X-band self-biased hexaferrite material based on cr substitution and method of making the same

Abstract

The application belongs to the technical field of ferrite material preparation, and specifically provides an X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution and a preparation method thereof, so as to meet the engineering needs of X-band miniature integrated devices; the X-band self-biased hexagonal gyromagnetic ferrite material in the application comprises: a BaM hexagonal ferrite and an additive, wherein the chemical formula of the BaM hexagonal ferrite is BaCr x Fe 11.2‑x O 19‑δ , 0

Description

Technical Field

[0001] This invention belongs to the field of ferrite material preparation technology, and particularly relates to X-band low-loss self-biased hexagonal gyratory magnetic ferrite material and its preparation method. Specifically, it provides an X-band self-biased hexagonal gyratory magnetic ferrite material based on Cr substitution and its preparation method. Background Technology

[0002] With the rapid development of 5G / 6G communication, satellite navigation, and military radar technologies, microwave devices are evolving towards higher frequencies, greater integration, miniaturization, and lower losses. As a core material for microwave devices, gyromagnetic ferrites occupy an irreplaceable position in key components such as circulators, isolators, and phase shifters due to their unique gyromagnetic effect and excellent electromagnetic properties. Currently, the X-band (8-12GHz), as the core frequency band for military radar, satellite communication, and electronic countermeasures systems, places more stringent performance requirements on gyromagnetic ferrite materials. These requirements necessitate ultra-low loss characteristics in high-frequency environments, while also ensuring high saturation magnetization, temperature stability, miniaturization, and weight reduction. Traditional microwave circulators often use spinel-type (such as NiFe2O4) or garnet-type (such as YIG) ferrites as the gyromagnetic medium. Their design relies on external permanent magnets to provide a bias magnetic field for unidirectional transmission and reverse isolation of radio frequency signals. In this structural design, the external magnet assembly typically accounts for 30%-50% of the total device weight, making it difficult to compress the circulator's longitudinal dimensions (typical thickness > 5mm), thus hindering the miniaturization of microwave devices. BaM hexagonal ferrite (chemical formula BaFe2O4) offers a solution. 12 O 19 The magnetoplumble-type crystal structure endows it with unique uniaxial magnetocrystalline anisotropy (anisotropic field H). a ≈20kOe), theoretically enabling self-biased operation in the X-band (8-12 GHz); compared to traditional garnet-type (YIG, H a ≈10Oe) and spinel-type materials (such as Ni2Fe4, H a ≈1kOe), its height H a The properties of this material eliminate the need for external magnets, directly providing a built-in bias field through lattice anisotropy. However, the anisotropic field of the pure BaM phase is too high, resulting in an excessively high ferromagnetic resonance linewidth. Furthermore, according to Kittel's formula, its ferromagnetic resonance frequency is too high and too far from the X-band, potentially leading to increased low-field losses. Therefore, the development of X-band self-biased hexagonal gyromagnetic ferrite materials is of great significance.

[0003] Regarding self-biased hexagonal ferrite materials, V. Laur, in his paper "Self-Biased Y-Junction Circulators Using Lanthanum- and Cobalt-Substituted Strontium Hexaferrites," proposed the application of polycrystalline lanthanum and cobalt-substituted strontium hexagonal ferrites in self-biased circulators. Sr was prepared using a solid-state sintering method. 0.8 La 0.2 Fe 11.8 Co 0.2 O 19 Hexagonal gyromagnetic ferrite material, with the following performance indicators: anisotropic field H a =20.3kOe, ferromagnetic resonance linewidth ΔH=1500Oe, remanence ratio M r / M s =0.9, coercivity H c =4400Oe. Nazia Yasmin, in her paper "Influence of samarium substitution on the structural and magnetic properties of M-type hexagonal ferrites," investigated the effect of rare earth substitution on the structure and magnetism of M-type hexagonal ferrites, and prepared SrSm using the sol-gel method. x Fe 12-x O 19 (x=0,0.01,0.02,0.03), the performance is optimal when x=0.02, and the performance index is: remanence ratio M r / M s =0.62, coercivity H c =1987Oe, without mentioning anisotropic fields. M. Awawdeh of the Physics Department at Yarmouk University in Irbid, Jordan, proposed BaM hexagonal ferrites with Ga and Al substitution respectively in his paper "Magnetic properties and Mössbauer spectroscopy on Ga,Al, and Cr substituted hexaferrites," and prepared BaFe using a solid-state reaction method. 12-x M x O 19 (M=Ga, Al, x=0.0, 0.2, 0.4, 0.6), it was found that as the substitution amount increases, the saturation magnetization decreases, the grain size decreases, leading to an increase in coercivity and anisotropic field H. a=12kOe, ferromagnetic resonance linewidth not mentioned. A. Baykal of the University of Darman, in his paper "Pb substituted Ba,Sr-hexaferrite nanoparticles as high quality microwave absorbers," investigated the effect of Pb substitution on the magnetic and microwave properties of barium strontium ferrite, preparing Ba using a solid-state reaction method. 0.5-x Sr 0.5-x Pb 2x Fe 12 O 19 (x=0,0.1,0.2,0.3,0.4), the performance is optimal when x=0.2, and the performance index is: remanence ratio M r / M s =0.52, coercivity H c =1820 Oe, anisotropic field not mentioned. Although the above materials have certain properties such as remanence ratio M r / M s Coercivity H c While achieving high performance, the variations in its anisotropic field and ferromagnetic resonance linewidth have not been fully explored, and the overall performance parameters cannot guarantee its application in microwave devices. Summary of the Invention

[0004] The purpose of this invention is to provide a Cr-substituted X-band self-biased hexagonal gyromagnetic ferrite material and its preparation method to meet the engineering requirements of X-band micro-integrated devices. This invention uses non-magnetic ions Cr to substitute Fe in BaM ferrite, effectively controlling the anisotropic field of BaM ferrite while reducing anisotropic broadening, lowering the anisotropic field of BaM ferrite to 10.0~12.0 kOe, thus enabling its application in the X-band. Simultaneously, the self-biased hexagonal gyromagnetic ferrite possesses high saturation magnetization, high remanence ratio and coercivity, and low ferromagnetic resonance linewidth, which is beneficial for comprehensively improving the bandwidth and insertion loss characteristics of circulators.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A Cr-substituted X-band self-biased hexagonal gyromagnetic ferrite material, characterized in that it comprises: BaM hexagonal ferrite and additives, wherein the chemical formula of the BaM hexagonal ferrite is BaCr. x Fe 11.2-x O 19-δ, where \(0 < x \leq 1.2\); based on the mass of the pre-sintered BaM hexagonal ferrite material, the additives include: \(0.1\ wt\%\) to \(1.5\ wt\%\) of \(SiO_2\), \(0.1\ wt\%\) to \(1.5\ wt\%\) of \(Bi_2O_3\), and \(0.1\ wt\%\) to \(2.0\ wt\%\) of \(CaCO_3\).

[0007] Further, the anisotropy field \(H\) of the X-band self-biased hexagonal ferrimagnetic material a is \(10.0\ kOe\) to \(12.0\ kOe\).

[0008] Further, the method for preparing the Cr-substituted X-band self-biased hexagonal ferrimagnetic material is characterized by comprising the following steps:

[0009] Step 1, proportioning;

[0010] Using \(BaCO_3\) with a purity of \(99.5\%\), \(Cr_2O_3\) with a purity of \(99.5\%\), and \(Fe_2O_3\) with a purity of \(99.3\%\) as raw materials, calculate and weigh according to the chemical formula \(BaCr x Fe 11.2- x O 19-δ , where \(0 < x \leq 1.2\);

[0011] Step 2, primary ball milling;

[0012] Perform primary ball milling on the proportioned materials obtained in Step 1, then dry and screen to obtain the primary ball milled materials;

[0013] Step 3, pre-sintering;

[0014] Place the sieved primary ball milled materials in an air atmosphere for pre-sintering. The pre-sintering temperature is \(1000^{\circ}C\) to \(1280^{\circ}C\), the holding time is \(1\ h\) to \(4\ h\), and the heating rate is \(1^{\circ}C / min\) to \(3^{\circ}C / min\) to obtain the pre-sintered BaM hexagonal ferrite materials;

[0015] Step 4, doping;

[0016] Based on the mass of the pre-sintered materials obtained in Step 3, add \(SiO_2\), \(Bi_2O_3\), and \(CaCO_3\) as additives to obtain the doped mixed powder;

[0017] Step 5, secondary ball milling;

[0018] Perform secondary ball milling on the doped mixed powder. The average particle size of the powder after ball milling is \(0.6\ \mu m\) to \(1.4\ \mu m\) to obtain the secondary ball milled slurry;

[0019] Step 6, forming;

[0020] Perform dehydration treatment on the slurry obtained in Step 5, and press the dehydrated slurry into a green body under a magnetic field forming press;

[0021] Step 7: Multi-stage atmosphere sintering;

[0022] The green billet obtained in step 6 is placed in a controlled atmosphere resistance furnace, and the furnace temperature is raised from room temperature to 950°C to accelerate the removal of moisture from the green billet and inhibit cracking of the green billet; the heating rate is 0.5°C / min to 2°C / min.

[0023] Then, the furnace temperature is continuously increased to 1200℃~1400℃ to allow the additives to be uniformly enriched at the grain boundaries and fully encapsulate the grains; the heating rate is 1℃ / min~3℃ / min.

[0024] Finally, it is kept at an oxygen atmosphere of 0.03 MPa to 0.06 MPa for 6 to 15 hours to reduce Fe. 2+ This process generates and eliminates closed pores, resulting in uniform and dense grains.

[0025] Furthermore, in step 4, the proportions of the additives are as follows: based on the mass of the BaM hexagonal ferrite pre-sintered material, SiO2: 0.1 wt%~1.5 wt%, Bi2O3: 0.1 wt%~1.5 wt%, CaCO3: 0.1 wt%~2.0 wt%.

[0026] Furthermore, in step 2, the ball milling time is 10 to 15 hours.

[0027] Furthermore, in step 5, the ball milling time is 12 to 24 hours.

[0028] Furthermore, in step 6, the moisture content of the slurry after dewatering is controlled between 4.0 wt% and 5.0 wt%.

[0029] Furthermore, in step 6, the parameters for pressing the green body are: the forming magnetic field strength is 0.6T~1.0T, the forming pressure is 80 MPa~120MPa, and the holding time is 70~120s.

[0030] In terms of working principle:

[0031] To address the problems of excessively high application frequency, large insertion loss, and narrow bandwidth in self-biased circulators, this invention proposes an X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution and its preparation method. Non-magnetic ions Cr are used to substitute Fe at the 12k crystal site in BaM ferrite to form BaM hexagonal ferrite BaCr. x Fe 11.2-x O 19-δ It should be noted that, regarding δ, because crystals often generate oxygen vacancies to compensate for the loss of positive charge due to the lack of Fe, causing the oxygen content to deviate from 19, δ represents the degree of oxygen vacancy generation. This expression is conventional in the field and does not have a specific numerical value. Cr 3+The magnetic moment (3 μB) is much smaller than that of Fe. 3+ Magnetic moment (5μB), and Cr 3+ with Fe 3+ The Fe-O-Cr magnetic exchange coupling between them is much weaker than that between Fe. 3+ The Fe-O-Fe coupling between the Fe atoms significantly reduces the contribution of the 12k sites to magnetic anisotropy. With increasing Cr substitution, the Fe-O-Cr bonding ratio further increases, disrupting the previously ordered Fe structure in the lattice. 3+ The magnetic moment alignment is disrupted, and the anisotropic characteristics of magnetic exchange coupling are weakened. Cr substitution effectively modulates the anisotropic field of BaM ferrite while reducing anisotropic broadening, lowering the anisotropic field of BaM ferrite to 10.0~12.0 kOe, thus enabling its application in the X-band.

[0032] Furthermore, Cr substitution can optimize the grain size of BaM ferrite materials, regulate the coercivity and remanence of BaM ferrite materials, and reduce the porosity of BaM ferrite materials, thus synergistically reducing the ferromagnetic resonance linewidth ΔH, which is beneficial for reducing the insertion loss of devices; at the same time, the use of an iron-deficient formulation reduces Fe 2+ This makes Fe 3+ / Fe 2+ The increase in the ratio leads to an increase in the resistivity of the material, further achieving the goal of reducing the ferromagnetic resonance linewidth ΔH. In addition, the iron-deficient formulation reduces the cell volume, promotes solid-state reactions, increases the material density, and reduces the porosity, further achieving the goal of reducing the ferromagnetic resonance linewidth ΔH.

[0033] In summary, the beneficial effects of the present invention are as follows:

[0034] This invention provides a Cr-substituted X-band self-biased hexagonal gyromagnetic ferrite material. It utilizes the non-magnetic ion Cr to replace Fe in BaM ferrite, effectively controlling the anisotropic field of BaM ferrite while reducing anisotropic broadening, lowering the anisotropic field of BaM ferrite to 10.0~12.0 kOe, thus enabling its application in the X-band. Simultaneously, the iron-deficient formulation design allows the self-biased hexagonal gyromagnetic ferrite to possess high saturation magnetization, high remanence and coercivity, and low ferromagnetic resonance linewidth, which is beneficial for comprehensively improving the bandwidth and insertion loss characteristics of circulators. Specifically:

[0035] (1) High saturation magnetization (4πM) s (3.8~4.2kGs), which can meet the engineering requirements for widening the bandwidth of microwave devices;

[0036] (2) High remanence ratio (M r / M s (0.65~0.75) and coercivity (H) c(450~550 Oe), which can cause the magnetic moment to precess in a strongly anisotropic direction, forming a built-in field, completely freeing it from the constraints of external magnets, and achieving small size and lightweight;

[0037] (3) High and adjustable anisotropic field (H a (10.0~12.0kOe), which can meet the engineering requirements for controlling the operating frequency band of microwave devices;

[0038] (4) The low ferromagnetic resonance linewidth (ΔH: 240~280Oe) can meet the engineering requirements of low insertion loss in microwave devices. Attached Figure Description

[0039] Figure 1 The X-ray diffraction patterns are of the self-biased hexagonal ferrite materials in Examples 1-3 and the comparative examples of this invention.

[0040] Figure 2 This is a scanning electron microscope image of pure BaM hexagonal ferrite material in the comparative example.

[0041] Figure 3 BaCr in Embodiment 1 of the present invention 0.6 Fe 10.6 O 19-δ Scanning electron microscope image of self-biased hexagonal ferrite material.

[0042] Figure 4 BaCr in Embodiment 2 of the present invention 0.7 Fe 10.5 O 19-δ Scanning electron microscope image of self-biased hexagonal ferrite material.

[0043] Figure 5 BaCr in Embodiment 3 of the present invention 0.8 Fe 10.4 O 19-δ Scanning electron microscope image of self-biased hexagonal ferrite material. Detailed Implementation

[0044] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0045] The present invention provides a Cr-substituted X-band self-biased hexagonal ferrite material and a preparation method thereof. By substituting Fe in BaM ferrite with non-magnetic ion Cr, the anisotropy field of BaM ferrite is effectively regulated while reducing the anisotropy broadening, so that the anisotropy field of BaM ferrite is reduced to 10.0 - 12.0 kOe, thus being applicable to the X band. At the same time, the self-biased hexagonal ferrite has a high saturation magnetization intensity, a high remanence ratio and coercivity, and a low ferromagnetic resonance linewidth, which is conducive to comprehensively improving the bandwidth and insertion loss characteristics of the circulator.

[0046] Based on this, the present invention provides three examples and one comparative example, specifically Example 1 - Example 3 and Comparative Example 1. Among them, the self-biased hexagonal ferrite material is prepared by the following steps:

[0047] Step 1:配料;

[0048] According to the chemical formula BaCr x Fe 11.2-x O 19-δ (0<x≤1.2), calculate and weigh the raw material powders of 99.5% BaCO3, 99.5% Cr2O3, and 99.3% Fe2O3. The formula of each raw material powder in Comparative Example 1 and Examples 1 - 3 is shown in Table 1;

[0049] Table 1 Raw material formula

[0050]

[0051] 步骤2、一次球磨;

[0052] Perform primary ball milling on the mixture obtained in Step 1 for 12 hours, then dry and screen to obtain the primary ball-milled material;

[0053] 步骤3、预烧;

[0054] Place the sieved primary ball-milled material in an air atmosphere for pre-sintering at a pre-sintering temperature of 1250 °C, a holding time of 2 h, and a heating rate of 2 °C / min to obtain the BaM hexagonal ferrite pre-sintered material;

[0055] 步骤4、掺杂;

[0056] Based on the mass of the pre-sintered material obtained in Step 3, add 1.0 wt% SiO2, 0.5 wt% Bi2O3, and 1.5 wt% CaCO3 to obtain the doped mixed powder;

[0057] 步骤5、二次球磨;

[0058] Perform secondary ball milling on the doped mixed powder for 18 hours, and the average particle size of the powder after ball milling is 1.0 μm to obtain the secondary ball-milled slurry;

[0059] Step 6: Shaping;

[0060] The slurry obtained in step 5 is dehydrated to control the water content of the slurry at 4.5 wt%. Then, the dehydrated slurry is pressed into a green body under a magnetic field forming press. The forming magnetic field strength is 0.8 T, the forming pressure is 100 MPa, and the holding time is 100 s.

[0061] Step 7: Multi-step atmosphere sintering

[0062] The green billet obtained in step 6 is placed in a controlled atmosphere resistance furnace, and the furnace temperature is raised from room temperature to 950°C to accelerate the removal of moisture from the green billet and inhibit cracking of the green billet; wherein the heating rate is 1°C / min.

[0063] Then the furnace temperature is continuously increased to 1280℃ to allow the additives to be uniformly enriched at the grain boundaries and fully encapsulate the grains; the heating rate is 2 ℃ / min.

[0064] After heating to 1280℃, it was held in an oxygen atmosphere of 0.05MPa for 15 hours to reduce Fe. 2+ This process generates and eliminates closed pores, resulting in uniform and dense grains.

[0065] The samples prepared in the above steps were analyzed for phase composition using X-ray diffraction; their microstructure was observed using scanning electron microscopy; and their 4πM magnetometer was measured using a LakeShore 8604 vibrating sample magnetometer. s 4πM r H c The CK-XW-100 high-frequency integrated measurement system was used to measure ΔH, and the anisotropic field H was measured. a It is derived from Kittel's formula.

[0066] Tests showed that the 4πM of Comparative Example 1 and Examples 1-3... s M r / M s H c H a The values ​​of ΔH, porosity P, and average grain size D are shown in Table 2.

[0067] Table 2 Test Results

[0068]

[0069] Furthermore, such as Figure 1 The figures show the X-ray diffraction patterns of the self-biased hexagonal ferrite materials in Examples 1-3 and the comparative example of this invention. As can be seen from the figures, the diffraction peaks of Examples 1-3 and the comparative example match well with the standard cards, and no impurity phases are generated. Figure 2The image shown is a scanning electron microscope image of pure BaM hexagonal ferrite material in the comparative example, as shown below. Figure 3 The image shown is of BaCr in Example 1. 0.6 Fe 10.6 O 19-δ Scanning electron microscope images of self-biased hexagonal ferrite materials, such as Figure 4 The image shows BaCr in Example 2. 0.7 Fe 10.5 O 19-δ Scanning electron microscope images of self-biased hexagonal ferrite materials, such as Figure 5 The image shown is of BaCr in Example 3. 0.8 Fe 10.4 O 19-δ Scanning electron microscope images of self-biased hexagonal ferrite materials show that, as the Cr substitution amount increases, the average grain size decreases while the porosity decreases.

[0070] In summary, this invention, based on BaM hexagonal ferrite, employs a non-magnetic Cr substitution and an iron-deficient formulation in the main composition to prepare a BaM hexagonal gyromagnetic ferrite material suitable for X-band self-biased circulators. Its material specifications are: saturation magnetization 4πM. s 3.8~4.2kGs, remanence ratio M r / M s : 0.65~0.75, coercivity H c 450~550 Oe, anisotropic field H a The remanence ratio is 10.0~12.0 kOe, and the ferromagnetic resonance linewidth ΔH is 240~280 Oe. This material provides a material basis for designing miniaturized self-biased circulators in the X-band. Furthermore, the larger remanence ratio and narrow ferromagnetic resonance linewidth improve the circulator bandwidth and insertion loss characteristics.

[0071] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A Cr-substituted X-band self-biased hexagonal gyromagnetic ferrite material, characterized in that, include: BaM hexagonal ferrite and additives, wherein the chemical formula of the BaM hexagonal ferrite is BaCr x Fe 11.2-x O 19-δ , 0 < x ≤ 1.2; based on the mass of the BaM hexagonal ferrite pre-sintered material, the additives include: 0.1 wt% to 1.5 wt% of SiO2, 0.1 wt% to 1.5 wt% of Bi2O3, and 0.1 wt% to 2.0 wt% of CaCO3.

2. The X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 1, characterized in that, The anisotropic field H of the X-band self-biased hexagonal gyromagnetic ferrite material a It ranges from 10.0 kOe to 12.0 kOe.

3. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 1, characterized in that, Includes the following steps: Step 1. Using BaCO3, Cr2O3, and Fe2O3 as raw materials, weigh them according to the chemical formula BaCr x Fe 11.2-x O 19-δ , where 0 < x ≤ 1.2 Step 2: The ingredients obtained in Step 1 are ball-milled once, then dried and sieved to obtain primary ball-milled material; Step 3: Place the sieved primary ball milling material in an air atmosphere for pre-firing. The pre-firing temperature is 1000℃~1280℃, the holding time is 1 h~4h, and the heating rate is 1℃ / min~3℃ / min to obtain BaM hexagonal ferrite pre-fired material. Step 4: Based on the mass of the pre-burned material obtained in Step 3, add SiO2, Bi2O3 and CaCO3 as additives to obtain the doped mixed powder. Step 5: The mixed powder obtained by doping is subjected to secondary ball milling. The average particle size of the powder after ball milling is 0.6μm to 1.4μm, and a secondary ball milling slurry is obtained. Step 6: Dehydrate the slurry obtained in Step 5, and press the dehydrated slurry into a green body under a magnetic field forming press. Step 7: Perform multi-stage atmosphere sintering on the green body obtained in Step 6; Placed in a controlled atmosphere resistance furnace, the furnace temperature is raised from room temperature to 950℃ at a rate of 0.5℃ / min to 2℃ / min. The temperature inside the furnace is continuously raised to 1200℃~1400℃, with a heating rate of 1℃ / min~3℃ / min; By holding the material in an oxygen atmosphere of 0.03 MPa to 0.06 MPa for 6 to 15 hours, a Cr-substituted X-band self-biased hexagonal gyromagnetic ferrite material was obtained.

4. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 3, characterized in that, In step 4, the proportions of the additives are as follows: based on the mass of the BaM hexagonal ferrite pre-sintered material, SiO2: 0.1 wt%~1.5 wt%, Bi2O3: 0.1 wt%~1.5 wt%, CaCO3: 0.1 wt%~2.0 wt%.

5. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 3, characterized in that, In step 2, the ball milling time is 10 to 15 hours.

6. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 3, characterized in that, In step 5, the ball milling time is 12 to 24 hours.

7. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 3, characterized in that, In step 6, the moisture content of the slurry after dewatering is controlled between 4.0 wt% and 5.0 wt%.

8. The method for preparing X-band self-biased hexagonal gyromagnetic ferrite material based on Cr substitution according to claim 3, characterized in that, In step 6, the parameters for pressing the green body are: the forming magnetic field strength is 0.6T~1.0T, the forming pressure is 80 MPa~120MPa, and the holding time is 70~120s.

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