SrTiO3-based giant dielectric ceramic material sintered under assistance of electric field and preparation method of SrTiO3-based giant dielectric ceramic material

Abstract

The invention relates to an electric field-assisted sintered SrTiO3 (ST)-based giant dielectric ceramic material and a preparation method thereof, a rare earth element Y is doped into ST ceramic, and a Sr1-1.5 xYxTiO3 ceramic sample is obtained through primary ball milling, drying, briquetting, pre-sintering, crushing, secondary ball milling, sieving, isostatic cool pressing and electric field-assisted sintering. The Sr1-1.5 xYxTiO3 ceramic provided by the invention obtains the giant dielectric constant and low dielectric loss performance under the condition that the sintering time and the sintering temperature are far lower than those of a traditional solid phase method, the energy consumption for producing the giant dielectric ceramic is greatly reduced, and a reference method is provided for industrial production of the ceramic.

Description

Technical Field

[0001] This invention relates to the field of high-energy-storage dielectric ceramic capacitors, and more specifically to a method for preparing ST-based giant dielectric ceramic materials by electric field-assisted sintering. Background Technology

[0002] Giant dielectric constant ceramics ( Ɛ r >10 4 ST-based ceramics have wide applications in emerging industrial fields such as autonomous driving, immersive virtual reality, future factories, and smart healthcare in the 6G era, and are of great significance in adapting to the development trend of electronic devices towards higher frequencies, higher voltages, and miniaturization. However, traditional sintering methods for preparing ST-based ceramics require long-term high-temperature treatment in a reducing atmosphere to obtain giant dielectric properties, which not only consumes a lot of energy but also poses a challenge to industrial production.

[0003] Electric field assisted sintering technology, commonly known as "flash sintering", has attracted widespread attention since its first report due to its advantages of low sintering temperature, short holding time and fast densification rate. It is a green and environmentally friendly industrial production technology with great potential.

[0004] ST has a high dielectric constant at room temperature ( Ɛ r It exhibits a band gap of 3.2 eV and approximately 300 kV, while also displaying excellent intrinsic characteristics such as high breakdown field strength (>200 kV / cm), excellent insulation resistance, and low dielectric loss (tan ≈300 kV / cm). δ <0.01), is a matrix material very suitable for preparing giant dielectric ceramics, and it is also sensitive to the applied electric field, making it suitable for flash sintering. This invention prepares a giant dielectric ceramic by doping ST with rare earth oxide Y2O3 and using electric field-assisted sintering technology. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing ST-based giant dielectric ceramic materials by electric field-assisted sintering, overcoming the drawbacks of traditional solid-state sintering methods, such as high energy consumption and the need for reducing atmosphere treatment. The ceramics obtained using this method exhibit giant dielectric constants and low dielectric loss, and the process is environmentally friendly.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An ST-based giant dielectric ceramic material sintered under electric field assistance, with the stoichiometric formula: Sr 1-1.5x Y x TiO3, x =0~0.018.

[0007] Furthermore, the preparation method of the aforementioned ST-based giant dielectric ceramic material includes the following steps: (1) SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder are mixed according to the stoichiometric formula Sr 1-1.5x Y x TiO3, x Weigh out 0~0.018g and mix thoroughly to form a mixed ingredient; (2) The main crystalline phase powder is obtained by ball milling, drying, pressing and pre-firing the mixed ingredients in step (1); (3) After the pre-fired powder in step (2) is crushed, ball-milled twice, sieved and pressed into a green body, and the green body is sintered with electric field to obtain ST-based giant dielectric ceramic.

[0008] Furthermore, in step (1), Sr 1-1.5x Y x TiO3, x =0~0.018 powder is prepared according to the following steps: the synthesized SrCO3, TiO2 and Y2O3 powders are weighed and mixed in a molar ratio of 1:1:0~0.018. The mixed powder, zirconia spheres and deionized water are ball-milled in a mass ratio of 1:1.5~5:1~1.5. The ball milling speed is 300~500 rpm and the time is 8~12h. The ball-milled slurry is dried, pressed into blocks, pre-calcined in air and nitrogen at 1100~1200℃ for 2~4h, and then pulverized to obtain the main crystalline phase powder.

[0009] Furthermore, the main crystalline phase powder synthesized in step (2) is ball-milled a second time with zirconia spheres and deionized water at a mass ratio of 1:1.5~5:1~1.5, and the ball milling speed is 300~500 rpm.

[0010] Therefore, the ball milling time in step two is 8~24 hours.

[0011] Therefore, in step two, the sieve mesh size is 120 mesh.

[0012] Furthermore, in step three, the pressing process involves first holding the pressure at 200MPa for 4 minutes, then holding it at 190MPa for 4 minutes, and finally releasing the pressure at 40MPa / min.

[0013] Furthermore, the specific steps of electric field-assisted sintering in step (3) are as follows: Holes are drilled at both ends of the isostatically pressed, dense dog-bone-shaped sample, and two platinum wires are passed through the holes and suspended inside a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm.2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0014] Furthermore, a method for preparing ST-based giant dielectric ceramic materials by electric field-assisted sintering includes the following steps: a sintered dog-bone-shaped sample is cut into small pieces, then polished and cleaned; silver paste is coated onto the surface of the cut sample; and the ceramic material coated with silver electrodes is heat-treated to obtain Sr... 1-1.5x Y x TiO3, x =0~0.018 giant dielectric ceramic material.

[0015] Furthermore, the aforementioned Sr 1-1.5x Y x TiO3, x The heat treatment conditions for the ceramic material coated with silver electrodes using 0~0.018 giant dielectric ceramic material are: heat treatment at 650~750℃ for 10~20min.

[0016] And, Sr prepared by the above method 1-1.5x Y x TiO3, x =0~0.018 giant dielectric ceramic material.

[0017] The present invention has the following beneficial technical effects: The material prepared by the method of this invention possesses a large dielectric constant and low dielectric loss, making it a candidate material for preparing high-energy-storage dielectric ceramic capacitors for industrial applications. The sintering temperature is reduced by 500-600℃, the sintering holding time is reduced by orders of magnitude, and energy consumption is low, making it a potentially green and environmentally friendly industrial production technology. Attached Figure Description

[0018] Figure 1 Sr prepared by conventional solid-state sintering (CS) and flash sintering (FS) in Example 4(a) 0.979 Y 0.014 (a) Sintering curve of TiO3(SYT14) ceramic, (b) Dielectric constant of the giant dielectric constant ceramic prepared by flash sintering under 1V / 1kHz test conditions. Ɛ r ) and loss tangent (tan δ ); Figure 2 The XRD patterns of ST and SYT14 powders pre-calcined and sintered under different atmospheres in Examples 1 and 4 (a, c) and the Raman spectra of ST and SYT14 powders pre-calcined and sintered under different atmospheres (b, d) are shown. Figure 3SEM images of ST and SYT14 ceramics pre-fired and sintered under different atmospheres in Examples 1 and 4; Figure 4 The dielectric spectra of ST and SYT14 ceramics pre-fired and sintered under different atmospheres in Examples 1 and 4 are shown. Detailed Implementation

[0019] The embodiments of the present invention will be described in further detail below: An ST-based giant dielectric ceramic material sintered under electric field assistance, with the stoichiometric formula Sr 1-1.5x Y x TiO3, x =0~0.018.

[0020] A field-assisted sintering of Sr 1-1.5x Y x The preparation method of TiO3 giant dielectric ceramic material includes the following steps: (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0~0.018. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0021] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0022] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0023] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials.

[0024] The present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following specific embodiments are merely further elaborations on the present invention and not further limitations thereof: Note: Sr1-1.5xYxTiO3 (x=0.014) is abbreviated as SYT14; ST ceramics that are pre-fired in air and sintered in air with an electric field are abbreviated as Air-cal-FS-ST; SYT14 ceramics pre-fired in air and sintered in air with electric field assistance are abbreviated as Air-cal-FS-ST; SYT14 ceramics pre-fired in nitrogen and sintered in air with electric field assistance are abbreviated as N2-cal-FS-ST. Example 1

[0025] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr 1-1.5x Y x TiO3, in which x =0.

[0026] Step (1) Weigh and mix SrCO3 and TiO2 powders in a molar ratio of 1:1. The purity of SrCO3 and TiO2 powders is >99.0%.

[0027] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0028] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0029] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 2

[0030] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr1-1.5x Y x TiO3, in which x =0.002.

[0031] Step (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0.002. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0032] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0033] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0034] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 3

[0035] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr 1-1.5x Y x TiO3, in which x =0.006.

[0036] (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0.006. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0037] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0038] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0039] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 4

[0040] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr 1-1.5x Y x TiO3, in which x =0.010.

[0041] (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0.010. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0042] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0043] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0044] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 5

[0045] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr 1-1.5x Y x TiO3, in which x =0.014.

[0046] (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0.014. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0047] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0048] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0049] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 6

[0050] The present invention provides a method for preparing ST-based giant dielectric ceramic materials, the formulation of which is Sr 1-1.5x Y x TiO3, in which x =0.018.

[0051] (1) Weigh and mix SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder in a molar ratio of 1:1:0.018. The purity of SrCO3 and TiO2 powders is >99.0%, and the purity of Y2O3 powder is >99.9%.

[0052] (2) Weigh the mixed powder, zircon, and deionized water, and mix them in mass ratios of 1:5:(1~1.2) and 1:5:(1.2~1.5), respectively. Then, ball mill the mixture for 8~12 hours using a planetary ball mill, and dry it at 60~100℃ for 18~20 hours. Press the dried powder into briquettes. Place the briquettes in a box furnace and pre-fire them in air at 1100~1200℃ for 2~4 hours. Alternatively, place the briquettes in a tube furnace and pre-fire them at 1100~1200℃ for 2~4 hours under nitrogen to obtain the main crystalline phase powder for later use.

[0053] (3) The main crystalline phase powder obtained by pre-firing in nitrogen and air in step 2 is mixed with zirconium spheres and deionized water at a mass ratio of 1:3~5:1~1.2 and then ball-milled for 18~24h, and then dried at 80~100℃ for 16~18h. (4) Grind the dried material from step (3) through a 120-mesh sieve to form sieved material; (5) The sieved material obtained in step (4) is pressed into a 20mm×3.1mm×1.4mm dog-bone sample using a dog-bone mold, and then pressed into shape by isostatic pressing, with the pressure controlled at 190~200MPa. Holes are punched at both ends of the isostatically pressed dense dog-bone sample, and two platinum wires are passed through the holes and suspended in a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

[0054] (6) The dog-bone-shaped sample sintered in step (5) is cut to obtain several small samples. These samples are then polished and cleaned, and silver paste is applied to their surfaces as electrodes. Subsequently, the samples coated with silver electrodes are placed in an alumina crucible lined with zirconium oxide pads, and the entire apparatus is transferred into a box furnace. Heat treatment is performed at 650~750℃ for 10~20 minutes to finally obtain Sr. 1-1.5x Y x TiO3 ceramic materials. Example 7

[0055] A comparative analysis was conducted on the electric field-assisted sintering regime of sample SYT14 in Example 4 and the traditional solid-state sintering regime, and the results were obtained. Figure 1 (a) Sintering curves of SYT14 ceramics prepared by conventional solid-state sintering (CS) and flash sintering (FS), from... Figure 1 (a) It can be seen that the FS sintering temperature is 940℃ and the duration is 480s. The energy consumption of this sintering process is much lower than that required by the CS sintering process. A comparative analysis of the performance of sample SYT14 from Example 4 with other matrix ceramic nodes yielded... Figure 1 (b) Dielectric constant of the giant dielectric constant ceramic prepared by flash calcination under test conditions of 1V / 1kHz. Ɛ r ) and loss tangent (tan δ ),from Figure 1 (b) It can be seen that the sample of Example 4 obtained a giant dielectric constant and the lowest dielectric loss.

[0056] XRD tests were performed on the samples prepared in Examples 1 and 4 to obtain... Figure 2 The result is (a,c). Figure 2 (a, c) are the XRD patterns of ST and SYT14 powders pre-fired and sintered under different atmospheres. Figure 2 (a,c) It can be seen that all ST and SYT14 powders obtained by pre-firing and sintering in nitrogen and air exhibit a cubic perovskite crystal structure. Furthermore, the (110) diffraction peaks of the SYT14 powder pre-firing in nitrogen and the ST and SYT14 ceramic powders after FS sintering show a higher angle, indicating the introduction of more oxygen vacancies. Raman spectroscopy was performed on the samples prepared in Examples 1 and 4, yielding... Figure 2 (b,d) results Figure 2 (b, d) are the Raman spectra of ST and SYT14 powders pre-fired and sintered under different atmospheres. Figure 2 (b,d) It can be seen that after the ST and SYT14 powders were pre-calcined in nitrogen and then sintered in FS, the vibration modes of TO4 and LO4 in the ST and SYT14 ceramic powder spectra showed an increase in intensity and a broadening, which proves that more oxygen vacancies were introduced.

[0057] SEM images of the ceramic samples from Examples 1 and 4 were taken, and the following results were obtained. Figure 3 result. Figure 3 SEM images of ST and SYT14 ceramics pre-fired and sintered under different atmospheres. From... Figure 3 As can be seen, all ceramics achieved a dense microstructure, and the doping with Y₂O₃ led to a reduction in grain size. The ceramic samples prepared as powders by nitrogen pre-calcination showed an increase in grain size.

[0058] The dielectric properties of samples 1 and 4 were tested, and the results were obtained. Figure 4 result. Figure 4 The dielectric spectra of ST and SYT14 ceramics pre-fired and sintered under different atmospheres are shown. Figure 4 As can be seen, by doping with Y2O3, pre-calcining the powder with nitrogen, and applying an electric field-assisted sintering method, ST-based ceramic materials with good frequency stability, large dielectric constant, and low dielectric loss were obtained. Furthermore, a low-energy-consumption and environmentally friendly process for preparing ST-based giant dielectric materials was obtained.

Claims

1. A field-assisted sintering SrTiO3-based giant dielectric ceramic material, characterized in that, The stoichiometric formula is: Sr 1- 1.5x Y x TiO3, x =0~0.

018.

2. A method for preparing SrTiO3 giant dielectric ceramics by electric field-assisted sintering, characterized in that, Includes the following steps: (1) SrCO3 and TiO2 powders and rare earth oxide Y2O3 powder are mixed according to the stoichiometric formula Sr 1-1.5x Y x TiO3, x Weigh out 0~0.018g and mix thoroughly to form a mixed ingredient; (2) The main crystalline phase powder is obtained by ball milling, drying, pressing and pre-firing the mixed ingredients in step (1); (3) After the pre-fired powder in step (2) is crushed, ball-milled twice, sieved and pressed into a green body, and the green body is sintered with electric field to obtain ST-based giant dielectric ceramic.

3. The method for preparing SrTiO3-based giant dielectric ceramic material by electric field-assisted sintering according to claim 2, characterized in that, In step (1), Sr 1-1.5x Y x TiO3, x =0~0.018 powder is prepared according to the following steps: the synthesized SrCO3, TiO2 and Y2O3 powders are weighed and mixed in a molar ratio of 1:1:0~0.

018. The mixed powder, zirconia spheres and deionized water are ball-milled in a mass ratio of 1:1.5~5:1~1.

5. The ball milling speed is 300~500 rpm and the time is 8~12h. The ball-milled slurry is dried, pressed into blocks, pre-calcined in air and nitrogen at 1100~1200℃ for 2~4h, and then pulverized to obtain the main crystalline phase powder.

4. The method for preparing an electric field-assisted sintering SrTiO3-based giant dielectric ceramic material according to claim 2, characterized in that, In step (2), the synthesized main crystalline phase powder is ball-milled with zirconia spheres and deionized water at a mass ratio of 1:1.5~5:1~1.

5. The ball milling speed is 300~500 rpm and the time is 8~24h.

5. The method for preparing an electric field-assisted sintering SrTiO3-based giant dielectric ceramic material according to claim 2, characterized in that, In step three, the sample is pressed into a dog bone shape and then pressed into a dense blank by cold isostatic pressing under a pressure of 200~250MPa.

6. The method for preparing ST-based giant dielectric ceramic material by electric field-assisted sintering according to claim 2, characterized in that, The specific steps of electric field-assisted sintering in step (3) are as follows: Holes are drilled at both ends of the isostatically pressed, dense dog-bone-shaped sample. Two platinum wires are passed through the holes and suspended inside a tube furnace. The two platinum wires are connected to the positive and negative terminals of a high-voltage DC power supply. The tube furnace is heated to 400℃. Subsequently, under the action of an electric field of 75~200V / cm, the furnace temperature is further increased, maintaining the initial temperature in the range of 850~1000℃. After flash burning occurs, it lasts for 30~500 seconds, and the current density passing through the sample is controlled at 20~80mA / mm. 2 Then the DC power supply is cut off, and the temperature is reduced to 500°C in 80-100 minutes. Finally, the furnace is cooled to room temperature. The electric field-assisted sintering process is carried out in air.

7. A method for preparing an electric field-assisted sintering SrTiO3-based giant dielectric ceramic material according to claim 1, characterized in that: The sintered dog-bone-shaped sample was cut into small pieces, then polished and cleaned. Silver paste was coated onto the surface of the cut samples, and the ceramic material coated with silver electrodes was heat-treated to obtain Sr. 1-1.5x Y x TiO3, x =0~0.018 giant dielectric ceramic material.

8. A Sr according to claim 8 1-1.5x Y x TiO3, x A method for preparing giant dielectric ceramic materials with a dielectric constant of 0~0.018, characterized in that, The heat treatment conditions for the ceramic material coated with silver electrodes are: heat treatment at 650~750℃ for 10~20min.

9. A method for preparing an electric field-assisted sintering SrTiO3-based giant dielectric ceramic material according to claim 7 or 8, characterized in that, The prepared Sr 1-1.5x Y x TiO3, x =0~0.018 giant dielectric ceramic material.

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