High-entropy aluminate-based microwave dielectric material with near-zero temperature coefficient of resonant frequency and preparation method thereof

Abstract

This invention discloses a high-entropy aluminate-based microwave dielectric material with a near-zero temperature coefficient of resonant frequency, belonging to the field of microwave electronic ceramic materials. The chemical composition of this material is: [MgZnCa]. (1‑2x) / 3 [CoNi] x Al2O4, where 0.10≤ x ≤0.30, 1.52R≤Δ S ≤1.61R, Δ S In addition to representing the configuration entropy, this invention also discloses a method for preparing the above-mentioned material, including steps such as weighing, ball milling, drying, calcination, secondary ball milling, drying, granulation, molding, debinding, and sintering. The microwave dielectric material provided by this invention has a low dielectric constant (6.79~8.87) and a near-zero temperature coefficient of resonant frequency (~-12 ppm / ℃), thus having high application prospects in the field of next-generation mobile communications.

Description

Technical Field

[0001] This invention relates to the field of microwave electronic ceramic materials, and in particular to a high-entropy aluminate microwave material with a near-zero resonant frequency temperature coefficient and its preparation method. Background Technology

[0002] With the rapid development of modern communication technologies, especially mobile satellite communication and the Global Positioning System (GPS), high-performance microwave dielectric ceramics have attracted widespread attention. Microwave dielectric ceramics, as a functional material, possess excellent dielectric properties, high-frequency characteristics, and temperature stability, making them suitable for microwave communication applications. Meanwhile, high-entropy materials have garnered significant attention due to their unique properties. These materials are typically formed by the solid solution of multiple components in equal or near-equal proportions, exhibiting structural characteristics and performance features distinct from traditional materials. They hold promise for widespread applications in aerospace, new energy electronic devices, and nuclear energy.

[0003] Aluminates are valued for their good quality factor (Q×f) and low dielectric constant (ε). r This has attracted widespread attention (Wu Haitao, Zhao Liping. Research progress of microwave dielectric ceramic materials [J]. Journal of Jinan University (Natural Science Edition). 2016, 30(3): 177-183.). Takahashi S et al. prepared spinel aluminate Mg by ion substitution. 1-x Zn x Al2O4 ceramics have the best performance at ε r =8.4, Q×f=222600GHz, but its resonant frequency temperature coefficient (τ) f The value is -61ppm / ℃, which cannot meet the requirements for τ in actual use. f The requirement is near zero.

[0004] Deng et al. obtained Mg2GeO4-MgAl2O4 ceramics through a composite method, which exhibited good dielectric properties (ε). r =8.0, Q×f=150000GHz, τ f =-34ppm / ℃), but its τ f The value is still not close to zero. Surendran KP et al. used TiO2 to adjust the τ of MgAl2O4. f The value, although it can be τ f The value was adjusted to near zero, but TiO2's high dielectric constant and low Q×f value (ε) r =105, Q×f=46000GHz) will lead to a deterioration in the dielectric constant and quality factor of MgAl2O4. Furthermore, the two-phase recombination method can be used to adjust τ. f The value can easily generate a second phase, which can lead to uncontrollable microwave dielectric properties.

[0005] In summary, traditional ionic substitution struggles to achieve chemical bond distortion while simultaneously maintaining crystal structure stability, which limits its application in controlling microwave dielectric properties. Furthermore, the combination of positive and negative temperature coefficient phases can easily deteriorate the dielectric constant and quality factor, rendering microwave dielectric properties uncontrollable. Summary of the Invention

[0006] One of the objectives of this invention is to provide a high-entropy aluminate-based microwave dielectric material with a near-zero temperature coefficient of resonant frequency, in order to solve the aforementioned problems.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] Its chemical composition is: [MgZnCa] (1-2x) / 3 [CoNi] x Al2O4, where 0.10≤x≤0.30, 1.52R≤ΔS≤1.61R, and ΔS represents the configuration entropy.

[0009] The calculation method is as follows: Where R represents the ideal gas constant, with a value of 8.314 J / K·mol; x i This indicates the mole fraction of each component in the system; N represents the number of elements.

[0010] To address the above problems, the inventors proposed using Zn 2+ Ca 2+ Co 2+ Ni 2+ Ion substitution of Mg in MgAl2O4 2 + Ultimately, a high-entropy aluminate microwave ceramic with inexpensive raw materials, simple preparation process, and near-zero temperature coefficient of resonant frequency was obtained.

[0011] High-entropy ceramics (ΔS≥1.5R) offer greater potential for structural and performance tuning in microwave dielectric ceramics due to their high-entropy effect, hysteresis diffusion effect, lattice distortion in structure, and synergistic performance enhancement. High configurational entropy and hysteresis diffusion improve the single-phase formation capability and phase stability of the system, preventing the formation of a second phase and thus avoiding uncontrollable microwave dielectric properties. Lattice distortion and synergistic effects can effectively tune microwave dielectric properties; therefore, optimizing the microwave dielectric properties of aluminate ceramic systems through the unique effects of high entropy is feasible and holds promise for achieving near-zero τ. f Values ​​and higher Q×f values.

[0012] The second objective of this invention is to provide a method for preparing the above-mentioned material, comprising the following steps:

[0013] (1) According to [MgZnCa] (1-2x) / 3 [CoNi] x Al2O4, wherein 0.10≤x≤0.30, is obtained by weighing, ball milling, and drying raw materials MgO, ZnO, NiCO3, CoCO3, CaCO3 and Al2O3 to obtain a uniformly mixed and dried powder.

[0014] (2) The uniformly mixed and dried powder is ground and then pre-fired to obtain pre-fired material;

[0015] (3) The pre-burned material is subjected to secondary ball milling, and then dried for later use.

[0016] (4) The powder after secondary ball milling is mixed with the binder solution for granulation and then pressed into shape;

[0017] (5) The sample after pressing is debonded to obtain a green blank, and then the green blank is sintered to obtain the required material.

[0018] As a preferred technical solution, in step (1), the weighed raw materials are placed in a ball mill jar, with deionized water as the ball milling medium. The mass ratio of powder to deionized water is 1:0.8 to 1.5. The difference between the maximum and minimum mass of the four ball mill jars is no more than 2g. The ball milling speed is 250 to 300 rpm, and the ball milling time is 4 to 12 hours. The raw materials are mixed evenly by ball milling once. After ball milling, the powder is dried to constant weight for later use.

[0019] As a preferred technical solution, the specific conditions for the pre-firing treatment in step (2) are as follows: the pre-firing temperature is 1200-1400℃, the pre-firing heating rate is 2-10℃ / min, the holding time is 2-6h; the pre-firing cooling rate is 5℃ / min, and after cooling to 500℃, it is cooled to room temperature with the furnace.

[0020] As a preferred technical solution, the adhesive solution in step (4) is a PVA solution with a concentration of 5-10 wt% and an added mass percentage of 5 wt%-20 wt%. The specific pressing conditions are: pressure of 10-20 MPa, diameter of the pressed cylinder of 12 mm, and thickness of 5-7 mm.

[0021] In step (3), the secondary ball milling process parameters are the same as those in step (1) for the primary ball milling.

[0022] As a preferred technical solution, the specific conditions for the glue removal process in step (5) are: the processing temperature is 400-600℃, the heating rate of the glue removal process is 2-5℃ / min, and the holding time is 2-6h.

[0023] As a preferred technical solution, the specific conditions for the sintering treatment in step (5) are as follows: the sintering temperature is 1500℃, the heating rate is 2~5℃ / min, the holding time is 2~6h; the sintering reaction cooling rate is 5℃ / min, and the temperature is cooled to 500℃ and then cooled to room temperature.

[0024] This invention is based on [MgZnCa]. (1-2x) / 3 [CoNi] x When MgO, ZnO, NiCO3, CoCO3, CaCO3, and Al2O3 are mixed and reacted in the corresponding proportions, the resulting phase is mainly spinel-type [MgO]. 0.2 Zn 0.2 Ca 0.2 Co 0.2 Ni 0.2 Al2O4 and Ca3Al 10 O 18 A high-entropy aluminate microwave dielectric ceramic with a near-zero temperature coefficient of resonant frequency was generated by solid-state reaction method.

[0025] Compared with existing technologies, the advantages of this invention are: the material of this invention has a near-zero temperature coefficient of resonant frequency, making it suitable for use as an antenna substrate material. Because Zn 2+ Ca 2+ Co 2+ Ni 2+ Ions partially replace Mg in MgAl2O4 2+ The changes in the valence of the A-site and B-site bonds result in the "compressed" and "rattling" effects of the cations, leading to a significant change in the temperature coefficient of the resonant frequency. Therefore, the near-zero temperature coefficient of the resonant frequency is achieved by the changes in chemical bonds caused by the synergistic effect of multiple ions, and a near-zero temperature coefficient of the resonant frequency can be obtained without the need for a two-phase recombination method. Attached Figure Description

[0026] Figure 1 The X-ray diffraction (XRD) patterns of sintered samples with different x values ​​at 1500℃ in Example 1 are shown; "PDF#21-1552" and "PDF#01-0572" in the figure are crystal phase standard card numbers.

[0027] Figure 2 These are the microwave dielectric properties of the material with different x values ​​during sintering at 1500℃ in Example 1;

[0028] Figure 3 These are the microwave dielectric properties of the material with different x values ​​during sintering at 1450℃ in Example 2;

[0029] Figure 4The microwave dielectric properties at different sintering temperatures when x = 0.15 are shown in Example 3.

[0030] Figure 5 The microwave dielectric properties parameters are for different sintering temperatures when x = 0.20 in Example 4. Detailed Implementation

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] Example 1:

[0033] A two-phase high-entropy aluminate microwave dielectric material with a near-zero temperature coefficient of resonant frequency is prepared by the following steps:

[0034] Step 1: Weigh the raw materials according to the molar ratio of MgO:ZnO:CaCO3:NiCO3:CoCO3:Al2O3=(1-2x) / 3:(1-2x) / 3:(1-2x) / 3:x:x:1 (0.10≤x≤0.30). Use a 0.001g electronic balance to weigh the raw materials, ensuring that the error between the weighed value and the theoretical calculation value is no greater than 0.0005g. Place the weighed raw materials in a ball mill jar, use zirconium balls as grinding balls and deionized water as the ball milling medium, and ball mill at 250rpm for 4 hours. After ball milling, place the slurry in a constant temperature drying oven and dry it to constant weight for later use.

[0035] Step 2: Crush the dried and agglomerated mixed powder obtained in Step 1 in a mortar, place it in a crucible and compact it. Increase the temperature to 100℃ at a rate of 2℃ / min, then increase it to 1300℃ at a rate of 10℃ / min and hold it for 4 hours. Decrease the temperature to 500℃ at a rate of 5℃ / min, and then cool it to room temperature in the furnace to obtain [MgZnCa]. (1-2x) / 3 [Co.Ni] x Al2O4 pre-calcined material is further placed into a ball mill jar for secondary ball milling. The ball milling process is the same as the first ball milling. After ball milling, the material is dried to constant weight for later use.

[0036] Step 3: Crush the dried and agglomerated pre-fired material obtained in Step 2 in a mortar, add 10wt% PVA solution as a binder, grind and granulate, and pass it through 40 mesh and 120 mesh sieves at the same time. Take the granulated material in the middle (i.e. in the 120 mesh sieve) and dry press it into a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm under uniaxial pressure at 20 MPa.

[0037] Step 4: Place the cylindrical green sample obtained in Step 3 into a high-temperature sintering furnace, raise the temperature to 100°C at a rate of 5°C / min, then raise it to 600°C at a rate of 10°C / min and hold it for 4 hours to remove the PVA organic binder. Then lower the temperature to 500°C at a rate of 5°C / min and cool it to room temperature with the furnace to obtain the green sample after binder removal.

[0038] Step 5: Place the debinding green sample obtained in Step 4 back into the high-temperature sintering furnace, raise the temperature to 100°C at a rate of 5°C / min, then raise it to 1500°C at a rate of 10°C / min and hold it for 4 hours for sintering. After the holding period, lower the temperature to 500°C at a rate of 5°C / min and then cool it to room temperature with the furnace to obtain a low-sintering-temperature dual-phase high-entropy aluminate microwave dielectric ceramic. The configurational entropy of the material obtained in this embodiment is: 1.52R≤ΔS≤1.61R.

[0039] XRD patterns of materials with different x values ​​are as follows Figure 1 As shown, from Figure 1 The sample contains [Mg] 0.2 Zn 0.2 Ca 0.2 Co 0.2 Ni 0.2 Al2O4 and Ca3Al 10 O 18 Characteristic peaks.

[0040] ε corresponding to different values ​​of sample x r Q×f and τ f Values ​​such as Figure 2 As shown, from Figure 2 As can be seen from this, when x = 0.10 to 0.30, ε r =8.25~8.57, Q×f=34500~54900GHz, τ f = -49 to -12 ppm / ℃. Furthermore, when x = 0.15, the material exhibits excellent properties: ε r =8.51, Q×f=54900GHz, τ f = -12ppm / ℃.

[0041] Example 2

[0042] Compared with Example 1, this embodiment differs only in that the sintering temperature in step 5 is changed from 1500℃ to 1450℃; all other parameters are the same as in Example 1. The configurational entropy of the material obtained in this embodiment is: 1.52R≤ΔS≤1.61R. The ε0 of the obtained sample is... r Value, Q×f value and τ f Values ​​such as Figure 3 As shown, when x = 0.10 to 0.30, ε r =8.32~8.87, Q×f=28300~49600GHz, τ f = -42 to +3 ppm / ℃.

[0043] Example 3

[0044] Compared with Example 1, this embodiment keeps x = 0.15 and changes the sintering temperature to 1400-1550℃. Everything else is the same as in Example 1. The configurational entropy of the material obtained in this embodiment is ΔS = 1.59R, and the ε of the obtained sample... r Value, Q×f value and τ f Values ​​such as Figure 4 As shown, ε r =7.27~8.87, Q×f=11000~54900GHz, τ f = -12 to +4 ppm / ℃.

[0045] Example 4

[0046] Compared with Example 1, this embodiment keeps x = 0.20 and changes the sintering temperature to 1400–1550 °C. Everything else is the same as in Example 1. The configurational entropy of the material obtained in this embodiment is ΔS = 1.61R, and the ε of the obtained sample… r Value, Q×f value and τ f Values ​​such as Figure 5 As shown, ε r =7.16~8.67, Q×f=7764~54400GHz, τ f = -37 to -7 ppm / ℃.

[0047] Comparative Example 1

[0048] Compared with Example 1, this comparative example reduces the number of substituted ions (two ions substituted [Mg]). 1 / 3 Zn 1 / 3 Co 1 / 3 Al₂O₄ (ΔS = 1.1R) and three ionic substitutions [Mg 1 / 4 Zn 1 / 4 Co 1 / 4 Ni 1 / 4 Al2O4 (ΔS=1.39R), the rest is the same as in Example 1, and the obtained sample [Mg 1 / 3 Zn 1 / 3 Co 1 / 3 ε of Al2O4 r Value, Q×f value and τ f Value: ε r =9.08, Q×f=59400GHz, τ f = -38ppm / ℃; Sample [Mg 1 / 4 Zn 1 / 4 Co 1 / 4 Ni 1 / 4 ε of Al2O4 r Value, Q×f value and τ f Value: ε r =8.62, Q×f=26500GHz, τf = -60ppm / ℃.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-entropy aluminate-based microwave dielectric material with a near-zero temperature coefficient of resonant frequency, characterized in that, Its chemical composition is: [MgZnCa] (1-2x) / 3 [CoNi] x Al2O4, where 0.10 ≤ x ≤ 0.30, 1.52R ≤ Δ S ≤ 1.61R, Δ S τ represents configuration entropy. f = -12~+4 ppm / ℃.

2. The method for preparing the high-entropy aluminate-based microwave dielectric material with a near-zero temperature coefficient of resonant frequency as described in claim 1, characterized in that, Includes the following steps: (1) According to [MgZnCa] (1-2x) / 3 [CoNi] x The proportion of Al2O4 was determined by weighing the raw materials MgO, ZnO, CaCO3, NiCO3, CoCO3 and Al2O3, ball milling them once, and drying them to obtain a uniformly mixed and dried powder. (2) The uniformly mixed and dried powder is ground and then pre-fired to obtain pre-fired material; (3) The pre-burned material is subjected to secondary ball milling, and then dried for later use; (4) The powder after secondary ball milling is mixed with the binder solution, granulated, and then pressed into shape; (5) The sample after pressing is debonded to obtain a green blank, and then the green blank is sintered to obtain the required material.

3. The preparation method according to claim 2, characterized in that, The specific conditions for the pre-firing treatment in step (2) are as follows: the pre-firing temperature is 1200~1400 ℃, the pre-firing heating rate is 2~10 ℃ / min, the holding time is 2~6 h; the pre-firing cooling rate is 5 ℃ / min, and after cooling to 500 ℃, it is cooled to room temperature with the furnace.

4. The preparation method according to claim 2, characterized in that, The adhesive solution in step (4) is a PVA solution with a concentration of 5-10 wt% and an added mass percentage of 5 wt%-20 wt%. The specific pressing conditions are: pressure of 10-20 MPa, diameter of the pressed cylinder of 12 mm, and thickness of 5-7 mm.

5. The preparation method according to claim 2, characterized in that, The specific conditions for the glue removal process described in step (5) are as follows: The processing temperature is 400–600 ℃, the heating rate of the glue removal process is 2–5 ℃ / min, and the holding time is 2–6 h.

6. The preparation method according to claim 2, characterized in that, The specific conditions for the sintering treatment in step (5) are: sintering temperature of 1500 ℃, heating rate of 2~5 ℃ / min, and holding time of 2~6 h; After sintering, the cooling rate is 5 ℃ / min, and the temperature is reduced to 500 ℃ and then cooled to room temperature.

Images