FREQUENCY-STABLE LOW-DIELECTRIC MICROWAVE DIELECTRIC CERAMIC MATERIAL AND PREPARATION METHOD THEREOF

Abstract

The present invention relates to a frequency-stable low-dielectric microwave dielectric ceramic material and a preparation method thereof. The material is prepared from the following components in percentage by mass: 70-90% of a main-phase ceramic material A, 10-30% of an auxiliary-phase ceramic material B and 0-1.0% of an oxide sintering aid C. The main-phase ceramic material A is Mg.sub.xMe.sub.ySiO.sub.2+x+y; the auxiliary-phase ceramic material B is composed of RO-bRe.sub.2O.sub.3-cTiO.sub.2, R is at least one of Ca or Sr, Re.sub.2O.sub.3 is at least two of Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3; and the oxide sintering aid C is at least one of MnO.sub.2, WO.sub.3 and CeO.sub.2.

Claims

1. A frequency-stable low-dielectric microwave dielectric ceramic material, consisting of the following components in percentage by mass: 70 to 90% of a main-phase ceramic material A, 10 to 30% of an auxiliary-phase ceramic material B and 0 to 1.0% of an oxide sintering aid C, wherein a sum of mass percentage of the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C is 100%; wherein the main-phase ceramic material A satisfies a chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y, and Me is Co or Zn, the auxiliary-phase ceramic material B is composed of RO-bRe.sub.2O.sub.3-cTiO.sub.2, wherein R is at least one of Ca or Sr, and Re.sub.203 is at least two of Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3, and the oxide sintering aid C is at least one of MnO.sub.2, MnCO.sub.3, WO.sub.3, and CeO.sub.2.

2. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, wherein 2.00x+y2.20, 1.80x2.15, 0y0.40.

3. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, wherein 1.0a2.0, 0.05b0.50, 1.0c1.5.

4. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, wherein 2.00x+y2.10, 1.80x2.05, 0.05y0.25.

5. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, wherein 1.0a1.5, 0.05b0.30, 1.0c1.2.

6. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, wherein Re.sub.2O.sub.3 in the chemical formula of the auxiliary-phase ceramic material B is Al.sub.2O.sub.3 and Sm.sub.2O.sub.3, or Al.sub.2O.sub.3 and Nd.sub.2O.sub.3, or Al.sub.2O.sub.3 and Y.sub.2O.sub.3, or Al.sub.2O.sub.3 and La.sub.2O.sub.3.

7. A preparation method for preparing the frequency-stable low-dielectric microwave dielectric ceramic material according to claim 1, comprising the following steps: step 1) synthesis of the main-phase ceramic material A: raw materials MgO, SiO.sub.2, ZnO, and CoO are weighed and mixed according to a ratio of the chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y to obtain a first mixture, wherein a deionized water is used as a solvent, and the first mixture is ball-milled for 16 to 24 hours and then dried; the dried mixture is filtered through a 40-mesh sieve, put into an alumina crucible, calcined at 1150 C. to 1300 C. for 2 to 4 hours to synthesize a main-phase powder A, the main-phase powder A is ground and filtered through the 40-mesh sieve for use; step 2) synthesis of the auxiliary-phase ceramic material B: according to the chemical formula RO-bRe.sub.2O.sub.3-cTiO.sub.2, raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3 are weighed and mixed to obtain a second mixture, wherein the deionized water is used as the solvent, the second mixture is ball-milled for 16 to 24 hours, and then dried, and then filtered through the 40-mesh sieve, loaded into the alumina crucible, calcined at 1100 C. to 1300 C. for 2 to 4 hours to synthesize an auxiliary-phase powder B, which is ground and filtered through the 40-mesh sieve for use; step 3) the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C are prepared according to a certain ratio to obtain a third mixture, ZrO.sub.2 balls are used as a grinding medium, and the deionized water is added according to a weight ratio of the third mixture to the deionized water 1:1.5 to 2, wet mixing is adopted to mix the third mixture and the deionized water for 12 to 18 hours, thn being dried at 120 C., added with 1% to 3% of polyvinyl alcohol binder by weight for grinding and granulating, and filtered through the 40-mesh sieve, under a pressure of 80 to 120 MPa, pressed into a green body with a diameter of 20 mm and a thickness of 10 mm, and sintered at 1300 C. to 1450 C. for 2 to 4 hours in an air atmosphere to obtain the frequency-stable low-dielectric microwave dielectric ceramic material.

8. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 2, wherein Re.sub.2O.sub.3 in the chemical formula of the auxiliary-phase ceramic material B is Al.sub.2O.sub.3 and Sm.sub.2O.sub.3, or Al.sub.2O.sub.3 and Nd.sub.2O.sub.3, or Al.sub.2O.sub.3 and Y.sub.2O.sub.3, or Al.sub.2O.sub.3 and La.sub.2O.sub.3.

9. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 3, wherein Re.sub.2O.sub.3 in the chemical formula of the auxiliary-phase ceramic material B is Al.sub.2O.sub.3 and Sm.sub.2O.sub.3, or Al.sub.2O.sub.3 and Nd.sub.2O.sub.3, or Al.sub.2O.sub.3 and Y.sub.2O.sub.3, or Al.sub.2O.sub.3 and La.sub.2O.sub.3.

10. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 4, wherein Re.sub.2O.sub.3 in the chemical formula of the auxiliary-phase ceramic material B is Al.sub.2O.sub.3 and Sm.sub.2O.sub.3, or Al.sub.2O.sub.3 and Nd.sub.2O.sub.3, or Al.sub.2O.sub.3 and Y.sub.2O.sub.3, or Al.sub.2O.sub.3 and La.sub.2O.sub.3.

11. The frequency-stable low-dielectric microwave dielectric ceramic material according to claim 5, wherein Re.sub.2O.sub.3 in the chemical formula of the auxiliary-phase ceramic material B is Al.sub.2O.sub.3 and Sm.sub.2O.sub.3, or Al.sub.2O.sub.3 and Nd.sub.2O.sub.3, or Al.sub.2O.sub.3 and Y.sub.2O.sub.3, or Al.sub.2O.sub.3 and La.sub.2O.sub.3.

12. A preparation method for preparing the frequency-stable low-dielectric microwave dielectric ceramic material according to claim 2, comprising the following steps: step 1) synthesis of the main-phase ceramic material A: raw materials MgO, SiO.sub.2, ZnO, and CoO are weighed and mixed according to a ratio of the chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y to obtain a first mixture, wherein a deionized water is used as a solvent, and the first mixture is ball-milled for 16 to 24 hours and then dried; the dried mixture is filtered through a 40-mesh sieve, put into an alumina crucible, calcined at 1150 C. to 1300 C. for 2 to 4 hours to synthesize a main-phase powder A, the main-phase powder A is ground and filtered through the 40-mesh sieve for use; step 2) synthesis of the auxiliary-phase ceramic material B: according to the chemical formula RO-bRe.sub.2O.sub.3-cTiO.sub.2, raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3 are weighed and mixed to obtain a second mixture, wherein the deionized water is used as the solvent, the second mixture is ball-milled for 16 to 24 hours, and then dried, and then filtered through the 40-mesh sieve, loaded into the alumina crucible, calcined at 1100 C. to 1300 C. for 2 to 4 hours to synthesize an auxiliary-phase powder B, which is ground and filtered through the 40-mesh sieve for use; step 3) the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C are prepared according to a certain ratio to obtain a third mixture, ZrO.sub.2 balls are used as a grinding medium, and the deionized water is added according to a weight ratio of the third mixture to the deionized water 1:1.5 to 2, wet mixing is adopted to mix the third mixture and the deionized water for 12 to 18 hours, thn being dried at 120 C., added with 1% to 3% of polyvinyl alcohol binder by weight for grinding and granulating, and filtered through the 40-mesh sieve, under a pressure of 80 to 120 MPa, pressed into a green body with a diameter of 20 mm and a thickness of 10 mm, and sintered at 1300 C. to 1450 C. for 2 to 4 hours in an air atmosphere to obtain the frequency-stable low-dielectric microwave dielectric ceramic material.

13. A preparation method for preparing the frequency-stable low-dielectric microwave dielectric ceramic material according to claim 3, comprising the following steps: step 1) synthesis of the main-phase ceramic material A: raw materials MgO, SiO.sub.2, ZnO, and CoO are weighed and mixed according to a ratio of the chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y to obtain a first mixture, wherein a deionized water is used as a solvent, and the first mixture is ball-milled for 16 to 24 hours and then dried; the dried mixture is filtered through a 40-mesh sieve, put into an alumina crucible, calcined at 1150 C. to 1300 C. for 2 to 4 hours to synthesize a main-phase powder A, the main-phase powder A is ground and filtered through the 40-mesh sieve for use; step 2) synthesis of the auxiliary-phase ceramic material B: according to the chemical formula RO-bRe.sub.2O.sub.3-cTiO.sub.2, raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3 are weighed and mixed to obtain a second mixture, wherein the deionized water is used as the solvent, the second mixture is ball-milled for 16 to 24 hours, and then dried, and then filtered through the 40-mesh sieve, loaded into the alumina crucible, calcined at 1100 C. to 1300 C. for 2 to 4 hours to synthesize an auxiliary-phase powder B, which is ground and filtered through the 40-mesh sieve for use; step 3) the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C are prepared according to a certain ratio to obtain a third mixture, ZrO.sub.2 balls are used as a grinding medium, and the deionized water is added according to a weight ratio of the third mixture to the deionized water 1:1.5 to 2, wet mixing is adopted to mix the third mixture and the deionized water for 12 to 18 hours, thn being dried at 120 C., added with 1% to 3% of polyvinyl alcohol binder by weight for grinding and granulating, and filtered through the 40-mesh sieve, under a pressure of 80 to 120 MPa, pressed into a green body with a diameter of 20 mm and a thickness of 10 mm, and sintered at 1300 C. to 1450 C. for 2 to 4 hours in an air atmosphere to obtain the frequency-stable low-dielectric microwave dielectric ceramic material.

14. A preparation method for preparing the frequency-stable low-dielectric microwave dielectric ceramic material according to claim 4, comprising the following steps: step 1) synthesis of the main-phase ceramic material A: raw materials MgO, SiO.sub.2, ZnO, and CoO are weighed and mixed according to a ratio of the chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y to obtain a first mixture, wherein a deionized water is used as a solvent, and the first mixture is ball-milled for 16 to 24 hours and then dried; the dried mixture is filtered through a 40-mesh sieve, put into an alumina crucible, calcined at 1150 C. to 1300 C. for 2 to 4 hours to synthesize a main-phase powder A, the main-phase powder A is ground and filtered through the 40-mesh sieve for use; step 2) synthesis of the auxiliary-phase ceramic material B: according to the chemical formula RO-bRe.sub.2O.sub.3-cTiO.sub.2, raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3 are weighed and mixed to obtain a second mixture, wherein the deionized water is used as the solvent, the second mixture is ball-milled for 16 to 24 hours, and then dried, and then filtered through the 40-mesh sieve, loaded into the alumina crucible, calcined at 1100 C. to 1300 C. for 2 to 4 hours to synthesize an auxiliary-phase powder B, which is ground and filtered through the 40-mesh sieve for use; step 3) the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C are prepared according to a certain ratio to obtain a third mixture, ZrO.sub.2 balls are used as a grinding medium, and the deionized water is added according to a weight ratio of the third mixture to the deionized water 1:1.5 to 2, wet mixing is adopted to mix the third mixture and the deionized water for 12 to 18 hours, thn being dried at 120 C., added with 1% to 3% of polyvinyl alcohol binder by weight for grinding and granulating, and filtered through the 40-mesh sieve, under a pressure of 80 to 120 MPa, pressed into a green body with a diameter of 20 mm and a thickness of 10 mm, and sintered at 1300 C. to 1450 C. for 2 to 4 hours in an air atmosphere to obtain the frequency-stable low-dielectric microwave dielectric ceramic material.

15. A preparation method for preparing the frequency-stable low-dielectric microwave dielectric ceramic material according to claim 5, comprising the following steps: step 1) synthesis of the main-phase ceramic material A: raw materials MgO, SiO.sub.2, ZnO, and CoO are weighed and mixed according to a ratio of the chemical formula Mg.sub.xMe.sub.ySiO.sub.2+x+y to obtain a first mixture, wherein a deionized water is used as a solvent, and the first mixture is ball-milled for 16 to 24 hours and then dried; the dried mixture is filtered through a 40-mesh sieve, put into an alumina crucible, calcined at 1150 C. to 1300 C. for 2 to 4 hours to synthesize a main-phase powder A, the main-phase powder A is ground and filtered through the 40-mesh sieve for use; step 2) synthesis of the auxiliary-phase ceramic material B: according to the chemical formula RO-bRe.sub.2O.sub.3-cTiO.sub.2, raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Nd.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and La.sub.2O.sub.3 are weighed and mixed to obtain a second mixture, wherein the deionized water is used as the solvent, the second mixture is ball-milled for 16 to 24 hours, and then dried, and then filtered through the 40-mesh sieve, loaded into the alumina crucible, calcined at 1100 C. to 1300 C. for 2 to 4 hours to synthesize an auxiliary-phase powder B, which is ground and filtered through the 40-mesh sieve for use; step 3) the main-phase ceramic material A, the auxiliary-phase ceramic material B and the oxide sintering aid C are prepared according to a certain ratio to obtain a third mixture, ZrO.sub.2 balls are used as a grinding medium, and the deionized water is added according to a weight ratio of the third mixture to the deionized water 1:1.5 to 2, wet mixing is adopted to mix the third mixture and the deionized water for 12 to 18 hours, thn being dried at 120 C., added with 1% to 3% of polyvinyl alcohol binder by weight for grinding and granulating, and filtered through the 40-mesh sieve, under a pressure of 80 to 120 MPa, pressed into a green body with a diameter of 20 mm and a thickness of 10 mm, and sintered at 1300 C. to 1450 C. for 2 to 4 hours in an air atmosphere to obtain the frequency-stable low-dielectric microwave dielectric ceramic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings that constitute a part of the present disclosure are used to provide further understanding of the present disclosure, and the schematic embodiments and descriptions of the present disclosure are used to explain the present disclosure and do not constitute a limitation to the present disclosure.

[0024] In FIG. 1, (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Embodiment 3, and (d) is a scanning electron microscope image of the microwave dielectric ceramic material prepared in Embodiment 6.

[0025] FIG. 2 is a comparison diagram of the frequency temperature coefficient of Comparative Examples 1, 2 and Embodiments 5 and 8 at different temperatures.

DESCRIPTION OF THE EMBODIMENTS

[0026] The present disclosure will be described below in conjunction with specific embodiments.

Embodiment 1

[0027] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and CoO are weighed and mixed according to the ratio of chemical formula Mg.sub.2.00Co.sub.0.10SiO.sub.4.10. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 20 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1250 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0028] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, La.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 0.99CaO.Math.0.11SrO-0.06La.sub.2O.sub.3.Math.0.05Al.sub.2O.sub.3-1.00TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 16 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0029] 3) 82.3 wt % of the main-phase ceramic material A and 16.7 wt % of the auxiliary-phase ceramic material B are mixed, and 0.25 wt % of CeO.sub.2 and 0.75% of MnO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 15 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1300 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 2

[0030] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2 and ZnO are weighed according to the ratio of chemical formula Mg.sub.2.02Zn.sub.0.05SiO.sub.4.07. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 16 hours, dried in a 120 C. oven, ground by using a quartz mortar, and filtered through a 40-mesh sieve. Then the powder is put into an alumina crucible for calcination at 1200 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0031] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, Nd.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition 1.05CaO.Math.0.12SrO-0.08Nd.sub.2O.sub.3.Math.0.06Al.sub.2O.sub.3-1.05TiO.sub.2. Deionized water is added according to the ratio of mixture to deionized water 1:2, the material is mixed and ground for 20 hours, and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve. Then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0032] 3) 81.8 wt % of the main-phase ceramic material A and 17.7 wt % of the auxiliary-phase ceramic material B are mixed, and 0.2 wt % of WO.sub.3 and 0.3 wt % of MnO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 12 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1350 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 3

[0033] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and CoO are weighed and mixed according to the ratio of chemical formula Mg.sub.1.95Co.sub.0.10SiO.sub.4.05. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 20 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1150 C. for 4 hours to obtain the main-phase pre-calcined powder A.

[0034] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, La.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 1.25CaO.Math.0.20SrO-0.15La.sub.2O.sub.3.Math.0.12Al.sub.2O.sub.3-1.20TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 16 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1250 C. for 2 hours to obtain auxiliary-phase pre-calcined powder B.

[0035] 3) 79.5 wt % of the main-phase ceramic material A and 20.1 wt % of the auxiliary-phase ceramic material B are mixed, and 0.3 wt % of CeO.sub.2 and 0.1% of WO.sub.3 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 15 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1300 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 4

[0036] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and CoO are weighed and mixed according to the ratio of chemical formula Mg.sub.2.00Co.sub.0.05SiO.sub.4.05. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 20 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0037] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 0.85CaO.Math.0.45SrO-0.15Sm.sub.2O.sub.3.Math.0.10Al.sub.2O.sub.3-1.10TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 20 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1150 C. for 4 hours to obtain auxiliary-phase pre-calcined powder B.

[0038] 3) 84.6 wt % of the main-phase ceramic material A, 14.9 wt % of the auxiliary-phase ceramic material B and 0.5 wt % of MnO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 18 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1400 C. for 2 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 5

[0039] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and ZnO are weighed and mixed according to the ratio of chemical formula Mg.sub.1.90Zn.sub.0.20SiO.sub.4.10. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 16 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1150 C. for 2 hours to obtain the main-phase pre-calcined powder A.

[0040] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, Nd.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 0.95CaO.Math.0.15SrO-0.10Y.sub.2O.sub.3.Math.0.08Al.sub.2O.sub.3-1.05TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 24 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1100 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0041] 3) 80.6 wt % of the main-phase ceramic material A, 18.4 wt % of the auxiliary-phase ceramic material B, 0.5 wt % of CeO.sub.2, and 0.5 wt % of MnO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 12 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1300 C. for 4 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 6

[0042] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and ZnO are weighed and mixed according to the ratio of chemical formula Mg.sub.2.00Zn.sub.0.03SiO.sub.4.10. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 16 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0043] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, Nd.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 1.10CaO.Math.0.20SrO-0.18Nd.sub.2O.sub.3.Math.0.12Al.sub.2O.sub.3-1.20TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 20 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1250 C. for 2 hours to obtain auxiliary-phase pre-calcined powder B.

[0044] 3) 79.5 wt % of the main-phase ceramic material A, 19.9 wt % of the auxiliary-phase ceramic material B, 0.1 wt % of WO.sub.3, and 0.5 wt % of MnO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 18 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1350 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 7

[0045] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and CoO are weighed and mixed according to the ratio of chemical formula Mg.sub.1.85Co.sub.0.25SiO.sub.4.10. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 20 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1250 C. for 2 hours to obtain the main-phase pre-calcined powder A.

[0046] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, La.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 1.20CaO.Math.0.25SrO.sub.3-0.20La.sub.2O.sub.3.Math.0.10Al.sub.2O.sub.3-1.18TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 16 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1300 C. for 4 hours to obtain auxiliary-phase pre-calcined powder B.

[0047] 3) 76.8 wt % of the main-phase ceramic material A, 22.9 wt % of the auxiliary-phase ceramic material B, and 0.3 wt % of CeO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 15 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1400 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 8

[0048] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and ZnO are weighed and mixed according to the ratio of chemical formula Mg.sub.2.02Zn.sub.0.05SiO.sub.4.07. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 16 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0049] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, Sm.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 1.15CaO.Math.0.10SrO-0.10Sm.sub.2O.sub.3.Math.0.15Al.sub.2O.sub.3-1.10TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 20 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1200 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0050] 3) 79.3 wt % of the main-phase ceramic material A, 20.2 wt % of the auxiliary-phase ceramic material B, 0.2 wt % of CeO.sub.2, and 0.3% of MnO.sub.2 are mixed. Moreover, 0.5% of CeO.sub.2 and 0.3% of MnO.sub.2 by the total mass of the main-phase A and the auxiliary-phase B are added. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 15 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1370 C. for 3 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Embodiment 9

[0051] 1) Synthesis of main-phase ceramic material A: The raw materials MgO, SiO.sub.2, and CoO are weighed and mixed according to the ratio of chemical formula Mg.sub.1.90Co.sub.0.10SiO.sub.4.00. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 20 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1250 C. for 2 hours to obtain the main-phase pre-calcined powder A.

[0052] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3, SrCO.sub.3, La.sub.2O.sub.3, Al.sub.2O.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of 1.25CaO.Math.0.25SrO-0.15Y.sub.2O.sub.3.Math.0.15Al.sub.2O.sub.3-1.08TiO.sub.2. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 20 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1300 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0053] 3) 75.7 wt % of the main-phase ceramic material A, 24.0 wt % of the auxiliary-phase ceramic material B, and 0.3 wt % of WO.sub.3 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 18 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1350 C. for 4 hours to obtain a frequency-stable low-dielectric ceramic material and its dielectric properties are tested.

Comparative Example 1

[0054] 1) Synthesis of main-phase ceramic material A: The raw materials MgO and SiO.sub.2 are weighed and mixed according to the ratio of chemical formula Mg.sub.2.00SiO.sub.4.00. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 24 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1300 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0055] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of CaTiO.sub.3. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 16 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1100 C. for 3 hours to obtain auxiliary-phase pre-calcined powder B.

[0056] 3) 85 wt % of the main-phase ceramic material A and 15 wt % of the auxiliary-phase ceramic material B are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 18 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1420 C. for 3 hours to obtain a microwave dielectric ceramic of the Comparative Example and its dielectric properties are tested.

Comparative Example 2

[0057] 1) Synthesis of main-phase ceramic material A: The raw materials MgO and SiO.sub.2 are weighed and mixed according to the ratio of chemical formula Mg.sub.2.05SiO.sub.4.00. Deionized water is added according to the ratio of mixture to deionized water 1:3, the material is mixed and ground for 24 hours, then dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1300 C. for 3 hours to obtain the main-phase pre-calcined powder A.

[0058] 2) Synthesis of auxiliary-phase ceramic material B: The raw materials CaCO.sub.3 and TiO.sub.2 are weighed and mixed according to the chemical composition of CaTiO.sub.3. Deionized water is added according to the ratio of the mixture to deionized water 1:2, the material is mixed and ground for 16 hours and dried in an oven at 120 C., ground with a quartz mortar and filtered through a 40-mesh sieve, and then the powder is put into an alumina crucible and calcined at 1300 C. for 4 hours to obtain auxiliary-phase pre-calcined powder B.

[0059] 3) 82.4 wt % of the main-phase ceramic material A, 17.3 wt % of the auxiliary-phase ceramic material B, and 0.3 wt % of CeO.sub.2 are mixed. ZrO.sub.2 balls are used as the grinding medium. Deionized water is added according to the weight ratio of mixture: zirconia balls: deionized water 1:5:1.8. After 18 hours of wet mixing, the material is dried at 120 C., and 2 wt % of polyvinyl alcohol (PVA binder) is added for grind and granulating and filtered through a 40-mesh sieve. Then, the granulated powder is pressed into a cylindrical body with a diameter of 20 mm and a height of 10 mm under a pressure of 100 MPa, and the temperature is kept at 1370 C. for 3 hours to obtain a microwave dielectric ceramic of the Comparative Example and its dielectric properties are tested.

[0060] Table 1 shows the dielectric properties of the comparative example and embodiments 1 to 9. The dielectric properties are calculated by using Agilent 8719ET network analyser. The Hakki-Coleman resonant cavity method is adopted to test the dielectric constant .sub.r and Qf values, and the frequency temperature coefficient .sub.f=(f.sub.80f.sub.25)/(f.sub.2555) is calculated and determined accordingly. f.sub.80 and f.sub.25 are the center frequencies of the sample at 80 C. and 25 C., respectively.

TABLE-US-00001 TABLE 1 Microwave dielectric properties of each embodiment No. .sub.r Q f (GHz) .sub.f (ppm/ C.) 1 9.80 63000 8 2 10.59 58000 1.79 3 11.25 53500 9.6 4 9.50 68000 16 5 10.48 59000 1.8 6 10.75 55360 2.75 7 12.36 51090 11.6 8 11.98 56900 4.8 9 13.60 45000 13 Comparative 10.30 40000 2.5 Example 1 Comparative 10.85 49700 0.50 Example 2

[0061] The Qf values of the embodiments listed in the above table are significantly improved compared with the comparative examples, and the sintering temperature is lower. It can be seen that the materials prepared by the method of the present disclosure have higher Qf values and the sintering temperature is significantly reduced. In FIG. 1, (a), (b), (c) and (d) are the scanning electron microscope photos of Comparative Example 1, Comparative Example 2, Embodiment 3 and Embodiment 6, respectively. It can be seen that the grain size of the dielectric ceramics prepared by the present disclosure is uniform with good density, and there is no abnormal growth phenomenon. FIG. 2 is a comparison chart of the temperature coefficients of 40 C. to 110 C. in Comparative Example 1, Comparative Example 2, Embodiment 5 and Embodiment 8. With reference to Comparative Example 1 and Comparative Example 2 both, it can be seen that CaTiO.sub.3 has not been modified by doping. In this case, the temperature coefficient of one side (i.e. 40 C. or 110 C.) of the full temperature range can only be adjusted to <5 ppm/ C. Comparing the comparative example with Embodiments 5 and 8, it can be seen that the modification of the auxiliary-phase ceramic B by the method of the present disclosure can significantly improve the temperature coefficient of the material in the full temperature range to within <5 ppm/ C.

[0062] It should be noted that, in the description of the present disclosure, the terms comprising, including and the like are intended to cover non-exclusive inclusion, and also include processes, methods and raw materials of other elements not explicitly listed. An embodiment or a specific embodiment and the like means that a particular feature, structure, material, or feature described in connection with the embodiment is included in at least one embodiment of the present disclosure.

[0063] Therefore, although specific embodiments have been used to describe the disclosure above, it should be understood that the above embodiments are used to understand the method and core matters of the present disclosure, and should not be construed as a limitation of the present disclosure. Those skilled in the art can change, modify, replace and modify the above embodiments within the scope of the present disclosure without departing from the principle and purpose of the present disclosure. Any simple modification, equivalent change and modification of the present disclosure shall be regarded as falling with the scope to be protected by the present disclosure.