A wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material and its preparation method
By employing a chemical composition of (Na0.3+xBi0.38-0.2xSr0.28-0.7x)(Ti1-xNbx)O3 with A and B site composite doping and a simple preparation process, the problem of poor dielectric stability of sodium bismuth titanate-based ceramics has been solved, achieving high dielectric constant and low dielectric loss over a wide temperature range, making it suitable for high-end electronic devices.
Patent Information
- Application Number
- CN202411060790.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-02
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2044-08-02
AI Technical Summary
Existing sodium bismuth titanate-based ceramics suffer from poor dielectric stability, low dielectric constant, and high loss, and their fabrication processes are demanding, making it difficult to meet the application requirements of high-end electronic devices in a wide temperature range.
Using the chemical composition (Na0.3+xBi0.38-0.2xSr0.28-0.7x)(Ti1-xNbx)O3, polar nanoregions of various structural types are formed through A- and B-site composite doping. Combined with simple preparation processes such as wet ball milling, dry pressing, and sintering in air atmosphere, a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material is prepared.
It maintains high dielectric constant and low dielectric loss over a wide temperature range, is safe and non-toxic, and has a simple preparation method that is easy to industrialize, reducing energy consumption and preparation costs.
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Figure CN118955123B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of piezoelectric ceramic materials technology, and in particular to a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material and its preparation method. Background Technology
[0002] Sodium bismuth titanate-based ceramics, as a novel lead-free relaxor ferroelectric material, have attracted considerable attention due to their excellent dielectric properties and wide-temperature stability. In modern electronic devices, capacitors, as key passive components, perform multiple functions such as voltage smoothing, pulse discharge, and filtering. With the rapid development of technology, especially in high-end applications such as 5G communication, electric vehicles, and aerospace, the performance requirements for capacitors are becoming increasingly stringent, particularly regarding stability over high temperatures and wide temperature ranges. Traditional ceramic capacitor dielectric materials, such as BaTiO3 and its modified systems, while meeting performance requirements within a certain temperature range, exhibit a sharp deterioration in the temperature stability of their dielectric properties at higher temperatures, limiting their application in extreme environments. Furthermore, these materials may contain harmful elements such as lead, posing a threat to the environment and human health. Therefore, developing environmentally friendly, high-performance alternative materials is of paramount importance.
[0003] Sodium bismuth titanate-based ceramics have become a research hotspot due to their high Curie temperature, low dielectric loss, and excellent dielectric temperature stability. This material exhibits a unique perovskite structure, with Na and Bi co-occupying the A-site and Ti occupying the B-site, resulting in stable dielectric properties over a wide temperature range. This is particularly true through doping modification, such as the addition of Sr. 0.53 Ba 0.47 Nb₂O₆ can further improve its dielectric constant and temperature stability, achieving stable operation in a temperature range from room temperature to 400℃ or even higher. However, the preparation process of sodium bismuth titanate-based ceramics is relatively complex, requiring precise control of multiple factors such as chemical composition, sintering temperature, and time to achieve optimal performance. Furthermore, the microstructure of the material has a significant impact on its macroscopic dielectric properties; therefore, fundamental research on grain growth and phase transition behavior is also crucial.
[0004] In summary, the research background of sodium bismuth titanate-based ceramics focuses on developing high-performance capacitor dielectric materials with wide temperature range stability to meet the application requirements of high-end electronic devices in harsh environments and promote the development of lead-free and environmentally friendly materials. Future research will continuously optimize the preparation process and deepen the understanding of the material's physical mechanisms to achieve even higher performance sodium bismuth titanate-based ceramic capacitor dielectric materials. Summary of the Invention
[0005] The purpose of this invention is to provide a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material and its preparation method, solving the problems of poor dielectric stability, low dielectric constant, high loss, and harsh preparation process conditions of existing sodium bismuth titanate-based piezoelectric ceramics.
[0006] To achieve the above objectives, the present invention provides a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material, wherein the general chemical formula of the ceramic capacitor dielectric material is: (Na 0.3 Bi 0.38 Sr 0.28 TiO3.
[0007] A wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material, wherein the general chemical formula of the ceramic capacitor dielectric material is: (Na 0.3+x Bi 0.38-0.2x Sr 0.28-0.7x (Ti) 1-x Nb x O3, 0 <x≤0.1。
[0008] The preparation method of the above-mentioned wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0009] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0010] S2, Pre-firing: After drying the slurry, pre-firing is performed;
[0011] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry;
[0012] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0013] S5. Dry pressing: Using a tablet press, fine powder is pressed into thin round tablets;
[0014] S6. Debinding: Debinding the formed thin disc at high temperature to obtain a ceramic blank;
[0015] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0016] Preferably, in step S1, the milling medium is anhydrous ethanol, the milling jar is a nylon jar, the milling balls are zirconium balls, the milling speed is 400 r / min, and the milling time is 12-16 hours.
[0017] Preferably, in step S2, the slurry is pre-fired in a corundum crucible at a temperature of 900°C for 4 hours.
[0018] Preferably, in step S3, the secondary ball milling medium is anhydrous ethanol, and the ball milling time is 8-12 hours.
[0019] Preferably, in step S4, a polyvinyl alcohol aqueous solution of 6wt% to 8wt% by mass is added to the dry powder, which is then dried and ground for 5 to 15 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder.
[0020] Preferably, in step S5, the pressure of the tablet press is 8 MPa and the holding time is 1 second.
[0021] Preferably, in step S6, the glue discharge temperature is 530℃-580℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 530℃-580℃ and held for 3 hours at the same heating rate.
[0022] Preferably, in step S7, the ceramic blank is buried in a small crucible with coarse powder, the sintering temperature is 1100℃-1130℃, the sintering time is 6 hours-8 hours, and the cooling rate is 2℃ / min.
[0023] The advantages and positive effects of the wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material and its preparation method described in this invention are as follows:
[0024] 1. This invention improves the dielectric temperature stability and dielectric loss of bismuth titanate by using A- and B-site composite doping to create defects. Because (Na... 0.3+x Bi 0.38-0.2x Sr 0.28-0.7x (Ti) 1-x Nb x In O3 ceramics, the A site (Na) + Bi 3 + 、Sr 2+ ) and B position (Ti 4+ 、Nb 5+ The composite ion occupancy creates various types of polar nanoregions (PNRs) within the material, and the broad dielectric response with diffusion phase transition characteristics weakens the dielectric anomalous peak, thus maintaining stable dielectric properties over a wide temperature range. Simultaneously, with the increase of Na... + and Nb 5+The increased content of the Bi₂Ti₂O₇ second phase in the ceramic crystal structure leads to a lower sintering temperature and reduces volatilization losses at high temperatures, thus contributing to lower dielectric losses. This results in a high and stable dielectric constant (~2350±15%) and low dielectric loss (<5%) in the ceramic capacitor dielectric material over a wide high-temperature range (22℃~316℃), improving its performance. Furthermore, the ceramic capacitor dielectric material is non-toxic, highly safe, and reduces environmental pollution. The ceramic capacitor dielectric material prepared by this invention exhibits a dielectric constant ε at 1kHz. r =2350 (150℃), loss tanδ=0.032% (150℃), TCC 150℃ The ≤15% temperature range is 22℃-316℃.
[0025] 2. The present invention can obtain ceramic capacitor dielectric material by dry pressing under 8MPa pressure and sintering powder in air atmosphere. The preparation method is simple, easy to operate and easy to industrialize.
[0026] 3. The ceramic capacitor dielectric material described in this invention is sintered at a lower sintering temperature, which helps to save energy and reduce manufacturing costs.
[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0028] Figure 1 This is a flowchart of an embodiment of the present invention;
[0029] Figure 2 These are X-ray diffraction analysis diagrams of the ceramic capacitor dielectric materials obtained in Examples 1-4 of this invention;
[0030] Figure 3 This is a schematic diagram showing the relative permittivity and dielectric loss of the ceramic capacitor dielectric material obtained in Examples 1-4 of the present invention as a function of temperature at 1 kHz.
[0031] Figure 4 The graph shows the change rate of capacitance-temperature of the ceramic capacitor dielectric material obtained in Examples 1-4 of the present invention as a function of temperature at a frequency of 1 kHz (based on 150 °C). Detailed Implementation
[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0033] A wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material, with the general chemical formula: (Na 0.3+ x Bi 0.38-0.2x Sr 0.28-0.7x (Ti)1-x Nb x O3, 0≤x≤0.1.
[0034] The preparation method of the above-mentioned wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0035] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0036] The raw materials contain 99.8% Na2CO3, 98% TiO2, 99.5% Nb2O5, 99% SrCO3, and 99% Bi2O3.
[0037] The grinding media is anhydrous ethanol, the grinding jar is a nylon jar, the grinding balls are zirconium balls, the grinding speed is 400 r / min, and the grinding time is 12-16 hours.
[0038] S2. Pre-firing: The slurry is dried to obtain a uniformly mixed powder. The powder is then pre-firing in an alumina crucible.
[0039] The preheating temperature is 900℃ and the preheating time is 4 hours.
[0040] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry.
[0041] The secondary ball milling medium was anhydrous ethanol, and the ball milling time was 8-12 hours.
[0042] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0043] Add 6 wt% to 8 wt% polyvinyl alcohol aqueous solution to the dry powder, dry it, and then grind it for 5 to 15 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder, which are then packaged separately.
[0044] S5. Dry pressing: Use a tablet press to press fine powder into thin round tablets.
[0045] The tablet press operates at a pressure of 8 MPa and a holding time of 1 second.
[0046] S6. Debinding: The formed thin disc is debinded at high temperature to obtain a ceramic blank.
[0047] The glue discharge temperature is 530℃-580℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 530℃-580℃ and held for 3 hours at the same heating rate.
[0048] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0049] The ceramic blank is buried in a small crucible with coarse powder, and the sintering temperature is 1100℃-1130℃, the sintering time is 6 hours-8 hours, and the cooling rate is 2℃ / min.
[0050] Example 1
[0051] When x = 0, the general chemical formula of the ceramic capacitor dielectric material is: (Na) 0.3 Bi 0.38 Sr 0.28 TiO3.
[0052] A method for preparing a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0053] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0054] The raw materials contain 99.8% Na2CO3, 98% TiO2, 99.5% Nb2O5, 99% SrCO3, and 99% Bi2O3.
[0055] The grinding media was anhydrous ethanol, the grinding jar was made of nylon, the grinding balls were zirconium balls, the grinding speed was 400 r / min, and the grinding time was 14 hours.
[0056] S2. Pre-firing: The slurry is dried to obtain a uniformly mixed powder. The powder is then pre-firing in an alumina crucible.
[0057] The preheating temperature is 900℃ and the preheating time is 4 hours.
[0058] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry.
[0059] The secondary ball milling medium was anhydrous ethanol, and the ball milling time was 10 hours.
[0060] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0061] Add 7 wt% polyvinyl alcohol aqueous solution to the dry powder, dry it, and then grind it for 10 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder, which are then packaged separately.
[0062] S5. Dry pressing: Use a tablet press to press fine powder into thin round tablets.
[0063] The tablet press operates at a pressure of 8 MPa and a holding time of 1 second.
[0064] S6. Debinding: The formed thin disc is debinded at high temperature to obtain a ceramic blank.
[0065] The glue discharge temperature is 550℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 550℃ and held for 3 hours at the same heating rate.
[0066] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0067] The ceramic blank was buried in a small crucible with coarse powder, and the sintering temperature was 1120℃, the sintering time was 7 hours, and the cooling rate was 2℃ / min.
[0068] Example 2
[0069] x = 0.025, the general chemical formula of the ceramic capacitor dielectric material is: (Na 0.325 Bi 0.375 Sr 0.2625 (Ti) 0.975 Nb 0.025 )O3.
[0070] A method for preparing a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0071] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0072] The raw materials contain 99.8% Na2CO3, 98% TiO2, 99.5% Nb2O5, 99% SrCO3, and 99% Bi2O3.
[0073] The grinding media was anhydrous ethanol, the grinding jar was made of nylon, the grinding balls were zirconium balls, the grinding speed was 400 r / min, and the grinding time was 14 hours.
[0074] S2. Pre-firing: The slurry is dried to obtain a uniformly mixed powder. The powder is then pre-firing in an alumina crucible.
[0075] The preheating temperature is 900℃ and the preheating time is 4 hours.
[0076] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry.
[0077] The secondary ball milling medium was anhydrous ethanol, and the ball milling time was 10 hours.
[0078] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0079] Add 7 wt% polyvinyl alcohol aqueous solution to the dry powder, dry it, and then grind it for 10 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder, which are then packaged separately.
[0080] S5. Dry pressing: Use a tablet press to press fine powder into thin round tablets.
[0081] The tablet press operates at a pressure of 8 MPa and a holding time of 1 second.
[0082] S6. Debinding: The formed thin disc is debinded at high temperature to obtain a ceramic blank.
[0083] The glue discharge temperature is 550℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 550℃ and held for 3 hours at the same heating rate.
[0084] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0085] The ceramic blank was buried in a small crucible with coarse powder, and the sintering temperature was 1120℃, the sintering time was 7 hours, and the cooling rate was 2℃ / min.
[0086] Example 3
[0087] x = 0.05, the general chemical formula of the ceramic capacitor dielectric material is: (Na 0.35 Bi 0.37 Sr 0.245 (Ti) 0.95 Nb 0.05 )O3.
[0088] A method for preparing a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0089] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0090] The raw materials contain 99.8% Na2CO3, 98% TiO2, 99.5% Nb2O5, 99% SrCO3, and 99% Bi2O3.
[0091] The grinding media was anhydrous ethanol, the grinding jar was made of nylon, the grinding balls were zirconium balls, the grinding speed was 400 r / min, and the grinding time was 16 hours.
[0092] S2. Pre-firing: The slurry is dried to obtain a uniformly mixed powder. The powder is then pre-firing in an alumina crucible.
[0093] The preheating temperature is 900℃ and the preheating time is 4 hours.
[0094] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry.
[0095] The secondary ball milling medium was anhydrous ethanol, and the ball milling time was 12 hours.
[0096] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0097] Add 7 wt% polyvinyl alcohol aqueous solution to the dry powder, dry it, and then grind it for 10 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder, which are then packaged separately.
[0098] S5. Dry pressing: Use a tablet press to press fine powder into thin round tablets.
[0099] The tablet press operates at a pressure of 8 MPa and a holding time of 1 second.
[0100] S6. Debinding: The formed thin disc is debinded at high temperature to obtain a ceramic blank.
[0101] The glue discharge temperature is 550℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 550℃ and held for 3 hours at the same heating rate.
[0102] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0103] The ceramic blank was buried in a small crucible with coarse powder, and the sintering temperature was 1100℃, the sintering time was 8 hours, and the cooling rate was 2℃ / min.
[0104] Example 4
[0105] x = 0.1, the general chemical formula of the dielectric material for ceramic capacitors is: (Na 0.4 Bi 0.36 Sr 0.21 (Ti) 0.9 Nb 0.1 )O3.
[0106] A method for preparing a wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps:
[0107] S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry.
[0108] The raw materials contain 99.8% Na2CO3, 98% TiO2, 99.5% Nb2O5, 99% SrCO3, and 99% Bi2O3.
[0109] The grinding media was anhydrous ethanol, the grinding jar was made of nylon, the grinding balls were zirconium balls, the grinding speed was 400 r / min, and the grinding time was 12 hours.
[0110] S2. Pre-firing: The slurry is dried to obtain a uniformly mixed powder. The powder is then pre-firing in an alumina crucible.
[0111] The preheating temperature is 900℃ and the preheating time is 4 hours.
[0112] S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry.
[0113] The secondary ball milling medium was anhydrous ethanol, and the ball milling time was 8 hours.
[0114] S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder.
[0115] Add 8 wt% polyvinyl alcohol aqueous solution to the dry powder, dry it, and then grind it for 10 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder, which are then packaged separately.
[0116] S5. Dry pressing: Use a tablet press to press fine powder into thin round tablets.
[0117] The tablet press operates at a pressure of 8 MPa and a holding time of 1 second.
[0118] S6. Debinding: The formed thin disc is debinded at high temperature to obtain a ceramic blank.
[0119] The glue discharge temperature is 550℃, the heating rate is 1℃ / min, the temperature is raised to 120℃ and held for 1 hour, and then the temperature is raised to 550℃ and held for 3 hours at the same heating rate.
[0120] S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in an air atmosphere using a muffle furnace to obtain the ceramic capacitor dielectric material.
[0121] The ceramic blank was buried in a small crucible with coarse powder, and the sintering temperature was 1130℃, the sintering time was 7 hours, and the cooling rate was 2℃ / min.
[0122] X-ray diffraction analysis was performed on the ceramic capacitor dielectric materials obtained in Examples 1-4, and the results are as follows: Figure 2 As shown, there are 7 characteristic peaks between 20° and 80°, which are (100), (110), (111), (200), (211), (220), and (310) as the angle increases, indicating that the ceramic material is a perovskite ceramic. The (111) and (200) diffraction peaks are split, indicating that the sample has a pseudo-cubic phase structure. There are impurity peaks near the diffraction peaks at 30°, 50°, and 60°, indicating the introduction of Na. + and Nb 5+ This leads to the formation of a second phase, Bi2Ti2O7.
[0123] Figure 3 This is a schematic diagram illustrating the relative permittivity and dielectric loss of the ceramic capacitor dielectric material described in Embodiments 1-4 of the present invention as a function of temperature at 1 kHz. Figure 3 As shown, the relative permittivity ε r In the temperature-dependent curves, Examples 1-3 show two dielectric anomalous peaks, while Example 4 shows only one obvious dielectric anomalous peak. The graph clearly shows that at x = 0.025, the relative permittivity is at a relatively high level, reflecting that doping improves the relative permittivity to some extent; however, excessive doping can lead to a decrease in the permittivity. The dielectric loss tanδ decreases with increasing doping concentration.
[0124] Figure 4 The graph shows the change rate of capacitance-temperature (based on 150°C) of the ceramic capacitor dielectric materials prepared in Examples 1-4 at a frequency of 1 kHz as a function of temperature.
[0125] The capacitance-temperature change rate and dielectric loss of the ceramic capacitor dielectric materials prepared in Examples 1-4 were compared, and the results are shown in Table 1.
[0126] Table 1. Properties of ceramic capacitor dielectric materials prepared in Examples 1-4
[0127]
[0128] It is evident that the ceramic capacitor dielectric material prepared using the method described in this invention exhibits a high relative permittivity, low dielectric loss, and a stable capacitance-temperature change rate. If the capacitance-temperature change rate is required to be ≤15%, the temperature range of Example 2 is 22-316℃, demonstrating superior overall performance.
[0129] Therefore, the wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material and its preparation method described in this invention can solve the problems of poor dielectric stability, low dielectric constant, high loss, and harsh preparation process conditions of existing sodium bismuth titanate-based piezoelectric ceramics.
[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material, characterized in that: The general chemical formula of the ceramic capacitor dielectric material is: (Na) 0.3+x Bi 0.38-0.2x Sr 0.28-0.7x (Ti) 1-x Nb x O3, x＝0.025； The preparation method of the above-mentioned wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material includes the following steps: S1. Batching and primary ball milling: Weigh analytically pure raw materials according to molar percentage. The raw materials include bismuth oxide (Bi2O3), sodium carbonate (Na2CO3), titanium dioxide (TiO2), strontium carbonate (SrCO3), and niobium pentoxide (Nb2O5). Mix the raw materials and wet ball mill them using a planetary ball mill to obtain a uniformly mixed primary slurry. S2, Pre-firing: After drying the slurry, pre-firing is performed; S3. Secondary ball milling: The pre-calcined powder is ball milled a second time using a planetary ball mill to obtain a uniformly mixed secondary slurry; S4. Granulation: After drying the secondary slurry, dry powder is obtained. The dry powder is granulated and sieved to obtain fine powder and coarse powder. S5. Dry pressing: The fine powder is pressed into thin round tablets using a tablet press. The pressure of the tablet press is 8MPa and the holding time is 1 second. S6. Debinding: Debinding the formed thin disc at high temperature to obtain a ceramic blank; S7. Sintering: The ceramic blank is buried with coarse powder and sintered at high temperature in air atmosphere in a muffle furnace to obtain ceramic capacitor dielectric material. The ceramic blank is buried in a small crucible with coarse powder. The sintering temperature is 1100℃-1130℃, the sintering time is 6 hours-8 hours, and the cooling rate is 2℃ / min.
2. The wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material according to claim 1, characterized in that: In step S1, the milling medium is anhydrous ethanol, the milling jar is a nylon jar, the milling balls are zirconium balls, the milling speed is 400 r / min, and the milling time is 12-16 hours.
3. The wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material according to claim 1, characterized in that: In step S2, the slurry is pre-fired in a corundum crucible at a temperature of 900°C for 4 hours.
4. The wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material according to claim 1, characterized in that: In step S3, the secondary ball milling medium is anhydrous ethanol, and the ball milling time is 8-12 hours.
5. The wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material according to claim 1, characterized in that: In step S4, a polyvinyl alcohol aqueous solution of 6wt%-8wt% by mass is added to the dry powder, and after drying, it is ground for 5-15 minutes. The ground powder is then sieved through a 120-mesh sieve to obtain fine powder and coarse powder.
6. The wide-temperature-range stable sodium bismuth titanate-based ceramic capacitor dielectric material according to claim 1, characterized in that: In S6, the glue discharge temperature is 530℃-580℃, and the heating rate is 1℃ / min.