Preparation method of garnet ferrite material with low cost, high dielectric constant and low loss

Abstract

The invention discloses a preparation method of a garnet ferrite material with low cost, high dielectric constant and low loss, and relates to the field of microwave ferrite materials. BiaCabY3-a-bZrcVdZneFe5-c-d-e-deltaO12, a is greater than or equal to 1 and less than or equal to 2, b is greater than or equal to 0.2 and less than or equal to 1, c is greater than or equal to 0.2 and less than or equal to 1, d is greater than or equal to 0.01 and less than or equal to 0.1, e is greater than or equal to 0.02 and less than or equal to 0.05, delta is greater than or equal to 0.01 and less than or equal to 0.05, and the invention further provides a preparation method of the material. The garnet ferrite material with high dielectric constant and low loss is obtained by utilizing low-cost raw materials and an advanced sintering technology, the dielectric constant epsilon'of the garnet ferrite material is about 30, the saturation magnetization is 4piMs and about 1950Gs, the ferromagnetic resonance line width delta H is lower than 40Oe, and the dielectric loss tan delta epsilon is less than or equal to 4 * 10 <-4 >. The high dielectric constant is an important technical approach for realizing miniaturization and light weight of microwave ferrite devices. The material has low ferromagnetic resonance line width and dielectric loss, not only can effectively reduce device loss, but also can broaden the working bandwidth of a microwave device, thereby improving the overall performance of the device. And the material is low in preparation cost, can significantly reduce the cost of microwave devices, and has good economic applicability.

Description

Technical Field

[0001] The present invention relates to a preparation method of a garnet ferrite material with low cost, high permittivity and low loss, especially a ferrite circulator applied to radar and 5G communication systems, belonging to the field of microwave ferrite materials. Background Art

[0002] Microwave ferrite devices play a crucial role in the field of microwave communication. Yttrium iron garnet ferrite, as an important microwave ferrite material, is widely used in isolators, circulators, filters, phase shifters and many other electronic magnetic and optical devices in radar and 5G communication systems. There are no cation vacancies in pure garnet ferrite, which endows it with the unique advantage of low microwave magnetic loss (i.e., low ferromagnetic resonance linewidth). Since its saturation magnetization (4πM s ) is usually lower than 2000 Gs, it has long been the preferred material for ferrite circulators in the X and lower frequency bands. With the development of communication technology, the requirements for miniaturization and lightweight of ferrite devices are becoming increasingly stringent. According to the relevant theories of the design of ferrite circulators and the transmission characteristics of electromagnetic waves, increasing the permittivity (ε) of ferrite materials is one of the important technical ways to achieve the miniaturization and lightweight of circulators. However, the permittivity of conventional microwave ferrites is usually about 13 - 17, and the permittivity of yttrium iron garnet ferrite is usually about 14. In order to increase the permittivity of yttrium iron garnet ferrite materials, some researchers have proposed using highly polarized ions for ion substitution. In recent years, some patents have reported the preparation methods of yttrium iron garnet with high permittivity. For example, patents with publication numbers CN114436637B, CN118145978, etc. have successfully prepared garnet ferrite materials with high permittivity and obtained relatively low ferromagnetic resonance linewidths. For yttrium iron garnet ferrite materials with a saturation magnetization of approximately 2000 Gs, it is usually difficult to simultaneously achieve high microwave dielectric constants and low ferromagnetic resonance line widths. In terms of increasing the dielectric constant, a main formulation system with Bi ion substitution can be adopted. Bi2O3 has a low melting point (about 820 °C), and both pre-sintering and sintering are carried out above this melting point. During this process, Bi2O3 will exist in a liquid state. When a formulation with a higher Bi content is used to increase the dielectric constant, too much liquid phase will cause uneven solid-phase reactions inside the sample, resulting in a decrease in the uniformity of the microstructure and an increase in defects, thereby leading to an increase in the microwave magnetic loss and dielectric loss of the material. This phenomenon is more serious especially when the dielectric constant of the yttrium iron garnet ferrite material is higher than 25. How to obtain garnet ferrite with both high dielectric constant, low ferromagnetic resonance line width, and low dielectric loss has become a research focus for scholars. Usually, ion substitution with precious metal oxides (such as In2O3) can effectively reduce the ferromagnetic resonance line width, but this will greatly increase the raw material cost of the yttrium iron garnet ferrite material. To avoid dependence on precious metals, how to develop yttrium iron garnet ferrite materials with low cost and high performance has become a challenge. In view of this problem, the present invention proposes a low-cost high-dielectric low-loss garnet ferrite material. By optimizing the main formulation system, reducing the usage of precious metal raw materials, and through optimized pre-sintering and sintering processes, a high-performance yttrium iron garnet ferrite material with both high dielectric constant, low ferromagnetic resonance line width, and low dielectric loss is obtained. This invention can provide a key technology for the development of miniaturized and lightweight ferrite circulators. Summary of the Invention

[0003] The present invention mainly aims at the development trends of miniaturization, lightweight, large bandwidth, and low loss of garnet ferrite devices, and provides a preparation method for a low-cost high-dielectric low-loss garnet ferrite material, aiming to further increase the dielectric constant of the garnet ferrite material while regulating the ferromagnetic resonance line width. High Bi substitution will inevitably cause a sharp increase in the ferromagnetic resonance line width, so the present invention only uses Ca 2+ Zr 4+ Zn 2+ ion combined substitution to regulate and reduce the ferromagnetic resonance line width, and introduce a small amount of V 5+ and Zn 2+ ion substitution to improve the magnetocrystalline anisotropy and microstructure of the material to meet the requirements of miniaturization, low loss, and large bandwidth of ferrite circulators / isolators. Using cheap metal oxides as raw materials, adopting a multi-stage sintering process and optimizing the sintering process curve, simplifying the preparation process, reducing the production cost of the material while regulating the material properties. The prepared yttrium iron garnet ferrite has a relatively high dielectric constant ε' of about 30, a relatively low ferromagnetic resonance line width ΔH below 40 Oe, and a microwave dielectric loss tanδ ε ≤4×10 -4 .

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A preparation method of a low-cost, high-permittivity and low-loss garnet ferrite material, comprising the following steps:

[0006] Step 1, batching:

[0007] Using Y2O3, Bi2O3, CaCO3, ZrO2, V2O5, ZnO and Fe2O3 as raw materials with analytical purity. Weigh the raw materials according to the stoichiometric ratio of the chemical formula Bi a Ca b Y 3-a-b Zr c V d Zn e Fe 5-c-d-e-δ O 12 ; where 1 ≤ a ≤ 2, 0.2 ≤ b ≤ 1, 0.2 ≤ c ≤ 1, 0.01 ≤ d ≤ 0.1, 0.02 ≤ e ≤ 0.05, 0.01 ≤ δ ≤ 0.05, and δ is the iron deficiency amount.

[0008] Step 2, primary ball milling:

[0009] Add deionized water to the powder weighed in Step 1 for primary ball milling, with the ball milling speed of 220 - 260 rpm and the ball milling time of 4 - 6 h.

[0010] Step 3, pre-sintering:

[0011] Dry the primary ball milled material obtained in Step 2, then screen it, and conduct pre-sintering at a pre-sintering temperature of 800 - 900 °C for 2 - 5 h.

[0012] Step 4, secondary ball milling:

[0013] Add deionized water to the pre-sintered material obtained in Step 3 for secondary ball milling, with the ball milling speed of 260 - 290 rpm and the ball milling time of 4 - 6 h.

[0014] Step 5, granulation:

[0015] After drying the secondary ball milled material obtained in Step 4, add a binder and conduct granulation and screening.

[0016] Step 6, forming:

[0017] Press the granulated material obtained in Step 5 into shape with a pressing pressure of 180 - 210 MPa.

[0018] Step 7, sintering:

[0019] The green compact formed in Step 8 is sintered in an atmosphere furnace at a sintering temperature of 850 - 950 °C for about 10 h. After sintering, the yttrium iron garnet ferrite material is obtained.

[0020] Further, the purity of each raw material in Step 1 is as follows: the purity of Y2O3 is 99.99%, the purity of Fe2O3 is 99.3%, the purity of CaCO3 is 98.5%, the purity of Bi2O3 is 99%, the purity of ZrO2 is 99%, the purity of V2O5 is 99%, and the purity of ZnO is 99%.

[0021] Further, in Step 2, the mass ratio of balls:materials:deionized water is 4:1:1.5.

[0022] Further, in Step 4, the mass ratio of balls:materials:deionized water is 4:1:1.5.

[0023] Further, in Step 5, the binder is an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 10 - 15 wt%.

[0024] In Step 7, the sintering process is a multi-stage sintering process using an oxygen atmosphere for sintering.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The present invention provides a method for preparing a garnet ferrite material with low cost, high permittivity and low loss. According to the characteristics of oxide raw materials, a multi-stage sintering process is adopted, and the degree of completion of the solid-phase reaction in the sintering stage is higher, and the material properties are more excellent; a high Bi substitution is used to greatly improve the permittivity of the material, and Ca 2+ Zr 4+ Zn 2+ Combined substitution is used to regulate and reduce the ferromagnetic resonance linewidth of the material. The introduction of V 5+ Substitution is used to regulate the microstructure of the material. The preparation process is simple, the production cycle is short, and a formulation system without indium and lanthanide rare earth ion substitution is adopted, so the production cost of the material is low.

[0027] 2. The garnet ferrite material prepared by the present invention has a permittivity ε' of about 30, a ferromagnetic resonance linewidth ΔH lower than 40 Oe, a saturation magnetization 4πM s of about 1950 Gs, and a dielectric loss tanδ ε ≤4×10 -4 . It can effectively reduce the design size of microwave ferrite devices and fully meet the development trend of miniaturization. At the same time, the narrower linewidth helps to reduce the insertion loss of the device, thereby broadening the working bandwidth of microwave ferrite devices. Description of the Drawings

[0028] Figure 1Magnetization curve of the ferrite material of Example 2.

[0029] Figure 2 Magnetization curve of the ferrite material of Example 3.

[0030] Figure 3 XRD pattern for phase analysis of the ferrite material of Example 2.

[0031] Figure 4 XRD pattern for phase analysis of the ferrite material of Example 3. Detailed implementation manners

[0032] The technical solution of the present invention will be described in detail below in conjunction with the embodiments.

[0033] Example 1

[0034] A method for preparing a low-cost high-dielectric low-loss garnet ferrite material, comprising the following steps:

[0035] Step 1, proportioning:

[0036] Using Y2O3 with a purity of 99.99%, Bi2O3 with a purity of 99%, CaCO3 with a purity of 98.5%, ZrO2 with a purity of 99%, ZnO with a purity of 99%, and Fe2O3 with a purity of 99.3% as raw materials, and calculating and weighing the raw materials according to the stoichiometric ratio of the chemical formula Bi a Ca b Y 3-a- b Zr c V d Zn e Fe 5-c-d-e-δ O 12 where a = 1.4, b = 0.34, c = 0.35, d = 0.01, e = 0.03, and δ = 0.012.

[0037] Step 2, primary ball milling:

[0038] Add deionized water to the powder weighed in Step 1 for primary ball milling, with a ball milling speed of 241 rpm and a ball milling time of 6 h.

[0039] Step 3, pre-sintering:

[0040] After drying the primary ball milled material obtained in Step 2, perform pre-sintering at a pre-sintering temperature of 865°C.

[0041] Step 4, secondary ball milling:

[0042] Add deionized water to the pre-sintered material obtained in Step 3 for secondary ball milling, with a ball milling speed of 281 rpm and a ball milling time of 4 h.

[0043] Step 5, Granulation:

[0044] After drying the secondary ball-milled abrasive obtained in Step 4, an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 11 wt% is added for granulation and sieving.

[0045] Step 6, Molding:

[0046] The granulated material obtained in Step 5 is pressed into shape, and the pressing pressure is 200 MPa.

[0047] Step 7, Sintering:

[0048] The formed green compact is placed in an oxygen atmosphere sintering device for high-temperature sintering. In the temperature range near the melting point of bismuth oxide, the heating rate is 0.5 °C / min, the sintering temperature is 850 - 950 °C, and the holding time is 10 h. Example 2

[0049] A preparation method of a low-cost high-dielectric low-loss garnet ferrite material, comprising the following steps:

[0050] Step 1, Batching:

[0051] Using Y2O3 with a purity of 99.99%, Bi2O3 with a purity of 99%, CaCO3 with a purity of 98.5%, ZrO2 with a purity of 99%, ZnO with a purity of 99%, and Fe2O3 with a purity of 99.3% as raw materials, according to the chemical formula Bi a Ca b Y 3-a- b Zr c V d Zn e Fe 5-c-d-e-δ O 12 Calculate and weigh the raw materials according to the stoichiometric ratio; where a = 1.4, b = 0.39, c = 0.4, d = 0.01, e = 0.03, δ = 0.012;

[0052] Step 2, Primary Ball Milling:

[0053] Add deionized water to the powder weighed in Step 1 for primary ball milling, with a ball milling speed of 241 rpm and a ball milling time of 6 h.

[0054] Step 3, Pre-sintering:

[0055] After drying the primary ball-milled abrasive obtained in Step 2, perform pre-sintering, and the pre-sintering temperature is 865 °C.

[0056] Step 4, Secondary Ball Milling:

[0057] Add deionized water to the pre-sintered material obtained in Step 3 for secondary ball milling, with a ball milling speed of 281 rpm and a ball milling time of 4 h.

[0058] Step 5, Granulation:

[0059] After drying the secondary ball-milled material obtained in Step 4, add an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 11 wt% for granulation and sieving.

[0060] Step 6, Molding:

[0061] Press the granulated material obtained in Step 5 into shape, with a pressing pressure of 200 MPa.

[0062] Step 7, Sintering:

[0063] Place the formed green body in an oxygen atmosphere sintering device for high-temperature sintering. In the temperature range near the melting point of bismuth oxide, the heating rate is 0.5 °C / min, the sintering temperature is 850 - 950 °C, and keep it warm for 10 h.

[0064] Example 3

[0065] A preparation method of a low-cost, high-dielectric and low-loss garnet ferrite material, comprising the following steps:

[0066] Step 1, Batching:

[0067] Using Y2O3 with a purity of 99.99%, Bi2O3 with a purity of 99%, CaCO3 with a purity of 98.5%, ZrO2 with a purity of 99%, V2O5 with a purity of 99%, ZnO with a purity of 99% and Fe2O3 with a purity of 99.3% as raw materials, calculate and weigh the raw materials according to the stoichiometric ratio of the chemical formula Bi a Ca b Y 3-a-b Zr c V d Zn e Fe 5-c-d-e-δ O 12 ; where a = 1.4, b = 0.41, c = 0.4, d = 0.02, e = 0.03, δ = 0.012.

[0068] Step 2, Primary Ball Milling:

[0069] Add deionized water to the powder weighed in Step 1 for primary ball milling, with a ball milling speed of 241 rpm and a ball milling time of 6 h.

[0070] Step 3, Pre-sintering:

[0071] After drying the primary ball-milled material obtained in Step 2, conduct pre-sintering, with a pre-sintering temperature of 865 °C.

[0072] Step 4, Secondary Ball Milling:

[0073] Add deionized water to the pre-sintered material obtained in Step 3 and perform secondary ball milling at a ball milling speed of 281 rpm for 4 h.

[0074] Step 5, Granulation:

[0075] After drying the secondary ball-milled material obtained in Step 4, add an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 11 wt% for granulation and sieving.

[0076] Step 6, Molding:

[0077] Press the granulated material obtained in Step 5 into shape at a pressing pressure of 200 MPa.

[0078] Step 7, Sintering:

[0079] Place the formed green body in an air atmosphere sintering device for high-temperature sintering. In the temperature range near the melting point of bismuth oxide, the heating rate is 0.5 °C / min, the sintering temperature is 850 - 950 °C, and hold for 10 h.

[0080] Example 4

[0081] A method for preparing a low-cost high-dielectric low-loss garnet ferrite material, comprising the following steps:

[0082] Step 1, Batching:

[0083] Using Y2O3 with a purity of 99.99%, Bi2O3 with a purity of 99%, CaCO3 with a purity of 98.5%, ZrO2 with a purity of 99%, ZnO with a purity of 99%, and Fe2O3 with a purity of 99.3% as raw materials, calculate and weigh the raw materials according to the stoichiometric ratio of the chemical formula Bi a Ca b Y 3-a- b Zr c V d Zn e Fe 5-c-d-e-δ O 12 ; where a = 1.4, b = 0.49, c = 0.5, d = 0.01, e = 0.03, δ = 0.012.

[0084] Step 2, Primary Ball Milling:

[0085] Add deionized water to the powder weighed in Step 1 for primary ball milling at a ball milling speed of 241 rpm for 6 h.

[0086] Step 3, Pre-sintering:

[0087] After drying the primary ball-milled material obtained in Step 2, perform pre-sintering at a pre-sintering temperature of 865 °C.

[0088] Step 4: Secondary ball milling:

[0089] Add deionized water to the pre-sintered material obtained in Step 3 for secondary ball milling. The ball milling speed is 281 rpm and the ball milling time is 4 h.

[0090] Step 5: Granulation:

[0091] After drying the secondary ball milled material obtained in Step 4, add an aqueous solution of polyvinyl alcohol (PVA) with a concentration of 11 wt% for granulation and sieving.

[0092] Step 6: Molding:

[0091] Press the granulated material obtained in Step 5 into shape. The pressing pressure is 200 MPa.

[0093] Step 7: Sintering:

[0094] Place the formed green body in an oxygen atmosphere sintering device for high-temperature sintering. In the temperature range near the melting point of bismuth oxide, the heating rate is 0.5 °C / min, the sintering temperature is 850 - 950 °C, and keep the temperature for 10 h.

[0096] The properties of the ferrite materials obtained in Examples 1 - 4 are shown in Table 1: Table 1 Properties of the Ferrite Materials in Examples 1 - 4

[0097]

Claims

1. A method for preparing a low-cost, high-dielectric and low-loss garnet ferrite material, characterized in that: The following steps are involved: Step 1. Ingredients: Y2O3, Bi2O3, CaCO3, ZrO2, V2O5, ZnO and Fe2O3 are used as raw materials, and the purity is analytically pure. a Ca b Y 3-a-b Zr c V d Zn e Fe 5-c-d-e-δ O 12 Calculate the stoichiometric ratio and weigh the raw materials; in 1≤a≤2, 0.2≤b≤1, 0.2≤c≤1, 0.01≤d≤0.1, 0.02≤e≤0.05, 0.01≤δ≤0.05, δ is the amount of iron deficiency. Step 2: First ball milling: The powder weighed in step 1 is ball-milled once, with a ball-milling speed of 220-260 rpm and a ball-milling time of 4-6 h. Step 3: Pre-burning: The primary ball mill material obtained in step 2 is dried and sieved, and pre-fired at 800-900° C. for 2-5 hours, with a cooling rate of fast and slow. Step 4: Secondary ball milling: The pre-sintered material obtained in step 3 is subjected to secondary ball milling, the ball milling speed is 260-290prm, and the ball milling time is 4-6h. Step 5: Granulation: After drying the secondary ball mill material obtained in step 4, a binder is added and granulation and screening are performed. Step 6: Molding: The granulated material obtained in step 5 is pressed into a shape at a pressing pressure of 180-210 MPa. Step 7: Sintering: The green compact formed in step 6 is placed in an oxidizing atmosphere furnace for sintering. After sintering, the garnet ferrite material is obtained.

2. The method for preparing the low-cost, high-dielectric and low-loss garnet ferrite material according to claim 1, characterized in that: In the first ball milling of step 2, the grinding balls are zirconium oxide, the ball milling medium is deionized water, and the mass ratio of balls: material: deionized water is 4:1:1.

5.

3. The method for preparing the low-cost, high-dielectric and low-loss garnet ferrite material according to claim 1, characterized in that: In step 3, the dried abrasive needs to be sieved through a 40-mesh sieve and then placed in a crucible for pre-sintering. A combination of fast and slow cooling rates is used to control grain defects and particle size. During the cooling process, when the temperature is above 465°C, a rapid cooling rate of 1-2°C / min is used. When the temperature is below 465°C, a slow cooling rate of 0.5-1°C / min is used.

4. The method for preparing the low-cost, high-dielectric and low-loss garnet ferrite material according to claim 1, characterized in that: In the secondary ball milling of step 4, the grinding balls are zirconia balls, the ball milling medium is deionized water, and the mass ratio of balls: material: deionized water is 4:1:1.

5.

5. The method for preparing the low-cost, high-dielectric and low-loss garnet ferrite material according to claim 1, characterized in that: In step 5, the adhesive is a polyvinyl alcohol aqueous solution with a concentration of 10-15wt%, and the powder particles are sieved with a mesh size of 80-200.

6. The method for preparing the low-cost, high-dielectric and low-loss garnet ferrite material according to claim 1, characterized in that: The sintering process in step 7 is a multi-stage sintering process, which makes the solid phase reaction more complete. The specific process is as follows: sinter in oxygen at 840-870℃ for about 2h. Then sinter in oxygen at 900-950℃ for 8-10h. Regarding the heating and cooling rate, during the heating stage, slow heating is adopted in the temperature range near the melting point of Bi2O3, with a rate of 0.5-1.5℃ / min, and rapid heating is adopted in the remaining stages, with a rate of about 2℃ / min. In the cooling stage, rapid cooling is adopted above 500℃, and naturally cools to room temperature below 500℃.

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