CN111138187A - Barium strontium titanate textured ceramic formed by water-based gel tape casting and preparation method thereof - Google Patents
Barium strontium titanate textured ceramic formed by water-based gel tape casting and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a barium strontium titanate textured ceramic formed by water-based gel tape casting, and relates to the technical field of electronic materials. The barium strontium titanate textured ceramic comprises barium strontium titanate powder and barium strontium titanate flaky seed crystals, and the barium strontium titanate flaky seed crystals are directionally arranged in the barium strontium titanate powder along the casting direction under the casting process to form ceramic with a textured structure; the relative density is 95-98%, the texture degree is 55-90%, the dielectric constant is 8000-11000, the dielectric loss is 0.005-0.04, and the dielectric adjustability is 40-60%; the invention also provides a preparation method of the barium strontium titanate textured ceramic formed by the water-based gel tape casting. The invention utilizes the combination of the flaky barium strontium titanate seed crystals and the barium strontium titanate powder to ensure that the flaky barium strontium titanate seed crystals are directionally arranged in the barium strontium titanate powder along the casting direction under the casting process, thereby improving the orientation of the ceramic material and simultaneously achieving the aim of improving the dielectric property of the ceramic material.
Description
Technical Field
The invention relates to the technical field of electronic materials, in particular to a barium strontium titanate textured ceramic formed by aqueous gel tape casting and a preparation method thereof.
Background
Barium strontium titanate is a solid solution formed by strontium titanate (SrTiO3) and barium titanate (BaTiO3) with a typical perovskite structure, has the advantages of high dielectric tunability, high insulation resistance, low dielectric loss and high capacitance temperature stability, and can adjust the dielectric constant and Curie temperature of a material in a wide range by changing the barium/strontium (Ba/Sr) molar ratio of the material. At present, people have made ferroelectric material phase shifters with barium strontium titanate, but for large-scale application, the dielectric tunability is still low, limiting the further development of the phase shifters. Therefore, the barium strontium titanate textured ceramic and the preparation method thereof are provided, and have important significance for improving the dielectric tunability of barium strontium titanate.
Disclosure of Invention
The invention aims to solve the problems of complicated preparation process and high requirement on preparation equipment of barium strontium titanate in the background technology, and provides a barium strontium titanate textured ceramic formed by aqueous gel casting and a preparation method thereof.
The barium strontium titanate flaky seed crystals are combined with the barium strontium titanate powder, and the flaky barium strontium titanate seed crystals are directionally arranged in the barium strontium titanate powder along the casting direction under the casting process, so that the orientation of the ceramic material is improved, and the purpose of improving the dielectric property of the ceramic material can be achieved.
The first purpose of the invention is to provide a barium strontium titanate textured ceramic formed by water-based gel tape casting, which comprises barium strontium titanate powder and barium strontium titanate flaky seed crystals, wherein the barium strontium titanate flaky seed crystals are directionally arranged in the barium strontium titanate powder along the tape casting direction under the tape casting process to form ceramic with texture tissues; the relative density is 95-98%, the texture degree is 55-90%, the dielectric constant is 8000-11000, the dielectric loss is 0.005-0.04, and the dielectric adjustability is 40-60%.
The second purpose of the invention is to provide a preparation method of barium strontium titanate textured ceramic formed by water-based gel tape casting, which comprises the following steps:
s1, respectively weighing barium strontium titanate powder, deionized water, a dispersing agent and a plasticizer, mixing and ball-milling for 24-48 h, then adding barium strontium titanate flaky seed crystals, and continuing ball-milling for 0.5-1 h to obtain barium strontium titanate slurry;
wherein the mass ratio of the barium strontium titanate powder to the deionized water to the dispersant to the plasticizer is 100: 30-60: 5-15: 4-12; the adding amount of the barium strontium titanate flaky seed crystals is 20-100% of the mass of the barium strontium titanate powder;
s2, performing vacuum degassing on the barium strontium titanate slurry obtained in the S1, then performing tape casting, and drying at room temperature after molding to obtain a barium strontium titanate film blank; wherein the thickness of the prepared barium strontium titanate film blank is 0.1-0.2 mm;
s3, after laminating the barium strontium titanate film blank obtained in the S2, carrying out hot water pressure equalization to obtain a blocky barium strontium titanate ceramic blank;
and S4, carrying out binder removal and sintering on the blocky barium strontium titanate ceramic blank obtained in the S3 to obtain the textured barium strontium titanate ceramic.
Preferably, the barium strontium titanate powder is amorphous Ba0.6Sr0.4TiO3Powder having an average particle diameter of 0.5. mu.m.
Preferably, the barium strontium titanate flaky seed crystal is flaky Ba prepared by a molten salt method0.6Sr0.4TiO3And a seed crystal having a thickness of 0.5 μm and a radial length of 10 μm.
Preferably, the dispersant is a copolymer of isobutylene and maleic acid glycoside.
Preferably, the plasticizer is polyethylene glycol 600.
Preferably, in the process of tape casting, the gap between the tape casting knife and the steel belt is adjusted to be 150-300 mu m, and the rotation number of the steel belt is 300-400 r/min.
Preferably, the barium strontium titanate film blank lamination is to laminate 30-50 layers of barium strontium titanate film blanks to 2-3 mm, and the lamination pressure is 2-10 MPa.
Preferably, the gel is discharged by heat preservation at 380 ℃ for 2 hours.
Preferably, the sintering is carried out at the temperature of 1350-1450 ℃ for 5-20 h.
Compared with the prior art, the invention has the beneficial effects that:
(1) the water-based gel tape casting formed barium strontium titanate textured ceramic provided by the invention has the advantages that the relative density is 95-98%, the texture degree is 55-90%, the dielectric constant is 8000-11000, the dielectric loss is 0.005-0.04, and the dielectric adjustability is 40-60%.
(2) According to the water-based gel tape casting formed barium strontium titanate textured ceramic, the flaky barium strontium titanate seed crystals are combined with the barium strontium titanate powder, and are directionally arranged in the barium strontium titanate powder along the tape casting direction under the tape casting process, so that the purpose of improving the dielectric property of the ceramic material can be achieved while the orientation of the ceramic material is improved.
Drawings
FIG. 1 is an XRD pattern of a BST sample containing 5 wt% seed crystals after 5h of sintering soak time in example 1;
wherein, fig. 1a is an XRD pattern of barium strontium titanate ceramic perpendicular to the casting direction; FIG. 1b is an XRD pattern of barium strontium titanate ceramic parallel to the casting direction.
Fig. 2 is an SEM photograph parallel to the casting direction of the barium strontium titanate textured ceramic prepared in example 1.
Fig. 3 is an SEM photograph of the barium strontium titanate textured ceramic prepared in example 1, perpendicular to the casting direction.
Detailed Description
In order to make the technical solutions of the present invention better understood and implemented by those skilled in the art, the present invention is further described below with reference to the following specific embodiments and the accompanying drawings, but the embodiments are not meant to limit the present invention.
It should be noted that the experimental methods described in the following examples are all conventional methods unless otherwise specified;
barium strontium titanate powder is purchased from Shanghai Dian Yang industry Co., Ltd;
the barium strontium titanate flaky seed crystal is synthesized by a two-step molten salt method: in the first step, bismuth trioxide, titanium dioxide, sodium chloride and potassium chloride are used for synthesizing flaky bismuth titanate (Bi) by a molten salt method at 1000 DEG C4Ti3O12) (ii) a Secondly, bismuth titanate, barium carbonate, strontium carbonate, sodium chloride and potassium chloride are used for synthesizing barium strontium titanate flaky seed crystals by a 740 ℃ molten salt method, the thickness of the barium strontium titanate flaky seed crystals is 0.5 mu m, and the radial length of the barium strontium titanate flaky seed crystals is 10 mu m;
other reagents and materials, unless otherwise specified, are commercially available.
Example 1
Mixing 100g of barium strontium titanate powder, 30g of deionized water, 5g of dispersant and 4g of plasticizer, adding 279g of zirconium oxide grinding balls, carrying out ball milling for 24h to obtain barium strontium titanate slurry, adding 20g of barium strontium titanate flaky seed crystals into the slurry, carrying out ball milling for 30min continuously to obtain barium strontium titanate slurry, placing the slurry in a conical flask, carrying out vacuum degassing for 30min, placing the slurry on a casting machine for casting molding, carrying out tape casting at the steel tape rotation number of 300r/min and the gap between a tape casting knife and the steel tape of 300 mu m, standing and drying at room temperature for 24h to obtain a barium strontium titanate film blank sheet with the thickness of 0.1mm, laminating 50 layers of barium strontium titanate film blank sheets to 3mm, carrying out hot water pressure equalization at the laminating pressure of 10MPa to obtain a blocky barium strontium titanate ceramic blank body, placing the barium strontium titanate ceramic blank body in a muffle furnace to carry out glue discharge at the heating rate of 1 ℃/min and the heat preservation time of 2h at 380 ℃, placing the blank body after glue discharge in a sintering furnace at the heating, keeping the temperature at 1350 ℃ for 5h, and sintering to obtain textured barium strontium titanate ceramic; wherein the dispersant is a copolymer of isobutene and maleic acid glycoside; the plasticizer is polyethylene glycol 600.
The barium strontium titanate textured ceramic obtained in the embodiment has the relative density of 95%, the texture degree of 55%, the dielectric constant of 8000, the dielectric loss of 0.04 and the dielectric tunability of 40%.
Example 2
Mixing 100g of barium strontium titanate powder, 60g of deionized water, 15g of dispersing agent and 12g of plasticizer, adding 561g of zirconium oxide grinding balls, performing ball milling for 48h to obtain barium strontium titanate slurry, adding 100g of barium strontium titanate flaky seed crystals into the slurry, continuing ball milling for 30min to obtain barium strontium titanate slurry, placing the slurry in a conical flask, performing vacuum degassing for 30min, placing the slurry on a casting machine for casting molding, performing tape casting at a rotation number of 400r/min and a gap between a tape casting knife and a tape casting knife of 150 mu m, standing and drying at room temperature for 24h to obtain a barium strontium titanate film blank with a thickness of 0.2mm, laminating 30 layers of barium strontium titanate film blanks to 2mm, performing hot water pressure equalization at a laminating pressure of 2MPa to obtain a blocky barium strontium titanate ceramic blank, placing the barium strontium titanate ceramic blank in a muffle furnace to perform heat preservation for 2h at a heating rate of 1 ℃/min and 380 ℃, performing glue discharging, placing the blank after glue discharging in a sintering furnace at a heating rate of 3 ℃/min, the temperature is kept at 1450 ℃ for 20h, and the textured barium strontium titanate ceramic is obtained by sintering; wherein the dispersant is a copolymer of isobutene and maleic acid glycoside; the plasticizer is polyethylene glycol 600. The barium strontium titanate textured ceramic obtained in the embodiment has the relative density of 98%, the texture degree of 90%, the dielectric constant of 11000, the dielectric loss of 0.005 and the dielectric tunability of 60%.
Example 3
Mixing 100g of barium strontium titanate powder, 40g of deionized water, 8g of dispersant and 8g of plasticizer, adding 279g of zirconium oxide grinding balls, carrying out ball milling for 36h to obtain barium strontium titanate slurry, adding 50g of barium strontium titanate flaky seed crystals into the slurry, continuing ball milling for 30min to obtain barium strontium titanate slurry, placing the slurry in a conical flask, carrying out vacuum degassing for 30min, placing the slurry on a casting machine for casting molding, carrying out tape casting with the rotation number of a steel tape of 350r/min and the gap between a tape casting cutter and the steel tape of 200 mu m, standing and drying at room temperature for 24h to obtain a barium strontium titanate film blank with the thickness of 0.15mm, laminating 40 layers of barium strontium titanate film blanks to 2.5mm, carrying out hot water pressure equalization with the laminating pressure of 5MPa to obtain a blocky barium strontium titanate ceramic blank, placing the barium strontium titanate ceramic blank in a muffle furnace to carry out heat preservation for 2h at the heating rate of 1 ℃/min and 380 ℃ to carry out glue discharge, placing the blank after glue discharge in a sintering furnace at the heating rate of, preserving heat at 1400 ℃ for 15h, and sintering to obtain textured barium strontium titanate ceramic; wherein the dispersant is a copolymer of isobutene and maleic acid glycoside; the plasticizer is polyethylene glycol 600.
The barium strontium titanate textured ceramic obtained in the embodiment has the relative density of 96%, the texture degree of 72%, the dielectric constant of 9800, the dielectric loss of 0.02 and the dielectric tunability of 50%.
Example 4
Mixing 100g of barium strontium titanate powder, 50g of deionized water, 13g of dispersing agent and 12g of plasticizer, adding 360g of zirconium oxide grinding balls, performing ball milling for 30h to obtain barium strontium titanate slurry, adding 35g of barium strontium titanate flaky seed crystals into the slurry, performing ball milling for 30min to obtain barium strontium titanate slurry, placing the slurry in a conical flask, performing vacuum degassing for 30min, placing the slurry on a casting machine for casting molding, setting the rotation number of a steel belt to be 400r/min, setting the gap between a casting knife and the steel belt to be 300 mu m, standing and drying at room temperature for 24h to obtain barium strontium titanate film blank sheets, laminating the barium strontium titanate film blank sheets, performing hot water pressure equalization at the laminating pressure of 10MPa to obtain blocky barium strontium titanate ceramic blanks, placing the barium strontium titanate ceramic blanks in a muffle furnace to perform heat preservation at the heating rate of 1 ℃/min and at the temperature of 380 ℃ for 2h to perform adhesive removal, placing the blanks after adhesive removal in a sintering furnace at the heating rate of 3 ℃/min, the temperature is kept at 1450 ℃ for 10h, and the textured barium strontium titanate ceramic is obtained by sintering; wherein the dispersant is a copolymer of isobutene and maleic acid glycoside; the plasticizer is polyethylene glycol 600.
The barium strontium titanate textured ceramic obtained in the embodiment has the relative density of 95%, the texturing degree of 63%, the dielectric constant of 9100, the dielectric loss of 0.03 and the dielectric tunability of 47%.
Example 5
Mixing 100g of barium strontium titanate powder, 35g of deionized water, 10g of dispersing agent and 6g of plasticizer, adding 279g of zirconium oxide grinding balls, performing ball milling for 48h to obtain barium strontium titanate slurry, adding 80g of barium strontium titanate flaky seed crystals into the slurry, performing ball milling for 30min to obtain barium strontium titanate slurry, placing the slurry in a conical flask, performing vacuum degassing for 30min, placing the slurry on a casting machine for casting molding, performing tape casting at a rotation number of 300r/min and a gap between a tape casting knife and a tape casting machine of 150 mu m, standing and drying at room temperature for 24h to obtain a barium strontium titanate film blank with a thickness of 0.2mm, laminating 40 layers of barium strontium titanate film blanks to 2.5mm, performing hot water pressure equalization at a laminating pressure of 8MPa to obtain a blocky barium strontium titanate ceramic blank, placing the barium strontium titanate ceramic blank in a muffle furnace to perform glue discharge at a heating rate of 1 ℃/min and a heat preservation time of 380 ℃ of 2h, placing the blank after glue discharge in a sintering furnace at a heating rate of 3 ℃/min, the temperature is kept at 1450 ℃ for 20h, and the textured barium strontium titanate ceramic is obtained by sintering; wherein the dispersant is a copolymer of isobutene and maleic acid glycoside; the plasticizer is polyethylene glycol 600.
The barium strontium titanate textured ceramic obtained in this example has a relative density of 98%, a texturing degree of 85%, a dielectric constant of 10200, a dielectric loss of 0.009, and a dielectric tunability of 57%.
In order to illustrate the performance of the barium strontium titanate textured ceramics prepared in examples 1 to 5, the specific detection results are shown in table 1.
Wherein, the ratio of the bulk density to the theoretical density of the sample is determined as the relative density by adopting an Archimedes drainage method; the ratio of the sum of diffraction peaks in a specific X-ray diffraction direction to the sum of all diffraction peaks is texture degree; the dielectric constant and the dielectric loss are measured by an impedance tester; the dielectric tunability was measured by a ferroelectric meter.
TABLE 1 relevant Properties of barium strontium titanate textured ceramics prepared in examples 1-5
| Item | Relative density | Degree of texture | Dielectric constant | Dielectric loss | Dielectric tunability |
| Example 1 | 95％ | 55％ | 8000 | 0.04 | 40％ |
| Example 2 | 98％ | 90％ | 11000 | 0.005 | 60％ |
| Example 3 | 96％ | 72％ | 9800 | 0.02 | 50％ |
| Example 4 | 95％ | 63％ | 9100 | 0.03 | 47％ |
| Example 5 | 98％ | 85％ | 10200 | 0.009 | 57％ |
As can be seen from Table 1, the relative density, texture degree, dielectric constant and dielectric tunability of the sample are all improved with the increase of the sintering temperature and the extension of the holding time, and the dielectric loss of the sample is reduced. The comprehensive performance of the ceramic can be greatly improved by increasing the sintering temperature and prolonging the heat preservation time.
To further illustrate the effects of the present invention, the crystallinity and morphology of the product prepared in example 1 were also examined, and the specific results are shown in fig. 1 and fig. 2.
As can be seen from FIG. 1, the most intense peak of the X-ray diffraction of FIG. 1a is the shift of the (100) crystal plane from the most intense diffraction peak of the standard data, indicating that the ceramic grains are growing in a particular direction.
As can be seen from FIGS. 2 to 3, the grain structure of the barium strontium titanate ceramic preferentially grows parallel to the casting direction to form a texture structure.
In conclusion, the invention provides a barium strontium titanate textured ceramic formed by water-based gel tape casting and a preparation method thereof. The barium strontium titanate flaky seed crystals are combined with the barium strontium titanate powder, and the flaky barium strontium titanate seed crystals are directionally arranged in the barium strontium titanate powder along the casting direction under the casting process, so that the orientation of the ceramic material is improved, and the purpose of improving the dielectric property of the ceramic material can be achieved.
The present invention describes preferred embodiments and effects thereof. Additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. The barium strontium titanate textured ceramic formed by water-based gel tape casting is characterized by comprising barium strontium titanate powder and barium strontium titanate flaky seed crystals, wherein the barium strontium titanate flaky seed crystals are directionally arranged in the barium strontium titanate powder along the tape casting direction under the tape casting process to form ceramic with a textured structure; the relative density is 95-98%, the texture degree is 55-90%, the dielectric constant is 8000-11000, the dielectric loss is 0.005-0.04, and the dielectric adjustability is 40-60%.
2. The preparation method of the barium strontium titanate textured ceramic formed by water-based gel casting according to claim 1, which is characterized by comprising the following steps:
s1, respectively weighing barium strontium titanate powder, deionized water, a dispersing agent and a plasticizer, mixing and ball-milling for 24-48 h, then adding barium strontium titanate flaky seed crystals, and continuing ball-milling for 0.5-1 h to obtain barium strontium titanate slurry;
wherein the mass ratio of the barium strontium titanate powder to the deionized water to the dispersant to the plasticizer is 100: 30-60: 5-15: 4-12; the adding amount of the barium strontium titanate flaky seed crystals is 20-100% of the mass of the barium strontium titanate powder;
s2, performing vacuum degassing on the barium strontium titanate slurry obtained in the S1, then performing tape casting, and drying at room temperature after molding to obtain a barium strontium titanate film blank; wherein the thickness of the prepared barium strontium titanate film blank is 0.1-0.2 mm;
s3, after laminating the barium strontium titanate film blank obtained in the S2, carrying out hot water pressure equalization to obtain a blocky barium strontium titanate ceramic blank;
and S4, carrying out binder removal and sintering on the blocky barium strontium titanate ceramic blank obtained in the S3 to obtain the textured barium strontium titanate ceramic.
3. The method for preparing barium strontium titanate textured ceramic by water-based gel tape casting according to claim 2, wherein the barium strontium titanate powder is amorphous Ba0.6Sr0.4TiO3Powder having an average particle diameter of 0.5. mu.m.
4. The method for preparing barium strontium titanate textured ceramic by water-based gel tape casting according to claim 2, wherein the barium strontium titanate flaky seed crystal is flaky Ba prepared by a molten salt method0.6Sr0.4TiO3Seed crystal having a thickness of 0.5 μm and a diameterThe longitudinal length was 10 μm.
5. The method for preparing barium strontium titanate textured ceramic by water-based gel tape casting according to claim 2, wherein the dispersant is a copolymer of isobutylene and maleic acid glycoside.
6. The method for preparing the barium strontium titanate textured ceramic by water-based gel casting according to claim 2, wherein the plasticizer is polyethylene glycol 600.
7. The preparation method of the barium strontium titanate textured ceramic by the water-based gel tape casting according to claim 2, wherein in the tape casting process, the gap between a tape casting knife and a steel tape is adjusted to be 150-300 μm, and the rotation number of the steel tape is 300-400 r/min.
8. The preparation method of the barium strontium titanate textured ceramic formed by the water-based gel tape casting according to claim 2, wherein the barium strontium titanate film blank is laminated by laminating 30-50 layers of barium strontium titanate film blanks to 2-3 mm, and the laminating pressure is 2-10 MPa.
9. The method for preparing the barium strontium titanate textured ceramic by water-based gel tape casting according to claim 2, wherein the binder removal is performed at 380 ℃ for 2 h.
10. The preparation method of the barium strontium titanate textured ceramic formed by casting the water-based gel according to claim 2, wherein the sintering is carried out at 1350-1450 ℃ for 5-20 h.
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Effective date of registration: 20211123 Address after: 401520 No. 1148, Gaoyang Road, Hechuan District, Chongqing Patentee after: Zhongke run capital (Chongqing) aerogel Technology Research Institute Co.,Ltd. Address before: 710000 No. 127 Youyi West Road, Shaanxi, Xi'an Patentee before: Northwestern Polytechnical University |