CN112919902A - Preparation method of electric field assisted low-temperature rapid sintering fine-grain barium titanate capacitor ceramic - Google Patents
Preparation method of electric field assisted low-temperature rapid sintering fine-grain barium titanate capacitor ceramic Download PDFInfo
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- 229910002113 barium titanate Inorganic materials 0.000 title claims abstract description 76
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 title claims abstract description 74
- 238000005245 sintering Methods 0.000 title claims abstract description 61
- 239000000919 ceramic Substances 0.000 title claims abstract description 53
- 230000005684 electric field Effects 0.000 title claims abstract description 49
- 239000003990 capacitor Substances 0.000 title claims abstract description 45
- 238000002360 preparation method Methods 0.000 title description 6
- 238000000034 method Methods 0.000 claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims description 18
- 239000002994 raw material Substances 0.000 claims description 7
- AOWKSNWVBZGMTJ-UHFFFAOYSA-N calcium titanate Chemical compound [Ca+2].[O-][Ti]([O-])=O AOWKSNWVBZGMTJ-UHFFFAOYSA-N 0.000 claims description 5
- 238000005553 drilling Methods 0.000 claims description 5
- 229910003440 dysprosium oxide Inorganic materials 0.000 claims description 5
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(iii) oxide Chemical compound O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 claims description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 5
- 239000000395 magnesium oxide Substances 0.000 claims description 5
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 5
- 238000000465 moulding Methods 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- 238000011068 loading method Methods 0.000 claims description 4
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- 230000006698 induction Effects 0.000 abstract description 6
- 238000005265 energy consumption Methods 0.000 abstract description 5
- 239000002245 particle Substances 0.000 abstract description 4
- 238000001272 pressureless sintering Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 10
- 229910052697 platinum Inorganic materials 0.000 description 5
- 239000003985 ceramic capacitor Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 230000003679 aging effect Effects 0.000 description 1
- -1 barium titanate compound Chemical class 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000000748 compression moulding Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000009766 low-temperature sintering Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000002490 spark plasma sintering Methods 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
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- C04B35/468—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
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Abstract
The invention discloses a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature under the assistance of an electric field, which rapidly sinters fine-grained barium titanate at a lower temperature. The invention is pressed and formed after the materials are mixed according to the proportion; putting the blank into a device, increasing the temperature at a constant temperature-rise rate, applying an auxiliary electric field, and setting a critical value for the current; when the temperature reaches 900-950 ℃, entering a stable stage, and keeping the current at a critical value for a period of time. The apparatus for applying the electric field is then switched off and the furnace begins to cool rapidly to room temperature. Under the induction of an electric field, the mass transfer speed of particles in a sample is accelerated, and at the moment, the sample can be quickly contracted and densified; meanwhile, because a large amount of heat can be generated in a short time, the sintering temperature is low and is far lower than the temperature of pressureless sintering. The method can greatly reduce the furnace temperature and cost required during sintering, accelerate the sintering speed and reduce the energy consumption. It provides a novel process method for producing capacitor ceramics with excellent dielectric property.
Description
Technical Field
The invention belongs to the field of preparing barium titanate ceramic capacitors, and particularly relates to a method for preparing fine-grain barium titanate capacitor ceramic through rapid low-temperature sintering.
Background
Barium titanate, BaTiO3Has good physicochemical properties, such as: the performance of catalysis, gas sensing, ferroelectric, thermoelectric, piezoelectric, electro-optic conversion and the like is widely applied to many fields. Among them, barium titanate as a ceramic dielectric plays an important role in a multilayer ceramic capacitor (MLCC). With the development of miniaturization and integration of capacitors, new requirements are made on dielectric materials: large dielectric constant and small crystal grain size. In order to improve the performance of the capacitor, the requirements can be met by means of doping modification, different preparation processes and the like, such as different sintering methods and the like.
At present, people mainly perform pressureless sintering, namely, barium titanate powder is pressed and formed in a muffle furnace, the temperature is raised to about 1300 ℃ for solid phase sintering, the time of the whole process is longer, and the energy consumption is higher. The sample is sintered without pressure, the grain size is about 10 mu m, the grain size is too large, and the puncture resistance and the aging resistance are poor. Therefore, it is necessary to lower the sintering temperature and refine the grain size. The Spark Plasma Sintering (SPS) has not only the plastic deformation caused by joule heat and pressurization of hot-pressing sintering, but also the direct-current pulse voltage generated between powder particles, and effectively utilizes the spontaneous heating effect generated by the discharge between powder particles, and is characterized by fast temperature rise and fast preparation of a sample with good compactness and small crystal grains. The pressureless sintering time adopted by the prior art is overlong, the temperature is higher, and the grain size is larger. In view of this, it is necessary to provide a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature with the assistance of an electric field, so as to reduce the temperature, improve the degree of grain refinement, improve the preparation efficiency and improve the quality, which is a technical problem to be solved urgently.
Disclosure of Invention
In order to solve the problems of the prior art, the invention aims to overcome the defects in the prior art, and provides a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature under the assistance of an electric field, so that the sintering temperature is reduced, an external field optimized sintering process is introduced, the grain refinement degree of the prepared barium titanate capacitor ceramic is improved, the preparation efficiency is improved, the quality of the ceramic product is obviously improved, the energy consumption is reduced, and the cost is obviously reduced.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature under the assistance of an electric field comprises the following steps:
(1) preparing materials according to the raw material composition of the barium titanate capacitor ceramic prepared by the target, pressing and molding the mixed raw materials into a blank, and drilling holes at two ends of the blank;
(2) putting the green body into an electric field auxiliary heating device, and respectively enabling the positive electrode and the negative electrode of the heating device to penetrate through the holes at the two ends of the green body so as to enable the two ends of the green body to be connected with the positive electrode and the negative electrode of the electric field auxiliary heating device;
(3) heating at a speed of not less than 10 ℃/min to raise the temperature to the sintering temperature range of barium titanate, applying an auxiliary electric field to the green body when the sintering temperature of barium titanate is reached, setting the current to be a critical value, controlling the electric field loading to maintain for a certain time to ensure the stability of the current in the sintering process of the green body, melting and sintering the green body, then cooling at a speed of not less than 3 ℃/min until the temperature is reduced to the room temperature, and preparing the fine-grain barium titanate capacitor ceramic by a low-temperature rapid sintering method. The method of the invention obtains the fine-grained barium titanate capacitor ceramic product with excellent compactness and dielectric property by low-temperature rapid sintering and molding under the induction of an electric field.
Preferably, in the step (3), the electric field loading time is controlled for at least 240 s; and controlling the heat preservation time to be at least 10 minutes during heat preservation.
Preferably, in the step (3), the current density is controlled within the range of 35 to 45mA/mm2. Further preferably, the current density is controlled within the range of 37-44 mA/mm2。
Preferably, in the step (3), the electric field strength is controlled to be not less than 150V/cm. Further preferably, the electric field intensity is controlled to be not less than 150-155V/cm.
Preferably, in the step (3), the sintering temperature is controlled to be 900-950 ℃. Further preferably, the sintering temperature is controlled within 900-935 ℃.
Preferably, in the step (3), the grain size of the prepared fine-grained barium titanate capacitor ceramic is not more than 400nm, and the compactness of the ceramic is not less than 88.6%. It is further preferred that the grain size of the prepared fine-grained barium titanate capacitor ceramic is not more than 350 nm. It is still further preferred that the fine-grained barium titanate capacitor ceramic has a grain size of no greater than 300 nm. Further preferably, the density of the ceramic is not less than 90%.
Preferably, in the step (1), the barium titanate compound formula is: magnesium oxide, dysprosium oxide and calcium titanate are added into barium titanate powder.
Preferably, in the step (1), the mixed raw materials are poured into a mould and are pre-pressed for forming; then, obtaining a blank body through hydraulic pressure; drilling holes at two ends of the blank body, and coating platinum slurry.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the barium titanate ceramic capacitor material is quickly sintered at a lower temperature, a blank formed by pressing is placed into a device, then an electric field is applied, and the heating rate is constant; under the induction of an electric field, the mass transfer speed in the sample is accelerated, and at the moment, the sample can be rapidly contracted and densified;
2. the method can generate a large amount of heat within a short time, so that the required sintering temperature is far lower than that of pressureless sintering, and finally, a sample with the grain size of about 300nm is obtained, and the anti-breakdown and aging properties of the sample are improved;
3. the method of the invention has the advantages of low sintering temperature, short sintering time, reduced energy consumption and reduced sintering cost.
Drawings
FIG. 1 is a graph showing the grain size distribution of a ceramic prepared according to a preferred embodiment of the present invention.
FIG. 2 is a graph showing the power versus temperature curves at different sintering temperatures and different current densities for the first and second embodiments of the present invention.
FIG. 3 is a scanning electron microscope image of barium titanate capacitor ceramic under different current densities in the first and second embodiments of the present invention.
FIG. 4 shows an embodiment of the present invention with a second power of 44mA/mm2The dielectric constant of the lower sintered sample was plotted against temperature.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
the first embodiment is as follows:
in this embodiment, a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature with the assistance of an electric field includes the following steps:
(1) adding magnesium oxide, dysprosium oxide and calcium titanate into barium titanate, mixing the materials according to a proper proportion, pressing and molding the mixed raw materials into a barium titanate blank, and drilling holes at two ends of the barium titanate blank;
(2) putting the barium titanate blank into an electric field auxiliary heating device, respectively enabling positive and negative platinum wires of the heating device to penetrate through holes at two ends of the barium titanate blank, and suspending the barium titanate blank between the positive and negative platinum wires to enable two ends of the barium titanate blank to be connected with positive and negative electrodes of the electric field auxiliary heating device;
(3) heating at a speed of 10 ℃/min, applying an electric field of no more than 155V/cm to the barium titanate blank, controlling the temperature to reach 935 ℃, rapidly reducing the voltage to generate current, and controlling the current density to be 37mA/mm2Keeping the current unchanged for 240s to ensure the stability of the current in the sintering process of the ceramic body, melting and sintering the barium titanate body, then cooling at the speed of 3 ℃/min until the temperature is reduced to the room temperature, and preparing the fine-grained barium titanate capacitor by a low-temperature rapid sintering methodAnd (3) ceramic.
The grain size of the fine-grain barium titanate capacitor ceramic prepared by the embodiment is 300 +/-10 nm, and the compactness of the ceramic reaches 88.6%. The method of the embodiment obtains the fine-grained barium titanate capacitor ceramic product with excellent compactness and dielectric property by low-temperature rapid sintering and forming under the induction of an electric field.
Example two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in this embodiment, a method for rapidly sintering fine-grained barium titanate capacitor ceramic at low temperature with the assistance of an electric field includes the following steps:
(1) adding magnesium oxide, dysprosium oxide and calcium titanate into barium titanate, mixing the materials according to a proper proportion, pressing and molding the mixed raw materials into a barium titanate blank, and drilling holes at two ends of the barium titanate blank;
(2) putting the barium titanate blank into an electric field auxiliary heating device, respectively enabling positive and negative platinum wires of the heating device to penetrate through holes at two ends of the barium titanate blank, and suspending the barium titanate blank between the positive and negative platinum wires to enable two ends of the barium titanate blank to be connected with positive and negative electrodes of the electric field auxiliary heating device;
(3) heating at a speed of 10 ℃/min, applying an electric field of no more than 155V/cm to the barium titanate blank, controlling the temperature to reach 900 ℃, rapidly reducing the voltage to generate current, and controlling the current density to be 44mA/mm2Keeping the current unchanged for 240s to ensure the stability of the current in the sintering process of the ceramic body, melting and sintering the barium titanate body, and then cooling at the speed of 3 ℃/min until the temperature is reduced to the room temperature, thereby preparing the fine-grain barium titanate capacitor ceramic by a low-temperature rapid sintering method.
The grain size of the fine-grain barium titanate capacitor ceramic prepared by the embodiment is 300 +/-10 nm, and the compactness of the ceramic reaches 90%. The method of the embodiment obtains the fine-grained barium titanate capacitor ceramic product with excellent compactness and dielectric property by low-temperature rapid sintering and forming under the induction of an electric field. The dielectric constant of the fine-grained barium titanate capacitor ceramic prepared in the embodiment is measured, and the dielectric property is good as shown in FIG. 4.
According to the invention, the fine-grain barium titanate capacitor ceramic is prepared by other embodiments, and the fine-grain barium titanate is rapidly sintered at a lower temperature of 900-950 ℃. Adding magnesium oxide, dysprosium oxide and calcium titanate into barium titanate, mixing the materials according to a proper proportion, and performing compression molding; putting the blank into a designed device, increasing the temperature at a constant temperature-rising rate, applying an auxiliary electric field, keeping the voltage constant, and setting a critical value for the current; and when the temperature reaches 900-950 ℃, entering a stable stage, and keeping the current at a critical value for a period of time. The apparatus for applying the electric field is then switched off and the furnace begins to cool rapidly to room temperature. The grain size of the prepared fine-grained barium titanate capacitor ceramic is not more than 400nm, see figure 1. Fig. 2 is a graph showing the power variation with temperature at different sintering temperatures and different current densities according to the first and second embodiments of the present invention, and it can be seen from fig. 2 that the power can be kept stable when the temperature is controlled to 930-950 ℃. In the first embodiment, the power can be kept stable when the temperature is controlled to reach 900-950 ℃. It can be seen that the method of the embodiment is easier to maintain the stability of the sintering process. FIG. 3 is a scanning electron microscope image of barium titanate capacitor ceramic under different current densities in the first and second embodiments of the present invention. It is understood that the barium titanate capacitor ceramic prepared in the above examples has uniformly refined crystal grains. Under the induction of an electric field, the mass transfer speed of particles in a sample is accelerated, and at the moment, the sample can be quickly contracted and densified; meanwhile, a large amount of heat can be generated within a short time, so that the sintering temperature is reduced to 900-950 ℃, and is far lower than the non-pressure sintering temperature. The method can greatly reduce the furnace temperature and cost required during sintering, accelerate the sintering speed and reduce the energy consumption. It provides a novel process method for producing capacitor ceramics with excellent dielectric property.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be replaced with equivalents as long as the object of the present invention is met, and the technical principle and the inventive concept of the present invention are not departed from the scope of the present invention.
Claims (10)
1. A method for rapidly sintering fine-grained barium titanate capacitor ceramics under low temperature assisted by an electric field is characterized by comprising the following steps:
(1) preparing materials according to the raw material composition of the barium titanate capacitor ceramic prepared by the target, pressing and molding the mixed raw materials into a blank, and drilling holes at two ends of the blank;
(2) putting the green body into an electric field auxiliary heating device, and respectively enabling the positive electrode and the negative electrode of the heating device to penetrate through the holes at the two ends of the green body so as to enable the two ends of the green body to be connected with the positive electrode and the negative electrode of the electric field auxiliary heating device;
(3) heating at a speed of not less than 10 ℃/min to raise the temperature to the sintering temperature range of barium titanate, applying an auxiliary electric field to the green body when the sintering temperature of barium titanate is reached, setting the current to be a critical value, controlling the electric field loading to maintain for a certain time to ensure the stability of the current in the sintering process of the green body, melting and sintering the green body, then cooling at a speed of not less than 3 ℃/min until the temperature is reduced to the room temperature, and preparing the fine-grain barium titanate capacitor ceramic by a low-temperature rapid sintering method.
2. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (3), controlling the electric field loading time to be at least 240 s; and controlling the heat preservation time to be at least 10 minutes during heat preservation.
3. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (3), the current density is controlled within the range of 35-45 mA/mm2。
4. The method of electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 3 wherein: in the step (3), the current density is controlled within the range of 37-44 mA/mm2。
5. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (3), the electric field intensity is controlled to be not less than 150V/cm.
6. The method of electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 5 wherein: in the step (3), the electric field intensity is controlled to be not less than 150-155V/cm.
7. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (3), the sintering temperature is controlled to be 900-950 ℃.
8. The method of electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 7 wherein: in the step (3), the sintering temperature is controlled to be 900-935 ℃.
9. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (3), the grain size of the prepared fine-grain barium titanate capacitor ceramic is not more than 400nm, and the compactness of the ceramic is not less than 88.6%.
10. The method for electric field assisted low temperature rapid sintering of fine crystalline barium titanate capacitor ceramics according to claim 1 wherein: in the step (1), the formula of the barium titanate mixture is as follows: magnesium oxide, dysprosium oxide and calcium titanate are added into barium titanate powder.
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