BNT-based ceramic material with high energy storage performance as well as preparation method and application of BNT-based ceramic material

Abstract

A BNT-based ceramic material with high energy storage performance belongs to the technical field of functional ceramics, the chemical general formula of the BNT-based ceramic material is lambda (Bi0. 5Na0. 5) 1-xCaxHfyTi1-yO3-(1-lambda) Sr0. 7Bi0. 2TiO3, x is greater than 0 and less than or equal to 0.09, and y is greater than 0 and less than or equal to 0.09. The preparation method comprises the following steps: weighing Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3 according to a chemical formula lambda (Bi0. 5Na0. 5) (1-x) CaxHfyTi (1-y) O3-(1-lambda) Sr0. 7Bi0. 2TiO3; carrying out ball milling on the raw materials to obtain dry powder; pre-sintering the powder subjected to ball milling, and carrying out secondary ball milling on the pre-sintered powder; adding polyvinyl alcohol into the powder subjected to secondary ball milling, granulating, and pressing the granules into ceramic chips; carrying out glue discharging treatment on the ceramic wafer; and sintering the ceramic chip after glue discharging to obtain a ceramic material sample. According to the invention, Ca < 2 + > / Hf < 4 + > co-doping stabilizes the TiO6 octahedral structure, refines the grain size and promotes the formation of nano-domains. Besides, the BNCxHyT-SBT ceramic can realize nearly equal proportion balance coexistence of P4bm and R3c phases, and the polarization dynamics and relaxation behavior are remarkably enhanced, so that the energy storage performance is maximized.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramics, and particularly relates to a BNT-based high energy storage performance ceramic material, its preparation method and application. Background Art

[0002] With the rapid development of electronic information technology and the continuous enhancement of people's environmental protection awareness, environmentally friendly energy storage materials and devices have become one of the research hotspots in the field of functional materials. Among many energy storage technologies, dielectric ceramic capacitors are considered a promising energy storage material due to their ultra-high power density, fast charge and discharge rate, good temperature stability and anti-fatigue performance.

[0003] Among traditional dielectric ceramic materials, lead-containing dielectric materials have a greater energy storage density. However, the volatilization of lead will cause serious damage to the human body and the environment, and the use of this material will be restricted with the improvement of environmental protection awareness. Therefore, it is an inevitable trend for countries to develop new environmentally friendly lead-free ceramics to meet the application requirements in the future energy storage field.

[0004] Lead-free perovskite ceramics have become promising candidate materials for energy storage applications due to their excellent dielectric properties and environmental compatibility. Among them, ceramics based on Bi 0.5 Na 0.5 TiO3 (BNT) stand out due to their large spontaneous polarization (P S ) and high Curie temperature (T C ). However, the practical application of BNT is limited by challenges such as high dielectric loss and low breakdown electric field strength, which restrict its energy storage capacity. Summary of the Invention

[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a BNT-based high energy storage performance ceramic material, its preparation method and application, so as to solve the technical problem of poor energy storage performance of lead-free energy storage ceramic materials in the prior art.

[0006] To achieve the above purpose and other related purposes,

[0007] In the first aspect of the present invention, a BNT-based high energy storage performance ceramic material is provided, and its chemical general formula is:

[0008] λ(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-(1-λ)Sr 0.7 Bi 0.2 TiO3,

[0009] Among them, 0 < x ≤ 0.09 and 0 < y ≤ 0.09.

[0010] Preferably in any of the above solutions, the chemical general formula of the BNT-based high energy storage performance ceramic material is: λ(Bi 0.5 Na 0.5 ) 0.03 Ca 0.07 Hf 0.07 Ti 0.03 O3-(1-λ)Sr 0.7 Bi 0.2 TiO3.

[0011] Preferably in any of the above solutions, the chemical general formula of the BNT-based high energy storage performance ceramic material is: Its chemical general formula is: 0.65(Bi 0.5 Na 0.5 ) 0.03 Ca 0.07 Hf 0.07 Ti 0.03 O3-0.35Sr 0.7 Bi 0.2 TiO3.

[0012] The second invention of the present invention provides a preparation method of a BNT-based high energy storage performance ceramic material, including the following steps:

[0013] S1. According to the chemical formula λ(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-(1-λ)Sr 0.7 Bi 0.2 TiO3, weigh raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3;

[0014] S2. Ball mill the raw materials to obtain dry powder;

[0015] S3. Pre-burn the ball milled powder and perform secondary ball milling on the pre-burned powder;

[0016] S4. Add 5wt% polyvinyl alcohol to the powder after secondary ball milling for granulation, and press the granules into ceramic sheets;

[0017] S5. Perform debinding treatment on the ceramic sheets;

[0018] S6. Sinter the ceramic sheets after debinding to obtain ceramic material samples.

[0019] Preferably, in any of the above solutions, in S2, the ball milling time of the raw materials is 10 to 14 h, and the ball milling media are zirconia balls and absolute ethanol.

[0020] Preferably, in any of the above solutions, in S3, the pre-sintering temperature of the ball-milled powder is 800 to 900 °C, the pre-sintering time is 5 to 6 h, and the time of secondary ball milling is 10 to 14 h.

[0021] Preferably, in any of the above solutions, in S5, the process of debinding treatment is to heat the ceramic sheet at a rate of 1 to 2 °C / min to 800 to 900 °C and hold for 1 to 3 h.

[0022] Preferably, in any of the above solutions, in S6, the sintering temperature of the ceramic sheet is 1140 to 1150 °C, and the sintering time is 2 to 4 h.

[0023] In the third aspect of the present invention, a ceramic energy storage capacitor is provided, and the ceramic energy storage capacitor includes a BNT-based high energy storage performance ceramic material.

[0024] As described above, a BNT-based high energy storage performance ceramic material, its preparation method and application of the present invention have the following beneficial effects:

[0025] 1. In the present invention, double-site doping is carried out in BNT, Ca is introduced at the A site 2+ which inhibits grain growth and refines the grain size, thereby improving the breakdown strength; at the same time, Ti at the B site 4+ is replaced by Hf 4+ which destroys the ferroelectric long-range order, forms nano-scale domain regions, reduces the inter-domain coupling, enhances the response speed of the nano-scale domain structure to the electric field, and reduces the remanent polarization, enabling the BNCxHyT-SBT ceramic to maintain excellent energy storage performance in a wide temperature range of 30 to 150 °C.

[0026] 2. In the present invention, after introducing SBT, the perovskite structure of BNT changes from a trigonal phase to a coexistence phase of trigonal and tetragonal; on this basis, Ca 2+ / Hf 4+ is co-doped at the A / B sites. By changing the content of Ca 2+ / Hf 4+ the ceramic microstructure is regulated, enabling the BNCxHyT-SBT ceramic to achieve a nearly equal proportion balance coexistence of the P4bm and R3c phases, significantly enhancing the polarization dynamics and relaxation behavior, and thus maximizing the energy storage performance of the ceramic material.

[0027] 3. In the present invention, Ca 2+ / Hf 4+Substitutions were made at different sites in the ABO3-type perovskite structure, effectively changing the local structure of the unit cell, reducing the differences in the bond lengths of Bi-O and Ti-O in the oxygen octahedra and enhancing the symmetry in the P4bm and R3c phases, thus achieving lattice structure stability and the best structural balance. Description of the Drawings

[0028] Figure 1 Shown are the XRD pattern of the BNCxHyT-SBT ceramic and the enlarged cross-sections of the (111) and (200) peaks.

[0029] Figure 2 Shown is the unipolar P-E diagram of the BNCxHyT-SBT ceramic at 2 Hz and ambient temperature.

[0030] Figure 3 Shown is the energy storage performance diagram of the BNCxHyT-SBT ceramic at 250 kV / cm.

[0031] Figure 4 Shown is the summary diagram of the P value parameters of the BNCxHyT-SBT ceramic.

[0032] Figure 5 Shown is the content diagram of the tetragonal (P4bm) phase and the trigonal (R3c) phase in the BNCxHyT-SBT ceramic.

[0033] Figure 6 Shown is the SEM diagram of the BNCxHyT-SBT ceramic, where (a) x = y = 0, (b) x = y = 0.03, (c) x = y = 0.05, (d) x = y = 0.07, (e) x = y = 0.09, (f) summary diagram of the average grain size of ceramics with different compositions;

[0034] Figure 7 Shown is BNC 0.07 H 0.07 Comparison diagram of the energy storage performance of the T-SBT ceramic with existing lead-free ceramics.

[0035] Figure 8 Shown is BNC 0.07 H 0.07 Electric hysteresis loop (a) of the BNCxHyT-SBT ceramic under an electric field of 50 - 250 kV / cm and its corresponding energy storage parameters (b) diagram.

[0036] Figure 9 Shown is BNC 0.07 H 0.07 Diagram of the change of the electric hysteresis loop of the BNCxHyT-SBT ceramic with polarization with the number of cycles (c) and the corresponding energy storage parameters (d).

[0037] Figure 10 Shown is BNC0.07 H 0.07 Electric hysteresis loops (e) and corresponding energy storage parameters (f) of T-SBT ceramics under an electric field of 120 kV / cm and at different temperatures. Detailed implementation manners

[0038] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0039] The technical solution of the present invention is not limited to the specific implementation manners listed below, and also includes any combination between the specific implementation manners.

[0040] The present invention first provides a BNT-based high energy storage performance ceramic material, and its chemical general formula is:

[0041] λ(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-(1-λ)Sr 0.7 Bi 0.2 TiO3,

[0042] where 0 < x ≤ 0.09 and 0 < y ≤ 0.09.

[0043] The present invention uses a BNT ferroelectric ceramic material as the matrix, and at the same time introduces the relaxor material Sr 0.7 Bi 0.2 TiO3 into BNT to adjust the relaxivity of the material, so that Bi 0.5 Na 0.5 TiO3-Sr 0.7 Bi 0.2 TiO3 (BNT-SBT) ceramics have lead-free environmental protection and good relaxor behavior. After introducing SBT, the perovskite structure of BNT changes from a rhombohedral phase to a coexisting phase of rhombohedral and tetragonal phases, and the structure of the coexistence of different crystal phases plays a key role in the energy storage performance.

[0044] At the same time, the reasonable introduction of doping ions Ca 2+ , Hf 4+ can effectively adjust the local coordination environment of A-site and B-site ions, induce the formation of oxygen vacancies, and cause local lattice distortion. These modifications can enhance the polarization characteristics and dielectric response of the material, and effectively overcome the limitations of single-component doping modification. Introducing Ca 2+ at the A-site of the BNT-based ceramic inhibits grain growth and refines the grain size, thereby improving the breakdown strength. At the same time, Ti 4+ at the B-site is replaced by Hf 4+Substitution disrupts the long-range order, forming domain structures at the nanoscale, reducing inter-domain coupling, enhancing the responsiveness of nanodomains to the electric field, and decreasing the remnant polarization.

[0045] In summary, BNC x H y The H-T-SBT ceramics achieve a nearly equal-proportion balanced coexistence of the P4bm and R3c phases, significantly enhancing the polarization dynamics and relaxation behavior, thus maximizing the energy storage performance, and can exhibit excellent energy storage performance within the high-temperature test range of 30 - 150 °C.

[0046] Based on the above theoretical basis, in this embodiment, 0.65(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-0.35Sr 0.7 Bi 0.2 TiO3 (abbreviated as BNC x H y T-SBT) is selected as the research object.

[0047] The present invention provides a preparation method for a BNT-based ceramic material with high energy storage performance, comprising the following steps:

[0048] S1. According to the chemical formula 0.65(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-0.35Sr 0.7 Bi 0.2 TiO3, weigh raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3. Among them, the purities of Bi2O3, SrCO3, and TiO2 are 99%, the purity of CaCO3 is 98.5%, the purity of HfO2 is 99.9%, and the purity of Na2CO3 is 99.8%.

[0049] S2. Ball-mill the raw materials at a rotation speed of 250 r / min for 10 - 14 h to obtain dry powder. During the ball-milling process, zirconia balls are placed in the ball-milling tank, and anhydrous ethanol is used as the ball-milling medium;

[0050] S3. Pre-sinter the ball-milled powder at 800 - 900 °C for 5 - 6 h, and perform secondary ball-milling on the pre-sintered powder. The rotation speed of the secondary ball-milling is 250 r / min, and the time of the secondary ball-milling is 10 - 14 h;

[0051] S4. To achieve better shaping, 5 wt% polyvinyl alcohol (PVA) was added to the powder after secondary ball milling for granulation, and the granules were pressed into ceramic wafers with a diameter of 10 mm and a thickness of about 1 mm;

[0052] S5. The ceramic wafers were slowly heated to 800 - 900 °C at a rate of 1 - 2 °C / min and then held for 1 - 3 h for binder burnout treatment to remove the binder;

[0053] S6. The ceramic wafers after binder burnout were sintered at 1140 - 1150 °C for 2 - 4 h to obtain ceramic material samples.

[0054] After sintering, the ceramics were ultrasonically cleaned and polished on both sides, and then silver electrodes were coated for electrical property testing.

[0055] During the process of testing the energy storage performance, a very high electric field needs to be applied (electric field strength = voltage / thickness). If the sample thickness is large, the required voltage will be very high, which not only places high requirements on the instrument but also easily causes sample breakdown. Therefore, in order to reduce the external voltage and simultaneously reduce the risk of sample breakdown, in this embodiment, a grinding machine was used to reduce the ceramic thickness to less than 0.2 mm before testing the energy storage performance.

[0056] Example 1

[0057] The chemical formula of the BNT-based high energy storage performance ceramic material in this example is:

[0058] 0.65(Bi 0.5 Na 0.5 ) 0.07 Ca 0.03 Hf 0.03 Ti 0.07 O3-0.35Sr 0.7 Bi 0.2 TiO3, and the preparation process includes the following steps:

[0059] S1. Weigh the raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3 according to the stoichiometric ratio;

[0060] S2. The raw materials were ball milled for 12 h at 250 r / min with anhydrous ethanol as the medium to obtain dry powder;

[0061] S3. The ball milled powder was pre-sintered at 850 °C for 6 h, and the pre-sintered powder was subjected to secondary ball milling for 12 h;

[0062] S4. To achieve better shaping, 5 wt% polyvinyl alcohol (PVA) was added to the powder after secondary ball milling for granulation, and the granules were pressed into ceramic wafers with a diameter of 10 mm and a thickness of about 1 mm;

[0063] S5. Heat the ceramic sheet to 850 °C at a rate of 1 °C / min and hold for 2 h for debinding treatment to remove the binder;

[0064] S6. Sinter the debound ceramic sheet at 1140 °C for 3 h to obtain the ceramic material sample BNC 0.03 H 0.03 T-SBT.

[0065] Example 2

[0066] In this example, the chemical formula of the BNT-based high energy storage performance ceramic material is:

[0067] 0.65(Bi 0.5 Na 0.5 ) 0.05 Ca 0.05 Hf 0.05 Ti 0.05 O3-0.35Sr 0.7 Bi 0.2 TiO3, and the preparation process includes the following steps:

[0068] S1. Weigh the raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3 according to the stoichiometric ratio;

[0069] S2. Ball mill the raw materials in absolute ethanol as the medium at 250 r / min for 12 h to obtain dry powder;

[0070] S3. Pre-sinter the ball-milled powder at 850 °C for 6 h, and perform secondary ball milling on the pre-sintered powder, and the secondary ball milling time is 12 h;

[0071] S4. To better form, add 5 wt% polyvinyl alcohol (PVA) to the powder after secondary ball milling for granulation, and press the granules into ceramic sheets with a diameter of 10 mm and a thickness of about 1 mm;

[0072] S5. Heat the ceramic sheet to 850 °C at a rate of 1 °C / min and hold for 2 h for debinding treatment to remove the binder;

[0073] S6. Sinter the debound ceramic sheet at 1140 °C for 3 h to obtain the ceramic material sample BNC 0.05 H 0.05 T-SBT.

[0074] Example 3

[0075] In this example, the chemical formula of the BNT-based high energy storage performance ceramic material is:

[0076] 0.65(Bi 0.5 Na0.5 ) 0.03 Ca 0.07 Hf 0.07 Ti 0.03 O3 - 0.35Sr 0.7 Bi 0.2 TiO3, the preparation process includes the following steps:

[0077] S1. Weigh the raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3 according to the stoichiometric ratio;

[0078] S2. Ball - mill the raw materials in anhydrous ethanol as the medium at 250 r / min for 12 h to obtain dry powder;

[0079] S3. Pre - sinter the ball - milled powder at 850 °C for 6 h, and perform secondary ball - milling on the pre - sintered powder. The secondary ball - milling time is 12 h;

[0080] S4. To better form, add 5 wt% polyvinyl alcohol (PVA) to the powder after secondary ball - milling for granulation, and press the granules into a ceramic sheet with a diameter of 10 mm and a thickness of about 1 mm;

[0081] S5. Heat the ceramic sheet at a rate of 1 °C / min to 850 °C and hold for 2 h for debinding treatment to remove the binder;

[0082] S6. Sinter the ceramic sheet after debinding at 1140 °C for 3 h to obtain the ceramic material sample BNC 0.07 H 0.07 T - SBT.

[0083] Example 4

[0084] In this example, the chemical formula of the BNT - based high - energy - storage performance ceramic material is:

[0085] 0.65(Bi 0.5 Na 0.5 ) 0.01 Ca 0.09 Hf 0.09 Ti 0.01 O3 - 0.35Sr 0.7 Bi 0.2 TiO3, the preparation process includes the following steps:

[0086] S1. Weigh the raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3 according to the stoichiometric ratio;

[0087] S2. Ball - mill the raw materials in anhydrous ethanol as the medium at 250 r / min for 12 h to obtain dry powder;

[0088] S3. Pre-sinter the ball-milled powder at 850 °C for 6 h, and perform secondary ball milling on the pre-sintered powder for 12 h;

[0089] S4. To better form, add 5 wt% polyvinyl alcohol (PVA) to the powder after secondary ball milling for granulation, and press the granules into ceramic wafers with a diameter of 10 mm and a thickness of about 1 mm;

[0090] S5. Heat the ceramic wafers to 850 °C at a rate of 1 °C / min, hold for 2 h for debinding treatment to remove the binder;

[0091] S6. Sinter the debound ceramic wafers at 1150 °C for 3 h to obtain the ceramic material sample BNC 0.09 H 0.09 T-SBT.

[0092] Comparative example

[0093] Make the following modifications to the content disclosed in Example 1 or Example 2 or Example 3 or Example 4,

[0094] Do not introduce Ca 2+ , Hf 4+ , that is, x = y = 0, to obtain the ceramic material sample BNT-SBT.

[0095] Ultrasonically clean and double-side polish the ceramic material samples prepared in Examples 1-4 and the comparative example, and then coat silver electrodes for electrical property testing.

[0096] And use a grinding machine to reduce the ceramic thickness to 0.15 mm and then perform energy storage performance testing.

[0097] The test analysis results are as follows:

[0098] Figure 1 It shows that the samples prepared in Example 1, Example 2, Example 3, Example 4 and the comparative example all exhibit a characteristic perovskite structure, and the main diffraction peak is consistent with the standard PDF card #97-28-0381. And the diffraction peaks in the (111) and (200) directions show obvious splitting, indicating that doping leads to an increase in structural distortion or the emergence of different crystal phases.

[0099] Figure 2 It shows that the pure BNT-SBT ceramic exhibits a large polarization (P m ) and a high remanent polarization (P r ). With the increase of the content of Ca 2+ and Hf 4 + , P m and P rDecrease correspondingly, and the P-E loop becomes narrower.

[0100] Figure 3 The experimental results can be summarized in Table 1.

[0101] Table 1 Energy storage performance parameters of the ceramic materials prepared in Examples 1-4 and Comparative Examples.

[0102] Table 1

[0103]

[0104] Thus, the recoverable energy storage density of BNC 0.07 H 0.07 T-SBT ceramics reaches 3.45 J / cm³ under an electric field of 250 kV / cm 3 , and the energy efficiency is 83%.

[0105] Figure 4 Indicates P m , P r and ΔP (the difference between P m and P r ) shows a decreasing trend with the increase of doping amount. Due to the lattice distortion or coexistence of different crystal phases caused by doping, the flipping of ferroelectric domains is inhibited.

[0106] Figure 5 Indicates that at all doping levels, the tetragonal (P4bm) phase and the rhombohedral (R3c) phase coexist, and the phase ratio changes with the change of doping concentration. For BNT-SBT ceramics, the structure is mainly dominated by the R phase, which is consistent with the known structure of pure BNT. However, with the increase of Ca 2+ and Hf 4+ concentration, a significant phase transition occurs, and the proportion of the tetragonal phase increases.

[0107] When x = y = 0.07, it changes from the main rhombohedral structure to an equilibrium state of tetragonal and rhombohedral phases close to 1:1, indicating that the A / B substitution co-doping of Ca 2+ and Hf 4+ plays a key role in the near-equimolar relationship between the two phases.

[0108] Figure 6 Indicates that all samples have clear grain morphology and dense microstructure. And with the increase of Ca 2+ and Hf 4+ doping concentration, the grain size continuously decreases, reaching a minimum average grain size of about 0.68 μm. This indicates that Ca 2+ and Hf 4+The effective incorporation inhibits grain growth. However, when the doping concentration reaches x = y = 0.09, the grain size increases again, reaching 0.73 μm. At this time, the ratio of the R3c and P4bm phases changes, and the ratio of the tetragonal phase is the highest. Since the tetragonal phase has a larger lattice distortion and weaker domain wall motion, this may promote the coalescence and enlargement of grains. With the increase of the doping level, the observed decrease in grain size can be attributed to Hf 4+ introduces a larger ionic radius reduces the oxygen vacancy content, slows down the ionic diffusion rate, and inhibits grain and grain boundary diffusion during sintering. This is beneficial to improving the breakdown strength and increasing the energy storage density.

[0109] Figure 7 It is shown that the BNC prepared in Example 3 0.07 H 0.07 The energy storage performance of the H-T-SBT ceramic is higher than that of the existing BNT, BT, and KNN lead-free ceramics.

[0110] Figure 8 It is shown that the BNC prepared in Example 3 0.07 H 0.07 For the H-T-SBT ceramic, as the electric field strength increases, the P-E loop shows an elongated shape, and the energy storage density increases significantly. The change in energy efficiency (η) is only 1.4%, and the energy efficiency (η) always remains above 83%. Therefore, the BNC 0.07 H 0.07 The H-T-SBT ceramic has stable energy storage performance under different applied electric fields. At 250 kV / cm, the maximum W rec value reaches 3.45 J / cm 3 , and η is 83%.

[0111] Figure 9 It is shown that the BNC prepared in Example 3 0.07 H 0.07 After 10 cycles of the H-T-SBT ceramic at 150 kV / cm 7 , the ferroelectric hysteresis loop still remains elongated, with only slight polarization fluctuations. The increase in the coercive field (E c ) and the remanent polarization (P r ) leads to an increase in the total energy storage.

[0112] In practical applications, capacitors must withstand long-term use and repeated charge-discharge cycles. Therefore, fatigue resistance is crucial for dielectric energy storage ceramics. And it can be seen through Figure 9 that the ceramics prepared by the present invention have good fatigue resistance.

[0113] Figure 10 It is shown that the BNC prepared in Example 3 0.07 H0.07 When the temperature of the T-SBT ceramic rises from 30 °C to 150 °C, W rec decreases from 1.47 J / cm 3 to 1.3 J / cm 3 , only a 11% reduction. In addition, η initially increases and then decreases, but still remains above 85%. Therefore, this ceramic has excellent thermal breakdown performance in a wide temperature range.

[0114] In summary, in the present invention, the introduction of Ca 2+ ions induces lattice distortion and grain refinement, significantly improving the breakdown strength and local polarization characteristics. At the same time, Hf 4+ doping stabilizes the TiO6 octahedral structure, effectively reducing the dielectric loss, and forms a nano-domain structure, weakening the inter-domain coupling and further enhancing the polarization response. The experimental results show that when the doping concentration is x = y = 0.07, the ratio of the R3c phase and the P4bm phase is close to equilibrium, achieving the best structural balance. Under an electric field of 250 kV / cm, the recoverable energy storage density (W rec ) of the BNCxHyT-SBT ceramic reaches 3.45 J / cm 3 , while the energy storage efficiency (η) exceeds 83%. In addition, the lattice distortion induced by doping significantly improves the thermal stability and low-loss characteristics, enhancing the overall dielectric properties, thus maximizing the energy storage performance. Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0115] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A BNT-based ceramic material with high energy storage performance, characterized in that, Its chemical general formula is: λ(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-(1-λ)Sr 0.7 Bi 0.2 TiO3, Among them, 0 < x ≤ 0.09, 0 < y ≤ 0.

09.

2. The BNT-based high energy storage performance ceramic material according to claim 1, wherein Its chemical general formula is: λ(Bi 0.5 Na 0.5 ) 0.03 Ca 0.07 Hf 0.07 Ti 0.03 O3-(1-λ)Sr 0.7 Bi 0.2 TiO3。 3. The BNT-based ceramic material with high energy storage performance according to claim 1, characterized in that, Its chemical general formula is: 0.65(Bi 0.5 Na 0.5 ) 0.03 Ca 0.07 Hf 0.07 Ti 0.03 O3 - 0.35Sr 0.7 Bi 0.2 TiO3.

4. A method for preparing the BNT-based high energy storage performance ceramic material according to claim 1, characterized in that, It includes the following steps: S1. According to the chemical formula λ(Bi 0.5 Na 0.5 ) 1-x Ca x Hf y Ti 1-y O3-(1-λ)Sr 0.7 Bi 0.2 TiO3, weigh out the raw materials Bi2O3, CaCO3, HfO2, SrCO3, TiO2 and Na2CO3; S2. Ball-mill the raw materials to obtain dry powder; S3. Pre-sinter the ball-milled powder, and perform secondary ball-milling on the pre-sintered powder; S4. Add 5wt% polyvinyl alcohol to the powder after secondary ball-milling for granulation, and press the granules into ceramic sheets; S5. Perform degumming treatment on the ceramic sheets; S6. Sinter the degummed ceramic sheets to obtain ceramic material samples.

5. The preparation method of the BNT-based ceramic material with high energy storage performance according to claim 4, wherein, In S2, the ball-milling time of the raw materials is 10 - 14h, and the ball-milling medium is zirconia balls and absolute ethanol.

6. The preparation method of the BNT-based ceramic material with high energy storage performance according to claim 4, wherein, In S3, the pre-sintering temperature of the ball-milled powder is 800 - 900 °C, the pre-sintering time is 5 - 6h, and the time of secondary ball-milling is 10 - 14h.

7. The preparation method of the BNT-based ceramic material with high energy storage performance according to claim 4, characterized in that, In S5, the process of degumming treatment is to heat the ceramic sheets at a rate of 1 - 2 °C / min to 800 - 900 °C and keep them at this temperature for 1 - 3h.

8. The preparation method of the BNT-based ceramic material with high energy storage performance according to claim 4, characterized in that, In S6, the sintering temperature of the ceramic sheets is 1140 - 1150 °C, and the sintering time is 2 - 4h.

9. A ceramic energy storage capacitor, characterized in that, The ceramic energy storage capacitor includes the BNT-based high energy storage performance ceramic material described in any one of claims 1 - 3.

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