High-power low-loss li-based microwave ferrite for ltcc and preparation method thereof

Abstract

This invention relates to a high-power, low-loss Li-based microwave ferrite for LTCC and its preparation method, belonging to the field of electronic ceramics technology. The ferrite, based on its respective standard components, contains the following content: Li₂CO₃ 11.80–12.24 mol%, ZnO 19.87–20.41 mol%, TiO₂ 10.78–11.08 mol%, Mn₃O₄ 0.39–2.65 mol%, Co₃O₄ 0.04–0.58 mol%, Fe₂O₃ 54.70–56.18 mol%, and Bi₂O₃ 0.09 mol%. This invention introduces high-valence Mn ions into the Li-based microwave ferrite, altering the ferrite grain size distribution, particularly increasing the proportion of fine grains, thus improving the spin linewidth. Based on grain refinement, the introduction of an appropriate amount of Co ions with rapid relaxation characteristics further enhances the ferrite's spin linewidth.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramics technology, specifically relating to a high-power, low-loss Li-based microwave ferrite for LTCC and its preparation method. Background Technology

[0002] As phased array radar systems develop towards miniaturization, integration, and multifunctionality, key components such as phase shifters require lower insertion loss, higher peak power, and faster response speeds. Li-based ferrites, due to their high rectangularity and high saturation magnetization (4πM), are ideal for this purpose. s ), high Curie temperature (T) c Lithium-based ferrites are considered excellent candidate materials for microwave ferrite phase shifters due to their advantages such as low spin linewidth and low ferromagnetic resonance linewidth (ΔH). To meet the requirements of miniaturization and integration of microwave ferrite devices, current research on lithium-based ferrites mainly focuses on two aspects: 1) lowering the sintering temperature of ferrites to around 900℃ by introducing additives such as low-melting-point oxides and glass to achieve co-firing with silver electrodes; 2) improving the severe degradation of dielectric and magnetic losses in low-temperature sintered lithium-based ferrites through ion substitution. Furthermore, microwave ferrite devices for high-power applications require not only low electromagnetic losses but also high power handling capabilities. Therefore, simultaneously achieving optimal comprehensive performance in terms of spin linewidth, dielectric loss, and magnetic loss of Li-based ferrite materials under low-temperature sintering conditions is an urgent problem to be solved.

[0003] Patent application number 202010379833.9 discloses a high-power gyroscope ferrite material for the Ku band and its preparation method. This invention modifies Zn... 2+ and Ti 4+ The amount of substitution of ions in Li-based ferrites, supplemented with Bi₂O₃, V₂O₅ and other additives, was used to obtain the spin wave linewidth ΔH of the samples under sintering conditions at 1000℃. k The maximum value is ~3.88 Oe, the ferromagnetic resonance linewidth ΔH is as low as ~298 Oe, and the dielectric loss tangent is tanδ. ε As low as ~5.7×10 -4 The material produced by this invention has a high sintering temperature, making it incompatible with LTCC technology, and the spin wave linewidth ΔH is also limited. k The values ​​are too low, and the microwave magnetic loss ΔH is too high. Patent application number 202110372118.7 discloses a narrow-linewidth LTCF gyromagnetic substrate material and its preparation method. This invention modifies the Zn content in Li-based ferrites... 2+ Ti 4+By supplementing the ion substitution with B2O3-ZnO-Bi2O3 (BZB) glass additive and Bi2O3 oxide, a ferrite sample with ΔH of ~90Oe was obtained under sintering conditions of 900℃, but its tanδ ε Gundam ~6.5×10 -4 It cannot simultaneously achieve low magnetic loss and low dielectric loss, and no ΔH was observed. k Parameters. Patent application number 201811483879.4 discloses a spinel Li-based ferrite material for X-band to millimeter-wave band locked phase shifters, the method using Zn... 2+ Ti 4+ Mg 2+ Cu 2+ Co 2+ Bi 3+ and Mn 2+ Plasma-substituted Li-based ferrites were sintered at 980 °C to obtain the spin wave linewidth ΔH of the samples. k High up to ~10.0 Oe, ferromagnetic resonance linewidth ΔH as low as ~145 Oe, dielectric loss tangent tanδ ε As low as ~2.3×10 -4 However, there is room for further optimization of its sintering temperature and spin wave linewidth. The article "Effect of Bi2O3 contents on magnetic and electromagnetic properties of LiZnMn ferriteceramics[J], Eur.Ceram.Soc.42(2022)3463–3472" states that by adding Bi2O3 as an additive, low magnetic loss (ΔH=~158Oe) and low dielectric loss (tanδ) were obtained by sintering at 1075℃. ε =~5.49×10 -4 However, its spin linewidth is only ~1.87 Oe. The article "Low-temperature sintering and ferrimagnetic properties of LiZnTiMnferrites with Bi2O3–Nb2O5 eutectic mixture[J], J.Mater.Sci.Mater.Electron.33(2022)20162–20169" added Bi2O3–Nb2O5 composite additives and achieved low magnetic loss (ΔH=~161Oe) under sintering conditions of 920℃, but no reports were found on dielectric loss tangent and spin linewidth parameters.

[0004] In summary, none of the above patents and articles have achieved both high spin linewidth and low microwave loss in Li-based ferrite materials under low-temperature sintering conditions (≤900℃). Given the requirements of high power handling capacity and low electromagnetic loss for microwave ferrite devices in LTCC integration technology, a better solution is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing LTCC microwave ferrite devices cannot simultaneously achieve high power handling capability and low electromagnetic loss, and to propose a high-power, low-loss Li-based microwave ferrite for LTCC and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A high-power, low-loss Li-based microwave ferrite for LTCC, wherein the Li-based microwave ferrite has the following content based on its respective standard: Li₂CO₃ 11.80–12.24 mol%, ZnO 19.87–20.41 mol%, TiO₂ 10.78–11.08 mol%, Mn₃O₄ 0.39–2.65 mol%, Co₃O₄ 0.04–0.58 mol%, Fe₂O₃ 54.70–56.18 mol%, and Bi₂O₃ 0.09 mol.

[0008] A method for preparing high-power, low-loss Li-based microwave ferrite for LTCC includes the following steps:

[0009] Step 1, Weighing:

[0010] Using analytically pure lithium carbonate (Li2CO3), zinc oxide (ZnO), titanium oxide (TiO2), manganese tetroxide (Mn3O4), cobalt tetroxide (Co3O4), iron oxide (Fe2O3), and bismuth oxide (Bi2O3) as raw materials, the following contents were weighed according to their respective standards: Li2CO3 11.80–12.24 mol%, ZnO 19.87–20.41 mol%, TiO2 10.78–11.08 mol%, Mn3O4 0.39–2.65 mol%, Co3O4 0.04–0.58 mol%, Fe2O3 54.70–56.18 mol%, and Bi2O3 0.09 mol%.

[0011] Step 2, First ball milling:

[0012] Add the raw material weighed in step 1 to a planetary ball mill for one ball milling. The dispersant is deionized water. The mass ratio of raw material to deionized water is 1:1.5. The ball mill speed is 250 r / min and the ball milling time is 4 h.

[0013] Step 3, Preheating:

[0014] After drying and sieving the ball mill slurry obtained in step 2, it is placed in an alumina crucible and pre-calcined in an oxygen atmosphere at 750℃~850℃ for 2h~3h. After completion, it is cooled to room temperature with the furnace and taken out to obtain Li-based microwave ferrite pre-calcined material.

[0015] Step 4, Secondary ball milling:

[0016] The Li-based microwave ferrite pre-calcined material obtained in step 3 and deionized water were added to a planetary ball mill for secondary ball milling. The mass ratio of pre-calcined material to deionized water was 1:1.3, the ball mill speed was 250 r / min, and the ball milling time was 6 h. After the ball milling was completed, the slurry was dried.

[0017] Step 5, Shaping:

[0018] After sieving the secondary ball milling material obtained in step 4, add 8-12 wt.% of polyvinyl alcohol (PVA) binder equivalent to the powder mass to granulate, and then press it into a ring-shaped green sample using a hydraulic press.

[0019] Step 6, Sintering:

[0020] The green sample obtained in step 5 is placed in a sintering furnace and heated to 600°C at a rate of 1°C / min, and held for 1-2 hours to remove the binder; then, the temperature is increased to the sintering temperature of 880-890°C at a rate of 1°C / min, and held for 2-3 hours; after sintering, the temperature is reduced to 600°C at a rate of 1°C / min; finally, the sample is allowed to cool naturally to room temperature with the furnace to obtain Li-based microwave ferrite.

[0021] This invention provides a high-power, low-loss Li-based microwave ferrite for LTCC. First, Zn is selected. 2+ -Ti 4+ -Bi 3 + Ion-substituted Li-based microwave ferrite iron-deficient formulation, Zn 2+ Ti 4+ The combined introduction of ions, besides altering the magnetic moment difference at the AB sites of the sublattice and the superexchange effect, and regulating the saturation magnetization and Curie temperature of the ferrite, also helps to enhance densification and reduce the magnetocrystalline anisotropy constant of the ferrite, thereby reducing porosity and linewidth caused by magnetocrystalline anisotropy; while an appropriate amount of Bi 3+ Ion substitution effectively reduced the sintering temperature and microwave magnetic loss of ferrite. Secondly, the combined approach of introducing high-valence Mn and high-valence Co ions effectively suppressed Fe... 2+ The generation of Co ions reduces dielectric loss; however, Co ions, due to their large positive magnetocrystalline anisotropy constant, increase the ferromagnetic resonance linewidth, while Mn tends to occupy the central A sites of the tetrahedron.2+ Ions and Mn that tend to occupy the central B site of the octahedron 3+ When ions are introduced, the superexchange effect at the AB sites weakens, thus reducing magnetic loss. Therefore, the low dielectric loss of the microwave ferrite is maintained without increasing the ferromagnetic resonance linewidth. Furthermore, the Mn in manganese tetroxide (Mn3O4)... 2+ / Mn 3+ The addition of ions leads to the precipitation of bismuth ferrite, resulting in ferrite grain refinement and shortening the spin wave transit time; based on this, Co from cobalt tetroxide (Co3O4), which has rapid relaxation characteristics, is introduced. 2+ / Co 3+ Ions further enhance the spin wave linewidth.

[0022] The technical specifications of the Li-based microwave ferrite prepared by this invention are as follows:

[0023] Sintering temperature: ~880℃;

[0024] Apparent density ρ: >4.7 g / cm³ 3 ;

[0025] Saturation magnetization 4πM s 3900Gs±3%;

[0026] Ferromagnetic resonance linewidth ΔH: <120 Oe;

[0027] Spin waveline width ΔH k >10Oe;

[0028] Dielectric loss tangent tanδ ε <3×10 -4 ;

[0029] Rectangularity R: ≥0.85;

[0030] Curie temperature T c >300℃;

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. This invention introduces high-valence Mn ions into Li-based microwave ferrites, altering the ferrite grain size distribution. In particular, the increased proportion of fine grains leads to a greater spin wave linewidth ΔH. k Enhancement: Based on grain refinement, the introduction of an appropriate amount of Co ions with rapid relaxation characteristics further enhances the spin wave linewidth ΔH of the ferrite. k .

[0033] 2. This invention considers iron-deficient formulations in material structure design and adds high-valence metal oxides Mn3O4 and Co3O4 to the raw materials. At the same time, it adopts comprehensive measures such as oxygen atmosphere treatment during the pre-calcination process, thereby significantly reducing the microwave dielectric and magnetic losses of ferrite.

[0034] 3. The high-power, low-loss Li-based microwave ferrite for LTCC prepared by this invention, in addition to having a relatively low sintering temperature (~880℃), also possesses excellent electromagnetic properties: a high spin linewidth (ΔH). k >10Oe), low dielectric loss (tanδ) ε <3×10 -4 Low magnetic loss (ΔH < 120 Oe), high saturation magnetization (4π M). s =3900Gs±3%), high density (ρ>4.7g / cm³) 3 ), and high Curie temperature (T c >300℃). The high-power, low-loss Li-based microwave ferrite material obtained not only meets the requirements of LTCC process, but also possesses the good electromagnetic properties of key substrate materials required for high-power microwave ferrite devices. Attached Figure Description

[0035] Figure 1 The XRD patterns of the ferrites obtained in comparative examples, Example 1, and Example 8 are shown.

[0036] Figure 2 SEM images of Li-based microwave ferrite samples obtained in Comparative Example (a) and Example 1 (b). Detailed Implementation

[0037] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] A method for preparing high-power, low-loss Li-based microwave ferrite for LTCC includes the following steps:

[0040] Step 1, Weighing:

[0041] Using analytically pure lithium carbonate (Li2CO3), zinc oxide (ZnO), titanium oxide (TiO2), manganese tetroxide (Mn3O4), iron oxide (Fe2O3), and bismuth oxide (Bi2O3) as raw materials, the contents of each raw material were calculated and weighed according to their respective standards: Li2CO3 12.06 mol%, ZnO2 0.09 mol%, TiO2 10.91 mol%, Mn3O4 1.53 mol%, Fe2O3 55.32 mol%, and Bi2O3 0.09 mol%.

[0042] Step 2, First ball milling:

[0043] Add the raw material weighed in step 1 to a planetary ball mill for one ball milling. The dispersant is deionized water. The mass ratio of raw material to deionized water is 1:1.5. The ball mill speed is 250 r / min and the ball milling time is 4 h.

[0044] Step 3, Preheating:

[0045] After drying and sieving the ball mill slurry obtained in step 2, it is placed in an alumina crucible and pre-calcined in an oxygen atmosphere at 800℃ (oxygen partial pressure 0.3MPa, oxygen flow rate 300~400mL / min) for 2 hours. After completion, it is cooled to room temperature with the furnace and taken out to obtain Li-based microwave ferrite pre-calcined material.

[0046] Step 4, Secondary ball milling:

[0047] The Li-based microwave ferrite pre-calcined material obtained in step 3 and deionized water were added to a planetary ball mill for secondary ball milling. The mass ratio of pre-calcined material to deionized water was 1:1.3, the ball mill speed was 250 r / min, and the ball milling time was 6 h. After the ball milling was completed, the slurry was dried.

[0048] Step 5, Shaping:

[0049] After sieving the secondary ball milling material obtained in step 4, add 10 wt.% of polyvinyl alcohol (PVA) binder equivalent to the powder mass to granulate, and then press it into a ring-shaped green sample using a hydraulic press.

[0050] Step 6, Sintering:

[0051] The green sample obtained in step 5 was placed in a sintering furnace and heated to 600°C at a rate of 1°C / min, and held for 2 hours to remove the binder. Then, the temperature was increased to 880°C at a rate of 1°C / min and held for 2 hours. After sintering, the temperature was reduced to 600°C at a rate of 1°C / min. Finally, the sample was allowed to cool naturally to room temperature with the furnace to obtain Li-based microwave ferrite.

[0052] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 1 has the following properties: apparent density ρ is 4.76 g / cm³. 3 saturation magnetization 4πM s The value is 3882 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 88 Oe, and the spin wave linewidth ΔH k The dielectric constant ε (@9.3GHz) is 14.1 Oe, the dielectric loss tangent tanδ is 14.90, and the dielectric loss angle is positive (tanδ). ε (@9.3GHz) is 2.59×10 -4 Curie temperature Tc The temperature is 308℃, and the rectangularity R is 0.90.

[0053] Example 2

[0054] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.17mol%, ZnO2 0.33mol%, TiO2 11.04mol%, Mn3O4 0.39mol%, Co3O4 0.04mol%, Fe2O3 55.94mol%, and Bi2O3 0.09mol%. The remaining steps are the same as in Example 1.

[0055] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 2 has the following properties: apparent density ρ is 4.74 g / cm³. 3 saturation magnetization 4πM s The value is 3970 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 95 Oe, and the spin wave linewidth ΔH k The dielectric constant is 11.8 Oe, the dielectric constant ε' (@9.3 GHz) is 15.11, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.03×10 -4 Curie temperature T c The temperature is 310℃, and the rectangularity R is 0.88.

[0056] Example 3

[0057] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.14mol%, ZnO2 0.34mol%, TiO2 11.04mol%, Mn3O4 0.39mol%, Co3O4 0.08mol%, Fe2O3 55.92mol%, and Bi2O3 0.09mol%. The remaining steps are the same as in Example 1.

[0058] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 3 has the following properties: apparent density ρ is 4.74 g / cm³. 3 saturation magnetization 4πM s The value is 3977 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 99 Oe, and the spin wave linewidth ΔH k The dielectric constant is 14.3 Oe, the dielectric constant ε' (@9.3 GHz) is 15.03, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.07×10 -4 Curie temperature T c The temperature is 310℃, and the rectangularity R is 0.85.

[0059] Example 4

[0060] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.12mol%, ZnO2 0.34mol%, TiO2 11.04mol%, Mn3O4 0.39mol%, Co3O4 0.12mol%, Fe2O3 55.9mol%, and Bi2O3 0.09mol%. The remaining steps are the same as in Example 1.

[0061] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 4 has the following properties: apparent density ρ is 4.74 g / cm³. 3 saturation magnetization 4πM s The value is 3990 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 105 Oe, and the spin wave linewidth ΔH k The dielectric constant is 19.5 Oe, the dielectric constant ε' (@9.3 GHz) is 15.07, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.24×10 -4 Curie temperature T c The temperature is 311℃, and the rectangularity R is 0.89.

[0062] Example 5

[0063] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.09 mol%, ZnO2 0.34 mol%, TiO2 11.04 mol%, Mn3O4 0.39 mol%, Co3O4 0.16 mol%, Fe2O3 55.89 mol%, and Bi2O3 0.09 mol%. The remaining steps are the same as in Example 1.

[0064] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 5 has the following properties: apparent density ρ is 4.75 g / cm³. 3 saturation magnetization 4πM s The value is 3973 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 104 Oe, and the spin wave linewidth ΔH k The dielectric constant is 23.7 Oe, the dielectric constant ε' (@9.3 GHz) is 15.13, and the dielectric loss tangent tanδ is... ε (@9.3GHz) is 1.14×10 -4 Curie temperature T c The temperature is 311℃, and the rectangularity R is 0.89.

[0065] Example 6

[0066] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.06mol%, ZnO2 0.35mol%, TiO2 11.05mol%, Mn3O4 0.39mol%, Co3O4 0.19mol%, Fe2O3 55.87mol%, and Bi2O3 0.09mol%. The remaining steps are the same as in Example 1.

[0067] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 6 has the following properties: apparent density ρ is 4.75 g / cm³. 3 saturation magnetization 4πM s The value is 3955 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 105 Oe, and the spin wave linewidth ΔH k The dielectric constant is 25.4 Oe, the dielectric constant ε' (@9.3 GHz) is 15.08, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.17×10 -4 Curie temperature T c The temperature is 310℃, and the rectangularity R is 0.87.

[0068] Example 7

[0069] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.04mol%, ZnO2 0.35mol%, TiO2 11.05mol%, Mn3O4 0.39mol%, Co3O4 0.23mol%, Fe2O3 55.85mol%, and Bi2O3 0.09mol%. The remaining steps are the same as in Example 1.

[0070] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 7 has the following properties: apparent density ρ is 4.75 g / cm³. 3 saturation magnetization 4πM s The value is 3926 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 107 Oe, and the spin wave linewidth ΔH k The dielectric constant is 22.1 Oe, the dielectric constant ε' (@9.3 GHz) is 15.17, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.26×10 -4 Curie temperature T c The temperature is 310℃, and the rectangularity R is 0.89.

[0071] Example 8

[0072] The difference between this embodiment and Example 1 is that in step 1, the raw materials are calculated and weighed according to the following percentages: Li2CO3 12.01 mol%, ZnO2 0.35 mol%, TiO2 11.05 mol%, Mn3O4 0.39 mol%, Co3O4 0.27 mol%, Fe2O3 55.84 mol%, and Bi2O3 0.09 mol%. The remaining steps are the same as in Example 1.

[0073] The high-power, low-loss Li-based microwave ferrite for LTCC prepared in Example 8 has the following properties: apparent density ρ is 4.74 g / cm³. 3 saturation magnetization 4πM s The value is 3901 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 110 Oe, and the spin wave linewidth ΔH k The dielectric constant is 33.2 Oe, the dielectric constant ε' (@9.3 GHz) is 15.18, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.37×10 -4 Curie temperature T c The temperature is 310℃, and the rectangularity R is 0.88.

[0074] Comparative Example

[0075] Compared with Example 1, the comparative example differs in that: in step 1, the raw materials were calculated and weighed according to Li2CO3 12.24mol%, ZnO2 0.41mol%, TiO2 11.08mol%, Fe2O3 56.18mol%, and Bi2O3 0.09mol%, while the remaining steps were the same as in Example 1.

[0076] The properties of the Li-based microwave ferrite prepared in the comparative example are as follows: apparent density ρ is 4.77 g / cm³. 3 saturation magnetization 4πM s The value is 4022 Gs, the ferromagnetic resonance linewidth ΔH (@9.3 GHz) is 127 Oe, and the spin wave linewidth ΔH k The dielectric constant is 8.3 Oe, the dielectric constant ε' (@9.3 GHz) is 15.29, and the dielectric loss tangent is tanδ. ε (@9.3GHz) is 1.53×10 -4 Curie temperature T c The temperature is 317℃, and the rectangularity R is 0.87.

[0077] Figure 1 The XRD patterns of the ferrites obtained in comparative examples, Example 1, and Example 8 are shown. Figure 2SEM images of the cross-sections of the Li-based microwave ferrite samples obtained in Comparative Example (a) and Example 1 (b) are shown. Table 1 shows the performance parameters of the examples and comparative examples. In the Fe-deficient Li-based ferrite, the grain size distribution was changed by trace Mn substitution, increasing the proportion of fine grains (≤1.0 μm) and resulting in a higher spin wave linewidth ΔH. k Significant improvements were achieved, and based on this, the introduction of Co ions with rapid relaxation characteristics further enhanced the spin linewidth ΔH of the microwave ferrite. k Meanwhile, the addition of trace amounts of high-valence Mn and high-valence Co helps to reduce Fe in ferrite. 2+ The addition of Mn reduces microwave dielectric loss. Furthermore, the Mn content weakens the superexchange effect at the AB sites of the spinel ferrite, resulting in magnetocrystalline anisotropy and increased linewidth ΔH. a This reduces and narrows the overall ferromagnetic resonance linewidth ΔH.

[0078] Table 1

[0079]

Claims

1. A method for preparing high-power, low-loss Li-based microwave ferrite for LTCC, characterized in that, Includes the following steps: Step 1, Weighing: Using Li2CO3, ZnO, TiO2, Mn3O4, Co3O4, Fe2O3, and Bi2O3 as raw materials, the contents of each raw material, calculated according to their respective standards, were as follows: Li2CO3 11.80~12.24 mol%, ZnO 19.87~20.41 mol%, TiO2 10.78~11.08 mol%, Mn3O4 0.39~2.65 mol%, Co3O4 0.04~0.58 mol%, Fe2O3 54.70~56.18 mol%, and Bi2O3 0.09 mol%. Step 2, First ball milling: The raw materials weighed in step 1 are subjected to ball milling once. The ball mill speed is 250 r / min and the ball milling time is 4 h. Step 3, Preheating: After drying and sieving the ball mill slurry obtained in step 2, it is pre-calcined in an oxygen atmosphere at 750℃~850℃ for 2h~3h. After completion, it is cooled to room temperature in the furnace and taken out to obtain Li-based microwave ferrite pre-calcined material. Step 4, Secondary ball milling: The Li-based microwave ferrite pre-calcined material obtained in step 3 was subjected to secondary ball milling at a speed of 250 r / min for 6 h. After ball milling, the slurry was dried. Step 5, Shaping: After sieving the secondary ball milling material obtained in step 4, polyvinyl alcohol binder was added for granulation, and then the material was pressed into a green sample using a hydraulic press. Step 6, Sintering: The green sample obtained in step 5 is placed in a sintering furnace and heated to 600℃. It is held at this temperature for 1-2 hours to remove the binder. Then, the temperature is raised to the sintering temperature of 880℃ and held for 2-3 hours. After sintering, the temperature is lowered to 600℃. Finally, the sample is allowed to cool naturally to room temperature with the furnace to obtain Li-based microwave ferrite.

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