A high-entropy design bismuth ferrite-based energy storage ceramic, a preparation method and applications thereof

Abstract

The application relates to the technical field of dielectric energy storage device materials, in particular to a high-entropy design bismuth ferrite-based energy storage ceramic, a preparation method and application thereof, the material has a chemical composition formula of (0.7-x)Bi 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 )TiO3-xNaNbO3-yMnO2, wherein the value range of x is 0-0.15, and the value of y is 0-0.005. The application adopts a high-entropy strategy to design a relaxor ferroelectric material, multiple elements occupy the same site of the material to produce lattice distortion, promote the relaxor characteristics of the bismuth ferrite-based ceramic, and optimize the electric hysteresis loop. The NaNbO3 antiferroelectric material is introduced to destroy the long-range ferroelectric order and enhance the local random field, which is beneficial to obtaining a lower P r value. In addition, the appropriate addition of 0.5% mol of MnO2 can reduce the concentration of oxygen vacancies, thereby reducing the leakage current of the material, and the energy storage efficiency is improved. The material design not only enriches the application field of high-entropy ceramics, but also provides a new idea for improving the performance of energy storage ceramics.

Description

Technical Field

[0001] This invention relates to the field of dielectric energy storage device materials technology, specifically to a high-entropy bismuth ferrite-based energy storage ceramic, its preparation method, and its application. Background Technology

[0002] With the development of modern power electronics technology, higher demands are being placed on the energy storage density and power density of dielectric materials. Especially in high-power pulse power systems, aerospace, and new energy vehicles, the need for high-temperature stability and reliability of ceramic capacitors is growing. Traditional ceramic materials, due to their low Curie temperature and limited energy storage performance, are struggling to meet increasingly demanding application environments. Therefore, developing new ceramic materials with excellent high-temperature energy storage performance and stability is particularly important. High-entropy ceramics, as an emerging materials field, have attracted widespread attention in recent years. Their unique chemical composition and structural design offer new possibilities for achieving high energy storage density. Compared with other dielectric energy storage materials, bismuth ferrite-based ceramics, as a lead-free material, not only have environmental advantages but also offer rapid charge / discharge capabilities, high power density, and long cycle life, providing a promising alternative to lead-based ceramics.

[0003] Bismuth ferrite-based ceramics (BiFeO3) have a high Curie temperature (Ti). C High Curie temperatures are crucial for ensuring the reliability and stability of materials over a wide temperature range; bismuth ferrite-based ceramics exhibit large spontaneous polarization (approximately 100 μC / cm). 2 This characteristic helps to improve the energy storage density of materials. A large spontaneous polarization intensity means that the material can generate greater polarization under the influence of an electric field, thus storing more energy. However, it also has a large remanent polarization intensity, which leads to a relatively low breakdown field strength, limiting the improvement of efficiency. In August 2024, *ACS Applied Materials & Interfaces* published an article entitled "High-Entropy Strategy for Improved Mechanical and Energy Storage Properties in BaTiO3-BiFeO3 Based Ceramics," which developed a lead-free ferroelectric ceramic material based on 0.67BiFeO3-0.33BaTiO3, introducing Sr(Mg) through conventional solid-state sintering. 1 / 6 Zn 1 / 6 Ta 1 / 3Nb 1 / 3 O3 achieves multi-element coexistence at the B site and high configurational entropy, resulting in an excellent energy storage efficiency (η) of 75% and 2.4 J / cm³. 3 recoverable energy storage density (W)rec It also achieved an ultra-high hardness of up to 7.2 GPa, which proves that the high-entropy strategy of the invention is effective.

[0004] In summary, bismuth ferrite-based ceramics, as a potential lead-free system to replace lead-based ceramics, offer significant environmental and health advantages.

[0005] In view of the above difficulties, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention

[0006] The purpose of this invention is to address the challenges of high remanent polarization, dielectric loss, and low breakdown electric field in bismuth ferrite-based ceramics using a high-entropy strategy, thereby improving their overall energy storage performance. This invention provides a high-entropy design for bismuth ferrite-based energy storage ceramics, its preparation method, and its applications. This material design not only enriches the application fields of high-entropy ceramics but also offers new insights into improving the performance of energy storage ceramics.

[0007] To achieve the above objectives, this invention discloses a high-entropy bismuth ferrite-based energy storage ceramic, wherein the chemical composition of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic is (0.7-x)Bi. 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 TiO3-xNaNbO3-yMnO2, where 0≤x≤0.15, 0≤y≤0.005.

[0008] The x is 0, 0.05, 0.10 or 0.15, and the y is 0 or 0.005.

[0009] This invention also discloses a method for preparing the above-mentioned high-entropy bismuth ferrite-based energy storage ceramic, comprising the following steps:

[0010] S1, after drying Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3, they are mixed in a certain proportion to obtain mixture A;

[0011] S2, the mixture A obtained in step S1 is ball-milled for the first time with deionized water and zirconia balls. After ball milling, it is dried and then passed through a 120-mesh sieve to obtain mixture B.

[0012] S3, pre-calcining the mixture B obtained in step S2 at 880℃ for 3 hours, cooling it with the furnace after the temperature drops to 300℃, then ball milling it a second time, drying it, and then passing it through a 120-mesh sieve again to obtain high-entropy powder.

[0013] S4. The high-entropy powder obtained in step S3 is pressed into a cylindrical ceramic blank with a diameter of 10 mm and sintered in a muffle furnace at 970℃-990℃ to obtain a high-entropy bismuth ferrite-based energy storage ceramic.

[0014] In step S2, during the first ball milling, the planetary ball mill is used to ball mill clockwise for 12 hours, wait for 0.5 hours, and then continue ball milling counterclockwise for 12 hours at a speed of 200 r / min. After ball milling, the ball mill is dried for 48 hours at a drying temperature of 80℃.

[0015] In step S3, before the second ball milling, 0-0.5% mol of MnO2 is added to the pre-calcined powder to form a mixture.

[0016] In step S3, during the second ball milling, the planetary ball mill is used to ball mill clockwise for 12 hours, wait for 0.5 hours, and then continue ball milling counterclockwise for 12 hours at a speed of 200 r / min. After ball milling, the ball mill is dried for 48 hours at a drying temperature of 80℃.

[0017] In step S4, the sieved high-entropy powder is mixed with 7wt% PVA binder and granulated. After passing through a 120-mesh sieve again, a ceramic green body is obtained under a pressure of 158MPa for 2 minutes.

[0018] In step S4, the specific sintering process is as follows: the ceramic blank is buried in the same calcined powder, heated to 970-990℃ at a heating rate of 4-6℃ / min, sintered for 2-3 hours, and cooled with the furnace after the temperature drops to 300℃ to obtain a high-entropy bismuth ferrite-based energy storage ceramic.

[0019] This invention also discloses the application of the above-mentioned high-entropy bismuth ferrite-based energy storage ceramic in high-power dielectric energy storage devices.

[0020] This invention combines the high polarization characteristics of BiFeO3 and the excellent dielectric properties of BaTiO3. By controlling the proportion of various element doping through high-entropy design principles, it can promote the relaxation characteristics of bismuth ferrite-based ceramics, reduce polarization hysteresis, and achieve higher energy storage density and efficiency. The lattice distortion and increased resistivity caused by the high-entropy effect help enhance the breakdown electric field, further improving energy storage performance.

[0021] The main difficulty in this invention lies in solving the problem of Bi during the sintering process. 3+ The increase in leakage current due to volatilization and Fe 3+ The valence change of Bi leads to an increase in defect ion concentration, reducing the density and discharge energy and efficiency of the ceramic. This study employed a sealed sintering method, embedding the pressed green body in pre-fired powder, which reduced the concentration of Bi ions. 3+The volatilization of Fe; the introduction of NaNbO3 can act as a sintering aid, lowering the sintering temperature and promoting the densification process of ceramics. Doping with appropriate amounts of Sm and Gd elements can also stabilize Fe. 3+ The price change.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention utilizes the A-site (Bi) 3+ 、Sm 3+ Gd 3+ 、Sr 2+ Ba 2 + Na + ) and B position (Nb 5+ Ti 4+ Fe 3+ The coexistence of multiple elements increases the configurational entropy of ceramic materials, thereby inducing the relaxation behavior of BiFeO3-based ferroelectrics. The microcrystalline structure of high-entropy ceramics may tend to decrease due to the reduction in local electric field heterogeneity, which can be attributed to the slow diffusion effect induced by configurational entropy. On the one hand, the introduction of NN helps to achieve a near-hysteresis-free near-linear polarization response under high electric fields, which is crucial for improving energy storage efficiency. The increase in NN content leads to the random distribution of A-site and B-site ions, disrupting the long-range ferroelectric order and forming short-range PNR, thereby achieving a fast discharge response and low P. r In addition, the appropriate addition of 0.5% mol MnO2 can reduce the concentration of oxygen vacancies, thereby reducing the leakage current of the material and improving the energy storage efficiency. Attached Figure Description

[0023] Figure 1 The images show the sintered XRD patterns of different bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramics prepared in Examples 1-5.

[0024] Figure 2 SEM images of different bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramics prepared in Examples 1 to 5, wherein (a) Example 1, (b) Example 2, (c) Example 3, (d) Example 4, and (e) Example 5;

[0025] Figure 3 Images showing the hysteresis loops of different bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramics prepared in Examples 1-5;

[0026] Figure 4 Images showing the dielectric constant and dielectric loss at 1 MHz for different bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramics prepared in Examples 1-5.

[0027] Figure 5Images show the energy storage performance of the bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramic prepared in Example 5. (a) shows the monopole hysteresis loop of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5 under different electric fields. (b) shows the W... rec W tal and the variation of η with the electric field;

[0028] Figure 6 Images show the charge-discharge performance of the bismuth ferrite-based high-entropy relaxor ferroelectric energy storage ceramic prepared in Example 5. (a) shows the underdamped charge-discharge current curve of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5, and (b) shows the high-entropy bismuth ferrite-based ceramic sample I prepared in Example 5. max C D P D The curves showing the change with electric field are shown in (c) and (d) respectively. (c) is the overdamped charge-discharge current curve of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5. D Curve showing how it changes over time. Detailed Implementation

[0029] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0030] Example 1

[0031] This embodiment provides a high-entropy bismuth ferrite-based relaxor ferroelectric energy storage ceramic with a chemical composition of 0.7Bi. 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 TiO3.

[0032] The specific preparation steps for this ceramic are as follows:

[0033] Ingredients: Place the chemical raw materials Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3 (of which the purity of Bi2O3, Sm2O3, Gd2O3, TiO2, and Na2CO3 is not less than 99.99%, and the purity of SrCO3, BaCO3, Nb2O5, and Fe2O3 is not less than 99.9%) into a drying oven and dry at a constant temperature of 80℃ for 48 hours to remove the moisture present in the raw materials. Then, accurately weigh them on an electronic balance according to the formula ratio of each element.

[0034] First ball milling: Pour the zirconia balls, the weighed raw material mixture and deionized water into the nylon jar in sequence, then place the ball milling jar in the planetary ball mill, and ball mill clockwise for 12 hours. After stopping for 0.5 hours, ball mill counterclockwise for 12 hours at a speed of 200 r / min.

[0035] Drying: The mixture of the ball-milled raw material and deionized water was separated from the ball milling beads by a filter screen, and then the mixture was poured into a crystallizing dish and dried in a drying oven at a constant temperature of 80°C for 48 hours.

[0036] Sieving: After the mixture is completely dried and only the raw material powder remains, take the powder out of the crystallizing dish and grind it with an agate mortar until all the powder passes through a 120-mesh sieve to obtain powder with uniform particle size.

[0037] Pre-firing: The sieved sample is placed in an alumina crucible, with several small holes left in the powder to allow carbon dioxide released during pre-firing to escape. Then, it is pre-firing in a muffle furnace at 880℃ for 3 hours.

[0038] Secondary ball milling and sieving: Repeat the first ball milling, drying and sieving process to obtain powder with uniform particle distribution.

[0039] Tableting: The powder after the second sieving is granulated by adding 7wt% PVA binder. After granulation, it is sieved again through a 120-mesh sieve to obtain the final powder. An appropriate amount of powder is placed in a mold and pressed into a cylindrical green body with a diameter of 10mm using an automatic tablet press. The pressure is 158MPa and the holding time is 2min.

[0040] Debinding: All blanks are placed in a muffle furnace and heated to 600°C at a heating rate of 2°C / min. After holding at this temperature for 3 hours, the cooling rate is controlled at 5°C / min. After the temperature drops to 300°C, the blanks are cooled with the furnace until room temperature.

[0041] Sintering: The ceramic green body of this component after debinding is embedded in the same calcined powder and placed in a muffle furnace. The temperature is raised to 990°C at a heating rate of 5°C / min and sintered for 3 hours. The temperature is lowered to 300°C and then cooled to room temperature with the furnace to obtain the ceramic sample of this component.

[0042] Sample preparation: The ceramic sample is crushed, polished, ultrasonicated with alcohol, and coated with silver paste on both sides to obtain the sample to be tested.

[0043] In the above steps, silver paste is applied to both sides with radii of 1 mm and 2 mm respectively. The silvering temperature is 700℃ and the time is 40 minutes.

[0044] The XRD image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows a P4mm tetragonal phase structure.

[0045] The SEM image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows relatively dense grains with an average grain size of 1.85 μm.

[0046] The bismuth ferrite-based relaxor ferroelectric energy storage ceramic sample prepared in this embodiment can release energy density W. rec 1.96 J / cm 3 The energy storage efficiency η is 42.93%, the breakdown field strength is 230kV / cm, and the relative permittivity ε is... r The dielectric constant is 1471.2, and the dielectric loss tanδ is 0.085.

[0047] Example 2

[0048] This embodiment provides a high-entropy bismuth ferrite-based relaxor ferroelectric energy storage ceramic with a chemical composition of 0.65Bi. 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 TiO3-0.05NaNbO3.

[0049] The specific preparation steps for this ceramic are as follows:

[0050] Ingredients: Place the chemical raw materials Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3 (of which the purity of Bi2O3, Sm2O3, Gd2O3, TiO2, and Na2CO3 is not less than 99.99%, and the purity of SrCO3, BaCO3, Nb2O5, and Fe2O3 is not less than 99.9%) into a drying oven and dry at a constant temperature of 80℃ for 48 hours to remove the moisture present in the raw materials. Then, accurately weigh them on an electronic balance according to the formula ratio of each element.

[0051] First ball milling: Pour the zirconia balls, the weighed raw material mixture and deionized water into the nylon jar in sequence, then place the ball milling jar in the planetary ball mill, and ball mill clockwise for 12 hours. After stopping for 0.5 hours, ball mill counterclockwise for 12 hours at a speed of 200 r / min.

[0052] Drying: The mixture of the ball-milled raw material and deionized water was separated from the ball milling beads by a filter screen, and then the mixture was poured into a crystallizing dish and dried in a drying oven at a constant temperature of 80°C for 48 hours.

[0053] Sieving: After the mixture is completely dried and only the raw material powder remains, take the powder out of the crystallizing dish and grind it with an agate mortar until all the powder passes through a 120-mesh sieve to obtain powder with uniform particle size.

[0054] Pre-firing: The sieved sample is placed in an alumina crucible, with several small holes left in the powder to allow carbon dioxide released during pre-firing to escape. Then, it is pre-firing in a muffle furnace at 880℃ for 3 hours.

[0055] Secondary ball milling and sieving: Repeat the first ball milling, drying and sieving process to obtain powder with uniform particle distribution.

[0056] Tableting: The powder after the second sieving is granulated by adding 7wt% PVA binder. After granulation, it is sieved again through a 120-mesh sieve to obtain the final powder. An appropriate amount of powder is placed in a mold and pressed into a cylindrical green body with a diameter of 10mm using an automatic tablet press. The pressure is 158MPa and the holding time is 2min.

[0057] Debinding: All blanks are placed in a muffle furnace and heated to 600°C at a heating rate of 2°C / min. After holding at this temperature for 3 hours, the cooling rate is controlled at 5°C / min. After the temperature drops to 300°C, the blanks are cooled with the furnace until room temperature.

[0058] Sintering: The ceramic green body of this component after debinding is embedded in the same calcined powder and placed in a muffle furnace. The temperature is raised to 990°C at a heating rate of 5°C / min and sintered for 3 hours. The temperature is lowered to 300°C and then cooled to room temperature with the furnace to obtain the ceramic sample of this component.

[0059] Sample preparation: The ceramic sample is crushed, polished, ultrasonicated with alcohol, and coated with silver paste on both sides to obtain the sample to be tested.

[0060] In the above steps, silver paste is applied to both sides with radii of 1 mm and 2 mm respectively. The silvering temperature is 700℃ and the time is 40 minutes.

[0061] The XRD images of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment show that it exhibits a tetragonal P4mm phase and a pseudocubic phase. Structural coexistence.

[0062] The SEM image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows relatively dense grains with an average grain size of 0.54 μm.

[0063] The bismuth ferrite-based relaxor ferroelectric energy storage ceramic sample prepared in this embodiment can release energy density W. rec 2.33 J / cm 3The energy storage efficiency η is 45.46%, the breakdown field strength is 260kV / cm, and the relative permittivity ε is... r The dielectric constant is 1397.38, and the dielectric loss tanδ is 0.082.

[0064] Example 3

[0065] This embodiment provides a high-entropy bismuth ferrite-based relaxor ferroelectric energy storage ceramic with a chemical composition of 0.6Bi. 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 TiO3-0.1NaNbO3.

[0066] The specific preparation steps for this ceramic are as follows:

[0067] Ingredients: Chemical raw materials Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3 (of which Bi2O3, Sm2O3, Gd2O3, TiO2, and Na2CO3 have a purity of not less than 99.99%).

[0068] SrCO3, BaCO3, Nb2O5, and Fe2O3 (with a purity of not less than 99.9%) are placed in a drying oven and dried at a constant temperature of 80℃ for 48 hours to remove moisture from the raw materials. Then, they are accurately weighed on an electronic balance according to the formula ratio of each element.

[0069] First ball milling: Pour the zirconia balls, weighed raw materials and deionized water into the nylon jar in sequence, then place the ball milling jar in the planetary ball mill, and ball mill clockwise for 12 hours. After stopping for 0.5 hours, ball mill counterclockwise for 12 hours at a speed of 200 r / min.

[0070] Drying: The mixture of the ball-milled raw material and deionized water was separated from the ball milling beads by a filter screen, and then the mixture was poured into a crystallizing dish and dried in a drying oven at a constant temperature of 80°C for 48 hours.

[0071] Sieving: After the mixture is completely dried and only the raw material powder remains, take the powder out of the crystallizing dish and grind it with an agate mortar until all the powder passes through a 120-mesh sieve to obtain powder with uniform particle size.

[0072] Pre-firing: The sieved sample is placed in an alumina crucible, with several small holes left in the powder to allow carbon dioxide released during pre-firing to escape. Then, it is pre-firing in a muffle furnace at 880℃ for 3 hours.

[0073] Secondary ball milling and sieving: Repeat the first ball milling, drying and sieving process to obtain powder with uniform particle distribution.

[0074] Tableting: The powder after the second sieving is granulated by adding 7wt% PVA binder. After granulation, it is sieved again through a 120-mesh sieve to obtain the final powder. An appropriate amount of powder is placed in a mold and pressed into a cylindrical green body with a diameter of 10mm using an automatic tablet press. The pressure is 158MPa and the holding time is 2min.

[0075] Debinding: All blanks are placed in a muffle furnace and heated to 600°C at a heating rate of 2°C / min. After holding at this temperature for 3 hours, the cooling rate is controlled at 5°C / min. After the temperature drops to 300°C, the blanks are cooled with the furnace until room temperature.

[0076] Sintering: The ceramic green body of this component after debinding is embedded in the same calcined powder and placed in a muffle furnace. The temperature is raised to 985°C at a heating rate of 5°C / min and sintered for 3 hours. The temperature is lowered at a cooling rate of 5°C / min and then cooled to room temperature with the furnace to obtain the ceramic sample of this component.

[0077] Sample preparation: The ceramic sample is crushed, polished, ultrasonicated with alcohol, and coated with silver paste on both sides to obtain the sample to be tested.

[0078] In the above steps, silver paste is applied to both sides with radii of 1 mm and 2 mm respectively. The silvering temperature is 700℃ and the time is 40 minutes.

[0079] The XRD image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows that the tetragonal phase P4mm and the second phase (Sm,Gd)3NbO7 coexist.

[0080] The SEM image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows relatively dense grains with an average grain size of 0.51 μm.

[0081] The bismuth ferrite-based relaxor ferroelectric energy storage ceramic sample prepared in this embodiment can release energy density W. rec 3.5 J / cm 3 The energy storage efficiency η is 56.7%, the breakdown field strength is 330kV / cm, and the relative permittivity ε is... r The dielectric constant is 844.29, and the dielectric loss tanδ is 0.073.

[0082] Example 4

[0083] This embodiment provides a high-entropy bismuth ferrite-based relaxor ferroelectric energy storage ceramic with a chemical composition of 0.55Bi. 0.9 (Sm 0.5 Gd 0.5) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 TiO3-0.15NaNbO3.

[0084] The specific preparation steps for this ceramic are as follows:

[0085] Ingredients: Chemical raw materials Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3 (of which Bi2O3, Sm2O3, Gd2O3, TiO2, and Na2CO3 have a purity of not less than 99.99%).

[0086] SrCO3, BaCO3, Nb2O5, and Fe2O3 (with a purity of not less than 99.9%) are placed in a drying oven and dried at a constant temperature of 80℃ for 48 hours to remove moisture from the raw materials. Then, they are accurately weighed on an electronic balance according to the formula ratio of each element.

[0087] First ball milling: Pour the zirconia balls, weighed raw materials and deionized water into the nylon jar in sequence, then place the ball milling jar in the planetary ball mill, and ball mill clockwise for 12 hours. After stopping for 0.5 hours, ball mill counterclockwise for 12 hours at a speed of 200 r / min.

[0088] Drying: The mixture of the ball-milled raw material and deionized water was separated from the ball milling beads by a filter screen, and then the mixture was poured into a crystallizing dish and dried in a drying oven at a constant temperature of 80°C for 48 hours.

[0089] Sieving: After the mixture is completely dried and only the raw material powder remains, take the powder out of the crystallizing dish and grind it with an agate mortar until all the powder passes through a 120-mesh sieve to obtain powder with uniform particle size.

[0090] Pre-firing: The sieved sample is placed in an alumina crucible, with several small holes left in the powder to allow carbon dioxide released during pre-firing to escape. Then, it is pre-firing in a muffle furnace at 880℃ for 3 hours.

[0091] Secondary ball milling and sieving: Repeat the first ball milling, drying and sieving process to obtain powder with uniform particle distribution.

[0092] Tableting: The powder after the second sieving is granulated by adding 7wt% PVA binder. After granulation, it is sieved again through a 120-mesh sieve to obtain the final powder. An appropriate amount of powder is placed in a mold and pressed into a cylindrical green body with a diameter of 10mm using an automatic tablet press. The pressure is 158MPa and the holding time is 2min.

[0093] Debinding: All blanks are placed in a muffle furnace and heated to 600°C at a heating rate of 2°C / min. After holding at this temperature for 3 hours, the cooling rate is controlled at 5°C / min. After the temperature drops to 300°C, the blanks are cooled with the furnace until room temperature.

[0094] Sintering: The ceramic green body of this component after debinding is embedded in the same calcined powder and placed in a muffle furnace. The temperature is raised to 970°C at a heating rate of 5°C / min and sintered for 3 hours. The temperature is lowered at a cooling rate of 5°C / min and then cooled to room temperature with the furnace to obtain the ceramic sample of this component.

[0095] Sample preparation: The ceramic sample is crushed, polished, ultrasonicated with alcohol, and coated with silver paste on both sides to obtain the sample to be tested.

[0096] In the above steps, silver paste is applied to both sides with radii of 1 mm and 2 mm respectively. The silvering temperature is 700℃ and the time is 40 minutes.

[0097] The XRD image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows that it is a tetragonal P4mm phase. It coexists with the (Sm,Gd)3NbO7 three-phase system.

[0098] The SEM image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows relatively dense grains with an average grain size of 0.46 μm.

[0099] The bismuth ferrite-based relaxor ferroelectric energy storage ceramic sample prepared in this embodiment can release energy density W. rec 2.5 J / cm 3 The energy storage efficiency η is 79%, the breakdown field strength is 290kV / cm, and the relative permittivity ε is... r The dielectric constant is 652.89, and the dielectric loss tanδ is 0.084.

[0100] Example 5

[0101] This embodiment provides a high-entropy bismuth ferrite-based relaxor ferroelectric energy storage ceramic with a chemical composition of 0.6Bi. 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 )TiO3-0.1NaNbO3-0.5mol%MnO2.

[0102] The specific preparation steps for this ceramic are as follows:

[0103] Ingredients: Place the chemical raw materials Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, and Fe2O3 (of which the purity of Bi2O3, Sm2O3, Gd2O3, TiO2, and Na2CO3 is not less than 99.99%, and the purity of SrCO3, BaCO3, Nb2O5, and Fe2O3 is not less than 99.9%) into a drying oven and dry at a constant temperature of 80℃ for 48 hours to remove the moisture present in the raw materials. Then, accurately weigh them on an electronic balance according to the formula ratio of each element.

[0104] First ball milling: Pour the zirconia balls, weighed raw materials and deionized water into the nylon jar in sequence, then place the ball milling jar in the planetary ball mill, and ball mill clockwise for 12 hours. After stopping for 0.5 hours, ball mill counterclockwise for 12 hours at a speed of 200 r / min.

[0105] Drying: The mixture of the ball-milled raw material and deionized water was separated from the ball milling beads by a filter screen, and then the mixture was poured into a crystallizing dish and dried in a drying oven at a constant temperature of 80°C for 48 hours.

[0106] Sieving: After the mixture is completely dried and only the raw material powder remains, take the powder out of the crystallizing dish and grind it with an agate mortar until all the powder passes through a 120-mesh sieve to obtain powder with uniform particle size.

[0107] Pre-firing: The sieved sample is placed in an alumina crucible, with several small holes left in the powder to allow carbon dioxide released during pre-firing to escape. Pre-firing is then carried out in a muffle furnace at 880℃ for 3 hours.

[0108] Secondary ball milling and sieving: 0.5% mol of MnO2 is added to the pre-calcined powder, and the first ball milling, drying and sieving process is repeated to obtain powder with uniform particle distribution.

[0109] Tableting: The powder after the second sieving is granulated by adding 7wt% PVA binder. After granulation, it is sieved again through a 120-mesh sieve to obtain the final powder. An appropriate amount of powder is placed in a mold and pressed into a cylindrical green body with a diameter of 10mm using an automatic tablet press. The pressure is 158MPa and the holding time is 2min.

[0110] Debinding: All blanks are placed in a muffle furnace and heated to 600°C at a heating rate of 2°C / min. After holding at this temperature for 3 hours, the cooling rate is controlled at 5°C / min. After the temperature drops to 300°C, the blanks are cooled with the furnace until room temperature.

[0111] Sintering: The ceramic green body of this component after debinding is embedded in the same calcined powder and placed in a muffle furnace. The temperature is raised to 980°C at a heating rate of 5°C / min and sintered for 3 hours. The temperature is lowered at a cooling rate of 5°C / min and then cooled to room temperature with the furnace to obtain the ceramic sample of this component.

[0112] Sample preparation: The ceramic sample is crushed, polished, ultrasonicated with alcohol, and coated with silver paste on both sides to obtain the sample to be tested.

[0113] In the sample preparation process, silver paste was applied to both sides with radii of 1 mm and 2 mm, respectively. The silver firing temperature was 700℃, and the firing time was 40 minutes.

[0114] The XRD images of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment show tetragonal P4mm phase and pseudocubic phase. coexist.

[0115] The SEM image of the bismuth ferrite-based relaxor ferroelectric energy storage ceramic material prepared in this embodiment shows dense grains with an average grain size of 0.49 μm.

[0116] The bismuth ferrite-based relaxor ferroelectric energy storage ceramic sample prepared in this embodiment can release energy density W. rec 3.7 J / cm 3 The energy storage efficiency η is 70.5%, the breakdown field strength is 330 kV / cm, and the relative permittivity ε is... r The dielectric constant is 840.1, the dielectric loss tanδ is 0.06, and the discharge time is 33ns.

[0117] The bismuth ferrite-based ceramic samples in Examples 1-5 were subjected to XRD, SEM, dielectric temperature spectroscopy, hysteresis loop, and charge-discharge tests. The results are analyzed below:

[0118] Figure 1 XRD images of the high-entropy bismuth ferrite-based ceramic samples prepared in Examples 1-5: The phase structure of the undoped NaNbO3 ceramic sample is P4mm; the main structure of the ceramic samples with x = 0.05, 0.10, and 0.15 is P4mm, partially transformed into... The ceramic samples with composition x = 0.10 and 0.15 also contained a portion of (Sm,Gd)3NbO7 impurity phase. When 0.5% mol of MnO2 was added to the ceramic sample with composition x = 0.1, no obvious (Sm,Gd)3NbO7 impurity phase appeared. The addition of MnO2 may help suppress the formation of impurity phases in the material, thereby maintaining the phase purity and crystal structure integrity of the material.

[0119] Figure 2The images show SEM images of the high-entropy bismuth ferrite-based ceramic samples prepared in Examples 1-5. Specifically, (a) is an SEM image of the high-entropy bismuth ferrite-based ceramic prepared in Example 1, with an average grain size of 1.85 μm. (b) is an SEM image of the high-entropy bismuth ferrite-based ceramic prepared in Example 2, with an average grain size of 0.64 μm. (c) is an SEM image of the high-entropy bismuth ferrite-based ceramic prepared in Example 3, with an average grain size of 0.51 μm. (d) is an SEM image of the high-entropy bismuth ferrite-based ceramic prepared in Example 4, with an average grain size of 0.46 μm. (e) is an SEM image of the high-entropy bismuth ferrite-based ceramic prepared in Example 5, with an average grain size of 0.49 μm. Figures (a)-(d) show that the gradually decreasing average grain size helps to improve the breakdown electric field of the ceramic. Figure (e) shows that the average grain size of the sample with added MnO2 also decreases.

[0120] Figure 3 Images show the dielectric constant and dielectric loss of the high-entropy bismuth ferrite-based ceramic samples prepared in Examples 1-5 at 1 MHz. The maximum dielectric constant is 1397.38 for ceramics with x = 0, gradually decreasing to 840.1 for ceramics with composition x = 0.15. This indicates that the dielectric constant gradually flattens after the addition of NaNbO3, suggesting the influence of relaxation behavior. In Examples 1-5, the dielectric loss is low at low temperatures, gradually increasing with increasing temperature. Increased temperature leads to increased charge carrier mobility, which in turn increases the material's conductivity and consequently, the dielectric loss.

[0121] Figure 4 The images show the hysteresis loops of the high-entropy bismuth ferrite-based ceramic samples prepared in Examples 1-5. As the NaNbO3 doping content gradually increases (x≤0.1), the PE curves show the P... r Gradually decrease, P m and E b The doping concentration gradually increases. In Example 4, the NaNbO3 doping concentration was 0.15, and the P... r E b The further reduction may be related to the lattice distortion induced by NaNbO3, the increase in random electric field, and the decrease in breakdown field strength due to the influence of the second phase. This is also true for P in Example 4. r The value reached its lowest point, approximately 3 μC / cm. 2 By calculating the energy density and energy consumption, it was found that in Example 4, an ESP (W) with a breakdown strength of 290 kV / cm was obtained when x = 0.15. rec ~2.5J / cm 3 In Example 5, with x = 0.1, a high breakdown strength of 330 kV / cm was obtained for the ESP (W) with a breakdown strength of η ~ 79%. rec~3.7J / cm 3 Performance (η ~ 70.4%).

[0122] Figure 5 (a) Images of the monopole hysteresis loops of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5 under different electric fields. The maximum polarization and energy storage density increase with increasing electric field. Figure 5 (b) is W in Example 5 rec W tal As η changes with the electric field, energy storage efficiency and energy storage density show opposite trends. Under high electric fields, domains may respond more readily and switch quickly, which helps to improve discharge rate and energy storage density. However, this rapid response may also lead to increased energy loss, thereby reducing energy storage efficiency.

[0123] Figure 6 (a) is the underdamped charge-discharge current curve of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5. Figure 6 (b) is the high-entropy bismuth ferrite-based ceramic sample I prepared in Example 5. max C D P D Curve of change with electric field Figure 6 (c) is the overdamped charge-discharge current curve of the high-entropy bismuth ferrite-based ceramic sample prepared in Example 5. Figure 6 (d) is the high-entropy bismuth ferrite-based ceramic sample W prepared in Example 5. D Curve showing the change over time. The results indicate that C... D and P D Both increase with increasing electric field, reaching 679.3 A / cm at 160 kV / cm. 2 and 54.34MW / cm 3 The maximum value. Discharge time t 0.9 =33ns, which indicates the discharge energy density (W d 90% of the energy can be released rapidly, and this high-entropy energy storage ceramic material shows great potential and advantages in the field of lead-free ceramics.

[0124] The ceramic sample in Example 3, with a composition of 0.1%, exhibited a high breakdown electric field and energy density, but its energy conversion efficiency was low under a high breakdown electric field. Unlike Example 3, the ceramic sample prepared in Example 5 involved an improvement in the process: before the second ball milling, 0.5% mol of MnO2 was added to the pre-calcined powder, and the first ball milling, drying, and sieving process was repeated to obtain a powder with uniform particle distribution.

[0125] The ceramic sample prepared in Example 5, with a sintering temperature reduced to 980℃, contained tetragonal P4mm phase and pseudocubic phase. Coexistence without other impurities. The grain distribution is more compact, with an average grain size of 0.49 μm. The prepared ceramic sample can release a storage density W. rec 3.7 J / cm 3 The energy storage efficiency η is 70.5%, the breakdown field strength is 330 kV / cm, and the relative permittivity ε is... r The dielectric constant is 840.1, the dielectric loss tanδ is 0.06, and the discharge time is 33 ns. Additionally, MnO2 can reduce Fe... 2+ / Fe 3+ Ion exchange between components helps reduce leakage current in the material, thereby reducing energy loss. In Example 5, through process improvement, the energy storage characteristics of a ceramic sample with a composition of 0.1 were successfully optimized.

[0126] In summary, Example 5 represents the best overall performance. Under the high-entropy strategy, it is known that when the N / A doping amount is 0.1 and an additional 0.5% mol of MnO2 is added, the relaxation behavior of bismuth ferrite-based ceramics can be improved, grain growth can be suppressed, the breakdown field strength can be enhanced, and the remanent polarization intensity can be reduced, thereby achieving a higher storage density of 3.7 J / cm³. 3 The rapid discharge rate is 33 ns.

[0127] This invention revolves around (0.7-x)Bi 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 This paper details the preparation method, performance testing, and potential applications of TiO3-xNaNbO3-yMnO2 (where 0≤x≤0.15 and y is 0 or 0.005), providing a reference for further research and industrialization of high-entropy ceramic materials.

[0128] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A high-entropy design bismuth ferrite-based energy storage ceramic, characterized in that, The chemical composition of the bismuth ferrite-based energy storage ceramic is (0.7-x)Bi 0.9 (Sm 0.5 Gd 0.5 ) 0.1 FeO3-0.3(Sr 0.5 Ba 0.5 )TiO3-xNaNbO3-y MnO2, wherein 0 < x ≤ 0.15, 0 < y ≤ 0.

005.

2. A high-entropy design bismuth ferrite-based energy storage ceramic according to claim 1, wherein, The x is 0.05, 0.10 or 0.15, and y is 0.

005.

3. A method of preparing a high-entropy design bismuth ferrite-based energy storage ceramic as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: S1, after drying Bi2O3, Sm2O3, Gd2O3, SrCO3, BaCO3, TiO2, Na2CO3, Nb2O5, Fe2O3, the mixture A is obtained by mixing according to the proportion; S2, the mixture A obtained in step S1 is mixed with deionized water and zirconia balls, and the first ball milling is carried out, and then the drying treatment is carried out after the ball milling, and the mixture B is obtained after the complete drying and the screening through the 120 mesh screen; S3, the mixture B obtained in step S2 is pre-fired at 880℃ for 3h, and then the temperature is reduced to 300℃, and the furnace cooling is carried out, and then the second ball milling is carried out, and then the drying treatment is carried out, and then the high-entropy powder is obtained after the screening through the 120 mesh screen again, and before the second ball milling, the MnO2 is added to the pre-fired powder to form the mixture; S4, the high-entropy powder obtained in step S3 is pressed into a cylindrical ceramic green body with a diameter of 10 mm, and then the sintering is carried out at 970-990℃ in a muffle furnace for 3h, and then the high-entropy designed bismuth ferrite-based energy storage ceramic is obtained.

4. A method of preparing a high-entropy design bismuth ferrite-based energy storage ceramic according to claim 3, characterized in that, In the step S2, when the first ball milling is carried out, the planetary ball mill is clockwise ball milled for 12h, and then the waiting is carried out for 0.5h, and then the counterclockwise ball milling is continued for 12h, and the rotating speed is 200r / min, and then the drying treatment is carried out for 48h after the ball milling is completed, and the drying temperature is 80℃.

5. A method of preparing a high-entropy design bismuth ferrite-based energy storage ceramic according to claim 3, characterized in that, In the step S3, when the second ball milling is carried out, the planetary ball mill is clockwise ball milled for 12h, and then the waiting is carried out for 0.5h, and then the counterclockwise ball milling is continued for 12h, and the rotating speed is 200r / min, and then the drying treatment is carried out for 48h after the ball milling is completed, and the drying temperature is 80℃.

6. A method of preparing a high-entropy design bismuth ferrite-based energy storage ceramic according to claim 3, characterized in that, In the step S4, after the screening, the high-entropy powder is mixed with 7wt% of PVA binder for granulation, and then the screening through the 120 mesh screen is carried out again, and then the ceramic green body is obtained under the pressure of 158MPa, and the pressure maintaining time is 2min.

7. A method of preparing a high-entropy design bismuth ferrite-based energy storage ceramic according to claim 3, characterized in that, In the step S4, the specific process of the sintering is as follows: the ceramic green body is buried in the calcined same powder, and then the temperature is increased to 970-990℃ at the temperature increasing rate of 4-6℃ / min, and then the sintering time is 2-3h, and then the temperature is reduced to 300℃, and then the furnace cooling is carried out, and then the high-entropy designed bismuth ferrite-based energy storage ceramic is obtained.

8. The application of the high-entropy designed bismuth ferrite-based energy storage ceramic in the high-power dielectric energy storage device according to claim 1 or 2.

Images