A microwave dielectric ceramic material for filters and its preparation method

Abstract

The present invention discloses a microwave dielectric ceramic material for filters, which is made of the following raw material components in molar percentages: BaCO3 10 mol% - 20 mol%, TiO2 75 mol% - 80 mol%, ZnO 2 mol% - 4 mol%, Li2CO3 2 mol% - 4 mol%, ZrO2 1 mol% - 2 mol%. The present invention also discloses a preparation method of the microwave dielectric ceramic material for filters. This microwave dielectric ceramic material can maintain the following microwave properties under the condition of low-temperature sintering (1100 - 1200 °C): Er = 35 ± 2, Qf > 45000 GHz, τf is adjustable and meets the requirement within ±5 ppm / °C, which can meet the technical requirements of signal filter devices and has important industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic information materials, and specifically relates to a microwave dielectric ceramic material for filters and a preparation method thereof. Background Art

[0002] As the operating frequency of microwave communication electronics develops towards higher and higher frequency bands, the performance requirements for microwave dielectric ceramics, which are the main signal carriers in corresponding signal filter devices, are becoming increasingly stringent. Currently, for commercially available materials used for signal filtering with a dielectric constant range of 35 ± 2, their temperature coefficients are generally greater than ±5 ppm / °C; or the Ba-Ti-Cu-Zn-O system is adopted. Due to the addition of Cu element, the grain growth of ceramics in this system is very obvious, resulting in a significant reduction in the strength of the ceramics. Defects such as porcelain body fracture and corner chipping are likely to occur during actual application, and the frequency temperature coefficient of the entire system is uncontrollable. Adjusting the frequency temperature coefficient will significantly affect the Q value of the entire system and will also affect the dielectric constant to a certain extent.

[0003] Therefore, developing a material with a dielectric constant of 35 ± 2, a Qf value higher than 45000, which can be sintered at low temperature, and has good porcelain body strength is a very good development direction for microwave dielectric ceramics for filters. Summary of the Invention

[0004] To solve the above technical problems, the purpose of the present invention is to provide a microwave dielectric ceramic material for filters and a preparation method thereof; this microwave dielectric ceramic material can maintain the following microwave properties under the condition of low-temperature sintering (1100 - 1200 °C): Er = 35 ± 2, Qf > 45000 GHz, τf is adjustable and meets the requirement within ±5 ppm / °C, can meet the technical requirements of signal filter devices, and has important industrial application value.

[0005] To achieve the above technical purpose and reach the above technical effect, the present invention is realized through the following technical solutions:

[0006] On the one hand, the present invention provides a microwave dielectric ceramic material for filters, which is made of the following raw material components in mole percentages:

[0007] BaCO3 10 mol% - 20 mol%, TiO2 75 mol% - 80 mol%, ZnO 2 mol% - 4 mol%, Li2CO3 2 mol% - 4 mol%, ZrO2 1 mol% - 2 mol%;

[0008] This microwave dielectric ceramic includes a main crystal phase and a doped crystal phase. The composition expression of the main crystal phase is BaTi4O9, and the doped crystal phase includes Ba(Zr x Ti1-x ) 4O9 and LiZn y Ti 1.75-y / 2 O4, and the values of x and y in the composition expression of the doped crystal phase are determined by the molar percentages of the raw material components.

[0009] Furthermore, the sintering temperature of the microwave dielectric ceramic material is 1100 - 1200 °C, the dielectric constant is 33 - 37, the Q×f value of the quality factor is above 45000 GHz, and the absolute value of the resonant frequency temperature coefficient is below 5 ppm / °C.

[0010] On the other hand, the present invention provides a method for preparing a microwave dielectric ceramic material for a filter, comprising the following steps:

[0011] 1) Weigh BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 according to the molar percentages respectively, mix them thoroughly and then ball-mill. After ball-milling, dry, sieve and put them into a corundum crucible, and then perform heat preservation pre-sintering to obtain a powder substrate;

[0012] 2) Ball-mill the powder substrate obtained in step 1) above thoroughly, and after ball-milling, dry, granulate and sieve;

[0013] 3) Press the sieved granular material into a shape, and finally obtain the microwave dielectric ceramic material for the filter through sintering.

[0014] Furthermore, the temperature of the heat preservation pre-sintering process in step (1) is 800 - 1100 °C, and the heat preservation pre-sintering time is 3 - 5 h.

[0015] Furthermore, the sintering process in step (3) is sintering at 1100 - 1200 °C for 3 - 8 h.

[0016] Furthermore, the granulation in step (2) is to mix the dried powder with a binder, and then make it into micron-sized spherical particles.

[0017] Furthermore, the binder is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution or methyl cellulose.

[0018] Furthermore, in step (3), the granular material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm.

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

[0020] The microwave dielectric ceramic of the present invention is sintered from BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 as raw materials. The sintered microwave dielectric ceramic includes the main crystal phase BaTi4O9 and the doped crystal phase LiZn y Ti1.75-y / 2 O4 and Ba(Zr x Ti 1-x )4O9, by doping with LiZn y Ti 1.75-y / 2 O4 crystal phase with a small dielectric constant and continuously controllable temperature coefficient (the temperature coefficient changes with the ratio of Ti and Zn), the temperature coefficient can be continuously adjusted, and by equivalently doping Ba(Zr x Ti 1-x )4O9, the ceramic strength can be improved.

[0021] The microwave dielectric ceramic material of the present invention can maintain the following microwave properties under the condition of low-temperature sintering (1100 - 1200 °C): Er = 35 ± 2, Qf > 45000 GHz, τf is adjustable and meets the requirement within ±5 ppm / °C, which can meet the technical requirements of signal filter devices and has important industrial application value. Specific Embodiments

[0022] The technical solutions in the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] The present invention provides a microwave dielectric ceramic material for filters, which is made of the following raw material components in mole percentages:

[0024] BaCO3 10 mol% - 20 mol%, TiO2 75 mol% - 80 mol%, ZnO 2 mol% - 4 mol%, Li2CO3 2 mol% - 4 mol%, ZrO2 1 mol% - 2 mol%;

[0025] The microwave dielectric ceramic includes a main crystal phase and a doped crystal phase. The composition expression of the main crystal phase is BaTi4O9, and the doped crystal phase includes Ba(Zr x Ti 1-x )4O9 and LiZn y Ti 1.75-y / 2 O4, and the values of x and y in the composition expression of the doped crystal phase are determined by the mole percentages of the raw material components.

[0026] The sintering temperature of the microwave dielectric ceramic material is 1100 - 1200 °C, the dielectric constant is 33 - 37, the quality factor Q×f value is above 45000 GHz, and the absolute value of the resonant frequency temperature coefficient is below 5 ppm / °C.

[0027] Preparation method of microwave dielectric ceramic material for this filter, comprising the following steps:

[0028] 1) Charge BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 respectively according to mole percentages, mix thoroughly and then ball-mill. After ball-milling, dry, sieve and put into a corundum crucible, and then keep it at a temperature of 800 - 1100 °C for heat-preserving pre-sintering for 3 - 5 h to obtain a powder substrate;

[0029] 2) Ball-mill the powder substrate obtained in the above step 1 thoroughly, dry, granulate and sieve after ball-milling; the granulation is to mix the dried powder with a binder and then make it into micron-sized spherical particles; the binder is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution or methyl cellulose;

[0030] 3) Press the sieved granular material in step 2 into a cylinder with a diameter of 10 mm and a height of 6 mm, and finally sinter at 1100 - 1200 °C for 3 - 8 h to obtain the microwave dielectric ceramic material for this filter.

[0031] The following examples will further illustrate the present invention, but do not limit the present invention thereby.

[0032] Example 1

[0033] The raw material composition expression of the microwave dielectric ceramic material for the filter in Example 1 is aBaCO3 - bTiO2 - cZnO - dLi2CO3 - eZrO2; a, b, c, d, e respectively independently represent mole percentages, a = 16 mol%, b = 75 mol%, c = 4 mol%, d = 4 mol%, e = 1 mol%.

[0034] The preparation method of the microwave dielectric ceramic material for the filter in Example 1, comprising the following steps:

[0035] 1) Charge BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 respectively according to the mole percentages of the raw material composition expression, mix thoroughly and then ball-mill. After ball-milling, dry, sieve and put into a corundum crucible, and then keep it at a temperature of 1000 °C for heat-preserving pre-sintering for 4 h to obtain a powder substrate;

[0036] 2) Ball-mill the powder substrate obtained in the above step 1 thoroughly, dry, granulate and sieve after ball-milling;

[0037] 3) Press the sieved granular material in step 2 into a cylinder with a diameter of 10 mm and a height of 6 mm, and finally sinter at 1100 °C for 5 h to obtain the microwave dielectric ceramic material for this filter.

[0038] Example 2

[0039] The raw material composition expression of the microwave dielectric ceramic material for the filter in this embodiment 2 is aBaCO3-bTiO2-cZnO-dLi2CO3-eZrO2; a, b, c, d, e independently represent the molar percentage, a=18mol%, b=75mol%, c=3mol%, d=3mol%, e=1mol%.

[0040] The method for preparing the microwave dielectric ceramic material for the filter of the second embodiment comprises the following steps:

[0041] 1) BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 are prepared according to the molar percentage of the raw material composition expression, and the mixture is fully mixed and then ball-milled. After ball-milling, the mixture is dried, sieved, and placed in a corundum crucible, and then pre-calcined at 1000° C. for 4 hours to obtain a powder substrate;

[0042] 2) fully ball-milling the powder substrate obtained in step 1), drying, granulating and sieving after ball-milling;

[0043] 3) The sieved granules in step 2) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and finally sintered at 1120° C. for 5 h to obtain the microwave dielectric ceramic material for the filter.

[0044] Example 3

[0045] The raw material composition expression of the microwave dielectric ceramic material for the filter in this embodiment 3 is aBaCO3-bTiO2-cZnO-dLi2CO3-eZrO2; a, b, c, d, e independently represent the molar percentage, a=12mol%, b=80mol%, c=3mol%, d=3mol%, e=2mol%.

[0046] The difference between the preparation method of Example 3 and that of Example 1 is that the sintering temperature of step (3) is 1140°C.

[0047] Example 4

[0048] The raw material composition expression of the microwave dielectric ceramic material for the filter in Example 4 is aBaCO3-bTiO2-cZnO-dLi2CO3-eZrO2; a, b, c, d, and e independently represent molar percentages, a=19mol%, b=75mol%, c=2mol%, d=2mol%, and e=2mol%.

[0049] The difference between the preparation method of Example 4 and that of Example 1 is that the sintering temperature of step (3) is 1180°C.

[0050] Example 5

[0051] The raw material composition expression of the microwave dielectric ceramic material for the filter in Example 5 is aBaCO3-bTiO2-cZnO-dLi2CO3-eZrO2; a, b, c, d, and e independently represent molar percentages, a=14mol%, b=80mol%, c=2mol%, d=2mol%, and e=2mol%.

[0052] The difference between the preparation method of Example 5 and that of Example 1 is that the sintering temperature of step (3) is 1200°C.

[0053] Comparative Example 1

[0054] The raw material composition expression of the microwave dielectric ceramic material of Comparative Example 1 is 15 mol% BaCO3-85 mol% TiO2-10 mol% Li2CO3.

[0055] The method for preparing the microwave dielectric ceramic material of Comparative Example 1 comprises the following steps:

[0056] 1) BaCO3, TiO2 and Li2CO3 are prepared according to the molar percentage of the raw material composition expression, mixed sufficiently and then ball-milled, dried and sieved after ball-milling, and put into a corundum crucible, and then pre-calcined at a temperature of 1000° C. for 4 hours to obtain a powder substrate;

[0057] 2) fully ball-milling the powder substrate obtained in step 1), drying, granulating and sieving after ball-milling;

[0058] 3) The sieved granules in step 2) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and finally sintered at 1200° C. for 5 h to obtain the microwave dielectric ceramic material for the filter.

[0059] Comparative Example 2

[0060] The raw material composition expression of the microwave dielectric ceramic material of Comparative Example 2 is 15 mol% BaCO3-75 mol% TiO2-10 mol% ZnO.

[0061] The method for preparing the microwave dielectric ceramic material of Comparative Example 2 comprises the following steps:

[0062] 1) BaCO3, TiO2 and ZnO are prepared according to the molar percentage of the raw material composition expression, mixed sufficiently and then ball-milled, dried and sieved after ball-milling, and put into a corundum crucible, and then pre-calcined at a temperature of 1000° C. for 4 hours to obtain a powder substrate;

[0063] 2) fully ball-milling the powder substrate obtained in step 1), drying, granulating and sieving after ball-milling;

[0064] 3) The sieved granules in step 2) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and finally sintered at 1250° C. for 5 h to obtain the microwave dielectric ceramic material for the filter.

[0065] Comparative Example 3

[0066] The raw material composition expression of the microwave dielectric ceramic material of Comparative Example 3 is 20 mol% BaCO3-69 mol% TiO2-10 mol% ZnO-1 mol% ZrO2.

[0067] The preparation method of the microwave dielectric ceramic material of Comparative Example 3 comprises the following steps:

[0068] 1) BaCO3, TiO2, ZnO and ZrO2 are prepared according to the molar percentage of the raw material composition expression, and the mixture is fully mixed and then ball-milled. After ball-milling, the mixture is dried, sieved and placed in a corundum crucible, and then pre-calcined at 1000° C. for 4 hours to obtain a powder substrate;

[0069] 2) fully ball-milling the powder substrate obtained in step 1), drying, granulating and sieving after ball-milling;

[0070] 3) The sieved granular material in step 2) is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm, and finally sintered at 1300° C. for 5 hours to obtain the microwave dielectric ceramic material for the filter.

[0071] Performance Testing

[0072] The microwave dielectric properties of the microwave dielectric ceramic material tested using a microwave network analyzer are shown in Table 1.

[0073] Table 1 Parameter values of the embodiments and comparative examples and microwave dielectric properties of microwave dielectric ceramics

[0074]

[0075]

[0076] It can be seen from Table 1 that, compared with the microwave dielectric ceramic materials of comparative examples 1-3, the microwave dielectric ceramic materials of embodiments 1-5 of the present invention can maintain the following microwave properties under low temperature sintering conditions (1100-1200°C): Er=35±2, Qf>45000GHz, and the resonant frequency temperature coefficient τf is within ±5ppm / °C, which can meet the technical requirements of signal filter devices and has important industrial application value.

[0077] The above are only embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any modifications or equivalent transformations made using the content of the specification of the present invention, 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 microwave dielectric ceramic material for a filter, characterized in that: The microwave dielectric ceramic material is made of the following raw material components in molar percentage: BaCO3 10mol%~20mol%, TiO2 75mol%~80mol%, ZnO 2mol%~4mol%, Li2CO32mol%~4mol%, ZrO2 1mol%~2mol%; The microwave dielectric ceramic comprises a main crystal phase and a doped crystal phase. The composition expression of the main crystal phase is BaTi4O9, and the doped crystal phase comprises Ba(Zr x Ti 1-x )4O9 and LiZn y Ti 1.75-y / 2 O4. The values of x and y in the composition expression of the doped crystal phase are determined by the molar percentages of the raw material components.

2. The microwave dielectric ceramic material for a filter according to claim 1, wherein: The microwave dielectric ceramic material has a sintering temperature of 1100-1200° C., a dielectric constant of 33-37, a quality factor Q×f value of more than 45000 GHz, and an absolute value of a resonant frequency temperature coefficient of less than 5 ppm / ° C.

3. A preparation method of a microwave dielectric ceramic material for a filter as described in claim 1 or 2, characterized in that, The following steps are involved: 1) BaCO3, TiO2, ZnO, Li2CO3, and ZrO2 are prepared according to molar percentage, mixed sufficiently, and then ball-milled. After ball-milling, the mixture is dried, sieved, and placed in a corundum crucible, and then pre-calcined at a temperature of 100° to obtain a powder substrate; 2) fully ball-milling the powder substrate obtained in step 1), drying, granulating and sieving after ball-milling; 3) The sieved granular material in step 2) is pressed into shape, and finally sintered to obtain the microwave dielectric ceramic material for the filter.

4. The preparation method of the microwave dielectric ceramic material for a filter according to claim 3, wherein, The temperature of the heat preservation and pre-burning process in step (1) is 800-1100° C., and the heat preservation and pre-burning time is 3-5 hours.

5. The preparation method of the microwave dielectric ceramic material for a filter according to claim 3, wherein The sintering process in step (3) is sintering at 1100-1200° C. for 3-8 hours.

6. The preparation method of the microwave dielectric ceramic material for a filter according to claim 3, characterized in that, The granulation described in step (2) is to mix the dried powder with a binder and then make micron-sized spherical particles.

7. The preparation method of the microwave dielectric ceramic material for a filter according to claim 6, wherein, The binder is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution or methyl cellulose.

8. The preparation method of the microwave dielectric ceramic material for a filter according to claim 3, characterized in that, In step (3), the granular material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm.

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