass transfer rate, ultimately making it difficult to efficiently grow crystals to millimeter-sized or larger dimensions. Microwave devices (such as circulators) typically require ferrite substrates with dimensions of 4×4×0.5mm or larger. Therefore, how to prepare M-type Ba ferrite single crystal materials that meet the needs of different frequency bands and the size requirements of device processing, while maintaining their low-loss advantage, is of great strategic significance for broadening the application frequency bands of microwave devices and promoting the development of next-generation communication and radar detection technologies. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and provide a method for preparing Sc-substituted M-type Ba ferrite single crystal materials.

[0004] The core idea of ​​this invention is: based on the single-ion model theory, ferrites have high resistivity, and magnetic metal ions (such as Fe)... 3+ Isolated by nonmetallic ions, the electrons of ferrite materials can be considered localized, taking only their own spin-orbit coupling and crystal electric field effects into account. The magnetocrystalline anisotropy of ferrite materials largely depends on the number and configuration of electrons in the magnetic ions, as well as the symmetry and strength of the crystal electric field. Therefore, magnetocrystalline anisotropy can be controlled by altering the ionic magnetic moments at the ferrite's magnetic crystal sites through ion substitution. 3+ The 3d orbital of the ion has no electrons, resulting in unsplit polarization and making it a nonmagnetic ion. 3+ The substituted crystal sites will not produce any magnetic moment, and Sc 3+ Substitution of leads to a weakening of exchange coupling effects and dipole-dipole interactions at adjacent crystal sites. Using Sc 3+ Fe replacement 3+ This will effectively reduce the anisotropic field H of M-type Ba ferrite. a This reduces the frequency of application. On the other hand, increasing the proportion of flux and low-melting-point substances such as BaCO3 in the overall composition lowers the melting temperature, which is beneficial for the crystallization and growth of M-type Ba ferrite.

[0005] Furthermore, the growth process of M-type Ba ferrite prepared by the molten salt method requires the formation of crystal nuclei in the melt through a chemical reaction, followed by spontaneous crystallization under the driving force of a supersaturated (or supercooled) phase transformation, resulting in gradual crystal growth. Therefore, during crystal growth, conditions such as the container walls, impurities within the system, and external temperature all affect the critical size of the crystal nuclei, the nucleation rate, and the formation energy. By installing equidistantly distributed silicon-molybdenum rods at the top and bottom of the single-crystal furnace, and controlling the heating efficiency of the upper and lower parts of the furnace separately, a temperature difference is created from top to bottom within the furnace during crystal growth. This increases the nucleation rate at the bottom of the melt and decreases the nucleation rate in the upper half, achieving a non-uniform nucleation effect, reducing the number of crystal nuclei, and preserving sufficient raw materials for crystal growth, resulting in Sc-substituted M-type Ba ferrite single crystal material that meets processing requirements. Furthermore, the uniformly mixed mixture is filled into a platinum crucible, which is then placed in the center of a firing platform. A rotary motor is installed at the bottom of the platform. During the growth process, the crucible is slowly rotated to generate different centrifugal forces in different parts of the melt. The melt flow rate is lower at the center of the melt, allowing atoms to fully contact and react chemically to generate Sc-substituted M-type Ba ferrite crystal nuclei. The closer to the outer edge of the melt, the faster the melt flow rate, reducing the atomic contact time and thus controlling the non-uniform nucleation inside the melt. Under the continuous rotation of the crucible, the atoms in the melt continue to move, providing a continuous source of raw materials for the crystal growth process. This further promotes the increase in crystal size, ultimately growing Sc-substituted M-type Ba ferrite single crystal materials with a single-sided dimension of more than 8 mm.

[0006] This invention provides a method for preparing Sc-substituted M-type Ba ferrite single crystal materials, the obtained materials having a density d ≥ 5.12 g / cm³. 3 Single-sided dimension l≥8mm, Curie temperature T c ≥399℃, saturation magnetization 4πM s ≥4200Gs, anisotropic field H a Performance parameters: ≤12kOe, ferromagnetic resonance linewidth ΔH≤40Oe.

[0007] A method for preparing Sc-substituted M-type Ba ferrite single crystal material includes the following steps:

[0008] Step 1. Recipe;

[0009] Using BaCO3, Fe2O3 and Sc2O3 as raw materials, weigh the raw materials and mix them according to the ratio of "16.0~18.0wt% BaCO3, 75.0~83.0wt% Fe2O3, 1.0~5.0wt% Sc2O3".

[0010] Step 2. Mixing;

[0011] In step 1, add 15-30 wt% Na2CO3 as a flux to the mixed powder, mix it evenly in a drum ball mill, and the ball milling time is 4-8 hours.

[0012] Step 3. Crystal growth;

[0013] The powder obtained in step 2 is loaded into a platinum crucible and then placed in the furnace chamber of a single crystal furnace. The furnace is heated to 1200~1350℃ in an air atmosphere and held for 5~15 hours. The temperature is then slowly reduced to 900℃ at a rate of 2~8℃ / h. During the slow cooling process, the temperature difference between the top and bottom of the furnace chamber is maintained at 5~15℃, while the firing platform rotates at a rate of 5~20 rpm until the bottom area of ​​the furnace chamber is cooled to 900℃.

[0014] Step 4. Sour cooking;

[0015] The mixture obtained in step 3 is added to dilute nitric acid at 50~80℃ and ultrasonically treated to accelerate the reaction of oxides and salt impurities in the mixture and separate Sc-substituted M-type Ba ferrite single crystal material.

[0016] Furthermore, in step 3, the platinum crucible is placed at the center of the firing platform in the furnace chamber of the single crystal furnace.

[0017] Furthermore, in step 3, silicon molybdenum rods are installed at equal intervals at the top and bottom of the single crystal furnace chamber. During the crystal growth process, the heating power at the top and bottom of the furnace chamber is adjusted to create a temperature difference from top to bottom within the furnace chamber.

[0018] Furthermore, in step 4, the concentration of dilute nitric acid is 65~68 wt%.

[0019] The magnetic properties of the sample obtained in step 4 were tested. The saturation magnetization of the material (4π M) was measured using a LakeShore-8604 vibrating sample magnetometer. s The sample density d was tested using the Archimedes displacement method; the anisotropic field H of the material was calculated using the singular point method (SPD). a The ferromagnetic resonance linewidth ΔH of the material was measured using the resonant cavity perturbation method.

[0020] The final technical specifications of the Sc-substituted M-type ferrite single crystal material prepared by this invention are as follows:

[0021] Density d ≥ 5.12 g / cm³ 3 ;

[0022] Single-sided dimension l ≥ 8mm;

[0023] Curie temperature T c ≥399℃;

[0024] Saturation magnetization 4πM s ≥4200Gs;

[0025] Anisotropic field H a ≤12kOe;

[0026] The ferromagnetic resonance linewidth ΔH ≤ 40 Oe.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a method for preparing Sc-substituted M-type Ba ferrite single crystals. By creating a temperature gradient and using rotation-controlled non-uniform nucleation during crystal growth, Sc-substituted M-type Ba ferrite single crystals are grown, with a single-sided crystal size exceeding 8 mm, meeting device fabrication requirements. The use of a non-magnetic Sc ​​substitution strategy effectively reduces the anisotropic field H of the material. a This broadens its application frequency range to meet the application requirements of K-band microwave devices; it also features a low ferromagnetic resonance linewidth, which effectively reduces insertion loss during device application. Attached Figure Description

[0029] Figure 1 The images show optical photographs of the single-crystal materials obtained in Examples 1-4 and their single-sided dimension measurements. Detailed Implementation

[0030] Addressing the current domestic and international demand and technological gap for M-type Ba ferrite single crystal materials for K-band circulators, this invention provides a method for preparing Sc-substituted M-type Ba ferrite single crystals through a Sc substitution strategy combined with temperature difference control and rotational growth. The guiding principles are: single-ion theoretical model, ion occupancy mechanism, heterogeneous nucleation model, and crystal growth mechanism. First, using BaCO3, Fe2O3, and Sc2O3 as raw materials, a Sc substitution strategy is adopted based on the ion occupancy and anisotropy origin of the M-type Ba ferrite material. Second, during crystal growth, the temperature difference inside the furnace is controlled according to the heterogeneous nucleation mechanism to form a temperature gradient and control the nucleation efficiency of the M-type Ba ferrite. Finally, under the premise of optimizing the above formula and preparation process, the rotation of the firing stage provides driving force for melt flow during growth, controlling the nucleation range of the M-type ferrite and providing sufficient raw materials for crystal growth, thereby achieving the preparation of Sc-substituted M-type Ba ferrite single crystal materials with a single-sided dimension of over 8 mm, low anisotropic field, and low ferromagnetic resonance linewidth.

[0031] A method for preparing Sc-substituted M-type Ba ferrite single crystal material includes the following steps:

[0032] Step 1. Recipe;

[0033] Using BaCO3, Fe2O3 and Sc2O3 as raw materials, weigh the raw materials and mix them according to the ratio of "16.0~18.0wt% BaCO3, 75.0~83.0wt% Fe2O3, 1.0~5.0wt% Sc2O3".

[0034] Step 2. Mixing;

[0035] In step 1, add 15-30 wt% Na2CO3 as a flux to the mixed powder, mix it evenly in a drum ball mill, and the ball milling time is 4-8 hours.

[0036] Step 3. Crystal growth;

[0037] The powder obtained in step 2 is loaded into a platinum crucible and then placed in the furnace chamber of a single crystal furnace. The furnace is heated to 1200~1350℃ in an air atmosphere and held for 5~15 hours. The temperature is then slowly reduced to 900℃ at a rate of 2~8℃ / h. During the slow cooling process, the temperature difference between the top and bottom of the furnace chamber is maintained at 5~15℃, while the firing platform rotates at a rate of 5~20 rpm until the bottom area of ​​the furnace chamber is cooled to 900℃.

[0038] Step 4. Sour cooking;

[0039] The mixture obtained in step 3 is added to dilute nitric acid at 50~80℃ and ultrasonically treated to accelerate the reaction of oxides and salt impurities in the mixture and separate Sc-substituted M-type Ba ferrite single crystal material.

[0040] The magnetic properties of the sample obtained in step 4 were tested. The saturation magnetization of the material (4π M) was measured using a LakeShore-8604 vibrating sample magnetometer. s The sample density d was tested using the Archimedes displacement method; the anisotropic field H of the material was calculated using the singular point method (SPD). a The ferromagnetic resonance linewidth ΔH of the material was measured using the resonant cavity perturbation method.

[0041] Example

[0042] Examples 1-4: Preparation methods of Sc-substituted M-type Ba ferrite single crystal materials;

[0043] Comparative Example 1: A method for preparing Sc-free M-type Ba ferrite single crystal material, comprising the following steps:

[0044] Step 1. Recipe;

[0045] The main formulations for Examples 1-4 are shown in the table below:

[0046]

[0047] The main formulation for Comparative Example 1 is shown in the table below:

[0048]

[0049] Step 2. Mixing;

[0050] In step 1, 20 wt% of Na2CO3 was added to the mixed powder as a flux, and the mixture was mixed evenly in a drum ball mill for 5 hours.

[0051] Step 3. Crystal growth;

[0052] The powder obtained in step 2 is loaded into a platinum crucible and then placed in the center of the single crystal furnace. The furnace is heated to 1300 ℃ in an air atmosphere and held for 8 hours. The temperature is then slowly reduced to 900 ℃ at a rate of 5 ℃ / h. During the slow cooling process, the temperature difference between the top and bottom of the furnace is maintained at 8 ℃, while the firing platform rotates at a rate of 10 rpm until the bottom area of ​​the furnace is cooled to 900 ℃.

[0053] Step 4. Sour cooking;

[0054] The mixture obtained in step 3 was added to 65wt% dilute nitric acid at 75 °C and ultrasonically treated to accelerate the reaction of oxides and salt impurities in the mixture and separate Sc-substituted M-type Ba ferrite single crystal material.

[0055] M-type Ba ferrite single crystal materials were prepared using the above process. The performance parameters of Examples 1-4 are as follows:

[0056]

[0057] The performance parameters of Comparative Example 1 are as follows:

[0058] .

Claims

1. A method for preparing a Sc-substituted M-type Ba ferrite single crystal material, characterized in that, Includes the following steps: Step 1. Recipe; Using BaCO3, Fe2O3 and Sc2O3 as raw materials, weigh the raw materials and mix them according to the ratio of "16.0~18.0wt% BaCO3, 75.0~83.0wt% Fe2O3, 1.0~5.0wt% Sc2O3". Step 2. Mixing; In step 1, add 15-30 wt% Na2CO3 as a flux to the mixed powder and ball mill to mix it evenly. Step 3. Crystal growth; The powder obtained in step 2 is loaded into a platinum crucible and then placed in the furnace chamber of a single crystal furnace. The furnace is heated to 1200~1350℃ in an air atmosphere and held for 5~15 hours, then cooled to 900℃. During the cooling process, the temperature difference between the top and bottom of the furnace chamber is maintained at 5~15℃, while the firing platform rotates at a rate of 5~20 rpm until the bottom area of ​​the furnace chamber drops to 900℃. Step 4. Sour cooking; The mixture obtained in step 3 was ultrasonically treated in dilute nitric acid and separated to obtain Sc-substituted M-type Ba ferrite single crystal material.

2. The method for preparing Sc-substituted M-type Ba ferrite single crystal material according to claim 1, characterized in that, In step 2, the ball milling time is 4 to 8 hours.

3. The method for preparing Sc-substituted M-type Ba ferrite single crystal material according to claim 1, characterized in that, In step 3, the temperature is reduced to 900℃ at a rate of 2~8℃ / h.

4. The method for preparing Sc-substituted M-type Ba ferrite single crystal material according to claim 1, characterized in that, In step 3, the platinum crucible is placed at the center of the firing platform in the furnace chamber of the single crystal furnace.

5. The method for preparing Sc-substituted M-type Ba ferrite single crystal material according to claim 1, characterized in that, In step 3, silicon molybdenum rods are installed at equal intervals at the top and bottom of the single crystal furnace. During crystal growth, the heating power at the top and bottom of the furnace is adjusted to create a temperature difference from top to bottom within the furnace.

6. The method for preparing Sc-substituted M-type Ba ferrite single crystal material according to claim 1, characterized in that, In step 4, the concentration of dilute nitric acid is 65~68wt%, and the temperature is 50~80℃.

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