Joule heat ultrafast sintering preparation method of barium titanate ceramic with ultrahigh dielectric constant and low loss

Abstract

The invention provides a Joule heat ultrafast sintering preparation method of barium titanate ceramic with ultrahigh dielectric constant and low loss, which comprises the following steps: ball-milling and mixing barium titanate powder and copper oxide powder, drying, pressing into a cake-shaped sample, carrying out cold isostatic pressing to obtain a sample piece, and carrying out vacuum treatment on Joule heat ultrafast sintering equipment to obtain the barium titanate ceramic with ultrahigh dielectric constant and low loss. Putting the sample preparation sheet between two layers of graphite felts, and starting Joule heat ultrafast sintering equipment to enable the graphite felts to generate Joule heat, so as to realize short-time sintering of the barium titanate ceramic. According to the invention, a Joule heat ultrafast sintering technology is adopted, and Joule heat is generated by directly applying voltage and current to the graphite felt, so that the sintering time is greatly shortened, and environmental pollution is avoided; meanwhile, the dielectric constant of the barium titanate ceramic is greatly improved by adding copper oxide, and the energy consumption is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of ceramic capacitor technology, and specifically to a high-temperature ceramic material, and more particularly to a Joule thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss. Background Technology

[0002] Barium titanate is widely used in multilayer ceramic capacitors, piezoelectric ceramic devices, and dielectric energy storage materials due to its high dielectric constant, good insulation properties, and excellent thermal stability. With the rapid development of 5G communication and miniaturization of electronic devices, the market has an urgent need for ceramic capacitors with ultra-high dielectric constant, low loss, high-frequency stability, and efficient fabrication.

[0003] Currently, solid-state sintering and liquid-phase synthesis are widely used to prepare barium titanate ceramics. While solid-state sintering is simple and low-cost, it requires holding at 1200-1400℃ for 4-8 hours, leading to grain coarsening and decreased dielectric properties, and also incurs high energy consumption and low production efficiency. Liquid-phase synthesis, although achieving higher dielectric constants, is complex, costly, and generates large amounts of wastewater, causing serious environmental pollution. Summary of the Invention

[0004] The purpose of this invention is to provide a Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss, thereby improving the dielectric constant of barium titanate ceramics while reducing energy consumption.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss by Joule heating and ultrafast sintering includes the following steps:

[0007] S1. Take 97%-99.9% of barium titanate powder and 0.1%-3% of copper oxide powder by mass percentage, mix them, add ball milling beads and ball milling media, and wet ball mill to form a raw material slurry. After drying the raw material slurry, grind and sieve it to obtain mixed powder. Press the mixed powder into a cake shape to make a sample, and then perform cold isostatic pressing to obtain a sample piece.

[0008] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1200-1600℃. After holding at the temperature, the sample is taken out to obtain barium titanate ceramic.

[0009] Furthermore, the ball milling media in step S1 are anhydrous ethanol and deionized water, and the wet ball milling time is 4-8 hours.

[0010] Furthermore, the drying temperature in step S1 is 80-120℃, and the drying time is 4-8 hours.

[0011] Furthermore, the median particle size D50 of the mixed powder obtained by grinding and sieving in step S1 is 0.3-1.5 μm.

[0012] Furthermore, the pressure of the cold isostatic pressing process in step S1 is 100-700 MPa, and the time is 1-10 min.

[0013] Furthermore, the Joule heating generated by the graphite felt in step S2 can also be achieved by setting a staged heating mode in the Joule heating ultrafast sintering equipment.

[0014] Furthermore, the heat preservation time in step S2 is 30 seconds to 5 minutes.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] This invention employs Joule heating ultrafast sintering technology, directly applying voltage and current to the graphite felt to achieve a sintering temperature exceeding 1200℃ within 30 seconds, significantly shortening the sintering time and substantially reducing energy consumption. Simultaneously, the addition of copper oxide greatly improves the dielectric constant of the barium titanate ceramic. 2+ It can partially replace Ti in the BaTiO lattice 4+ CuO forms defect dipoles, enhancing local polarization response and thus increasing the overall dielectric constant of the material. Furthermore, CuO promotes liquid phase formation during sintering, which aids in grain growth and densification, reduces microscopic defects such as porosity, and lowers leakage current and interfacial polarization losses. Simultaneously, Cu… 2+ The introduction of copper oxide inhibits oxygen volatilization, increases the insulation resistance of the material, and further reduces dielectric loss. Therefore, copper oxide doping not only optimizes the microstructure of barium titanate ceramics but also synergistically enhances its dielectric properties through defect dipole polarization and lattice modulation mechanisms. Furthermore, the use of Joule heating ultrafast sintering technology can minimize environmental pollution and achieve green production. Attached Figure Description

[0017] Figure 1 This is a graph showing the relationship between the dielectric constant and temperature of the barium titanate ceramic sintered in Example 2 of the present invention.

[0018] Figure 2 This is a temperature-time comparison chart between the Joule heating ultrafast heating of this invention and conventional sintering. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0020] Example 1

[0021] A Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss is as follows:

[0022] S1. Take 99.5% barium titanate powder and 0.5% copper oxide powder by mass percentage, mix them, add ball milling beads, anhydrous ethanol and deionized water, and wet ball mill to form a raw material slurry. The ball milling time is 6 hours and the speed is 300 r / min. Dry the raw material slurry at 80℃ for 8 hours. After drying, grind and sieve to obtain a mixed powder with a median particle size D50 of 0.3 μm. Press the mixed powder into a cake shape to prepare the sample, and then use a pressure of 500 MPa to perform cold isostatic pressing for 10 minutes to finally obtain the sample piece.

[0023] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The stage heating mode is selected in the Joule heating ultrafast sintering equipment, and the required sintering temperature is set to 1500℃. The supercapacitor in the equipment discharges and transfers the Joule heat to the graphite felt. After holding at this temperature for 4 minutes, the sample is taken out to obtain barium titanate ceramic.

[0024] Example 2

[0025] A Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss is as follows:

[0026] S1. Take 99% barium titanate powder and 1% copper oxide powder by mass percentage, mix them, add ball milling beads, anhydrous ethanol and deionized water, and wet ball mill to form a raw material slurry. The ball milling time is 5 hours and the speed is 300 r / min. Dry the raw material slurry at 120℃ for 4 hours. After drying, grind and sieve to obtain a mixed powder with a median particle size D50 of 1.5 μm. Press the mixed powder into a cake shape for sample preparation, and then perform cold isostatic pressing treatment at 700 MPa for 1 minute to finally obtain the sample piece.

[0027] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1600℃. After holding at the temperature for 30s, the sample is taken out to obtain barium titanate ceramic.

[0028] Example 3

[0029] A Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss is as follows:

[0030] S1. Take 98.5% barium titanate powder and 1.5% copper oxide powder by mass percentage, mix them, add ball milling beads, anhydrous ethanol and deionized water, and wet ball mill to form a raw material slurry. The ball milling time is 8 hours and the speed is 300 r / min. Dry the raw material slurry at 100℃ for 6 hours. After drying, grind and sieve to obtain a mixed powder with a median particle size D50 of 0.6 μm. Press the mixed powder into a cake shape to prepare the sample, and then perform cold isostatic pressing at 100 MPa for 10 minutes to finally obtain the sample piece.

[0031] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1200℃. After holding at the temperature for 5 minutes, the sample is taken out to obtain barium titanate ceramic.

[0032] Example 4

[0033] A Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss is as follows:

[0034] S1. Take 99.9% barium titanate powder and 0.1% copper oxide powder by mass percentage, mix them, add ball milling beads, anhydrous ethanol and deionized water, and wet ball mill to form a raw material slurry. The ball milling time is 5 hours and the speed is 300 r / min. Dry the raw material slurry at 90℃ for 5 hours. After drying, grind and sieve to obtain a mixed powder with a median particle size D50 of 1 μm. Press the mixed powder into a cake shape for sample preparation, and then perform cold isostatic pressing treatment at 400 MPa for 5 minutes to finally obtain the sample piece.

[0035] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1400℃. After holding at the temperature for 2 minutes, the sample is taken out to obtain barium titanate ceramic.

[0036] Example 5

[0037] A Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss is as follows:

[0038] S1. Take 97% barium titanate powder and 3% copper oxide powder by mass percentage, mix them, add ball milling beads, anhydrous ethanol and deionized water, and wet ball mill to form a raw material slurry. The ball milling time is 6 hours and the speed is 300 r / min. Dry the raw material slurry at 80℃ for 8 hours. After drying, grind and sieve to obtain a mixed powder with a median particle size D50 of 1.5 μm. Press the mixed powder into a cake shape for sample preparation, and then perform cold isostatic pressing treatment at 500 MPa for 2 minutes to finally obtain the sample piece.

[0039] S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1600℃. After holding at this temperature for 30smin, the sample is taken out to obtain barium titanate ceramic.

[0040] The dielectric properties of the barium titanate ceramic prepared in Example 2 were tested at a frequency of 1 kHz. Figure 1 As shown, the dielectric constant of the prepared barium titanate ceramic exhibits a significant peak at the Curie temperature of 126.9 °C, reaching a maximum value of 41,417; the corresponding dielectric loss is 0.03, which is at a relatively low level. These results demonstrate that the prepared barium titanate ceramic possesses high dielectric response and low energy loss, exhibiting excellent dielectric properties.

[0041] To further illustrate the preparation method of this invention, the temperature-time curves of the Joule heating ultrafast sintering process used in this invention were compared with those of the traditional heating sintering process, as follows: Figure 2 As shown in the figure, it can be clearly observed that the temperature rises gradually under traditional heating methods, requiring a long time to reach the target temperature; while the Joule heating ultrafast heating method can rapidly raise the temperature and reach a stable state in a very short time. This comparison intuitively demonstrates the significant advantage of the ultrafast heating method used in this invention in terms of sintering efficiency compared to traditional heating methods. By utilizing the Joule heat generated by electric current in the graphite felt to achieve localized instantaneous high-temperature sintering of the sample, only about 5 minutes are needed from sample placement to finished product. The sample can be removed immediately after sintering without the need for prolonged heating and cooling, greatly shortening the cycle and increasing throughput.

Claims

1. A method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss by Joule heating and ultrafast sintering, characterized in that, Includes the following steps: S1. Take 97%-99.9% of barium titanate powder and 0.1%-3% of copper oxide powder by mass percentage, mix them, add ball milling beads and ball milling media, and wet ball mill to form a raw material slurry. After drying the raw material slurry, grind and sieve it to obtain mixed powder. Press the mixed powder into a cake shape to make a sample, and then perform cold isostatic pressing to obtain a sample piece. S2. Vacuum treatment is performed on the Joule heating ultrafast sintering equipment. The sample is placed between two layers of graphite felt. The Joule heating ultrafast sintering equipment is started to apply voltage and current to the graphite felt to generate Joule heat, so that the firing temperature reaches 1200-1600℃. After holding at the temperature, the sample is taken out to obtain barium titanate ceramic.

2. The method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss by Joule heating and ultrafast sintering according to claim 1, characterized in that, The ball milling media in step S1 are anhydrous ethanol and deionized water, and the wet ball milling time is 4-8 hours.

3. The method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss by Joule heating and ultrafast sintering according to claim 1, characterized in that, The drying temperature in step S1 is 80-120℃, and the drying time is 4-8 hours.

4. The Joule-thermal ultrafast sintering preparation method for barium titanate ceramics with ultra-high dielectric constant and low loss according to claim 1, characterized in that, The median particle size D50 of the mixed powder obtained by grinding and sieving in step S1 is 0.3-1.5 μm.

5. The Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss according to claim 1, characterized in that, The pressure of the cold isostatic pressing process in step S1 is 100-700 MPa, and the time is 1-10 min.

6. The Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss according to claim 1, characterized in that, The Joule heating of the graphite felt described in step S2 can also be achieved by setting a staged temperature rise mode in the Joule heating ultrafast sintering equipment.

7. The Joule-thermal ultrafast sintering method for preparing barium titanate ceramics with ultra-high dielectric constant and low loss according to claim 1, characterized in that, The heat preservation time in step S2 is 30 seconds to 5 minutes.

Images