A low-loss CaMgSiO4-based microwave dielectric ceramic material and its preparation method

Abstract

The present invention discloses a low-loss CaMgSiO4-based microwave dielectric ceramic material and a preparation method thereof. The microwave dielectric ceramic material is sintered from raw materials in the following parts by weight: 165-172 parts of black talc, 154-164 parts of wollastonite, 82-88 parts of MgO, 204-210 parts of CaCO3, 3-6 parts of LiF, and 2-4 parts of TiO2. The preparation method includes the following steps: crushing, grinding, and sieving black talc and wollastonite ore to obtain black talc and wollastonite ore powder; weighing LiF and TiO2, mixing and calcining them; weighing black talc, wollastonite, MgO, and CaCO3 powder according to the ratio, and wet ball-milling and mixing them; drying, calcining, heat-preserving, and furnace-cooling the powder after ball-milling; dry rolling and mixing the calcined powder and the composite modifier evenly; forming a blank and sintering it. The CaMgSiO4 ceramic material prepared by the present invention has ultra-low dielectric loss and a small temperature coefficient of resonant frequency.

Description

Technical Field

[0001] The present invention belongs to ceramic materials and their manufacturing methods, and particularly relates to a low-loss CaMgSiO4-based microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] Microwave dielectric ceramic materials are widely used in microwave devices such as resonators, filters, and dielectric antennas. With the increasing perfection of 5G communication technology, the demand for low-cost, high-frequency, and lightweight microwave devices in mobile, satellite communication, and wireless local area network (WLAN) is increasing day by day. This requires microwave dielectric ceramic materials to have low cost, low density, and excellent microwave dielectric properties (lower εr , to avoid signal delay; high Q×f , to ensure excellent frequency selection characteristics; near-zero τf , to ensure high thermal stability).

[0003] In recent years, with the rapid progress of microwave communication and radar technology, many applicable microwave ceramics generally have a relatively high εr ( εr >10) and Q×f , such as: Y2BaCu 0.4 Ni 0.6 O5, Mg4Nb2O9, LaBO3, Ba(Zn 1 / 3 Ta 2 / 3 )O3. However, the relatively high relative dielectric constant ( εr >10) of the above materials limits their application in microwave dielectric resonators. A high relative dielectric constant will increase the interaction coupling loss between them and the electrodes, thereby reducing the transmission rate of electrical signals. Researchers have found that CaMgSiO4-based microwave dielectric ceramic materials are a kind of low dielectric constant ceramic materials with great application potential. However, problems such as high dielectric loss and high temperature coefficient of resonant frequency limit their further application.

[0004] Therefore, how to further reduce the dielectric loss of the CaMgSiO4 ceramic system, effectively adjust the τ f value of the ceramic material, and reduce its sintering temperature has become a key technical problem to be solved urgently. Summary of the Invention

[0005] Object of the Invention: In order to overcome the deficiencies in the prior art, the object of the present invention is to provide a low-loss CaMgSiO4-based microwave dielectric ceramic material with an adjustable temperature coefficient of resonant frequency. Another object of the present invention is to provide a preparation method for a low-sintering temperature and low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0006] Technical solution: A low-loss CaMgSiO4-based microwave dielectric ceramic material of the present invention is sintered from the following raw materials in parts by weight: 165-172 parts of black talc, 154-164 parts of wollastonite, 82-88 parts of MgO, 204-210 parts of CaCO3, 3-6 parts of LiF, and 2-4 parts of TiO2.

[0007] Further, the main phase of the low-loss CaMgSiO4-based microwave dielectric ceramic material is CaMgSiO4.

[0008] Further, the relative dielectric constant of the low-loss CaMgSiO4-based microwave dielectric ceramic material is 7.85-8.39, the quality factor is 95537-116916 GHz, and the resonant frequency temperature coefficient is -26 to -30 ppm / °C.

[0009] The preparation method of the above low-loss CaMgSiO4-based microwave dielectric ceramic material includes the following steps:

[0010] Step S1: Crush, grind and screen black talc and wollastonite ores respectively to obtain black talc and wollastonite ore powders;

[0011] Step S2: Weigh LiF and TiO2 powders in proportion, grind and mix them, and then calcine;

[0012] Step S3: Weigh black talc ore powder, wollastonite ore powder, MgO, and CaCO3 in proportion, and wet ball mill and mix them;

[0013] Step S4: Dry, calcine, keep warm, and cool with the furnace the product obtained in Step S3;

[0014] Step S5: Add the product obtained in Step S2 to the product obtained in Step S4, and dry roll mill and mix them;

[0015] Step S6: Take out the powder obtained in Step S5, prepare a blank from the powder and sinter it to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0016] Further, in Step S1, the particle sizes of the crushed, ground and screened black talc and wollastonite are 38-75 μm.

[0017] Further, in Step S2, both the LiF and TiO2 powders are of analytical purity, the grinding time is 15-30 min, the calcination temperature is 550-700 °C, and the heat preservation time is 2-4 h.

[0018] Further, in Step S3, both the MgO and CaCO3 powders are of analytical purity, the ball milling is wet ball milling, the ball milling speed is 200-250 r / min, and the ball milling time is 8-12 h. Wet ball milling makes the material easier to grind, improves the grinding efficiency, and the material uniformity is better.

[0019] Further, in step S4, the calcination temperature is 900 - 1000 °C, and the heat preservation time is 2 - 4 h. If the calcination temperature is lower than 900 °C, the raw material phase is contained in the powder, and impurity phases are likely to appear during the subsequent sintering process; if the calcination temperature is higher than 1000 °C, the particle size of the powder becomes larger, and the reaction activity becomes poor during the subsequent sintering process.

[0020] Further, in step S5, the ball milling is dry rolling milling, the ball milling speed is 180 - 220 r / min, and the ball milling time is 16 - 24 h. Dry rolling milling can prevent the separation of the main material and the composite modifier in the aqueous grinding medium, so that the composite modifier can be evenly dispersed in the main material.

[0021] Further, in step S6, the sintering temperature is 1100 - 1200 °C, heat preservation is carried out for 4 - 6 h after sintering, and then it is cooled with the furnace. If the sintering temperature is lower than 1000 °C, the sintering driving force of the ceramic material is insufficient, the densification degree decreases, and the performance deteriorates; if the sintering temperature is higher than 1200 °C, the ceramic grains grow abnormally, and the grains are coated during the grain growth process, resulting in an increase in the porosity, a decrease in the densification degree, and a deterioration in the performance.

[0022] Preparation principle: Introduce MgO and CaCO3 raw materials into wollastonite and black talc ores, making up for the deficiency of Mg and Ca in the mineral material composition, thereby ensuring that the main crystal phase of the final ceramic product is CaMgSiO4, and further significantly reducing the dielectric loss of the material. LiF and TiO2 powders are pre-synthesized into a Li-Ti binary phase through high-temperature calcination, so that the composite modifier contains TiO2 and the Li-Ti binary phase, which not only reduces the sintering temperature of the material, but also improves the resonance frequency temperature coefficient τ of the ceramic material. f 。

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0024] 1. Using wollastonite and black talc ores as the main raw materials, a low-cost CaMgSiO4-based microwave dielectric ceramic material is prepared;

[0025] 2. Selecting a composite modifier of LiF and TiO2, and through the preparation method of pre-synthesizing a Li-Ti binary phase, without reducing the quality factor (Q×f) of the ceramic material, the sintering temperature of the material is reduced while the resonance frequency temperature coefficient of the material is improved;

[0026] 3. It has ultra-low dielectric loss and a small resonance frequency temperature coefficient, and the proportion of mineral raw materials used exceeds half, providing a low-cost solution for microwave devices and materials for millimeter-wave communication. Description of the Drawings

[0027] Figure 1XRD pattern of the low-loss CaMgSiO4-based microwave dielectric ceramic material prepared in Example 2 of the present invention.

[0028] Figure 2 SEM image of the low-loss CaMgSiO4-based microwave dielectric ceramic material prepared in Example 2 of the present invention.

[0029] Figure 3 SEM image of the low-loss CaMgSiO4-based microwave dielectric ceramic material prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0030] In the following examples, materials, reagents, instruments, etc. used, unless otherwise specified, can be obtained from commercial sources. The experimental methods without specific conditions noted in the examples are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. The specific compositions of the black talc ore powder and wollastonite ore are shown in Table 1 below.

[0031] Table 1 Elemental compositions of black talc ore powder and wollastonite ore (%)

[0032]

[0033] Example 1

[0034] A preparation method of a low-loss CaMgSiO4-based microwave dielectric ceramic material, comprising the following steps:

[0035] Step S1: Crush, grind and sieve black talc and wollastonite ore respectively to make the average particle size of the black talc and wollastonite ore powder 45 μm.

[0036] Step S2: Weigh 0.3 g of LiF powder and 0.3 g of TiO2 powder, manually grind and mix the two weighed powders for 15 min, place the mixed powder in a muffle furnace, calcine at 550 °C and keep warm for 2 h, and cool with the furnace.

[0037] Step S3: Weigh 16.5 g of black talc ore powder, 15.4 g of wollastonite ore powder, 8.2 g of MgO powder, and 20.4 g of CaCO3 powder, wet ball mill at a rotation speed of 200 r / min for 8 h, and dry.

[0038] Step S4: Place the product obtained in Step S3 in a muffle furnace, calcine at 900 °C and keep warm for 2 h, and cool with the furnace.

[0039] Step S5: Mix the powders calcined in Step S2 and Step S4 and dry roll mill at a rotation speed of 180 r / min for 16 h.

[0040] Step S6: Take out the powder obtained in Step S5, press it into a green body, and place it in a high-temperature muffle furnace for sintering. The sintering temperature is 1150 °C, the holding time is 4 h, and then it is cooled with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0041] Example 2

[0042] A preparation method of a low-loss CaMgSiO4-based microwave dielectric ceramic material, comprising the following steps:

[0043] Step S1: Crush, grind and screen the black talc and wollastonite ore respectively to make the average particle size of the black talc and wollastonite ore powder 45 μm.

[0044] Step S2: Weigh 0.6 g of LiF powder and 0.3 g of TiO2 powder, manually grind and mix the two weighed powders for 20 min, place the mixed powder in a muffle furnace for calcination at 600 °C and hold for 2 h, and then cool with the furnace.

[0045] Step S3: Weigh 16.9 g of black talc ore powder, 15.8 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.8 g of CaCO3 powder, wet ball mill at a speed of 225 r / min for 9 h, and dry.

[0046] Step S4: Place the product obtained in Step S3 in a muffle furnace for calcination at 950 °C and hold for 4 h, and then cool with the furnace.

[0047] Step S5: Mix the powders calcined in Step S2 and Step S4 and dry roll mill at a speed of 190 r / min for 18 h.

[0048] Step S6: Take out the powder obtained in Step S5, press it into a green body, and place it in a high-temperature muffle furnace for sintering. The sintering temperature is 1100 °C, the holding time is 6 h, and then it is cooled with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0049] Example 3

[0050] A preparation method of a low-loss CaMgSiO4-based microwave dielectric ceramic material, comprising the following steps:

[0051] Step S1: Crush, grind and screen the black talc and wollastonite ore respectively to make the average particle size of the black talc and wollastonite ore powder 45 μm.

[0052] Step S2: Weigh 0.5 g of LiF powder and 0.4 g of TiO2 powder, manually grind and mix the two weighed powders for 25 min, place the mixed powder in a muffle furnace for calcination at 650 °C and hold for 4 h, and then cool with the furnace.

[0053] Step S3: Weigh 17.2 g of black talc ore powder, 16.2 g of wollastonite ore powder, 8.8 g of MgO powder, and 20.6 g of CaCO3 powder. Wet ball mill at a rotation speed of 250 r / min for 10 h, and then dry.

[0054] Step S4: Place the product obtained in Step S3 into a muffle furnace, calcine at 1000 °C and hold for 3 h, and then cool with the furnace.

[0055] Step S5: Mix the powders calcined in Step S2 and Step S4 and dry roll mill at a rotation speed of 200 r / min for 20 h.

[0056] Step S6: Take out the powder obtained in Step S5, press it into a blank, place it in a high-temperature muffle furnace for sintering, the sintering temperature is 1200 °C, the holding time is 5 h, and then cool with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0057] Example 4

[0058] A preparation method of a low-loss CaMgSiO4-based microwave dielectric ceramic material, comprising the following steps:

[0059] Step S1: Crush and grind the black talc and wollastonite ores respectively and sieve them so that the average particle size of the black talc and wollastonite ore powders is 45 μm.

[0060] Step S2: Weigh 0.4 g of LiF powder and 0.2 g of TiO2 powder. Manually grind and mix the two weighed powders for 30 min. Place the mixed powder in a muffle furnace, calcine at 700 °C and hold for 3 h, and then cool with the furnace.

[0061] Step S3: Weigh 17.0 g of black talc ore powder, 16.4 g of wollastonite ore powder, 8.4 g of MgO powder, and 21.0 g of CaCO3 powder. Wet ball mill at a rotation speed of 225 r / min for 11 h, and then dry.

[0062] Step S4: Place the product obtained in Step S3 into a muffle furnace, calcine at 950 °C and hold for 4 h, and then cool with the furnace.

[0063] Step S5: Mix the powders calcined in Step S2 and Step S4 and dry roll mill at a rotation speed of 210 r / min for 22 h.

[0064] Step S6: Take out the powder obtained in Step S5, press it into a blank, place it in a high-temperature muffle furnace for sintering, the sintering temperature is 1100 °C, the holding time is 5 h, and then cool with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0065] Example 5

[0066] A preparation method of a low-loss CaMgSiO4-based microwave dielectric ceramic material, comprising the following steps:

[0067] Step S1: Crush, grind and screen black talc and wollastonite ore respectively to make the average particle size of black talc and wollastonite ore powder 45 μm.

[0068] Step S2: Weigh 0.6 g of LiF powder and 0.4 g of TiO2 powder, manually grind and mix the two weighed powders for 20 min, place the mixed powder in a muffle furnace, calcine at 600 °C and hold for 4 h, and cool with the furnace.

[0069] Step S3: Weigh 16.7 g of black talc ore powder, 15.6 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.6 g of CaCO3 powder, wet ball mill at a speed of 200 r / min for 12 h, and dry.

[0070] Step S4: Place the product obtained in Step S3 in a muffle furnace, calcine at 900 °C and hold for 3 h, and cool with the furnace.

[0071] Step S5: Mix the powders calcined in Step S2 and Step S4 and dry roll mill at a speed of 220 r / min for 24 h.

[0072] Step S6: Take out the powder obtained in Step S5, press it into a blank and place it in a high-temperature muffle furnace for sintering. The sintering temperature is 1150 °C, the holding time is 4 h, and then cool with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0073] Comparative Example 1

[0074] Crush, grind and screen black talc and wollastonite ore respectively to make the average particle size of black talc and wollastonite ore powder 45 μm. Take 16.9 g of black talc ore powder, 15.8 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.8 g of CaCO3 powder, wet ball mill at a speed of 225 r / min for 9 h, place the dried powder in a muffle furnace, calcine at 950 °C and hold for 4 h, and cool with the furnace. The calcined powder is dry roll milled at a speed of 190 r / min for 18 h, the roll milled powder is pressed into a blank and placed in a high-temperature muffle furnace for sintering. The sintering temperature is 1400 °C, the holding time is 6 h, and then cool with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0075] Comparative Example 2

[0076] The black talc and wollastonite ore are respectively crushed, ground and sieved to make the average particle size of the black talc and wollastonite ore powder 45 μm. Take 16.9 g of black talc ore powder, 15.8 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.8 g of CaCO3 powder, and wet ball mill at a speed of 225 r / min for 9 h. After drying, the powder is placed in a muffle furnace for calcination at 950 °C and held for 4 h, and then cooled with the furnace. Add 0.6 g of LiF powder to the calcined powder, and dry roll mill at a speed of 190 r / min for 18 h. The rolled powder is compacted and placed in a high-temperature muffle furnace for sintering. The sintering temperature is 1350 °C, and the holding time is 6 h, and then cooled with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0077] Comparative Example 3

[0078] The black talc and wollastonite ore are respectively crushed, ground and sieved to make the average particle size of the black talc and wollastonite ore powder 45 μm. Take 16.9 g of black talc ore powder, 15.8 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.8 g of CaCO3 powder, and wet ball mill at a speed of 225 r / min for 9 h. After drying, the powder is placed in a muffle furnace for calcination at 950 °C and held for 4 h, and then cooled with the furnace. Add 0.3 g of TiO2 powder to the calcined powder, and dry roll mill at a speed of 190 r / min for 18 h. The rolled powder is compacted and placed in a high-temperature muffle furnace for sintering. The sintering temperature is 1450 °C, and the holding time is 6 h, and then cooled with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0079] Comparative Example 4

[0080] The black talc and wollastonite ore are respectively crushed, ground and sieved to make the average particle size of the black talc and wollastonite ore powder 45 μm. Take 16.9 g of black talc ore powder, 15.8 g of wollastonite ore powder, 8.6 g of MgO powder, and 20.8 g of CaCO3 powder, and wet ball mill at a speed of 225 r / min for 9 h. After drying, the powder is placed in a muffle furnace for calcination at 950 °C and held for 4 h, and then cooled with the furnace. Add 0.6 g of LiF and 0.3 g of TiO2 powder to the calcined powder, and dry roll mill at a speed of 190 r / min for 18 h. The rolled powder is compacted and placed in a high-temperature muffle furnace for sintering. The sintering temperature is 1300 °C, and the holding time is 6 h, and then cooled with the furnace to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material.

[0081] Table 2 Properties of the materials obtained in each example and comparative example

[0082]

[0083] Table 2 shows the microwave dielectric properties and sintering properties of low-loss CaMgSiO4-based ceramic materials under different formulations and process conditions in Examples 1 to 5. Among them, the ceramic sample prepared in Example 2 has the lowest relative dielectric constant, the highest quality factor, the smallest absolute value of the resonant frequency temperature coefficient, and the lowest sintering temperature, which is the optimal example. Figure 1 As shown, the main phase is CaMgSiO4. Compared with Example 2, Comparative Example 1 prepared a ceramic sample without adding LiF and TiO2. Figure 2 (Example 2) and Figure 3 As shown in (Comparative Example 1), the ceramic material prepared in Comparative Example 1 has poor density and more pores, so the dielectric properties and sintering properties are poor. In Comparative Example 2, a ceramic sample without adding TiO2 was prepared, and the resonant frequency temperature coefficient was not improved. In Comparative Example 3, a ceramic sample without adding LiF was prepared, and the sintering performance was relatively poor. Although two modifiers, LiF and TiO2, were added in Comparative Example 4, the Li-Ti binary phase was not pre-synthesized by high-temperature calcination. Therefore, compared with Example 2, the dielectric properties and sintering properties are generally low.

Claims

1. A method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material, characterized in that: The following steps are involved: Step S1, crushing black talc and wollastonite respectively, grinding and sieving to obtain black talc ore powder and wollastonite ore powder; Step S2, weighing LiF and TiO2 powders in proportion, grinding and mixing, and then calcining; Step S3, weighing black talc powder, wollastonite powder, MgO and CaCO3 in proportion, and mixing by wet ball milling; Step S4, drying, calcining, heat preservation, and cooling with the furnace; Step S5, adding the product obtained in step S2 to the product obtained in step S4, and dry rolling and mixing; Step S6, taking out the powder obtained in step S5, preparing a blank from the powder and then sintering it to obtain a low-loss CaMgSiO4-based microwave dielectric ceramic material; The low-loss CaMgSiO4-based microwave dielectric ceramic material is prepared by sintering the following raw materials in parts by weight: 165-172 parts of black talc, 154-164 parts of wollastonite, 82-88 parts of MgO, 204-210 parts of CaCO3, 3-6 parts of LiF, and 2-4 parts of TiO2.

2. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: Its main phase is CaMgSiO4.

3. The method for preparing the low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: The low-loss CaMgSiO4-based microwave dielectric ceramic material has a relative dielectric constant of 7.85 to 8.39, a quality factor of 95537 to 116916 GHz, and a resonant frequency temperature coefficient of -26 to -30 ppm / °C.

4. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In the step S1, the particle size of the black talc and wollastonite after crushing, grinding and screening is 38-75 μm.

5. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In the step S2, LiF and TiO2 powders are both analytically pure, the grinding time is 15-30 min, the calcination temperature is 550-700° C., and the ball milling time is 2-4 h.

6. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In step S3, the MgO and CaCO3 powders are both analytically pure, the rotation speed of the wet ball mill is 200-250 r / min, and the wet ball milling time is 8-12 h.

7. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In step S4, the calcination temperature is 900-1000° C., and the holding time is 2-4 hours.

8. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In step S5, the rotation speed of dry rolling is 180-220 r / min, and the dry rolling time is 16-24 h.

9. The method for preparing a low-loss CaMgSiO4-based microwave dielectric ceramic material according to claim 1, characterized in that: In the step S6, the sintering temperature is 1100-1200° C., and the sintering temperature is kept for 4-6 hours, followed by cooling in the furnace.

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