CN112759382A - 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 discloses a microwave dielectric ceramic and a preparation method thereof, wherein the chemical composition of the ceramic has an expression of aCaO bSrO cLn2O3·dNb2O5·eTiO2(I) Wherein Ln ═ Y, Nd or Sm. The microwave dielectric ceramic contains rare earth element oxides of Y, Nd or Sm, has good microwave dielectric property, and comprises two rare earth element oxides and Nb2O5And TiO2The microwave dielectric ceramic obtained by the combined action of sintering and sintering has good microwave dielectric property.
Description
Technical Field
The invention relates to the field of ceramic materials, in particular to a microwave dielectric ceramic and a preparation method thereof.
Background
A filter and a resonator are used in a mobile communication base station system, and the most core raw material for producing the filter and the resonator is microwave dielectric ceramic powder with the dielectric constant of 45 and the Q multiplied by F value of 40000 or above. The ceramic powder is mainly used for microwave components such as resonators, filters, dielectric antennas, dielectric guided wave loops and the like, and can be used for mobile communication, satellite communication, military radars and the like. With the development of scientific technology, the amount of communication information is rapidly increased, and the requirements of people on wireless communication, the use of microwave communication systems such as satellite communication and satellite direct broadcast television becomes a necessary trend for the development of current communication technology.
The microwave dielectric ceramic prepared from the microwave dielectric ceramic powder is a novel functional electronic ceramic which is rapidly developed in the last 30 years, and has the characteristics of low loss, small frequency temperature coefficient, high dielectric constant and the like. At present, the microwave dielectric ceramic material with dielectric constant of 45 is developed most rapidly and best in Japan, and the production level of microwave ceramic materials and devices is highest by Murata [ Cuntia ] company, Trans-Tech company in Japan, Filtronic [ Feiko ] and other companies, and the annual value is more than billion dollars. With the development of the international and domestic mobile communication industry toward 4G, a large number of ceramic resonators and filters having a dielectric constant of 45 are required for the construction of base stations for mobile communication. At present, the microwave medium raw material with high QxFo [ ceramic quality factor ] value of dielectric constant of 45 in China is still a blank, and is almost completely monopolized by Japan at the present stage, and raw material powder with the specification is imported from Japan and has high price and long transaction period in other countries.
CaTiO with perovskite structure3-NdAlO3The ceramic material has excellent microwave dielectric property: r is about 45, Qxf is more than or equal to 44000GHz, and tau f is about 0 ppm/DEG C. But due to the rare earth oxide Nd2O3The price is expensive, and the commercial application of the material is limited to a certain extent. Relatively speaking, homologous rare earth oxide Sm2O3、La2O3Is relatively low in price and can replace Nd2O3And has good microwave dielectric properties. The patent aims to obtain a substitute CaTiO by improving the formula and optimizing the preparation process3-NdAlO3The novel microwave dielectric ceramic has practical value so as to meet the technical requirements of systems such as a communication base station and the like.
Disclosure of Invention
Aiming at the technical problems, the invention aims to provide a microwave dielectric ceramic and a preparation method thereof.
The first aspect of the present invention provides a microwave dielectric ceramic having a chemical composition represented by formula (I), aCaO bSrO cLn2O3·dNb2O5·eTiO2(I)，
Wherein Ln is Y, Nd or Sm, a is more than or equal to 10 mol% and less than or equal to 25 mol%, b is more than or equal to 5 mol% and less than or equal to 25 mol%, c is more than or equal to 0 mol% and less than or equal to 20 mol%, d is more than or equal to 15 mol% and less than or equal to 25 mol%, e is more than or equal to 10 mol% and less than or equal to 50 mol%, and a + b + c + d + e is 100%.
Preferably, the a satisfies the following condition: a is more than or equal to 15 mol% and less than or equal to 20 mol%.
Preferably, b satisfies the following condition: b is more than or equal to 10 mol% and less than or equal to 15 mol%.
Preferably, c satisfies the following condition: c is more than or equal to 0.01 mol% and less than or equal to 10 mol%.
Preferably, d satisfies the following condition: d is more than or equal to 18 mol% and less than or equal to 22 mol%.
Preferably, said e satisfies the following condition: e is more than or equal to 30 mol% and less than or equal to 40 mol%.
In another aspect, the present invention further provides a method for manufacturing a microwave dielectric ceramic in the first aspect of the present invention, which comprises the following steps:
step 1): CaO, SrO and Ln are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The method of pulverization in the present invention is not particularly limited, and pulverization can be carried out according to a method known to those skilled in the art, such as mortar pulverization. After the grinding, the ball milling is carried out after the sieving is carried out, and a 40-mesh sieve is preferably selected during the sieving. The method for ball milling is not particularly limited, and the ball milling is preferably carried out in a medium by using milling balls, the medium is preferably ethanol, and the milling balls can be zirconium oxide milling balls or agate balls.
The granulation is preferably performed by mixing powder and a binder into a slurry and granulating the slurry. The binder is preferably a polyvinyl alcohol solution with the mass concentration of 5-8 wt%, and the usage amount of the binder is preferably 10-15 wt%. The method of granulation is not particularly limited in the present invention. The pressure of the dry pressing is preferably 100-150 MPa. After the pressed sheet is obtained, the binder in the formed pressed sheet is preferably removed, and the method for removing the binder is preferably to keep the pressed sheet at 550-650 ℃ for 1-3 hours.
Wherein the plasticizer comprises polyethylene glycol plasticizer PEG400 or polyethylene glycol dicarboxylic acid plasticizer PEG 20K. Plasticizer PEG20K (20), formula (C)2H4O)nC4H6O5. Plasticizer PEG400 is polyethylene glycol (PEG)400, appearance (25 ℃): condensation point (. degree. C.) of colorless viscous liquid: clarity and color of the solution: not concentrated and not deeper than 2# standard solution; viscosity 40(mm 2/s): average molecular weight of 37-45: 380-420; pH value: 4-7 ethylene glycol or diethylene glycol: less than or equal to 0.25 percent; residue on ignition (%): less than or equal to 0.2 arsenic salt (ppm): less than or equal to 3 heavy metals (ppm): less than or equal to 5; storage and transportation: the product is nontoxic and nonflammable, and can be transported according to common chemicals and stored in dry place in a sealed manner.
The dispersant is 5468CF, and the release agent is LU 6418: the dispersing agent 5468CF is a special high-molecular amine salt copolymer, colorless transparent liquid, a special dispersing agent and a dispergator for electronic ceramic products, and other conductive particles cannot be introduced when the product is used, so that the sintering degree is low. The mold release agent LU6418 refers to stearic acid NOPCOCERALU-6418, has a melting point of 53 ℃ and 30 percent, is a mold release agent for compression molding of fine ceramics, and is very effective.
Compared with the prior art, the chemical composition of the microwave dielectric ceramic has the expression of aCaO bSrO cLn2O3·dNb2O5·eTiO2(I) Wherein Ln ═ Y, Nd or Sm. The microwave dielectric ceramic contains rare earth element oxides of Y, Nd or Sm, has good microwave dielectric property, and comprises two rare earth element oxides and Nb2O5And TiO2The microwave dielectric ceramic obtained by the combined action of sintering and sintering has good microwave dielectric property. Furthermore, since Y, Nd or Sm oxide is opposite to Nd2O3The price is cheaper, so the microwave dielectric ceramic of the invention is cheap. The experimental result shows that the microwave dielectric ceramic epsilon of the inventionrIs 23-35, Qinf is 58000 to 86000GHz, taufThe dielectric ceramic is-2-6 ppm/DEG C, is a high-quality low-loss microwave dielectric ceramic, can be widely applied to preparation of microwave devices such as dielectric resonators, filters, duplexers and the like with excellent performance, and meets technical requirements of systems such as communication base stations and the like.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
[ example 1 ]
Step 1): CaO, SrO and Y are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO cY2O3·dNb2O5·eTiO2(I) The mole percentages of a, b, c, d, and e are 15 mol%, 12 mol%, 18 mol%, 21 mol%, and 34 mol%, respectively. By means of mediaMass resonator method for measuring microwave dielectric constant epsilon of microwave dielectric ceramic of the embodimentrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
[ example 2 ]
Step 1): CaO, SrO and Nd are added according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO cNd2O3·dNb2O5·eTiO2(I) 17 mol% for a, 13 mol% for b, 18 mol% for c, 20 mol% for d, and 32 mol% for e. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
[ example 3 ]
Step 1): CaO, SrO and Sm are added according to a certain molar ratio2O3、Nb2O5And TiO2With deionized water andfully mixing the powder;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO cY2O3·dNb2O5·eTiO2(I) The values a, b, c, d, and e are 16 mol%, 15 mol%, 11 mol%, 19 mol%, and 39 mol%, respectively. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
[ example 4 ]
Step 1): CaO, SrO and Y are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO cY2O3·dNb2O5·eTiO2(I) The content of "a" is 20 mol%, the content of "b" is 15 mol%, the content of "c" is 5 mol%, the content of "d" is 20 mol%, and the content of "e" is 30 mol%. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
[ example 5 ]
Step 1): CaO, SrO and Y are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristicsAnd (3) carrying out mark: aCaO bSrO cY2O3·dNb2O5·eTiO2(I) The mole percentages of "a" and "b" are 17 mol%, 10 mol%, 3 mol%, 23 mol%, and 47 mol%, respectively. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
[ example 6 ]
Step 1): CaO, SrO and Y are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO cY2O3·dNb2O5·eTiO2(I) The mole percentages of a, b, c, d, and e are 25 mol%, 20 mol%, 1 mol%, 22 mol%, and 32 mol%, respectively. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
Comparative example 1
Step 1): CaO, SrO and Nb are added according to a certain molar ratio2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out glue removal treatment for 2 hours in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
The adding proportion of the raw materials is controlled in the preparation process, so that the obtained ceramic has the following characteristics: aCaO bSrO dNb2O5·eTiO2(I) The content of "a" is 25 mol%, the content of "b" is 20 mol%, the content of "d" is 23 mol%, and the content of "e" is 32 mol%. The microwave dielectric constant ε of the microwave dielectric ceramic of this example was measured by a dielectric resonator methodrThe quality factor Qxf value and the temperature drift tau of the microwave dielectric ceramic of the embodiment are tested by a dielectric resonator methodfSee table 1 for details.
TABLE 1
The experimental result shows that the microwave dielectric ceramic epsilon of the inventionr23 to 35, Qxf of 58000 to 86000GHz, τfIs-2 to 6 ppm/DEG C, is oneThe high-quality low-loss microwave dielectric ceramic can be widely applied to the preparation of microwave devices with excellent performance, such as dielectric resonators, filters, duplexers and the like, and meets the technical requirements of systems, such as communication base stations and the like.
The foregoing description has disclosed fully preferred embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the present invention without departing from the scope of the appended claims. Accordingly, the scope of the appended claims is not to be limited to the specific embodiments described above.
Claims (10)
1. A microwave dielectric ceramic is characterized in that the chemical composition expression is formula (I)
aCaO·bSrO·cLn2O3·dNb2O5·eTiO2(I)，
Wherein Ln is Y, Nd or Sm, a is more than or equal to 10 mol% and less than or equal to 25 mol%, b is more than or equal to 5 mol% and less than or equal to 25 mol%, c is more than or equal to 0 mol% and less than or equal to 20 mol%, d is more than or equal to 15 mol% and less than or equal to 25 mol%, e is more than or equal to 10 mol% and less than or equal to 50 mol%, and a + b + c + d + e is 100%.
2. A microwave dielectric ceramic according to claim 1, wherein a satisfies the following condition: a is more than or equal to 15 mol% and less than or equal to 20 mol%.
3. A microwave dielectric ceramic according to claim 2, wherein b satisfies the following condition: b is more than or equal to 10 mol% and less than or equal to 15 mol%.
4. A microwave dielectric ceramic according to claim 3, wherein c satisfies the following condition: c is more than or equal to 0.01 mol% and less than or equal to 10 mol%.
5. A microwave dielectric ceramic according to claim 4, wherein d satisfies the following condition: d is more than or equal to 18 mol% and less than or equal to 22 mol%.
6. A microwave dielectric ceramic according to claim 5, wherein e satisfies the following condition: e is more than or equal to 30 mol% and less than or equal to 40 mol%.
7. A method of making a microwave dielectric ceramic as claimed in any one of claims 1 to 6, comprising the steps of:
step 1): CaO, SrO and Ln are mixed according to a certain molar ratio2O3、Nb2O5And TiO2The oxide of (2) is fully mixed with deionized water and a dispersant;
step 2): ball milling the mixture for 8 hours, wherein the grain diameter of the milling ball is 0.5 mu m;
step 3): after ball milling, drying at 90-120 ℃ for 8 hours, calcining at 1000-1200 ℃ for 4-5 hours, naturally cooling to room temperature, introducing into a pulverizer for pulverization, and sieving with a 40-mesh sieve to obtain powder A;
step 4): assembling and spraying the powder A, deionized water, a dispersing agent, a plasticizer and a release agent according to a certain molar ratio to obtain powder B;
step 5): and adding a proper amount of binder (5 wt% of polyvinyl alcohol solution) into the powder B for granulation, then putting the powder into a mould, pressing and forming under the pressure of 100MPa, then putting the mould into a high-temperature furnace, carrying out degumming treatment for 2 hours at the temperature of 500 ℃ in the air atmosphere, and then heating to 1100-1300 ℃ to sinter the ceramic into the ceramic.
8. A method for making a microwave dielectric ceramic as claimed in claim 7 wherein the plasticizer comprises polyethylene glycol plasticizer PEG400 or polyethylene glycol dicarboxylic acid plasticizer PEG 20K.
9. A method for making a microwave dielectric ceramic as claimed in claim 8 wherein the dispersant is 5468CF and the release agent is LU 6418.
10. A microwave dielectric ceramic as claimed in claim 7 wherein the binder is a 5-20 wt% solution of a polyvinyl alcohol.
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