A preparation method of LiBaF3 microwave dielectric ceramics

Abstract

The invention discloses a LiBaF 3 The preparation method of microwave dielectric ceramics relates to the field of microwave communication and the field of low-temperature co-fired ceramic dielectric materials, including LiF and BaF 2 The powders were placed in a heating furnace for primary calcination, primary grinding, primary drying, secondary calcination, secondary grinding, secondary drying, and sieving granulation; the obtained powder raw materials were pressed into cylinders and cold isostatically pressed; and finally sintered for 2 hours to achieve densification to obtain densified LiBaF 3 ; In the present invention, LiBaF 3 The preparation method of microwave dielectric materials can achieve densification at a lower temperature; under this preparation condition, LiBaF 3 Microwave dielectric ceramics have a low dielectric constant of 13.72, a high quality 73000GHz and a near-zero resonant frequency temperature coefficient of ‑35.74×10 ‑6 / ℃; at the same time, the LiBaF 3 Microwave dielectric ceramics can coexist with Ag at low temperatures and are a new type of microwave dielectric material with great application potential.

Description

Technical Field

[0001] The invention relates to the field of microwave communication and low-temperature co-fired ceramic dielectric materials, and in particular to a method for preparing LiBaF3 microwave dielectric ceramics. Background Art

[0002] Microwave communication technology plays an extremely important role in contemporary information technology and has extensive and in-depth applications in military, civil communications, satellite communications, aerospace and other fields. With the advent of the 5G / 6G era, the communication carrier frequency will expand from microwave to millimeter wave region or even higher. In such high-frequency communications, signal delay has become the primary problem that needs to be solved. Signal delay time is related to dielectric constant (ε r ), the use of materials with lower dielectric constants can significantly increase the propagation speed of radio signals; high quality factor (Q×f) can reduce signal loss and crosstalk risk during signal transmission and improve its frequency selection characteristics; near-zero resonant frequency temperature coefficient (τ f ) shows that the material has good thermal stability and can better adapt to the application environment of complex temperature field; in addition, low temperature co-fired ceramic technology (LTCC) is considered to be an effective method to achieve miniaturization and circuit integration of next-generation communication system modules; with the increase of application frequency, circuit loss gradually dominates the communication system, and low resistivity Ag and Cu electrodes can significantly reduce the loss in the signal propagation process, thereby increasing the signal transmission speed; therefore, in order to meet the requirements of high-frequency communication technologies such as 5G / 6G, it is of great significance to propose some new microwave dielectric materials with low dielectric constant, high quality factor and near-zero resonant frequency temperature coefficient that can be prepared by LTCC technology. Summary of the invention

[0003] In order to solve the above technical problems, the technical solution provided by the present invention is: a method for preparing LiBaF3 microwave dielectric ceramics, comprising the following steps:

[0004] (1) LiF and BaF 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein;

[0005] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder is ground once to ensure a uniform mix;

[0006] (3) placing the uniformly mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol;

[0007] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ;

[0008] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium to grind the calcined powder;

[0009] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter;

[0010] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0011] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0012] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0013] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0014] The advantages of the present invention compared with the prior art are: 3 The preparation method of microwave dielectric materials can achieve densification (~97%) at a relatively low temperature (625°C); under this preparation condition, LiBaF 3 Microwave dielectric ceramics have a low dielectric constant of 13.72, a high quality 73000GHz and a near-zero resonant frequency temperature coefficient of -35.74×10 -6 / ℃; at the same time, the LiBaF 3 Microwave dielectric ceramics can coexist with Ag at low temperatures (650°C) and are a new type of microwave dielectric material with great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The LiBaF calcined at 300°C-700°C in the present invention 3 XRD results of powders.

[0016] Figure 2 The LiBaF prepared at a sintering temperature of 600°C-675°C in the present invention 3 XRD results of ceramics.

[0017] Figure 3 LiBaF prepared at different sintering temperatures in the present invention 3 Density and relative density of ceramics.

[0018] Figure 4 LiBaF prepared under different sintering conditions in the present invention 3 Microwave dielectric properties of ceramics. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention.

[0020] Embodiment 1:

[0021] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0022] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0023] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0024] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0025] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Among them, the calcination temperature is 300℃ and the calcination time is 4 hours.

[0026] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0027] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0028] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0029] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0030] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0031] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0032] Embodiment 2:

[0033] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0034] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0035] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0036] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0037] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Wherein, the calcination temperature is 700°C and the calcination time is 4 hours;

[0038] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0039] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0040] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0041] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0042] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0043] (10) The densified LiBaF3 is polished for subsequent testing.

[0044] Embodiment 3:

[0045] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0046] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0047] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0048] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0049] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Wherein, the calcination temperature is 600°C and the calcination time is 4 hours;

[0050] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0051] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0052] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0053] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0054] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0055] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0056] Embodiment 4:

[0057] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0058] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0059] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0060] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0061] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Wherein, the calcination temperature is 625°C and the calcination time is 4 hours;

[0062] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0063] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0064] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0065] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0066] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0067] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0068] Embodiment 5:

[0069] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0070] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0071] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0072] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0073] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Wherein, the calcination temperature is 650°C and the calcination time is 4 hours;

[0074] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0075] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0076] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0077] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0078] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0079] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0080] Embodiment 6:

[0081] A method for preparing LiBaF3 microwave dielectric ceramics comprises the following steps:

[0082] (1) Select LiF and BaF with a purity of 99.99% 2 The powders are placed in a heating furnace for calcination to remove volatile impurities and water vapor therein; wherein the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours;

[0083] (2) LiF and BaF 2 The powders were weighed at a molar ratio of 1:1 and anhydrous ethanol was used as the grinding medium to grind LiF and BaF. 2 The powder was ground once for 4 hours to ensure uniform mixing;

[0084] (3) placing the uniformly mixed mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0085] (4) The mixture material obtained in step (3) is placed in a heating furnace again for secondary calcination to obtain the main phase LiBaF 3 ; Wherein, the calcination temperature is 675°C and the calcination time is 4 hours;

[0086] (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium for 4 hours;

[0087] (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; wherein the temperature of the drying oven is 100° C. and the drying time is 4 hours;

[0088] (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size;

[0089] (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body;

[0090] (9) Sintering the ceramic obtained in step (8) at 600-675° C. in air atmosphere for 2 hours to achieve densification, thereby obtaining a densified LiBaF 3 ;

[0091] (10) Densified LiBaF 3 Polishing is performed for subsequent testing.

[0092] 1. Test Results

[0093] (1) Figure 1 As shown, Figure 1 LiBaF calcined at 300-700℃ 3 The XRD results of the powder show that with the increase of calcination temperature, the impurity phase gradually disappears, and only a very weak impurity peak remains at 600°C.

[0094] like Figure 2 As shown, Figure 2 LiBaF is prepared at a sintering temperature of 600℃-675℃ 3 The XRD results of the ceramics show that single-phase LiBaF can be obtained within this sintering temperature range. 3 Ceramic material.

[0095] (2) Figure 3 As shown, Figure 3 LiBaF prepared at different sintering temperatures 3 The density and relative density of the ceramics show that the density of the ceramic material is the highest under sintering conditions at 625℃.

[0096] (3) Figure 4 As shown, Figure 4 LiBaF prepared under different sintering conditions3 Microwave dielectric properties of ceramics. With the increase of sintering temperature, the dielectric constant and quality factor first increase and then decrease, and the temperature coefficient of resonance frequency gradually increases and approaches zero; at 625℃, the dielectric constant, quality factor and temperature coefficient of resonance frequency of the ceramic are 13.72, 73000GHz and -35.74×10 -6 / ℃. LiBaF prepared by LTCC technology 3 The new ceramic material is a promising microwave dielectric material.

[0097] Compared with other current LTCC technologies: LiBaF 3 The densification temperature of the ceramic (625°C) is significantly lower than the sintering temperature used in most LTCC technologies, which is more conducive to reducing production costs and energy consumption, avoiding warping and cracking of the substrate, ensuring dimensional stability, improving reliability, and achieving co-firing with low-melting-point metal conductors (such as Cu, Ag, etc.), facilitating metal wiring and device integration; in addition, compared with the widely reported microwave dielectric ceramics of vanadate, molybdate and borate systems, the LiBaF3 ceramics proposed in the present invention have better comprehensive dielectric properties; for example, Ba prepared at 660°C 3 Zn(V 2 O 7 ) 2 The ceramic has a dielectric constant of 10.3, a quality factor of 43400GHz, and a resonant frequency temperature coefficient of -46.87ppm / ℃; Li prepared at 650℃ 2 Mg 2 Mo 3 O 12 The ceramic has a dielectric constant of 9.3, a quality factor of 58583GHz, and a resonant frequency temperature coefficient of -51ppm / ℃; Li prepared at 640℃ 6 B 4 O 9 The LiBaF3 ceramic has a dielectric constant of 5.9, a quality factor of 41800GHz, and a resonant frequency temperature coefficient of -72ppm / ℃. In summary, the LiBaF3 ceramic proposed in this technology has certain microwave dielectric performance advantages. Finally, LiBaF 3 The ceramic system has high room temperature stability and can coexist with Ag at low temperatures, making it a potential LTCC application material.

[0098] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for preparing LiBaF3 microwave dielectric ceramics, characterized in that: The following steps are involved: (1) LiF and BaF2 powders are placed in a heating furnace and calcined to remove volatile impurities and water vapor; (2) LiF and BaF2 powders were weighed in a molar ratio of 1:1, and the LiF and BaF2 powders were ground once using anhydrous ethanol as a grinding medium to ensure uniform mixing; (3) placing the uniformly mixed material obtained in step (2) in a drying oven for primary drying to remove anhydrous ethanol; (4) placing the mixture material obtained in step (3) into the heating furnace again for secondary calcination to obtain the main phase LiBaF3; (5) grinding the mixed material obtained in step (4) for a second time using anhydrous ethanol as a grinding medium to grind the calcined powder; (6) placing the mixed material obtained in step (5) into a drying oven for secondary drying to remove organic matter; (7) sieving and granulating the mixed fraction obtained in step (6) through a 100-mesh sieve to obtain a powder raw material with a relatively uniform particle size; (8) pressing the powder raw material obtained in step (7) into a cylinder with a diameter of 10 mm at a pressure of 150 MPa, and then cold isostatically pressing at a pressure of 200 MPa for 30 seconds to obtain a ceramic body; (9) sintering the ceramic obtained in step (8) at 600-675° C. in an air atmosphere for 2 hours to achieve densification, thereby obtaining densified LiBaF 3 ; (10) The densified LiBaF3 is polished for subsequent testing.

2. The method for preparing a LiBaF3 microwave dielectric ceramic according to claim 1, characterized in that: The LiF and BaF2 raw materials selected in the step (1) have a purity of 99.99%.

3. The method for preparing a LiBaF3 microwave dielectric ceramic according to claim 1, characterized in that: In the step (1), the calcination temperature of the heating furnace is 500° C. and the calcination time is 2 hours.

4. The method for preparing a LiBaF3 microwave dielectric ceramic according to claim 1, characterized in that: The time for the first grinding in step (2) and the second grinding in step (5) is 4 hours.

5. The method for preparing a LiBaF3 microwave dielectric ceramic according to claim 1, characterized in that: In the primary drying in step (3) and the secondary drying in step (6), the temperature of the drying oven is 100° C. and the drying time is 4 hours.

6. The method for preparing a LiBaF3 microwave dielectric ceramic according to claim 1, characterized in that: The secondary calcination in step (4) is carried out at a temperature of 300-700° C. and for a time of 4 hours.

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