Low-temperature sintered medium-dielectric-constant microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a low-temperature sintered medium-dielectric-constant microwave dielectric ceramic material and a preparation method thereof. The composition expression of the microwave dielectric ceramic material is xMgTiO3-yCaTiO3-z (aMg2SiO4-bMgSiO3), and x, y, a and b are mole fractions and meet the following conditions: x + y = 1, 0.05 < = y < = 0.15, a = 0.5, and b = 0.5; and z is a mass fraction and is 1-10 wt.% of the mass of the xMgTiO3-yCaTiO3. The microwave dielectric ceramic material can maintain the following microwave properties under the sintering condition of 1250-1300 DEG C: the dielectric constant is 30-32, the quality factor Qf value is not less than 24000GHz, and the temperature coefficient of resonance frequency tau f is less than or equal to 15ppm / DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave dielectric materials, and in particular, relates to a low-temperature sintered dielectric constant microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] With the rapid development of the Internet of Things, 5G technology and 6G technology, the demand for high-performance microwave devices with a wide range of dielectric constants, low loss, temperature stability, etc. is increasing, and the demand for microwave dielectric ceramic materials that can meet the miniaturization and integration of microwave circuits is also increasing. At present, medium dielectric constant microwave dielectric ceramics are mainly used in military radar and microwave communication fields. The research and development and preparation of medium dielectric constant microwave dielectric ceramics with small temperature coefficient and high quality factor are crucial to promote the development of communication technology.

[0003] Titanate materials have industrial prospects due to their light weight, low cost and good performance. At present, experts and scholars have conducted in-depth research on titanates, among which magnesium titanate materials have received widespread attention due to their good microwave dielectric properties. Whether it is magnesium titanate or magnesium metatitanate, the higher sintering temperature and higher resonant frequency temperature coefficient limit their application. Although the sintering can be reduced and the performance can be improved by adding sintering aids and composite doping, the results are minimal. Therefore, the development of a low-temperature sintered medium dielectric constant microwave dielectric ceramic material has broad application prospects. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a low-temperature sintered medium dielectric constant microwave dielectric ceramic material and a preparation method; the microwave dielectric ceramic material can maintain the following microwave properties under the sintering conditions of 1250-1300°C: the dielectric constant is 30-32, the quality factor Qf value is not less than 24000GHz, and the resonant frequency temperature coefficient τf≤15ppm / °C.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] On the one hand, the present invention provides a low-temperature sintered medium dielectric constant microwave dielectric ceramic material, the composition expression of the microwave dielectric ceramic material is xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions and satisfy the following conditions: x+y=1, and 0.05≤y≤0.15, a=0.5, b=0.5; z is the mass fraction, and is 1 to 10 wt.% relative to the mass of xMgTiO3-yCaTiO3.

[0007] Furthermore, the dielectric constant of the microwave dielectric ceramic material is 30-32, the quality factor Qf value is not less than 24000 GHz, and the resonant frequency temperature coefficient τf≤15 ppm / °C.

[0008] Another aspect of the present invention provides a method for preparing a low-temperature sintered microwave dielectric ceramic material with a medium dielectric constant, comprising the following steps:

[0009] 1) According to the molar fraction of each element in the composition expression xMgTiO3-yCaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature to obtain a synthesized xMgTiO3-yCaTiO3;

[0010] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression aMg2SiO4-bMgSiO3, the weighed materials are fully mixed and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-calcined at a temperature to obtain a synthesized aMg2SiO4-bMgSiO3;

[0011] 3) ball-milling and drying the xMgTiO3-yCaTiO3 obtained in step 1) and the aMg2SiO4-bMgSiO3 obtained in step 2) in proportion, and then pre-calcining by heat preservation to obtain a powder substrate;

[0012] 4) fully ball-milling the powder substrate obtained in step 3), drying, granulating and sieving after ball-milling;

[0013] 5) The granular material screened in step 4) is pressed into shape, and finally debinding and sintering are performed to obtain the microwave dielectric ceramic material.

[0014] Furthermore, the pre-burning temperature in step 1), step 2) and step 3) is 800-1000° C., and the pre-burning time is 2-5 hours.

[0015] Furthermore, in step 4), the particle size D50 of the powder after ball milling is less than 0.7 micrometers.

[0016] Furthermore, the granulation in step 4) is to mix the dried powder with a binder and then prepare micron-sized spherical particles.

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

[0018] Furthermore, in step 5), the granular material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm.

[0019] Furthermore, the debinding process in step 5) is carried out at 600° C. for 2 hours.

[0020] Furthermore, the sintering process in step 5) is performed at 1250-1300° C. for 3-7 hours.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention adds CaTiO3 to magnesium titanate and adds a certain proportion of Mg2SiO4 and MgSiO3 to improve the resonant frequency temperature coefficient of magnesium titanate in a composite doping manner and make it meet the requirement of near-zero adjustable. In addition, the microwave dielectric ceramic material also has the following microwave dielectric properties: εr=31±1, Qf≥24000GHz, and the sintering temperature is reduced to a certain extent.

[0023] The preparation method of the present invention controls the particle size D50 of the powder after ball milling to less than 0.7 microns, increases the surface activity by reducing the material particle size, thereby reducing the sintering temperature, further improving the dielectric properties of the ceramic material, and meeting the development needs of microwave communication technology. DETAILED DESCRIPTION

[0024] The technical solutions in the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] On the one hand, the present invention provides a low-temperature sintered medium dielectric constant microwave dielectric ceramic material, whose composition expression is xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions and satisfy the following conditions: x+y=1, and 0.05≤y≤0.15, a=0.5, b=0.5; z is the mass fraction, and is 1 to 10 wt.% relative to the mass of xMgTiO3-yCaTiO3.

[0026] The microwave dielectric ceramic material has a dielectric constant of 30 to 32, a quality factor Qf value of not less than 24000 GHz, and a resonant frequency temperature coefficient τf≤15 ppm / °C.

[0027] The method for preparing the low temperature sintered medium dielectric constant microwave dielectric ceramic material comprises the following steps:

[0028] 1) According to the molar fraction of each element in the composition expression xMgTiO3-yCaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-burned at a temperature of 800 to 1000° C. for a time of 2 to 5 hours to obtain a synthesized xMgTiO3-yCaTiO3;

[0029] 2) According to the molar fraction of each element in the composition expression aMg2SiO4-bMgSiO3, MgO and SiO2 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-burned at a temperature of 800 to 1000° C. for a time of 2 to 5 hours to obtain a synthesized aMg2SiO4-bMgSiO3;

[0030] 3) ball-milling and drying the xMgTiO3-yCaTiO3 obtained in step 1) and the aMg2SiO4-bMgSiO3 obtained in step 2) in proportion, and then pre-calcining them to obtain a powder substrate; wherein the pre-calcining temperature is 800-1000° C., and the pre-calcining time is 2-5 hours;

[0031] 4) ball-milling the powder substrate obtained in step 3) to obtain a powder particle size D50 less than 0.7 microns after ball milling, drying, granulating, and sieving after ball milling; wherein the granulation is to mix the dried powder with a binder and then prepare micron-sized spherical particles; the binder used in the granulation is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution, or methyl cellulose;

[0032] 5) The sieved granular material in step 4) is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm, and finally the microwave dielectric ceramic material is obtained by debinding and sintering; wherein the debinding process is to keep the temperature at 600°C for 2 hours, and the sintering process is to sinter at 1250-1300°C for 3-7 hours.

[0033] The dielectric constant microwave dielectric ceramic material can be applied to microwave components.

[0034] Example 1

[0035] The low-temperature sintered medium dielectric constant microwave dielectric ceramic material of Example 1 has a composition expression of xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions, x=0.90, y=0.10, a=0.5, and b=0.5; the mass fraction z of 0.5Mg2SiO4-0.5MgSiO3 relative to the mass of 0.9MgTiO3-0.1CaTiO3 is 8wt.%.

[0036] The method for preparing the low temperature sintered medium dielectric constant microwave dielectric ceramic material comprises the following steps:

[0037] 1) According to the molar fraction of each element in the composition expression 0.9MgTiO3-0.1CaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature of 800° C. for 5 hours to obtain synthesized 0.9MgTiO3-0.1CaTiO3;

[0038] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression 0.5Mg2SiO4-0.5MgSiO3, the weighed materials are fully mixed and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-fired at a temperature of 800° C. for 5 hours to obtain synthesized 0.5Mg2SiO4-0.5MgSiO3;

[0039] 3) ball-milling and drying the 0.9MgTiO3-0.1CaTiO3 obtained in step 1) and the 0.5Mg2SiO4-0.5MgSiO3 obtained in step 2) in proportion, and then pre-calcining them at a temperature of 800° C. for 5 hours to obtain a powder substrate;

[0040] 4) The powder substrate obtained in step 3) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.479 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then make micron-sized spherical particles;

[0041] 5) The sieved granules in step 4) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and are first sintered at 600° C. for 2 h to remove binder, and then sintered at 1250° C. for 7 h to obtain the microwave dielectric ceramic material.

[0042] Example 2

[0043] The low-temperature sintered medium dielectric constant microwave dielectric ceramic material of Example 2 has a composition expression of xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions, x=0.92, y=0.08, a=0.5, and b=0.5; the mass fraction z of 0.5Mg2SiO4-0.5MgSiO3 relative to the mass of 0.92MgTiO3-0.08CaTiO3 is 6wt.%.

[0044] The method for preparing the low temperature sintered medium dielectric constant microwave dielectric ceramic material comprises the following steps:

[0045] 1) According to the molar fraction of each element in the composition expression 0.92MgTiO3-0.08CaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature of 830° C. for 4 hours to obtain synthesized 0.92MgTiO3-0.08CaTiO3;

[0046] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression 0.5Mg2SiO4-0.5MgSiO3, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-fired at a temperature of 850° C. for 4 hours to obtain synthesized 0.5Mg2SiO4-0.5MgSiO3;

[0047] 3) ball-milling and drying the 0.92MgTiO3-0.08CaTiO3 obtained in step 1) and the 0.5Mg2SiO4-0.5MgSiO3 obtained in step 2) in proportion, and then pre-calcining them at a temperature of 850° C. for 4 hours to obtain a powder substrate;

[0048] 4) The powder substrate obtained in step 3) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.468 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then make micron-sized spherical particles;

[0049] 5) The sieved granules in step 4) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and are first sintered at 600° C. for 2 h to remove binder, and then sintered at 1250° C. for 6 h to obtain the microwave dielectric ceramic material.

[0050] Example 3

[0051] The low-temperature sintered medium dielectric constant microwave dielectric ceramic material of Example 3 has a composition expression of xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions, x=0.95, y=0.05, a=0.5, and b=0.5; the mass fraction z of 0.5Mg2SiO4-0.5MgSiO3 relative to the mass of 0.95MgTiO3-0.05CaTiO3 is 4wt.%.

[0052] The method for preparing the low temperature sintered medium dielectric constant microwave dielectric ceramic material comprises the following steps:

[0053] 1) According to the molar fraction of each element in the composition expression 0.95MgTiO3-0.05CaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature of 850° C. for 3 hours to obtain synthesized 0.95MgTiO3-0.05CaTiO3;

[0054] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression 0.5Mg2SiO4-0.5MgSiO3, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-fired at a temperature of 850° C. for 3 hours to obtain synthesized 0.5Mg2SiO4-0.5MgSiO3;

[0055] 3) ball-milling and drying the 0.95MgTiO3-0.05CaTiO3 obtained in step 1) and the 0.5Mg2SiO4-0.5MgSiO3 obtained in step 2) in proportion, and then pre-calcining them at a temperature of 850° C. for 3 hours to obtain a powder substrate;

[0056] 4) The powder substrate obtained in step 3) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.581 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then make micron-sized spherical particles;

[0057] 5) The sieved granules in step 4) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and are first sintered at 600° C. for 2 h to remove binder, and then sintered at 1270° C. for 5 h to obtain the microwave dielectric ceramic material.

[0058] Example 4

[0059] The low-temperature sintered medium dielectric constant microwave dielectric ceramic material of Example 4 has a composition expression of xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions, x=0.86, y=0.14, a=0.5, b=0.5; the mass fraction z of 0.5Mg2SiO4-0.5MgSiO3 relative to the mass of 0.86MgTiO3-0.14CaTiO3 is 2wt.%.

[0060] The method for preparing the low temperature sintered medium dielectric constant microwave dielectric ceramic material comprises the following steps:

[0061] 1) According to the molar fraction of each element in the composition expression 0.86MgTiO3-0.14CaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature of 850° C. for 3 hours to obtain a synthesized 0.95MgTiO3-0.05CaTiO3;

[0062] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression 0.5Mg2SiO4-0.5MgSiO3, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-fired at a temperature of 850° C. for 3 hours to obtain synthesized 0.5Mg2SiO4-0.5MgSiO3;

[0063] 3) ball-milling and drying the 0.86MgTiO3-0.14CaTiO3 obtained in step 1) and the 0.5Mg2SiO4-0.5MgSiO3 obtained in step 2) in proportion, and then pre-calcining the mixture at a temperature of 850° C. for 3 h to obtain a powder substrate;

[0064] 4) The powder substrate obtained in step 3) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.593 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then make micron-sized spherical particles;

[0065] 5) The sieved granules in step 4) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and are first sintered at 600° C. for 2 h to remove binder, and then sintered at 1300° C. for 4.5 h to obtain the microwave dielectric ceramic material.

[0066] Comparative Example 1

[0067] The microwave dielectric ceramic material of comparative example 1 has a composition expression of xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions, x=1, y=0, a=0.5, and b=0.5; the mass fraction z of 0.5Mg2SiO4-0.5MgSiO3 relative to the mass of MgTiO3 is 1wt.%.

[0068] The method for preparing the microwave dielectric ceramic material comprises the following steps:

[0069] 1) The weighed materials MgO and TiO2 are mixed fully and then ball-milled. After ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-calcined at a temperature of 870° C. for 2.5 hours to obtain MgTiO3;

[0070] 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression 0.5Mg2SiO4-0.5MgSiO3, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-fired at a temperature of 850° C. for 3 hours to obtain synthesized 0.5Mg2SiO4-0.5MgSiO3;

[0071] 3) ball-milling the MgTiO3 obtained in step 1) and the 0.5Mg2SiO4-0.5MgSiO3 obtained in step 2) in proportion, drying, and pre-calcining them at a temperature of 850° C. for 3 h to obtain a powder substrate;

[0072] 4) The powder substrate obtained in step 3) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.662 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then make micron-sized spherical particles;

[0073] 5) The sieved granules in step 4) are pressed into cylinders with a diameter of 10 mm and a height of 6 mm, and are first sintered at 600° C. for 2 h to remove binder, and then sintered at 1330° C. for 4.5 h to obtain the microwave dielectric ceramic material.

[0074] Comparative Example 2

[0075] The composition expression of the microwave dielectric ceramic material of Comparative Example 2 is xMgTiO3-yCaTiO3, wherein x and y are molar fractions, x=0.95, y=0.05.

[0076] The method for preparing the microwave dielectric ceramic material comprises the following steps:

[0077] 1) According to the molar fraction of each element in the composition expression 0.95MgTiO3-0.05CaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-burned at a temperature of 900° C. for 2 hours to obtain a 0.95MgTiO3-0.05CaTiO3 powder substrate;

[0078] 2) The powder substrate obtained in step 1) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.735 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then prepare micron-sized spherical particles;

[0079] 3) The sieved granular material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm, and is first sintered at a temperature of 600° C. for 2 h to remove the binder, and then sintered at 1350° C. for 3 h to obtain the microwave dielectric ceramic material.

[0080] Comparative Example 3

[0081] The composition expression of the microwave dielectric ceramic material of Comparative Example 3 is MgTiO3.

[0082] The method for preparing the microwave dielectric ceramic material comprises the following steps:

[0083] 1) The weighed materials MgO and TiO2 are mixed fully and then ball-milled. After ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-calcined at a temperature of 850° C. for 3 hours to obtain a MgTiO3 powder substrate;

[0084] 2) The powder substrate obtained in step 1) is fully ball-milled, and the particle size D50 of the powder after ball milling is 0.719 microns. After ball milling, the powder is dried, granulated, and sieved; wherein the granulation is to mix the dried powder with a binder and then prepare micron-sized spherical particles;

[0085] 3) The sieved granular material is pressed into a cylinder with a diameter of 10 mm and a height of 6 mm, first sintered at 600° C. for 2 h to remove binder, and then sintered at 1320° C. for 3.5 h to obtain the microwave dielectric ceramic material.

[0086] Performance Testing

[0087] The microwave dielectric properties of the microwave dielectric ceramic material tested using a microwave network analyzer are shown in Table 1.

[0088] Table 1 Parameter values ​​of the embodiments and comparative examples and microwave dielectric properties of microwave dielectric ceramics

[0089]

[0090] It can be seen from Table 1 that, compared with Comparative Examples 1-3, the microwave dielectric ceramic materials prepared in Examples 1-4 can maintain the following microwave dielectric properties at 1250-1300°C: ε r =31±1, Qf>24000GHz, resonant frequency temperature coefficient τ fThe absolute value is less than 15ppm / ℃. The present invention is a low-temperature sintered medium dielectric constant microwave dielectric ceramic. By comparing the embodiment with the comparative example, it can also be found that reducing the particle size of the prepared powder can effectively reduce the sintering temperature, and the prepared ceramic material has a small grain size, which is beneficial to reduce dielectric loss and increase the service life of microwave components. The microwave dielectric ceramic prepared by the present invention has a wide sintering temperature, a high quality factor, good temperature stability and an appropriate dielectric constant, and has broad application prospects in the field of microwave devices.

[0091] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any modifications or equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A low temperature sintered medium dielectric constant microwave dielectric ceramic material, characterized in that: The composition expression of the microwave dielectric ceramic material is xMgTiO3-yCaTiO3-z(aMg2SiO4-bMgSiO3), wherein x, y, a, and b are all molar fractions and satisfy the following conditions: x+y=1, and 0.05≤y≤0.15, a=0.5, b=0.5; z is the mass fraction, and is 1 to 10 wt.% relative to the mass of xMgTiO3-yCaTiO3.

2. The low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 1, characterized in that: The microwave dielectric ceramic material has a dielectric constant of 30 to 32, a quality factor Qf value of not less than 24000 GHz, and a resonant frequency temperature coefficient τf≤15 ppm / °C.

3. A method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 1 or 2, characterized in that: The steps include: 1) According to the molar fraction of each element in the composition expression xMgTiO3-yCaTiO3, MgO, TiO2 and CaCO3 are weighed respectively, the weighed materials are mixed thoroughly and then ball-milled, and after ball-milling, they are dried, sieved and put into a corundum crucible, and then pre-calcined at a temperature to obtain a synthesized xMgTiO3-yCaTiO3; 2) MgO and SiO2 are weighed respectively according to the molar fraction of each element in the composition expression aMg2SiO4-bMgSiO3, the weighed materials are fully mixed and then ball-milled, and after ball-milling, they are dried, sieved, put into a corundum crucible, and then pre-calcined at a temperature to obtain a synthesized aMg2SiO4-bMgSiO3; 3) ball-milling and drying the xMgTiO3-yCaTiO3 obtained in step 1) and the aMg2SiO4-bMgSiO3 obtained in step 2) in proportion, and then pre-calcining by heat preservation to obtain a powder substrate; 4) fully ball-milling the powder substrate obtained in step 3), drying, granulating and sieving after ball-milling; 5) The granular material screened in step 4) is pressed into shape, and finally debinding and sintering are performed to obtain the microwave dielectric ceramic material.

4. The method for preparing a low-temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: The pre-burning temperature in step 1), step 2) and step 3) is 800-1000° C., and the pre-burning time is 2-5 hours.

5. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: In step 4), the particle size D50 of the powder after ball milling is less than 0.7 micrometer.

6. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: The granulation in step 4) is to mix the dried powder with a binder and then make micron-sized spherical particles.

7. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 6, characterized in that: The binder used for granulation is selected from at least one of polyvinyl alcohol solution, polyvinyl butyral solution, acrylic acid solution or methyl cellulose.

8. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: In step 5), the granules are pressed into cylinders with a diameter of 10 mm and a height of 6 mm.

9. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: The debinding process in step 5) is carried out at 600°C for 2 hours.

10. The method for preparing a low temperature sintered medium dielectric constant microwave dielectric ceramic material according to claim 3, characterized in that: The sintering process in step 5) is sintering at 1250-1300° C. for 3-7 hours.

Images