Low-temperature sintered high dielectric constant microwave dielectric ceramic, preparation method and application thereof

Abstract

The application discloses a low-temperature sintered high-dielectric-constant microwave dielectric ceramic and a preparation method and application thereof. The microwave dielectric ceramic comprises main materials with a composition expression of aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and auxiliary materials with a chemical formula of xZnO-yH3BO3, wherein 29%<=a<=31%, 49%<=b<=51%, 5%<=c<=7%, 1%<=d<=3%, 4%<=e<=6%, 4%<=f<=6%, 65%<=x<=68%, and 32%<=y<=35%; the mass ratio of the main materials to the auxiliary materials is 1:(0.14-0.16). The microwave dielectric ceramic can keep the following microwave performances under the condition of low-temperature sintering: a dielectric constant Dk=35+ / -2, a quality factor of 20000 GHz or more, a dielectric loss Df<=0.03%, and a resonance frequency temperature coefficient tauf being within + / -10 ppm / deg C.

Description

Technical Field

[0001] This invention belongs to the field of electronic information materials technology, specifically relating to a low-temperature sintered high dielectric constant microwave dielectric ceramic, its preparation method, and its application. Background Technology

[0002] As microwave communication electronics are used at increasingly higher frequencies, the performance requirements for microwave dielectric ceramics, which serve as the primary signal carriers, in corresponding signal filter devices are becoming increasingly stringent. Furthermore, in mobile filter applications, the requirement for thin and compact components is essential. Therefore, currently, commercially available ceramic materials for signal filtering in SAW and LC filters, with a dielectric constant range of 35±2, exhibit dielectric losses ≥0.05% and temperature drift ≥±10ppm / ℃. Moreover, lower sintering temperatures result in lower sintering strength, making them prone to defects such as ceramic body fracture and chipping in practical applications. Therefore, in the LTCC field, to achieve co-firing with silver electrodes, a material is needed with a sintering temperature below 900℃, a dielectric constant of 35±2, a Qf value above 20000GHz, a dielectric loss of less than 0.03%, and good ceramic body strength. This represents a promising development direction for microwave dielectric ceramics used in low-temperature co-fired filters. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a low-temperature sintered high-dielectric-constant microwave dielectric ceramic, its preparation method, and its applications. The microwave dielectric ceramic of the present invention can maintain the following microwave properties under low-temperature sintering conditions (850–900℃): dielectric constant Dk = 35 ± 2, quality factor Qf > 20000 GHz, dielectric loss Df ≤ 0.03%, and resonant frequency temperature coefficient τf within ± 10 ppm / ℃. This meets the technical requirements for signal filtering in microwave communication and has significant industrial application value.

[0004] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0005] This invention provides a low-temperature sintered high dielectric constant microwave dielectric ceramic, comprising a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein 29%≤a≤31%, 49%≤b≤51%, 5%≤c≤7%, 1%≤d≤3%, 4%≤e≤6%, 4%≤f≤6%; 65%≤x≤68%, 32%≤y≤35%; a~f, x, and y are mass percentages, a+b+c+d+e+f=100%, x+y=100%; and the mass ratio of the main material to the auxiliary material is 1:(0.14~0.16).

[0006] Furthermore, the microwave dielectric ceramic includes the crystalline phases BaTi4O9 and Li2(Cu). k Zn1- k )Ti3O8 and Ba(Zr z Ti 1-z )4O9, and 0 < k < 1, 0 < z < 1; the microwave dielectric ceramic also includes the glass phase ZnB2O4.

[0007] Furthermore, the microwave dielectric ceramic material has a sintering temperature of 850–900℃, a dielectric constant of 33–37, a quality factor Q×f of ≥20000GHz, a dielectric loss Df≤0.03%, and a resonant frequency temperature coefficient τf within ±10ppm / ℃.

[0008] Another aspect of the present invention provides a method for preparing high dielectric constant microwave dielectric ceramics sintered at low temperatures, comprising the following steps:

[0009] 1) Weigh BaCO3, TiO2, CuO, ZnO, Li2CO3 and ZrO2 according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then keep them warm and pre-fire them to obtain the main material base material.

[0010] 2) Weigh ZnO and H3BO3 according to their chemical formulas. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and place them in an alumina crucible. Then keep them warm and pre-fire them to obtain the auxiliary material base.

[0011] 3) Mix the main material substrate obtained in step 1) and the auxiliary material substrate obtained in step 2) according to the mass ratio, and then ball mill them thoroughly. After ball milling, dry, granulate, and sieve.

[0012] 4) Press the granules after sieving in step 3) into shape, and finally sinter them to obtain the high dielectric constant microwave dielectric ceramic material.

[0013] Furthermore, the temperature of the heat preservation and preheating process in steps 1) and 2) is 600-800℃, and the heat preservation and preheating time is 3-5h.

[0014] Furthermore, the sintering process in step 4) is carried out at 850–900°C for 3–8 hours.

[0015] Furthermore, the granulation described in step 3) involves mixing the dried powder with a binder and then forming micron-sized spherical particles.

[0016] Furthermore, the adhesive is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution, or methylcellulose.

[0017] Furthermore, in step 4), the granules are pressed into cylinders with a diameter of 10 mm and a height of 6 mm.

[0018] The present invention also provides the application of this low-temperature sintered high dielectric constant microwave dielectric ceramic in LTCC filters.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The microwave dielectric ceramic of the present invention contains three crystal phases in its main material. Furthermore, the present invention also uses a glass phase with low melting point characteristics to match the main crystal phase. The phases are well matched, which eliminates the defects of general barium-titanium ceramics, such as a sharp decrease in Q value and a sharp increase in loss after adding a large proportion of glass material. At the same time, it can achieve dense sintering below the melting point of the silver internal electrode.

[0021] The microwave dielectric ceramic of the present invention can maintain the following microwave properties under low-temperature sintering conditions (850~900℃): dielectric constant Dk=35±2, quality factor Qf>20000GHz, dielectric loss Df≤0.03%, and resonant frequency temperature coefficient τf within ±10ppm / ℃. It can meet the technical requirements of signal filtering in microwave communication and has important industrial application value. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a low-temperature sintered high dielectric constant microwave dielectric ceramic, comprising a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein 29%≤a≤31%, 49%≤b≤51%, 5%≤c≤7%, 1%≤d≤3%, 4%≤e≤6%, 4%≤f≤6%; 65%≤x≤68%, 32%≤y≤35%; a~f, x, and y are mass percentages, a+b+c+d+e+f=100%, x+y=100%; the mass ratio of the main material to the auxiliary material is 1:(0.14~0.16).

[0024] The microwave dielectric ceramic includes the crystalline phases BaTi4O9 and Li2(Cu). k Zn1- k )Ti3O8 and Ba(Zr z Ti1-z The microwave dielectric ceramic also includes a glassy phase ZnB₂O₄, where k < k < 1 and z < 1. The values ​​of k and z are determined by the molar ratio of the main raw materials.

[0025] The dielectric constant of this microwave dielectric ceramic material is 33-37, the quality factor Q×f is above 20000GHz, the dielectric loss Df≤0.03%, and the temperature coefficient of resonant frequency τf is within ±10ppm / ℃.

[0026] The method for preparing the low-temperature sintered high-dielectric-constant microwave dielectric ceramic includes the following steps:

[0027] 1) Weigh BaCO3, TiO2, CuO, ZnO, Li2CO3 and ZrO2 according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then keep them warm and pre-fire them to obtain the main material base material.

[0028] 2) Weigh ZnO and H3BO3 according to their chemical formulas. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and place them in an alumina crucible. Then keep them warm and pre-fire them to obtain the auxiliary material base.

[0029] 3) The main material substrate obtained in step 1) and the auxiliary material substrate obtained in step 2) are mixed according to the mass ratio, and then ball-milled. After ball milling, the mixture is dried, granulated, and sieved. The granulation is to mix the dried powder with a binder and then form micron-sized spherical particles. The binder is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution, or methylcellulose.

[0030] 4) Press the sieving granules from step 3) into cylinders with a diameter of 10 mm and a height of 6 mm, and finally sinter them to obtain the high dielectric constant microwave dielectric ceramic material.

[0031] In step 1) and step 2), the temperature for the preheating process is 600–800℃, and the preheating time is 3–5 hours. In step 4), the sintering process is carried out at 850–900℃ for 3–8 hours.

[0032] This low-temperature sintered high-dielectric-constant microwave dielectric ceramic can be used in LTCC filters.

[0033] The following embodiments will further illustrate the present invention, but are not intended to limit the invention.

[0034] Example 1

[0035] The low-temperature sintered high dielectric constant microwave dielectric ceramic of Example 1 comprises a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to f, x and y are mass percentages, a = 31%, b = 49%, c = 7%, d = 1%, e = 6%, f = 6%; x = 65%, y = 35%; and the mass ratio of the main material to the auxiliary material is 1:0.16.

[0036] The method for preparing the low-temperature sintered high-dielectric-constant microwave dielectric ceramic includes the following steps:

[0037] 1) Weigh BaCO3, TiO2, CuO, ZnO, Li2CO3 and ZrO2 according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-fire them at 750℃ for 3 hours to obtain the main material base material.

[0038] 2) Weigh ZnO and H3BO3 according to the composition formula of the auxiliary materials. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-calcine them at 750℃ for 3 hours to obtain the auxiliary material base material.

[0039] 3) Mix the main material base obtained in step 1) and the auxiliary material base obtained in step 2) according to the mass ratio, then ball mill thoroughly, and then dry, granulate and sieve.

[0040] 4) Press the granules after sieving in step 3) into shape, and finally sinter them at 850℃ for 4 hours to obtain the high dielectric constant microwave dielectric ceramic material.

[0041] Example 2

[0042] The low-temperature sintered high dielectric constant microwave dielectric ceramic of Example 2 includes a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to f, x and y are mass percentages, a = 30.5%, b = 49%, c = 7%, d = 2%, e = 5.5%, f = 6%; x = 65%, y = 35%; the mass ratio of the main material to the auxiliary material is 1:0.155.

[0043] The difference between the preparation method of Example 2 and Example 1 is that the sintering temperature in step 4) is 860℃.

[0044] Example 3

[0045] The low-temperature sintered high dielectric constant microwave dielectric ceramic of Example 3 includes a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to f, x and y are mass percentages, a = 30%, b = 50%, c = 6%, d = 3%, e = 6%, f = 5%; x = 65%, y = 35%; and the mass ratio of the main material to the auxiliary material is 1:0.15.

[0046] The difference between the preparation method of Example 3 and Example 1 is that the sintering temperature in step 4) is 870℃.

[0047] Example 4

[0048] The low-temperature sintered high dielectric constant microwave dielectric ceramic of Example 4 includes a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to f, x and y are mass percentages, a = 29.5%, b = 51%, c = 7%, d = 2%, e = 5.5%, f = 5%; x = 65%, y = 35%; the mass ratio of the main material to the auxiliary material is 1:0.145.

[0049] The difference between the preparation method of Example 4 and Example 1 is that the sintering temperature in step 4) is 880℃.

[0050] Example 5

[0051] The low-temperature sintered high dielectric constant microwave dielectric ceramic of Example 5 comprises a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2 and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to f, x and y are mass percentages, a = 29%, b = 51%, c = 7%, d = 3%, e = 4%, f = 6%; x = 65%, y = 35%; and the mass ratio of the main material to the auxiliary material is 1:0.14.

[0052] The difference between the preparation method of Example 5 and Example 1 is that the sintering temperature in step 4) is 890℃.

[0053] Comparative Example 1

[0054] The microwave dielectric ceramic material of Comparative Example 1 has the composition formula aBaCO3-bTiO2, where a and b are mass percentages, a = 25% and b = 75%.

[0055] The preparation method of the microwave dielectric ceramic material in Comparative Example 1 includes the following steps:

[0056] 1) Weigh BaCO3 and TiO2 according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-calcine them at 1000℃ for 3 hours to obtain the powder base material.

[0057] 2) The powder substrate obtained in step 1) above is fully ball-milled, and then dried, granulated and sieved.

[0058] 3) Press the granules after sieving in step 2) into cylinders with a diameter of 10 mm and a height of 6 mm, and finally sinter them at 1200℃ for 4 h to obtain the microwave dielectric ceramic material.

[0059] Comparative Example 2

[0060] The microwave dielectric ceramic material of Comparative Example 2 includes a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to d, x and y are mass percentages, a = 25%, b = 60%, c = 10%, d = 5%; x = 65%, y = 35%; and the mass ratio of the main material to the auxiliary material is 1:0.1.

[0061] The preparation method of the microwave dielectric ceramic material in Comparative Example 2 includes the following steps:

[0062] 1) Weigh BaCO3, TiO2, CuO and ZnO according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-fire them at 750℃ for 3 hours to obtain the main material base material.

[0063] 2) Weigh ZnO and H3BO3 according to the chemical formula of the excipients. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-calcine them at 1000℃ for 3 hours to obtain the excipient base material.

[0064] 3) Mix the main material base obtained in step 1) and the auxiliary material base obtained in step 2) according to the mass ratio, then ball mill thoroughly, and then dry, granulate and sieve.

[0065] 4) Press the granules after sieving in step 3) into shape, and finally sinter them at 1100℃ for 4 hours to obtain the microwave dielectric ceramic material.

[0066] Comparative Example 3

[0067] The microwave dielectric ceramic material of Comparative Example 3 includes a main material with the composition formula aBaCO3-bTiO2-cZnO-dCuO and an auxiliary material with the chemical formula xZnO-yH3BO3, wherein a to d, x and y are mass percentages, a = 30%, b = 60%, c = 5%, d = 5%; x = 65%, y = 35%; and the mass ratio of the main material to the auxiliary material is 1:0.1.

[0068] The preparation method of the microwave dielectric ceramic material of Comparative Example 3 includes the following steps:

[0069] 1) Weigh BaCO3, TiO2, CuO and ZnO according to the composition formula of the main material. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-fire them at 750℃ for 3 hours to obtain the main material base material.

[0070] 2) Weigh ZnO and H3BO3 according to the composition formula of the auxiliary materials. Mix the weighed materials thoroughly and then ball mill them. After ball milling, dry and sieve them and put them into a corundum crucible. Then, pre-calcine them at 1000℃ for 3 hours to obtain the auxiliary material base material.

[0071] 3) Mix the main material base obtained in step 1) and the auxiliary material base obtained in step 2) according to the mass ratio, then ball mill thoroughly, and then dry, granulate and sieve.

[0072] 4) Press the granules after sieving in step 3) into shape, and finally sinter them at 1100℃ for 4 hours to obtain the microwave dielectric ceramic material.

[0073] Performance testing

[0074] The microwave dielectric properties of microwave dielectric ceramics obtained by testing them using a microwave network analyzer are shown in Table 1.

[0075] Table 1 shows the parameter values ​​for the examples and comparative examples, as well as the microwave dielectric properties of the microwave dielectric ceramics.

[0076]

[0077] As shown in Table 1, the microwave dielectric ceramic materials of Examples 1-5 of this invention can maintain the following microwave properties under low-temperature sintering conditions (850-900℃): dielectric constant Dk = 35 ± 2, quality factor Qf > 20000 GHz, dielectric loss Df ≤ 0.03%, and resonant frequency temperature coefficient τf within ± 10 ppm / ℃, which can meet the technical requirements of signal filtering in microwave communication. The microwave dielectric ceramic of Comparative Example 1 has a higher sintering temperature, higher dielectric loss, and a larger resonant frequency temperature coefficient. The microwave dielectric ceramics of Comparative Examples 2 and 3, compared to Comparative Example 1, contain glass frit, which lowers the sintering temperature to some extent, but results in a lower quality factor and higher dielectric loss.

[0078] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any modifications or equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A low temperature sintered high dielectric constant microwave dielectric ceramic, characterized by: The main material has a composition expression of aBaCO3-bTiO2-cZnO-dCuO-eLi2CO3-fZrO2, and the auxiliary material has a chemical formula of xZnO-yH3BO3, wherein 29%≤a≤31%, 49%≤b≤51%, 5%≤c≤7%, 1%≤d≤3%, 4%≤e≤6%, 4%≤f≤6%, 65%≤x≤68%, and 32%≤y≤35%; a, b, c, d, e, f, x, and y are mass percentages, a+b+c+d+e+f=100%, and x+y=100%; the mass ratio of the main material to the auxiliary material is 1:(0.14-0.16). The microwave dielectric ceramic comprises a crystal phase BaTi409, Li2(Cu k Zn1- k )Ti308 and Ba(Zr z Ti 1-z )409, and 0 < k < 1, 0 < z < 1; the microwave dielectric ceramic further comprises a glass phase ZnB204.

2. The low temperature sintered high dielectric constant microwave dielectric ceramic of claim 1, wherein: The microwave dielectric ceramic material has a sintering temperature of 850-900 ℃, a dielectric constant of 33-37, a quality factor Qxf value of more than 20000 GHz, a dielectric loss Df of less than or equal to 0.03%, and a resonance frequency temperature coefficient τf of less than or equal to ±10 ppm / ℃.

3. A method of producing a low-temperature-sintered high-dielectric-constant microwave dielectric ceramic according to any one of claims 1 to 2, characterized by, The method comprises the following steps: 1) BaCO3, TiO2, CuO, ZnO, Li2CO3, and ZrO2 are weighed according to the composition expression of the main material, and then mixed and ball milled, and the ball-milled material is dried, sieved, and placed in a corundum crucible for heat preservation and pre-sintering to obtain a main material base material; 2) ZnO and H3BO3 are weighed according to the chemical formula of the auxiliary material, and then mixed and ball milled, and the ball-milled material is dried, sieved, and placed in a corundum crucible for heat preservation and pre-sintering to obtain an auxiliary material base material; 3) the main material base material obtained in step 1) and the auxiliary material base material obtained in step 2) are mixed according to a mass ratio, and then ball milled, dried, granulated, and sieved; 4) the granulated material after sieving in step 3) is pressed into a cylinder, and finally sintered to obtain the high dielectric constant microwave dielectric ceramic material.

4. The method of claim 3, wherein the low-temperature sintered high dielectric constant microwave dielectric ceramic is represented by the formula: (Ba1-xSrx) (Ti1-yZry) O3, wherein 0 < x < 1 and 0 < y < 1. The heat preservation and pre-sintering process in steps 1) and 2) has a temperature of 600-800 ℃, and a heat preservation and pre-sintering time of 3-5 h.

5. The method of claim 3, wherein the low-temperature sintered high dielectric constant microwave dielectric ceramic is represented by the formula: (Ba1-xSrx) (Ti1-yZry) O3, wherein x and y are each independently 0.0001 to 0.

1. The sintering process in step 4) is sintering at 850-900 ℃ for 3-8 h.

6. The method of claim 3, wherein the low-temperature sintered high dielectric constant microwave dielectric ceramic is represented by the formula: (Ba1-xSrx) (Ti1-yZry) O3, wherein 0 < x < 1 and 0 < y < 1. The granulation in step 3) is mixing the dried powder with a binder, and then making micron-sized spherical particles.

7. The method for preparing high-dielectric-constant microwave dielectric ceramics sintered at low temperatures according to claim 6, characterized in that, The binder is at least one selected from a polyvinyl alcohol solution, a polyvinyl butyral solution, an acrylic acid solution, or methyl cellulose.

8. The method of claim 3, wherein the low-temperature sintered high dielectric constant microwave dielectric ceramic is represented by the formula: (Ba1-xSrx) (Ti1-yZry) O3, wherein x and y are each independently 0.0001 to 0.

1. In step 4), the granulated material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm.

9. Application of the low-temperature sintered high dielectric constant microwave dielectric ceramic in claim 1-2 to an LTCC filter.

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