Ultra-high performance ceramic material suitable for millimeter wave communication and preparation method thereof

Abstract

The invention relates to an ultra-high performance ceramic material suitable for millimeter wave communication and a preparation method thereof. The chemical formula of the microwave dielectric ceramic is Mg (2-x) Ga (0.5 x) Li (0.5 x) SiO4, wherein 0 lt; x is less than or equal to 0.06. The ceramic adopts MgO, Ga2O3, Li2O and SiO2 as raw materials, and is prepared by raw material pretreatment, primary ball milling, pre-sintering, secondary ball milling, granulation, pressing, glue discharging and sintering. The material can be suitable for high-frequency millimeter wave dielectric resonant antennas, dielectric resonators, filters and other low-dielectric-loss wireless communication devices, and a ceramic material with reliable performance is provided for the field of high-frequency millimeter wave communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave dielectric ceramic materials, and specifically relates to a Mg 2-x Ga 0.5x Li 0.5x SiO4 microwave dielectric ceramic and its preparation method. Background Art

[0002] With the development of 5G / 6G communications, automotive millimeter-wave radars, satellite communications, and high-frequency passive devices, higher requirements are imposed on dielectric materials in the millimeter-wave band. The material not only needs to have a low dielectric constant to reduce transmission delay and device parasitic effects, but also needs to have ultra-low dielectric loss and a resonance frequency temperature coefficient close to zero to ensure the frequency stability of the device in a complex temperature environment.

[0003] Forsterite (Mg2SiO4) is a typical microwave dielectric ceramic with a low dielectric constant, having advantages such as low dielectric constant, low loss, and low raw material cost, and is an important candidate material for communication devices such as millimeter-wave dielectric resonators and antennas. However, there are two long-standing bottlenecks in this system: firstly, complete densification usually requires a relatively high sintering temperature exceeding 1500 °C; secondly, the resonance frequency temperature coefficient is usually a large negative value, making it difficult to directly meet the requirements of engineering applications for temperature stability. Summary of the Invention

[0004] Aiming at the above-mentioned bottlenecks of the prior art, the present invention proposes a preparation method for Mg 2-x Ga 0.5x Li 0.5x SiO4 microwave dielectric ceramic. By introducing hetero-valent ions to synergistically substitute at the Mg site, the densification temperature of the ceramic is reduced and the microwave dielectric properties are evenly improved, which can be applied to improve the use stability and environmental adaptability of millimeter-wave dielectric resonant antennas, dielectric resonators, filters, or low-dielectric-loss wireless communication devices.

[0005] The technical solution of the present invention is as follows: A microwave dielectric ceramic material suitable for millimeter-wave communication, the chemical formula of the microwave dielectric ceramic material is Mg 2-x Ga 0.5x Li 0.5x SiO4, wherein the Ga and Li elements synergistically substitute the Mg ion sites of forsterite in the form of ions with a molar ratio of 1:1 and different valences; where 0 < x ≤ ۰۰۶, preferably 0 < x ≤ ۰۰۴.

[0006] Its preparation method includes the following steps: (1) Using MgO, Ga2O3, Li2O, and SiO2 as raw materials, according to the target chemical formula Mg2-x Ga 0.5x Li 0.5x Weigh and mix the stoichiometric ratios of Mg, Ga, Li and Si in SiO4; (2) The mixed raw materials obtained in step (1) are subjected to ball milling, drying and pre-calcination for the first time to obtain pre-calcined powder; (3) The pre-calcined powder is ball-milled, dried, ground and sieved for a second time. After adding a binder, it is granulated, sieved and pressed into shape to obtain a green body. (4) The green body obtained in step (3) is debonded and sintered to obtain the microwave dielectric ceramic material.

[0007] As a preferred option, the pre-firing temperature in step (2) is 1100~1150 ℃ to avoid the high pre-firing temperature affecting the performance of the final ceramic.

[0008] As a preferred embodiment, the Ga 3+ / Li + The doping amount x is 0.04, under which the ceramic obtains the optimal microwave dielectric properties.

[0009] Preferably, the dielectric constant of the microwave dielectric ceramic material is 6.8~7.0, Q f The value is 204000~238600GHz@12.8 GHz, and the temperature coefficient of the resonant frequency is -48~-42 ppm / ℃.

[0010] The present invention also provides the application of the microwave dielectric ceramic material in the fabrication of millimeter-wave dielectric resonant antennas, dielectric resonators, filters or low dielectric loss wireless communication devices.

[0011] Compared with the prior art, the present invention has the following beneficial effects: (1) Ga 3+ / Li + Synergistic heterovalent substitution is beneficial for the formation of stable Mg2SiO4 single-phase solid solutions; (2) This substitution strategy can shift the optimal densification temperature of the material from about 1500°C to about 1400°C; (3) While maintaining a low dielectric constant, Q can be significantly improved. f And improve τ f The x=0.04 component exhibits the best overall performance and demonstrates extremely excellent low-loss characteristics in the 24~25 GHz millimeter wave band.

[0012] Existing research has shown that in the field of microwave dielectric ceramics, densification temperature and Q... f Value and temperature coefficient of resonant frequency τ fIt is difficult to establish a simple and stable correspondence between them, and it is usually difficult to achieve simultaneous optimization of the three using conventional processes. Q f The value is quite sensitive to porosity, density, grain growth, volatilization loss, and second phase, and often shows a trend of first increasing and then decreasing with changes in sintering temperature; τ f It is mainly affected by crystal structure, chemical bond characteristics, and phase composition, and is often addressed by introducing positive τ. f The components or second phase can be adjusted, but this type of method is prone to causing Q. f The value decreases. Therefore, the material of this invention not only maintains a single phase, but also synergistically optimizes Q. f Value and make τ f The improvement towards zero value and the potential to reduce densification temperature are not conventional results that are easily obtained in existing technologies, demonstrating good synergistic optimization effects and outstanding performance.

[0013] The material provided by this invention is particularly suitable for millimeter-wave dielectric resonant antennas. Compared with existing technologies, the material of this invention has a lower dielectric constant, which better meets the requirements of antennas for electromagnetic wave propagation characteristics and radiation performance in the millimeter-wave band; at the same time, it has a higher Q... f The value can significantly reduce dielectric loss, thereby improving the radiation efficiency, gain, and signal transmission quality of antenna devices; furthermore, this invention, by making τ f Improving the Q-value towards zero can effectively reduce the sensitivity of the device's resonant frequency to changes in ambient temperature, thereby enhancing the stability and reliability of the antenna's operating frequency band. Especially in applications such as 5G / 6G millimeter-wave communication, point-to-point high-speed backhaul, automotive millimeter-wave radar, and satellite / airborne millimeter-wave communication, the additional losses introduced by the dielectric material are more significant due to the high system operating frequency, sensitivity to transmission loss, and high miniaturization of devices. Therefore, the Q-value of the material is crucial. f This places higher demands on the value. A higher Q... f A certain value helps maintain low dielectric loss in the millimeter-wave band, ensuring high radiation efficiency, gain, and directivity of the antenna, thereby meeting the application requirements of long-distance transmission, weak signal reception, and high-precision detection. At the same time, these application scenarios typically face complex temperature variation environments; if the material τ... f A large deviation from zero can easily lead to antenna resonant frequency drift, impedance matching deterioration, and operating frequency band shift, thereby affecting the stability of communication links, radar detection accuracy, and the long-term consistency of devices.

[0014] Based on the above performance advantages, this invention achieves densification temperature and Q... f value and τ f The synergistic optimization of the device not only improves the overall application performance of the millimeter-wave dielectric resonant antenna, but also has a positive effect on improving the stability and environmental adaptability of the device. Attached Figure Description

[0015] Figure 1 Mg as described in Examples 1-7 of this invention 2-x Ga 0.5x Li 0.5x XRD pattern of SiO4 ceramics sintered at 1400℃; Figure 2 Mg as described in Examples 1-7 of this invention 2-x Ga 0.5x Li 0.5x The relative density of SiO4 ceramics varies with doping concentration; Figure 3 Mg from Examples 1-7 of this invention 2-x Ga 0.5x Li 0.5x Microwave dielectric properties of SiO4 ceramics (Q f Value, dielectric constant εr, temperature coefficient of resonant frequency τ f The variation with doping concentration; Figure 4 Mg from Examples 1-7 of this invention 2-x Ga 0.5x Li 0.5x Microwave dielectric properties of SiO4 ceramics (Q f Value (varying with resonant frequency) Detailed Implementation

[0016] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, all raw materials used are commercially available high-purity reagents, and the processes and testing methods used are conventional methods in the art.

[0017] Example 1: This example is a Mg2SiO4 microwave dielectric ceramic, and the preparation process includes the following steps: Step (1) Raw material proportioning and ball milling: MgO, Ga2O3, Li2O and SiO2 are used as raw materials. Except for MgO, the other raw materials are dried at 85℃; MgO is calcined at 1100℃ for 3 h to remove the influence of impurities. After weighing according to the stoichiometric ratio of Mg2SiO4, ethanol is added and ball milling is carried out once for 24 h with zirconium balls as the ball milling medium, and the ball milling rate is 240 r / min.

[0018] Step (2) Pre-calcination and secondary ball milling: After the first ball milling and drying, the powder is sieved through a 100-mesh standard sieve, then pre-calcined at 1150℃ for 3 hours, and the pre-calcined powder is ball-milled again for 24 hours.

[0019] Step (3) Granulation, pressing and sintering: After secondary ball milling, the sample is dried, passed through a 100-mesh standard sieve, and then granulated with 10 wt% polyvinyl alcohol aqueous solution. It is then pressed into shape at 40-100 MPa. The temperature is then increased to 650℃ at 2℃ / min and held for 3 h to remove the glue. Finally, the temperature is increased to 1400-1550℃ at 4℃ / min and held for 3 h to sinter the sample to obtain the target ceramic sample.

[0020] The XRD pattern of this embodiment 1 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 confirms that it is a single-phase ceramic.

[0021] The relative density of this embodiment 1 is as follows: Figure 2 As shown, the relative density of Mg2SiO4 ceramics is 92%~98%.

[0022] The microwave dielectric properties of this embodiment at the optimal temperature of 1500℃ are as follows: Figure 3 As shown, the dielectric constant is 6.91 and Q is... f The value is 193000 GHz, t f It is -57 ppm / ℃.

[0023] Q in this embodiment 1 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 206700 GHz can be reached at 24.5 GHz.

[0024] Example 2: This example uses Mg 1.99 Ga 0.005 Li 0.005 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: Step (2) is the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.99 Ga 0.005 Li 0.005 SiO4 is weighed, and the sintering temperature range of step (3) is 1350℃~1525℃.

[0025] The XRD pattern of this embodiment 2 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0026] The relative density of this embodiment 2 is as follows: Figure 2 As shown, Mg 1.99 Ga 0.005 Li 0.005 The relative density of SiO4 ceramics is 93%~98%.

[0027] The microwave dielectric properties of Example 2 at the optimal temperature of 1450℃ are as follows: Figure 3 As shown, the dielectric constant is 6.92 and Q is... f The value is 204000 GHz, t f It is -48 ppm / ℃.

[0028] Q in this embodiment 2 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 221000 GHz can be reached at 24.5 GHz.

[0029] Example 3: This example uses Mg 1.98 Ga 0.01 Li 0.01 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: The steps are basically the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.98 Ga 0.01 Li 0.01 SiO4 is weighed. The pre-firing temperature in step (2) is 1125℃, and the sintering temperature range in step (3) is 1350℃~1525℃.

[0030] The XRD pattern of this embodiment 3 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0031] The relative density of this embodiment 3 is as follows: Figure 2 As shown, Mg 1.98 Ga 0.01 Li 0.01 The relative density of SiO4 ceramics is 92.8%~98.5%.

[0032] The microwave dielectric properties of Example 3 at the optimal temperature of 1450℃ are as follows: Figure 3 As shown, the dielectric constant is 6.93 and Q is... f The value is 211000 GHz, t f It is -44 ppm / ℃.

[0033] Q in this embodiment 3 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 242000 GHz can be reached at 24.5 GHz.

[0034] Example 4: This example uses Mg 1.97 Ga 0.015 Li 0.015 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: The steps are basically the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.98 Ga 0.01 Li 0.01 SiO4 is weighed. The pre-firing temperature in step (2) is 1125℃, and the sintering temperature range in step (3) is 1350℃~1525℃.

[0035] The XRD pattern of this embodiment 4 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0036] The relative density of Example 4 is as follows: Figure 2 As shown, Mg 1.97 Ga 0.015 Li 0.015 The relative density of SiO4 ceramics is 93%~97.6%.

[0037] The microwave dielectric properties at the optimal temperature of 1425℃ in Example 4 are as follows: Figure 3 As shown, the dielectric constant is 6.87 and Q is... f The value is 235000 GHz, t f It is -43 ppm / ℃.

[0038] Q in this embodiment 4 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 264,000 GHz can be reached at 24.5 GHz.

[0039] Example 5: This example uses Mg 1.96 Ga 0.02 Li 0.02 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: The steps are basically the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.96 Ga 0.02 Li 0.02 SiO4 is weighed. The pre-firing temperature in step (2) is 1100℃, and the sintering temperature range in step (3) is 1350℃~1525℃.

[0040] The XRD pattern of Example 5 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0041] The relative density of Example 5 is as follows: Figure 2 As shown, Mg 1.96 Ga 0.02 Li 0.02The relative density of SiO4 ceramics is 92.7%~97.1%.

[0042] The microwave dielectric properties of Example 5 at the optimal temperature of 1400℃ are as follows: Figure 3 As shown, the dielectric constant is 6.8 and Q is... f The value is 238600 GHz, t f It is -42 ppm / ℃.

[0043] Q in Example 5 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 295,000 GHz can be reached at 24.5 GHz.

[0044] Example 6: This example uses Mg 1.95 Ga 0.025 Li 0.025 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: The steps are basically the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.95 Ga 0.025 Li 0.025 SiO4 is weighed. The pre-firing temperature in step (2) is 1100℃, and the sintering temperature range in step (3) is 1350℃~1525℃.

[0045] The XRD pattern of Example 6 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0046] The relative density of Example 6 is as follows: Figure 2 As shown, Mg 1.95 Ga 0.025 Li 0.025 The relative density of SiO4 ceramics is 90%~96.4%.

[0047] The microwave dielectric properties of Example 6 at the optimal temperature of 1400℃ are as follows: Figure 3 As shown, the dielectric constant is 6.72 and Q is... f The value is 147000 GHz, t f It is -39.5 ppm / ℃.

[0048] Q in Example 6 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 167,000 GHz can be reached at 24.5 GHz.

[0049] Example 7: This example uses Mg 1.94 Ga 0.03 Li0.03 The preparation process of SiO4 microwave dielectric ceramic includes the following steps: The steps are basically the same as in Example 1, except that the raw material ratio in step (1) is based on the chemical formula Mg 1.94 Ga 0.03 Li 0.03 SiO4 is weighed. The pre-firing temperature in step (2) is 1075℃, and the sintering temperature range in step (3) is 1350℃~1525℃.

[0050] The XRD pattern of Example 7 is as follows: Figure 1 As shown, a comparison with the standard PDF card of Mg2SiO4 indicates that it is a single-phase solid solution.

[0051] The relative density of Example 7 is as follows: Figure 2 As shown, Mg 1.94 Ga 0.03 Li 0.03 The relative density of SiO4 ceramics is 89.5%~96.5%.

[0052] The microwave dielectric properties of this embodiment at the optimal temperature of 1400℃ are as follows: Figure 3 As shown, the dielectric constant is 6.68 and Q is... f The value is 66700 GHz, t f It is -37 ppm / ℃.

[0053] Q in Example 7 f The relationship between the value and the resonant frequency is as follows: Figure 4 As shown, it can be seen that 85400 GHz can be reached at 24.5 GHz.

[0054] Appendix Figure 1 Different Mg compositions are given 2-x Ga 0.5x Li 0.5x The diffraction peaks of the SiO4 sample can all be attributed to the orthorhombic Mg2SiO4 olivine structure, and no obvious second phase was detected, indicating that Ga 3+ / Li + It can enter the Mg site to form a single-phase solid solution.

[0055] Appendix Figure 2 The relative density of each component sample changes with sintering temperature. The relative density of each component sample generally increases first and then decreases with increasing sintering temperature, indicating that the system has a clear optimal densification temperature window. Compared with the unsubstituted sample, the Ga of this invention... 3+ / Li + The optimal densification temperature shifts forward overall after synergistic heterovalent substitution.

[0056] Appendix Figure 3The figure shows the microwave dielectric properties of the Ga alloy at the optimal sintering temperature for each embodiment. 3+ / Li + With appropriate substitution, its microwave dielectric properties can be improved.

[0057] Appendix Figure 4 Q is the value of each embodiment at different resonant frequencies. f Performance, Example 5, Q at around 24.5 GHz f The result of up to 294,600 GHz indicates that the material of this invention has excellent low-loss characteristics in the millimeter-wave band around 24.5 GHz, making it suitable for devices such as dielectric resonator antennas, dielectric resonators, and filters for millimeter-wave communication.

Claims

1. A microwave dielectric ceramic material suitable for millimeter-wave communication, characterized in that, The chemical formula of the microwave dielectric ceramic material is Mg 2-x Ga 0.5x Li 0.5x SiO4, where 0 < x ≤ 0.

06. The Ga and Li elements co-substitute the Mg ion sites of forsterite in the form of ions with a molar ratio of 1:1 and different valence states.

2. The microwave dielectric ceramic material suitable for millimeter-wave communication according to claim 1, characterized in that, The microwave dielectric ceramic material has the chemical formula Mg. 2-x Ga 0.5x Li 0.5x SiO4, where 0 <x≤0.04。 3. The microwave dielectric ceramic material according to claim 2, characterized in that, The dielectric constant of the microwave dielectric ceramic material is 6.8~7.0, Q f The value is 204000~238600 GHz @12.8 GHz, and the temperature coefficient of the resonant frequency is -48~-42ppm / °C.

4. The microwave dielectric ceramic material according to claim 2, characterized in that, The microwave dielectric ceramic material exhibits the following microwave dielectric properties (Q) in the 24–25 GHz millimeter-wave band: f The values ​​reach 221000~295000 GHz, the dielectric constant is 6.7~7.0, and the temperature coefficient of resonant frequency is -48~-42 ppm / °C.

5. A method for preparing a microwave dielectric ceramic material as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Using MgO, Ga2O3, Li2O and SiO2 as raw materials, according to the target chemical formula Mg 2-x Ga 0.5x Li 0.5x The stoichiometric ratios of Mg, Ga, Li and Si in SiO4 were weighed and mixed to obtain a mixed raw material; (2) The mixed raw materials obtained in step (1) are subjected to ball milling, drying and pre-calcination for the first time to obtain pre-calcined powder; (3) The pre-calcined powder is ball-milled, dried, ground and sieved for the second time. After adding a binder, it is granulated, sieved and pressed into shape to obtain a green body. (4) The green body obtained in step (3) is debonded and sintered to obtain the microwave dielectric ceramic material.

6. The preparation method according to claim 5, characterized in that, Before weighing the material as described in step (1), the following pretreatment steps are also included: For raw materials other than MgO, use them after drying at 85 °C; For use after calcining MgO at 1100 °C for 3 h; In both steps (2) and (3), ethanol was used as the medium and zirconium balls were used as the milling medium. The milling time was 24 h and the milling rate was 240 r / min.

7. The preparation method according to claim 5, characterized in that, The pre-calcination temperature is 1100~1150 °C, and the holding time is 3 h; the granulation uses a 10 wt% polyvinyl alcohol aqueous solution as a binder, which is first passed through a 100-mesh sieve and then through a 60-mesh sieve.

8. The preparation method according to claim 5, characterized in that, The molding pressure is 40~100 MPa; the glue removal specifically includes heating to 650 °C at 2 °C / min and holding at that temperature for 3 h.

9. The preparation method according to claim 5, characterized in that, The sintering process specifically involves heating to 1350~1550 °C at a rate of 4 °C / min and holding for 3 h, then cooling to 800 °C at a rate of 2 °C / min and then cooling with the furnace.

10. The use of the microwave dielectric ceramic material according to any one of claims 1 to 4 in the fabrication of millimeter-wave dielectric resonant antennas, dielectric resonators, filters, or low dielectric loss wireless communication devices.

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