High-energy-storage and high-efficiency dielectric ceramic and preparation method thereof

Abstract

The invention relates to the technical field of energy storage ceramics, in particular to a high-energy-storage and high-efficiency dielectric ceramic and a preparation method thereof. According to the specific technical scheme, the chemical general formula of the high-energy-storage and high-efficiency dielectric ceramic is (1-x) Bi < 0.2 > Na < 0.2 > K < 0.2 > La < 0.2 > Sr < 0.2 > TiO < 3-x > PbTiO < 3 >, and x is the content of introduced PbTiO < 3 > and ranges from 0.1 to 0.4. The polarization intensity of the high-entropy energy storage ceramic is regulated and controlled by regulating and controlling the content of the strong ferroelectric component.

Description

Technical Field

[0001] This invention relates to the field of energy storage ceramics technology, specifically to a high-energy-storage, high-efficiency dielectric ceramic and its preparation method. Background Technology

[0002] Ceramic capacitors for energy storage are widely used in advanced electronic devices such as microwave communications, electric vehicles, distributed energy systems, and energy storage systems due to their high power density and fast charge / discharge speed. Their energy storage mechanism relies on the displacement of bound charge cells, which is fundamentally different from the energy storage mechanisms of batteries and solid oxide fuel cells, which rely on chemical reactions. However, their relatively low recoverable energy density (W / W) is a significant challenge. rec Typically <5J / cm 3 The high energy density and high energy storage efficiency ("dual high") of lead-free dielectric capacitors have severely limited their application range and hindered their development towards miniaturization and intelligence. Therefore, the development of lead-free dielectric capacitors has become a research focus.

[0003] Energy storage density W rec It is a function of the polarization intensity of the energy storage ceramic under an applied electric field. Therefore, achieving high W rec It needs to simultaneously possess high saturation polarization, low remanent polarization, and high breakdown electric field. To achieve these electrical properties concurrently, dielectric materials should possess the following characteristics: dense microstructure, fine grains, enhanced electric field-induced polarization capability, and the ability to rapidly recover from a non-polar state. Currently, the most common method to enhance energy storage performance is through chemical composition design, and a large number of lead-free compounds have been extensively studied, with their energy storage density rapidly increasing to 7 J / cm³. 3 above.

[0004] Recent studies have found that in the superparaelectric state, certain energy storage ceramics exhibit further reductions in nanodomain size and weakening of interdomain coupling, resulting in lower barriers to domain flipping energy and lower thermal perturbation energy. Therefore, the polarization of nanodomains can rapidly and dynamically flip between energy-equivalent directions, making it possible to achieve extremely small hysteresis. While superparaelectric dielectric ceramics possess high energy storage efficiency, they significantly sacrifice the saturation polarization intensity P. m This results in ceramics having a lower energy storage density (see...) Figure 1 ).

[0005] Therefore, this invention designs a method for introducing strong ferroelectric components into superparaelectric energy storage ceramics in order to simultaneously obtain high energy storage density and energy storage efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-energy-storage, high-efficiency dielectric ceramic and its preparation method. By controlling the content of strong ferroelectric components, the polarization intensity of the high-entropy energy-storage ceramic can be regulated.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention discloses a high-energy-storage, high-efficiency dielectric ceramic, whose general chemical formula is:

[0009] (1-x)Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-xPbTiO3, where x is the content of introduced PbTiO3, x = 0.1-0.4.

[0010] This invention discloses a method for preparing high-energy-storage, high-efficiency dielectric ceramics. According to the stoichiometric ratio of the general chemical formula, raw materials K₂CO₃, Na₂CO₃, SrCO₃, Bi₂O₃, TiO₂, La₂O₃, and PbTiO₃ are weighed. Each raw material is mixed with anhydrous ethanol, then ball-milled once and calcined, followed by a second ball-milling. After drying, the powder is mixed with a binder and pressed into a green body. After removing the binder, it is calcined at high temperature to obtain the dielectric ceramic.

[0011] Preferably, the first ball milling is carried out at a speed of 300-400 rpm for 8-24 hours, with a ball-to-material ratio of 2:1-8:1; the second ball milling is carried out at a speed of 300-400 rpm for 8-24 hours, with a ball-to-material ratio of 2:1-8:1.

[0012] Preferably, the slurry obtained after one ball milling is dried at 70-90℃ for 8-24 hours and then calcined at 1000-1150℃ for 2 hours.

[0013] Preferably, the adhesive is a 2-5 wt% aqueous solution of polyvinyl alcohol.

[0014] Preferably, after the green body is debonded at 600°C for 1 hour, it is sintered in air at 1200-1260°C for 2-3 hours.

[0015] The present invention has the following beneficial effects:

[0016] 1. The high-entropy ferroelectric ceramic disclosed in this invention is produced by introducing the strong ferroelectric component PbTiO3 into Bi, which has a superparaelectric state. 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 In the TiO3 system, the problem of low polarization and poor energy storage density in superparaelectric high-entropy dielectric materials is addressed. The design mechanism of PbTiO3 component to enhance polarization is as follows: due to Pb... 2+The presence of empty orbitals that can hybridize with O enables high-entropy ceramics to exhibit enhanced lattice ferroelectric distortion at the atomic scale, thereby increasing polarization intensity. This structural change can significantly enhance field-induced polarization intensity in the original superparaelectric matrix, thus substantially increasing energy storage density while maintaining high energy storage efficiency.

[0017] 2. This invention utilizes superparaelectric Bi... 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 Introducing the highly ferroelectric PbTiO3 into the TiO3 system prepared high-entropy ceramics containing a large amount of the highly ferroelectric T phase. The large lattice distortion of the T phase creates conditions for the enhancement of the planning vector. At the same time, since Pb has empty orbitals that can hybridize with O, the polarization intensity of the ceramic at the atomic scale is also greatly improved, ultimately achieving excellent energy storage performance.

[0018] 3. The preparation method of the piezoelectric ceramic material described in this invention is simple, stable, easy to operate, and convenient for industrial production. Attached Figure Description

[0019] Figure 1 This is a schematic diagram showing the energy storage density and energy storage efficiency of energy storage ceramics.

[0020] Figure 2 This is a flowchart illustrating the preparation process of the energy storage medium ceramic of the present invention;

[0021] Figure 3 Bipolar PE curves of the high-entropy energy storage ceramic materials provided in Examples 7 and 8 under a field strength of 10 kV / mm;

[0022] Figure 4 The tolerance factor calculation results for the high-entropy energy storage ceramic materials provided in Examples 1-6;

[0023] Figure 5 X-ray diffraction patterns of the high-entropy energy storage ceramic materials provided in Examples 1-6;

[0024] Figure 6 The results of dielectric constant versus temperature for the high-entropy energy storage ceramic materials provided in Examples 1-6;

[0025] Figure 7 The transmission electron microscopy results are for Examples 1 and 4;

[0026] Figure 8 The results of PE tests on the high-entropy energy storage ceramic materials provided in Examples 1-5 at 10kV / mm;

[0027] Figure 9The results of PE tests on the high-entropy energy storage ceramic materials provided in Examples 1-5 under the breakdown field strength;

[0028] Figure 10 This is a comparison chart of the performance of Example 4 with other energy storage ceramics;

[0029] Figure 11 The results of PE tests on the energy storage ceramics of Examples 9, 10, and 11 under the breakdown field strength;

[0030] Figure 12 The results are from the energy storage performance stability test in Example 4. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0033] This invention discloses a high-energy-storage, high-efficiency dielectric ceramic, whose general chemical formula is:

[0034] (1-x)Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-xPbTiO3, where x is the content of introduced PbTiO3, x = 0.1-0.4.

[0035] refer to Figure 2 As shown, the preparation process is as follows:

[0036] (1) Ingredients: Weigh the raw materials K2CO3 (99.0%), Na2CO3 (99.8%), SrCO3 (99.0%), Bi2O3 (99.0%), TiO2 (98.0%), La2O3 (99.99%) and PbTiO3 (99.9%) according to the stoichiometric ratio of the general chemical formula.

[0037] (2) First ball milling: Put all raw materials, anhydrous ethanol, and zirconium oxide ball milling beads into a ball milling jar and mill at a speed of 300-400 rpm for 8-24 hours. The ball-to-material ratio is 2:1-8:1.

[0038] (3) Calcination: After the slurry obtained after one ball milling is dried at 70-90℃ for 8-24 hours, it is calcined at 1000-1150℃ for 2 hours to form the target crystal phase.

[0039] (4) Secondary ball milling: The calcined powder, anhydrous ethanol, and zirconium oxide ball milling beads are placed in a ball milling jar and milled at a speed of 300-400 rpm for 8-24 hours. The ball-to-material ratio is 2:1-8:1. After mixing evenly, the mixture is dried.

[0040] (5) Granulation: Dry the slurry after secondary ball milling, and then add 2-5wt% polyvinyl alcohol (PVA) aqueous solution as a binder.

[0041] (6) Molding: The granulated powder is pressed into a green disc with a diameter of 10.0 mm and a thickness of 1.0 mm under a pressure of 200 MPa for 30 seconds.

[0042] (7) Debinding and sintering: After debinding the green body at 600℃ for 1 hour, the disc is sintered in air at 1200-1260℃ for 2-3 hours to obtain a dense ceramic body.

[0043] (8) Performance testing: After polishing the ceramic body to a thickness of 0.03-0.10 mm, a gold electrode with a diameter of 2 mm is prepared on its surface for hysteresis loop testing.

[0044] The present invention will be further described below with reference to specific embodiments.

[0045] Example 1

[0046] If x is taken as 0 in the general formula, then the chemical formula of the high-entropy energy storage ceramic material in Example 1 is: Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3.

[0047] refer to Figure 1As shown, the method for preparing this ceramic is as follows: K2CO3 (99.0%), Na2CO3 (99.8%), SrCO3 (99.0%), Bi2O3 (99.0%), TiO2 (98.0%), La2O3 (99.99%), and PbTiO3 (99.9%) are used as raw materials. After being accurately weighed according to stoichiometric ratios, they are placed in a polyethylene container and mixed with zirconia balls and anhydrous ethanol. The mixture is then ball-milled for 8 hours (ball-to-material ratio of 4:1) to ensure thorough mixing. The resulting mixture is dried at 90℃ for 8 hours, calcined at 1000-1150℃ for 2 hours, and then ball-milled again for 8 hours (ball-to-material ratio of 4:1). The dried powder is then pressed into 10mm diameter discs under a pressure of 200MPa for 30 seconds, and finally sintered at 1260℃ in air for 2 hours to complete the preparation. Finally, after polishing the sample to a thickness of approximately 0.05 mm, a gold electrode with a diameter of 2 mm was fabricated on its surface for hysteresis loop testing.

[0048] Example 2

[0049] If x is taken as 0.1 in the general formula, then the chemical formula of the high-entropy energy storage ceramic material in Example 2 is: 0.9Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-0.1PbTiO3. The method for preparing this high-entropy energy storage ceramic in Example 2 of this invention is the same as that in Example 1. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formula in Example 2.

[0050] Example 3

[0051] In the general formula, x is taken as 0.2, then the chemical formula of the high-entropy energy storage ceramic material in Example 3 is: 0.8Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-0.2PbTiO3. The method for preparing this high-entropy energy storage ceramic in Example 3 of this invention is the same as that in Example 2. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formula in Example 3.

[0052] Example 4

[0053] In the general formula, x is taken as 0.25, then the chemical formula of the high-entropy energy storage ceramic material in Example 4 is: 0.75Bi 0.2 Na 0.2 K 0. 2La 0.2 Sr 0.2TiO3-0.25PbTiO3. The method for preparing this high-entropy energy storage ceramic in Example 4 of this invention is the same as that in Example 3. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formula in Example 4.

[0054] Example 5

[0055] If x is taken as 0.3 in the general formula, then the chemical formula of the high-entropy energy storage ceramic material in Example 5 is: 0.7Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-0.3PbTiO3. The method for preparing this high-entropy energy storage ceramic in Example 5 of this invention is the same as that in Example 4. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formula in Example 5.

[0056] Example 6

[0057] In the general formula, x is taken as 0.4, then the chemical formula of the high-entropy energy storage ceramic material in Example 5 is: 0.6Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-0.4PbTiO3. The method for preparing this high-entropy energy storage ceramic in Example 6 of this invention is the same as that in Example 5. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formula in Example 6.

[0058] Examples 7 and 8

[0059] To further demonstrate the superiority of PbTiO3 doping, a strong ferroelectric component, in enhancing polarization intensity, this experiment selected Bi... 0.2 Na 0.2 K 0.2 La 0.2 Pb 0.2 TiO3 is from Example 7 and Bi 0.2 Na 0.2 K 0.2 La 0.2 Ba 0.2 TiO3 is used in Example 8 to demonstrate the role of Pb. The methods used to prepare this high-entropy energy storage ceramic in Examples 7 and 8 are the same as those in Example 6. The difference lies in the molar ratio of the raw materials, which is determined by weighing according to the chemical formulas in Examples 7 and 8.

[0060] Examples 9-11

[0061] To further demonstrate the universality of PbTiO3 doping in enhancing polarization intensity, this experiment selected 0.75Bi... 0.2 Na 0.2 K 0.2 La 0.2 Ca 0.2 TiO3-0.25PbTiO3, 0.75Bi 0.2 Na 0.2 Li 0.2 La 0.2 Sr 0.2 TiO3-0.25PbTiO3 and 0.75Bi 0.2 Na 0.2 K 0.2 Nd 0.2 Sr 0.2 TiO3-0.25PbTiO3 is used in Examples 9-11. The method for preparing this high-entropy energy storage ceramic in Examples 9-11 is the same as that in Example 8. The difference is that the molar ratio of the raw materials is determined by weighing according to the chemical formulas in Examples 9-11.

[0062] Experimental characterization and performance test results:

[0063] like Figure 3 As shown, Figure 3 Bipolar PE curves of the high-entropy ceramics prepared in Examples 1, 7, and 8 under a 10 kV / mm electric field are shown. The results indicate that compared to Bi... 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3 high-entropy ceramics, Bi 0.2 Na 0.2 K 0.2 La 0.2 Pb 0.2 TiO3 and Bi 0.2 Na 0.2 K 0.2 La 0.2 Ba 0.2 The polarization intensity of high-entropy TiO3 ceramics was improved, demonstrating that doping with the strong ferroelectric components BaTiO3 and PbTiO3 is beneficial to improving polarization intensity. It is worth noting that Bi... 0.2 Na 0.2 K 0.2 La 0.2 Pb 0.2 The polarization intensity of TiO3 high-entropy ceramics is significantly higher than that of the other two high-entropy ceramics, because Pb 2+The presence of empty orbitals that can hybridize with O enables high-entropy ceramics to exhibit enhanced lattice ferroelectric distortion at the atomic scale, thereby leading to increased polarization intensity. These results demonstrate that PbTiO3 doping has a significant advantage in improving polarization intensity.

[0064] like Figure 4 As shown, Figure 4 Tolerance factors for different PbTiO3 doping contents were used to demonstrate that the strongly ferroelectric element PbTiO3 could be successfully introduced into Bi. 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 For TiO3 high-entropy ceramics, the tolerance factors of Examples 1-6 were calculated. The closer the tolerance factor is to 1, the higher the lattice matching degree and the easier the ceramic is to synthesize.

[0065] like Figure 5 As shown, Figure 5 XRD diffraction patterns of ceramics with different PbTiO3 doping contents were shown. The results indicate that no impurity peaks appeared in the XRD diffraction patterns of any of the ceramics, suggesting that all ceramics are pure phases and proving the successful preparation of this composition. Furthermore, the characteristic peak around 22° gradually increased in intensity with increasing PbTiO3 content, indicating a gradual enhancement of the ferroelectricity of the high-entropy ceramics. In addition, the pseudo-cubic phase was observed in the peak shape between 44° and 48° in all ceramics, indicating that the introduction of PT did not significantly disrupt the average superparaelectric state characteristics, which is beneficial for maintaining excellent energy storage efficiency.

[0066] like Figure 6 As shown, Figure 6The dielectric constants of (a) 0PT, (b) 10PT, (c) 20PT, (d) 25PT, (e) 30PT, and (f) 40PT vary with temperature; (g) the temperature values ​​corresponding to the dielectric peaks at 1 kHz for different PbTiO3 doping contents; and (h) the temperature differences of the dielectric peaks at different frequencies for 0PT and 25PT. The results show that the dielectric constant of the high-entropy ceramic continuously increases with increasing PbTiO3 content. A high dielectric constant is beneficial for the ceramic to obtain high polarization intensity under an electric field, indicating that the introduction of PbTiO3 is beneficial for enhancing energy storage performance. Simultaneously, the temperatures corresponding to the dielectric peaks at 1 kHz are extracted. It is found that the temperature consistently increases with PbTiO3 doping. Even with the introduction of 0-30% PbTiO3, the dielectric material still maintains its room-temperature superparaelectric characteristics, which is beneficial for excellent energy storage efficiency. However, when the PbTiO3 content further increases to 40%, the dielectric peak temperature exceeds room temperature, and the room-temperature superparaelectric structure is disrupted. This leads to high remanent polarization, which is detrimental to improving energy storage performance. Therefore, 40PT high-entropy ceramics will not be discussed further in the subsequent work. Furthermore, by extracting the temperature difference corresponding to the dielectric peaks at different frequencies for 0PT and 25PT high-entropy ceramics, it can be seen that PbTiO3 doping did not destroy the relaxation properties of the ceramics, indicating the successful introduction of the strategy.

[0067] like Figure 7 As shown, Figure 7 (a) and (e) show the transmission electron microscopy (TEM) results at 0 PT; (b), (c), and (f) show the TEM results at 25 PT; and (d) is a polarization diagram. The results show that a large nanodomain structure is observed in the 25 PT high-entropy ceramic sample, while no domain morphology is observed in the 0 PT high-entropy ceramic sample. This directly proves the effectiveness of the design strategy. Figure 1 This means that by introducing strongly ferroelectric components into superparaelectric dielectric materials, it is possible to modulate their nanoscale domain structure and promote enhanced polarization. Furthermore, atomic-scale transmission electron microscopy observations show that PbTiO3 doping increases the domain size from 2-4 nm at 0 PT to tens of nanometers at 25 PT, further confirming the enhancement effect of PbTiO3 on polarization at the atomic scale.

[0068] like Figure 8 As shown, hysteresis loop tests were performed on ceramics with different PbTiO3 contents to analyze their energy storage density and efficiency. It can be seen that under the same field strength, the polarization intensity gradually increases with the increase of PbTiO3 content, directly proving the effectiveness of the designed strategy.

[0069] Further calculations were performed to obtain the energy storage density and energy storage efficiency of each component material under the breakdown field strength, such as... Figure 9 (PE curves of different PbTiO3 doping contents under breakdown field strength) and Table 1 are shown.

[0070] Table 1 shows the energy storage performance of the high-entropy energy storage ceramic materials provided in Examples 1-5, based on their breakdown field strength.

[0071] system <![CDATA[Energy storage density (J / cm 3 )]]> Energy storage efficiency (%) <![CDATA[Saturation planned intensity (μC / cm 2 )]]> 0PT 10.8 96.7 27.7 10PT 13.8 89 49.5 20PT 14.8 81 60.8 25PT 20.5 86.5 65.8 30PT 19.3 87 62.2

[0072] like Figure 10 As shown, the energy storage performance of the components in the current invention was compared (data sourced from relevant articles published in authoritative international journals such as Nature Communications, Advanced Materials, and Science before October 2025, listed in Table 2). It is evident that compared to previous reports, this invention achieves an ultra-high energy storage density of ~20.5 J / cm³. 3 And energy storage efficiency ~86.5%. Furthermore, such as... Figure 11 As shown in the PE curves with different element substitutions, the (1-x)Bi in the formulation... 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 Replacing Sr with Ca, K with Li, or La with Nd in TiO3-xPbTiO3 (x=0.25) all result in an ultra-high energy storage density >15J / cm³. 3 The efficiency is >85%, proving that the method of the present invention has universality.

[0073] Table 2 Performance Comparison: Relevant Journal Articles and Performance

[0074]

[0075] like Figure 12 As shown, Figure 12 To assess the (a) frequency stability, (b) temperature stability, and (c) cycle stability of the sample prepared in Example 4, and to verify the performance stability of the ceramic of this invention, we conducted variable temperature, variable frequency, and fatigue performance tests on the ceramic. Experimental results show that the energy storage density is 11.3 ± 0.5 J / cm³ within the temperature range of 20-160℃. 3 The energy storage efficiency is 87.2±1.7%; the energy storage density is 11.4±0.9 J / cm³ in the 1-300 Hz range. 3 The energy storage efficiency is 82.5 ± 2.5%; at 10 cycles... 7 The energy storage density is 11.8 ± 0.1 J / cm³ within the specified range. 3 The energy storage efficiency is 84±0.5%. All of the above results demonstrate that the high-entropy ceramic of this invention possesses excellent performance stability.

[0076] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A high-energy-storage, high-efficiency dielectric ceramic, characterized in that: Its general chemical formula is: (1-x)Bi 0.2 Na 0.2 K 0.2 La 0.2 Sr 0.2 TiO3-xPbTiO3, where x is the content of introduced PbTiO3, x = 0.1-0.

4.

2. A method for preparing a high-energy-storage, high-efficiency dielectric ceramic as described in claim 1, characterized in that: According to the stoichiometric ratio of the general chemical formula, raw materials K2CO3, Na2CO3, SrCO3, Bi2O3, TiO2, La2O3 and PbTiO3 are weighed. Each raw material is mixed with anhydrous ethanol, and then ball-milled once and calcined, followed by a second ball milling. After drying, the powder is mixed with a binder and pressed into a green body. After removing the binder, it is calcined at high temperature to obtain dielectric ceramic.

3. The preparation method according to claim 2, characterized in that: The first ball milling is carried out at a speed of 300-400 rpm for 8-24 hours, with a ball-to-material ratio of 2:1-8:1; the second ball milling is carried out at a speed of 300-400 rpm for 8-24 hours, with a ball-to-material ratio of 2:1-8:

1.

4. The preparation method according to claim 2 or 3, characterized in that: After the slurry obtained from one ball milling is dried at 70-90℃ for 8-24 hours, it is calcined at 1000-1150℃ for 2 hours.

5. The preparation method according to claim 2, characterized in that: The adhesive is a 2-5 wt% aqueous solution of polyvinyl alcohol.

6. The preparation method according to claim 3, characterized in that: After the green body is debonded at 600℃ for 1 hour, it is sintered in air at 1200-1260℃ for 2-3 hours.

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