Rapid densification microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a rapidly densified microwave dielectric ceramic material and a preparation method thereof.The principal crystalline phase of the microwave dielectric ceramic material is Ba2Zn3Si3O11, due to the fact that the composition of the microwave dielectric ceramic material is located near an eutectic line in a three-phase diagram, a liquid phase is generated more easily in the sintering process, and therefore the sintering process can be accelerated, and the performance of the microwave dielectric ceramic material is improved. The heat preservation time after glue discharging in the preparation process of the microwave dielectric ceramic material can be remarkably shortened, so that the technical problem that the microwave dielectric ceramic material needs relatively long sintering time to be densified in the prior art is solved, the batch production efficiency is improved, meanwhile, energy is saved, and environmental pollution is reduced.

Description

Technical Field

[0001] This invention belongs to the field of microwave dielectric ceramics technology, and more specifically, relates to a method for rapidly densifying microwave dielectric ceramic materials and its preparation. Background Technology

[0002] Microwave dielectric ceramics refer to ceramics used as dielectric materials in microwave frequency band (300 MHz ~ 300 GHz) circuits to perform one or more functions. They are key materials for electronic components such as resonators, filters, duplexers, dielectric substrates, dielectric waveguide transmission lines and antennas that are widely used in modern communications.

[0003] Low-temperature co-fired ceramics (LTCC) technology is a widely used passive electronic device integration technology that allows for the three-dimensional integration of different passive devices through layering. Traditional microwave dielectric ceramic production processes require holding the ceramic substrate at a temperature of 3 hours or even longer. Shortening the sintering time leads to a decrease in the density of the ceramic substrate, causing a severe deterioration in microwave dielectric properties. Current rapid sintering technologies (such as spark plasma sintering (SPS), microwave sintering (MWS), and ultrafast high-temperature sintering (UHS)) typically require expensive equipment, special sintering atmospheres and conditions, and long sintering times, making large-scale continuous production impossible. Therefore, there is an urgent need to develop a microwave dielectric ceramic substrate that can be densified in a short time using a traditional muffle furnace under atmospheric pressure, in line with the trend of green energy conservation and energy saving, and effectively suppressing the technical problem of silver electrode diffusion caused by excessively long sintering times in LTCC technology. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a rapid densification microwave dielectric ceramic material and its preparation method, thereby solving the technical problem that microwave dielectric ceramic materials require a long sintering time to densify in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a microwave dielectric ceramic material is provided, the microwave dielectric ceramic material comprising the main crystalline phase Ba2Zn3Si3O 11 .

[0006] Preferably, it further includes a sintering aid, wherein the mass percentage x of the sintering aid in the main crystalline phase satisfies: 0 < x ≤3%; the sintering aid is a mixture of Li2O, B2O3 and SiO2.

[0007] Preferably, in the sintering aid, the molar percentage of Li2O is 30-50%, the molar percentage of B2O3 is 30-55%, and the molar percentage of SiO2 is 5-20%.

[0008] Preferably, the microwave dielectric ceramic has a dielectric constant of 9 to 11, a quality factor of 7000 to 25000 GHz, and a resonant frequency temperature coefficient of -50 to -80 ppm / ℃.

[0009] According to another aspect of the present invention, a method for preparing the microwave dielectric ceramic material is provided, comprising the following steps: (1) Using BaCO3, ZnO and SiO2 as raw materials, according to the chemical formula Ba2Zn3Si3O 11 The molar ratio of Ba, Zn, and Si elements is determined by mixing the ingredients, followed by wet ball milling, drying, and sieving to obtain a powder with uniform particles. (2) After the powder in step (1) is pre-fired, it is wet ball milled, dried and sieved again, and then the binder is added to granulate and molded, and then dry pressed to obtain the green porcelain body. (3) The raw ceramic blank is sintered in a muffle furnace after debinding to obtain the microwave dielectric ceramic material.

[0010] Preferably, in step (2), a sintering aid is added after the powder is pre-calcined; the mass percentage x of the sintering aid in the main crystalline phase satisfies 0 < 0. x ≤ 3%, the sintering aid is a mixture of Li2O, B2O3 and SiO2.

[0011] Preferably, in step (2), the pre-firing temperature is 1080-1150 °C and the time is 3-5 h.

[0012] Preferably, in step (3), the adhesive discharge conditions are: heating to 450-600 ℃ at a heating rate of 3-10 ℃ / min and holding for 1-2 h to discharge the adhesive; Preferably, the sintering conditions are: heating to 1150℃ to 1300℃ at a heating rate of 5 to 10℃ / min, and sintering time of 1 to 30 min; Preferably, the sintering conditions are: heating to 800℃ to 900℃ at a heating rate of 5 to 10℃ / min, and sintering time of 1 to 30 min.

[0013] Preferably, the drying conditions in steps (1) and (2) are: drying temperature 70℃~100℃, drying time 8h~12h.

[0014] Preferably, the adhesive comprises 4% to 8% of the powder by mass, and more preferably 5%.

[0015] Preferably, the adhesive is selected from polyvinyl alcohol, paraffin, or polyvinyl butyral.

[0016] Preferably, in steps (1) and (2), the ball milling medium for wet ball milling is zirconium oxide, and the dispersant is deionized water; the mass ratio of the powder to be milled, the ball milling medium, and the dispersant is 1:(5-8):(1.5-3); and the wet ball milling time is 4-6 h.

[0017] According to another aspect of the present invention, a ceramic device is provided, wherein the ceramic device comprises, from top to bottom, an electrode material and the microwave dielectric ceramic material.

[0018] Preferably, the electrode material is selected from silver or a silver-palladium alloy.

[0019] According to another aspect of the invention, an application of the ceramic device is provided, in which the ceramic device is used as an antenna, filter, duplexer or dielectric substrate.

[0020] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: (1) The microwave dielectric ceramic material Ba2Zn3Si3O used in this invention 11 -LBS, which adopts the main crystal phase Ba2Zn3Si3O 11 Because its composition is located near the eutectic line in the BaO-ZnO-SiO2 three-phase diagram, it is easier to generate a liquid phase during sintering, which can accelerate the sintering process and significantly reduce the sintering time. By adding LBS sintering aid, the sintering temperature can be greatly reduced to 800~900 ℃, while still maintaining the rapid densification characteristics.

[0021] (2) The microwave dielectric ceramic material Ba2Zn3Si3O prepared by the present invention 11 - x LBS has a low dielectric constant of 9 to 11 and a low dielectric loss of 7000 to 25000 GHz, a resonant frequency temperature coefficient of -50 to -80 ppm / ℃, and also has the property of rapid densification.

[0022] (3) The microwave dielectric ceramic material Ba2Zn3Si3O used in this invention 11 This method can significantly shorten the heat preservation time after debinding during the preparation of microwave dielectric ceramic materials, allowing the sintering time to be controlled within 1 to 30 minutes to obtain highly dense microwave dielectric ceramics. This is beneficial for improving the efficiency of mass production, while saving energy and reducing environmental pollution. Attached Figure Description

[0023] Figure 1 Ba2Zn3Si3O prepared in Example 4 of this invention 11 Scanning electron microscope (SEM) image of microwave dielectric ceramics.

[0024] Figure 2 The images shown are scanning electron microscope (SEM) images and energy dispersive X-ray spectroscopy (EDS) images of the silver electrode after it was printed in Embodiment 15 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Example 1 This embodiment provides a method for preparing microwave dielectric ceramic materials, including the following steps: (1) Mix BaCO3, ZnO, and SiO2 according to the formula Ba2Zn3Si3O 11 The raw materials are mixed according to stoichiometric ratios to obtain a mixture. (2) The raw materials from step (1) were mixed with zirconia balls and deionized water at a mass ratio of 1:8:2 and then ball-milled in a planetary ball mill for 5 h. After that, the mixture was dried in an 80 ℃ forced-air drying oven for 12 h. The dried powder was then passed through a 40-mesh sieve and placed in a muffle furnace. The temperature was increased from room temperature to 1100 ℃ at a rate of 5 ℃ / min and held for 3 h. The temperature was then lowered to room temperature with the furnace to preliminarily synthesize Ba2Zn3Si3O. 11 .

[0027] (3) The powder from step (2) is ball-milled a second time. After mixing the powder, zirconium oxide balls and deionized water in a mass ratio of 1:8:2, the mixture is ball-milled for 6 hours. Then it is dried in an 80°C forced-air drying oven for 12 hours. After drying, the powder is sieved through a 40-mesh sieve and 5wt% of PVA binder is added for granulation. After sieving through an 80-mesh sieve again, it is pressed into ceramic green bodies with a diameter of 12 mm and a height of 5-6 mm using a mold under a pressure of 200 MPa.

[0028] (4) Place the blank from (3) in a muffle furnace, and under an air atmosphere, heat it to 550 °C at 5 °C / min to remove the binder for 1 hour, then heat it to 1160 °C to sinter for 15 minutes, and then cool it down to room temperature with the furnace to obtain the microwave dielectric ceramic material.

[0029] (5) The microwave dielectric properties of the cylindrical sample were tested using the parallel plate resonance method on a network analyzer. The dielectric constant ε of the microwave dielectric ceramic material was determined using a network analyzer at room temperature (25°C). r and quality factor Q×f After heating the microwave dielectric ceramic material from 25 °C to 75 °C using a heating device, the temperature coefficient of the resonant frequency was calculated using a network analyzer. τ f .

[0030] Example 2 The difference between Example 2 and Example 1 is that the sintering time in step (4) is 30 min.

[0031] Example 3 The difference between Example 3 and Example 1 is that the sintering temperature in step (4) is 1180℃.

[0032] Example 4 The difference between Example 4 and Example 1 is that the sintering time in step (4) is 1 min and the sintering temperature is 1200℃. Figure 1 This is a scanning electron microscope (SEM) image of the microwave dielectric ceramic of Example 4. The image shows a tightly packed grain structure with no obvious surface pores, indicating that Ba2Zn3Si3O... 11 It can be densified in a short time.

[0033] Example 5 The difference between Example 5 and Example 1 is that the sintering temperature in step (4) is 1200℃.

[0034] Example 6 The difference between Example 6 and Example 1 is that the sintering time in step (4) is 30 min, the sintering temperature is 1200℃, and the heating rate is 8°C / min.

[0035] Example 7 The difference between Example 7 and Example 1 is that the sintering time in step (4) is 30 min, the sintering temperature is 1200℃, and the heating rate is 10°C / min.

[0036] Example 8 The difference between Example 8 and Example 1 is that the sintering time in step (4) is 30 min and the sintering temperature is 1240℃.

[0037] Example 9 The difference between Example 9 and Example 1 is that the sintering time in step (4) is 30 min and the sintering temperature is 1260℃.

[0038] Example 10 The difference between Example 10 and Example 1 is that the sintering time in step (4) is 30 min and the sintering temperature is 1280℃.

[0039] Example 11 This embodiment provides a method for preparing microwave dielectric ceramic materials, including the following steps: (1) Mix BaCO3, ZnO, and SiO2 according to the formula Ba2Zn3Si3O 11 The raw materials are mixed according to stoichiometric ratios to obtain a mixture. (2) The raw materials from step (1) were mixed with zirconia balls and deionized water at a mass ratio of 1:8:2 and then ball-milled in a planetary ball mill for 5 h. After that, the mixture was dried in an 80 ℃ forced-air drying oven for 12 h. The dried powder was then passed through a 40-mesh sieve and placed in a muffle furnace. The temperature was increased from room temperature to 1100 ℃ at a rate of 5 ℃ / min and held for 3 h. The temperature was then lowered to room temperature with the furnace to preliminarily synthesize Ba2Zn3Si3O. 11 .

[0040] (3) The powder from step (2) is ball-milled a second time according to the chemical formula Ba2Zn3Si3O 11 -0.5wt% LBS was added to the corresponding mass percentage of LBS sintering aid, and the mixture was ball-milled for 6 h after being mixed with powder:zirconia balls:deionized water in a mass ratio of 1:8:2. The mixture was then placed in an 80 ℃ forced-air drying oven and dried for 12 h. After drying, the powder was passed through a 40-mesh sieve and 5 wt% PVA was added for granulation. After passing through an 80-mesh sieve again, the powder was pressed into ceramic green bodies with a diameter of 12 mm and a height of 5-6 mm using a mold under a pressure of 200 MPa.

[0041] (4) Place the blank from (3) in a muffle furnace, and under an air atmosphere, heat it to 550 °C at 5 °C / min to remove the binder for 1 hour, then heat it to 880 °C to sinter for 30 minutes, and then cool it down to room temperature with the furnace to obtain the microwave dielectric ceramic material.

[0042] (5) The microwave dielectric properties of the cylindrical sample were tested using the parallel plate resonance method on a network analyzer. The dielectric constant ε of the microwave dielectric ceramic material was determined using a network analyzer at room temperature (25°C). r and quality factor Q×f After heating the microwave dielectric ceramic material from 25°C to 75°C using a heating device, the temperature coefficient of the resonant frequency was statistically analyzed on a network analyzer. τ f .

[0043] Example 12 The difference between Example 12 and Example 11 is that the mass fraction of the sintering aid is 1%.

[0044] Example 13 The difference between Example 13 and Example 11 is that the mass fraction of the sintering aid is 1.5% and the sintering temperature is 850℃.

[0045] Example 14 The difference between Example 14 and Example 11 is that the mass fraction of the sintering aid is 2% and the sintering temperature is 850℃.

[0046] Table 1 shows the preparation conditions and dielectric properties of the microwave dielectric ceramic materials used in the examples.

[0047] As can be seen from Examples 1-10 in Table 1, the low-dielectric-loss microwave dielectric ceramics obtained by this invention have a dielectric constant of 8.5-10.5, a quality factor of 14000-21000 GHz, and a resonant frequency temperature coefficient of -62.7--72.7 ppm / °C. Furthermore, its dielectric loss is independent of the sintering time and heating rate, and its microwave dielectric properties are very stable. SEM characterization and density variation show that Ba2Zn3Si3O 11 Microwave dielectric ceramics exhibit dense sintering, maintaining low dielectric loss even with a holding time shortened to one minute. Examples 11-14 demonstrate that adding an appropriate amount of LBS sintering aid can lower the sintering temperature to below 900 °C, resulting in composite ceramics with a dielectric constant of 9.45–9.7, a quality factor of 6900–7300 GHz, and a resonant frequency temperature coefficient of -67.4–-70.7 ppm / °C. The density of the microwave dielectric ceramics does not change significantly with sintering time, highlighting its ability to rapidly densify.

[0048] Example 15 This embodiment provides a ceramic device, which consists of, from top to bottom, a silver electrode material and a microwave dielectric ceramic material prepared in Example 13, wherein the silver electrode material is printed on the microwave dielectric ceramic material.

[0049] Figure 2 The image shown is a cross-sectional SEM image of the ceramic device obtained in this embodiment. It can be seen that the microwave dielectric ceramic material is well bonded to the Ag electrode and there is no obvious diffusion.

[0050] Comparative Example 1 Comparative Example 1 discloses a ceramic material. The difference between Comparative Example 1 and Example 4 is that in step (1), BaCO3, ZnO and SiO2 are mixed according to the stoichiometric ratio of BaZnSiO4 to obtain a mixed raw material; in step (4), the sintering time is 180 min.

[0051] The ceramic material BaZnSiO4 requires a holding time of 180 minutes to achieve densification, compared to Ba2Zn3Si3O. 11 It has a higher dielectric constant and a lower quality factor. In addition, it has a smaller temperature coefficient of resonant frequency. Specific performance parameters are shown in Table 1.

[0052] Comparative Example 2 Comparative Example 2 discloses a ceramic material. The difference between Comparative Example 2 and Example 4 is that in step (1), BaCO3, ZnO and SiO2 are mixed according to the stoichiometric ratio of BaZn2Si2O7 to obtain a mixed raw material; in step (4), the sintering time is 180 min.

[0053] The ceramic material BaZn2Si2O7 requires a holding time of 180 minutes to achieve densification, and its sintering temperature is higher than that of Ba2Zn3Si3O. 11 Higher, but with a lower quality factor; specific performance parameters are shown in Table 1.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microwave dielectric ceramic material, characterized in that, The microwave dielectric ceramic material includes the main crystal phase Ba2Zn3Si3O. 11 .

2. The microwave dielectric ceramic material as described in claim 1, characterized in that, It also includes a sintering aid, wherein the mass percentage x of the sintering aid in the main crystalline phase satisfies: 0 < x ≤ 3%; the sintering aid is a mixture of Li2O, B2O3 and SiO2; Preferably, in the sintering aid, the molar percentage of Li2O is 30-50%, the molar percentage of B2O3 is 30-55%, and the molar percentage of SiO2 is 5-20%.

3. A method for preparing a microwave dielectric ceramic material as described in any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Using BaCO3, ZnO and SiO2 as raw materials, according to the chemical formula Ba2Zn3Si3O 11 The molar ratio of Ba, Zn, and Si elements is determined by mixing the ingredients, followed by wet ball milling, drying, and sieving to obtain a powder with uniform particles. (2) After the powder in step (1) is pre-fired, it is wet ball milled, dried and sieved again, and then the binder is added to granulate and molded, and then dry pressed to obtain the green porcelain body. (3) The raw ceramic blank is sintered in a muffle furnace after debinding to obtain the microwave dielectric ceramic material.

4. The method for preparing a microwave dielectric ceramic material according to claim 3, characterized in that, In step (2), after the powder is pre-calcined, a sintering aid is added; the mass percentage x of the sintering aid in the main crystalline phase satisfies 0 < 0. x ≤3%, the sintering aid is a mixture of Li2O, B2O3 and SiO2.

5. The method for preparing a microwave dielectric ceramic material according to claim 3, characterized in that, In step (2), the pre-firing temperature is 1080℃~1150℃ and the time is 3h~5h; In step (3), the adhesive discharge conditions are as follows: the temperature is raised to 450-600℃ at a heating rate of 3-10℃ / min, and kept at this temperature for 1-2 hours to discharge the adhesive.

6. The method for preparing a microwave dielectric ceramic material according to claim 3, characterized in that, The sintering conditions are as follows: the temperature is increased to 1150℃ to 1300℃ at a heating rate of 5 to 10℃ / min, and the sintering time is 1 to 30 min.

7. The method for preparing a microwave dielectric ceramic material according to claim 4, characterized in that, The sintering conditions are as follows: the temperature is increased to 800℃ to 900℃ at a heating rate of 5 to 10℃ / min, and the sintering time is 1 to 30 min.

8. The method for preparing a microwave dielectric ceramic material according to claim 3, characterized in that, The drying conditions in steps (1) and (2) are: drying temperature 70℃~100℃, drying time 8h~12h; The binder comprises 4% to 8% of the powder mass, preferably 5%; the binder is selected from polyvinyl alcohol, paraffin wax or polyvinyl butyral.

9. A ceramic device, characterized in that, The ceramic device comprises, from top to bottom, an electrode material and the microwave dielectric ceramic material as described in any one of claims 1-2; preferably, the electrode material is selected from silver or a silver-palladium alloy.

10. The application of a ceramic device as described in claim 9, characterized in that, The ceramic device is used in antennas, filters, duplexers, or dielectric substrates.

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