Ca-based low dielectric microwave dielectric ceramic and preparation method thereof

Abstract

The application provides a Ca-based low-dielectric microwave dielectric ceramic and a preparation method thereof, which is prepared from a compound with a chemical formula of xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge), and the main crystal phase of the compound has a chemical formula of Ca4MAl2N3O 14 (M is Mg or Zn; N is Si or Ge). The Ca-based low-dielectric microwave dielectric ceramic prepared by the above method overcomes the defects in the synthesis of low-dielectric microwave dielectric ceramics in the prior art, has the characteristics of low dielectric constant and high quality factor, has the advantages of simple synthesis process and stable main crystal phase composition, and is a low-dielectric microwave dielectric ceramic material suitable for millimeter wave communication.

Description

Technical Field

[0001] This invention relates to the field of low-dielectric microwave dielectric ceramics, and more particularly to a Ca-based low-dielectric microwave dielectric ceramic and its preparation method. Background Technology

[0002] With the rapid development of communication technology, traditional metal cavity filters, resonators, waveguides, and other components can no longer meet the needs of modern communication due to their large size, high dielectric loss, and poor thermal stability. While microwave components made of high-dielectric-constant microwave dielectric ceramics can meet the miniaturization requirements, their high dielectric loss and poor thermal stability limit their application in high-frequency fields. High-dielectric-constant microwave dielectric ceramics are no longer sufficient to meet the current demands for high speed, low latency, and high thermal stability in communication. There is an urgent need to develop new ceramic materials with low dielectric constants (<15) and high quality factors to meet the needs of high-frequency communication. In particular, the upcoming millimeter-wave and terahertz communications will create a huge demand for low-dielectric-constant microwave dielectric materials.

[0003] Due to their abundant silicon-oxygen and germanium-oxygen tetrahedral structures, and the high bond strength and covalent ratio of Si-O and Ge-O bonds, silicate and germanate ceramics exhibit low dielectric constants. Their stable tetrahedral chain structure and high ionic covalent ratio also contribute to their high quality factors. To enrich the variety of low-dielectric microwave dielectric ceramics and develop a wider range of high-performance, low-cost low-dielectric microwave dielectric ceramics suitable for high-frequency communication, it is necessary to continuously explore novel microwave dielectric ceramic compositions and preparation methods that combine low dielectric constants and high quality factors within the silicate and germanate ceramic system.

[0004] In view of this, it is necessary to explore novel low-dielectric microwave dielectric ceramic compositions and design an improved method for preparing low-dielectric microwave dielectric ceramics in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing Ca-based low-dielectric microwave dielectric ceramics. The Ca-based low-dielectric microwave dielectric ceramics prepared by this method have a sintering temperature between 1150 and 1350°C and exhibit low dielectric constant and high quality factor. The development of this Ca-based low-dielectric microwave dielectric ceramic broadens the selection range of low-dielectric-constant microwave dielectric ceramic materials.

[0006] To achieve the above-mentioned objective, this invention provides a Ca-based low-dielectric microwave dielectric ceramic, which is prepared using a compound with the chemical formula xCaO-yMO-zAl3O2-kNO2, wherein 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, and 2≤k≤4, and the chemical expression of the main crystalline phase of the Ca-based low-dielectric microwave dielectric ceramic is Ca4MAl2N3O14 Where M is Mg or Zn; N is Si or Ge.

[0007] Preferably, M is Mg, N is Ge, x = 4, y = 1, z = 2, and k = 3.

[0008] Preferably, the dielectric constant ε of the Ca-based low-dielectric microwave dielectric ceramic is... r The range is 8.3 to 9.6, and the quality factor Q×f is 6000 to 13400 GHz.

[0009] To achieve the above-mentioned objectives, the present invention also provides a method for preparing Ca-based low-dielectric microwave dielectric ceramics, comprising the following steps:

[0010] S1. Weigh CaCO3, MO (M is Mg or Zn), Al3O2 and NO2 (N is Si or Ge) as raw materials and mix them according to the stoichiometric ratio of the chemical formula xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge). After mixing evenly, perform a first wet ball milling treatment, and then dry and pre-fire to obtain pre-fired ceramic powder; wherein, 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, 2≤k≤4;

[0011] S2. The pre-fired ceramic powder obtained in step S1 is subjected to a second wet ball milling process. After ball milling, the powder is dried, granulated with binder, pressed into sheets, and then sintered to obtain Ca-based low-dielectric microwave dielectric ceramic.

[0012] Preferably, in step S1, the pre-firing temperature is 900–1050°C and the pre-firing time is 5–10 hours.

[0013] Preferably, in step S2, the sintering temperature is 1150–1350°C and the sintering time is 5–10 h.

[0014] Preferably, in step S1, the dispersant for the first wet ball milling treatment is deionized water, the amount of which is twice the mass of the powder, the ball milling medium is zirconium balls, the ball milling speed is 360 r / min, and the ball milling time is 5 to 10 h.

[0015] Preferably, in step S2, the dispersant for the second wet ball milling process is deionized water, and its amount is twice the mass of the powder.

[0016] Preferably, in step S2, the adhesive is PVA or paraffin.

[0017] Preferably, in step S2, the amount of the binder added is 5-10% of the mass ratio of the ceramic powder.

[0018] Preferably, in step S2, the milling medium for the second wet ball milling treatment is zirconium balls, and the ball milling process is to mill at a speed of 360 r / min for 5 to 10 hours.

[0019] The beneficial effects of this invention are:

[0020] The Ca-based low-dielectric microwave dielectric ceramic provided by this invention uses a compound with the chemical formula xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge) to prepare the Ca-based low-dielectric microwave dielectric ceramic. This method overcomes the shortcomings of existing technologies in preparing low-dielectric-constant microwave dielectric ceramics at lower sintering temperatures. The resulting Ca-based low-dielectric microwave dielectric ceramic simultaneously possesses the characteristics of lower sintering temperature, lower dielectric constant, and higher quality factor. The low dielectric constant reduces the interactive coupling loss between the material and the electrode and improves the transmission rate of electrical signals. The high quality factor reduces system losses and improves the frequency selectivity of the material. Furthermore, Ca4MAl2N3O... 14 Ca-based low-dielectric microwave dielectric ceramics with (M being Mg or Zn; N being Si or Ge) as the main crystalline phase have the advantages of stable main phase composition, good batch stability, and suitability for large-scale production. They have comprehensive performance superior to existing commercial materials and are a promising material for application. Attached Figure Description

[0021] Figure 1 Images of sintered samples of Ca-based low-dielectric microwave dielectric ceramics prepared in Examples 1-4 of this invention;

[0022] Figure 2 XRD pattern of Ca-based low-dielectric microwave dielectric ceramic prepared in Example 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of the crystal structure of the main crystal phase of the low-dielectric Ca-based low-dielectric microwave dielectric ceramic prepared in Example 1 of the present invention.

[0024] Figure 4 SEM image of the Ca-based low-dielectric microwave dielectric ceramic prepared in Example 1 of the present invention;

[0025] Figure 5 SEM image of the Ca-based low-dielectric microwave dielectric ceramic prepared in Example 4 of the present invention;

[0026] Figure 6 SEM image of the Ca-based low-dielectric microwave dielectric ceramic prepared in Example 5 of the present invention;

[0027] Figure 7 SEM image of the Ca-based low-dielectric microwave dielectric ceramic prepared in Example 8 of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0030] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] This invention provides the application of a compound in the preparation of Ca-based low-dielectric microwave dielectric ceramics. The chemical formula of the compound is xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge), wherein 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, 2≤k≤4, and the chemical expression of the main crystalline phase of the Ca-based low-dielectric microwave dielectric ceramic is Ca4MAl2N3O 14 (M is Mg or Zn; N is Si or Ge). The dielectric constant ε of the microwave dielectric ceramic material prepared using the above compounds is... r The range is 8.3 to 9.6, and the quality factor Q×f is 6000 to 13400 GHz.

[0032] This invention also provides the application of the above chemical formula Ca4MAl2N3O 14 A method for preparing microwave dielectric ceramics from compounds (M is Mg or Zn; N is Si or Ge) is described below:

[0033] S1. Weigh CaCO3, MO (M is Mg or Zn), Al3O2 and NO2 (N is Si or Ge) as raw materials and mix them according to the stoichiometric ratio of the chemical formula xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge), where 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, 2≤k≤4; after mixing evenly, perform a first wet ball milling treatment, and then dry and pre-fire to obtain pre-fired ceramic powder.

[0034] S2, the pre-fired ceramic powder obtained in step S1 is subjected to a second wet ball milling process. After ball milling, it is dried and granulated with a binder. After pressing into sheets, it is sintered to obtain Ca-based low-dielectric microwave dielectric ceramic.

[0035] In step S1, the dispersant for the first wet ball milling treatment is 200wt% deionized water, that is, the amount of deionized water is twice the mass of the powder; the ball milling medium is zirconium balls, the ball milling speed is 360 r / min, and the ball milling time is 5 to 10 h.

[0036] In step S1, the pre-firing temperature is 900-1050℃ and the pre-firing time is 5-10h.

[0037] In step S2, the dispersant for the second wet ball milling treatment is 200 wt% deionized water, the milling medium is zirconium balls, and the milling process is ball milling at a speed of 360 r / min for 5–10 h. The sintering temperature is 1150–1350 °C, and the sintering time is 5–10 h.

[0038] In step S2, the binder is PVA (polyvinyl alcohol) or paraffin wax, and the amount of binder added during granulation is 5-10% of the mass of ceramic powder.

[0039] The preparation method of the ultra-low dielectric constant silicon-based microwave dielectric ceramic of the present invention will be further explained below with reference to specific embodiments:

[0040] Example 1

[0041] This embodiment prepares a Ca-based low-dielectric microwave dielectric ceramic, and the specific preparation method is as follows:

[0042] S1. CaCO3, MO, Al3O2, and NO2 with a purity of 99.9% are mixed according to the stoichiometric ratio of xCaO-yMO-zAl3O2-kNO2, where M is Mg, N is Si, x=4, y=1, z=2, and k=3. After uniform mixing, zirconium balls are used as the ball milling medium and deionized water is used as the dispersant. The powder is mixed and stirred in a ball mill for 5 hours at a speed of 360 r / min for the first wet ball milling treatment. The obtained slurry is dried and pre-fired at 1000℃ for 5 hours to obtain pre-fired ceramic powder.

[0043] S2. The pre-fired ceramic powder obtained in step S1 is subjected to a second wet ball milling treatment. After ball milling, it is dried to obtain ceramic powder. Then, 8% by mass of polyvinyl alcohol is added to the ceramic powder as a binder for granulation. The powder is pressed into cylindrical green samples with a thickness-to-diameter ratio of 0.4 to 0.6 under a pressure of 150 MPa. After pressing, the samples are sintered in air at 1200℃ for 5 hours to obtain Ca-based low-dielectric microwave dielectric ceramic. The conditions of the second wet ball milling treatment are the same as those of the first wet ball milling treatment.

[0044] The sintered sample of the Ca-based low-dielectric microwave dielectric ceramic prepared in this embodiment is shown in the figure below. Figure 1 As shown, the sintered sample exhibits good ceramic-forming properties; Figure 2 As shown, the main crystalline phase in the sintered Ca-based low-dielectric microwave dielectric ceramic is Ca4MAl2N3O. 14 (M is Mg; N is Si), and the phase composition is almost free of other impurities; such as Figure 3 As shown, the crystal structure contains a large number of hinged binary tetrahedral six-membered ring structures, indicating that the Ca-based low-dielectric microwave dielectric ceramic contains a large number of Si-O bonds or Ge-O bonds. The high covalent bond content of Si-O and Ge-O bonds suggests that the Ca-based low-dielectric microwave dielectric ceramic may have a low dielectric constant.

[0045] The SEM image of the Ca-based low-dielectric microwave dielectric ceramic prepared in this embodiment is shown below. Figure 4 As shown, Ca4MAl2N3O 14 The surface microstructure of the ceramic (M is Mg; N is Si) is very dense and free of pores, indicating the excellent sintering characteristics of this novel Ca-based low-dielectric microwave dielectric ceramic.

[0046] Examples 2 to 10

[0047] The only differences between Examples 2 to 10 and Example 1 are the values ​​of x, y, z, and k in the compound and the sintering temperature. The other steps are basically the same as in Example 1 and will not be repeated here. The properties of the Ca-based low-dielectric microwave dielectric ceramics prepared in Examples 1 to 10 are shown in Table 1. The Ca-based low-dielectric microwave dielectric ceramics have a dielectric constant ε. r The GHz band ratio is 8.3–9.6, and the quality factor Q×f is 6000–13400 GHz; due to Ca4MAl2N3O 14 The crystal structure of the (M is Mg or Zn; N is Si or Ge) phase contains oxygen tetrahedral rings, thus exhibiting good thermal stability; secondly, the Ca4MAl2N3O phase... 14(M is Mg or Zn; N is Si or Ge) Ca-based low-dielectric microwave dielectric ceramics, which are the main crystalline phase, do not contain easily variable valence elements, are not prone to deliquescence, and have a low sintering temperature. Therefore, they can be used as candidate materials for the preparation of dielectric components and for electronic packaging.

[0048] Table 1. Performance comparison of Ca-based low-dielectric microwave dielectric ceramics prepared in Examples 1 to 10

[0049]

[0050]

[0051] like Figure 5-7 The figures shown are Ca4MAl2N3O prepared in Examples 4, 5, and 8, respectively. 14 The SEM image of the ceramic (M is Mg or Zn; N is Si or Ge) shows that its surface microstructure is very dense and without pores, indicating the excellent sintering characteristics of this novel Ca-based low-dielectric microwave dielectric ceramic.

[0052] In summary, the Ca-based low-dielectric microwave dielectric ceramic proposed in this invention uses a compound with the chemical formula xCaO-yMO-zAl3O2-kNO2 (M is Mg or Zn; N is Si or Ge) to prepare Ca-based low-dielectric microwave dielectric ceramics. The resulting Ca-based low-dielectric microwave dielectric ceramics possess both low dielectric constant and high quality factor, exhibiting superior overall performance compared to existing commercial materials, making them a material with great application potential.

[0053] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A Ca-based low-dielectric microwave dielectric ceramic, characterized in that, The Ca-based low-dielectric microwave dielectric ceramic is prepared using a compound with the chemical formula xCaO-yMO-zAl3O2-kNO2; wherein 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, 2≤k≤4, and the chemical expression of the main crystalline phase of the Ca-based low-dielectric microwave dielectric ceramic is Ca4MAl2N3O 14 Where M is Mg or Zn; N is Si or Ge.

2. The Ca-based low-dielectric microwave dielectric ceramic according to claim 1, characterized in that, The dielectric constant ε of the Ca-based low-dielectric microwave dielectric ceramic r The range is 8.3 to 9.6, and the quality factor Q×f is 6000 to 13400 GHz.

3. The Ca-based low-dielectric microwave dielectric ceramic according to claim 1, characterized in that, M is Mg, N is Ge, x = 4, y = 1, z = 2, k = 3.

4. A method for preparing Ca-based low-dielectric microwave dielectric ceramic according to any one of claims 1-3, characterized in that, Includes the following steps: S1, weigh CaCO3, MO, Al3O2 and NO2 as raw materials and mix them according to the stoichiometric ratio of xCaO-yMO-zAl3O2-kNO2. After mixing evenly, perform a first wet ball milling treatment, and then dry and pre-fire to obtain pre-fired ceramic powder; wherein, M is Mg or Zn; N is Si or Ge; 3.5≤x≤4.5, 0.5≤y≤1.5, 1.5≤z≤2.5, 2≤k≤4; S2, the pre-fired ceramic powder obtained in step S1 is subjected to a second wet ball milling process. After ball milling, it is dried and granulated with a binder. After pressing into sheets, it is sintered to obtain Ca-based low-dielectric microwave dielectric ceramic.

5. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 4, characterized in that, In step S1, the pre-firing temperature is 900-1050°C, and the pre-firing time is 5-10 hours.

6. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 4, characterized in that, In step S2, the sintering temperature is 1150–1350°C, and the sintering time is 5–10 h.

7. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 4, characterized in that, In step S1, the dispersant for the first wet ball milling treatment is deionized water, the ball milling medium is zirconium balls, and the ball milling time is 5 to 10 hours.

8. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 4, characterized in that, In step S2, the dispersant for the second wet ball milling treatment is deionized water.

9. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 4, characterized in that, In step S2, the adhesive is PVA or paraffin.

10. The method for preparing Ca-based low-dielectric microwave dielectric ceramics according to claim 9, characterized in that, In step S2, the amount of the binder added is 5-10% of the mass ratio of the ceramic powder.

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