Low-die high-entropy microwave dielectric ceramic with garnet structure and preparation method thereof

Abstract

This invention relates to the field of dielectric ceramics technology, specifically to a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure and its preparation method. The chemical composition formula of the low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure is Ca. 3 (Co 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 ) 2 SiV 2 O 12 By introducing the high-entropy effect into the garnet structure and optimizing the sintering temperature, a Ca with a garnet structure was successfully synthesized. 3 (Co 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 ) 2 SiV 2 O 12 Pure-phase low-dielectric-high-entropy microwave dielectric ceramics. They exhibit a dielectric constant of 6.5–10.4, a quality factor of 12490–62440 GHz, and a temperature coefficient of resonant frequency of -9.2–-7.4 ppm / ℃. These ceramics possess excellent microwave dielectric properties and have significant practical application value.

Description

A low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure and its preparation method Technical Field

[0001] This invention relates to the field of dielectric ceramics technology, specifically to a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure and its preparation method. Background Technology

[0002] Microwave frequencies, due to their high transmission speed and large communication capacity, have become an important component of mobile communications. With the continuous increase in the number of mobile communication device users, higher demands are being placed on microwave dielectric ceramics used in microwave components. As a functional material, microwave dielectric ceramics, in addition to possessing certain physical properties, must also possess certain microwave dielectric properties. Specifically, a high relative permittivity enables component miniaturization but reduces transmission rates. Therefore, in the field of high-frequency communications, it is necessary to develop microwave dielectric ceramics with low relative permittivity (hereinafter referred to as low dielectric). In recent years, ε... r Low-dielectric microwave ceramics with a dielectric constant of <15 are gradually becoming a research hotspot. They also need to possess a high quality factor (Q×f≥20000GHz) to improve the selectivity of component operating frequencies and simplify heat dissipation structure design; and a near-zero resonant frequency temperature coefficient (-10ppm / ℃≤τ). f ≤10ppm / ℃), thus ensuring the operational stability of electronic components. However, very few single-phase ceramics can simultaneously meet all three performance requirements, and developing high-performance microwave dielectric ceramics using novel design concepts remains a significant challenge.

[0003] With the research on high-entropy alloys, the concept of high entropy has gradually been introduced into ceramic materials, evolving into high-entropy ceramics. These ceramics have a lattice site occupied by five or more cations, exhibiting high configurational entropy and displaying excellent mechanical, energy storage, electrical, and magnetic properties. A patent (CN 115536373 B) has been published demonstrating the use of the high-entropy effect to prepare a (Mg) alloy with an orthoclase structure. 0.2 Co 0.2 Ni 0.2 Cu 0.2 Zn 0.2 SiO3 is a low-dielectric, high-entropy ceramic with excellent microwave dielectric properties, ε r The dielectric constant is 6.5–6.9, and the dielectric loss is 0.0001–0.0004 @ 10 GHz. f The concentration ranges from -40 to -24.5 ppm / ℃. Although this application utilizes the high-entropy effect to suppress the crystal transformation of MgSiO3 ceramics and lower the densification sintering temperature, its τ... f The value is still too large, making it difficult to meet practical applications.

[0004] Compared to orthoclase, garnet has a more complex structure, making the synthesis of single-phase garnet compounds more difficult. Currently, Ca3M2SiV2O obtained using solid-state synthesis methods... 12 All (M = Mg, Cu, Zn) contain a second phase, which severely affects the microwave dielectric properties of ceramics. If the high entropy effect can be utilized to introduce multiple cations into the same lattice position in the garnet structure to form a single-phase material, it will open up new avenues for the regulation of the microwave dielectric properties of microwave dielectric ceramics with garnet structures.

[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 obtaining Ca3M2SiV2O by solid-state synthesis. 12 The presence of a second phase in (M=Mg,Cu,Zn) ceramics severely affects their microwave dielectric properties. To address this issue, a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure and its preparation method are provided.

[0007] To achieve the above objectives, this invention discloses a method for preparing low-dielectric-high-entropy microwave dielectric ceramics with a garnet structure, comprising the following steps:

[0008] S1, based on the target substance Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 The raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2 and V2O5 were weighed according to the molar ratio of their elemental composition and ball-milled with anhydrous ethanol to obtain a mixed slurry.

[0009] S2, the mixed slurry is dried and then pre-calcined, followed by secondary ball milling and drying to obtain dry Ca3(Co)2. 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 Pre-formed powder;

[0010] S3, PVA aqueous solution is added to the dry pre-made powder for granulation, and the powder is sieved to obtain uniform powder, which is then pressed into ceramic blanks;

[0011] S4, the ceramic green body is debinded and sintered to obtain Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2Ni 0.2 )2SiV2O 12 High-entropy microwave dielectric ceramics.

[0012] In step S1, the purity of the raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2 and V2O5 are all ≥99%, and they need to be dried in an oven at 100℃ for 12 hours before being weighed.

[0013] In step S2, the drying temperature is 80℃ and the drying time is 12h.

[0014] In step S2, the pre-firing temperature is 950℃, the holding time is 8h, the heating rate is 5℃ / min, and the furnace is cooled to room temperature after the pre-firing.

[0015] In steps S1 and S2, 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 8 hours and the ball mill speed is 300 r / min.

[0016] In step S3, a 100-mesh sieve is used for sieving.

[0017] In step S3, the concentration of the PVA aqueous solution is 5%, and the amount of PVA aqueous solution added is 7% of the mass of the pre-made powder.

[0018] In step S3, the tablet is pressed using dry pressing technology, under a pressure of 200MPa for 2-3 minutes, with a blank diameter of 10mm and a height of 5-6mm.

[0019] In step S4, the temperature for debinding is 600℃, the heating rate is 2℃ / min, and the holding time is 2h. After debinding, the sintering process continues at a temperature of 990~1070℃, 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 low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure prepared by the above-described method, wherein the chemical formula of the high-entropy microwave dielectric ceramic is Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12The high-entropy microwave dielectric ceramic has a dielectric constant of 6.5 to 10.4, a quality factor of 12490 to 62440 GHz, and a resonant frequency temperature coefficient of -9.2 to -7.4 ppm / ℃. It is composed of five metal elements in equal molar ratios of Co, Cu, Mg, Zn and Ni occupying the B site, forming a high configurational entropy.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention uses five metal elements in equal molar ratio to occupy the B-site positions of the garnet structure, forming a high configurational entropy. Then, by optimizing the sintering temperature, a low dielectric high entropy microwave dielectric ceramic with a garnet structure is successfully synthesized.

[0023] 2. Compared with traditional garnet structure ceramics, the high-entropy microwave dielectric ceramic of this invention has a lower sintering temperature, a relative density of up to 96.5%, a dielectric constant of 6.5 to 10.4, a quality factor of 12490 to 62440 GHz, and a resonant frequency temperature coefficient of -9.2 to -7.4 ppm / ℃. It has excellent microwave dielectric properties and has good application prospects in the field of high-frequency communication. Attached Figure Description

[0024] Figure 1 shows Ca3Co2SiV2O 12 Microscopic images of real-time sintering of the matrix ceramic;

[0025] Figure 2 shows Ca3Co2SiV2O 12 Density and microwave dielectric properties of the matrix ceramic;

[0026] Figure 3 shows the relative density and bulk density of the high-entropy microwave dielectric ceramics with garnet structure prepared in Examples 1-5 of this invention.

[0027] Figure 4 shows the X-ray diffraction patterns of the high-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of the present invention and the Rietveld structure refinement pattern of the ceramics sintered at 1050℃; wherein (a) is the X-ray diffraction pattern of Examples 1-5 and (b) is the Rietveld structure refinement pattern at 1050℃.

[0028] Figure 5 shows the Raman spectra of the high-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.

[0029] Figure 6 shows the microwave performance of the high-entropy microwave dielectric ceramics with garnet structure prepared in Examples 1-5 of this invention; (a) is the dielectric constant (ε). r (b) represents the temperature coefficient of the resonant frequency (τ). f(c) is the quality factor (Q×f). Detailed Implementation

[0030] 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.

[0031] Quality factor and temperature coefficient of resonant frequency, as important evaluation parameters of microwave dielectric ceramics, are influenced to some extent by density. Sintering temperature is one of the most important factors affecting density, and Ca3Co2SiV2O 12 Due to the narrow sintering temperature range, matrix ceramics cannot achieve satisfactory density (relative density needs to be above 95%). To solve this technical challenge, the inventors attempted to simultaneously dope the B site with five cations (Co, Cu, Mg, Zn, and Ni) to form a high configurational entropy, thereby obtaining superior microwave dielectric properties.

[0032] Example 1

[0033] Ca3(Co) with garnet structure 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 High-entropy microwave dielectric ceramics and their preparation methods, the preparation process includes the following steps:

[0034] S1: Mix the raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2, and V2O5 (all with a purity ≥ 99%) according to the chemical formula Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 Weigh.

[0035] S2: The weighed raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2 and V2O5 are placed into a nylon ball mill jar for ball milling once. Anhydrous ethanol and yttrium oxide toughened zirconia balls are added as ball milling media, and the mixture is ball milled in a planetary ball mill for 8 hours.

[0036] S3: Place the ball-milled mixed slurry into an 80℃ oven and dry it for 12 hours. Grind the dried powder and calcine it at 950℃ for 8 hours at a heating rate of 5℃ / min. Then cool it to room temperature with the furnace.

[0037] S4: After the calcined powder is properly ground and there is no obvious agglomeration, it is then ball-milled a second time. The specific process is the same as the first ball milling.

[0038] S5: Place the mixed slurry after secondary ball milling into an 80℃ oven and dry for 12 hours. Place the dried powder in an agate mortar, add 7wt% PVA aqueous solution, and grind thoroughly to ensure that the powder and PVA aqueous solution are evenly mixed. Then pass the mixture 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.

[0039] S6: Heat to 600℃ at a heating rate of 2℃ / min, hold for 2 hours to remove the binder, then heat to 990℃ at a heating rate of 5℃ / min, and finally cool to room temperature with the furnace to obtain the microwave dielectric ceramic sample.

[0040] In this embodiment, the relative density after sintering is 56.8%, the dielectric constant is 6.5, the quality factor is 15490 GHz, and the temperature coefficient of the resonant frequency is -9.2 ppm / ℃.

[0041] Example 2

[0042] The sintering process in this example is as follows: the temperature is increased to 600°C at a heating rate of 2°C / min, held at that temperature for 2 hours to remove the binder, and then increased to 1010°C at a heating rate of 5°C / min. Finally, the temperature is cooled to room temperature in the furnace to obtain the microwave dielectric ceramic sample. The remaining steps are the same as in Example 1.

[0043] In this embodiment, the relative density after sintering is 63.8%, the dielectric constant is 7.1, the quality factor is 21690 GHz, and the temperature coefficient of the resonant frequency is -8.8 ppm / ℃.

[0044] Example 3

[0045] The sintering process in this example is as follows: the temperature is increased to 600°C at a heating rate of 2°C / min, held at that temperature for 2 hours to remove the binder, and then increased to 1030°C at a heating rate of 5°C / min. Finally, the temperature is cooled to room temperature in the furnace to obtain the microwave dielectric ceramic sample. The remaining steps are the same as in Example 1.

[0046] In this embodiment, the relative density after sintering is 85.6%, the dielectric constant is 9.1, the quality factor is 47450 GHz, and the temperature coefficient of the resonant frequency is -7.9 ppm / ℃.

[0047] Example 4

[0048] The sintering process in this example is as follows: the temperature is increased to 600°C at a heating rate of 2°C / min, held at that temperature for 2 hours to remove the binder, and then increased to 1050°C at a heating rate of 5°C / min. Finally, the temperature is cooled to room temperature in the furnace to obtain the microwave dielectric ceramic sample. The remaining steps are the same as in Example 1.

[0049] In this embodiment, the relative density after sintering is 96.5%, the dielectric constant is 10.7, the quality factor is 62440 GHz, and the temperature coefficient of the resonant frequency is -7.4 ppm / ℃.

[0050] Example 5

[0051] The sintering process in this example is as follows: the temperature is increased to 600°C at a heating rate of 2°C / min, held at that temperature for 2 hours to remove the binder, and then increased to 1070°C at a heating rate of 5°C / min. Finally, the temperature is cooled to room temperature in the furnace to obtain the microwave dielectric ceramic sample. The remaining steps are the same as in Example 1.

[0052] In this embodiment, the relative density after sintering is 94.3%, the dielectric constant is 10.4, the quality factor is 58960 GHz, and the temperature coefficient of the resonant frequency is -7.7 ppm / ℃.

[0053] Figure 1 shows Ca3Co2SiV2O 12 Microscopic image of real-time sintering of the matrix ceramic; As can be seen from Figure 1, the sintering temperature of the matrix ceramic is too narrow and there is inconsistent melting phenomenon.

[0054] Figure 2 shows Ca3Co2SiV2O 12 Density and microwave dielectric properties of the matrix ceramic; As can be seen from Figure 2, within the existing sintering temperature range, the density of the material is low, and the microwave properties of the matrix ceramic are significantly affected by the sintering temperature and are not ideal.

[0055] Figure 3 shows the relative density and bulk density of the high-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention. As can be seen from Figure 3, the synthesized high-entropy ceramics achieved a maximum relative density of 96.5% and a maximum bulk density of 3.74 g / cm³. 3 At this point, the ceramic structure is dense, and the device can be made lightweight.

[0056] Figure 4 shows the X-ray diffraction patterns of the high-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention and the Rietveld structure refinement pattern of the ceramics sintered at 1050℃. As can be seen from Figure 4(a), the synthesized high-entropy ceramics are all single garnet structures. Figure 4(b) further verifies that no second phase is generated in the high-entropy microwave dielectric ceramic body.

[0057] Figure 5 shows the Raman spectra of the high-entropy microwave dielectric ceramics with garnet structures prepared in Examples 1-5 of this invention. As can be seen from Figure 5, the change in temperature did not have a significant effect on the rotation and vibration of chemical bonds in the high-entropy microwave dielectric ceramics.

[0058] Figure 6 shows the microwave dielectric properties of the high-entropy ceramics with garnet structures prepared in Examples 1-5 of this invention. As can be seen from Figure 6, with the increase of temperature, the dielectric constant, quality factor, and temperature coefficient of resonant frequency all increase first and then decrease. The ceramic prepared in Example 4 with the optimal sintering temperature has a dielectric constant of 10.7, a quality factor of 62440 GHz, a temperature coefficient of resonant frequency of -7.4 ppm / ℃, and a dielectric constant <15. It also exhibits a high quality factor and high temperature stability, and its microwave dielectric properties are significantly improved compared to the matrix ceramic.

[0059] 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 low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure, characterized in that, Includes the following steps: S1, based on the target substance Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 The raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2, and V2O5 were weighed according to the molar ratio of their elemental composition and ball-milled with anhydrous ethanol to obtain a mixed slurry; S2, the mixed slurry was dried and then pre-calcined, followed by a second ball milling and drying to obtain dry Ca3(Co)2O5. 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 S3, Pre-formed powder; PVA aqueous solution is added to the dried pre-formed powder for granulation, and the powder is sieved to obtain a uniform powder, which is then pressed into a ceramic green body; S4, the ceramic green body is debinded and sintered to obtain Ca3(Co) 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 High-entropy microwave dielectric ceramics.

2. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S1, the purity of the raw materials CaCO3, CoO, CuO, MgO, ZnO, NiO, SiO2 and V2O5 are all ≥99%, and they need to be dried in an oven at 100℃ for 12 hours before being weighed.

3. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S2, the drying temperature is 80℃ and the drying time is 12h.

4. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S2, the pre-firing temperature is 950℃, the holding time is 8h, the heating rate is 5℃ / min, and the furnace is cooled to room temperature after the pre-firing.

5. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In steps S1 and S2, 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 8 hours and the ball mill speed is 300 r / min.

6. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S3, a 100-mesh sieve is used for sieving.

7. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S3, the concentration of the PVA aqueous solution is 5%, and the amount of PVA aqueous solution added is 7% of the mass of the pre-made powder.

8. The method for preparing a low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure as described in claim 1, characterized in that, In step S3, the tablet is pressed using dry pressing technology, under a pressure of 200MPa for 2-3 minutes, with a blank diameter of 10mm and a height of 5-6mm.

9. The method for preparing a low-dielectric-high-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 2℃ / min, and the holding time is 2h. After debinding, the sintering process continues at a temperature of 990~1070℃, a heating rate of 5℃ / min, and a holding time of 8h. After sintering, the furnace is cooled to room temperature.

10. A low-dielectric-high-entropy microwave dielectric ceramic with a garnet structure, prepared by the method according to any one of claims 1 to 9, characterized in that, The chemical formula of the high-entropy microwave dielectric ceramic is Ca3(Co). 0.2 Cu 0.2 Mg 0.2 Zn 0.2 Ni 0.2 )2SiV2O 12 The high-entropy microwave dielectric ceramic has a dielectric constant of 6.5 to 10.4, a quality factor of 12490 to 62440 GHz, and a resonant frequency temperature coefficient of -9.2 to -7.4 ppm / ℃. It is composed of five metal elements in equal molar ratios of Co, Cu, Mg, Zn and Ni occupying the B site, forming a high configurational entropy.

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