High-entropy energy storage ceramic compound, preparation method, capacitor and application

Abstract

The invention provides a high-entropy energy storage ceramic compound, a preparation method, a capacitor and application, the chemical general formula of the high-entropy energy storage ceramic compound is (Bi < 0.2 > Na < 0.2 > Ba < 0.2 > K < 0.2 > La < 0.2 >) TiO < 3-x > Ca (Hf < 0.7 > Zr < 0.3 >) O3, and the value of x is 0.1-0.2. In the high-entropy energy storage ceramic compound provided by the invention, the grain size of the ceramic is refined and the remanent polarization is reduced by utilizing the synergistic effect of the equimolar high-entropy ceramic matrix and the relaxation agent Ca (Hf0. 7Zr0. 3) O3, the defects of low efficiency and large leakage current of Bi0. 5Na0. 5TiO3 are effectively improved, and the energy storage density and the energy storage efficiency are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of capacitors, and particularly relates to a high-entropy energy storage ceramic composite, a preparation method, a capacitor and an application. Background Art

[0002] Dielectric energy storage ceramics are a type of energy storage materials with high power density, and are widely used in fields such as pulsed power devices, new energy vehicles, high-voltage inverters, etc., and have important application value and national defense significance in the fields of daily electronic components and national defense security. The research on dielectric energy storage materials mainly focuses on three major material systems: one is polymer-based composite dielectrics, such as biaxially oriented polypropylene films, ceramic-PVDF composite films, etc. Although such materials have high energy storage density, and currently some materials (such as polypropylene films) have been commercialized, they need to be improved in terms of thermal stability and short cycle charge-discharge life; the second is glass-ceramics or glass ceramics. Due to their uniform grains and high density, they also exhibit relatively high energy storage density. However, problems such as interface polarization and full energy release restrict their development; the third is ceramic-based dielectrics. Due to their wide range of tolerance factors, large room for adjustment, and numerous material systems, and at the same time having characteristics such as stable structure, high thermal stability, and long cycle service life, they have been studied the most widely. The research on ceramic-based dielectrics includes barium titanate (BaTiO3) in the early 1980s, which has a high dielectric constant (ε>3000) and a low breakdown field strength (<100 kV / cm), and potassium sodium niobate (KNN) lead-free ceramics in the 2010s. At present, most of the ceramic-based dielectric energy storage materials are PbZrO3-based materials, such as (Pb,La)(Zr,Ti)O3 antiferroelectric ceramics, which have high energy storage density and are applied to some specific products.

[0003] Although great progress has been made in the research of energy storage dielectric materials, there is still a large gap from the actual needs. On the one hand, high power, light weight, and miniaturization put forward higher requirements for high-density energy storage dielectric ceramics. On the other hand, with the increasing international attention to environmental protection issues, due to the potential harm of lead to the human body and the environment, the development of environmentally friendly lead-free energy storage dielectrics has become a hot topic in recent years. Therefore, developing a new system of high-energy storage lead-free ceramic dielectrics has scientific research and practical application value.

[0004] Environmentally friendly Bi 0.5 Na 0.5 TiO3 has a large saturation polarization value, a relatively high Curie temperature, and low dielectric loss, and has broad application prospects in the field of dielectric energy storage. But pure Bi 0.5 Na 0.5TiO3 ceramics have a large remanent polarization and a small breakdown field strength, resulting in a large energy loss, and both the energy storage density and the energy storage efficiency are relatively low. Therefore, it is necessary to provide a BNT-based ceramic energy storage material that is environmentally friendly, has small grain size, large saturation polarization value, low remanent polarization, high energy density and energy storage efficiency, low production cost, and high stability. Summary of the Invention

[0005] The purpose of the present invention is to overcome the disadvantages and deficiencies in the prior art, and provide a high-entropy energy storage ceramic composite. By using an equimolar high-entropy ceramic matrix and a relaxor Ca(Hf 0.7 Zr 0.3 )O3 to act synergistically, the grain size of the ceramic is refined, the remanent polarization is reduced, and the disadvantages of low efficiency and large leakage current of Bi 0.5 Na 0.5 TiO3 are effectively improved, and the energy storage density and energy storage efficiency are enhanced.

[0006] The present invention is realized through the following technical solutions:

[0007] A high-entropy energy storage ceramic composite with a chemical general formula of (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x is 0.1 to 0.2.

[0008] In the high-entropy energy storage ceramic composite provided by the present invention, the chemical general formula of the high-entropy energy storage ceramic composite is (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. Bi 0.5 Na 0.5 TiO3 with high polarization is selected as the first matrix, and different broadband oxides Ba2O3 and La2O3 are added to increase the grain resistance, destroy the long-range ferroelectric order, and improve the ferroelectric properties of the material; at the same time, K + is introduced to improve the crystal structure, enhance the mechanical stability and electrical properties; the first matrix Bi 0.5 Na 0.5 TiO3 and Ba 2+ , La 3+Form an equimolar high-entropy ceramic matrix. Since the ceramic structure with equimolar high entropy will form a highly disordered state, causing low breakdown strength or low polarization, resulting in insufficient energy storage performance, Ca(Hf 0.7 Zr 0.3 )O3 is selected as an additive to improve the breakdown field strength. The high-entropy energy storage ceramic composite provided by the present invention is designed by high entropy. By utilizing the synergy of the equimolar high-entropy ceramic matrix and the relaxor Ca(Hf 0.7 Zr 0.3 )O3, the grain size of the ceramic is refined, the remanent polarization is reduced, and the disadvantages of low efficiency and large leakage current of Bi 0.5 Na 0.5 TiO3 are effectively improved, and the energy storage density and energy storage efficiency are enhanced.

[0009] The present invention also provides a preparation method of the above-mentioned high-entropy energy storage ceramic composite, including the following steps: using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2 and ZrO2 as raw materials, and formulating according to the stoichiometric ratio of the chemical general formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 to obtain a raw material mixture, where the value of x is 0.1 to 0.2; processing the raw material mixture to form raw material powder; granulating the raw material powder to obtain raw material particles; forming and pressing the raw material particles to obtain a ceramic green body; sintering the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0010] In the preparation method of the high-entropy energy storage ceramic composite provided by the present invention, the raw materials are formulated according to the stoichiometric ratio of the chemical general formula, and a Bi 0.5 Na 0.5 TiO3 matrix is formed during the sintering process, and broadband oxides BaCO3, La2O3 and the relaxor Ca(Hf 0.7 Zr 0.3 )O3 are introduced to obtain a high-entropy energy storage ceramic composite with high energy storage.

[0011] Further, in the step of processing the raw material mixture to form raw material powder, the powder is ball-milled once, pre-fired at high temperature, ball-milled twice, and dried. By processing the raw materials to form raw material powder through two ball-milling processes and high-temperature pre-firing, a raw material powder with uniform mixing and finer particles is obtained, which is beneficial to obtaining a high-entropy energy storage ceramic composite with a dense structure and uniform components in the end.

[0012] Further, in the step of high-temperature pre-firing in the process of processing the raw material mixture to form raw material powder, the high-temperature pre-firing process is to calcine the powder at 800 - 900 °C for 180 - 200 min, control the heating rate at 5 - 8 °C / min, and after the calcination, naturally cool to room temperature in the furnace to obtain pre-fired powder. By controlling the temperature, time, and heating rate of the high-temperature pre-firing process, the oxides in the raw materials can fully react to form a ferrite precursor with a specific crystal structure, reduce the firing shrinkage rate, make the reaction more complete, and partially densify the raw materials, reducing the porosity, thereby improving its mechanical properties.

[0013] Further, in the step of granulating the raw material powder to obtain raw material particles, the raw material powder is dried, ground, sieved, the binder is added and then ground again, and sieved again to obtain raw material particles. Mixing the raw material powder with the binder to form raw material particles with a certain particle size is convenient for molding and pressing.

[0014] Further, in the step of molding and pressing the raw material particles to obtain a ceramic green body, the raw material particles are pressed into shape, the pressure is controlled at 8 - 10 MPa, and the pressure is maintained to obtain a ceramic green body. By molding and pressing the raw material particles to obtain a ceramic green body and controlling the pressure and pressure holding time, a dense ceramic green body is obtained.

[0015] Further, in the step of sintering the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, the ceramic green body is sintered at 1150 - 1250 °C, and the sintering time is 120 - 150 min to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. Control the sintering temperature and sintering time to make the oxide reaction complete, introduce different broadband oxide systems to form an equimolar high-entropy ceramic structure with Bi 0.5 Na 0.5 TiO3, and introduce Ca(Hf 0.7 Zr0.3 )Using O3 as a relaxant, a high-entropy energy storage ceramic composite is obtained.

[0016] Furthermore, the ceramic green body is sintered to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. In this step, the heating rate is controlled at 5 - 8 °C / min, and the ceramic green body is sintered at 1150 - 1250 °C. Controlling the heating rate is beneficial to the formation of a dense structure.

[0017] The present invention also provides a high-entropy ceramic capacitor, which includes the above-mentioned high-entropy energy storage ceramic composite.

[0018] The present invention also provides the application of the above-mentioned high-entropy energy storage ceramic composite in high-power pulse devices.

[0019] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0020] Figure 1 is a flow chart of the preparation method of the high-entropy energy storage ceramic composite.

[0021] Figure 2 is the XRD diffraction pattern of the high-entropy energy storage ceramic composite of Example 3.

[0022] Figure 3 is the SEM characterization diagram of the high-entropy energy storage ceramic composite of Example 3.

[0023] Figure 4 is the energy storage performance analysis diagram of the high-entropy energy storage ceramic composite of Example 3.

[0024] Figure 5 is the frequency stability analysis test diagram of the high-entropy energy storage ceramic composite of Example 3.

[0025] Figure 6 is the temperature stability analysis test diagram of the high-entropy energy storage ceramic composite of Example 3.

[0026] Figure 7 is the fatigue stability test diagram of the high-entropy energy storage ceramic composite of Example 3.

[0027] Figure 8 is the over-damping curve analysis test diagram of the high-entropy energy storage ceramic composite of Example 3. Detailed Embodiments

[0028] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It can be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention, rather than limiting the embodiments of the present invention. In addition, it should be noted that for the sake of description, only parts related to the embodiments of the present invention are shown in the drawings, rather than all the structures.

[0029] In addition, the terms first, second, third, etc. in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features.

[0030] Similarly, the terms "fixed" and "connected" are also used in the specification and claims, and should not be understood as being limited to direct connection. Therefore, the expression "device A is connected to device B" should not be limited to device A being directly connected to device B in the device or system. It means that there is a path between device A and device B, which can be a path including other devices or tools.

[0031] Example 1

[0032] This embodiment provides a high-entropy energy storage ceramic composite with a chemical general formula of (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x ranges from 0.1 to 0.2.

[0033] In the high-entropy energy storage ceramic composite provided by this embodiment, the chemical general formula of the high-entropy energy storage ceramic composite is (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. Bi 0.5 Na 0.5 TiO3 with high polarization is selected as the first matrix, and different broadband oxides Ba2O3 and La2O3 are added to increase the grain resistance, destroy the long-range ferroelectric order, and improve the ferroelectric properties of the material; at the same time, K + is introduced to improve the crystal structure and enhance the mechanical stability and electrical properties; due to the first matrix Bi 0.5 Na 0.5TiO3 and Ba 2+ , La 3+ form an equimolar high-entropy ceramic matrix. Since the equimolar high-entropy ceramic structure will form a highly disordered state, causing low breakdown strength or low polarization, resulting in insufficient energy storage performance, Ca(Hf 0.7 Zr 0.3 )O3 is selected as an additive to improve the breakdown field strength. The high-entropy energy storage ceramic composite provided by the present invention is designed by high-entropy. By using the equimolar high-entropy ceramic matrix and the relaxor Ca(Hf 0.7 Zr 0.3 )O3 to act synergistically, the grain size of the ceramic is refined, polar nano-regions are induced, and the low breakdown strength caused by the high disorder of the equimolar high-entropy matrix is greatly improved, the breakdown field strength is increased, and at the same time the remanent polarization is reduced, effectively improving the disadvantages of low efficiency and large leakage current of Bi 0.5 Na 0.5 TiO3, and the energy storage density and energy storage efficiency are improved.

[0034] In one embodiment, the value of x in (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 is 0.1.

[0035] In one embodiment, the value of x in (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 is 0.15.

[0036] In one embodiment, the value of x in (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 is 0.2.

[0037] For the high-entropy energy storage ceramic composite of this example, at a high field strength of 485 kV / cm, (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr0.3 ) The O3 ceramic has an optimal recoverable energy storage density (W) of 6.77 J / cm 3 and an optimal energy storage efficiency (η) of 86%. When this high-entropy energy storage ceramic material is used in capacitors, it can greatly improve the energy storage density and energy storage efficiency of the capacitors, and its performance is superior to that of most other lead-free bismuth titanate-based energy storage materials. Moreover, in practical applications, (Bi rec ) and numerical value of 86% of the optimal energy storage efficiency (η), when the high entropy energy storage ceramic material is used in a capacitor, can greatly improve the energy storage density and energy storage efficiency of the capacitor, and its performance is better than most other lead-free bismuth titanate-based energy storage materials; and in practical applications, (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramics also have excellent frequency stability, temperature stability, and fatigue stability.

[0038] Example 2

[0039] This embodiment provides a preparation method for the high-entropy energy storage ceramic composite of Embodiment 1. Figure 1 It is a flowchart of the preparation method for the high-entropy energy storage ceramic composite. Please refer to Figure 1 , and the preparation method for the high-entropy energy storage ceramic composite includes the following steps:

[0040] Step S1: Using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2, and ZrO2 as raw materials, prepare a raw material mixture according to the stoichiometric ratio of the chemical general formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x ranges from 0.1 to 0.2.

[0041] Step S2: Process the raw material mixture to form raw material powder.

[0042] Step S3: Granulate the raw material powder to obtain raw material particles.

[0043] Step S4: Compress and tablet the raw material particles to obtain a ceramic green body.

[0044] Step S5: Sinter the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr0.3 )O3。

[0045] In the preparation method of the high-entropy energy storage ceramic composite provided in this embodiment, the raw materials are proportioned according to the stoichiometric ratio of the chemical general formula, and Bi 0.5 Na 0.5 TiO3 matrix is formed during the sintering process, and broadband oxides BaCO3, La2O3 and relaxant Ca(Hf 0.7 Zr 0.3 )O3 are introduced to obtain a high-entropy energy storage ceramic composite with high energy storage.

[0046] In this embodiment, in step S2, the raw material mixture is subjected to primary ball milling, high-temperature pre-sintering, secondary ball milling and drying. The raw materials are processed to form raw material powders. Through two ball millings and high-temperature pre-sintering, raw material powders with uniform mixing and finer particles are obtained, which is beneficial to obtaining a high-entropy energy storage ceramic composite with a dense structure and uniform components finally.

[0047] In this embodiment, in step S2, during the primary ball milling process, ethanol and zirconia grinding balls are added to the raw material mixture, and the total mass of the raw material mixture: the total mass of the zirconia grinding balls = 1:1. The diameter of the zirconia grinding balls is 3 - 6 mm, where the number of 6-mm grinding balls: the number of 4 - 5-mm grinding balls: the number of 3-mm grinding balls = 1:2:3. The zirconia grinding balls have high density and delicate texture. After grinding, the surface finish of the raw material mixture is high and the friction coefficient is small. Using zirconia grinding balls with different particle sizes has better grinding effect and efficiency than using zirconia grinding balls of a single size. The procedures of primary ball milling and secondary ball milling are the same.

[0048] In this embodiment, in step S2, the high-temperature pre-sintering process is to calcine the powder at 800 - 900 °C for 180 - 200 min, and the heating rate is controlled at 5 - 8 °C / min. After calcination, it is cooled to room temperature naturally with the furnace to obtain the pre-calcined powder. Controlling the temperature, time and heating rate of the high-temperature pre-sintering process enables the oxides in the raw materials to react fully, forming a ferrite precursor with a specific crystal structure, reducing the sintering shrinkage rate, making the reaction more complete, and partially densifying the raw materials, reducing the porosity, thereby improving its mechanical properties.

[0049] Specifically, the raw material mixture after primary ball milling is dried and placed in a first alumina crucible. After the first alumina crucible is placed upright on the alumina sintering plate, a second alumina crucible is buckled and sleeved outside the first alumina crucible, and a circle of alumina powder is covered at the edge of the caliber of the second alumina crucible for sealing, and then it is calcined at a constant temperature of 800 - 900 °C and cooled to room temperature with the furnace.

[0050] In this embodiment, in step S2, the pre-sintered powder obtained by high-temperature pre-sintering is dried to volatilize ethanol, and the pre-sintered powder without ethanol is ground, which is beneficial to increasing the density of the high-entropy energy storage ceramic composite formed by subsequent sintering. The specific operation is as follows: put the pre-sintered powder without ethanol into a mortar and grind it with an agate rod.

[0051] To achieve a better density enhancement effect, grinding can be carried out respectively after the first ball milling, after the high-temperature pre-sintering, and after the second ball milling.

[0052] In this embodiment, in step S3, the raw material powder is dried, ground, sieved, a binder is added and then ground again, and then sieved again to obtain raw material particles. Mixing the raw material powder with the binder to form raw material particles with a certain particle size is convenient for molding and pressing.

[0053] In this embodiment, in step S4, the raw material particles are pressed into a shape, the pressure is controlled at 8-10 MPa, and the pressure is maintained to obtain a ceramic blank. Molding and pressing the raw material particles to obtain a ceramic blank, controlling the pressure and the pressure holding time, to obtain a dense ceramic blank.

[0054] Specifically, in step S4, the raw material particles obtained in step S3 are loaded into a pressing die, and are pressed into a shape by a press, and the pressure is maintained for 60-90 s to obtain a ceramic blank.

[0055] In this embodiment, in step S5, the ceramic blank is sintered at 1150-1250 °C, and the sintering time is 120-150 min to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. Control the sintering temperature and the sintering time to make the oxide reaction complete, introduce different broadband oxide systems to form an equimolar high-entropy ceramic structure with Bi 0.5 Na 0.5 TiO3, and introduce Ca(Hf 0.7 Zr 0.3 )O3 as a relaxant to obtain a high-entropy energy storage ceramic composite.

[0056] In this embodiment, in step S5, the heating rate is controlled at 5-8 °C / min, and the ceramic blank is sintered at 1150-1250 °C. Controlling the heating rate is beneficial to forming a dense structure.

[0057] In this embodiment, in step S3, part of the raw material powder is taken out, the remaining raw material powder is made into raw material particles, and the raw material particles are pressed into a ceramic blank in step S4; in step S5, the pressed ceramic blank is placed on an alumina sintering plate, the remaining raw material powder in step S3 is covered on the ceramic blank, and an alumina crucible is inverted to cover the ceramic blank covered with the raw material powder, and after constant temperature calcination, it is cooled to room temperature with the furnace. Since Bi is easily volatilized at high temperatures, in order to ensure the purity and density of the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 sintered from the ceramic blank, the method of covering the ceramic blank with part of the raw material powder is adopted to volatilize Bi in the raw material powder and reduce the volatilization of Bi in the ceramic blank.

[0058] During the high-temperature sintering process of step S5, highly polarized Bi 0.5 Na 0.5 TiO3 is formed as the first matrix, and wide-bandgap oxides Ba2O3 and La2O3 are introduced. Among them, the E of Ba2O3 g = 3.7 eV, and the E of La2O3 g = 5.5 eV. The wide-bandgap oxides are used to increase the grain resistance; at the same time, K is introduced during the high-temperature sintering + to improve the crystal structure, enhance the mechanical stability and electrical properties, and form an equimolar high-entropy ceramic matrix (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3; since the equimolar high-entropy ceramic structure will form a highly disordered state, resulting in low breakdown strength or low polarization and insufficient energy storage performance, Ca(Hf 0.7 Zr 0.3 )O3 is selected as an additive to improve the breakdown field strength, and entropy increase is achieved again through Ca(Hf 0.7 Zr 0.3 )O3, and the relaxation behavior is caused by the high-entropy effect. The high-entropy energy storage ceramic composite provided by the present invention uses the equimolar high-entropy ceramic matrix and the relaxant Ca(Hf 0.7 Zr 0.3 )O3 through high-entropy design and synergistic action. While introducing wide-band series oxides to increase the grain resistance, a relaxant is introduced to improve the low breakdown strength caused by the highly disordered state, refine the grain size of the ceramic, reduce the remanent polarization, and effectively improve Bi 0.5 Na 0.5The disadvantages of low TiO3 efficiency and large leakage current are overcome, enhancing the energy storage density and energy storage efficiency.

[0059] Example 3

[0060] This embodiment provides a high-entropy energy storage ceramic composite, which is prepared by the following preparation method:

[0061] Step S1: Using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2, and ZrO2 as raw materials, prepare a raw material mixture according to the stoichiometric ratio of the chemical formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x is 0.15. Among them, the raw materials are shown in Table 1.

[0062] Table 1 Preparation raw materials of (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3

[0063]

[0064]

[0065] Using Bi2O3, Na2CO3, BaCO3, La2O3, K2CO3, TiO2, CaCO3, HfO2, and ZrO2 shown in Table 1 as raw materials, weigh and mix the above raw materials according to the stoichiometric ratio of the chemical formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 system to obtain a raw material mixture, where the value of x is 0.1 - 0.2. Since Bi ions and Na ions in the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3 matrix are prone to volatilization, therefore, in order to avoid the loss of ceramics during the subsequent mixing and ball milling process, during the batching stage, (Bi 0.2Na 0.2 Ba 0.2 K 0.2 La 0.2 ) The ratio of TiO3 is greater than the stoichiometric ratio, that is, the amounts of Bi2O3 and K2CO3 will be 1% more than the stoichiometry.

[0066] Step S2: Process the raw materials to form raw material powder. Perform primary ball milling, high-temperature pre-sintering, secondary ball milling, and drying on the raw material mixture. Specifically:

[0067] Primary ball milling: Put the raw material mixture into a nylon grinding tube, add ethanol and zirconia grinding balls with different diameters for ball milling, control the rotation speed of the ball mill at 380 revolutions per minute, set the primary ball milling time to 12 - 24 hours, and dry the mixture at 80°C after ball milling. Among them, zirconia is used as the grinding medium and ethanol is used as the grinding solvent. The total mass of the prepared raw materials: the total mass ratio of zirconia is 1:1; the diameter range of the zirconia grinding balls is 3 - 6 mm, and the number ratio of the zirconia grinding balls is controlled at 6 mm grinding balls: 4 - 5 mm grinding balls: 3 mm small grinding balls = 1:2:3.

[0068] High-temperature pre-sintering: Pour the raw material mixture after primary ball milling and drying into an agate mortar, grind it with an agate rod for 15 - 45 minutes, then pour the ground raw material mixture into an alumina crucible, calcine it at 800°C for 200 min in an air atmosphere in a muffle furnace, control the heating rate at 8°C / min, and let it cool naturally to room temperature with the furnace after calcination to obtain the pre-sintered powder.

[0069] Secondary ball milling: Put the pre-sintered powder obtained after high-temperature pre-sintering into a nylon ball mill tank, add ethanol and zirconia grinding balls with different diameters to obtain a mixture, control the rotation speed of the ball mill at 380 revolutions per minute, set the secondary ball milling time to 12 - 24 hours, and dry the mixture at 80°C after ball milling. Among them, zirconia is used as the grinding medium and ethanol is used as the grinding solvent. The total mass of the prepared raw materials: the total mass ratio of zirconia is 1:1; the diameter range of the zirconia grinding balls is 3 - 6 mm, and the number ratio of the zirconia grinding balls is controlled at 6 mm grinding balls: 4 - 5 mm grinding balls: 3 mm small grinding balls = 1:2:3.

[0070] Step S3: Granulate the raw material powder to obtain raw material particles. Specifically, after the processed powder undergoes steps such as drying, grinding, and sieving, the particle size is greatly reduced, and then an appropriate amount of binder PVA (3% - 5% concentration) is added to grind it, and the ground powder is sieved through a 100-mesh sieve to obtain raw material particles with a certain particle size.

[0071] Step S4: Molding and tabletting the raw material particles to obtain a ceramic green body. Specifically, the raw material particles obtained in Step S3 are loaded into a tabletting mold and uniaxially pressed and formed using a powder tabletting machine. The pressure is controlled at 9 MPa and the pressure is maintained for 60 seconds to obtain a (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic green body with a diameter of 13.5 mm and a thickness of 1.1 mm.

[0072] Step S5: Sintering the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0073] Specifically, the obtained (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic green body is placed in a muffle furnace, and the heating rate is controlled at 8 °C / min. It is slowly heated to 1200 °C and held for 150 min. After the holding is completed, the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic green body is naturally cooled to room temperature with the furnace, and a (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic sheet with a thickness of 1.1 mm is obtained.

[0074] Since Bi ions and K ions in (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3 are prone to volatilization. To reduce their volatilization, (Bi 0.2Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 ) The sintering process of the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic green body needs to be sintered in a buried manner, that is, the (Bi

[0075] )O3 ceramic green body is placed in a muffle furnace and covered with sample powder of the same composition before sintering.

[0076] For performance testing, the high-entropy energy storage ceramic composite is polished and electroplated with a bottom electrode and a top electrode to prepare a capacitor.

[0077] The operation process of polishing is as follows: 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic sheets are polished with 600-mesh green silicon carbide abrasive to about 0.1 mm to obtain BNBKLT-xCHZ ceramic thin sheets.

[0078] The operation process of electroplating the bottom electrode and the top electrode is as follows:

[0079] First, the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic thin sheets are put into a small ion sputtering instrument, and Au is used as the target material to grow an Au electrode film under a vacuum of 2×10 -3 Pa. The sputtering current is controlled to be 8 - 10 mA, and the target material is sputtered in an argon atmosphere for 50 seconds. The above sputtering operation is repeated 3 times. On the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr0.3 ) The bottom electrode is electroplated on the O3 ceramic wafer;

[0080] Next, a perforated mask plate is placed on the side of the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic wafer that has not been plated with an electrode. Then, the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic wafer is placed in a small ion sputtering instrument. Au is used as the target, and dot-shaped Au electrodes are grown under a vacuum of 2×10 -3 Pa. The sputtering current is controlled at 8 - 10 mA, and the target is sputtered in an argon atmosphere for 50 seconds. The above sputtering operation is repeated 3 times. The diameter of the holes on the mask plate is 1.5 mm, and the top electrode is electroplated on the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic wafer.

[0081] The following are the relevant performance tests on the high-entropy energy storage ceramic composite:

[0082] Figure 2 This is the XRD diffraction pattern of the high-entropy energy storage ceramic composite. Please refer to Figure 2 . The test results are obtained by testing with a X-ray diffractometer (X’Pert PRO, PANalytical X). All samples show a standard cubic perovskite structure without any impurity peaks, indicating that Ca 2+ , Hf 4+ and Zr 4+ are successfully dissolved in the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3 lattice; compared with pure (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3, Ca(Hf 0.7 Zr0.3 ) The incorporation of O3 causes the (110) diffraction peak to shift to a lower degree, indicating that the lattice expands after doping. The reason is that Ti at the B site 4+ (CN6, ) is replaced by Hf with a larger ionic radius 4+ (CN6, ) and Zr 4+ (CN4, ) resulting in lattice expansion. It can be seen that after introducing Ca(Hf 0.7 Zr 0.3 )O3, more disordered lattices are generated in the (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramics, which is beneficial to the enhancement of relaxation behavior.

[0083] Figure 3 is the SEM characterization diagram of the high-entropy energy storage ceramic composite. Please refer to Figure 3 . The test results are obtained by testing with a scanning electron microscope (ZEISS Gemini500). It can be seen from the figure that the ceramic has clear grain boundaries and a dense microstructure. The inset is the statistical distribution of the corresponding average grain size (GA), and its grain size is ~0.35 μm, which is attributed to the synergistic reaction with Ba 0.7 Zr 0.3 )O3 after introducing Ca(Hf 2+ , La 3+ . The increase in entropy value and the decrease in grain size contribute to achieving a high breakdown field strength.

[0084] Based on the introduction of Ba 2+ , La 3+ and K + in the high-entropy energy storage ceramic composite provided in this embodiment, the entropy value is further increased by introducing the relaxant Ca(Hf 0.7 Zr 0.3 )O3. For ceramic materials, its configurational entropy (ΔS config ) can be calculated according to the following formula:

[0085]

[0086] where x a , x b and x c are the mole fractions of ions at the A, B, and O sites respectively. According to research, when ΔS config ≥ 1.5R, the material can be defined as a high-entropy material.

[0087] With the increase of the doping content x of the relaxor Ca(Hf 0.7 Zr 0.3 )O3, the entropy values increase to 1.91R (x = 0.05), 2.06R (x = 0.10), 2.16R (x = 0.15), and 2.41R (x = 0.20), respectively. The increased entropy value refines the grain size, which decreases from 0.89 μm at x = 0 to 0.32 μm at x = 0.20. At the same time, the entropy increase improves the breakdown field strength. The breakdown field strength of the high-entropy energy storage ceramic composite increases from 200 kV / cm at x = 0.00 to 485 kV / cm at x = 0.15, which is also due to the relaxation behavior caused by the high-entropy effect.

[0088] Figure 4 is the analysis diagram of the energy storage performance of the high-entropy energy storage ceramic composite. Please refer to Figure 4 , and the high-entropy energy storage ceramic composite is tested by a ferroelectric tester (Radiant Technology). Figure 4 (a) shows the variation of the unipolar P-E loop of (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 with the electric field, and its corresponding W rec variation trend is as Figure 4 (b) shown. It can be found that in (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 with a high entropy value (2.16R), a huge recoverable energy storage density of about 6.77 J / cm 3 and an efficiency of about 86% are achieved. In addition, (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 also achieves a high breakdown field strength (E b = 485 kV / cm), which is due to the strong relaxation behavior caused by the high-entropy effect.

[0089] Through the ferroelectric tester, the prepared (Bi 0.2 Na0.2 Ba 0.2 K 0.2 La 0.2 )(TiO3-xCa(Hf 0.7 Zr 0.3 )O3 for stability analysis.

[0090] Figure 5 is the frequency stability analysis test chart of the high-entropy energy storage ceramic composite. Figure 5 In it, figure (b) corresponds to Figure 5 W in figure (a) of rec and the change values of η. Please refer to Figure 5 , in the frequency stability test, the change value of W rec is 2.8%.

[0091] Figure 6 is the temperature stability analysis test chart of the high-entropy energy storage ceramic composite. Among them, Figure 6 in figure (b) corresponds to Figure 6 W in figure (a) of rec and the change values of η. Please refer to Figure 6 , in the temperature stability test, the change value of W rec is 6.2%.

[0092] Figure 7 is the fatigue stability test chart of the high-entropy energy storage ceramic composite. Figure 7 In it, figure (b) corresponds to Figure 7 W in figure (a) of rec and the change values of η. Please refer to Figure 7 , in the fatigue stability test, the change value of W rec is 4.0%. The (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )(TiO3-xCa(Hf 0.7 Zr 0.3 ))O3 has excellent frequency stability, temperature stability, and fatigue stability. (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )(TiO3-xCa(Hf 0.7 Zr 0.3 ))O3 ceramics have excellent stability in practical applications.

[0093] Figure 8 is the over-damping curve analysis test chart of the high-entropy energy storage ceramic composite. Please refer to Figure 8 , (Bi0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 ceramic samples under various electric fields are shown as follows. Through calculation, in Figure 8 as shown, in Figure 8 (a), the discharge energy density (W dis ) versus electric field is plotted. As the electric field increases, W dis almost linearly increases. At 100 kV / cm, the maximum value of W dis is ~0.58 J / cm 3 . In addition, the charge-discharge time t 0.9 of the ceramic is ~79 ns. The high W dis and short t 0.9 values indicate that the BNBKLT-0.15CHZ high-entropy ceramic is a promising candidate for pulsed power system applications.

[0094] Example 4

[0095] This embodiment provides a high-entropy energy storage ceramic composite, which is prepared by the preparation method of Embodiment 3. The main difference from the preparation method of Embodiment 3 is as follows:

[0096] Step S1: Using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2, and ZrO2 as raw materials, according to the chemical formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 for batching to obtain a raw material mixture, where the value of x is 0.1.

[0097] Step S2: Processing the raw material mixture to form raw material powder.

[0098] In Step S2, the high-temperature pre-sintering process is to calcine the powder at 800 °C for 180 min, control the heating rate at 5 °C / min, and after the calcination is completed, let it cool naturally to room temperature in the furnace to obtain the pre-sintered powder.

[0099] Step S3: Granulating the raw material powder to obtain raw material particles.

[0100] Step S4: Molding and pressing the raw material particles to obtain a ceramic green body. The pressure is controlled at 8 Mpa and the pressure holding time is 60 seconds.

[0101] Step S5: Sintering the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0102] In step S5, the ceramic green body is sintered at 1150 °C for 120 min, and the heating rate is controlled at 5 °C / min to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0103] Example 5

[0104] This embodiment provides a high-entropy energy storage ceramic composite, which is prepared by the preparation method of Example 3. The main difference from the preparation method of Example 3 is:

[0105] This embodiment provides a high-entropy energy storage ceramic composite, which is prepared by the preparation method of Example 3. The main difference from the preparation method of Example 3 is:

[0106] Step S1: Using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2 and ZrO2 as raw materials, formulating a raw material mixture according to the stoichiometric ratio of the chemical general formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x is 0.2.

[0107] Step S2: Processing the raw material mixture to form raw material powder.

[0108] In step S2, the high-temperature pre-sintering process is to calcine the powder at 900 °C for 200 min, control the heating rate at 8 °C / min, and after the calcination is completed, let it cool naturally with the furnace to room temperature to obtain pre-sintered powder.

[0109] Step S3: Granulate the raw material powder to obtain raw material particles.

[0110] Step S4: Mold and press the raw material particles to obtain a ceramic green body. The pressure is controlled at 10 Mpa and the pressure holding time is 90 seconds.

[0111] Step S5: Sinter the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0112] In step S5, sinter the ceramic green body at 1250 °C for 150 min, and control the heating rate at 8 °C / min to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

[0113] The present invention is not limited to the above embodiments. If various changes or deformations to the present invention do not depart from the spirit and scope of the present invention, and if these changes and deformations are within the scope of the claims of the present invention and equivalent technical scope, then the present invention also intends to include these changes and deformations.

Claims

1. A high-entropy energy storage ceramic composite, characterized in that: The chemical general formula is (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3, where the value of x ranges from 0.1 to 0.

2.

2. A preparation method of the high-entropy energy storage ceramic composite as claimed in claim 1, characterized in that, Comprising the following steps: Using Bi2O3, Na2CO3, BaCO3, Na2CO3, TiO2, Bi2O3, CaCO3, HfO2 and ZrO2 as raw materials, according to the chemical formula (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3 for batching to obtain a raw material mixture, where the value of x is 0.1 - 0.2; Processing the raw material mixture to form raw material powder; Granulating the raw material powder to obtain raw material particles; Forming and pressing the raw material particles to obtain a ceramic green body; Sinter the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3 - xCa(Hf 0.7 Zr 0.3 )O3.

3. The preparation method of the high-entropy energy storage ceramic composite according to claim 2, characterized in that: In the step of processing the raw material mixture to form raw material powder, the powder is subjected to primary ball milling, high-temperature pre-sintering, secondary ball milling and drying.

4. The preparation method of the high-entropy energy storage ceramic composite according to claim 3, characterized in that: In the step of processing the raw material mixture to form raw material powder, the high-temperature pre-sintering process is to calcine the powder at 800-900 °C for 180-200 min, the heating rate is controlled at 5-8 °C / min, and after the calcination is completed, it is cooled naturally to room temperature with the furnace to obtain pre-sintered powder.

5. The preparation method of the high-entropy energy storage ceramic composite according to claim 2, characterized in that: In the step of granulating the raw material powder to obtain raw material particles, the raw material powder is dried, ground, sieved, a binder is added and then ground again, and sieved again to obtain raw material particles.

6. The preparation method of the high-entropy energy storage ceramic composite according to claim 2, characterized in that: In the step of forming and pressing the raw material particles to obtain a ceramic green body, the raw material particles are pressed into shape, the pressure is controlled at 8-10 MPa, and the pressure is maintained to obtain a ceramic green body.

7. The preparation method of the high-entropy energy storage ceramic composite according to any one of claims 2-6, characterized in that: Sinter the ceramic green body to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. In the step, sinter the ceramic green body at 1150 - 1250 °C for 120 - 150 min to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3.

8. The preparation method of the high-entropy energy storage ceramic composite according to claim 7, characterized in that: Sinter the ceramic blank to obtain (Bi 0.2 Na 0.2 Ba 0.2 K 0.2 La 0.2 )TiO3-xCa(Hf 0.7 Zr 0.3 )O3. In this step, control the heating rate to 5-8 °C / min and sinter the ceramic blank at 1150-1250 °C.

9. A high-entropy ceramic capacitor, characterized in that: Comprising the high-entropy energy storage ceramic composite described in claim 1.

10. Application of the high-entropy energy storage ceramic composite described in claim 1 in high-power pulse devices.

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