A low-loss microwave ferrite material for LTCF phase shifters and its preparation method

Abstract

This invention relates to a low-loss microwave ferrite material for LTCF phase shifters and its preparation method, belonging to the field of electronic ceramic materials technology. The microwave ferrite material comprises a main material and auxiliary materials, with the auxiliary materials accounting for 0.01–2 wt.% of the main material. The main material consists of: Li₂CO₃ 11.65–12.33 mol%, ZnO 17.61–22.18 mol%, TiO₂ 8.22–13.31 mol.%, Mn₃O₄ 1.85–1.96 mol%, Fe₂O₃ 50.93–59.79 mol%, and Bi₂O₃ 0.08–0.09 mol%. The auxiliary material is rutile or anatase TiO₂ with a particle size of 5 nm–50 nm. The low-loss microwave ferrite material for LTCF phase shifters prepared by this invention, in addition to having a low sintering temperature (≤910℃), also has a narrow ferromagnetic resonance linewidth (≤90Oe) and low dielectric loss (<3×10⁻⁶). ‑4 It possesses high saturation magnetization (>3700 Gauss), high remanence ratio (>0.85), and high Curie temperature (>300℃). The fabricated microwave ferrite not only meets the requirements of LTCF process but also possesses excellent magnetic properties required for key substrate materials in microwave devices such as low-loss phase shifters.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic materials technology, specifically relating to a microwave ferrite material for LTCF phase shifters with low loss, high saturation magnetization and high remanence ratio, and its preparation method. Background Technology

[0002] Due to its advantages such as wide adjustable saturation magnetization range, high remanence ratio, narrow ferromagnetic resonance linewidth, and low dielectric loss at room temperature, LiZn ferrite is widely used as a substrate material for microwave ferrite phase shifters. With the development of phased array radar technology, the key component—the phase shifter—needs to evolve towards low loss, miniaturization, and integration. Low-temperature co-fired ferrite (LTCF) technology provides an effective solution for the miniaturization and integration of microwave ferrite devices. However, previously, LTCF LiZn ferrites often struggled to achieve narrow ferromagnetic resonance linewidths and low dielectric losses due to the presence of numerous pores and insufficient grain growth. High ferromagnetic resonance linewidths and dielectric losses lead to excessive insertion and return losses, as well as severe heat generation in microwave ferrite devices. Therefore, achieving a low-temperature sintering process compatible with LTCF technology while maintaining low microwave loss and other magnetic properties is an urgent problem to be solved.

[0003] Currently, research on the low-temperature sintering and magnetic properties of LiZn microwave ferrites mainly focuses on ion substitution and low-melting-point oxide or glass doping modification. Patent application number 202110324931.7 discloses a low-temperature sintering LiZn ferrite material with high saturation magnetization and its preparation method. This invention utilizes Zr... 4+ Ion partial substitution of Zn in LiZn ferrite 2+The sample prepared by this method, with the addition of Bi2O3 as a sintering aid and sintered at 925℃, yielded a ferromagnetic resonance linewidth of 205 Oe and a specific saturation magnetization of 102.4 emu / g. However, the ferromagnetic resonance linewidth of the material prepared by this method is too large, and no dielectric loss has been reported. "R. Wang, T. Zhou, Z. Zhong. Low-temperature processing of LiZn-based ferriteceramics by co-doping of V2O5 and Sb2O3: Composition, microstructure and magnetic properties[J]. Journal of Materials Science & Technology, 2022, 99: 1–8." This article describes how to achieve a LiZn ferrite with a ferromagnetic resonance linewidth of 153.8 Oe@9.5 GHz, a specific saturation magnetization of 82.51 emu / g, and a remanence ratio of 0.85 by co-doping with V2O5 and Sb2O3 and sintering at 920℃. The sample prepared by this method has a large ferromagnetic resonance linewidth, and no dielectric loss has been reported. "X. Wang, Z. Zhong, Z. Chen, et al. Effects of B2O3–Li2CO3–SiO2–ZnOglass on properties of Li 0.43 Zn 0.27 Ti 0.13 Fe 2.17 O4 ferrites sintered at low temperatures[J].Ceramics International,2020,46(5):5719–5724.” The article adds B2O3–Li2CO3–SiO2–ZnO glass, and obtains LiZnTi ferrite with a ferromagnetic resonance linewidth of 237Oe@9.3GHz and a specific saturation magnetization of 78.70 emu / g at 920℃. The ferromagnetic resonance linewidth of the sample prepared by this method is still too large, and the test results of dielectric loss are not reported. In summary, to meet the requirements of miniaturization, integration and high performance of LTCF phase shifters, a better solution is urgently needed to improve the comprehensive performance indicators of microwave ferrite substrates (narrow ferromagnetic resonance linewidth, low dielectric loss, high saturation magnetization, high remanence ratio, etc.). Summary of the Invention

[0004] The purpose of this invention is to address the problems of large ferromagnetic resonance linewidth and lack of research on dielectric loss characteristics in existing low-temperature sintered LiZn microwave ferrites, and to propose a low-loss microwave ferrite material for LTCF phase shifters and its preparation method.

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

[0006] A low-loss microwave ferrite material for LTCF phase shifters is prepared by low-temperature co-firing of the main material LiZn ferrite and the auxiliary material nano-TiO2. Firstly, the main material LiZn ferrite is selected from Zn... 2+ The iron-deficient formulation, characterized by heavy ion doping and Ti-Mn-Bi co-substitution, followed by pre-calcination in an oxygen atmosphere, results in materials with low microwave loss characteristics. Furthermore, the introduction of trace amounts of rutile or anatase nano-TiO2 further reduces microwave loss: some of the TiO2 entering the crystal lattice... 4+ The ions will replace the Fe at the B site of the LiZn ferrite. 3+ Ions, in order to maintain valence balance, a small amount of Fe 3+ The ions will transform into Fe. 2+ Ions, forming Fe 2+ -Ti 4+ -Fe 2+ Ion pairs. And Fe 2+ The positive magnetocrystalline anisotropy constant (K1) of the ions can compensate for the negative K1 of LiZn ferrite, reducing |K1| and the corresponding anisotropic broadening of the material, thereby reducing the ferromagnetic resonance linewidth. The remaining TiO2 nanoparticles dispersed between the grains can form a high-resistivity grain boundary layer, which is beneficial to reducing dielectric loss. The microwave ferrite material comprises a main material and an auxiliary material, with the auxiliary material accounting for 0.01–2 wt.% of the main material. The main material consists of the following components: Li₂CO₃ 11.65–12.33 mol%, ZnO 17.61–22.18 mol%, TiO₂ 8.22–13.31 mol.%, Mn₃O₄ 1.85–1.96 mol%, Fe₂O₃ 50.93–59.79 mol%, and Bi₂O₃ 0.08–0.09 mol%. The auxiliary material is rutile or anatase TiO₂ with a particle size of 5 nm–50 nm.

[0007] A method for preparing a low-loss microwave ferrite material for LTCF phase shifters includes the following steps:

[0008] Step 1, Pre-fired material preparation:

[0009] 1.1 Using analytically pure lithium carbonate (Li2CO3), zinc oxide (ZnO), titanium dioxide (TiO2), manganese tetroxide (Mn3O4), ferric oxide (Fe2O3), and bismuth trioxide (Bi2O3) as raw materials, the raw materials were weighed according to the following proportions: Li2CO3 11.65–12.33 mol%, ZnO 17.61–22.18 mol%, TiO2 8.22–13.31 mol%, Mn3O4 1.85–1.96 mol%, Fe2O3 50.93–59.79 mol%, and Bi2O3 0.08–0.09 mol%. The raw materials were then transferred to the stainless steel ball mill jar of a planetary ball mill and wet-milled for 3–5 hours to obtain a primary slurry.

[0010] 1.2 After drying and sieving the primary slurry obtained in step 1.1, pre-calcine it in an oxygen furnace at 780-820℃ for 1.5-2.5 hours. After cooling to room temperature in the furnace, remove it to obtain the pre-calcined main material.

[0011] Step 2, Secondary ball milling:

[0012] After sieving the main pre-calcined material obtained in step 1, add auxiliary materials equivalent to 0.01 to 2 wt.% of the main pre-calcined material mass. Put the resulting mixture into a planetary ball mill for secondary ball milling. After ball milling for 5 to 8 hours, a secondary slurry is obtained, which is then dried to obtain microwave ferrite abrasive.

[0013] Step 3: Shaping and sintering:

[0014] 3.1 After passing the microwave ferrite abrasive obtained in step 2 through an 80-mesh sieve, add 8-12 wt.% polyvinyl alcohol (PVA) binder equivalent to the powder mass to granulate, and then press it into a green sample using a hydraulic press.

[0015] 3.2 Place the green sample obtained in step 3.1 into a sintering furnace, heat it to 870-910℃ at a rate of 1-3℃ / min, hold it at that temperature for 2 hours, and allow it to cool naturally to room temperature after sintering to obtain the microwave ferrite material.

[0016] Furthermore, the excipient in step 2 is rutile or anatase TiO2 with a particle size of 5nm to 50nm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. Based on a formula with low loss, this invention introduces trace amounts of nano-TiO2 to further reduce microwave loss: a portion of the TiO2 that enters the crystal lattice... 4+ Ion-substituted Fe 3+ Ions, inducing Fe 2+ The formation of ions, Fe 2+The positive K1 of the ions can compensate for the negative K1 of LiZn ferrite, thereby reducing anisotropic broadening and obtaining a narrow ferromagnetic resonance linewidth. At the same time, the nano-TiO2 retained at the grain boundaries can form a high-resistivity layer, optimizing the dielectric properties of the material.

[0019] 2. In this invention, after employing nano-TiO2 doping, some Bi... 3+ Ions are Ti 4+ Ion substitution forms a small amount of bismuth iron oxide with a high Curie temperature, thus increasing the Curie temperature of the material.

[0020] 3. The low-loss microwave ferrite material for LTCF phase shifters prepared by this invention, in addition to having a low sintering temperature (≤910℃), also has a narrow ferromagnetic resonance linewidth (≤90Oe) and low dielectric loss (<3×10⁻⁶). -4 It possesses high saturation magnetization (>3700 Gauss), high remanence ratio (>0.85), and high Curie temperature (>300℃). The fabricated microwave ferrite not only meets the requirements of LTCF process but also possesses excellent magnetic properties required for key substrate materials in microwave devices such as low-loss phase shifters. Attached Figure Description

[0021] Figure 1 SEM images of the ferrite samples obtained in Comparative Example (a), Example 2 (b), and Example 6 (c). Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0023] A low-loss microwave ferrite material for LTCF phase shifters is proposed. Based on an iron-deficient formulation with Ti-Mn-Bi co-substitution, trace amounts of nano-TiO2 are introduced to modulate the LiZn ferrite, thereby finely controlling the Fe content of the ferrite. 2+ The ion content and grain boundary composition, among other factors, enable the obtained microwave ferrite material to have a narrow ferromagnetic resonance linewidth, low dielectric loss, high saturation magnetization, high remanence ratio, and high Curie temperature.

[0024] Example 1

[0025] Step 1, Pre-fired material preparation:

[0026] 1.1 Using analytically pure lithium carbonate (Li2CO3), zinc oxide (ZnO), titanium dioxide (TiO2), manganese tetroxide (Mn3O4), ferric oxide (Fe2O3), and bismuth trioxide (Bi2O3) as raw materials, the raw materials were weighed according to the following molar ratio: Li2CO3 11.98 mol%, ZnO 19.96 mol%, TiO2 10.84 mol%, Mn3O4 1.9 mol%, Fe2O3 55.24 mol%, Bi2O3 0.08 mol%. The raw materials were then transferred to the stainless steel ball mill jar of a planetary ball mill for a single ball milling process, which lasted for 4 hours.

[0027] 1.2 After drying and sieving the slurry obtained in step 1.1, it is pre-calcined at 800℃ for 2 hours in an oxygen atmosphere. After cooling to room temperature in the furnace, it is taken out to obtain the main pre-calcined material.

[0028] Step 2: Add auxiliary materials and perform secondary ball milling:

[0029] After sieving the main pre-calcined material obtained in step 1, add auxiliary material (rutile TiO2 with a particle size of 25nm) equivalent to 0.10wt.% of the main pre-calcined material mass. Put the resulting mixture into a planetary ball mill for secondary ball milling for 6 hours. After drying the resulting secondary slurry, the second grinding material is obtained.

[0030] Step 3: Shaping and sintering:

[0031] 3.1 After passing the two abrasives obtained in step 2 through an 80-mesh sieve, add 10 wt.% of polyvinyl alcohol (PVA) binder equivalent to the powder mass to granulate, and then press them into green samples using a hydraulic press;

[0032] 3.2 The green sample obtained in step 3.1 is placed in a sintering furnace and heated to 890°C at a rate of 2°C / min. The temperature is held for 2 hours. After sintering, the sample is naturally cooled to room temperature in the furnace to obtain the low-loss microwave ferrite material for the LTCF phase shifter.

[0033] The microwave ferrite material prepared in Example 1 has the following properties: ferromagnetic resonance linewidth ΔH = 90 Oe @ 9.3 GHz; dielectric constant ε' = 15.22; and dielectric loss tangent tanδ. ε =2.01×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3793 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =308.4℃.

[0034] Example 2

[0035] The difference between this embodiment and embodiment 1 is that the auxiliary material added in step 2 is equivalent to 0.20 wt.% of the mass of the pre-fired main material, while the rest of the steps are the same as in embodiment 1.

[0036] The microwave ferrite material prepared in Example 2 has the following properties: ferromagnetic resonance linewidth ΔH = 79 Oe @ 9.3 GHz; dielectric constant ε' = 14.99; and dielectric loss tangent tanδ. ε =1.61×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3776 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =309.8℃.

[0037] Example 3

[0038] The difference between this embodiment and embodiment 1 is that the auxiliary material added in step 2 is equivalent to 0.35 wt.% of the mass of the pre-fired main material, while the rest of the steps are the same as in embodiment 1.

[0039] The microwave ferrite material prepared in Example 3 has the following properties: ferromagnetic resonance linewidth ΔH = 82 Oe @ 9.3 GHz; dielectric constant ε' = 15.25; and dielectric loss tangent tanδ. ε =2.11×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3731 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =309.8℃.

[0040] Example 4

[0041] The difference between this embodiment and embodiment 1 is that the auxiliary material added in step 2 is replaced with anatase TiO2 with a particle size of 25nm, and its mass is equivalent to 0.10wt.% of the mass of the main pre-burned material. The rest of the steps are the same as in embodiment 1.

[0042] The microwave ferrite material prepared in Example 4 has the following properties: ferromagnetic resonance linewidth ΔH = 86 Oe @ 9.3 GHz; dielectric constant ε' = 15.00; and dielectric loss tangent tanδ. ε =2.64×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3783 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c=308.7℃.

[0043] Example 5

[0044] The difference between this embodiment and embodiment 1 is that the auxiliary material added in step 2 is replaced with anatase TiO2 with a particle size of 25nm, and its mass is equivalent to 0.20wt.% of the mass of the main pre-burned material. The rest of the steps are the same as in embodiment 1.

[0045] The microwave ferrite material prepared in Example 5 has the following properties: ferromagnetic resonance linewidth ΔH = 78 Oe @ 9.3 GHz; dielectric constant ε' = 15.15; and dielectric loss tangent tanδ. ε =1.90×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3778 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =309.0℃.

[0046] Example 6

[0047] The difference between this embodiment and embodiment 1 is that the auxiliary material added in step 2 is replaced with anatase TiO2 with a particle size of 25nm, and its mass is equivalent to 0.35wt.% of the mass of the main pre-burned material. The rest of the steps are the same as in embodiment 1.

[0048] The microwave ferrite material prepared in Example 6 has the following properties: ferromagnetic resonance linewidth ΔH = 88 Oe @ 9.3 GHz; dielectric constant ε' = 14.95; and dielectric loss tangent tanδ. ε =2.31×10 -4 @9.3GHz; Saturation magnetization 4πM s = 3759 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =310.7℃.

[0049] Comparative Example

[0050] Compared with Example 1, the difference in the comparative example is that no excipients were added in step 2, while the rest of the steps are the same as in Example 1.

[0051] The microwave ferrite material prepared in the comparative example has the following properties: ferromagnetic resonance linewidth ΔH = 10³ Oe @ 9.3 GHz; dielectric constant ε' = 15.00; and dielectric loss tangent tanδ. ε =3.73×10 -4 @9.3GHz; Saturation magnetization 4πM s= 3794 Gauss; Remanence ratio B r / B s =0.89; Curie temperature T c =308.3℃.

[0052] Figure 1 SEM images of the ferrite samples obtained in Comparative Example (a), Example 2 (b), and Example 6 (c) are shown. Table 1 shows the performance parameters of the comparative examples and examples. Compared with the comparative examples, the microwave loss characteristics of the examples with the addition of trace amounts of nano-TiO2 were significantly improved: the ferromagnetic resonance linewidth decreased by 12.6% to 24.3%, and the dielectric loss tangent decreased by 29.2% to 56.8%; at the same time, it is noted that the Curie temperature of the material increased instead of decreasing.

[0053] Table 1 Performance parameters of comparative examples and embodiments

[0054]

Claims

1. A low-loss microwave ferrite material for LTCF phase shifters, characterized in that, The microwave ferrite material comprises a main material and an auxiliary material, with the auxiliary material accounting for 0.01~2 wt.% of the main material. The main material consists of the following components: Li2CO3 11.65~12.33 mol%, ZnO 17.61~22.18 mol%, TiO2 8.22~13.31 mol%, Mn3O4 1.85~1.96 mol%, Fe2O3 50.93~59.79 mol%, and Bi2O3 0.08~0.09 mol. The auxiliary material is rutile or anatase TiO2 with a particle size of 5 nm~50 nm.

2. A method for preparing a low-loss microwave ferrite material for an LTCF phase shifter, characterized in that, Includes the following steps: Step 1, Pre-fired material preparation: 1.1 Using Li2CO3, ZnO, TiO2, Mn3O4, Fe2O3, and Bi2O3 as raw materials, the raw materials are weighed according to the following proportions: Li2CO3 11.65~12.33mol%, ZnO 17.61~22.18mol%, TiO2 8.22~13.31mol%, Mn3O4 1.85~1.96mol%, Fe2O3 50.93~59.79mol%, Bi2O3 0.08~0.09mol%. The raw materials are then transferred to a planetary ball mill for one ball milling for 3~5 hours to obtain a primary slurry. 1.2 After drying and sieving the primary slurry obtained in step 1.1, pre-calcine it in an oxygen furnace at 780-820℃ for 1.5-2.5 hours. After cooling to room temperature in the furnace, remove it to obtain the pre-calcined main material. Step 2, Secondary ball milling: After sieving the main pre-calcined material obtained in step 1, add auxiliary materials equivalent to 0.01-2 wt.% of the main pre-calcined material mass. The resulting mixture is then placed in a planetary ball mill for secondary ball milling. After ball milling for 5-8 hours, a secondary slurry is obtained, which is then dried to obtain microwave ferrite abrasive. The auxiliary material is rutile or anatase TiO2 with a particle size of 5 nm-50 nm. Step 3: Shaping and sintering: 3.1 The microwave ferrite abrasive obtained in step 2 is sieved, granulated, and pressed into shape; 3.2 Place the sample pressed in step 3.1 into a sintering furnace, heat it to 870~910℃, hold it at that temperature for 2 hours, and allow it to cool naturally to room temperature after sintering to obtain the microwave ferrite material.

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