A non-equi-molar high-entropy relaxor ferroelectric ceramic, multilayer capacitor and preparation method and application thereof

Abstract

The present application relates to a non-equi-molar high-entropy relaxor ferroelectric ceramic, a multilayer capacitor and a preparation method and application thereof. The chemical composition of the non-equi-molar high-entropy relaxor ferroelectric ceramic is Bi 1 / 6 Na 1 / 6Ba 1 / 6 Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 TiO3, wherein M and N are selected from any two of La, Ce, Pr, Nd, Sm and Eu; preferably, M is Nd and N is Sm. The non-equi-molar high-entropy relaxor ferroelectric ceramic provided by the present application can reduce the remanent polarization and enhance the breakdown resistance while maintaining high maximum polarization, thereby achieving ultra-high energy storage density and energy storage efficiency in a Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6K 1 / 6 M 1 / 12 N 1 / 12 TiO3 multilayer ceramic capacitor.

Description

Technical Field

[0001] This invention belongs to the field of functional ceramic materials and devices, and relates to a non-equimolar high-entropy relaxor ferroelectric ceramic, a multilayer capacitor, its preparation method and application. Background Technology

[0002] With the rapid development of new energy vehicles, ultra-high power pulse systems, and next-generation information technology, the demand for superior energy storage devices is increasing. Among energy storage devices based on different principles, multilayer ceramic capacitors (MLCCs) stand out due to their superior performance advantages: ultra-high power density, ultra-fast charge and discharge rates, and ultra-long lifespan. The energy storage performance of MLCCs is limited by the intrinsic energy storage characteristics of the ceramic material. Existing ceramic materials have relatively low recyclable energy storage density (…). W rec ) and energy storage efficiency ( η This limitation restricts the application of multilayer ceramic capacitors. Therefore, there is an urgent need to develop new ceramic dielectrics to achieve breakthroughs in capacitor energy storage performance.

[0003] The energy storage performance of dielectric ceramic capacitors is typically evaluated based on their hysteresis loop (PE loop): .in, P m and P r These represent the maximum polarization intensity and the residual polarization intensity, respectively. Therefore, to obtain ceramic dielectrics with excellent energy storage performance, the core lies in achieving synergistic optimization of maximizing the maximum polarization intensity, minimizing the residual polarization intensity, and maximizing the breakdown strength.

[0004] To achieve this goal, developing relaxor ferroelectrics (RFEs) characterized by extremely fine hysteresis loops is currently the mainstream strategy. In recent years, numerous attempts have been made to optimize relaxor ferroelectrics, including polar nanodomain engineering, core-shell structure construction, superparaelectric design, polarization-strain coupled lattice engineering, defect engineering, and heterovalent doping. These methods have all been proven to improve the energy storage performance of dielectric ceramics, but the improvement is still relatively limited. Among these, high-entropy relaxor ferroelectric materials with multiple elements occupying equivalent lattice sites, due to their atomic-scale compositional heterogeneity, can induce significant local structural disorder, generating strong local random electric-stress fields. In recent years, they have shown great application potential in the energy storage field, and these characteristics are highly beneficial for improving energy storage performance. However, traditional high-entropy design approaches have certain limitations: when using the conventional A-site equimolar entropy-increasing strategy, although the increase in lattice disorder significantly improves energy storage efficiency, it often leads to a precipitous decrease in polarization intensity; on the other hand, in materials using the equimolar entropy-increasing strategy, the abnormal growth of electric field-induced polar nanodomains under extremely high electric fields can easily lead to premature polarization saturation, resulting in a decrease in breakdown field strength (E b The difficulty in making further breakthroughs has become a bottleneck restricting the improvement of the energy storage performance of MLCCs. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a non-equimolar entropy engineering method using two rare earth elements co-doped components. This method aims to construct locally heterogeneous microdomains and multi-state nanodomain structures, inducing heterogeneous distribution of chemical composition at the atomic scale. By constructing locally heterogeneous microdomains, high local polarization response activity is retained. Using this strategy, this invention provides a non-equimolar high-entropy relaxor ferroelectric ceramic, a multilayer capacitor, its preparation method, and its applications. The non-equimolar high-entropy relaxor ferroelectric ceramic (Bi...) 1 / 6Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 TiO3 (where M and N are selected from any two of La, Ce, Pr, Nd, Sm, and Eu) can reduce the remanent polarization intensity and enhance the breakdown resistance while maintaining a high maximum polarization intensity, thus achieving better performance in Bi... 1 / 6 Na 1 / 6 Ba 1 / 6Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 Ultra-high energy storage density and energy storage efficiency are achieved in TiO3 multilayer ceramic capacitors.

[0006] In a first aspect, the present invention provides a non-equimolar high-entropy relaxor ferroelectric ceramic, wherein the chemical composition of the non-equimolar high-entropy relaxor ferroelectric ceramic is: Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 TiO3, wherein M and N are selected from any two of La, Ce, Pr, Nd, Sm, and Eu; preferably, M is Nd and N is Sm.

[0007] Secondly, the present invention provides a method for preparing the above-mentioned non-equimolar high-entropy relaxor ferroelectric ceramic, comprising the following steps: (1) Using Bi2O3, NaCO3, BaCO3, SrCO3, K2CO3, M element oxides, N element oxides and TiO2 as raw materials, the raw materials are weighed and mixed according to the chemical composition of non-equimolar high-entropy relaxor ferroelectric ceramics, and ceramic powder is obtained after pre-firing treatment; (2) The obtained ceramic powder is finely ground and dried; (3) The finely ground ceramic powder is granulated and pressed into shape to obtain a ceramic body; (4) The obtained ceramic blank is sintered to obtain the non-equimolar high-entropy relaxor ferroelectric ceramic.

[0008] Preferably, in step (1), the mixing method is wet ball milling, and the parameters of wet ball milling include: the mass ratio of raw material powder: ball milling medium: solvent is 1: (4.0~5.0): (0.7~1.5), and the ball milling time is 6~12 hours.

[0009] Preferably, in step (1), the temperature of the pre-firing treatment is 800-950°C and the holding time is 2-6 hours; preferably, the heating rate is 2-5°C / minute.

[0010] Preferably, in step (2), the fine grinding method is wet ball milling, and the parameters of wet ball milling include: the mass ratio of ceramic powder: ball milling medium: solvent is 1: (4.0~5.0): (0.7~1.5), and the ball milling time is 10~24 hours.

[0011] Preferably, in step (3), the granulation process includes: mixing ceramic powder with a binder, then aging and sieving; the amount of binder added is 6-10 wt% of the ceramic powder; and the aging time is 23-26 hours.

[0012] Preferably, in step (4), the ceramic blank is debonded before sintering; the debonding temperature is 600-700℃ and the time is 2-6 hours; preferably, the ambient atmosphere is an air atmosphere.

[0013] Preferably, in step (4), the sintering temperature is 1050-1350°C and the holding time is 2-4 hours; preferably, the heating rate is 2-5°C / minute.

[0014] Thirdly, the present invention provides a multilayer capacitor comprising the above-described non-equimolar high-entropy relaxor ferroelectric ceramic or the non-equimolar high-entropy relaxor ferroelectric ceramic prepared by the above-described preparation method.

[0015] Fourthly, the present invention provides a method for preparing the above-mentioned multilayer capacitor, comprising the following steps: (1) The powder material of the above-mentioned non-equimolar high-entropy relaxor ferroelectric ceramic is mixed with solvent, binder, plasticizer and dispersant to obtain ceramic slurry; (2) The obtained ceramic slurry is cast into a film, the inner electrode is screen printed, and after stacking, isostatic pressing, debinding, sintering, and the outer electrode is drawn on, the multilayer capacitor is obtained.

[0016] Preferably, in step (1), the binder is selected from at least one of polyvinylpyrrolidone, sucrose, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the plasticizer is selected from at least one of polyethylene glycol and dioctyl phthalate; the solvent is selected from at least one of ethanol, methanol, acetone, ethyl acetate, butanone, and glycerol; and the dispersant is selected from at least one of phosphate ester, ethoxylated compound, trioleic acid glyceride, and AKM0531.

[0017] Preferably, in step (1), based on the total mass of the ceramic slurry as 100%, the content of non-equimolar high-entropy relaxor ferroelectric ceramic is 35% to 60%, the content of binder is 4.0% to 5.0%, the content of plasticizer is 1.65% to 1.95%, the content of dispersant is 0.2% to 0.4%, and the content of solvent is 32% to 58%.

[0018] Preferably, in step (2), the thickness of the cast film is 4 to 20 μm.

[0019] Preferably, in step (2), the material of the inner electrode and / or the outer electrode is selected from at least one of Pt, Ag / Pd, Cu, and Ni.

[0020] Preferably, in step (2), the temperature of the adhesive discharge is 300-500℃ and the holding time is 1-5 h; preferably, the heating rate is 0.5-1℃ / min and the ambient atmosphere is an oxygen atmosphere.

[0021] Preferably, in step (2), the sintering temperature is 1070-1150℃ and the holding time is 1-3 h; preferably, the heating rate is 2-4℃ / min and the ambient atmosphere is an oxygen atmosphere.

[0022] Preferably, the dielectric layer thickness of the resulting multilayer capacitor is 2–15 μm.

[0023] Fifthly, the present invention provides an application of the above-mentioned multilayer capacitor in dielectric energy storage. Beneficial effects

[0024] Compared with the prior art, the present invention has the following beneficial effects: The non-equimolar entropy engineering proposed in this invention, involving the co-doping of two rare earth elements, can maintain a high maximum polarization intensity while suppressing electric field-induced hysteresis and delaying saturation polarization. The Bi prepared in this invention... 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6M 1 / 12 N 1 / 12TiO3 bulk ceramics and MLCCs achieved J / cm² values ​​of 10.67 and 18.80 respectively. 3 With its ultra-high recyclable energy storage density and energy storage efficiency of 91.33% and 94.56%, it provides a device selection and strategy support with great application potential for the development of dielectric energy storage technology. Attached Figure Description

[0025] Figure 1 X-ray diffraction of the ceramic materials prepared in Example 1 and Comparative Examples 1-4 of this invention; Figure 2 The following are performance test diagrams of the ceramic materials and their multilayer capacitors prepared in Examples 1-2 and Comparative Examples 1-4 of the present invention; wherein, (a) is the unipolar hysteresis loop of the ceramic materials and their multilayer capacitors prepared in Examples 1-2 and Comparative Examples 1-4, and (b) is the releasable energy storage density and energy storage efficiency of the ceramic materials and their multilayer capacitors prepared in Examples 1-2 and Comparative Examples 1-4. Figure 3 The following are performance test diagrams of the multilayer capacitor prepared in Example 2 of the present invention; wherein, (a) is the unipolar hysteresis curve under varying temperature, (b) is the releaseable energy density and energy storage efficiency under varying temperature, (c) is the unipolar hysteresis curve under varying frequency, (d) is the releaseable energy density and energy storage efficiency under varying frequency, (e) is the unipolar hysteresis curve under different cycle numbers, and (f) is the releaseable energy density and energy storage efficiency under different cycle numbers; Figure 4 shows the actual charge and discharge performance of the multilayer capacitor prepared in Example 2 of the present invention under underdamped and overdamped conditions; wherein, (a) is the charge and discharge current curve under different electric fields under underdamped conditions, (b) is the discharge current density and power density under underdamped conditions with the change of electric field, (c) is the charge and discharge current curve under different electric fields under overdamped conditions, and (d) is the discharge energy density under different electric fields under overdamped conditions with the change of time. Detailed Implementation

[0026] To further illustrate the invention's content, features, and practical effects, the invention will be described in detail below with reference to embodiments. It should be noted that the modification methods of the invention are not limited to these specific implementation methods. Equivalent substitutions and modifications made by those skilled in the art based on their reading of the invention's content, without departing from the spirit and essence of the invention, are also within the scope of protection claimed by this invention.

[0027] First, this invention provides a non-equimolar high-entropy relaxor ferroelectric ceramic, wherein the chemical composition of the ultra-high remanent polarization intensity and low-loss BNT-based ferroelectric ceramic is: Bi 1 / 6 Na 1 / 6 Ba1 / 6 Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 TiO3, wherein M and N are selected from any two of La, Ce, Pr, Nd, Sm, and Eu; preferably, M is Nd and N is Sm. This invention employs non-equimolar configuration entropy engineering with dual rare earth co-doping to achieve Bi... 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 12 Sm 1 / 12 The synergistic optimization of polarization intensity and breakdown strength of TiO3 bulk ceramics led to the fabrication of multilayer capacitors with a recyclable energy storage density of 18.80 J / cm³ and an energy storage efficiency of 94.56%, exhibiting excellent temperature and frequency stability, fatigue resistance, and fast charge / discharge performance. This invention provides a new strategy for the development of high-energy-storage dielectric ceramics and their multilayer capacitors, showing significant application potential in new energy, pulsed power systems, and other fields.

[0028] This invention addresses the inherent bottlenecks of traditional equimolar high-entropy relaxor ferroelectric ceramics, such as the decrease in maximum polarization, premature polarization saturation, and limited breakdown strength. It innovatively proposes a stepwise non-equimolar configuration entropy engineering method combined with Nd... 3+ 、Sm 3+ Dual rare earth co-doping strategy to construct Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 12 Sm 1 / 12 The TiO3 non-equimolar A-site occupancy system achieves breakthroughs in energy storage performance through multi-dimensional synergy. By employing a non-equimolar occupancy design, the two rare earth elements act as asymmetric perturbation centers, inducing atomic-scale chemical heterogeneity. This retains high spontaneous polarization while inducing local structural distortion through ionic radius gradients, resulting in a composite structure where vortex domains coexist with rhombohedral, tetragonal, and cubic polymorphic nanodomains. This lowers the domain flipping energy barrier, enhancing maximum polarization, and achieves extremely low residual polarization through the vortex domain flux closure effect. Simultaneously, the differentiated electric field response of different domains significantly delays polarization saturation. The coexistence of multivalent cations also pins domain walls, inhibiting the merging and growth of polar nanodomains under strong fields. Combined with configuration entropy-induced grain refinement, resistivity enhancement, and Ti-O bond strength strengthening, this significantly improves breakdown strength. The resulting multilayer ceramic capacitor achieves ultra-high recoverable energy density and excellent efficiency, while also exhibiting ultra-wide temperature and frequency stability and ultra-fast charge and discharge capabilities, providing a new design paradigm for next-generation high-performance lead-free energy storage devices.

[0029] The following exemplifies the preparation method of non-equimolar high-entropy relaxor ferroelectric ceramics provided by the present invention.

[0030] Using Bi2O3, NaCO3, BaCO3, SrCO3, K2CO3, M element oxides, N element oxides and TiO2 as raw materials, the raw materials are weighed and mixed according to the chemical composition of non-equimolar high-entropy relaxor ferroelectric ceramics, and then pre-fired to obtain ceramic powder.

[0031] In an optional embodiment, the mixing method is wet ball milling, and the parameters of wet ball milling include: the mass ratio of raw material powder: ball milling medium: solvent can be 1: (4.0~5.0): (0.7~1.5), and the ball milling time can be 6~12 hours.

[0032] In an optional embodiment, the pre-firing treatment temperature is 800-950°C, and the holding time is 2-6 hours; preferably, the heating rate is 2-5°C / minute.

[0033] The obtained ceramic powder is finely ground and dried. The fine grinding method is wet ball milling, and the parameters of wet ball milling include: the mass ratio of ceramic powder: milling medium: solvent can be 1:(4.0~5.0):(0.7~1.5), and the ball milling time can be 10~24 hours.

[0034] Finely ground ceramic powder is granulated and pressed into shape to obtain a ceramic green body.

[0035] In an optional embodiment, the granulation process includes: mixing ceramic powder with a binder, followed by aging and sieving; the amount of binder added is 6-10 wt% of the mixed powder; the aging time can be 23-26 hours.

[0036] The obtained ceramic blank was debinded and then sintered to obtain non-equimolar high-entropy relaxor ferroelectric ceramic.

[0037] In an optional embodiment, the temperature for discharging the adhesive can be 600–700°C, and the time can be 2–6 hours; preferably, the ambient atmosphere can be air. The sintering temperature can be 1070–1350°C, and the holding time can be 2–4 hours; preferably, the heating rate can be 2–5°C / minute.

[0038] The following exemplarily illustrates the method for fabricating a multilayer capacitor provided by the present invention.

[0039] The powder material of the above-mentioned non-equimolar high-entropy relaxor ferroelectric ceramic is stirred and finely ground, and then mixed with solvent, binder, plasticizer and dispersant to obtain ceramic slurry.

[0040] In an optional embodiment, the parameters for fine grinding in the stirred mill include: powder material: milling media: alcohol = 1:(8-12):(1.0-2.5), rotation speed of 400-600 rpm, milling media being zirconium balls with a diameter of 0.9-1.2 mm, and grinding time of 3-6 h. After stirred grinding, the average particle size of the non-equimolar high-entropy relaxor ferroelectric ceramic powder material is 3-4.5 μm.

[0041] In an optional embodiment, the binder is selected from at least one of polyvinylpyrrolidone, sucrose, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB); the plasticizer is selected from at least one of polyethylene glycol and dioctyl phthalate; the solvent is selected from at least one of ethanol, methanol, acetone, ethyl acetate, butanone, and glycerol; and the dispersant is selected from at least one of phosphate esters, ethoxylated compounds, trioleic acid esters, and AKM0531. Based on 100% of the total mass of the ceramic slurry, the content of non-equimolar high-entropy relaxor ferroelectric ceramics is 35%–60%, the binder content is 4.0%–5.0%, the plasticizer content is 1.65%–1.95%, the dispersant content is 0.2%–0.4%, and the solvent content is 32%–58%.

[0042] A multilayer capacitor is obtained by casting ceramic slurry into a film, screen printing inner electrodes, stacking, isostatic pressing, debinding, sintering, and then attaching outer electrodes.

[0043] In an alternative embodiment, the thickness of the cast film can be 4–20 μm.

[0044] In an optional embodiment, the material of the inner electrode and / or the outer electrode is selected from at least one of Pt, Ag / Pd, Cu, and Ni.

[0045] In an optional embodiment, the isostatic pressing temperature is 60–80°C, and the pressure is 60–70 MPa. The binder discharge temperature is 300–500°C, and the holding time is 1–5 h; preferably, the heating rate is 0.5–1°C / min, and the ambient atmosphere is an oxygen atmosphere. The sintering temperature is 1070–1150°C, and the holding time is 1–3 h; preferably, the heating rate is 2–4°C / min, and the ambient atmosphere is an oxygen atmosphere.

[0046] The obtained multilayer capacitor is subjected to polarization treatment. The polarization treatment is carried out at room temperature and under an electric field of 4.0 to 10.0 kV / mm for 10 to 40 minutes.

[0047] The dielectric layer thickness of the multilayer capacitor prepared by the above method is 2 to 15 μm.

[0048] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Example 1

[0049] The non-equimolar high-entropy relaxor ferroelectric ceramic (Bi) provided in Example 1 of this embodiment is... 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 12 Sm 1 / 12 The preparation method of TiO3 includes the following steps: (1) Using Bi2O3, NaCO3, BaCO3, SrCO3, K2CO3, Nd2O3, Sm2O3, and TiO2 as raw materials, according to the chemical composition of non-equimolar high-entropy relaxor ferroelectric ceramics, Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 12 Sm 1 / 12 TiO3 raw materials were weighed and mixed for 12 hours according to the mass ratio of raw materials: spheres: anhydrous ethanol = 1: 4.0: 1.5. Then, the mixture was dried, pressed into blocks, and pre-fired in an oxygen atmosphere at a heating rate of 3℃ / min to 850℃ and held for 2 hours to obtain ceramic powder. (2) The obtained ceramic powder was finely ground by wet ball milling for 12 hours and dried. Then, PVA binder (7 wt% of the ceramic powder mass) was added to it for granulation, aged for 24 hours, and passed through a 60-mesh sieve. Then, it was pressed into a circular sheet with a diameter of 13 mm and a thickness of 2 mm. Then, it was heated to 650°C in the air and the binder was removed for 2 hours to obtain the ceramic body. (3) Place the ceramic blank in the crucible, cover the crucible, and heat it to 1000℃ in the air at a heating rate of 3℃ / min, then heat it to 1260℃ at a heating rate of 2℃ / min, hold it for 2 hours, and cool it with the furnace to obtain non-equimolar high-entropy relaxor ferroelectric ceramic. (4) The obtained ceramic material is ground into a ceramic sheet with a thickness of 30 μm, and after cleaning, drying and sputtering gold electrodes, a non-equimolar high-entropy relaxor ferroelectric ceramic device is obtained. Example 2

[0050] This embodiment 2 provides a process for preparing a non-equimolar high-entropy relaxor ferroelectric ceramic multilayer capacitor, including the following steps: (1) Using Bi2O3, NaCO3, BaCO3, SrCO3, K2CO3, Nd2O3, Sm2O3, and TiO2 as raw materials, according to the chemical composition of non-equimolar high-entropy relaxor ferroelectric ceramics, Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 12 Sm 1 / 12 TiO3 raw materials were weighed and mixed for 12 hours according to the mass ratio of raw materials: spheres: anhydrous ethanol = 1: 4.0: 1.5. Then, the mixture was dried, pressed into blocks, and pre-fired in an oxygen atmosphere at a heating rate of 3℃ / min to 850℃ and held for 2 hours to obtain ceramic powder. (2) The obtained ceramic powder was finely ground by wet ball milling with zirconium balls as the ball milling medium. The mass ratio of powder: ball milling medium: alcohol was 1:10:2, the speed was 500 r / min, and the grinding time was 4 hours. (3) Finely ground ceramic powder (40 wt%), a mixed solvent of alcohol and ethyl acetate (mass ratio of alcohol to ethyl acetate is 1:2.15, 53.9 wt%), and dispersant AKM0531 (0.3 wt%) were ball-milled and mixed for 4 h. Then, binder polyvinyl butyral (PVB) (4.0 wt%) and plasticizer dioctyl phthalate (DOP) (1.8 wt%) were added and ball-milled and mixed for 4 h to obtain ceramic slurry; (4) After vacuum degassing of the ceramic slurry, it is cast into a film (7 μm thick), screen printed with Ag / Pd internal electrodes, stacked, and then subjected to warm isostatic pressing (65MPa / 75℃). It is then cut into small pieces; and then heated to 330℃ in air atmosphere and held for 5 hours to remove the binder, thus obtaining a multilayer ceramic body. (5) Place the multilayer ceramic blank into an alumina crucible, cover the blank with ceramic powder having the same composition as in step (1), cover with a ground glass plate, raise the temperature to 1260°C at a heating rate of 2°C / min, and hold for 3 hours to obtain multilayer ceramic. (6) The two ends of the multilayer ceramic were coated with silver, and the temperature was raised to 700°C at a heating rate of 2°C / min. The temperature was held for 0.5 hours to obtain a non-equimolar high-entropy relaxor ferroelectric ceramic multilayer capacitor with a dielectric layer thickness of 4.5 μm. Comparative Example 1

[0051] The preparation process of the ferroelectric ceramic in Comparative Example 1 is the same as in Example 1, except that the chemical composition of the ferroelectric ceramic is Bi. 0.5 Na 0.5 TiO3, sintering temperature 1080℃. Comparative Example 2

[0052] The preparation process of the ferroelectric ceramic in Comparative Example 2 is the same as that in Example 1, except that in step (3), the chemical composition is Bi. 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 Nd 1 / 6 TiO3, sintering temperature 1200℃. Comparative Example 3

[0053] The preparation process of the ferroelectric ceramic in Comparative Example 3 is the same as that in Example 1, except that in step (3), the chemical composition is Bi. 1 / 5 Na 1 / 5 Sr 1 / 5 K 1 / 5 Nd 1 / 5 TiO3, sintering temperature 1180℃. Comparative Example 4

[0054] The preparation process of the ferroelectric ceramic in Comparative Example 4 is the same as that in Example 1, except that in step (3), the chemical composition is Bi. 1 / 3 Na 1 / 3 Sr 1 / 3 TiO3, sintering temperature 1180℃.

[0055] Figure 1 The figures show X-ray diffraction patterns of the ceramic materials prepared in Example 1 and Comparative Examples 1-4 of this invention. As can be seen from the figures, the relaxor ferroelectric ceramics prepared using the method provided by this invention are all free of impurities.

[0056] Figure 2 The figures show the releasable energy storage density and energy storage efficiency of the ceramic materials and their multilayer capacitors prepared in Examples 1-2 and Comparative Examples 1-4 of this invention. As can be seen from the figures, the ceramic materials and their multilayer capacitors prepared using the method provided by this invention exhibit excellent energy storage performance, significantly exceeding that of the comparative examples.

[0057] Figure 3 The figure shows the release density and energy storage efficiency of the multilayer capacitor prepared in Example 2 under varying temperature, frequency, and cycle counts. As can be seen from the figure, the multilayer capacitor prepared using the method provided by this invention exhibits excellent temperature and frequency stability and fatigue resistance. Over a wide temperature range from -150℃ to 150℃, W... recThe values ​​of W and η show relatively small changes relative to room temperature, remaining within the ranges of 15.32 ± 0.95 J / cm³ and 93.91 ± 3.27%, respectively. Within the 10–200 Hz range, W... rec η and η remain above 15.04 J / cm³ and 93.10%, respectively. Meanwhile, the capacitor undergoes 10... 6 After one cycle, the recoverable energy storage density and energy efficiency fluctuated slightly, changing from 15.32 J / cm³ to 15.09 J / cm³ and from 93.91% to 94.33%, respectively.

[0058] Figure 4 shows the actual charge and discharge performance of the multilayer capacitor prepared in Example 2 of this invention under underdamped and overdamped conditions. As shown in the figure, at 800 kV / cm, the discharge current density and power density of the capacitor in the underdamped state are 372.25 A / cm² and 147.89 MW / cm³, respectively; under the overdamped condition with a 300 Ω resistance, the discharge power density reaches 7.23 J / cm³. 3 .

[0059] Table 1 lists the release energy density and energy storage efficiency of the relaxor ferroelectric ceramic or multilayer capacitors prepared in Examples 1-2 and Comparative Examples 1-4.

[0060] Table 1: .

[0061] In summary, the relaxor ferroelectric ceramics and their multilayer capacitors prepared by this invention achieve ultra-high energy storage density and energy storage efficiency through non-equimolar high-entropy engineering with co-doping of two rare earth elements, providing device selection and strategy support with great application potential for the development of dielectric energy storage technology.

[0062] The above description represents only some preferred embodiments of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content and spirit of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A non-equimolar high-entropy relaxor ferroelectric ceramic, characterized in that, The chemical composition of the non-equimolar high-entropy relaxor ferroelectric ceramic is: Bi 1 / 6 Na 1 / 6 Ba 1 / 6 Sr 1 / 6 K 1 / 6 M 1 / 12 N 1 / 12 TiO3, wherein M and N are selected from any two of La, Ce, Pr, Nd, Sm, and Eu; preferably, M is Nd and N is Sm.

2. A method for preparing a non-equimolar high-entropy relaxor ferroelectric ceramic according to claim 1, characterized in that, Includes the following steps: (1) Using Bi2O3, NaCO3, BaCO3, SrCO3, K2CO3, M element oxides, N element oxides and TiO2 as raw materials, the raw materials are weighed and mixed according to the chemical composition of non-equimolar high-entropy relaxor ferroelectric ceramics, and ceramic powder is obtained after pre-firing treatment; (2) The obtained ceramic powder is finely ground and dried; (3) The finely ground ceramic powder is granulated and pressed into shape to obtain a ceramic body; (4) The obtained ceramic blank is sintered to obtain the non-equimolar high-entropy relaxor ferroelectric ceramic.

3. The preparation method according to claim 2, characterized in that, In step (1), the temperature of the pre-firing treatment is 800-950°C and the holding time is 2-6 hours; preferably, the heating rate is 2-5°C / minute.

4. The preparation method according to claim 2 or 3, characterized in that, In step (2), the fine grinding method is wet ball milling. The parameters of wet ball milling include: the mass ratio of ceramic powder: ball milling medium: solvent is 1:(4.0~5.0):(0.7~1.5), and the ball milling time is 10~24 hours.

5. The preparation method according to any one of claims 2-4, characterized in that, In step (3), the granulation process includes: mixing ceramic powder with binder, then aging and sieving; the amount of binder added is 6-10 wt% of the ceramic powder; the aging time is 23-26 hours.

6. The preparation method according to any one of claims 2-5, characterized in that, In step (4), the ceramic blank is debinded before sintering; the debinding temperature is 600-700℃ and the time is 2-6 hours; preferably, the ambient atmosphere is an air atmosphere. The sintering temperature is 1050–1350°C, and the holding time is 2–4 hours; preferably, the heating rate is 2–5°C / minute.

7. A multilayer capacitor, characterized in that, This includes the non-equimolar high-entropy relaxor ferroelectric ceramic as described in claim 1 or the non-equimolar high-entropy relaxor ferroelectric ceramic prepared by the preparation method described in any one of claims 2-6.

8. A method for preparing a multilayer capacitor according to claim 7, characterized in that, Includes the following steps: (1) Mix the powder material of non-equimolar high-entropy relaxor ferroelectric ceramics with solvent, binder, plasticizer and dispersant to obtain ceramic slurry; (2) The obtained ceramic slurry is cast into a film, the inner electrode is screen printed, and after stacking, isostatic pressing, debinding, sintering, and the outer electrode is drawn on, the multilayer capacitor is obtained.

9. The preparation method according to claim 8, characterized in that, In step (2), the temperature of the adhesive discharge is 300-500℃, and the heat preservation time is 1-5 h; preferably, the heating rate is 0.5-1℃ / min, and the ambient atmosphere is an oxygen atmosphere. The sintering temperature is 1070–1150°C, and the holding time is 1–3 h; preferably, the heating rate is 2–4°C / min, and the ambient atmosphere is an oxygen atmosphere.

10. An application of the multilayer capacitor according to claim 7 in dielectric energy storage.

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