A high energy storage density sodium niobate-based lead-free ceramic dielectric material and preparation thereof

Abstract

The application relates to the technical field of dielectric materials, in particular to a high-energy-density sodium niobate-based lead-free ceramic dielectric material and a preparation method thereof. 0.5 Na 0.5 TiO3)‑xSr 0.7 Bi 0.2 TiO3+0.1‑0.2wt%MnCO3 wherein x=0‑0.10, and the preparation method comprises the following steps: according to the chemical formula, mixing raw materials, and sequentially performing primary ball milling, discharging, drying, pre-sintering, adding MnCO3, secondary ball milling, drying, sieving, flow casting, isostatic pressing treatment, glue removal and sintering to obtain the sodium niobate-based ceramic dielectric material. Compared with the prior art, the material provided by the application has the advantages of high breakdown electric field strength, slender hysteresis loop, excellent energy storage characteristics and the like.

Description

Technical Field

[0001] This invention relates to the field of dielectric materials technology, and in particular to a high energy density sodium niobate-based lead-free ceramic dielectric material and its preparation. Background Technology

[0002] Energy is the material foundation upon which human society depends for survival and development. With the comprehensive development of social modernization, the demand for energy is increasing daily. How to efficiently utilize energy has become a focus of common concern for countries worldwide. Furthermore, the rapid development of miniaturization and integration of electronic components places even higher demands on the performance of materials. Ceramic dielectric capacitors, due to their fast charging and discharging speeds, high power density, long cycle life, wide operating temperature range, and good safety, are widely used in important fields such as aerospace, medical devices, automotive electronics, and laser weapons. Lead-based antiferroelectric materials dominate the ceramic dielectric capacitor market due to their excellent energy storage and discharge characteristics. However, the environmental and health hazards of lead make the development of environmentally friendly lead-free dielectric energy storage materials an urgent priority.

[0003] Perovskite inorganic materials based on barium titanate, sodium bismuth titanate, strontium titanate, potassium sodium niobate, silver niobate, and sodium niobate have become some of the main lead-free energy storage ceramic systems currently under research. Among them, sodium niobate-based ceramics, as an important member of the lead-free antiferroelectric system, have attracted widespread attention in the field of dielectric energy storage due to their characteristics such as low theoretical density, high polarization intensity and Curie temperature, and rich phase structure. However, the antiferroelectric phase of sodium niobate-based ceramics easily transforms into a metastable ferroelectric phase under the induction of a high electric field, thus exhibiting a square saturated hysteresis loop with ferroelectric characteristics. This results in high leakage conductance and losses at high fields, making it difficult to obtain a high breakdown electric field, which is detrimental to achieving high energy storage density. To this end, various methods have been employed to reduce the leakage and loss of sodium niobate-based ceramics, thereby further improving their energy storage density. Patent (application number CN202211407274) utilizes appropriate amounts of Ba(Fe) 0.5 Nb 0.5 O3 doping into a NaNbO3 matrix yields 0.97–4 J / cm³ at room temperature. 3 The energy storage density is 55.8%–82.4%. To date, the energy storage density and energy storage efficiency of sodium niobate-based lead-free energy storage ceramics are both 5 J / cm³. 3 With a purity below 85%, it is difficult to simultaneously obtain sodium niobate-based ceramics that possess high energy density, high energy storage efficiency, and low loss, thus limiting the application of this system in the field of dielectric energy storage. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a high energy density sodium niobate-based lead-free ceramic dielectric material and its preparation.

[0005] This material can significantly improve the energy storage density and efficiency of lead-free energy storage ceramics, as well as their resistance to breakdown electric fields. The ceramics obtained by this invention have high breakdown field strength, excellent energy storage characteristics, simple preparation process, good uniformity of ceramic samples, high reliability, and are lead-free and pollution-free, which is conducive to promoting the development of next-generation electronic components.

[0006] This invention is the first to utilize 0.75NaNbO3-0.25Bi... 0.5 Na 0.5 In TiO3, where x = 0-0.10, a certain amount of Sr is introduced into the binary system. 0.7 Bi 0.2 TiO3 content, and the addition of an appropriate amount of MnCO3 to reduce the prepared NaNbO3-Bi 0.5 Na 0.5 TiO3-Sr 0.7 Bi 0.2 The leakage conductance of TiO3 material is reduced, thereby improving its insulation. While maintaining the high saturation polarization intensity of sodium niobate, the leakage conductance is significantly reduced, the residual polarization intensity is decreased, and the breakdown electric field intensity is increased, resulting in a significant improvement in the energy storage density of sodium niobate-based lead-free ceramic dielectrics, which has significant practical application value.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A sodium niobate-based lead-free ceramic dielectric material, the chemical composition of which is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3 + 0.1-0.2 wt% MnCO3, where x = 0-0.10. A method for preparing a sodium niobate-based lead-free ceramic dielectric material includes the following steps:

[0009] S1: According to the general chemical formula of sodium niobate-based lead-free ceramic dielectric materials, bismuth source, sodium source, titanium source, strontium source and niobium source are mixed and then subjected to ball milling, discharge, drying and pre-firing in sequence to obtain pre-synthesized ceramic powder;

[0010] S2: Add MnCO3 to the pre-synthesized ceramic powder obtained in S1 and ball mill it a second time. Then dry and sieve to obtain the raw material powder of sodium niobate-based lead-free ceramic media material. Add organic solvent, emulsifier, plasticizer, binder and dispersant to the raw material powder of sodium niobate-based lead-free ceramic media material and mix evenly to obtain a slurry of sodium niobate-based lead-free ceramic media material. Then obtain a ceramic film by casting. Perform isostatic pressing treatment, debinding and sintering on the ceramic film to obtain the sodium niobate-based ceramic media material.

[0011] Furthermore, the bismuth source includes Bi2O3, the sodium source includes Na2CO3, the titanium source includes TiO2, the strontium source includes SrCO3, and the niobium source includes Nb2O5.

[0012] Furthermore, the conditions for the primary and secondary ball milling processes are as follows: anhydrous ethanol and ZrO2 balls are used as the ball milling media, wherein the mass ratio of ZrO2 balls, anhydrous ethanol and raw materials is (2.2-2.6):(1.4-1.6):1, the ball milling speed is 420-460 r / min, and the ball milling time is 20-23 h.

[0013] Furthermore, in step S1, the pre-firing temperature is 800-850℃, and the pre-firing time is 4-8h.

[0014] Furthermore, in step S2, the emulsifier is selected from trioleic acid glyceride, the plasticizer is selected from dibutyl phthalate, the binder is selected from polyvinyl butyral, and the dispersant is selected from polyethylene glycol.

[0015] Furthermore, the amount of emulsifier added is 2.8-3.2% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic media material; the amount of plasticizer added is 2.8-3.2% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic media material; the amount of binder added is 10-12% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic media material; and the amount of dispersant added is 2.8-3.2% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic media material.

[0016] Furthermore, in step S2, the isostatic pressure treatment is performed by applying pressures of 50MPa, 100MPa, 150MPa and 200MPa sequentially at a temperature of 70-80℃.

[0017] Furthermore, in step S2, the sintering process specifically involves heating to 1200-1300℃ at a heating rate of 2.5-3.5℃ / min and calcining at a constant temperature for 2-4 hours.

[0018] Furthermore, in step S2, the temperature for discharging the adhesive is 550-600℃, and the discharging time is 20-24h.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The sodium niobate-based lead-free ceramic dielectric material prepared by this invention has high breakdown electric field strength, long hysteresis loop and excellent energy storage characteristics, which has great practical value for realizing lead-free, miniaturized and integrated electronic components.

[0021] (2) This invention utilizes 0.75NaNbO3-0.25Bi 0.5 Na 0.5 Introducing a certain amount of Sr into the TiO3 binary system 0.7 Bi 0.2 TiO3 content, and the addition of an appropriate amount of MnCO3 to reduce the prepared NaNbO3-Bi 0.5 Na 0.5 TiO3-Sr 0.7 Bi 0.2 The leakage conductance of TiO3 material is reduced, thereby improving its insulation. While maintaining the high saturation polarization intensity of sodium niobate, the leakage conductance is significantly reduced, the residual polarization intensity is decreased, and the breakdown electric field intensity is increased, resulting in a significant improvement in the energy storage density of sodium niobate-based lead-free ceramic dielectrics, which has significant practical application value. Attached Figure Description

[0022] Figure 1 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 1;

[0023] Figure 2 The curves showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 1 as a function of electric field strength are shown.

[0024] Figure 3 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 2;

[0025] Figure 4 The curves showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 2 as a function of electric field strength are shown.

[0026] Figure 5 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 3;

[0027] Figure 6 The curves showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 3 as a function of electric field strength are shown.

[0028] Figure 7 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 4;

[0029] Figure 8 The curves showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 4 as a function of electric field strength are shown.

[0030] Figure 9 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 11;

[0031] Figure 10 The curve showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 11 as a function of electric field strength is shown.

[0032] Figure 11 The hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 12;

[0033] Figure 12 The curves showing the energy storage characteristics of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 12 as a function of electric field strength are shown. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] A sodium niobate-based lead-free ceramic dielectric material, the chemical composition of which is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3 + 0.1-0.2wt% MnCO3, where x = 0-0.10.

[0036] A method for preparing a sodium niobate-based lead-free ceramic dielectric material includes the following steps:

[0037] S1: Bi₂O₃, SrCO₃, TiO₂, Na₂CO₃, and Nb₂O₅ are selected as bismuth, strontium, titanium, sodium, and niobium sources, respectively, according to (1-x)(0.75NaNbO₃-0.25Bi 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3 was mixed in stoichiometric proportions and then successively subjected to ball milling, discharge, drying, and pre-calcination to obtain pre-synthesized ceramic powder.

[0038] In some specific embodiments of the present invention, the specific conditions for a single ball milling are as follows: anhydrous ethanol and ZrO2 balls are used as the ball milling medium, the mass ratio of ZrO2 balls, anhydrous ethanol and raw materials is 2.5:1.5:1, the ball milling speed is 430 r / min, and the ball milling time is 22 h.

[0039] S2: Add MnCO3 to the pre-synthesized ceramic powder obtained in S1 and ball mill it a second time. Then dry it at 100°C and sieve it (sieve mesh number of 200) to obtain the raw material powder of sodium niobate-based lead-free ceramic media material. Add organic solvent, emulsifier, plasticizer, binder and dispersant to the raw material powder of sodium niobate-based lead-free ceramic media material and mix them evenly to obtain the slurry of sodium niobate-based lead-free ceramic media material. Then obtain a ceramic film by casting, and perform isostatic pressing, debinding and sintering on the ceramic film to obtain the sodium niobate-based ceramic media material.

[0040] In some specific embodiments of the present invention, the specific conditions for secondary ball milling are as follows: anhydrous ethanol and ZrO2 balls are used as the ball milling medium, the mass ratio of ZrO2 balls, anhydrous ethanol and raw materials is 2.5:1.5:1, the ball milling speed is 430 r / min, and the ball milling time is 12 h.

[0041] In some specific embodiments of the present invention, the pre-firing temperature is 800-850°C and the pre-firing time is 4-8 hours, preferably 850°C for 8 hours.

[0042] In some specific embodiments of the present invention, the emulsifier is selected as trioleic acid glyceride, the plasticizer is selected as dibutyl phthalate, the binder is selected as polyvinyl butyral, and the dispersant is selected as polyethylene glycol.

[0043] The amount of emulsifier added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic dielectric material, preferably 3%.

[0044] The amount of plasticizer added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic dielectric material, preferably 3%.

[0045] The amount of binder added is 10-12% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic dielectric material, preferably 11%.

[0046] The amount of dispersant added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic media material, preferably 3%.

[0047] In some specific embodiments of the present invention, the organic solvent is a mixture of anhydrous ethanol and butanone, wherein the amount of anhydrous ethanol added is 50-55% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic dielectric material, and the amount of butanone added is 100-105% of the mass of the raw material powder of the sodium niobate-based lead-free ceramic dielectric material.

[0048] In some specific embodiments of the present invention, the isostatic pressing conditions are as follows: pressurization is performed sequentially at a temperature of 70-80°C using pressures of 50MPa, 100MPa, 150MPa and 200MPa, with the preferred temperature being 80°C.

[0049] In some specific embodiments of the present invention, the sintering process is as follows: heating to 1200-1300°C at a heating rate of 2.5-3.5°C / min, and calcining at a constant temperature for 2-4 hours, preferably heating from room temperature to 1250°C at a heating rate of 3.5°C / min and holding at that temperature for 4 hours.

[0050] In some specific embodiments of the present invention, the glue discharge temperature is 550-600℃ and the glue discharge time is 20-24h. Preferably, the glue discharge temperature is 600℃ and the glue discharge time is 20h.

[0051] The following embodiments are implemented based on the above-described technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0052] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0053] In the following embodiments, unless otherwise specified, the raw materials, reagents, or processing techniques are all conventional commercially available products or conventional processing techniques in the art. Pre-firing, sintering, and debinding are all carried out in an air atmosphere.

[0054] Example 1

[0055] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0, and the composition is 0.75NaNbO3-0.25Bi 0.5 Na 0.5 TiO3.

[0056] The specific preparation method is as follows:

[0057] (1) According to the chemical formula (1-x)(0.75NaNbO3-0.25Bi) 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2TiO3 (where x = 0) is prepared by weighing raw materials Bi2O3, SrCO3, TiO2, Na2CO3, and Nb2O5, and mixing them uniformly through a single ball milling process to obtain the initial raw material powder. During ball milling, anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mass ratio of ZrO2 balls to raw materials is 2.5:1, and the mass ratio of anhydrous ethanol to raw materials is 1.5:1. The ball mill speed is 430 r / min, and the ball milling time is 20 h. After drying, the powder is prepared.

[0058] (2) The dried raw material powder was pre-fired at 850°C for 8 hours under sealed conditions to obtain pre-synthesized ceramic powder;

[0059] (3) Add 0.1wt% MnCO3 (the mass concentration here refers to the mass content of MnCO3 in the final product ceramic media material) to the pre-synthesized ceramic powder and perform secondary ball milling. Dry the slurry after ball milling at 100℃. During ball milling, anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mass ratio of ZrO2 balls to raw materials is 2.5:1, the mass ratio of anhydrous ethanol to raw materials is 1.5:1, the speed of the ball mill is 430r / min, and the ball milling time is 12h.

[0060] (4) Pass the dried raw material powder from step (3) through a 200-mesh sieve to obtain the raw material powder for sodium niobate-based lead-free ceramic media material;

[0061] (5) The obtained raw material powder is mixed evenly with organic solvent, emulsifier, plasticizer, binder, and dispersant to obtain a slurry of sodium niobate-based lead-free ceramic dielectric material. The organic solvent is a mixture of anhydrous ethanol and methyl ethyl ketone (MEK); the emulsifier is triolein; the plasticizer is dibutyl phthalate; the binder is polyvinyl butyral; and the dispersant is polyethylene glycol. The amount of anhydrous ethanol added is 55% of the raw material powder mass; the amount of MEK added is 105% of the raw material powder mass; the amount of triolein added is 3% of the raw material powder mass; the amount of polyvinyl butyral added is 10% of the raw material powder mass; the amount of polyethylene glycol added is 3% of the raw material powder mass; and the amount of dibutyl phthalate added is 3% of the raw material powder mass.

[0062] (6) The obtained ceramic slurry is prepared into a ceramic film by casting process, and then cut into 10mm×10mm square pieces. At 80℃, pressure of 50MPa, 100MPa, 150MPa and 200MPa is applied in sequence, and each pressure is held for 5 minutes to obtain sodium niobate-based lead-free ceramic media green body.

[0063] (7) The obtained ceramic blank was kept at 600℃ for 20h for debinding treatment. Then, the debinded ceramic blank was heated to 1250℃ at a heating rate of 3.5℃ / min under sealed conditions and kept at that temperature for 4h. Finally, it was cooled to room temperature with the furnace to obtain sodium niobate-based lead-free ceramic dielectric material.

[0064] Gold electrodes were deposited on both sides of the obtained sodium niobate-based lead-free ceramic dielectric material using ion sputtering (sputtering current 25 mA, sputtering time 10 min, electrode area 3.14 mm²). 2 The hysteresis loop of the material was tested using a ferroelectric testing system (Precision Premier II, USA) at room temperature and 10 Hz. Its energy storage characteristics can be calculated using the following formula:

[0065]

[0066]

[0067]

[0068] In the formula W tot W represents the total energy storage density. rec W represents the energy density that can be released. loss This represents the energy loss density. P is the polarization intensity, P max For the maximum polarization intensity, P r The remaining polarization intensity.

[0069] Figure 1 The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 1, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this example is long and thin, with a high breakdown electric field strength, reaching a maximum electric field strength of 720 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 2 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–720 kV / cm, η stabilizes around 65%. When the electric field strength reaches 700 kV / cm, W… tot =10.18J / cm 3 W rec =6.96J / cm 3 Wloss =3.22J / cm 3 The corresponding η is 68.41%.

[0070] Example 2

[0071] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0.02, and other steps are the same as in Example 1.

[0072] Figure 3 The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 2, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this invention is slender, with a high breakdown electric field strength, reaching a maximum electric field strength of 760 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 4 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–760 kV / cm, η stabilizes around 72%. When the electric field strength reaches 760 kV / cm, W… tot =12.79J / cm 3 W rec = 9.63 J / cm 3 W loss =3.16J / cm 3 The corresponding η is 75.31%.

[0073] Example 3

[0074] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0.04, and other steps are the same as in Example 1.

[0075] Figure 5 The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 3, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this invention is slender, with a high breakdown electric field strength, reaching a maximum electric field strength of 820 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 6 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–820 kV / cm, η stabilizes around 80%. When the electric field strength reaches 820 kV / cm, W… tot =12.61J / cm 3 W rec =10.33J / cm 3 W loss =2.28J / cm 3 The corresponding η is 81.96%.

[0076] Example 4

[0077] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0.06, and other steps are the same as in Example 1.

[0078] The specific steps are as follows:

[0079] (1) According to the chemical formula (1-x)(0.75NaNbO3-0.25Bi) 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2TiO3 (where x = 0.06) was prepared by weighing raw materials Bi2O3, SrCO3, TiO2, Na2CO3, and Nb2O5, and mixing them uniformly through a single ball milling process to obtain the initial raw material powder. During ball milling, anhydrous ethanol and ZrO2 balls were used as the ball milling media. The mass ratio of ZrO2 balls to raw materials was 2.5:1, and the mass ratio of anhydrous ethanol to raw materials was 1.5:1. The ball mill speed was 430 r / min, and the ball milling time was 20 h. The powder was then dried.

[0080] (2) The dried raw material powder was pre-fired at 850°C for 8 hours under sealed conditions to obtain pre-synthesized ceramic powder;

[0081] (3) Add 0.1wt% MnCO3 to the pre-synthesized ceramic powder and perform secondary ball milling. Dry the slurry after ball milling at 100℃. During ball milling, anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mass ratio of ZrO2 balls to raw materials is 2.5:1, the mass ratio of anhydrous ethanol to raw materials is 1.5:1, the speed of the ball mill is 430r / min, and the ball milling time is 12h.

[0082] (4) Pass the dried raw material powder from step (3) through a 200-mesh sieve to obtain the raw material powder for sodium niobate-based lead-free ceramic media material;

[0083] (5) The obtained raw material powder is mixed evenly with organic solvent, emulsifier, plasticizer, binder, and dispersant to obtain a slurry of sodium niobate-based lead-free ceramic dielectric material. The organic solvent is a mixture of anhydrous ethanol and methyl ethyl ketone (MEK); the emulsifier is triolein; the plasticizer is dibutyl phthalate; the binder is polyvinyl butyral; and the dispersant is polyethylene glycol. The amount of anhydrous ethanol added is 55% of the raw material powder mass; the amount of MEK added is 105% of the raw material powder mass; the amount of triolein added is 3% of the raw material powder mass; the amount of polyvinyl butyral added is 10% of the raw material powder mass; the amount of polyethylene glycol added is 3% of the raw material powder mass; and the amount of dibutyl phthalate added is 3% of the raw material powder mass.

[0084] (6) The obtained ceramic slurry is prepared into a ceramic film by casting process, and then cut into 10mm×10mm square pieces. At 80℃, pressure of 50MPa, 100MPa, 150MPa and 200MPa is applied in sequence, and each pressure is held for 5 minutes to obtain sodium niobate-based lead-free ceramic media green body.

[0085] (7) The obtained ceramic blank was kept at 600℃ for 20h for debinding treatment. Then, the debinded ceramic blank was heated to 1250℃ at a heating rate of 3.5℃ / min under sealed conditions and kept at that temperature for 4h. Finally, it was cooled to room temperature with the furnace to obtain sodium niobate-based lead-free ceramic dielectric material.

[0086] Figure 7 The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 4, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this invention is slender, with a high breakdown electric field strength, reaching a maximum electric field strength of 870 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 8 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–870 kV / cm, η stabilizes around 84%. When the electric field strength reaches 870 kV / cm, W… tot =12.73J / cm 3 W rec =10.87J / cm 3 W loss =1.86J / cm 3 The corresponding η is 85.37%.

[0087] Example 5

[0088] The difference between this embodiment and Embodiment 4 lies in the specific process of the primary ball milling in step (1). In this embodiment, the primary ball milling process is as follows: anhydrous ethanol and ZrO2 balls are used as the milling media; the mass ratio of ZrO2 balls to raw materials is 2.5:1, and the mass ratio of anhydrous ethanol to raw materials is 1.5:1. The ball mill speed is 450 r / min, and the milling time is 15 h. All other steps are the same as in Embodiment 4. The final energy storage characteristics of the material remain almost unchanged.

[0089] Example 6

[0090] The difference between this embodiment and embodiment 4 lies in step (2). In this embodiment, the dried raw material powder is pre-fired at 900°C for 2 hours under sealed conditions to obtain pre-synthesized ceramic powder. All other steps are the same as in embodiment 4. The energy storage characteristics of the final material remain almost unchanged.

[0091] Example 7

[0092] The difference between this embodiment and embodiment 4 lies in the specific process of the secondary ball milling process in step (3). The secondary ball milling process in this embodiment is as follows: the mass ratio of ZrO2 balls to raw materials is 3:1, the mass ratio of anhydrous ethanol to raw materials is 1.5:1, the rotation speed of the ball mill is 450 r / min, and the ball milling time is 20 h. All other steps are the same as in embodiment 4. The energy storage characteristics of the final material remain almost unchanged.

[0093] Example 8

[0094] The difference between this embodiment and embodiment 4 lies in step (5). Step (5) in this embodiment is as follows:

[0095] The obtained raw material powder was first mixed evenly with an organic solvent, and then an emulsifier, plasticizer, binder, and dispersant were added and mixed evenly to obtain a slurry of sodium niobate-based lead-free ceramic dielectric material. The organic solvent was a mixture of anhydrous ethanol and methyl ethyl ketone (MEK); the emulsifier was triolein; the plasticizer was dibutyl phthalate (DBP); the binder was polyvinyl butyral; and the dispersant was polyethylene glycol (PEG). The amount of anhydrous ethanol added was 50% of the raw material powder mass; the amount of MEK added was 100% of the raw material powder mass; the amount of triolein added was 2.8% of the raw material powder mass; the amount of polyvinyl butyral added was 10% of the raw material powder mass; the amount of PEG added was 2.8% of the raw material powder mass; and the amount of DBP added was 2.8% of the raw material powder mass. All other steps were the same as in Example 4. The energy storage characteristics of the final material remained almost unchanged.

[0096] Example 9

[0097] The difference between this embodiment and Embodiment 4 lies in step (5). In this embodiment, the amount of anhydrous ethanol added is 55% of the raw material powder mass; the amount of butanone added is 105% of the raw material powder mass; the amount of trioleic acid glyceride added is 3% of the raw material powder mass; the amount of polyvinyl butyral added is 12% of the raw material powder mass; the amount of polyethylene glycol added is 3% of the raw material powder mass; and the amount of dibutyl phthalate added is 3% of the raw material powder mass. All other steps are the same as in Embodiment 4. The energy storage characteristics of the final material remain almost unchanged.

[0098] Example 10

[0099] The difference between this embodiment and embodiment 4 lies in step (7). In this embodiment, step (7) involves: holding the obtained ceramic green body at 550°C for 6 hours to remove the binder; then, heating the debinded ceramic green body to 1250°C under sealed conditions at a heating rate of 3°C / min and holding it for 6 hours; finally, cooling it to room temperature in the furnace to obtain sodium niobate-based lead-free high energy storage density and energy storage efficiency ceramic. All other steps are the same as in embodiment 4. The energy storage characteristics of the final material remain almost unchanged.

[0100] Example 11

[0101] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0.08, and other steps are the same as in Example 1.

[0102] Figure 9 The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 11, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this invention is slender, with a high breakdown electric field strength, reaching a maximum electric field strength of 880 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 10 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–880 kV / cm, η stabilizes around 84%. When the electric field strength reaches 880 kV / cm, W… tot =12.05J / cm 3 W rec =10.25J / cm 3 W loss =1.80J / cm 3 The corresponding η is 85.03%.

[0103] Example 12

[0104] This embodiment provides a sodium niobate-based lead-free ceramic dielectric material and its preparation method, wherein the ceramic chemical composition is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3, where x = 0.1, and other steps are the same as in Example 1.

[0105] Figure 11The figure shows the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in Example 12, measured at room temperature and 10 Hz. As can be seen from the figure, the hysteresis loop of the sodium niobate-based lead-free ceramic dielectric material prepared in this invention is slender, with a high breakdown electric field strength, reaching a maximum electric field strength of 900 kV / cm. The energy storage characteristics (total energy storage density W) are calculated based on the hysteresis loops under different electric field strengths. tot The available energy storage density W rec Energy loss density W loss The curves showing the variation of energy storage efficiency η with electric field intensity are as follows: Figure 12 As shown in the figure. It can be seen from the figure that W tot and W rec W increases rapidly with increasing electric field strength. loss It increases slowly with increasing electric field strength. Within the electric field strength range of 300–900 kV / cm, η stabilizes around 89%. When the electric field strength reaches 900 kV / cm, W… tot =11.53J / cm 3 W rec =10.28J / cm 3 W loss =1.25J / cm 3 The corresponding η is 89.17%.

[0106] Comparative Example 1

[0107] Compared with the sodium niobate-based lead-free ceramic media material structure of Example 4, this comparative example differs in that MnCO3 is not added, i.e., the step of adding MnCO3 in step (3) is omitted. The pre-synthesized ceramic powder is directly subjected to secondary ball milling, and the slurry after ball milling is dried at 100°C. During ball milling, anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mass ratio of ZrO2 balls to raw materials is 2.5:1, the mass ratio of anhydrous ethanol to raw materials is 1.5:1, the speed of the ball mill is 430 r / min, and the ball milling time is 12 h.

[0108] The sodium niobate-based lead-free ceramic dielectric material prepared in Comparative Example 1 was tested, and the results showed that η remained stable at around 80% within an electric field strength range of 100–600 kV / cm. When the electric field strength reached 600 kV / cm, W… tot =7.60 J / cm 3 W rec =6.18J / cm 3 W loss =1.42J / cm 3 The corresponding η is 81.25%.

[0109] Comparative Example 2

[0110] Compared with the sodium niobate-based lead-free ceramic dielectric material structure of Example 4, the difference in this comparative example is that the preparation process is changed to a solid-state reaction method. That is, 6 wt% PVA solvent is added to the sodium niobate powder obtained in step (4) to granulate the powder. After weighing 0.2 g of granulated powder, the powder is pressed (15 MPa for 5 min) to obtain a ceramic green body.

[0111] The obtained ceramic green body was held at 600℃ for 20 hours for debinding. Then, the debinded ceramic green body was heated to 1250℃ under sealed conditions at a heating rate of 3.5℃ / min and held for 4 hours. Finally, it was cooled to room temperature in the furnace to obtain sodium niobate-based lead-free ceramic dielectric material. The sintered ceramic material was then thinned to 100 micrometers for testing.

[0112] The sodium niobate-based lead-free ceramic dielectric material prepared in Comparative Example 2 was tested, and the results showed that η remained stable at around 75% within an electric field strength range of 100–400 kV / cm. When the electric field strength reached 400 kV / cm, W… tot =4.25J / cm 3 W rec =3.24J / cm 3 W loss =1.01J / cm 3 The corresponding η is 76.22%.

[0113] Comparative Example 3

[0114] Compared to the sodium niobate-based lead-free ceramic dielectric material structure of Example 4, this comparative example differs in that MnCO3 is replaced with MnSO4, while all other steps are the same as in Example 4. Because MnSO4 generates more oxygen vacancies upon thermal decomposition and volatilization, the ceramic performance deteriorates, and η remains stable at around 70% within an electric field strength range of 100–400 kV / cm. When the electric field strength reaches 400 kV / cm, W... tot =4.01J / cm 3 W rec =2.74J / cm 3 W loss =1.27J / cm 3 The corresponding η is 68.25%.

[0115] The sodium niobate-based lead-free ceramic dielectric material prepared in Comparative Example 3 was tested, and the results showed that η remained stable at around 75% within an electric field strength range of 100–400 kV / cm. When the electric field strength reached 400 kV / cm, W… tot =4.25J / cm 3 W rec =3.24J / cm 3 W loss=1.01J / cm 3 The corresponding η is 76.22%. Compared with Comparative Example 4, the addition of MnSO4 makes it difficult for S ions to volatilize during the ceramic preparation process, which leads to the generation of some pores and defects in the ceramic during sintering, resulting in a decrease in the energy storage performance of the ceramic.

[0116] Comparative Example 4

[0117] Compared with the sodium niobate-based lead-free ceramic media material structure of Example 1, this comparative example differs in that MnCO3 is not added, i.e., the step of adding MnCO3 in step (3) is omitted. The pre-synthesized ceramic powder is directly subjected to secondary ball milling, and the slurry after ball milling is dried at 100°C. During ball milling, anhydrous ethanol and ZrO2 balls are used as the ball milling media. The mass ratio of ZrO2 balls to raw materials is 2.5:1, the mass ratio of anhydrous ethanol to raw materials is 1.5:1, the speed of the ball mill is 430 r / min, and the ball milling time is 12 h.

[0118] The sodium niobate-based lead-free ceramic dielectric material prepared in Comparative Example 4 was tested, and the results showed that η remained stable at around 76% within an electric field strength range of 100–500 kV / cm. When the electric field strength reached 500 kV / cm, W… tot =5.21J / cm 3 W rec =3.99J / cm 3 W loss =1.22J / cm 3 The corresponding η is 76.50%.

[0119] Analysis of Examples 4, 1, 2, and 4 shows that without the addition of manganese carbonate or strontium bismuth titanate, or by using a solid-state reaction method, the total storage density W is [missing information]. tot Available energy storage density W rec There is a significant reduction in energy loss density W. loss The significant increase in energy density and the significant decrease in energy storage efficiency η indicate that the addition of strontium bismuth titanate and manganese carbonate in the formulation of this invention can significantly reduce leakage conductance, decrease residual polarization intensity, and increase breakdown electric field intensity while maintaining the high saturation polarization intensity of sodium niobate, thereby greatly improving the energy storage density of the sodium niobate-based lead-free ceramic dielectric. This ceramic dielectric material can be used as an energy storage material in laser, radar, mobile communication, or aerospace fields.

[0120] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a sodium niobate-based lead-free ceramic dielectric material, characterized in that, The chemical composition of this ceramic dielectric material is (1-x)(0.75NaNbO3-0.25Bi). 0.5 Na 0.5 TiO3)-xSr 0.7 Bi 0.2 TiO3 + 0.1-0.2 wt% MnCO3, where x = 0.02-0.10; The preparation method includes the following steps: S1: According to the general chemical formula of sodium niobate-based lead-free ceramic dielectric materials, bismuth source, sodium source, titanium source, strontium source and niobium source are mixed and then subjected to ball milling, discharge, drying and pre-firing in sequence to obtain pre-synthesized ceramic powder; The bismuth source includes Bi2O3, the sodium source includes Na2CO3, the titanium source includes TiO2, the strontium source includes SrCO3, and the niobium source includes Nb2O5; the pre-calcination temperature is 800-850℃, and the pre-calcination time is 4-8 h; S2: Add MnCO3 to the pre-synthesized ceramic powder obtained in S1 and ball mill it a second time. Then dry and sieve to obtain the raw material powder of sodium niobate-based lead-free ceramic media material. Add organic solvent, emulsifier, plasticizer, binder and dispersant to the raw material powder of sodium niobate-based lead-free ceramic media material and mix evenly to obtain a slurry of sodium niobate-based lead-free ceramic media material. Then obtain a ceramic film by casting. Perform isostatic pressing treatment on the ceramic film, remove the glue and sinter to obtain the sodium niobate-based lead-free ceramic media material.

2. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, The emulsifier is selected from trioleic acid glyceride, the plasticizer is selected from dibutyl phthalate, the binder is selected from polyvinyl butyral, and the dispersant is selected from polyethylene glycol.

3. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, The conditions for the primary and secondary ball milling processes are as follows: anhydrous ethanol and ZrO2 balls are used as the ball milling media, wherein the mass ratio of ZrO2 balls, anhydrous ethanol and raw materials is (2.2-2.6):(1.4-1.6):1, the ball milling speed is 420-460 r / min, and the ball milling time is 20-23h.

4. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, The amount of emulsifier added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic media material; the amount of plasticizer added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic media material; the amount of binder added is 10-12% of the mass of the raw material powder of sodium niobate-based lead-free ceramic media material; and the amount of dispersant added is 2.8-3.2% of the mass of the raw material powder of sodium niobate-based lead-free ceramic media material.

5. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, In step S2, the isostatic pressure treatment is performed by applying pressures of 50 MPa, 100 MPa, 150 MPa and 200 MPa sequentially at a temperature of 70-80℃.

6. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, In step S2, the sintering process specifically involves heating to 1200-1300℃ at a heating rate of 2.5-3.5℃ / min and calcining at a constant temperature for 2-4 hours.

7. The method for preparing sodium niobate-based lead-free ceramic dielectric material according to claim 1, characterized in that, In step S2, the temperature for discharging the adhesive is 550-600℃, and the discharging time is 20-24h.

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