CN110372370B - Microwave dielectric ceramic and preparation method thereof - Google Patents
Microwave dielectric ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention provides a microwave dielectric ceramic and a preparation method thereof, wherein the microwave dielectric ceramic has a general formula shown as the following formula: (1-x) Ca2Sm4Ti5O18‑xSmAlO3(ii) a Wherein x is 0.05-0.25. Compared with the prior art, the microwave dielectric ceramic provided by the invention takes the composite oxide with the specific general formula as a main material, and SmAlO is adjusted3The content of (A) can realize that the dielectric constant is about 45 and the frequency temperature coefficient is continuously adjustable; in addition, the microwave dielectric ceramic has stable structure, specific dielectric constant and high Q multiplied by f value, and the temperature coefficient of the resonant frequency is continuously adjustable. Experimental results show that the dielectric constant of the microwave dielectric ceramic is between 40 and 46.1, the Q x f is more than 30000GHz and can reach 49700GHz, and compared with other microwave dielectric ceramics with the same dielectric constant, the Q x f value of the system is high, and the dielectric loss is low; meanwhile, the temperature coefficient of the resonance frequency is continuously adjustable between-7.4 PPM/DEG C to +6.7 PPM/DEG C, and the method is suitable for large-scale commercial use.
Description
Technical Field
The invention relates to the technical field of microwave dielectric ceramics, in particular to a microwave dielectric ceramic and a preparation method thereof.
Background
The upcoming fifth generation wireless networks and technologies (5G) have a major leap in data transfer speed, capacity, and data transfer delay compared to the fourth generation (4G) networks. 5G brings a series of new technologies, and public and personal business standards can be reestablished in the fields of virtual reality, unmanned driving, smart cities, all-thing interconnection and the like. Sub-6 and millimeter waves are the main choices for deploying 5G networks worldwide. Sub-6 is concerned with improving the propagation range and providing the same coverage and performance with a smaller number of base stations, and a microwave dielectric ceramic material with a dielectric constant of about 45 is urgently needed for the frequency band dielectric waveguide filter. Many (1-x) CaTiO compounds with dielectric constants of about 45 are studied3-xLaAlO3The sintering temperature of the system is higher than 1500 ℃, the energy consumption is large, and the equipment loss is large, which limits the application of the system to a certain extent.
Disclosure of Invention
In view of the above, the present invention provides a microwave dielectric ceramic and a preparation method thereof, wherein the microwave dielectric ceramic has a dielectric constant of about 45, a high Q × f value, a low dielectric loss, and a continuously adjustable temperature coefficient of resonant frequency.
The invention provides a microwave dielectric ceramic, which has a general formula shown in a formula (I):
(1-x)Ca2Sm4Ti5O18-xSmAlO3formula (I);
in the formula (I), x is 0.05-0.25.
Preferably, the method further comprises the following steps:
an additive;
the additive is prepared from the following components in percentage by mass (40-55): (10-30): (15-30): (2-10): (1-10) SiO2、Al2O3、CaO、Y2O3And MgO.
Preferably, the preparation method of the additive specifically comprises the following steps:
mixing SiO2、Al2O3、CaO、Y2O3Mixing with MgO, ball milling, melting at 1400-1600 deg.c for 10-30 min, separating, crushing and sieving to obtain the additive.
The invention also provides a preparation method of the microwave dielectric ceramic, which comprises the following steps:
a) mixing CaCO3、Sm2O3、TiO2And Al2O3After mixing, carrying out primary grinding treatment, and then carrying out presintering to obtain a presintering material; then, carrying out secondary grinding treatment on the obtained pre-sintering material to obtain powder;
b) adding an adhesive into the powder obtained in the step a) for granulation forming to obtain a ceramic green body; and sintering the obtained ceramic green body to obtain the microwave dielectric ceramic.
Preferably, the first grinding treatment in step a) specifically comprises the following steps:
mixing the mixed raw materials, zirconium balls and water in a proportion of 1: (3-4): (2-3), ball-milling for 3-5 h at the rotating speed of 200-300 r/min, and drying at 80-150 ℃ to obtain the mixed material after the first grinding treatment.
Preferably, the temperature of the pre-sintering in the step a) is 900-1100 ℃, the heating rate is 3-8 ℃/min, and the heat preservation time is 3-4 h.
Preferably, the adhesive in the step b) is a polyvinyl alcohol aqueous solution with the mass percentage of 4% -8%;
the mass ratio of the powder to the adhesive is 100: (15-25).
Preferably, the granulation molding process in the step b) specifically comprises the following steps:
adding an adhesive into the microwave dielectric ceramic powder, granulating and grinding for 0.5-1.5 h, sieving with a 70-90 mesh sieve, and pressing and molding the obtained powder under the pressure of 80-120 MPa to obtain the ceramic green body.
Preferably, the sintering temperature in the step b) is 1100-1450 ℃, the heating rate is 3-8 ℃/min, and the heat preservation time is 2-4 h.
Preferably, the step a) further comprises:
and mixing the obtained pre-sintered material with an additive, and then carrying out secondary grinding treatment to obtain powder.
The invention provides a microwave dielectric ceramic and a preparation method thereof, wherein the microwave dielectric ceramic has a general formula shown as the following formula: (1-x) Ca2Sm4Ti5O18-xSmAlO3(ii) a Wherein x is 0.05-0.25. Compared with the prior art, the microwave dielectric ceramic provided by the invention takes the composite oxide with the specific general formula as a main material, and SmAlO is adjusted3The content of (A) can realize that the dielectric constant is about 45 and the frequency temperature coefficient is continuously adjustable; in addition, the microwave dielectric ceramic has stable structure, specific dielectric constant and high Q multiplied by f value, and the temperature coefficient of the resonant frequency is continuously adjustable. Experimental results show that the dielectric constant of the microwave dielectric ceramic is between 40 and 46.1, Qxf is more than 30000GHz and can reach 49700GHz, and compared with the microwave dielectric ceramic with the same dielectric constantThe other system is microwave dielectric ceramic, the system has high Q multiplied by f value and low dielectric loss; meanwhile, the temperature coefficient of the resonance frequency is continuously adjustable between-7.4 PPM/DEG C to +6.7 PPM/DEG C, and the method is suitable for large-scale commercial use.
In addition, the preparation method provided by the invention has the advantages of simple process, low sintering temperature, low cost, no toxicity, no environmental pollution, suitability for large-scale industrialization and wide development prospect, and meets the requirement of environmental protection.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a microwave dielectric ceramic, which has a general formula shown in a formula (I):
(1-x)Ca2Sm4Ti5O18-xSmAlO3formula (I);
in the formula (I), x is 0.05-0.25.
In the invention, x is 0.05-0.25, preferably 0.15; in a preferred embodiment of the present invention, the values of x are 0.05, 0.1, 0.2, and 0.25, respectively.
In the invention, the microwave dielectric ceramic takes the composite oxide with the specific general formula as a main material, and SmAlO is adjusted3The content of (A) can realize that the dielectric constant is about 45 and the frequency temperature coefficient is continuously adjustable; in addition, the microwave dielectric ceramic has stable structure, specific dielectric constant and high Q multiplied by f value, and the temperature coefficient of the resonant frequency is continuously adjustable.
In the present invention, the microwave dielectric ceramic preferably further comprises:
and (3) an additive.
In the invention, the additive is preferably prepared from the following components in a mass ratio of (40-55): (10-30): (15-30): (2-10): (1-10) SiO2、Al2O3、CaO、Y2O3And MgO, more preferably a mixture of MgO and MgO in a mass ratio of 50: 15: 25: 5: 5 SiO2、Al2O3、CaO、Y2O3And MgO.
In the present invention, the preparation method of the additive is preferably specifically:
mixing SiO2、Al2O3、CaO、Y2O3Mixing with MgO, ball milling, melting at 1400-1600 deg.c for 10-30 min, separating, crushing and sieving to obtain additive;
more preferably:
mixing SiO2、Al2O3、CaO、Y2O3Mixing with MgO, ball milling, drying, sieving, melting at 1500 deg.C for 20min, separating, crushing, and sieving to obtain the additive.
The ball milling equipment is not particularly limited in the present invention, and a ball mill known to those skilled in the art may be used. In the present invention, the time for the ball milling is preferably 20 to 30 hours, and more preferably 24 hours. In the present invention, the separation is preferably performed by extraction with water, and the present invention is not particularly limited thereto. The process of the present invention is not particularly limited, and the crushing method known to those skilled in the art may be used. In the present invention, the size of the mesh of the screen is preferably 150 to 250 mesh, and more preferably 200 mesh. By adopting the preparation method, the refined additive can be obtained, and the subsequent use is convenient.
In the present invention, the amount of the additive is preferably not more than 1.5%, more preferably 0.5% to 1%, of the mass of the microwave dielectric ceramic.
In the invention, the additive can reduce the sintering temperature, inhibit titanium reduction and improve the Q multiplied by f value.
The invention also provides a preparation method of the microwave dielectric ceramic, which comprises the following steps:
a) mixing CaCO3、Sm2O3、TiO2And Al2O3After mixing, carrying out primary grinding treatment, and then carrying out presintering to obtain a presintering material; then, carrying out secondary grinding treatment on the obtained pre-sintering material to obtain powder;
b) adding an adhesive into the powder obtained in the step a) for granulation forming to obtain a ceramic green body; and sintering the obtained ceramic green body to obtain the microwave dielectric ceramic.
The invention first prepares CaCO3、Sm2O3、TiO2And Al2O3After mixing, carrying out primary grinding treatment, and then carrying out presintering to obtain a presintering material; and then, carrying out secondary grinding treatment on the obtained pre-sintering material to obtain powder. CaCO of the invention3、Sm2O3、TiO2And Al2O3The source of (A) is not particularly limited, and commercially available products known to those skilled in the art may be used. In the present invention, the CaCO3、Sm2O3、TiO2And Al2O3The amount of (A) is calculated according to the stoichiometric ratio in the general formula shown in formula (I).
In the present invention, the first grinding process preferably includes:
mixing the mixed raw materials, zirconium balls and water in a proportion of 1: (3-4): (2-3), ball-milling for 3-5 h at the rotating speed of 200-300 r/min, and drying at 80-150 ℃ to obtain a mixed material after primary grinding treatment;
more preferably:
mixing the mixed raw materials, zirconium balls and water in a proportion of 1: 3: 2, ball milling for 4 hours at the rotating speed of 250r/min, and then drying at 120 ℃ to obtain a mixed material after the first grinding treatment.
The ball milling equipment is not particularly limited in the present invention, and a planetary ball mill well known to those skilled in the art may be used.
After the mixed material after the first grinding treatment is obtained, the obtained mixed material after the first grinding treatment is presintered to obtain a presintered material. In the invention, the pre-sintering temperature is preferably 900-1100 ℃, and more preferably 1000-1050 ℃; the temperature rise rate of the pre-sintering is preferably 3 ℃/min to 8 ℃/min, and more preferably 3 ℃/min; the heat preservation time of the pre-sintering is preferably 3 to 4 hours, and more preferably 3 hours.
After the pre-sintering material is obtained, the obtained pre-sintering material is ground for the second time to obtain powder. Before the second grinding treatment, the method preferably further comprises the steps of cooling the pre-sintered material; the furnace cooling solution known to those skilled in the art may be used, and the present invention is not limited thereto.
In the present invention, the second grinding process is the same as the first grinding process, and preferably specifically includes:
mixing the obtained pre-sintering material, zirconium balls and water in a proportion of 1: (3-4): (2-3), ball-milling for 3-5 h at the rotating speed of 200-300 r/min, and drying at 80-150 ℃ to obtain a mixed material after the second grinding treatment;
more preferably:
mixing the obtained pre-sintering material, zirconium balls and water in a proportion of 1: 3: 2, ball-milling for 4 hours at the rotating speed of 250r/min, and then drying at 120 ℃ to obtain a mixed material after the second grinding treatment.
The ball milling equipment is not particularly limited in the present invention, and a planetary ball mill well known to those skilled in the art may be used.
In the present invention, after obtaining the pre-sintered material, the method preferably further comprises:
and mixing the obtained pre-sintered material with an additive, and then carrying out secondary grinding treatment to obtain powder. In the present invention, the additive is the same as that described in the above technical solution, and is not described herein again. In the present invention, the amount of the additive is preferably not more than 1.5%, more preferably 0.5% to 1%, of the mass of the pre-fired material.
After the powder is obtained, adding an adhesive into the obtained powder for granulation molding to obtain a ceramic green body; and sintering the obtained ceramic green body to obtain the microwave dielectric ceramic. In the present invention, the adhesive is sufficiently tacky to be appliedCan ensure good formability and mechanical strength of the green body, and can be completely volatilized after high-temperature calcination, so that residual impurities of the binder are not left in the green body. In the present invention, the binder is preferably a polyvinyl alcohol aqueous solution with a mass percentage of 4% to 8%, and more preferably a polyvinyl alcohol aqueous solution with a mass percentage of 6%. In the present invention, the polyvinyl alcohol is converted into CO after high-temperature calcination (subsequent sintering process)2And H2O, can be completely volatilized.
In the present invention, the mass ratio of the powder to the binder is preferably 100: (15-25), more preferably 100: 20.
in the present invention, the granulation molding process preferably includes:
adding an adhesive into the microwave dielectric ceramic powder, granulating and grinding for 0.5-1.5 h, sieving with a 70-90 mesh sieve, and pressing and molding the obtained powder under the pressure of 80-120 MPa to obtain a ceramic green body;
more preferably:
and adding an adhesive into the microwave dielectric ceramic powder, granulating and grinding for 1h, sieving by using an 80-mesh sieve, and pressing and molding the obtained powder under the pressure of 100MPa to obtain a ceramic green body. In the invention, the granulating and grinding process can uniformly mix the powder and the adhesive and granulate.
In the present invention, the ceramic green body is preferably a thin cylindrical green body having a thickness of 4mm to 10mm and a diameter of 8mm to 20mm, and more preferably a thin cylindrical green body having a thickness of 6mm and a diameter of 13mm (a cylinder having a diameter to height ratio of about 2.0).
In the invention, the sintering temperature is preferably 1100-1450 ℃, more preferably 1170-1300 ℃; the heating rate of the sintering is preferably 3-8 ℃/min, and more preferably 3 ℃/min; the heat preservation time for sintering is preferably 2h to 4h, and more preferably 3 h.
After sintering, the method preferably further comprises the steps of cooling a sintered product to obtain the microwave dielectric ceramic; the furnace cooling solution known to those skilled in the art may be used, and the present invention is not limited thereto.
The preparation method provided by the invention has the advantages of simple process, low sintering temperature, low cost, no toxicity, no pollution to the environment, suitability for large-scale industrialization and very wide development prospect, and meets the requirement of environmental protection.
The invention provides a microwave dielectric ceramic and a preparation method thereof, wherein the microwave dielectric ceramic has a general formula shown as the following formula: (1-x) Ca2Sm4Ti5O18-xSmAlO3(ii) a Wherein x is 0.05-0.25. Compared with the prior art, the microwave dielectric ceramic provided by the invention takes the composite oxide with the specific general formula as a main material, and SmAlO is adjusted3The content of (A) can realize that the dielectric constant is about 45 and the frequency temperature coefficient is continuously adjustable; in addition, the microwave dielectric ceramic has stable structure, specific dielectric constant and high Q multiplied by f value, and the temperature coefficient of the resonant frequency is continuously adjustable. Experimental results show that the dielectric constant of the microwave dielectric ceramic is between 40 and 46.1, the Q x f is more than 30000GHz and can reach 49700GHz, and compared with other microwave dielectric ceramics with the same dielectric constant, the Q x f value of the system is high, and the dielectric loss is low; meanwhile, the temperature coefficient of the resonance frequency is continuously adjustable between-7.4 PPM/DEG C to +6.7 PPM/DEG C, and the method is suitable for large-scale commercial use.
In addition, the preparation method provided by the invention has the advantages of simple process, low sintering temperature, low cost, no toxicity, no environmental pollution, suitability for large-scale industrialization and wide development prospect, and meets the requirement of environmental protection.
To further illustrate the present invention, the following examples are provided for illustration. The raw materials used in the following examples of the present invention are all commercially available products; wherein the adhesive is a polyvinyl alcohol aqueous solution with the mass percentage of 6%; the additive is a composite oxide and is prepared from the following components in a mass ratio of 50: 15: 25: 5: 5 SiO2、Al2O3、CaO、Y2O3And MgO, and the preparation method specifically comprises the following steps:
mixing SiO2、Al2O3、CaO、Y2O3Mixing with MgO, ball milling for 24 hr, drying, sieving, melting at 1500 deg.C for 20min,then deionized water is used for extraction and separation, and the mixture is crushed and sieved by a 200-mesh sieve to obtain the additive.
Example 1
(1) 29.95g of CaCO were weighed out under x ═ 0.153、108.95g Sm2O3、59.75g TiO2And 1.35g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere), heating at the rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material, zirconium balls and deionized water in a proportion of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with a 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1450 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The microwave dielectric ceramic provided by the embodiment 1 of the invention is tested for various properties, and specifically comprises the following steps:
polishing the surface of the prepared ceramic sample by a metallographic and flannelette medium, and measuring the dielectric constant epsilon by adopting an Agilent 5061B network analyzer according to a Hakki-Coleman methodrAnd tan delta, and calculating to obtain a quality factor Q multiplied by f; in addition, the measurement of the temperature coefficient of the resonant frequency is to directly connect a network analyzer with a constant temperature box, test the change value of the resonant frequency in the temperature range of 20-85 ℃, and then calculate tau according to the formula shown in formula (II)fA value;
the test results of various properties of the microwave dielectric ceramic provided in the embodiment 1 of the present invention are shown in table 1.
Example 2
(1) 29.95g of CaCO were weighed out under x ═ 0.153、108.95g Sm2O3、59.75g TiO2And 1.35g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere) at the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 0.5 percent of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with a 80-mesh sieve, pressing the obtained powder (with the pressure of 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1300 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The various properties of the microwave dielectric ceramic provided in example 2 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 1.
Example 3
(1) 29.95g of CaCO were weighed out under x ═ 0.153、108.95g Sm2O3、59.75g TiO2And 1.35g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere) at the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1170 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The various properties of the microwave dielectric ceramic provided in example 3 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 1.
Example 4
(1) 29.95g of CaCO were weighed out under x ═ 0.153、108.95g Sm2O3、59.75g TiO2And 1.35g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1000 ℃ (in atmospheric atmosphere) with the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1.5% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (with the pressure of 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1100 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The various properties of the microwave dielectric ceramic provided in example 4 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 1.
TABLE 1 data on various properties of microwave dielectric ceramics provided in embodiments 1 to 4 of the present invention
Example 5
(1) 30.59g of CaCO were weighed out in a scale of x-0.053、107.98g Sm2O3、61.02g TiO2And 0.41g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere) at the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1170 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The properties of the microwave dielectric ceramic provided in example 5 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 2.
Example 6
(1) 30.28g of CaCO were weighed out in a scale of x-0.13、108.44g Sm2O3、60.42g TiO2And 0.86g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, drying at 120 ℃, and then drying at 1050 DEG CPresintering for 3h (in atmospheric atmosphere), wherein the heating rate is 3 ℃/min, and then cooling along with a furnace to obtain a presintering material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1170 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The properties of the microwave dielectric ceramic provided in example 6 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 2.
Example 7
(1) 29.58g of CaCO were weighed out in the proportions 0.2 ═ x3、109.51g Sm2O3、59.02g TiO2And 1.88g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere) at the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1170 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The properties of the microwave dielectric ceramic provided in example 7 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 2.
Example 8
(1) 29.18g of CaCO were weighed out in the proportions 0.25 ═ x3、110.13g Sm2O3、58.21g TiO2And 2.48g of Al2O3(ii) a Mixing the raw materials, zirconium balls and deionized water in a proportion of 1: 3: 2, ball-milling for 4 hours by using a planetary mill wet method, drying at 120 ℃, pre-burning for 3 hours at 1050 ℃ (in atmospheric atmosphere) at the heating rate of 3 ℃/min, and then cooling along with a furnace to obtain a pre-burning material; mixing the pre-sintering material with an additive to obtain a mixture of the pre-sintering material and the additive, wherein the amount of the additive is 1% of the mass of the pre-sintering material; mixing the mixture of the pre-sintering material and the additive, zirconium balls and deionized water in a ratio of 1: 3: 2, ball milling for 4 hours by a planetary mill wet method, and drying at 120 ℃ to obtain the microwave dielectric ceramic powder.
(2) Adding an adhesive accounting for 20% of the mass of the powder into the microwave dielectric ceramic powder obtained in the step (1), granulating and grinding for 1h, sieving with an 80-mesh sieve, pressing the obtained powder (the pressure is 100MPa) into a thin cylindrical blank with the thickness of 6mm and the diameter of 13mm, sintering the obtained blank at 1170 ℃ to form ceramic, heating at the rate of 3 ℃/min, keeping the temperature for 3h, and cooling with a furnace to obtain the microwave dielectric ceramic.
The properties of the microwave dielectric ceramic provided in example 8 of the present invention were tested according to the test method provided in example 1, and the results are shown in table 2.
TABLE 2 data on various properties of microwave dielectric ceramics provided in embodiments 5 to 8 of the present invention
As can be seen from tables 1-2, the dielectric constant of the microwave dielectric ceramic provided by the invention is between 40 and 46.1, Qxf is more than 30000GHz and can reach 49700GHz, and compared with other microwave dielectric ceramics with the same dielectric constant, the Q xf value of the system is high and the dielectric loss is low; meanwhile, the temperature coefficient of the resonance frequency is continuously adjustable between-7.4 PPM/DEG C to +6.7 PPM/DEG C.
In addition, the preparation method provided by the invention has the advantages of simple process, low sintering temperature, no toxicity, no pollution to the environment, suitability for large-scale industrialization and very wide development prospect, and meets the requirement of environmental protection.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A microwave dielectric ceramic having the general formula shown in formula (I):
(1-x)Ca2Sm4Ti5O18-xSmAlO3formula (I);
in the formula (I), x is 0.05-0.25;
the microwave dielectric ceramic further comprises:
an additive;
the additive is prepared from the following components in percentage by mass (40-55): (10-30): (15-30): (2-10): (1-10) SiO2、Al2O3、CaO、Y2O3And MgO.
2. The microwave dielectric ceramic of claim 1, wherein the preparation method of the additive specifically comprises:
mixing SiO2、Al2O3、CaO、Y2O3Mixing with MgO, ball milling, melting at 1400-1600 deg.c for 10-30 min, separating, crushing and sieving to obtain the additive.
3. A method for preparing a microwave dielectric ceramic as claimed in claim 1, comprising the steps of:
a) mixing CaCO3、Sm2O3、TiO2And Al2O3After mixing, carrying out primary grinding treatment, and then carrying out presintering to obtain a presintering material; then, carrying out secondary grinding treatment on the obtained pre-sintering material to obtain powder;
b) adding an adhesive into the powder obtained in the step a) for granulation forming to obtain a ceramic green body; and sintering the obtained ceramic green body to obtain the microwave dielectric ceramic.
4. The preparation method according to claim 3, wherein the first grinding treatment in step a) is carried out by:
mixing the mixed raw materials, zirconium balls and water in a proportion of 1: (3-4): (2-3), ball-milling for 3-5 h at the rotating speed of 200-300 r/min, and drying at 80-150 ℃ to obtain the mixed material after the first grinding treatment.
5. The preparation method according to claim 3, wherein the temperature of the pre-sintering in the step a) is 900 ℃ to 1100 ℃, the heating rate is 3 ℃/min to 8 ℃/min, and the holding time is 3h to 4 h.
6. The preparation method according to claim 4, wherein the adhesive in the step b) is a polyvinyl alcohol aqueous solution with the mass percentage of 4-8%;
the mass ratio of the powder to the adhesive is 100: (15-25).
7. The preparation method according to claim 3, wherein the granulating and forming process in the step b) is specifically as follows:
adding an adhesive into the microwave dielectric ceramic powder, granulating and grinding for 0.5-1.5 h, sieving with a 70-90 mesh sieve, and pressing and molding the obtained powder under the pressure of 80-120 MPa to obtain the ceramic green body.
8. The preparation method according to claim 3, wherein the sintering temperature in step b) is 1100-1450 ℃, the heating rate is 3-8 ℃/min, and the holding time is 2-4 h.
9. The method according to any one of claims 3 to 8, wherein the step a) further comprises:
and mixing the obtained pre-sintered material with an additive, and then carrying out secondary grinding treatment to obtain powder.
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