Low dielectric constant microwave dielectric ceramic material with low thermal expansion coefficient and adjustable resonance frequency temperature coefficient, preparation method and application

Abstract

The application belongs to the technical field of wireless communication and electronic ceramic material, and relates to a low dielectric constant microwave dielectric ceramic material with low thermal expansion coefficient and adjustable resonant frequency temperature coefficient, a preparation method and application thereof. The low dielectric constant microwave dielectric ceramic material with low thermal expansion coefficient and adjustable resonant frequency temperature coefficient has a chemical formula of ZrSiO4.xTiO2, wherein 0wt% < x <= 7wt%. The preparation method of the microwave dielectric ceramic material comprises the following steps: step (1), taking ZrSiO4 and TiO2 as raw materials, the purity of the raw materials is greater than 99%, the raw materials are weighed according to the proportion of each element in the target chemical formula ZrSiO4.xTiO2, wherein 0wt% < x <= 7wt%; the weighed raw materials are sequentially mixed, ball milled and dried to obtain a powder; step (2), the powder obtained in step (1) is granulated, sieved and formed to obtain a green body; and step (3), the green body obtained in step (2) is sintered at 1350-1500 DEG C to obtain a ceramic.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wireless communication and electronic ceramic materials, and particularly relates to a low dielectric constant microwave dielectric ceramic material with low thermal expansion coefficient and adjustable resonant frequency temperature coefficient, and a preparation method and application thereof. BACKGROUND

[0002] With the further development of electronic information products in the direction of wideband, miniaturization, integration and green, especially the rapid advancement of communication technology in the direction of 5G / 6G, the characteristics of low latency, high speed, high integration and low power consumption require dielectric materials to have low dielectric constant, low dielectric loss and high temperature stability. For example, the antenna substrate in wireless communication usually adopts low dielectric constant polymer dielectric materials such as epoxy resin, polytetrafluoroethylene and high-density polyethylene, which have relatively low dielectric loss and are easy to process into various shapes. However, the polymer dielectric material has high thermal expansion coefficient, low thermal conductivity and poor heat resistance, especially not very ideal at high frequency. Compared with polymer materials, low dielectric constant (<20) microwave dielectric ceramics generally have relatively lower dielectric loss, relatively lower thermal expansion coefficient, higher thermal conductivity and excellent mechanical strength, and can be widely used in radio frequency devices, base stations, radars, antennas, satellite communications and other industries.

[0003] Zirconium silicate (ZrSiO4) microwave dielectric ceramic material has low dielectric constant, low dielectric loss and good mechanical properties and chemical stability. In addition, it has abundant raw materials and low production cost, and has attracted much attention in the field of high-frequency communication in recent years. Varghese et al. previously proposed that ZrSiO4 can be applied to microwave integrated circuit applications. Therefore, it is of great value and significance to develop zirconium silicate microwave dielectric ceramic material, which is a very potential material in the field of industrial technology. However, the reported ZrSiO4 microwave dielectric ceramic has low density, and the resonant frequency temperature coefficient is a large negative number, which limits its application. SUMMARY

[0004] In order to solve the problems of low relative density and large negative resonant frequency temperature coefficient of ZrSiO4 microwave dielectric ceramic in the prior art, the application introduces an appropriate amount of TiO2, which is beneficial to the densification process of the ceramic. At the same time, the positive resonant frequency temperature coefficient is used to compensate and coordinate, and near-zero resonant frequency temperature coefficient and adjustable characteristics are obtained, and more dense ceramic is obtained, so as to optimize the microwave dielectric properties, and finally a low dielectric constant microwave dielectric ceramic material with low thermal expansion coefficient and adjustable resonant frequency temperature coefficient and a preparation method thereof are found.

[0005] The present invention provides a low dielectric constant microwave dielectric ceramic material with a low thermal expansion coefficient and an adjustable temperature coefficient of resonant frequency, having a chemical formula of ZrSiO4·xTiO2, where 0 wt% < x ≤ 7 wt%.

[0006] Preferably, the dielectric constant of the microwave dielectric ceramic material is 10.1 - 12.7, the dielectric loss is 0.00053 - 0.00065 @ 10 GHz, the adjustable range of the temperature coefficient of resonant frequency Tf is -9.8 - 25.9 ppm / °C, and |Tf| ≤ 10 ppm / °C when 2.5 wt% ≤ x ≤ 5 wt%; within the range of room temperature to 500 °C, the thermal expansion coefficient is 4 ppm / °C.

[0007] The present invention also provides a preparation method for the microwave dielectric ceramic material, comprising the following steps:

[0008] Step (1): Using ZrSiO4 and TiO2 as raw materials, weighing the raw materials according to the proportions of each element in the target chemical formula ZrSiO4·xTiO2, where 0 wt% < x ≤ 7 wt%; mixing, ball milling, and drying the weighed raw materials in sequence to obtain a powder.

[0009] Step (2): Granulating, sieving, and molding the powder obtained in step (1) to obtain a green body. )

[0010] Step (3): Sintering the green body obtained in step (2) at 1350 - 1500 °C to obtain a ceramic.

[0011] Preferably, in step (1), absolute ethanol and zirconium balls are used as ball milling media for ball milling, and the ball milling time is 24 h.

[0012] Preferably, in step (2), the granulation process includes: using an aqueous solution of polyvinyl alcohol with a concentration of 10 wt% as a binder, the addition amount of the binder accounting for 8% of the powder mass, the sieving using a 40 - mesh standard sieve, and the molding including pouring the granulated powder after sieving into a steel mold with a diameter of 12 mm and pressing it into a cylindrical green body with a height of 6 mm and a diameter of 12 mm under a pressure of 80 - 100 MPa.

[0013] Preferably, in step (3), the sintering process includes: heating up to 600 °C at a rate of 2 °C / min for debinding for 2 h, heating up to 1350 - 1500 °C at a rate of 5 °C / min for sintering for 3 h, and cooling down to 800 °C at a rate of 2 °C / min and then cooling to room temperature in the furnace.

[0014] This invention also provides applications of the aforementioned microwave dielectric ceramic material, which is used in the fabrication of any microwave component, including dielectric resonators, filters, and antenna substrates. The performance parameters of the microwave dielectric ceramic material are as follows: dielectric constant of 10.1–12.7, dielectric loss of 0.00053–0.00065@10GHz, and adjustable temperature coefficient of resonant frequency Tf ranging from -9.8 to 25.9ppm / °C, with |Tf| ≤ 10ppm / °C when 2.5wt% ≤ x ≤ 5wt%.

[0015] Preferably, by adjusting the proportion of raw materials weighed in step (1), the temperature coefficient of the resonant frequency of the microwave dielectric ceramic material is adjusted to prepare microwave components with different application performance requirements:

[0016] When the raw materials are weighed according to the chemical formula ZrSiO4·2.5wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is -9.8 to -8.6ppm / ℃.

[0017] When the raw materials are weighed according to the chemical formula ZrSiO4·3.5wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is -3.4 to -1.0ppm / ℃.

[0018] When the raw materials are weighed according to the chemical formula ZrSiO4·4wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is 0.5~3.1ppm / ℃;

[0019] When the raw materials are weighed according to the chemical formula ZrSiO4·5wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is 6.2~9.8ppm / ℃;

[0020] When the raw materials are weighed according to the chemical formula ZrSiO4·7wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is 21.7~25.9ppm / ℃.

[0021] The beneficial effects of this invention are:

[0022] Silicate-based microwave dielectric ceramics are a common material, inexpensive and abundant. They possess low dielectric constant and low dielectric loss characteristics, with Mg₂SiO₄ being a typical example. However, its resonant frequency temperature coefficient is -60 to -70 ppm / °C. To adjust its temperature coefficient closer to zero, many researchers have attempted to add TiO₂. However, TiO₂ reacts with Mg₂SiO₄ to generate byproducts, thus failing to achieve the desired tuning and reducing microwave dielectric properties.

[0023] ZrSiO4 is a kind of silicate material with low dielectric constant, low dielectric loss, good mechanical properties and chemical stability. Although Varghese et al. have proposed that ZrSiO4 can be used in microwave integrated circuits, there is little research on it. The ZrSiO4 microwave dielectric ceramics reported currently usually have low density (relative density < 95%), and the temperature coefficient of resonant frequency is a large negative number, so its application is limited.

[0024] Considering that TiO2 does not react with ZrSiO4, by adding an appropriate amount of TiO2 to ZrSiO4 (ZrSiO4·xTiO2, where 0wt% < x ≤ 7wt%), on the one hand, the density of the ceramic is improved (when x = 4wt%, the relative density reaches 96.5%), and the optimal sintering temperature is reduced (from 1500 °C when x = 0wt% to 1350 °C when x = 7wt%); on the other hand, the temperature coefficient of resonant frequency is adjusted from about -21.5 ppm / °C when x = 0wt% to about 23.8 ppm / °C when x = 7wt%, and when 2.5wt% ≤ x ≤ 5wt%, |Tf| ≤ 10 ppm / °C, achieving the goal of nearly zero temperature coefficient of resonance.

[0025] The thermal expansion coefficient of ZrSiO4·xTiO2 (0wt% < x ≤ 7wt%) is around 4 ppm / °C (within the range of room temperature to 500 °C), which is similar to that of silicon semiconductors, providing advantages for the integrated application of this material in microwave devices.

[0026] By adding TiO2, the microwave dielectric properties of ZrSiO4 microwave dielectric ceramics are optimized; low dielectric constant (10.1 - 12.7) and low dielectric loss (0.00053 - 0.00065 @ 10 GHz) are obtained, and the adjustable range of the temperature coefficient of resonant frequency (Tf) is -9.8 - 25.9 ppm / °C, which can be applied in the 5G / 6G communication field, especially microwave integrated circuits. The above characteristics make this invention have important industrial application value. Description of the Drawings

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art.后文将参照附图以示例性而非限制性的方式详细描述本发明的一些具体实施例。The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0028] Figure 1 It is the curve of the relative density of Comparative Example 1 and Examples 1 - 5 changing with the sintering temperature;

[0029] Figure 2 Microwave dielectric properties (dielectric constant, Qf value and temperature coefficient of resonant frequency) of Comparative Example 1 and Examples 1-5. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. In this invention, unless otherwise specified, the raw materials and equipment used are commercially available or commonly used in the art. The methods in the embodiments, unless otherwise specified, are conventional methods in the art.

[0031] The present invention will be further illustrated below with reference to examples and comparative examples.

[0032] Example 1:

[0033] ZrSiO4·2.5wt%TiO2 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0034] (1) Weighing and mixing: Weigh and mix ZrSiO4 and TiO2 raw materials (both with a purity greater than 99%) according to the chemical formula ZrSiO4·2.5wt%TiO2;

[0035] (2) Mixing, ball milling, drying, sieving, granulation and molding: The weighed raw materials are placed in a ball mill jar, and anhydrous ethanol and zirconium dioxide balls are added as the ball milling media for 24 hours. After ball milling, the raw materials are dried at 80℃ for 24 hours, sieved through a 120-mesh standard sieve, and granulated using a 10wt% polyvinyl alcohol (PVA) aqueous solution as a binder. The granulated powder is poured into a steel mold with a diameter of 12mm and pressed into a green body with a diameter of 12mm and a height of 4-6mm under a pressure of 98MPa.

[0036] (3) Sintering: The green body is heated from room temperature to 600℃ at a rate of 2℃ / min and held for 2h. Then the binder is removed. The temperature is then increased to 1325℃~1525℃ at a rate of 5℃ / min and held for 3h. The temperature is then reduced to 800℃ at a rate of 2℃ / min and cooled in the furnace to obtain microwave dielectric ceramic.

[0037] In this embodiment, the dielectric constant is 10.1 to 10.5, the dielectric loss is 0.00055 to 0.00057 @ 10 GHz, and the temperature coefficient of the resonant frequency is -9.8 to -8.6 ppm / ℃.

[0038] Example 2

[0039] ZrSiO4·3.5wt%TiO2 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0040] Steps (2) and (3) are the same as in Example 1. The difference is that in this example, the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·3.5wt%TiO2.

[0041] In this embodiment, the dielectric constant is 10.8 to 11.4, the dielectric loss is 0.00055 to 0.00063 @ 10 GHz, and the temperature coefficient of the resonant frequency is -3.4 to -1.0 ppm / ℃.

[0042] Example 3

[0043] ZrSiO4·4wt%TiO2 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0044] Steps (2) and (3) are the same as in Example 1. The difference is that in this example, the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·4wt%TiO2.

[0045] In this embodiment, the dielectric constant is 11.2 to 11.8, the dielectric loss is 0.00053 to 0.00055 @ 10 GHz, and the temperature coefficient of the resonant frequency is 0.5 to 3.1 ppm / ℃.

[0046] Example 4

[0047] ZrSiO4·5wt%TiO2 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0048] Steps (2) and (3) are the same as in Example 1. The difference is that in this example, the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·5wt%TiO2.

[0049] In this embodiment, the dielectric constant is 11.6–12.0, the dielectric loss is 0.00058–0.00062@10GHz, and the temperature coefficient of the resonant frequency is 6.2–9.8ppm / ℃.

[0050] Example 5

[0051] ZrSiO4·7wt%TiO2 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0052] Steps (2) and (3) are the same as in Example 1. The difference is that in this example, the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·7wt%TiO2.

[0053] In this embodiment, the dielectric constant is 12.1 to 12.7, the dielectric loss is 0.00063 to 0.00065 at 10 GHz, and the temperature coefficient of the resonant frequency is 21.7 to 25.9 ppm / ℃.

[0054] Example 6

[0055] The application of microwave dielectric ceramic materials is characterized in that the microwave dielectric ceramic materials are used in the preparation of any microwave component such as dielectric resonator, filter, and antenna substrate. The microwave dielectric ceramic materials are prepared according to the method described in Example 1. By modifying the ratio of raw materials in step (1) of Example 1 and changing the mass percentage of TiO2, the resonant frequency temperature coefficient of the microwave dielectric ceramic materials can be adjusted, thereby preparing microwave components with different application performance requirements.

[0056] When the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·2.5wt%TiO2, the temperature coefficient of the resonant frequency of the microwave component is -9.8 to -8.6ppm / ℃.

[0057] When the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·3.5wt%TiO2, the temperature coefficient of the resonant frequency of the microwave component is -3.4 to -1.0ppm / ℃.

[0058] When the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·4wt%TiO2, the temperature coefficient of the resonant frequency of the microwave component is 0.5~3.1ppm / ℃;

[0059] When the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·5wt%TiO2, the temperature coefficient of the resonant frequency of the microwave component is 6.2~9.8ppm / ℃;

[0060] When the raw materials in step (1) are weighed according to the chemical formula ZrSiO4·7wt%TiO2, the temperature coefficient of the resonant frequency of the microwave component is 21.7~25.9ppm / ℃.

[0061] Comparative Example 1:

[0062] ZrSiO4 microwave dielectric ceramic material and its preparation method, the preparation process includes the following steps:

[0063] (1) Weighing and mixing: Weigh and mix the ZrSiO4 raw material (purity greater than 99%);

[0064] (2) Ball milling, drying, sieving, granulation and molding: The weighed raw materials are placed in a ball mill jar, and anhydrous ethanol and zirconium dioxide balls are added as the ball milling media for 24 hours. After ball milling, the raw materials are dried at 80℃ for 24 hours, sieved through a 120-mesh standard sieve, and granulated using a 10wt% polyvinyl alcohol (PVA) aqueous solution as a binder. The granulated powder is poured into a steel mold with a diameter of 12mm and pressed into a green body with a diameter of 12mm and a height of 4-6mm under a pressure of 98MPa.

[0065] (3) Sintering: The green body is heated from room temperature to 600℃ at a rate of 2℃ / min and held for 2h. Then the binder is removed. The temperature is then increased to 1325℃~1525℃ at a rate of 5℃ / min and held for 3h. The temperature is then reduced to 800℃ at a rate of 2℃ / min and cooled in the furnace to obtain microwave dielectric ceramic.

[0066] The dielectric constant of this comparative example is 8.9–9.3, the dielectric loss is 0.00040–0.00053@10GHz, and the temperature coefficient of the resonant frequency is 21.7–25.9ppm / ℃.

[0067] Appendix Figure 1 The relative density curves of Comparative Example 1 and Examples 1-5 as a function of sintering temperature are shown. It can be seen that the maximum relative density of ZrSiO4 in the Comparative Example is only 93%. By adding TiO2, the relative density of all examples is increased, with the maximum relative density of Examples 1-5 all exceeding 95%. In other words, adding TiO2 can effectively improve the density of ZrSiO4 ceramics.

[0068] Appendix Figure 2 The microwave dielectric properties (dielectric constant, dielectric loss, and temperature coefficient of resonant frequency) of Comparative Example 1 and Examples 1-5 are shown. It can be observed that the dielectric constant of the samples increases with the addition of TiO2; the dielectric constant of the Comparative Example is 9.1, while that of the Examples increases from 10.3 to 12.4. The addition of TiO2 has little effect on the dielectric loss, which generally remains between 0.0004 and 0.0006, with the dielectric loss of the Examples being slightly higher than that of the Comparative Example. Regarding the temperature coefficient of resonant frequency, it can be observed that it increases almost linearly with the addition of TiO2, increasing from -21.5 to 23.8, achieving |Tf| ≤ 10 ppm / °C at 2.5 wt% ≤ x ≤ 5 wt%.

Claims

1. The application of a low-dielectric-constant microwave dielectric ceramic material with a low coefficient of thermal expansion and an adjustable temperature coefficient of resonant frequency, characterized in that, The microwave dielectric ceramic material is applied to the preparation of any one of microwave components such as dielectric resonators, filters, and antenna substrates. The application performance parameters of the microwave dielectric ceramic material are as follows: the dielectric constant is 10.1 - 12.7, the dielectric loss is 0.00053 - 0.00065 @ 10 GHz, the adjustable range of the resonance frequency temperature coefficient Tf is -9.8 - 25.9 ppm / °C, and when 2.5 wt% ≤ x < 5 wt%, |Tf| ≤ 10 ppm / °C; The chemical formula of the microwave dielectric ceramic material is ZrSiO4•xTiO2, where 0 wt% < x < 5 wt% or 5 wt% < x ≤ 7 wt%.

2. According to the application described in claim 1, the features are as follows: In the range of room temperature to 500 °C, the thermal expansion coefficient is 4 ppm / °C.

3. The application according to claim 1, characterized in that, The preparation method of the microwave dielectric ceramic material includes the following steps: Step (1): Using ZrSiO4 and TiO2 as raw materials, weigh the raw materials according to the proportion of each element in the target chemical formula ZrSiO4•xTiO2, where 0 wt% < x < 5 wt% or 5 wt% < x ≤ 7 wt%; mix, ball-mill, and dry the weighed raw materials in sequence to obtain powder. Step (2): Granulate, screen, and mold the powder obtained in step (1) to obtain a green body. Step (3): Sinter the green body obtained in step (2) at 1350 - 1500 °C to obtain a ceramic.

4. The application according to claim 3, characterized in that, In step (1), anhydrous ethanol and zirconium balls are used as ball-milling media for ball-milling, and the ball-milling time is 24 h.

5. The application according to claim 3, characterized in that, In step (2), the granulation process includes: using an aqueous solution of polyvinyl alcohol with a concentration of 10 wt% as a binder, the addition amount of the binder accounts for 8% of the powder mass, the screening uses a 40-mesh standard sieve, and the molding includes pouring the granulated powder after screening into a steel mold with a diameter of 12 mm and pressing it into a cylindrical blank with a height of 6 mm and a diameter of 12 mm under a pressure of 80 - 100 MPa.

6. The application of the microwave dielectric ceramic material according to claim 3, characterized in that, In step (3), the sintering process includes: heating at a rate of 2 °C / min to 600 °C for degumming for 2 h, heating at a rate of 5 °C / min to 1350 - 1500 °C for sintering for 3 h, and cooling at a rate of 2 °C / min to 800 °C and then cooling with the furnace to room temperature. Its features are, 7. According to the application of the microwave dielectric ceramic material described in claim 3, By adjusting the ratio of raw material weighing in step (1), the resonance frequency temperature coefficient of the microwave dielectric ceramic material is adjusted to prepare microwave components with different application performance requirements: When the raw materials are weighed according to the chemical formula ZrSiO4•A.5 wt%TiO2 in step (1), the resonance frequency temperature coefficient of the microwave component is -9.8 - -8.6 ppm / °C; When the raw materials are weighed according to the chemical formula ZrSiO4•3.5 wt%TiO2 in step (1), the resonance frequency temperature coefficient of the microwave component is -3.4 - -1.0 ppm / °C; When the raw materials are weighed according to the chemical formula ZrSiO4•4 wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is 0.5~3.1ppm / ℃; When the raw materials are weighed according to the chemical formula ZrSiO4•7 wt%TiO2 in step (1), the temperature coefficient of the resonant frequency of the microwave component is 21.7~25.9ppm / ℃.

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