An ultra-low dielectric constant microwave dielectric ceramic and a preparation method thereof

Abstract

The application relates to the field of electronic information functional ceramics and electronic devices, and discloses a kind of ultra-low dielectric constant microwave dielectric ceramic and preparation method thereof, the composition expression of the ultra-low dielectric constant microwave dielectric ceramic is: xMg2SiO4-(1-x)LiAl 0.925 B 0.075 O2+ywt.%MO, MO is sintering aid, wherein: 0.2<=x<=0.4, 0.5<=y<=1, the sintering temperature of the ultra-low dielectric constant microwave dielectric ceramic is 1000~1100 DEG C, the dielectric constant of the microwave dielectric ceramic prepared by the application can reach 4.9~5.8, Qxf value can reach 51539~60754 GHz, frequency temperature coefficient Tf can reach-16.2~-11.3ppm / DEG C, the ultra-low dielectric constant microwave dielectric ceramic can be prepared at lower sintering temperature, meanwhile Qxf value is high, better microwave dielectric performance can be obtained, and the resonant frequency temperature coefficient is low, and temperature stability is good.

Description

Technical Field

[0001] This invention belongs to the field of electronic information functional ceramics and electronic devices, specifically relating to an ultra-low dielectric constant microwave dielectric ceramic and its preparation method. Background Technology

[0002] Microwave dielectric ceramics are a new type of functional ceramic that has rapidly developed in recent years with the application of microwave technology. They are used as dielectric materials in microwave frequency circuits to perform one or more functions such as conduction, resonance, and filtering. With the rapid development of modern communication technology, microwave dielectric ceramics, as important electronic components, have a significant impact on the operating frequency, signal transmission efficiency, stability, and reliability of communication equipment. Because low-αr dielectric materials can suppress signal delay time and reduce cross-coupling losses in high-speed signal transmission, they are of great significance for future high-frequency network communication applications.

[0003] Microwave dielectric ceramics possess the basic properties of dielectric materials, typically measured by three main performance parameters: dielectric constant (ɛr), quality factor (Q×f), and temperature coefficient of resonant frequency (τf). To meet the requirements of high-frequency, miniaturized, and integrated microwave communication components, microwave dielectric ceramics need to have low dielectric constants, high quality factors, and near-zero temperature coefficient of resonant frequency. In practical applications, a low dielectric constant effectively avoids signal delay and ensures high transmission rates; a high quality factor (Q×f ≥ 5000 GHz) increases frequency selectivity and device reliability; and a near-zero temperature coefficient of resonant frequency (τf) ensures frequency stability with temperature variations. However, most materials cannot simultaneously meet all these requirements. For example, materials with excellent quality factors may have large temperature coefficients of resonant frequency, such as the existing Mn... 2+ For LiZnPO4 doped with sintered at 825℃, εr = 5.57, Q×f = 77900 GHz, and τf = -80.54×10⁻⁶. -6 Although the dielectric constant is low and the Q×f is high, the τf is also high, which is not conducive to the stability of the device. Therefore, further research is needed to obtain microwave dielectric ceramics with excellent comprehensive performance. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide an ultra-low dielectric constant microwave dielectric ceramic and its preparation method, which can realize the preparation of ultra-low dielectric constant microwave dielectric ceramic at a relatively low sintering temperature, while having a high Q×f value, thus obtaining better microwave dielectric properties, and having a low resonant frequency temperature coefficient and good temperature stability.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] An ultra-low dielectric constant microwave dielectric ceramic, wherein the compositional expression of the ultra-low dielectric constant microwave dielectric ceramic is: xMg2SiO4-(1-x)LiAl 0.925 B 0.075 O2+ywt.%MO, where MO is a sintering aid, wherein: 0.2≤x≤0.4, 0.5≤y≤1, and the sintering temperature of the ultra-low dielectric constant microwave dielectric ceramic is 1000~1100℃.

[0007] Preferably, the ultra-low dielectric constant microwave dielectric ceramic has a dielectric constant of 4.9~5.8, a Q×f value of 51539~60754GHz, and a frequency temperature coefficient τf of -16.2~-11.3ppm / ℃.

[0008] Preferably, when x=0.22 and the sintering temperature is 1280℃, the dielectric constant of the ultra-low dielectric constant microwave dielectric ceramic is 4.9, the Q×f value is 60754GHz, and the frequency temperature coefficient τf is -11.3ppm / ℃.

[0009] Preferably, the sintering aid is one or a mixture of several of B2O3, CuO, and ZnO.

[0010] A method for preparing ultra-low dielectric constant microwave dielectric ceramics includes the following steps:

[0011] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0012] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and pulverized and then dried to obtain dried powder of A1 and dried powder of A2.

[0013] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles and calcined at high temperature in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2;

[0014] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2 is given. Based on the value of x, the synthetic material A1 and synthetic material A2 are weighed separately, and then 0.5~1wt.% sintering aid is added to obtain the mixture B.

[0015] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar, using zirconium balls and deionized water as the grinding media;

[0016] (6) Pulping and granulation: Add 2-4w% of the binder by weight of mixture B to the slurry obtained in step (5), and then perform spray granulation;

[0017] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in an air atmosphere.

[0018] Preferably, the ball milling media in step (2) are zirconium balls and deionized water; after ball milling, the balls are placed in an oven at 120°C for drying.

[0019] Preferably, in step (3), the pre-firing temperature of A1 dry powder is 1150~1250℃ and the pre-firing time is 2~4h; the pre-firing temperature of A2 dry powder is 650~750℃ and the pre-firing time is 1~2h.

[0020] Preferably, in step (5), the mass ratio of zirconium balls, mixture B, and deionized water is 10:1:3; the ball milling speed is 200 r / min; and the ball milling time is 24 h.

[0021] Preferably, the adhesive in step (6) is a 5% (w / w) aqueous solution of polyvinyl alcohol.

[0022] Preferably, the sintering temperature in step (7) is 1000~1100℃ and the sintering time is 2~3h.

[0023] The beneficial effects of this invention are:

[0024] This invention utilizes magnesium oxide, silicon dioxide, lithium carbonate, aluminum oxide, and lithium metaborate as raw materials to prepare a compound with the formula xMg2SiO4-(1-x)LiAl. 0.925 B 0.075 O2 microwave dielectric ceramics, B 3+ Replace Al 3+ It can reduce the dielectric constant of microwave dielectric ceramics and improve their sintering properties, when B 3+ When the doping amount is 0.075 mol%, its dielectric constant can reach 4.9~5.8, the Q×f value can reach 51539~60754 GHz, and the frequency temperature coefficient τf can reach -16.2~-11.3 ppm / ℃. It can realize the preparation of microwave dielectric ceramics with ultra-low dielectric constant at a relatively low sintering temperature. At the same time, the high Q×f value can obtain good microwave dielectric properties, and the resonant frequency temperature coefficient is low and the temperature stability is good. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0027] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0028] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0029] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0030] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.2, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0031] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0032] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0033] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1000℃ for 3 hours.

[0034] Example 2: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0035] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0036] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0037] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0038] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.22, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0039] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0040] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0041] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1050℃ for 3 hours.

[0042] Example 3: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0043] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0044] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0045] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0046] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.25, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0047] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0048] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0049] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1100℃ for 3 hours.

[0050] Example 4: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0051] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0052] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0053] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0054] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.3, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0055] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0056] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0057] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1050℃ for 3 hours.

[0058] Example 5: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0059] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0060] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0061] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0062] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925B 0.075 The composition expression of O2, when x is 0.4, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0063] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0064] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0065] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1050℃ for 3 hours.

[0066] Example 6: A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0067] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0068] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0069] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0070] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.22, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0071] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0072] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0073] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1000℃ for 3 hours.

[0074] Example 7 A method for preparing an ultra-low dielectric constant microwave dielectric ceramic, comprising the following steps:

[0075] (1) Ingredients: Weigh magnesium oxide and silicon dioxide according to the composition formula of Mg2SiO4 and mix them evenly to obtain mixture A1; according to LiAl 0.925 B 0.075 The composition formula of O2 is obtained by weighing lithium carbonate, aluminum oxide and lithium metaborate and mixing them evenly.

[0076] (2) Mixing: The obtained mixtures A1 and A2 are ball-milled and dried. The ball milling media are zirconium balls and deionized water. After ball milling, they are placed in an oven at 120°C for drying to obtain dried powder of A1 and dried powder of A2.

[0077] (3) Pre-calcination: The obtained dry powder A1 and dry powder A2 are placed in alumina crucibles respectively. The dry powder A1 is calcined at 1200℃ for 3 hours in a pre-calcination furnace, and the dry powder A2 is calcined at 700℃ for 2 hours in a pre-calcination furnace to obtain synthetic material A1 and synthetic material A2.

[0078] (4) Secondary batching: according to xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2, when x is 0.22, weigh out synthetic material A1 and synthetic material A2, and then add 1 wt.% B2O3 to obtain mixture B;

[0079] (5) Mixing and grinding: Mixing and grinding the mixture B in a ball mill jar. The ball milling media are zirconium balls and deionized water. The mass ratio of zirconium balls, mixture B and deionized water is 10:1:3. The ball milling speed is 200 r / min and the ball milling time is 24 h.

[0080] (6) Pulping and granulation: Add a 5% polyvinyl alcohol aqueous solution, accounting for 2w% of the weight of mixture B, to the slurry obtained in step (5), and then perform spray granulation;

[0081] (7) Molding and sintering: The granulated powder obtained in step (6) is pressed into shape and then sintered in air atmosphere at a temperature of 1100℃ for 3 hours.

[0082] Performance testing

[0083] The microwave dielectric ceramics prepared in Examples 1-7 were subjected to performance testing: the bulk density of the ceramic samples was determined using the Archimedes displacement method; the dielectric constant (ɛr), quality factor (Q×f), and temperature coefficient of resonant frequency (τf) of the samples were tested using a microwave network analyzer; the resonant frequency f(T) at temperature T was measured, and the temperature coefficient of resonant frequency was calculated using the formula: τf = (f T2 -f T1 ) / [f T2 ×(T2-T1)], where T2 is 85℃ and T1 is 25℃, and the data results are shown in Table 1.

[0084] Table 1 Sample performance test results

[0085]

[0086] As can be seen from the data in Table 1, Examples 1-7 of the present invention can prepare microwave dielectric ceramics with ultra-low dielectric constant at a relatively low sintering temperature. At the same time, the Q×f value is high, which can obtain better microwave dielectric properties. Furthermore, the resonant frequency temperature coefficient is low, and the temperature stability is good, which can better meet the usage requirements of microwave communication components.

[0087] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An ultra-low dielectric constant microwave dielectric ceramic, characterized by, The composition expression of the ultra-low dielectric constant microwave dielectric ceramic is: xMg2SiO4-(1-x)LiAl 0.925 B 0.075 O2+ywt.%MO, MO is a sintering aid, wherein: 0.2≤x≤0.4, 0.5≤y≤1, and the sintering temperature of the ultra-low dielectric constant microwave dielectric ceramic is 1000~1100℃.

2. The ultra-low dielectric constant microwave dielectric ceramic of claim 1, wherein, The dielectric constant of the ultra-low dielectric constant microwave dielectric ceramic is 4.9-5.8, the Qxf value is 51539-60754 GHz, and the frequency temperature coefficient τf is -16.2--11.3 ppm / ℃.

3. The ultra-low dielectric constant microwave dielectric ceramic of claim 1, wherein, When x=0.22 and the sintering temperature is 1050℃, the dielectric constant of the ultra-low dielectric constant microwave dielectric ceramic is 4.9, the Qxf value is 60754 GHz, and the frequency temperature coefficient τf is -11.3 ppm / ℃.

4. The ultra-low dielectric constant microwave dielectric ceramic of claim 1, wherein, The sintering aid is one or a mixture of several of B2O3, CuO and ZnO.

5. A method for producing the ultra-low dielectric constant microwave dielectric ceramic according to any one of claims 1 to 4, characterized by, The method comprises the following steps: (1)Batching: magnesium oxide and silicon dioxide were weighed according to the composition expression of Mg2SiO4 and mixed uniformly to obtain a mixed material A1; lithium carbonate, aluminum oxide and lithium metaborate were weighed according to the composition expression of LiAlO2 and mixed uniformly to obtain a mixed material A2; 0.925 B 0.075 O2 of the composition expression of LiAlO2 and mixed uniformly to obtain a mixed material A2; (2) mixing: the obtained mixture A1 and A2 are respectively subjected to ball milling, powder crushing treatment and drying to obtain A1 dry powder and A2 dry powder; (3) pre-sintering: the obtained A1 dry powder and A2 dry powder are respectively placed in an alumina crucible and subjected to high-temperature calcination in a pre-sintering furnace to obtain synthesis material A1 and synthesis material A2; (4) Secondary batching: according to the composition expression of xMg2SiO4-(1-x)LiAl 0.925 B 0.075 The composition expression of O2 is taken according to the value of x, and the synthetic material A1 and the synthetic material A2 are taken respectively, and then 0.5-1 wt.% sintering aids are added to obtain the mixed material B; (5) mixing and crushing: the mixture B is mixed and crushed in a ball mill tank, and the ball milling medium is zirconium ball and deionized water; (6) slurry preparation and granulation: 2-4w% of a binder based on the weight of the mixture B is added to the slurry obtained in step (5), and then spray granulation is performed; (7) forming and sintering: the granulated powder obtained in step (6) is subjected to compression molding, and finally sintering is performed in an air atmosphere.

6. The method of claim 5, wherein the microwave dielectric ceramic has a dielectric constant of 2.2 or less. In step (2), the ball milling medium is zirconium ball and deionized water; after ball milling, drying treatment is performed in a 120℃ oven.

7. The method of claim 5, wherein the microwave dielectric ceramic has a dielectric constant of 2.5 or less. In step (3), the pre-sintering temperature of the A1 dry powder is 1150-1250℃, and the pre-sintering time is 2-4h; the pre-sintering temperature of the A2 dry powder is 650-750℃, and the pre-sintering time is 1-2h.

8. The method of claim 5, wherein the microwave dielectric ceramic has a dielectric constant of 2.2 or less. In step (5), the mass ratio of zirconium ball, mixture B and deionized water is 10:1:3; the ball milling speed is 200r / min; and the ball milling time is 24h.

9. The method of claim 5, wherein the microwave dielectric ceramic has a dielectric constant of 2.2 or less. In step (6), the binder is a polyvinyl alcohol aqueous solution with a mass concentration of 5%.

10. The method of claim 5, wherein the microwave dielectric ceramic has a dielectric constant of 2.5 or less. In step (7), the sintering temperature is 1000-1100℃, and the sintering time is 2-3h.

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