A medium-entropy microwave dielectric ceramic with a garnet structure and a preparation method thereof
By doping Co, Cu, Mg and Zn ions into the garnet structure, Ca3(Co0.25Cu0.25Mg0.25Zn0.25)2SiV2O12 microwave dielectric ceramics were prepared, which solved the problem of insufficient performance of existing microwave dielectric ceramics and realized the preparation of high-performance microwave dielectric ceramics suitable for millimeter-wave communication.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ANHUI UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2024-06-28
- Publication Date
- 2026-04-28
AI Technical Summary
Existing microwave dielectric ceramics cannot simultaneously meet the requirements of high relative permittivity, quality factor, and near-zero temperature coefficient of resonant frequency. Single-phase microwave dielectric ceramics have performance deficiencies and cannot meet the high-performance requirements of the 5G/6G communication era.
Using the concept of medium-entropy ceramics, Ca3(Co0.25Cu0.25Mg0.25Zn0.25)2SiV2O12 microwave dielectric ceramics were prepared by doping Co, Cu, Mg and Zn ions into the garnet structure and combining it with the traditional solid-state sintering method. The sintering temperature and process parameters were optimized to improve performance.
Microwave dielectric ceramics with dielectric constants of 8.1–10.9, quality factors of 23490–59200 GHz, and temperature coefficients of resonant frequencies of -11.2–-9.2 ppm/℃ have been developed, showing promising prospects for millimeter-wave communication applications. Furthermore, the process is simple and the cost is low.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of dielectric ceramics technology, specifically to a medium-entropy microwave dielectric ceramic with a garnet structure and its preparation method. Background Technology
[0002] Currently, microwave dielectric ceramics are widely used in wireless communication products, such as mobile phones, communication base stations, GPS, and WLAN. The advent of the 5G / 6G communication era places even higher performance demands on microwave dielectric ceramics. Corresponding electronic components should possess appropriate relative permittivity, a high quality factor (Q×f≥20000GHz), and a near-zero temperature coefficient of resonant frequency (-10ppm / ℃≤τ). f ≤10ppm / ℃). Since the signal transmission rate is inversely proportional to the square root of the relative permittivity of the dielectric material, a low relative permittivity can reduce the interaction coupling loss between the material and the electrode and increase the transmission rate of the electrical signal; while the higher the frequency, the lower the material loss is required. Therefore, a high Q×f value is beneficial to improving the selectivity of the device's operating frequency and simplifying the heat dissipation structure design. A near-zero resonant frequency temperature coefficient can ensure the operating stability of electronic components. Therefore, developing new low relative permittivity (ε) is crucial. r <15), high Q×f value and near-zero τ f Microwave dielectric ceramics have gradually become a research hotspot. Currently, it is difficult for single-phase microwave dielectric ceramics to simultaneously meet the above three properties, and how to design high-performance microwave dielectric ceramic systems remains a significant challenge.
[0003] Inspired by high-entropy alloys, researchers first proposed the concept of high-entropy oxides in 2015 and successfully prepared (Mg) oxides with a rock-salt structure. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 High-entropy ceramics were initially composed of O-type ceramics. Subsequently, the composition of high-entropy ceramics gradually expanded to include carbides, borides, silicates, etc. In recent years, research has found that stable oxides can also be formed when a lattice site is occupied by three or four ions; these ceramics are called medium-entropy ceramics. Currently, research on medium-entropy oxide ceramics mainly focuses on their optical, electrical, and thermal conductivity properties.
[0004] Garnet has a loose structure with abundant substitutable lattice sites, which facilitates the introduction of a large number of cations to modulate its functional properties. After the high-entropy effect was introduced into microwave dielectric ceramics, the selectivity of components and the diversity of properties provided a new approach for the performance regulation of microwave dielectric ceramics. However, the application research of medium-entropy ceramics in the field of microwave dielectrics has not yet been reported.
[0005] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention
[0006] The purpose of this invention is to solve the problem of how to design a high-performance microwave dielectric ceramic system with appropriate relative permittivity, high quality factor and near-zero resonant frequency temperature coefficient, and to provide a medium-entropy microwave dielectric ceramic with garnet structure and its preparation method.
[0007] To achieve the above objectives, this invention discloses a method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure, comprising the following steps:
[0008] S1. The required raw materials CaCO3, CoO, CuO, MgO, ZnO, SiO2 and V2O5 are all dried before weighing;
[0009] S2, according to Ca3(Co) 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The chemical formula is obtained by weighing the starting materials CaCO3, CoO, CuO, MgO, ZnO, SiO2 and V2O5, ball milling the resulting mixed powder with anhydrous ethanol, drying the slurry-like raw material to constant weight, and finally sieving to obtain a uniformly dried raw material mixed powder.
[0010] S3 involves calcining the raw material mixture into powder, followed by a reaction to obtain Ca3(Co)2. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The calcined powder was ball-milled twice with anhydrous ethanol to form a uniformly dispersed slurry. This slurry was then dried to constant weight and finally sieved to obtain uniformly dried Ca3(Co) powder. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Pre-formed powder;
[0011] S4, the pre-made powder is added to a PVA aqueous solution and granulated, then pressed into a ceramic green body. Subsequently, the green body is debinded and sintered to obtain Ca3(Co)2. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Medium-entropy microwave dielectric ceramics.
[0012] In step S1, the drying temperature is 80℃ and the drying time is 24h.
[0013] In both steps S2 and S3, yttrium-toughened zirconia balls are used for ball milling, and the mass ratio of raw material, anhydrous ethanol and yttrium-toughened zirconia balls is 1:2:4. The ball milling time is 12 hours and the ball mill speed is 300 r / min.
[0014] In steps S2 and S3, the drying temperature is 80℃, the drying time is 24h, and a 100-mesh sieve is used for sieving.
[0015] In step S3, the calcination temperature is 950℃, the holding time is 8h, the heating rate is 5℃ / min, and the furnace is cooled to room temperature after calcination.
[0016] In step S4, the mass fraction of the PVA aqueous solution is 5%, and the amount of PVA aqueous solution added is 6% of the mass of the pre-made powder.
[0017] In step S4, the tablet is pressed using dry pressing technology, with a pressure of 150 MPa and a holding time of 2 to 3 minutes.
[0018] In step S4, the diameter of the blank is 10 mm and the height is 5-6 mm.
[0019] In step S4, the temperature for debinding is 600℃, the heating rate is 1℃ / min, and the holding time is 2h. After debinding, the sintering process continues at a temperature of 970~1050℃, a heating rate of 5℃ / min, and a holding time of 8h. After sintering, the furnace is cooled to room temperature.
[0020] This invention also discloses a medium-entropy microwave dielectric ceramic with a garnet structure prepared by the above-described method, wherein the chemical formula of the medium-entropy microwave dielectric ceramic is Ca3(Co) 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The medium-entropy microwave dielectric ceramic has a dielectric constant of 8.1 to 10.8, a quality factor of 23490 to 59200 GHz, and a resonant frequency temperature coefficient of -11.2 to -9.2 ppm / ℃.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0022] 1. Based on the unique effect of medium entropy, the concept of medium entropy was introduced into garnet structure microwave dielectric ceramics for the first time. By optimizing the sintering temperature, a medium entropy microwave dielectric ceramic with garnet structure was successfully synthesized.
[0023] 2. Medium-entropy microwave dielectric ceramics have low sintering temperature, uniform microstructure, and a relative density of up to 95%.
[0024] 3. Medium-entropy microwave dielectric ceramics have a dielectric constant of 8.1 to 10.9, a quality factor of 23490 to 59200 GHz, and a resonant frequency temperature coefficient of -11.2 to -9.2 ppm / ℃, showing good application prospects in the field of millimeter-wave communication.
[0025] 4. This invention adopts the traditional solid-state sintering method, which has a simple preparation process, short preparation cycle, strong reproducibility, and low material cost, and has important industrial application value. Attached Figure Description
[0026] Figure 1 Ca3Co2SiV2O 12 SEM images of the ceramic matrix at 1050-1150℃;
[0027] Figure 2 Ca3Co2SiV2O 12 Density and microwave dielectric properties of the matrix ceramic;
[0028] Figure 3 The relative density diagrams are for the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention.
[0029] Figure 4 X-ray diffraction patterns and Rietveld structure refinement images at 1010℃ of the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention are shown; wherein (a) is the X-ray diffraction pattern of Examples 1-5, and (b) is the Rietveld structure refinement image at 1010℃.
[0030] Figure 5 SEM images of medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention; where (a) is Example 1, (b) is Example 2, (c) is Example 3, (d) is Example 4, and (e) is Example 5.
[0031] Figure 6 EDS mapping at 1010℃;
[0032] Figure 7 The following are histograms showing the grain size distribution of the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 2-5 of this invention; where (a) is Example 2, (b) is Example 3, (c) is Example 4, and (d) is Example 5. Detailed Implementation
[0033] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.
[0034] Due to Ca3Co2SiV2O 12 The narrow sintering temperature range of the matrix ceramic and the existence of inconsistent melting phenomena prevent the preparation of dense ceramics and the achievement of excellent microwave dielectric properties by further increasing the sintering temperature. To solve this technical challenge, the inventors attempted to simultaneously dope the B site with four cations (Co, Cu, Mg, and Zn) to form a higher configurational entropy, thereby obtaining superior microwave dielectric properties.
[0035] Example 1
[0036] Ca3(Co) with garnet structure 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Medium-entropy microwave dielectric ceramics and their preparation methods, the preparation process includes the following steps:
[0037] Step (1) Weighing: Weigh CaCO3, CoO, CuO, MgO, ZnO, SiO2, and V2O5 (all with a purity greater than 99%) according to the chemical formula Ca3(Co) 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Weigh.
[0038] Step (2) First ball milling: The weighed raw materials CaCO3, CoO, CuO, MgO, ZnO, SiO2 and V2O5 are placed in a nylon ball mill jar, and anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mixture is ball milled in a planetary ball mill for 8 hours.
[0039] Step (3) Calcination: The ball-milled mixed slurry is placed in an 80℃ oven and dried for 12 hours. The dried powder is then ground and calcined at 950℃ for 8 hours at a heating rate of 5℃ / min. After that, it is cooled to room temperature with the furnace.
[0040] Step (4) Secondary ball milling: After appropriate grinding of the calcined powder, secondary ball milling is carried out. The specific process is the same as the first ball milling.
[0041] Step (5) Molding: Place the ball-milled mixed slurry into an 80℃ oven and dry for 12 hours. Place the dried powder in an agate mortar and add 5wt% PVA aqueous solution. After the powder and PVA aqueous solution are mixed evenly, pass it through a 100-mesh standard sieve. Pour the granulated powder into a steel mold and press it into a cylindrical blank with a diameter of about 10mm and a height of about 5-6mm.
[0042] Step (6) Sintering: Heat to 600℃ at a heating rate of 1℃ / min, hold for 2h to remove the binder, then heat to 970℃ at a heating rate of 5℃ / min, and finally cool to room temperature with the furnace to obtain the microwave dielectric ceramic sample.
[0043] In this embodiment, the relative density after sintering is 72.9%, the dielectric constant is 8.1, the quality factor is 23490 GHz, and the temperature coefficient of the resonant frequency is -11.2 ppm / ℃.
[0044] Example 2
[0045] Steps (1) to (6) are the same as in Example 1. The difference is that in this example, the sintering process in step (6) is as follows: the temperature is raised to 600°C at a heating rate of 1°C / min, and the temperature is held for 2 hours to remove the binder. Then the temperature is raised to 990°C at a heating rate of 5°C / min, and finally cooled to room temperature with the furnace to obtain the microwave dielectric ceramic sample.
[0046] In this embodiment, the relative density after sintering is 86.4%, the dielectric constant is 9.8, the quality factor is 31570 GHz, and the temperature coefficient of the resonant frequency is -9.8 ppm / ℃.
[0047] Example 3
[0048] Steps (1) to (6) are the same as in Example 1. The difference is that in this example, the sintering process in step (6) is as follows: the temperature is raised to 600°C at a heating rate of 1°C / min, and the temperature is maintained for 2 hours to remove the binder. Then the temperature is raised to 1010°C at a heating rate of 5°C / min, and finally cooled to room temperature with the furnace to obtain the microwave dielectric ceramic sample.
[0049] In this embodiment, the relative density after sintering is 95.2%, the dielectric constant is 10.9, the quality factor is 59200 GHz, and the temperature coefficient of the resonant frequency is -9.6 ppm / ℃.
[0050] Example 4
[0051] Steps (1) to (6) are the same as in Example 1. The difference is that in this example, the sintering process in step (6) is as follows: the temperature is raised to 600°C at a heating rate of 1°C / min, and the temperature is held for 2 hours to remove the binder. Then the temperature is raised to 1030°C at a heating rate of 5°C / min, and finally cooled to room temperature with the furnace to obtain the microwave dielectric ceramic sample.
[0052] In this embodiment, the relative density after sintering is 94.5%, the dielectric constant is 10.8, the quality factor is 54390 GHz, and the temperature coefficient of the resonant frequency is -9.2 ppm / ℃.
[0053] Example 5
[0054] Steps (1) to (6) are the same as in Example 1. The difference is that in this example, the sintering process in step (6) is as follows: the temperature is raised to 600°C at a heating rate of 1°C / min, and the temperature is held for 2 hours to remove the binder. Then the temperature is raised to 1050°C at a heating rate of 5°C / min. Finally, the temperature is cooled to room temperature with the furnace to obtain the microwave dielectric ceramic sample.
[0055] In this embodiment, the relative density after sintering is 93.6%, the dielectric constant is 10.6, the quality factor is 50030 GHz, and the temperature coefficient of the resonant frequency is -10.3 ppm / ℃.
[0056] Figure 1 Ca3Co2SiV2O 12 SEM images of the ceramic matrix; from Figure 1 It can be seen that Ca3Co2SiV2O 12 When the sintering temperature of the matrix ceramic is between 1050-1100℃, the density is poor. When the temperature is further increased, melting begins to occur.
[0057] Figure 2 Ca3Co2SiV2O 12 Density and microwave dielectric properties of the matrix ceramic; affected by density, Ca3Co2SiV2O 12 The substrate ceramic did not exhibit good microwave dielectric properties, with quality factors all below 25000GHz and relatively large temperature coefficients of resonant frequency, which is not conducive to practical applications.
[0058] Figure 3 The relative density diagrams are for the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention; from Figure 3 It can be seen that the synthesized medium-entropy ceramic has a maximum relative density of 95.2%, which is significantly improved compared to the matrix ceramic.
[0059] Figure 4 The X-ray diffraction patterns are shown for the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention; from Figure 4 As can be seen, the synthesized medium-entropy ceramics are all pure phases, with no second phase generated.
[0060] Figure 5 These are SEM images of the medium-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention. Figure 6 EDS mapping plot at 1010℃; from Figure 5 As can be seen, the medium-entropy ceramics synthesized in Examples 2-5 have clear grain boundaries, relatively uniform size, high density, and no melting phenomenon; from Figure 6 It can be seen that the elements are evenly distributed at the optimal sintering temperature.
[0061] Figure 7 This is a histogram of the grain size distribution of the medium-entropy microwave dielectric ceramics with garnet structure prepared in Examples 2-5 of this invention; from Figure 7 It can be seen that the grain size first increases and then decreases with increasing temperature. The grain size in Example 4 is the largest, which helps to improve the quality factor of the medium-entropy ceramic.
[0062] Table 1 shows the microwave performance data of the garnet-structured medium-entropy microwave dielectric ceramics prepared in Examples 1-5 of this invention. As can be seen from Table 1, the Ca3(Co)3-carbide ceramics with garnet structures prepared in Examples 1-5 of this invention exhibit... 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The dielectric constants of the medium-entropy ceramics obtained at different sintering temperatures ranged from 8.1 to 10.9, classifying them as low-dielectric-constant ceramics. The ceramic prepared in Example 3 at the optimal sintering temperature exhibited a quality factor of 59200 GHz, demonstrating low dielectric loss. Furthermore, the ceramic prepared in Example 3 at the optimal sintering temperature showed a resonant frequency temperature coefficient of -9.6 ppm / ℃, exhibiting high temperature stability. Compared to the matrix ceramic, the quality factor was significantly improved, and the resonant frequency temperature coefficients were all around -10 ppm / ℃, meeting practical application requirements. The microwave dielectric properties demonstrate that the Ca3(Co) of this invention... 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Medium-entropy microwave dielectric ceramics have promising applications in the field of millimeter-wave wireless communication.
[0063] Table 1. Microwave performance data of the medium-entropy microwave dielectric ceramics with garnet structure prepared in Examples 1-5 of this invention.
[0064] Temperature (°C) 970 990 1010 1030 1050 Dielectric constant 8.1 9.8 10.9 10.8 10.6 Quality factor (GHz) 23490 31570 59200 54390 50030 Temperature coefficient of resonant frequency (ppm / °C) -11.2 -9.8 -9.6 -9.2 -10.3
[0065] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.
Claims
1. A method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure, characterized in that, Includes the following steps: S1. The required raw materials CaCO3, CoO, CuO, MgO, ZnO, SiO2 and V2O5 are dried before weighing; S2, according to Ca3(Co) 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The chemical formula is obtained by weighing the starting materials CaCO3, CoO, CuO, MgO, ZnO, SiO2 and V2O5, ball milling the resulting mixed powder with anhydrous ethanol, drying the slurry-like raw material to constant weight, and finally sieving to obtain a uniformly dried raw material mixed powder. S3 involves calcining the raw material mixture into powder, followed by a reaction to obtain Ca3(Co)2. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The calcined powder was ball-milled twice with anhydrous ethanol to form a uniformly dispersed slurry. This slurry was then dried to constant weight and finally sieved to obtain uniformly dried Ca3(Co) powder. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Pre-formed powder; S4, the pre-made powder is added to a PVA aqueous solution and granulated, then pressed into a ceramic green body. Subsequently, the green body is debinded and sintered to obtain Ca3(Co)2. 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 Medium-entropy microwave dielectric ceramics.
2. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S1, the drying temperature is 80℃ and the drying time is 24h.
3. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In both steps S2 and S3, yttrium-toughened zirconia balls are used for ball milling, and the mass ratio of raw material, anhydrous ethanol and yttrium-toughened zirconia balls is 1:2:
4. The ball milling time is 12 hours and the ball mill speed is 300 r / min.
4. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In steps S2 and S3, the drying temperature is 80℃, the drying time is 24h, and a 100-mesh sieve is used for sieving.
5. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S3, the calcination temperature is 950℃, the holding time is 8h, the heating rate is 5℃ / min, and the furnace is cooled to room temperature after calcination.
6. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S4, the mass fraction of the PVA aqueous solution is 5%, and the amount of PVA aqueous solution added is 6% of the mass of the pre-made powder.
7. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S4, the tablet is pressed using dry pressing technology, with a pressure of 150 MPa and a holding time of 2 to 3 minutes.
8. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S4, the diameter of the blank is 10 mm and the height is 5-6 mm.
9. The method for preparing a medium-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S4, the temperature for debinding is 600℃, the heating rate is 1℃ / min, and the holding time is 2h. After debinding, the sintering process continues at a temperature of 970~1050℃, a heating rate of 5℃ / min, and a holding time of 8h. After sintering, the furnace is cooled to room temperature.
10. A medium-entropy microwave dielectric ceramic with a garnet structure prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The chemical formula of the medium-entropy microwave dielectric ceramic is Ca3(Co). 0.25 Cu 0.25 Mg 0.25 Zn 0.25 )2SiV2O 12 The medium-entropy microwave dielectric ceramic has a dielectric constant of 8.1 to 10.8, a quality factor of 23490 to 59200 GHz, and a resonant frequency temperature coefficient of -11.2 to -9.2 ppm / ℃.