Low-cost low-dielectric high-performance microwave dielectric ceramic material and preparation method thereof

Abstract

The invention relates to the technical field of electronic ceramics, in particular to a low-cost, low-dielectric and high-performance microwave dielectric ceramic material and a preparation method thereof.Mg2SiO4 prepared from talcum powder and MgO serves as a matrix, and CaTiO3 or SrTiO3 is added to adjust the temperature stability; caTiO3 is selected to adjust the temperature coefficient, and LiF is added to reduce the sintering temperature. The Mg2SiO4 + x wt% CaTiO3 / y wt% SrTiO3 + z wt% LiF microwave dielectric ceramic prepared by a solid-phase sintering method has the advantages of low dielectric constant, low loss, low sintering temperature and ultrahigh Q * f value, a silicon raw material and a magnesium raw material are replaced by talc, the sintering temperature is reduced to 875 DEG C while the production cost is reduced, and a feasible path is provided for industrial production of low-temperature co-fired high-performance microwave dielectric ceramics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic ceramics, and particularly relates to a low-cost low-dielectric high-performance microwave dielectric ceramic material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of wireless communication technology, especially the vigorous rise of 5G / 6G, satellite communication and Internet of Things, microwave dielectric ceramics, as the core basic material of microwave circuits, are required to have unprecedented high performance. An ideal microwave dielectric ceramic needs to have a suitable dielectric constant (ε r ) to reduce the size of the device, a very high quality factor (Qxf value) to reduce signal transmission loss, and a near-zero resonance frequency temperature coefficient (τ f ) to ensure stable operation of the device in a wide temperature range. Among many candidate materials, magnesium orthosilicate (Mg2SiO4) stands out due to its unique crystal structure and excellent intrinsic properties, and becomes an extremely attractive choice in high-frequency and low-loss application fields. The most significant advantage of Mg2SiO4 ceramic is its extremely low dielectric loss (corresponding to a very high Qxf value), which is derived from weak ion polarization and low lattice vibration loss caused by the olivine structure composed of magnesium-oxygen octahedra [MgO6] and isolated silicon-oxygen tetrahedra [SiO4]. At the same time, its low dielectric constant (ε r ≈6-7) is very suitable for designing small-sized high-frequency devices (such as millimeter wave antennas and filters). However, the preparation of pure-phase Mg2SiO4 ceramic faces two major challenges: first, the extremely high sintering temperature (usually >1450℃) leads to high energy consumption and easy reaction with common electrode materials, which restricts actual application; second, its negative resonance frequency temperature coefficient (τ f ≈-60ppm / ℃) is difficult to meet the temperature stability requirements of actual devices.

[0003] Therefore, talc powder (Mg3Si4O 10 (OH)2) as a natural mineral raw material contains both silicon raw materials and magnesium raw materials, and has significant advantages in replacing traditional preparation methods for Mg2SiO4 microwave dielectric ceramic. Compared with traditional high-purity oxides (MgO+SiO2) or chemical synthesis methods, talc powder has the characteristics of low cost, low-temperature sintering activity, environmental friendliness, etc. Its Mg / Si stoichiometric ratio is close to the theoretical value, which can reduce the error of batching, and generate high-activity MgO and SiO2 during calcination, which can promote the formation of Mg2SiO4 phase, and reduce the sintering temperature (1250-1350℃) compared with traditional methods (1350-1450℃). In addition, talc powder has the advantages of lower price, simplified process, energy saving and environmental protection, etc., and provides a feasible path for the industrial production of high-performance microwave dielectric ceramics. In the future, combined with doping modification, the temperature stability can be further optimized to promote the development of high-frequency electronic devices. SUMMARY

[0004] The present application aims at providing a low-cost low-dielectric high-performance microwave dielectric ceramic material and a preparation method thereof, and solving the problems of high cost, high sintering temperature, high energy consumption, and reaction with common electrode materials to restrict practical application and difficult to meet the temperature stability requirement of actual devices due to the negative resonant frequency temperature coefficient of the Mg2SiO4 ceramic prepared by the traditional method.

[0005] To achieve the above-mentioned purpose, the present application provides a low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method, comprising the following steps:

[0006] The talc powder and MgO are mixed and then added into anhydrous ethanol, and placed in a ball mill for first wet grinding to obtain a slurry;

[0007] The slurry is placed in a drying box for drying;

[0008] The dried slurry powder is sieved, and then placed in a muffle furnace for pre-sintering;

[0009] After the pre-sintered powder is cooled, CaTiO3 or SrTiO3, LiF and anhydrous ethanol are added for second wet grinding;

[0010] The slurry after the second wet grinding is granulated after drying and sieving, and then pressed into a green ceramic body;

[0011] The green ceramic body is sintered to obtain a microwave dielectric ceramic material.

[0012] The talc powder and MgO are mixed and then added into anhydrous ethanol, and placed in a ball mill for first wet grinding to obtain a slurry, wherein:

[0013] The talc powder is dosed according to the stoichiometric formula Mg2SiO4, the mass ratio of anhydrous ethanol to Mg2SiO4 is 2:1, and the first wet grinding time is 4 hours.

[0014] The slurry is placed in a drying box for drying, wherein:

[0015] The drying temperature ranges from 85 to 100 DEG C.

[0016] The dried slurry powder is sieved, and then placed in a muffle furnace for pre-sintering, wherein:

[0017] An 80-mesh sieve is used for sieving, and the pre-sintering temperature of the muffle furnace is 1200 DEG C, and the pre-sintering time is 2 hours.

[0018] After the pre-sintered powder is cooled, CaTiO3 or SrTiO3, LiF and anhydrous ethanol are added for second wet grinding, wherein:

[0019] After the pre-sintered powder is cooled to room temperature, Mg2SiO4, CaTiO3, SrTiO3, LiF are proportioned according to Mg2SiO4+x wt% CaTiO3 / y wt% SrTiO3+z wt% LiF, wherein x=5-20, y=6-12, z=2.5-10;

[0020] Anhydrous ethanol is added for the second wet grinding, and the second wet grinding lasts for 4 hours.

[0021] The slurry after the second wet grinding is dried and sieved, granulated, and pressed into a ceramic green body, wherein:

[0022] The drying temperature ranges from 85-100℃.

[0023] The slurry after the second wet grinding is dried and sieved, granulated, and pressed into a ceramic green body, wherein:

[0024] In the process of drying and granulating, 30% polymethyl methacrylate solution is used as a binder.

[0025] The ceramic green body is sintered to obtain a microwave dielectric ceramic material, wherein:

[0026] The sintering temperature of the ceramic green body is 800-950℃, 1320-1440℃, or 1520-1600℃, and the duration is 2 hours.

[0027] A low-cost low-dielectric high-performance microwave dielectric ceramic material, comprising a Mg2SiO4 matrix and x wt% CaTiO3 or y wt% SrTiO3 and z wt% LiF, wherein x is 5-20, y is 6-12, z is 2.5-10, and the Mg2SiO4 matrix is prepared from 4000-mesh talc powder and MgO.

[0028] The microwave dielectric ceramic material has a dielectric constant ε r of 6.21-11.10, a quality factor Qxf of 14420-112056 GHz, and a resonance frequency temperature coefficient τ f of -58.25-41.17 ppm / ℃.

[0029] The application discloses a low-cost low-dielectric high-performance microwave dielectric ceramic material and a preparation method thereof, and the low-cost low-dielectric high-performance microwave dielectric ceramic material is prepared from talc powder and MgO, Mg2SiO4 is used as a matrix, CaTiO3 or SrTiO3 is added to adjust temperature stability, CaTiO3 is selected to adjust a temperature coefficient, and LiF is added to reduce a sintering temperature. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced.

[0031] Figure 1 is a process flow chart of the low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method of the application.

[0032] Figure 2 is a step flow chart of the low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method of the application. DETAILED DESCRIPTION

[0033] The embodiments of the application will be described in detail below, examples of which are shown in the drawings, and the embodiments described below by referring to the drawings are exemplary and are intended to explain the application, and cannot be understood as a limitation of the application.

[0034] Please refer to Figure 1 and Figure 2 , wherein, Figure 1 is a process flow chart of the low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method of the application. Figure 2 is a step flow chart of the low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method of the application.

[0035] The application provides a low-cost low-dielectric high-performance microwave dielectric ceramic material preparation method, which comprises the following steps.

[0036] S1: talc powder and MgO are mixed, then anhydrous ethanol is added, and the mixture is placed in a ball mill for first wet grinding to obtain a slurry;

[0037] S2: the slurry is placed in a drying box for drying;

[0038] S3: the dried slurry powder is sieved, and then the powder is placed in a muffle furnace for pre-sintering.

[0039] S4: after cooling the pre-fired powder, CaTiO3 or SrTiO3, LiF and anhydrous ethanol are added for second wet grinding;

[0040] S5: after the second wet grinding, the slurry is dried and sieved, then granulated and pressed into a ceramic green body;

[0041] S6: the ceramic green body is sintered to obtain a microwave dielectric ceramic material.

[0042] Specifically, in step S1, the ingredients are prepared according to the stoichiometric formula Mg2SiO4, the mass ratio of anhydrous ethanol to Mg2SiO4 is 2:1, and the first wet grinding time is 4 hours.

[0043] The temperature range for drying in step S2 and step S5 is 85-100℃.

[0044] In step S3, a 80 mesh sieve is used for sieving, and the pre-sintering temperature of the muffle furnace is 1200℃, and the pre-sintering time is 2 hours.

[0045] In step S4, after cooling the pre-fired powder to room temperature, Mg2SiO4, CaTiO3, SrTiO3, LiF are prepared according to the formula Mg2SiO4+xwt%CaTiO3 / y wt%SrTiO3+z wt%LiF, wherein x=5-20, y=6-12, z=2.5-10. Anhydrous ethanol is added for second wet grinding, and the second wet grinding time is 4 hours.

[0046] In the process of drying and granulating in step S5, 30% polymethyl methacrylate solution is used as the binder.

[0047] In step S6, the sintering temperature of the ceramic green body is 800-950℃, 1320-1440℃, 1520-1600℃, and the time is 2 hours.

[0048] In order to better understand the technical solution, the following examples are provided for further illustration: Specific example 1:

[0050] A microwave dielectric ceramic material is prepared by replacing part of the high-purity magnesium and silicon raw materials with talc powder by solid phase sintering method. The specific implementation steps are as follows:

[0051] (1) A certain amount of talc and MgO powder is weighed according to the chemical formula Mg2SiO4, anhydrous ethanol is added, and the mass ratio of anhydrous ethanol to anhydrous ethanol is 1:2 for first wet grinding, the time is 4 hours, and the rotation speed is 550 revolutions per minute;

[0052] (2) Place the powder slurry obtained in step (1) into a drying oven and dry it at 85~100℃;

[0053] (3) Place the sieved powder from step (2) into a muffle furnace and pre-fire it at 1200℃ for 2 hours;

[0054] (4) Add anhydrous ethanol to the powder after calcination in step (3). The mass ratio of the mixture to anhydrous ethanol is 1:2. Perform a second wet milling. The duration of the second wet milling is 4 hours and the rotation speed is 550 rpm.

[0055] (5) Place the powder slurry obtained in step (4) into a drying oven, dry it at 85~100℃, granulate it with 30% polymethyl methacrylate solution as a binder, pass it through an 80-mesh sieve, and then press it into ceramic green body using a tablet press.

[0056] (6) The green blank from step (5) is sintered at 1580°C for 2 hours.

[0057] (7) The microwave dielectric properties of the prepared sample at 1580℃ were tested using a network analyzer. r =7.20, Q×f =112056GHz, τ f = -53.68ppm / ℃. Specific Implementation Example 2:

[0059] Based on Specific Example 1, CaTiO3 was added, and microwave dielectric ceramic materials were prepared by solid-state sintering to adjust the temperature coefficient of the resonant frequency. The specific implementation steps are as follows:

[0060] (1) Weigh a certain amount of talc and MgO powder according to the chemical formula Mg2SiO4, add anhydrous ethanol, and perform a first wet milling with an anhydrous ethanol mass ratio of 1:2 for 4 hours and a speed of 550 rpm.

[0061] (2) Place the powder slurry obtained in step (1) into a drying oven and dry it at 85~100℃;

[0062] (3) Place the sieved powder from step (2) into a muffle furnace and pre-fire it at 1200℃ for 2 hours;

[0063] (4) The powder calcined in step (3) is mixed according to the formula Mg2SiO4+15wt%CaTiO3, and anhydrous ethanol is added. The mass ratio of the mixture to anhydrous ethanol is 1:2. The mixture is then wet-milled for 4 hours at a speed of 550 rpm.

[0064] (5) Place the powder slurry obtained in step (4) into a drying oven, dry it at 85~100℃, granulate it with 30% polymethyl methacrylate solution as a binder, pass it through an 80-mesh sieve, and then press it into ceramic green body using a tablet press.

[0065] (6) The green blank from step (5) is sintered at 1420°C for 2 hours.

[0066] (7) The microwave dielectric properties of the prepared sample at 1420℃ were tested using a network analyzer. r =10.05, Q×f =55868GHz, τ f =3.36ppm / ℃.

[0067] In this example, the material exhibits excellent overall dielectric properties ε when the sintering temperature is 1420℃. r =10.05, Q×f=55868GHz, τ f =3.36ppm / ℃, with a near-zero temperature coefficient of resonant frequency and excellent dielectric properties. Specific Implementation Example 3:

[0069] Based on Specific Example 1, SrTiO3 was added, and microwave dielectric ceramic materials were prepared by solid-state sintering to adjust the temperature coefficient of the resonant frequency. The specific implementation steps are as follows:

[0070] (1) Weigh a certain amount of talc and MgO powder according to the chemical formula Mg2SiO4, add anhydrous ethanol, and perform a first wet milling with an anhydrous ethanol mass ratio of 1:2 for 4 hours and a speed of 550 rpm.

[0071] (2) Place the powder slurry obtained in step (1) into a drying oven and dry it at 85~100℃;

[0072] (3) Place the sieved powder from step (2) into a muffle furnace and pre-fire it at 1200℃ for 2 hours;

[0073] (4) The powder calcined in step (3) is mixed according to the formula Mg2SiO4+8wt%SrTiO3, and anhydrous ethanol is added. The mass ratio of the mixture to anhydrous ethanol is 1:2. The mixture is then wet-milled for 4 hours at a speed of 550 rpm.

[0074] (5) Place the powder slurry obtained in step (4) into a drying oven, dry it at 85~100℃, granulate it with 30% polymethyl methacrylate solution as a binder, pass it through an 80-mesh sieve, and then press it into ceramic green body using a tablet press.

[0075] (6) The green blank from step (5) is sintered at 1400℃ for 2 hours.

[0076] (7) The microwave dielectric properties of the prepared sample at 1400℃ were tested using a network analyzer. r =7.99, Q×f =45074GHz, τ f =-3.00ppm / ℃.

[0077] In this example, the material exhibits excellent overall dielectric properties ε when sintered at a temperature of 1400°C. r =7.99, Q×f =45074GHz, τ f =-3.00ppm / ℃, the temperature coefficient of the resonant frequency is close to zero, but the dielectric properties are severely deteriorated compared with Specific Example 2. Specific Implementation Example 4:

[0079] Based on specific embodiments 1 and 2, LiF was added to prepare microwave dielectric ceramic materials via solid-state sintering, thus lowering the sintering temperature. The specific implementation steps are as follows:

[0080] (1) Weigh a certain amount of talc and MgO powder according to the chemical formula Mg2SiO4, add anhydrous ethanol, and perform a first wet milling with an anhydrous ethanol mass ratio of 1:2 for 4 hours and a speed of 550 rpm.

[0081] (2) Place the powder slurry obtained in step (1) into a drying oven and dry it at 85~100℃;

[0082] (3) Place the sieved powder from step (2) into a muffle furnace and pre-fire it at 1200℃ for 2 hours;

[0083] (4) The powder calcined in step (3) is mixed according to the formula Mg2SiO4+15wt%CaTiO3+7.5wt%LiF, and anhydrous ethanol is added. The mass ratio of the mixture to anhydrous ethanol is 1:2. The mixture is then wet-milled for 4 hours at a speed of 550 rpm.

[0084] (5) Place the powder slurry obtained in step (4) into a drying oven, dry it at 85~100℃, granulate it with 30% polymethyl methacrylate solution as a binder, pass it through an 80-mesh sieve, and then press it into ceramic green body using a tablet press.

[0085] (6) The green blank from step (5) is sintered at 875°C for 2 hours.

[0086] (7) The microwave dielectric properties of the prepared sample at 875℃ were tested using a network analyzer, ε r=9.12, Q×f =77467GHz, τ f =-28.18ppm / ℃.

[0087] As shown in Table 1, this invention provides a method for preparing low-cost, low-dielectric-constant, high-performance microwave dielectric ceramic materials via solid-state sintering. Its dielectric constant ε... r =7.20~10.05, quality factor Q×f =45074~112056GHz, temperature coefficient of resonant frequency τ f =-53.68~3.36ppm / ℃.

[0088] Table 1

[0089]

[0090] Using Mg2SiO4 prepared from talc and MgO as the matrix, CaTiO3 or SrTiO3 is added to adjust the temperature stability; while CaTiO3 is used to adjust the temperature coefficient, LiF is added to lower the sintering temperature. The microwave dielectric ceramic Mg2SiO4+xwt%CaTiO3 / ywt%SrTiO3+zwt%LiF prepared by solid-state sintering exhibits low dielectric constant, low loss, low sintering temperature, and ultra-high Q×f value. By replacing silicon and magnesium raw materials with talc, the production cost is reduced while lowering the sintering temperature to 875℃, providing a feasible path for the industrial production of high-performance microwave dielectric ceramics produced by low-temperature co-firing.

[0091] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A low-cost, low-dielectric-performance microwave dielectric ceramic material preparation method, characterized in that, Includes the following steps: Talc and MgO were mixed and then anhydrous ethanol was added. The mixture was then placed in a ball mill for the first wet milling to obtain a slurry. The slurry is placed in a drying oven and dried. The dried slurry powder is sieved and then placed in a muffle furnace for pre-firing. After cooling the pre-calcined powder, add CaTiO3 or SrTiO3, LiF and anhydrous ethanol for a second wet milling. The slurry after the second wet milling is dried, sieved, granulated, and pressed into ceramic green bodies. The ceramic green body is sintered to obtain a microwave dielectric ceramic material.

2. The method for preparing low-cost, low-dielectric-performance microwave dielectric ceramic materials as described in claim 1, characterized in that, Talc and MgO were mixed and then anhydrous ethanol was added. The mixture was then subjected to a first wet milling in a ball mill to obtain a slurry. Talc powder was prepared according to the stoichiometric formula Mg2SiO4, and the mass ratio of anhydrous ethanol to Mg2SiO4 was 2:

1. The first wet milling time was 4 hours.

3. The method for preparing low-cost, low-dielectric-performance microwave dielectric ceramic materials as described in claim 2, characterized in that, The slurry is placed in a drying oven and dried. The drying temperature range is 85–100℃.

4. The method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic materials as described in claim 3, characterized in that, The dried slurry powder is sieved and then placed in a muffle furnace for pre-firing. The sample was sieved through an 80-mesh sieve and placed in a muffle furnace. The pre-firing temperature was 1200℃ and the pre-firing time was 2 hours.

5. The method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic materials as described in claim 4, characterized in that, After cooling the pre-calcined powder, add CaTiO3 or SrTiO3, LiF, and anhydrous ethanol for a second wet milling. After the pre-calcined powder is cooled to room temperature, Mg2SiO4, CaTiO3, SrTiO3, and LiF are mixed in the following proportions: Mg2SiO4 + x wt%CaTiO3 / y wt%SrTiO3 + z wt%LiF, where x = 5–20, y = 6–12, and z = 2.5–10. Add anhydrous ethanol for a second wet milling, which lasts for 4 hours.

6. The method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic materials as described in claim 5, characterized in that, The slurry after the second wet milling is dried, sieved, granulated, and pressed into ceramic green bodies. The drying temperature range is 85–100℃.

7. The method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic material as described in claim 6, characterized in that, The slurry after the second wet milling is dried, sieved, granulated, and pressed into ceramic green bodies. During the drying and granulation process, a 30% polymethyl methacrylate solution is used as a binder.

8. The method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic material as described in claim 7, characterized in that, The ceramic green body is sintered to obtain a microwave dielectric ceramic material, wherein: The sintering temperature of the ceramic green body is 800℃~950℃, 1320℃~1440℃ or 1520℃~1600℃, and the sintering time is 2 hours.

9. A low-cost, low-dielectric, high-performance microwave dielectric ceramic material, prepared by the method for preparing low-cost, low-dielectric, high-performance microwave dielectric ceramic material as described in claim 1, characterized in that, The microwave dielectric ceramic material comprises Mg2SiO4 as a matrix, with x wt% CaTiO3 or y wt% SrTiO3 and z wt% LiF added, wherein x is 5-20, y is 6-12, and z is 2.5-10, and the Mg2SiO4 matrix is ​​prepared from 4000 mesh talc powder and MgO.

10. The low-cost, low-dielectric, high-performance microwave dielectric ceramic material as described in claim 9, characterized in that, The dielectric constant ε of the microwave dielectric ceramic material r The frequency range is 6.21-11.10, the quality factor Q×f is 14420~112056GHz, and the temperature coefficient of resonant frequency τ is... f The range is -58.25 to 41.17 ppm / ℃.

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