Low-dielectric ultra-low-loss temperature-stable ltcc material and preparation method thereof

Abstract

The application discloses a kind of low dielectric ultra-low loss temperature stable LTCC materials and preparation method thereof, LTCC material chemical general formula is Li 3+x Mg 2‑x NbO 6‑x F x ,0.02≤x≤0.1, crystal phase is pure phase Li3Mg2NbO6.This ceramic material is by Li 3+x Mg 2‑x NbO 6‑x F x Chemical stoichiometry ratio is dosed, 0.02≤x≤0.1, after first ball milling mixing, pre-sintering 3~5 hours at 700~800 DEG C temperature, after second ball milling mixing, granulation, shaping is carried out, and sintering 3~5 hours at 820~900 DEG C temperature is made.The application simultaneously adopts anion / cation to Li3Mg2NbO6 crystal structure and carries out fine tuning, reduces sintering temperature, improves lattice energy and order degree, to improve the quality factor and temperature stability of ceramic material.

Description

Technical Field

[0001] This invention relates to the field of microwave dielectric ceramic materials technology, specifically to a low dielectric ultra-low loss temperature stable LTCC material and its preparation method. Background Technology

[0002] Microwave dielectric ceramics, primarily used in the microwave frequency band (300MHz~300GHz), are novel functional ceramics that play a role in circuits and are widely used in microwave components such as dielectric resonators, filters, and dielectric antennas. To meet the requirements of miniaturization, lightweighting, multifunctionality, and cost reduction in equipment, microwave dielectric ceramics have become one of the hot topics in microwave dielectric materials research both domestically and internationally. To meet the requirements of devices, microwave dielectric ceramic materials should satisfy the following conditions: ① Moderate dielectric constant: a high dielectric constant can reduce device size, while a low dielectric constant can reduce signal delay; ② High quality factor to suppress signal attenuation, improve the signal-to-noise ratio, ensure excellent frequency selectivity, and reduce insertion loss at high frequencies; ③ Good temperature coefficient of resonant frequency, which ensures the temperature reliability of the device. Therefore, microwave dielectric materials that simultaneously meet the requirements of dielectric constant and low loss have attracted the interest of many researchers. However, existing material systems often cannot simultaneously meet these performance requirements. Therefore, the development of new ceramic material systems is necessary.

[0003] In recent years, Li3Mg2NbO6-based ceramics have been widely studied as a novel type of low-loss microwave dielectric ceramic with excellent microwave dielectric properties. Its microwave dielectric properties are: ε... r =16.8, Q×f=79643GHz, τ f= -27.2ppm / ℃. However, its sintering temperature is too high (≥1250℃) and there is still room for further optimization of the Q×f value. Low melting point additives can appropriately reduce the sintering temperature of Li3Mg2NbO6 ceramics, but they also introduce a second phase, which reduces the quality factor of the ceramics and results in a large temperature coefficient of resonant frequency (Low temperature sintering and microwave dielectric properties of Li3Mg2NbO6 ceramics doped with Li2O-B2O3-SiO2 glass, Journal of Alloys and Compounds, 2017, 690:688-691). The paper "Effect of MBS addition on the low temperature sintering and microwave dielectric properties of Li3Mg2NbO6 ceramics," published in *Journal of Materials Science: Materials in Electronics*, 2016, 27: 6395-6398, discloses the dielectric properties of ceramic materials with the addition of MBS and B2O3: a dielectric constant of 14.5, a Q×f value of 80759 GHz, and a frequency temperature coefficient of -21.96 ppm / ℃; and a dielectric constant of 14.0, a Q×f value of 67451 GHz, and a frequency temperature coefficient of -16.82 ppm / ℃. The ceramics with the addition of MBS and B2O3 exhibit relatively high losses and temperature coefficients, making them difficult to meet practical application requirements. Therefore, how to maintain a pure phase, lower the sintering temperature of Li3Mg2NbO6, while simultaneously reducing dielectric losses and improving temperature stability remains a key area of ​​research. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to achieve low-temperature sintering of Li3Mg2NbO6 ceramics and improve their dielectric properties while maintaining phase purity.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] A low-dielectric, ultra-low-loss, temperature-stable LTCC material with the general chemical formula Li 3+x Mg 2-x NbO 6-x F x Where 0.02≤x≤0.1, its crystal phase is pure phase Li3Mg2NbO6.

[0007] Preferably, the low dielectric, ultra-low loss, temperature-stable LTCC material is composed of Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x The ingredients are mixed according to a stoichiometric ratio, where 0.02 ≤ x ≤ 0.1. After the first ball milling, the mixture is pre-calcined at 700℃~800℃ for 3~5 hours, then mixed again by ball milling, granulated, shaped, and sintered at 820℃~900℃ for 3~5 hours to produce the final product.

[0008] Preferably, the low-dielectric-value, ultra-low-loss, temperature-stable LTCC material has the following dielectric properties: relative permittivity ε r The frequency response is 15.4–15.9, the quality factor Q×f is 122,000–154,000 GHz, and the temperature coefficient of resonant frequency τ is [not specified]. f The value is -10 to 5 ppm / ℃.

[0009] This invention also proposes a method for preparing the aforementioned low-dielectric, ultra-low-loss, temperature-stable LTCC material, comprising the following steps: mixing Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x The ingredients are prepared according to a stoichiometric ratio, where 0.02 ≤ x ≤ 0.1. After the first ball milling, the mixture is pre-calcined at 700℃~800℃ for 3~5 hours, then granulated and shaped after a second ball milling to obtain a green body. Finally, the green body is sintered at 820℃~900℃ for 3~5 hours to obtain the low dielectric ultra-low loss temperature stable LTCC material.

[0010] Preferably, the preparation method of the low dielectric ultra-low loss temperature-stable LTCC material includes the following steps:

[0011] S1. Ingredients: Mix the raw materials Li2CO3, MgO, LiF, and Nb2O5 according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x The ingredients are prepared according to the stoichiometric ratio, where 0.02 ≤ x ≤ 0.1;

[0012] S2. Mixing: The raw material obtained in S1 is subjected to ball milling for the first time. During the ball milling process, the raw material, solvent and ball milling media are placed in a ball mill for wet ball milling to obtain the first slurry.

[0013] S3. Drying the slurry: The first slurry obtained in S2 is dried to obtain a dried mixture, and then the dried mixture is sieved to obtain a dried powder;

[0014] S4. Pre-calcination: The dried powder obtained in S3 is calcined at 700℃~800℃ for 3~5 hours to obtain pre-calcined powder.

[0015] S5. Ball milling: The pre-calcined powder obtained in S4 is subjected to a second ball milling. During the ball milling process, the pre-calcined powder, solvent and ball milling media are placed in a ball mill for wet ball milling to obtain a second slurry.

[0016] S6. Granulation and pressing of green body: The second slurry obtained in S5 is dried and crushed, then a granulating agent is added to it for granulation, and then the granulated powder is pressed to form a green body.

[0017] S7. Sintering: The green blank obtained in S6 is sintered at 820℃~900℃ for 3~5 hours to prepare the pure phase low dielectric ultra-low loss temperature stable LTCC material.

[0018] Preferably, in the first and second ball milling processes, deionized water is used as the solvent, zirconium dioxide balls are used as the milling medium, the mass ratio of raw material, zirconium dioxide balls and deionized water is 1:2 to 5:2 to 5, the rotation speed is 200 to 400 rad / min, and the milling time is 2 to 6 hours.

[0019] Preferably, in step S3, the drying temperature is 90–120°C.

[0020] Preferably, a polyvinyl alcohol aqueous solution with a mass concentration of 12-15% is used as the granulating agent during the granulation process.

[0021] Preferably, the obtained green compact is first heated from room temperature to 400-600°C at a heating rate of 2-5°C / min, and held at this temperature for 2-5 hours. Then, it is heated to a sintering temperature of 820-900°C at a heating rate of 2-5°C / min and sintered for 3-5 hours to obtain the low dielectric ultra-low loss temperature-stable LTCC material.

[0022] The advantages of this invention are:

[0023] This invention uses Li in LiF + Replacement of Mg 2+ Li′ constitutes a negatively charged defect Mg F - Replace O 2- Constitutes positively charged defects The conservation of charge at the center of positive and negative charges leads to Coulomb attraction, thereby enhancing the lattice energy and improving the quality factor and temperature stability of the ceramic material. Simultaneously, the low melting point of LiF lowers the sintering temperature of Li3Mg2NbO6, enabling low-temperature co-firing. The samples of this invention, while maintaining a pure-phase structure, can be sintered at low temperatures and still possess extremely excellent dielectric properties, specifically ε... r =15.4~15.9, Q×f=122,000~154,000GHz, τ f = -10 to 5 ppm / ℃. Attached Figure Description

[0024] Figure 1 The X-ray diffraction (XRD) patterns of the products of Comparative Example 1 and Examples 1-5 of this invention are shown.

[0025] Figure 2 The images are SEM images of the products of Comparative Example 1 and Examples 1-3 of this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0028] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0029] Example 1

[0030] This embodiment provides a low dielectric, ultra-low loss, temperature-stable LTCC material with the chemical formula Li. 3.02 Mg 1.98 NbO 5.98 F 0.02 Its preparation method includes the following steps:

[0031] Step 1: Ingredients: Mix the raw materials Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3.02 Mg 1.98 NbO 5.98 F 0.02 The ingredients are prepared according to the stoichiometric ratio;

[0032] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:5:3 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 300 rad / min to obtain the first slurry.

[0033] Step 3: Drying the slurry: Pour out the first slurry obtained in Step 2 and dry it in an oven at 120°C to obtain a dry mixture. Then, pass the dried mixture through a 100-mesh standard sieve to obtain a dry powder.

[0034] Step 4: Pre-calcination: Place the dried powder obtained in step 3 into an alumina crucible and pre-calcine it at 700℃ for 5 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0035] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:5:3 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 300 rad / min to obtain the second slurry.

[0036] Step 6: Granulation and pressing of green body; Pour out the second slurry obtained in step 5, dry it in an oven at 100℃, and after pulverization, add a 15% polyvinyl alcohol (PVA) aqueous solution. After passing it through an 80-mesh sieve, granulate it, and then press it at 12 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0037] Step 7: Sintering: The green body obtained in Step 6 is sintered at 900℃ for 4 hours. The specific heating operation is as follows: First, the temperature is raised to 600℃ at a heating rate of 3℃ / min and maintained at this temperature for 2 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 900℃ at a heating rate of 3℃ / min and sintered for 4 hours to obtain a ceramic material with a pure phase of Li3Mg2NbO6, which is the low dielectric ultra-low loss temperature stable LTCC material.

[0038] Example 2

[0039] This embodiment provides a low dielectric, ultra-low loss, temperature-stable LTCC material with the chemical formula Li. 3.04 Mg 1.96 NbO 5.96 F 0.04 Its preparation method includes the following steps:

[0040] Step 1: Ingredients: Mix the raw materials Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3.04 Mg 1.96 NbO 5.96 F 0.04 The ingredients are prepared according to the stoichiometric ratio;

[0041] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:3:5 for wet ball milling. The ball milling time is 5 hours and the rotation speed is 300 rad / min to obtain the first slurry.

[0042] Step 3: Drying the slurry: Pour out the first slurry obtained in Step 2 and dry it in an oven at 120°C to obtain a dry mixture. Then, pass the dried mixture through a 100-mesh standard sieve to obtain a dry powder.

[0043] Step 4: Pre-calcination: Place the dried powder obtained in step 3 into an alumina crucible and pre-calcine it at 750°C for 4 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0044] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:3:5 for wet ball milling. The ball milling time is 5 hours and the rotation speed is 350 rad / min to obtain the second slurry.

[0045] Step 6: Granulation and pressing of green body: Pour out the second slurry obtained in step 5, dry it in an oven at 120℃, and after pulverization, add a 12% polyvinyl alcohol (PVA) aqueous solution. After passing it through a 100-mesh sieve, granulate it, and then press it at 12 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0046] Step 7: Sintering: The green body obtained in Step 6 is sintered at 880℃ for 4 hours. The specific heating operation is as follows: First, the temperature is raised to 550℃ at a heating rate of 2℃ / min and maintained at this temperature for 2 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 880℃ at a heating rate of 3℃ / min and sintered for 4 hours to obtain a ceramic material with a pure phase of Li3Mg2NbO6, which is the low dielectric ultra-low loss temperature stable LTCC material.

[0047] Example 3

[0048] This embodiment provides a low dielectric, ultra-low loss, temperature-stable LTCC material with the chemical formula Li. 3.06 Mg 1.94 NbO 5.94 F 0.06 Its preparation method includes the following steps:

[0049] Step 1: Ingredients: Mix the raw materials Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3.06 Mg 1.94 NbO 5.94 F 0.06 The ingredients are prepared according to the stoichiometric ratio;

[0050] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:2:4 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 200 rad / min to obtain the first slurry.

[0051] Step 3: Drying the slurry: Pour out the first slurry obtained in Step 2 and dry it in an oven at 120°C to obtain a dry mixture. Then, pass the dried mixture through a 100-mesh standard sieve to obtain a dry powder.

[0052] Step 4: Pre-calcination: Place the dried powder obtained in step 3 into an alumina crucible and pre-calcine it at 800℃ for 3 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0053] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:2:4 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 200 rad / min to obtain the second slurry.

[0054] Step 6: Granulation and pressing of green body: Pour out the second slurry obtained in step 5, dry it in an oven at 120℃, and after pulverization, add a 12% polyvinyl alcohol (PVA) aqueous solution. After passing it through a 100-mesh sieve, granulate it, and then press it at 12 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0055] Step 7: Sintering: The green body obtained in Step 6 is sintered at 860℃ for 5 hours. The specific heating operation is as follows: First, the temperature is raised to 500℃ at a heating rate of 5℃ / min and maintained at this temperature for 5 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 860℃ at a heating rate of 5℃ / min and sintered for 5 hours to obtain a ceramic material with a pure phase of Li3Mg2NbO6, which is the low dielectric ultra-low loss temperature stable LTCC material.

[0056] Example 4

[0057] This embodiment provides a low dielectric, ultra-low loss, temperature-stable LTCC material with the chemical formula Li. 3.08 Mg 1.92 NbO 5.92 F 0.08 Its preparation method includes the following steps:

[0058] Step 1: Ingredients: Mix the raw materials Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3.08 Mg 1.92 NbO 5.92 F 0.08 The ingredients are prepared according to the stoichiometric ratio;

[0059] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:2:5 for wet ball milling. The ball milling time is 5 hours and the rotation speed is 250 rad / min to obtain the first slurry.

[0060] Step 3: Drying the slurry: Pour out the first slurry obtained in step 2 and dry it in an oven at 120°C to obtain a dry mixture. Then, pass the dried mixture through a 120-mesh standard sieve to obtain a dry powder.

[0061] Step 4: Pre-calcination: Place the dried powder obtained in step 3 in an alumina crucible and pre-calcine it at 750°C for 3 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0062] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:2:5 for wet ball milling. The ball milling time is 5 hours and the rotation speed is 250 rad / min to obtain the second slurry.

[0063] Step 6: Granulation and pressing of green body: Pour out the second slurry obtained in step 5, dry it in an oven at 100℃, and after pulverization, add a 14% polyvinyl alcohol (PVA) aqueous solution. After passing through a 120-mesh sieve, granulate it and then press it at 12 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0064] Step 7: Sintering: The green body obtained in Step 6 is sintered at 840℃ for 3 hours. The specific heating operation is as follows: First, the temperature is raised to 450℃ at a heating rate of 3℃ / min and maintained at this temperature for 3 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 840℃ at a heating rate of 3℃ / min and sintered for 3 hours to obtain a ceramic material with pure phase Li3Mg2NbO6, which is the low dielectric ultra-low loss temperature stable LTCC material.

[0065] Example 5

[0066] This embodiment provides a low dielectric, ultra-low loss, temperature-stable LTCC material with the chemical formula Li. 3.1 Mg 1.9 NbO 5.9 F 0.1 Its preparation method includes the following steps:

[0067] Step 1: Ingredients: Mix the raw materials Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3.1 Mg 1.9 NbO 5.9 F 0.1 The ingredients are prepared according to the stoichiometric ratio;

[0068] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:4:4 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 350 rad / min to obtain the first slurry.

[0069] Step 3: Drying the slurry: Pour out the first slurry obtained in Step 2 and dry it in an oven at 80°C to obtain a dry mixture. Then, pass the dried mixture through a 120-mesh standard sieve to obtain a dry powder.

[0070] Step 4: Pre-calcination: Place the dried powder obtained in step 3 into an alumina crucible and pre-calcine it at 700℃ for 4 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0071] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:4:4 for wet ball milling. The ball milling time is 6 hours and the rotation speed is 350 rad / min to obtain the second slurry.

[0072] Step 6: Granulation and pressing of green body: Pour out the second slurry obtained in step 5, dry it in an oven at 100℃, and after pulverization, add a 15% polyvinyl alcohol (PVA) aqueous solution. After passing through a 120-mesh sieve, granulate it and then press it at 15 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0073] Step 7: Sintering: The green body obtained in Step 6 is sintered at 820℃ for 4 hours. The specific heating operation is as follows: First, the temperature is raised to 500℃ at a heating rate of 4℃ / min and maintained at this temperature for 2 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 820℃ at a heating rate of 4℃ / min and sintered for 4 hours to obtain a ceramic material with a pure phase of Li3Mg2NbO6, which is the low dielectric ultra-low loss temperature stable LTCC material.

[0074] Comparative Example 1

[0075] This comparative example provides a microwave dielectric ceramic material with the general chemical formula Li3Mg2NbO6, and its preparation method includes the following steps:

[0076] Step 1: Ingredients: Ingredients Li2CO3, MgO, and Nb2O5 are mixed according to the stoichiometric ratio of the general chemical formula Li3Mg2NbO6;

[0077] Step 2: Mixing: The raw materials obtained in Step 1 are ball-milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The raw materials, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:4:3 for wet ball milling. The ball milling time is 4 hours and the rotation speed is 250 rad / min to obtain the first slurry.

[0078] Step 3: Drying the slurry: Pour out the first slurry obtained in step 2 and dry it in an oven at 100°C to obtain a dry mixture. Then, pass the dried mixture through a 120-mesh standard sieve to obtain a dry powder.

[0079] Step 4: Pre-calcination: Place the dried powder obtained in step 3 into an alumina crucible and pre-calcine it at 1000℃ for 4 hours to allow the dried powder to undergo a pre-reaction and obtain pre-calcined powder.

[0080] Step 5: Ball milling: The pre-calcined powder obtained in step 4 is ball milled. Specifically, zirconia balls are used as the ball milling medium and deionized water is used as the solvent. The pre-calcined powder, zirconia balls, and deionized water are placed in a planetary ball mill at a mass ratio of 1:4:3 for wet ball milling. The ball milling time is 4 hours and the rotation speed is 250 rad / min to obtain the second slurry.

[0081] Step 6: Granulation and pressing of green body: Pour out the second slurry obtained in step 5, dry it in an oven at 100℃, and after pulverization, add a 12% polyvinyl alcohol (PVA) aqueous solution. After passing through an 80-mesh sieve, granulate it and then press it at 10 MPa to form a cylindrical green body with a diameter of 12 mm and a thickness of 6 mm.

[0082] Step 7: Sintering: The green body obtained in Step 6 is sintered at 1200℃ for 4 hours. The specific heating operation is as follows: First, the temperature is raised to 500℃ at a heating rate of 2℃ / min and maintained at this temperature for 2 hours. The purpose is to remove excess PVA. Then, the temperature is raised to the sintering temperature of 1200℃ at a heating rate of 2℃ / min and sintered for 4 hours to obtain a ceramic material with pure phase Li3Mg2NbO6.

[0083] Figure 1 The images show the X-ray diffraction (XRD) patterns of the products from Comparative Example 1 and Examples 1-5 of this invention. The XRD patterns of the comparative sample are shown below. Figure 1 As shown in (x=0), the XRD values ​​of Examples 1-5 are as follows: x=0.02, x=0.04, x=0.06, x=0.08, x=0.1. Figure 1 It can be seen from this that different Li + / F - The ceramic materials obtained by the substitution amount were all pure phase Li3Mg2NbO6, which indicates that Li + / F - The entry of ions into the Li3Mg2NbO6 crystal lattice did not form a second phase, nor did it alter the crystal structure of the Li3Mg2NbO6 ceramic. + / F - Ions fine-tuned the crystal structure of Li3Mg2NbO6, Li + Replacement of Mg 2+ Li′ constitutes a negatively charged defect Mg F - Replace O 2- Constitutes positively charged defects The conservation of charge at the positive and negative charge centers, along with the existence of Coulomb attraction, enhances the lattice energy, thereby improving the quality factor and temperature stability of the ceramic material. Simultaneously, the low melting point of LiF lowers the sintering temperature of Li3Mg2NbO6, enabling low-temperature co-firing.

[0084] Figure 2 These are SEM images of Comparative Example 1 (Fig. a), Example 1 (Fig. b), Example 2 (Fig. c), and Example 3 (Fig. d) of the present invention. It can be seen from them that without Li... + / F - The sample with the appropriate amount of substitution exhibited small grains and pores. As the substitution amount increased, due to the absence of lithium volatilization during low-temperature sintering, the pores gradually disappeared, and the grains began to grow.

[0085] Table 1. Sintering temperature and microwave dielectric properties of specific embodiments and comparative samples.

[0086] serial number Chemical formula Sintering temperature <![CDATA[ε r ]]> Q×f <![CDATA[τ f ]]> Comparative Example 1 <![CDATA[Li3Mg2NbO6]]> 1200℃ 16.2 82,000GHz -15ppm / ℃ Example 1 <![CDATA[Li 3.02 Mg 1.98 NbO 5.98 F 0.02 ]]> 900℃ 15.9 122000GHz -10ppm / ℃ Example 2 <![CDATA[Li 3.04 Mg 1.96 NbO 5.96 F 0.04 ]]> 880℃ 15.72 134100GHz -7.4ppm / ℃ Example 3 <![CDATA[Li 3.06 Mg 1.94 NbO 5.94 F 0.06 ]]> 860℃ 15.62 142000GHz -3.2ppm / ℃ Example 4 <![CDATA[Li 3.08 Mg 1.92 NbO 5.92 F 0.08 ]]> 840℃ 15.54 153800GHz 1.2ppm / ℃ Example 5 <![CDATA[Li 3.1 Mg 1.9 NbO 5.9 F 0.1 ]]> 820℃ 15.41 143000GHz 5ppm / ℃

[0087] Table 1 shows the sintering temperature and microwave dielectric properties of specific embodiments and comparative samples of the present invention. The microwave dielectric properties were tested using the resonant cavity method. Due to Li... + / F - The average polarizability of Li ions is low, thus their dielectric constant shows a gradually decreasing trend. Meanwhile, Li... + / F - Ion substitution also promotes grain growth, increasing grain size and reducing porosity. The presence of grain boundaries often acts as a two-dimensional defect and disrupts long-range order in the crystal, leading to dielectric loss. Using Li in LiF... + Replacement of Mg 2+ Li′ constitutes a negatively charged defect Mg F - Replace O 2- Constitutes positively charged defects The conservation of charge at the positive and negative charge centers, along with the existence of Coulomb attraction, enhances the lattice energy, thereby improving the quality factor and temperature stability of the ceramic material. Simultaneously, the low melting point of LiF lowers the sintering temperature of Li3Mg2NbO6, enabling low-temperature co-firing.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-dielectric-value, ultra-low-loss, temperature-stable LTCC material, characterized in that: Its general chemical formula is Li 3+x Mg 2- x NbO 6-x F x Where, 0.02≤ x ≤0.1, its crystalline phase is pure phase Li3Mg2NbO6; it is composed of Li2CO3, MgO, LiF, and Nb2O5 according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x Ingredients are prepared according to stoichiometric ratios, where 0.02 ≤ x ≤0.1, after the first ball milling and mixing, pre-calcination at 700°C~800°C for 3~5 hours, followed by a second ball milling and mixing, granulation and molding, and sintering at 820°C~900°C for 3~5 hours to produce.

2. The low dielectric ultra-low loss temperature-stable LTCC material according to claim 1, characterized in that: Its dielectric properties are as follows: relative permittivity ε r The quality factor is 15.4 to 15.

9. Q×f The resonant frequency temperature coefficient is 122,000~154,000 GHz. τ f for 10–5 ppm / °C.

3. A method for preparing a low-dielectric, ultra-low-loss, temperature-stable LTCC material as described in any one of claims 1-2, characterized in that, The steps include: mixing Li₂CO₃, MgO, LiF, and Nb₂O₅ according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x Ingredients are prepared according to stoichiometric ratios, where 0.02 ≤ x The material is ≤0.

1. After the first ball milling and mixing, it is pre-fired at 700°C~800°C for 3~5 hours, then granulated and shaped after the second ball milling and mixing to obtain a green body. The green body is then sintered at 820°C~900°C for 3~5 hours to obtain the low dielectric ultra-low loss temperature stable LTCC material.

4. The method for preparing the low-dielectric-value, ultra-low-loss, temperature-stable LTCC material according to claim 3, characterized in that: Includes the following steps: S1. Ingredients: Mix the raw materials Li2CO3, MgO, LiF, and Nb2O5 according to the general chemical formula Li 3+x Mg 2-x NbO 6-x F x The ingredients are prepared according to the stoichiometric ratio, where 0.02 ≤ x ≤0.1; S2. Mixing: The raw material obtained in S1 is subjected to ball milling for the first time. During the ball milling process, the raw material, solvent and ball milling media are placed in a ball mill for wet ball milling to obtain the first slurry. S3. Drying the slurry: The first slurry obtained in S2 is dried to obtain a dried mixture, and then the dried mixture is sieved to obtain a dried powder; S4. Pre-calcination: The dried powder obtained in S3 is calcined at 700°C to 800°C for 3 to 5 hours to obtain pre-calcined powder. S5. Ball milling: The pre-calcined powder obtained in S4 is subjected to a second ball milling. During the ball milling process, the pre-calcined powder, solvent and ball milling media are placed in a ball mill for wet ball milling to obtain a second slurry. S6. Granulation and pressing of green body: The second slurry obtained in S5 is dried and crushed, then a granulating agent is added to it for granulation, and then the granulated powder is pressed to form a green body. S7. Sintering: The green blank obtained in S6 is sintered at 820°C to 900°C for 3 to 5 hours to prepare the pure phase low dielectric ultra-low loss temperature stable LTCC material.

5. The method for preparing the low dielectric ultra-low loss temperature-stable LTCC material according to claim 3 or 4, characterized in that: In the first and second ball milling processes, deionized water was used as the solvent, and zirconia balls were used as the milling medium. The mass ratio of raw material, zirconia balls, and deionized water was 1:2 to 5:2 to 5, the rotation speed was 200 to 400 rad / min, and the milling time was 2 to 6 hours.

6. The method for preparing low-dielectric-value, ultra-low-loss, temperature-stable LTCC material according to claim 4, characterized in that: In S3, the drying temperature is 90–120°C.

7. The method for preparing the low dielectric ultra-low loss temperature-stable LTCC material according to claim 3 or 4, characterized in that: In the granulation process, a polyvinyl alcohol aqueous solution with a mass concentration of 12-15% is used as the granulating agent.

8. The method for preparing the low dielectric ultra-low loss temperature-stable LTCC material according to claim 3 or 4, characterized in that: The obtained green compact is first heated from room temperature to 400-600°C at a heating rate of 2-5°C / min, and held at this temperature for 2-5 hours. Then, it is heated to the sintering temperature of 820-900°C at a heating rate of 2-5°C / min and sintered for 3-5 hours to obtain the low dielectric ultra-low loss temperature stable LTCC material.

Images