Cordierite glass ceramic with low dielectric constant and low dielectric loss and preparation method thereof

Abstract

The invention discloses cordierite glass ceramics with low dielectric constant and low dielectric loss. The chemical formula of the cordierite glass ceramics is MgO-Al2O3-SiO2-MnO2-ZnO or MgO-Al2O3-SiO2-GeO2. The invention further discloses a preparation method of the cordierite glass ceramics. MnO2-ZnO or GeO2 is added into the cordierite crystal structure material as a nucleation agent, so that low dielectric constant and low dielectric loss can be realized while the requirement of low-temperature co-firing is met. The invention also discloses a preparation method of the cordierite microcrystalline glass with low dielectric constant and low dielectric loss, the whole method is optimized, the sintering temperature is low, and the obtained cordierite microcrystalline glass has low dielectric constant and low dielectric loss and has optimal dielectric properties.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric ceramics, and particularly to cordierite glass-ceramics with both low dielectric constant and low dielectric loss and a preparation method thereof. Background Art

[0002] With the rapid progress of modern technology, the traditional high-temperature co-fired ceramic technology can no longer meet the requirements of portability, integration and high reliability of electronic components. The emergence of LTCC material technology provides strong technical support for electronic components. In order to adapt to high-frequency application scenarios, researching and developing LTCC substrate materials with better temperature stability, smaller dielectric loss and lower sintering temperature, and realizing miniaturization and high-density integration of LTCC components are the future development directions of LTCC technology.

[0003] Chinese Patent No. CN104310980A, published on January 28, 2015, discloses a microwave dielectric ceramic material and a preparation method thereof. The chemical formula of the ceramic material is (1-x)Mg2Al4Si5O 18 -xTiO2, where 0 < x ≤ 0.35. The preparation method is to weigh the oxides of each element according to the chemical formula, synthesize Mg2Al4Si5O 18 ceramic material; then weigh the powder TiO2 raw material, mix and grind it evenly, dry it, add a binder, granulate and sieve it, then press it into a shape, sinter it into porcelain at high temperature under normal pressure, and obtain the ceramic material after temperature control and cooling. The dielectric constant of this material is 6.1 - 7.1, with a relatively high dielectric constant, and at the same time, the sintering temperature is 1350 - 1450 °C, with a high sintering temperature, which thus limits its application in the LTCC field. Summary of the Invention

[0004] The present invention is to solve the above problems existing in the microwave dielectric ceramic material and preparation method of the prior art, and provides cordierite glass-ceramics with both low dielectric constant and low dielectric loss.

[0005] The present invention also provides a preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss, with simple technological steps and a low sintering temperature.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The cordierite glass-ceramics with both low dielectric constant and low dielectric loss of the present invention has a chemical formula of MgO - Al2O3 - SiO2 - MnO2 - ZnO or MgO - Al2O3 - SiO2 - GeO2.

[0007] A preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss includes the following steps: (1)Ingredients: Accurately weigh the corresponding masses of MgO, Al2O3, Si2O3, MnO2, and ZnO as raw materials according to the molar ratio of Mg:Al:Si:Mn:Zn of 2:3.7:5:0.15:0.15, or accurately weigh the corresponding masses of MgO, Al2O3, Si2O3, and GeO2 as raw materials according to the molar ratio of Mg:Al:Si:Ge of 2:3.8:5:0.1.

[0008] (2)Mixing: Mix MgO, Si2O3, Al2O3, MnO2, and ZnO to obtain mixture I; or mix MgO, Al2O3, Si2O3, and GeO2 to obtain mixture II.

[0009] (3)Primary ball milling: Load mixture I or mixture II into a ball milling tank, add anhydrous ethanol for ball milling, and dry after ball milling to obtain primary ball milled material I or primary ball milled material II.

[0010] (4)Secondary ball milling: Place primary ball milled material I or primary ball milled material II in a crucible for pre - sintering, inject the melted glass melt into deionized water for cooling to obtain glass slag I or glass slag II. Load glass slag I or glass slag II into a ball milling tank, add anhydrous ethanol for ball milling, and dry after ball milling to obtain secondary ball milled material I or secondary ball milled material II.

[0011] (5)Granulation and tabletting: After screening secondary ball milled material I or secondary ball milled material II, add a binder to secondary ball milled material I or secondary ball milled material II, fully grind and then screen. Place the screened secondary ball milled material I or secondary ball milled material II in a mold for pressing to obtain cylindrical green body I or cylindrical green body II. The addition amount of the binder can be selected as required.

[0012] (6)Sintering: First heat cylindrical green body I from room temperature to 650 °C and hold for 4 h, then heat to 925 °C and hold for 2 h, and finally cool to 800 °C and cool naturally to obtain cordierite glass - ceramics (MASMZ); or first heat cylindrical green body II from room temperature to 650 °C and hold for 4 h, then heat to 950 °C and hold for 2 h, and finally cool to 800 °C and cool naturally to obtain cordierite glass - ceramics (MASG).

[0013] Preferably, in step (1), the MgO is calcined before weighing, the calcination temperature is 900 °C, and the calcination time is 2 h. Calcination is carried out to decompose the basic magnesium carbonate formed by water absorption. Heat to 650 °C and hold for degumming (removing PVA).

[0014] Preferably, in step (1), the Al2O3, MnO 2、Both Si2O3 and GeO2 were dried before weighing. The drying temperature was 80 °C and the drying time was 24 h. Drying was carried out to remove adsorbed moisture to ensure the accuracy of weighing.

[0015] Preferably, in step (3), the drying temperature is 80 °C and the drying time is 24 h.

[0016] Preferably, in step (4), the pre-sintering temperature is 1500 °C and the pre-sintering time is 2 h; the drying temperature is 80 °C and the drying time is 24 h.

[0017] Preferably, in step (5), the binder is a 5-10 wt% PVA solution; the pressing pressure is 80-100 MPa, and the height of the cylindrical green body I or the cylindrical green body II is 5 mm and the diameter is 12 mm.

[0018] Preferably, in step (6), first heat the cylindrical green body I from room temperature to 650 °C at a rate of 3 °C / min and hold for 4 h, then heat it to 925 °C at a rate of 5 °C / min and hold for 2 h, and finally cool it to 800 °C at a rate of 3 °C / min and then cool it naturally to obtain cordierite glass-ceramics; or first heat the cylindrical green body II from room temperature to 650 °C at a rate of 3 °C / min and hold for 4 h, then heat it to 950 °C at a rate of 5 °C / min and hold for 2 h, and finally cool it to 800 °C at a rate of 3 °C / min and then cool it naturally to obtain cordierite glass-ceramics.

[0019] Therefore, the present invention has the following beneficial effects: (1) Cordierite glass-ceramics with both low dielectric constant and low dielectric loss are provided. MnO2-ZnO or GeO2 is added as a nucleating agent in the cordierite-type crystal structure material, which can achieve both low dielectric constant and low dielectric loss while meeting the requirements of low-temperature co-firing. (2) A preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss is provided. The whole method is optimized, the sintering temperature is low, and the obtained cordierite glass-ceramics have both low dielectric constant and low dielectric loss, and have the best dielectric properties. Specific Embodiments

[0020] The following further describes the present invention in conjunction with specific embodiments.

[0021] Dielectric performance test method: Refer to the resonant cavity and vector network analyzer cylindrical resonant cavity method of the Hakki-Coleman microwave dielectric ceramic performance test to evaluate the microwave dielectric properties of the ceramic sample. The test process is: place the sample in the middle of the two metal feeder probes on both sides of the metal cavity of the test fixture, then generate electromagnetic field micro-perturbations by tuning the spiral precession probe on the metal cavity cover, find the resonant peak to determine the frequency of the medium that needs to be measured at the resonant peak, and read the center frequency and quality factor corresponding to the resonant peak; then enter the specific information of the sample in the test software, and the software will automatically complete the calculation of εr and tanδ. The measurement of τf requires the sample to be kept at room temperature and 85°C for a certain period of time, then record its resonant frequency (f value), and finally calculate the τf value.

[0022] Example 1 (1) Ingredients: Accurately weigh the corresponding masses of MgO, Al2O3, Si2O3, MnO2, and ZnO as raw materials according to the molar ratio of Mg:Al:Si:Mn:Zn of 2:3.7:5:0.15:0.15; MgO is calcined before weighing at 900°C for 2 h; Al2O3, Si2O3, and MnO2 are dried before weighing at 80°C for 24 h.

[0023] (2) Mixing: Mix MgO, Si2O3, Al2O3, MnO2 and ZnO to obtain mixed material I; (3) Primary ball milling: Place the mixed material I into a ball milling jar, add anhydrous ethanol for ball milling, and dry the mixture after ball milling to obtain primary ball mill material I.

[0024] (4) Secondary ball milling: The primary ball mill material I is placed in a crucible for pre-sintering at a temperature of 1500°C for 2 h. The molten glass is poured into deionized water for cooling to obtain glass slag I. The glass slag I is placed in a ball mill jar and anhydrous ethanol is added for ball milling. After ball milling, the material is dried to obtain secondary ball mill material I.

[0025] (5) Granulation and tableting: After the secondary ball mill material I is sieved, a binder (10 wt% PVA solution) is added to the secondary ball mill material I. After sufficient grinding, the sieved secondary ball mill material I is placed in a mold for pressing at a pressing pressure of 100 MPa to obtain a cylindrical green body I with a height of 5 mm and a diameter of 12 mm.

[0026] (6) Sintering: First, the green cylindrical blank Ⅰ is heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 925 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then cooled naturally to obtain cordierite glass-ceramics (MgO-Al2O3-SiO2-MnO2-ZnO). The dielectric properties of the obtained cordierite glass-ceramics are tested, and it is measured that: the dielectric constant is 4.74, and the dielectric loss is 0.81×10 -3 , and the temperature coefficient of resonant frequency is -15 ppm / / °C.

[0027] Comparative Example 1 Compared with Example 1, the difference in Comparative Example 1 is that: in step (6), the green cylindrical blank Ⅰ is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 900 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then cooled naturally to obtain cordierite glass-ceramics, and the rest is the same as in Example 1. The dielectric properties of the obtained cordierite glass-ceramics are tested, and it is measured that: the dielectric constant is 4.60, and the dielectric loss is 0.91×10 -3 , and the temperature coefficient of resonant frequency is -14 ppm / °C.

[0028] Comparative Example 2 Compared with Example 1, the difference in Comparative Example 2 is that: in step (6), the green cylindrical blank Ⅰ is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 950 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then cooled naturally to obtain cordierite glass-ceramics, and the rest is the same as in Example 1. The dielectric properties of the obtained cordierite glass-ceramics are tested, and it is measured that: the dielectric constant is 4.71, and the dielectric loss is 0.86×10 -3 , and the temperature coefficient of resonant frequency is -22 ppm / °C.

[0029] Comparative Example 3 Compared with Example 1, the difference in Comparative Example 3 is that: in step (6), the green cylindrical blank Ⅰ is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 975 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then cooled naturally to obtain cordierite glass-ceramics, and the rest is the same as in Example 1. The dielectric properties of the obtained cordierite glass-ceramics are tested, and it is measured that: the dielectric constant is 4.63, and the dielectric loss is 0.91×10 -3 , and the temperature coefficient of resonant frequency is -30 ppm / °C.

[0030] Comparative Example 4 Comparative Example 4 is different from Example 1 in that: in step (6), the green body Ⅰ of the cylinder is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 1000 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics, and the rest is the same as in Example 1. The dielectric properties of the obtained cordierite glass-ceramics were tested, and it was measured that: the dielectric constant was 4.60, the dielectric loss was 0.92×10 -3 , and the temperature coefficient of resonant frequency was -26 ppm / °C.

[0031] It can be seen from Example 1 and Comparative Examples 1-4 that the cordierite glass-ceramics (MASMZ) prepared in Example 1 (at a crystallization temperature of 925 °C) have the optimal dielectric properties: εr = 4.74, tanδ = 0.81×10 -3 , τf = -15 ppm / °C.

[0032] Example 2 (1) Batch preparation: According to the molar ratio of Mg:Al:Si:Ge of 2:3.8:5:0.1, the corresponding masses of MgO, Al2O3, Si2O3, and GeO2 were accurately weighed as raw materials; MgO was calcined before weighing, the calcination temperature was 900 °C, and the calcination time was 2 h; Al2O3, Si2O3, and GeO2 were all dried before weighing, the drying temperature was 80 °C, and the drying time was 24 h.

[0033] (2) Mixing: MgO, Si2O3, Al2O3, and GeO2 were mixed to obtain mixture Ⅱ.

[0034] (3) Primary ball milling: Mixture Ⅱ was loaded into a ball mill tank, anhydrous ethanol was added for ball milling, and after ball milling, it was dried to obtain primary ball milled material Ⅱ.

[0035] (4) Secondary ball milling: The primary ball milled material Ⅱ was placed in a crucible for pre-burning, the pre-burning temperature was 1500 °C, and the pre-burning time was 2 h. The molten glass melt was poured into deionized water for cooling to obtain glass slag Ⅱ. Glass slag Ⅱ was loaded into a ball mill tank, anhydrous ethanol was added for ball milling, and after ball milling, it was dried to obtain secondary ball milled material Ⅱ.

[0036] (5) Granulation and pressing: After the secondary ball milled material Ⅱ was sieved, the binder (10 wt% PVA solution) was added to the secondary ball milled material Ⅱ, and after sufficient grinding, it was sieved. The sieved secondary ball milled material Ⅱ was placed in a mold for pressing, and the pressing pressure was 100 Mpa to obtain a cylindrical green body Ⅱ with a height of 5 mm and a diameter of 12 mm.

[0037] (6) Sintering: First, the green body II of the cylinder is heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 950 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics (MgO-Al2O3-SiO2-GeO2). The dielectric properties of the obtained cordierite glass-ceramics were tested, and it was measured that: the dielectric constant was 4.46, the dielectric loss was 1.11×10 -3 , and the temperature coefficient of resonant frequency was -27 ppm / °C.

[0038] Comparative Example 5 Compared with Example 2, the difference in Comparative Example 5 is that: in step (6), the green body II of the cylinder is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 900 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics, and the rest is the same as in Example 2. The dielectric properties of the obtained cordierite glass-ceramics were tested, and it was measured that: the dielectric constant was 4.36, the dielectric loss was 1.32×10 -3 , and the temperature coefficient of resonant frequency was -32 ppm / °C.

[0039] Comparative Example 6 Compared with Example 2, the difference in Comparative Example 6 is that: in step (6), the green body II of the cylinder is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 925 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics, and the rest is the same as in Example 2. The dielectric properties of the obtained cordierite glass-ceramics were tested, and it was measured that: the dielectric constant was 4.41, the dielectric loss was 1.25×10 -3 , and the temperature coefficient of resonant frequency was -27 ppm / °C.

[0040] Comparative Example 7 Compared with Example 2, the difference in Comparative Example 7 is that: in step (6), the green body II of the cylinder is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 975 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics, and the rest is the same as in Example 2. The dielectric properties of the obtained cordierite glass-ceramics were tested, and it was measured that: the dielectric constant was 4.42, the dielectric loss was 1.17×10 -3 , and the temperature coefficient of resonant frequency was -29 ppm / °C.

[0041] Comparative Example 8 Comparative Example 8 is different from Example 2 in that: in step (6), the green body II of the cylinder is first heated from room temperature to 650 °C at a rate of 3 °C / min and held for 4 h, then heated to 1000 °C at a rate of 5 °C / min and held for 2 h, and finally cooled to 800 °C at a rate of 3 °C / min and then naturally cooled to obtain cordierite glass-ceramics, and the rest is the same as in Example 2. The dielectric properties of the obtained cordierite glass-ceramics were tested and measured as follows: the dielectric constant was 4.38, and the dielectric loss was 1.27×10 -3 , and the temperature coefficient of resonant frequency was -31 ppm / °C.

[0042] It can be seen from Example 2 and Comparative Examples 5-8 that the cordierite glass-ceramics (MASG) prepared in Example 2 (at a crystallization temperature of 950 °C) have the best dielectric properties: εr = 4.46, tanδ = 1.11×10 -3 , τf = -27 ppm / °C.

[0043] The dielectric properties of the cordierite glass-ceramics (MASMZ) prepared in Example 1, the cordierite glass-ceramics (MASG) prepared in Example 2, and other cordierite glass-ceramics of the same type prepared by the same method (with different crystallization temperatures, selecting their respective optimal crystallization temperatures and the rest being the same) were tested, and the measured results are shown in Table 1.

[0044] Table 1 Dielectric property test results of Example 1, Example 2 and other cordierite glass-ceramics of the same type

[0045] It can be seen from Table 1 that the cordierite glass-ceramics prepared in Example 1 and Example 2 have better dielectric properties than other cordierite glass-ceramics of the same type.

[0046] The above-described embodiments are only a preferred solution of the present invention and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. Cordierite glass-ceramics with both low dielectric constant and low dielectric loss, characterized in that, Its chemical formula is MgO-Al2O3-SiO2-MnO2-ZnO or MgO-Al2O3-SiO2-GeO2.

2. A method for preparing cordierite glass-ceramics with both low dielectric constant and low dielectric loss as described in claim 1, characterized in that, The following steps are involved: (1) Ingredients: According to the molar ratio of Mg:Al:Si:Mn:Zn of 2:3.7:5:0.15:0.15, accurately weigh the corresponding mass of MgO, Al2O3, Si2O3, MnO2, and ZnO as raw materials, or according to the molar ratio of Mg:Al:Si:Ge of 2:3.8:5:0.1, accurately weigh the corresponding mass of MgO, Al2O3, Si2O3, and GeO2 as raw materials; (2) Mixing: Mix MgO, Si2O3, Al2O3, MnO2 and ZnO to obtain mixed material I; or mix MgO, Al2O3, Si2O3 and GeO2 to obtain mixed material II; (3) Primary ball milling: put the mixed material I or the mixed material II into a ball milling jar, add anhydrous ethanol for ball milling, and dry after ball milling to obtain primary ball milling material I or primary ball milling material II; (4) Secondary ball milling: placing the primary ball mill material I or the primary ball mill material II in a crucible for pre-sintering, injecting the molten glass into deionized water for cooling to obtain glass slag I or glass slag II, placing the glass slag I or glass slag II in a ball milling jar, adding anhydrous ethanol for ball milling, and drying after ball milling to obtain secondary ball mill material I or secondary ball mill material II; (5) Granulation and tableting: After sieving the secondary ball mill material I or the secondary ball mill material II, a binder is added to the secondary ball mill material I or the secondary ball mill material II, and the secondary ball mill material I or the secondary ball mill material II is fully ground and sieved. The sieved secondary ball mill material I or the secondary ball mill material II is placed in a mold for pressing to obtain a cylindrical green body I or a cylindrical green body II; (6) Sintering: The cylindrical green body I is first heated from room temperature to 650°C and then kept at this temperature for 4 h, then heated to 925°C and kept at this temperature for 2 h, and finally cooled to 800°C and naturally cooled to obtain cordierite glass-ceramics; or the cylindrical green body II is first heated from room temperature to 650°C and then kept at this temperature for 4 h, then heated to 950°C and kept at this temperature for 2 h, and finally cooled to 800°C and naturally cooled to obtain cordierite glass-ceramics.

3. The method for preparing cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, characterized in that, In step (1), the MgO is calcined before weighing, with the calcination temperature being 900° C. and the calcination time being 2 h.

4. The preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, characterized in that, In step (1), the Al2O3, MnO2, Si2O3 and GeO2 are dried before weighing, with the drying temperature being 80°C and the drying time being 24h.

5. The preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, characterized in that, In step (3), the drying temperature is 80°C and the drying time is 24 hours.

6. The preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, wherein, In step (4), the pre-firing temperature is 1500°C and the pre-firing time is 2h; the drying temperature is 80°C and the drying time is 24h.

7. The preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, characterized in that, In step (5), the binder is a 5-10 wt% PVA solution; the pressing pressure is 80-100 MPa, and the height of the cylindrical green body I or the cylindrical green body II is 5 mm and the diameter is 12 mm.

8. The preparation method of cordierite glass-ceramics with both low dielectric constant and low dielectric loss according to claim 2, characterized in that, In step (6), first heat the green body Ⅰ of the cylinder from room temperature to 650 °C at a rate of 3 °C / min and hold for 4 h, then heat it to 925 °C at a rate of 5 °C / min and hold for 2 h, and finally cool it to 800 °C at a rate of 3 °C / min and then cool it naturally to obtain cordierite glass-ceramics; or first heat the green body Ⅱ of the cylinder from room temperature to 650 °C at a rate of 3 °C / min and hold for 4 h, then heat it to 950 °C at a rate of 5 °C / min and hold for 2 h, and finally cool it to 800 °C at a rate of 3 °C / min and then cool it naturally to obtain cordierite glass-ceramics.

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