Dielectric ceramic material and method of manufacture

Abstract

The application relates to the field of ceramic preparation and discloses a dielectric ceramic material and a preparation method, which comprises the following steps: S1, preparing Mg2Al4(Si 1‑x Ge x )5O 18 powder; wherein 0 18 x<=0.5; S2, preparing a titanium oxide-containing suspension; adding the titanium oxide-containing suspension and / or titanium oxide powder into the powder prepared in the step S1, and sintering to obtain the dielectric ceramic material. In the method, the silicon element in the traditional cordierite is partially replaced by germanium element, and the titanium oxide-containing suspension and / or titanium oxide powder is added, so that the target of high Qf and near zero TCF value is greatly achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic preparation, in particular to a dielectric ceramic material and a preparation method. BACKGROUND

[0002] Cordierite (Mg2Al4Si5O 18 12) has a low dielectric constant ε r (4-6) and has certain application value in the field of millimeter wave communication, but its other performances, such as quality factor Qf (23,000-40,000 GHz), are low, which leads to a relatively limited application range. The existing research results show that the factors affecting the microwave dielectric performance of dielectric ceramics include internal factors and external factors, wherein the external factors include material manufacturing process, raw material type, grain boundary, second phase, porosity and low density; the internal factors include non-harmonic lattice vibration, composition order / disorder and symmetry. Due to the many influencing factors, it is difficult to find new cordierite combinations, and the high performance characteristics cannot be fully embodied.

[0003] Silicate-based microwave dielectrics exhibit ε r <10 due to the covalent effect of [SiO4] tetrahedron, which is 50% higher than that of Al2O3, but the material density is not conducive to achieving high quality factor, and a sintering temperature higher than 1500℃ is required to a certain extent to achieve better performance. Cordierite ceramics also have the disadvantage of low quality factor of the above-mentioned silicate-based microwave dielectrics, in addition, there are additional challenges, such as large negative resonance frequency temperature coefficient, polymorphism complexity (high-symmetry hexagonal phase α-cordierite and low-symmetry orthorhombic phase β-cordierite), composition order / disorder, and non-harmonic lattice vibration and secondary phase evolution caused by dopants, which hinder the commercial development of cordierite ceramics in the field of millimeter wave technology.

[0004] In the prior art, the microwave dielectric performance is improved by increasing the material density and adding a sintering aid. The increase of the material density will produce low dielectric loss (tan δ) and high Qf value (1 / tan δ). Therefore, in the prior art, the method of increasing the material density is also used to improve the microwave dielectric performance, but the sintering temperature required in the preparation process of high-density materials is very high, which will cause structural deformation due to stress, defects, etc. in the preparation process, thereby reducing the quality factor. In order to reduce the sintering temperature and improve the density, people have been seeking to add a sintering aid, but almost all sintering aids have a negative impact on the Qf value of the prepared dielectric ceramic material. For example, BaCu(B2O3) as a sintering aid added to Mg2Al4Si5O 18 12) can reduce the sintering temperature to 900℃, but its Qf value is only about 21,000 GHz.

[0005] The prior art also improves the microwave dielectric properties by selecting materials with high Qf values. A composite material of Mg2Al4Si5O r + 50wt% Mg2SiO4 is prepared using 50wt% Mg2SiO4 with high Qf value (ε 18 = 6.8, Qf = 270,000 GHz and TCF = -67ppm / ℃) as a microwave dielectric medium, and the sintering temperature is reduced from 1460℃ to 1340℃, and the Qf value is increased to 76,374 GHz, but the value is still low, and the quality factor (Qf value) and the resonance frequency temperature coefficient (TCF value) are not greatly improved.

[0006] Therefore, the above-mentioned methods have not been able to greatly improve the quality factor of the cordierite ceramic dielectric properties, and further development methods are needed to optimize the microwave dielectric properties. SUMMARY

[0007] The present application aims to solve the problems of small Qf value and small negative TCF value in the microwave dielectric properties of cordierite ceramic in the prior art, and proposes a dielectric ceramic material and a preparation method. In the present application, germanium element is used to partially replace silicon element in traditional cordierite, and titanium oxide suspension and / or titanium oxide powder are added, which greatly improves the quality factor and the resonance frequency temperature coefficient of the microwave dielectric properties of the dielectric ceramic material, and can be more widely applied to the field of millimeter wave communication.

[0008] To achieve the above technical purpose, the present application provides a preparation method of a dielectric ceramic material, comprising the following steps:

[0009] S1, preparing Mg2Al4(Si 1-x Ge x )5O 18 powder; wherein 0 < x ≤ 0.5;

[0010] S2, preparing a titanium oxide-containing suspension; adding the titanium oxide-containing suspension and / or titanium oxide powder to the powder prepared in S1, and sintering to obtain the dielectric ceramic material.

[0011] The x is 0.1-0.3; and / or, the titanium oxide is selected from at least one of titanium monoxide, titanium dioxide or titanium sesquioxide; and / or, the mass percentage concentration of titanium oxide in the titanium oxide-containing suspension is 3-7wt%; and / or, the mass ratio of the powder prepared in S1 to the volume of the titanium oxide-containing suspension is 1-3g:0-1mL.

[0012] The mass percentage of the titanium oxide powder in the powder prepared in S1 is 0-5wt%; preferably 2.0-4.0wt%.

[0013] In the S1 step, the preparation method of the powder comprises dispersing a magnesium source, an aluminum source, a silicon source and a germanium source in a solvent, grinding, drying and calcining to obtain the powder.

[0014] The magnesium source is selected from at least one of MgO, Mg(OH)2 and MgSO4; and / or, the aluminum source is selected from at least one of Al2O3, Al(OH)3 and Al2(SO4)3; and / or, the silicon source is selected from at least one of SiO2, SiO3 and H2SiO3; and / or, the germanium source is selected from at least one of GeO2, GeCl4 and GeO3; and / or, the molar ratio of the metal elements Mg, Al, Si and Ge in the magnesium source, the aluminum source, the silicon source and the germanium source is 2:4:3.5-4.5:0.5-1.5; and / or, the solvent is ethanol or water; and / or, the mass ratio of the total mass of the magnesium source, the aluminum source, the silicon source and the germanium source to the volume of the solvent is 1g:4-5mL.

[0015] In the S1 step, the drying temperature is 90-100℃, and the time is 23-26h; and / or, the calcining atmosphere is air, the temperature is 1250-1350℃, and the time is 2-8h; and / or, the calcined product is further sieved by a sieve with a mesh size of 80-120 meshes.

[0016] The grinding method is ball milling, and the rotation speed of the ball milling is 250-270rpm / min, and the time is 22-26h.

[0017] In the S2 step, the preparation method of the suspension containing the titanium oxide comprises dispersing the titanium oxide in a solvent; preferably, the solvent is selected from one or more of deionized water and ethanol.

[0018] In the S2 step, the sintering temperature is 1300-1380℃; preferably, the sintering temperature is 1325-1350℃.

[0019] In the S2 step, the sintering further comprises the steps of grinding, sieving, tabletting and sealing preservation; preferably, the sieving is performed by using a sieve with a mesh size of 80-120 meshes; preferably, the tabletting pressure is 100-180MPa; preferably, the sealing preservation time is 20-28h; and preferably, the sintering time is 2-6h.

[0020] The sintering further comprises the steps of polishing and / or annealing; preferably, the annealing temperature is 1150-1250℃, and the time is 9-12h.

[0021] The application further provides a dielectric ceramic material.

[0022] The technical scheme of the application has the following beneficial effects:

[0023] (1) The application provides a preparation method of a dielectric ceramic material, which comprises the following steps: S1, preparing Mg2Al4(Si 1-x Ge x )5O 18 powder; wherein 0 < x < 0.5; S2, preparing a titanium oxide-containing suspension; and adding the titanium oxide-containing suspension and / or titanium oxide powder into the powder prepared in the step S1, and sintering to obtain the dielectric ceramic material. In the method, the germanium element is used to partially replace the silicon element in the traditional cordierite, and the titanium oxide-containing suspension and / or titanium oxide powder is added, so that the high Qf value and the near zero TCF value are greatly achieved. The germanium element is closest to the silicon element, and the ion radius IR of the germanium element is 4.25 g / cm ε r , the melting point is 1115 ℃, and the density is 4.25 g / cm 3 . The above properties are far more than those of other elements with the same valence, so that the partial replacement of the germanium element enables the main phase to be synthesized at a lower temperature, greatly improves the quality factor and the resonance frequency temperature coefficient, and provides the low-temperature sintering condition for the addition of the titanium oxide. The addition of the titanium oxide-containing suspension and / or titanium oxide powder further improves the Qf value and the TCF value on the basis of the replacement of the germanium element, while the low ε r value is maintained. Therefore, the method of the application greatly improves the Qf value and the TCF value through the partial replacement of the germanium element and the addition of the titanium oxide-containing suspension and / or titanium oxide powder, so that the microwave dielectric properties of the dielectric ceramic material are improved, and the application is superior to the traditional cordierite material and any previous research.

[0024] (2) The application provides a preparation method of a dielectric ceramic material, wherein the mass percentage of the titanium oxide powder to the ceramic powder prepared in the step S1 is limited to 0-5 wt%, preferably 2.0-4.0%, so that the Qf value and the TCF value are improved.

[0025] (3) The application provides a preparation method of a dielectric ceramic material, wherein the sintering temperature in the step S2 is 1300-1380 ℃, preferably 1325-1350 ℃, so that the Qf value and the TCF value are further improved.

[0026] (4) The application provides a preparation method of a dielectric ceramic material, wherein the dielectric ceramic material is prepared by sintering in the step S2; preferably, the dielectric ceramic material is prepared by sintering and then annealing, so that the Qf value and / or the TCF value are further improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to illustrate the technical solutions in the specific embodiments or the prior art of the present application more clearly, a brief introduction will be given to the drawings needed in the specific embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0028] Figure 1 is the preparation flow chart of embodiment 1 of the present application. DETAILED DESCRIPTION

[0029] The following examples are provided to better further understand the present application and are not limited to the best mode, and do not constitute limitations on the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the present application with other prior art features falls within the protection scope of the present application.

[0030] The specific experimental steps or conditions not mentioned in the examples can be performed according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by purchase.

[0031] Examples 1-10

[0032] Examples 1-10 provide a series of preparation methods of dielectric ceramic materials, which involve the molar ratio of Mg, Al, Si and Ge, the calcination temperature (℃, S1 step), the amount of TiO2 powder (Wt%, mass percentage of the mass of the powder prepared in S1 step), and the sintering temperature (℃, S2 step) in the preparation process. The dielectric ceramic materials of each example are prepared according to the following steps:

[0033] S1, according to the molar ratio of metal elements Mg, Al, Si and Ge shown in Table 1, Mg(OH)2(≥99%), Al2O3(≥99.99%), SiO2(≥99.99%) and GeO2(≥99.9%) were weighed and placed in a 500 mL ball mill jar, and ethanol was added, wherein the total mass of Mg(OH)2, Al2O3, SiO2 and GeO2 to the volume of ethanol was 1:5 (g / mL). After ball milling at 260 rpm / min for 24 h, a slurry was obtained. The slurry was dried at 100℃ for 24 h, then calcined at the calcination temperature shown in Table 1 for 4 h in an air atmosphere, then placed in a ball mill jar, and the above-mentioned addition of ethanol, ball milling and drying steps were repeated once, and then sieved with a 100 mesh sieve to obtain a powder.

[0034] S2, 2g of TiO2was weighed and dispersed in 40ml of water at 25°C to obtain a suspension, 1g of the powder prepared in step S1 was added dropwise to 0.5ml (4-5 drops) of the suspension, TiO2powder was then added, followed by manual grinding and sieving through a 100 mesh sieve, and then a cylindrical sheet was prepared under a pressure of 150MPa, sealed and stored for 24h, then sintered at the sintering temperature in Table 1 for 4h, polished to obtain a dielectric ceramic material.

[0035] The preparation process is shown in Figure 1 . The powder prepared in step S1 in Examples 1-10 is Mg2Al4(Si 1-x Ge x )5O 18 , x=0.2. 0wt% TiO2in Example 1 means that only 4-5 drops of the titanium oxide suspension were used as a starting point, without additional TiO2powder. In addition, 4-5 drops of the titanium oxide suspension were used in Examples 2-10, and additional TiO2powder was added.

[0036] Table 1 Preparation conditions for the preparation of dielectric ceramic materials

[0037]

[0038] Examples 11-20

[0039] Examples 11-20 provide a series of dielectric ceramic materials, and the molar ratio of Mg, Al, Si and Ge involved in the preparation process of Examples 11-20, the calcination temperature (℃, step S1), the amount of TiO2powder (wt%, the mass percentage of the mass of the powder prepared in step S1), and the sintering temperature (℃, step S2) correspond to Examples 1-10 in turn. The difference between Examples 1-10 and Examples 11-20 is that Examples 11-20 have an annealing step of sintering at 1200°C for 10h after polishing in step S2, and the rest of the preparation method is the same as that of Examples 1-10.

[0040] Comparative Example 1

[0041] The comparative example provides a dielectric ceramic material, the molar ratio of Mg, Al and Si involved in the preparation process, the calcination temperature (℃, S1 step) is shown in Table 2 below. The difference from Examples 1-10 is that the powder prepared in S1 step is placed in a mortar, 5wt% polyvinyl alcohol solution (PVA solution) is added, the amount of each 1 gram of powder is 0.2mL (a total of 2 drops), grinding, then under the pressure of 100MPa, a cylindrical sheet with a diameter of 12mm and a thickness of 6mm is prepared, then sintering at 600℃ for 4 hours (debinding stage), continue to sinter at 1450℃ for 4 hours (densification stage), polishing, prepared; no GeO2 is weighed and added in S1 step and no S2 step is performed, and the rest of the preparation method is the same as that of Examples 1-10.

[0042] Table 2 Preparation conditions of dielectric ceramic material preparation process

[0043] Sample Molar ratio of Mg, Al and Si Calcination temperature (°C, S1 step) Comparative Example 1 2:4:5 1350

[0044] Comparative Example 2

[0045] The comparative example provides a dielectric ceramic material, the molar ratio of Mg, Al, Si and Ge involved in the preparation process, the calcination temperature (℃, S1 step) is shown in Table 3 below. The difference from Examples 1-10 is that the powder prepared in S1 step is placed in a mortar, 5wt% polyvinyl alcohol solution (PVA solution) is added, the amount of each 1 gram of powder is 0.2mL (a total of 2 drops), grinding, then under the pressure of 100MPa, a cylindrical sheet with a diameter of 12mm and a thickness of 6mm is prepared, then sintering at 600℃ for 4 hours (debinding stage), continue to sinter at 1365℃ for 4 hours (densification stage), polishing, prepared; no S2 step is performed, and the rest of the preparation method is the same as that of Examples 1-10.

[0046] Table 3 Preparation conditions of dielectric ceramic material preparation process

[0047] Sample Molar ratio of Mg, Al, Si and Ge Calcination temperature (°C, S1 step) Comparative Example 1 2:4:4:1 1275

[0048] Experimental Example 1

[0049] The dielectric ceramic materials prepared in the examples and comparative examples are tested for performance, using a Keysight E5080B network analyzer, the dielectric constant εr, quality factor Qf and temperature stability coefficient are measured by the Hakki-Coleman dielectric resonance method in TE mode. 011 r The temperature stability coefficient calculation formula is as follows:

[0050]

[0051] ​wherein f1 and f2 are the resonance frequencies at 25℃ (T1) and 85℃ (T2), respectively.

[0052] The results are shown in Table 4 below.

[0053] Table 4 Performance test results

[0054] Sample Annealing temperature / °C - 10 h e r ]] Qf (GHz) TCF (ppm / °C) Example 1 - 4.99 127,326 -27.21 Example 2 - 5.21 123,982 -15.03 Example 3 - 5.46 106,416 -5.45 Example 4 - 5.33 109,427 -4.89 Example 5 - 5.15 105,655 -8.34 Example 6 - 5.54 99,341 -3.05 Example 7 - 5.44 101,862 +3.12 Example 8 - 5.42 91,406 +7.01 Example 9 - 5.55 88,687 -9.98 Example 10 - 5.58 83,169 -3.37 Example 11 1200 4.95 149,886 -26.12 Example 12 1200 5.14 145,096 -19.35 Example 13 1200 5.37 128,683 -11.92 Example 14 1200 5.27 125,050 -9.65 Example 15 1200 5.10 123,440 -11.43 Example 16 1200 5.50 116,319 -7.09 Example 17 1200 5.37 108,317 -2.06 Example 18 1200 5.35 106,912 +1.99 Example 19 1200 5.51 106,649 -11.06 Example 20 1200 5.53 110,894 -5.43 Comparative Example 1 - 4.72 43,474 -32.20 Comparative Example 2 - 4.44 61,369 -21.32

[0055] From Table 4, it can be seen that the microwave dielectric properties of the dielectric ceramic materials of Examples 1-20 are all better than those of Comparative Example 1, not only the Qf value is greatly improved, but also the TCF value is improved.

[0056] Comparative Example 2 increases the substitution of germanium element compared with Comparative Example 1, and the microwave dielectric properties of the dielectric ceramic material are improved compared with Comparative Example 1, but the Qf value of Comparative Example 2 is still low and needs to be further improved. Compared with Comparative Example 2, Example 1 adds titanium oxide-containing suspension on the basis of Comparative Example 2, and the microwave dielectric properties of the dielectric ceramic material are improved. Compared with Example 1, Examples 2-10 add titanium oxide powder on the basis of Example 1, and the TCF value of the microwave dielectric properties of the dielectric ceramic material is greatly improved. Especially, the Qf value of the dielectric ceramic materials of Examples 2-5 and 7 is more than 10000 GHz, and the TCF value is obviously higher than that of Example 1, which shows that the method of substituting part of germanium element, adding titanium oxide-containing suspension and / or titanium oxide powder in the present application can greatly improve the microwave dielectric properties of the dielectric ceramic material.

[0057] Compared with Examples 1-10, Examples 11-20 perform the step of annealing after sintering, wherein the Qf value of Examples 11-20 is greatly improved, and the TCF value of Examples 11, 17-18 is greatly improved.

[0058] The influence of the amount of titanium oxide powder is compared in Examples 1-10, and the microwave dielectric properties of the dielectric ceramic materials of Examples 2-8 are better, so the mass percentage of the titanium oxide powder to the powder prepared in Step S1 is preferably 2.0-4.0wt%.

[0059] The influence of the sintering temperature is compared in Examples 1-10, and the microwave dielectric properties of the dielectric ceramic materials of Examples 2-4, Examples 6-8 and Example 10 are better, so the sintering temperature is preferably 1325-1350℃.

[0060] The present application realizes a cordierite-based material suitable for millimeter wave application based on the component-treatment-structure-property relationship strategy.

[0061] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A method for producing a dielectric ceramic material, characterized by, The method comprises the following steps: S1, preparing Mg2Al4(Si 1-x Ge x )5O 18 powder; wherein 0 < x < 0.5; S2, preparing a suspension of titanium-containing oxide; adding the suspension of titanium-containing oxide and titanium oxide powder into the powder prepared in S1, and preparing a dielectric ceramic material after sintering; In S2, the step of annealing after sintering is further included; the temperature of the annealing is 1150-1250℃, and the time is 9-12h; The mass percentage concentration of titanium oxide in the suspension of titanium-containing oxide is 3-7wt%; the mass of the powder prepared in S1 to the volume of the suspension of titanium-containing oxide is 1-3g:0-1mL, and the volume of the suspension of titanium-containing oxide is not 0; The mass percentage of the mass of the titanium oxide powder to the mass of the powder prepared in S1 is 0-5wt%, and is not 0.

2. The method of producing a dielectric ceramic material according to claim 1, characterized by, The x is 0.1-0.3; and / or, the titanium oxide is selected from at least one of titanium monoxide, titanium dioxide or titanium sesquioxide.

3. The method of producing a dielectric ceramic material according to claim 1, characterized by, The mass percentage of the mass of the titanium oxide powder to the mass of the powder prepared in S1 is 2.0-4.0wt%.

4. The method of producing a dielectric ceramic material according to any one of claims 1 to 3, characterized by, In S1, the preparation method of the powder comprises dispersing a magnesium source, an aluminum source, a silicon source and a germanium source in a solvent, grinding, drying, calcining, and preparing a powder.

5. The method of producing a dielectric ceramic material according to claim 4, characterized by, The magnesium source is selected from at least one of MgO, Mg(OH)2 and MgSO4; and / or, the aluminum source is selected from at least one of Al2O3, Al(OH)3 and Al2(SO4)3; and / or, the silicon source is selected from at least one of SiO2 and H2SiO3; and / or, the germanium source is selected from at least one of GeO2 and GeCl4; and / or, the molar ratio of the metal elements Mg, Al, Si and Ge in the magnesium source, the aluminum source, the silicon source and the germanium source is 2:4:3.5-4.5:0.5-1.5; and / or, the solvent is ethanol or water; and / or, the ratio of the total mass of the magnesium source, the aluminum source, the silicon source and the germanium source to the volume of the solvent is 1g:4-5mL.

6. The method of producing a dielectric ceramic material according to claim 4, characterized by, In S1, the temperature of the drying is 90-100℃, and the time is 23-26h; and / or, the atmosphere of the calcining is air, the temperature is 1250-1350℃, and the time is 2-8h; and / or, the powder needs to be sieved by a sieve with a specification of 80-120mesh after the calcining.

7. The method of producing a dielectric ceramic material according to claim 1, characterized by, In S2, the temperature of the sintering is 1300-1380℃.

8. The method of producing a dielectric ceramic material according to claim 7, characterized by, In S2, the temperature of the sintering is 1325-1350℃.

9. The method of producing a dielectric ceramic material according to claim 1, characterized by, In S2, the steps of grinding, sieving, tabletting and sealing preservation are further included before the sintering.

10. The method of producing a dielectric ceramic material according to claim 9, characterized by, The sieving is performed by using a sieve with a specification of 80-120mesh.

11. The method of producing a dielectric ceramic material according to claim 10, characterized by, The pressure during the tabletting is 100-180MPa.

12. The method of producing a dielectric ceramic material according to claim 11, characterized by, The time of the sealing preservation is 20-28h.

13. The method of producing a dielectric ceramic material according to claim 12, characterized by, The time of the sintering is 2-6h.

14. The method of producing a dielectric ceramic material according to claim 1, characterized by, In S2, the step of polishing after the sintering is further included.

15. A dielectric ceramic material prepared by the preparation method of any one of claims 1-14.

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