Relaxation type bismuth layered structure ceramic with high energy storage characteristic as well as preparation method and application of relaxation type bismuth layered structure ceramic

Abstract

The invention relates to relaxation type bismuth lamellar structure ceramic with high energy storage characteristic as well as a preparation method and application of the relaxation type bismuth lamellar structure ceramic. The chemical composition of the relaxation type bismuth layered structure ceramic with the high energy storage characteristic is Bi (4-x) LaxTi3O12, wherein x is more than or equal to 1.10 and less than or equal to 1.40. The relaxation type bismuth layered structure ceramic with the high energy storage characteristic is successfully designed by introducing a specific content of La element into Bi4Ti3O12, and the relaxation type bismuth layered structure ceramic has the advantages of high breakdown field strength, high energy storage density and high efficiency. The recoverable energy storage density of the relaxation type bismuth layered structure ceramic with the high energy storage characteristic is 5.9-11.2 J / cm < 3 >, the energy storage efficiency is 72.8-88.1%, and the breakdown electric field is 725-912 kV / cm.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional ceramics, and relates to a high-energy-storage-property relaxor-type bismuth layer-structured ceramic as well as a preparation method and application thereof. BACKGROUND

[0002] Dielectric capacitors are widely used in the fields of power electronics, aerospace, radar communication and the like due to their extremely high output power density (10 2 ~ 10 7 W / kg), superfast charging and discharging rate (~ 10 1 ns) and excellent temperature stability. In recent years, with the gradual popularization of various new energy technologies such as portable electronic products, electric vehicles and pulse power technologies, the demand for capacitors with high energy storage density, high working temperature, high working voltage and excellent temperature stability is gradually increasing. In order to meet the use requirements in the above-mentioned fields, it is urgent to develop new dielectric ceramics with excellent energy storage properties to meet the actual needs of advanced pulse power capacitors. The energy storage ceramics reported at present are mostly of perovskite structure, but their breakdown field strength is low, which limits the realization of higher energy storage properties, so it is of important practical significance to develop new energy storage ceramic materials.

[0003] Bismuth layer-structured ferroelectrics (BLSFs) are considered as an ideal energy storage dielectric ceramic material due to their natural high breakdown field strength and excellent temperature stability. The general structure formula of bismuth layer-structured ferroelectrics is (Bi2O2) 2+ (A m- 1B m O 3m+1 ) 2- , wherein m is the number of BO6 octahedral layers containing A-site cations in the perovskite-like layer, and the crystal structure is that the perovskite-like layer (A m-1 B m O 3m+1 ) 2- is sandwiched between two (Bi2O2) 2+ layers. In bismuth layer-structured ferroelectrics, Na + , Sr 2+ , Ca 2+ , La 3+ and the like have larger ionic radius and lower valence cations occupying the A site, and B-site ions are generally W 6+ , Ta 5+ , Nb 5+ , Ti 4 + and the like have smaller ionic radius and higher valence metal cations.

[0004] For bismuth layer-structured ferroelectrics, the perovskite-like layer and (Bi2O2) 2+The layers are symbiotic, requiring higher structural stability; too many perovskite layers or (Bi2O2) 2+ Excessive layer distortion can easily cause the collapse of the entire bismuth layered structure. Therefore, current reports on bismuth layered ceramic energy storage focus on the modification of the perovskite-like layer through elemental doping, such as Sr. 0.5 Ni 0.5 Bi2NbTaO9(W rec =2.42J / cm -3 andη=80.8%)(PhysicaB.621(2021)413318), and perovskite layer number regulation, such as Ba2Bi4Ti5O 18 (W rec =1.16J / cm -3 (andη=87.2%) (Adv.Eng.Mater.25(2023)2201677), achieving excellent energy storage characteristics. However, the (Bi2O2) in the bismuth layered structure... 2+ The layers inhibit the relaxation behavior of the material, thus limiting the improvement of the energy storage properties of bismuth layered ferroelectric materials. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a relaxor-type bismuth layered ceramic with high energy storage properties, its preparation method, and its applications. Considering the similarity in ionic radius and valence state between rare earth ions and Bi ions, this invention successfully designs a relaxor-type bismuth layered ceramic with high energy storage properties based on bismuth titanate ceramics, exhibiting advantages such as high breakdown field strength, high energy storage density, and high efficiency.

[0006] In a first aspect, the present invention provides a high-energy-storage-performance relaxor-type bismuth layered structure ceramic, wherein the chemical composition of the high-energy-storage-performance relaxor-type bismuth layered structure ceramic is Bi. 4-x La x Ti3O 12 , where 1.10≤x≤1.40.

[0007] In this invention, by using Bi4Ti3O 12 Introducing a certain amount of La element, La 3+ When the ion content is greater than 1, it will preferentially enter (Bi2O2). 2+ The Bi sites in the layer cause (Bi2O2). 2+ Layer distortion causes local structural heterogeneity, reduces the size of ferroelectric domains, and promotes induced relaxation behavior and reduces residual polarization. The resulting high-energy-storage-performance relaxor bismuth layered ceramic material has the characteristics of high saturation polarization intensity, low residual polarization intensity, high breakdown strength, high energy storage density and efficiency.

[0008] Ideally, x = 1.2.

[0009] Preferably, the recyclable energy storage density of the high-energy-storage-performance relaxor bismuth layered ceramic is 5.9–11.2 J / cm³. 3 ; The energy storage efficiency of the high-energy-storage-characteristic relaxor bismuth layered ceramic is 72.8–88.1%. The breakdown electric field of the high-energy-storage-characteristic relaxor bismuth layered ceramic is 725–912 kV / cm.

[0010] Secondly, the present invention provides a method for preparing the above-mentioned high-energy-storage-characteristic relaxor-type bismuth layered structure ceramic, comprising the following steps: (1) Weigh out titanium source, bismuth source and lanthanum source according to the stoichiometric ratio of high energy storage relaxation type bismuth layered structure ceramic and mix them. After calcination, ceramic powder is obtained. (2) The ceramic powder is mixed with the binder and granulated, then sieved and molded to obtain a ceramic green body; (3) The ceramic green body is subjected to plasticizing and sintering to obtain the high energy storage characteristic relaxor bismuth layered structure ceramic.

[0011] Preferably, in step (1), the titanium source is titanium dioxide powder; the bismuth source is bismuth oxide powder; and the lanthanum source is lanthanum oxide powder.

[0012] Preferably, in step (1), the mixing method is ball milling; the parameters of the ball milling include: the ball milling medium is anhydrous ethanol, the grinding balls are zirconia balls and zirconia columns, the ball milling speed is 240-260 r / min, and the ball milling time is 5-6 h.

[0013] Preferably, in step (1), the calcination temperature is 800-1050°C and the time is 2-3 hours.

[0014] Preferably, in step (2), the binder is a polyvinyl alcohol aqueous solution with a concentration of 6-7 wt.%; the amount of binder added is 6-7 wt% of the ceramic powder mass.

[0015] Preferably, in step (2), the mesh size of the sieve is 40 to 80 mesh, preferably 40 mesh; The compression molding pressure is 1.5 to 5 MPa.

[0016] Preferably, in step (3), the temperature of the plastic discharge is 600-750℃ and the time is 2-3h; more preferably, the heating rate of the plastic discharge is 1-2℃ / min; more preferably, the temperature of the plastic discharge is 650℃, the time is 2h, and the heating rate is 2℃ / min.

[0017] Preferably, in step (3), the sintering temperature is 1100-1150℃ and the time is 2-4h; preferably, the sintering heating rate is 1-3℃ / min; more preferably, the sintering heating rate is 2℃ / min.

[0018] Thirdly, the present invention provides an energy storage ceramic element, comprising: the above-mentioned high-energy-storage-characteristic relaxor bismuth layered structure ceramic, and electrodes distributed on the surface of the high-energy-storage-characteristic relaxor bismuth layered structure ceramic.

[0019] Fourthly, this invention provides an application of a high-energy-storage-characteristic relaxor bismuth layered structure ceramic in multilayer ceramic capacitors.

[0020] Beneficial effects: In this invention, by introducing a specific amount of La element, some La... 3+ Ions enter (Bi2O2) 2+ The layer causes (Bi2O2) to form. 2+ Layer distortion induces relaxation behavior, altering the electrical properties of high-energy-storage-capability relaxable bismuth layered ceramics. This invention, for the first time, achieves strong relaxation behavior in bismuth layered ferroelectrics through La doping. The resulting high-energy-storage-capability relaxable bismuth layered ceramic material exhibits high saturation polarization, low remanent polarization, high breakdown strength, high energy density, and high efficiency. The recyclable energy density of this high-energy-storage-capability relaxable bismuth layered ceramic is 5.9–11.2 J / cm³. 3 The energy storage efficiency is 72.8–88.1%, and the breakdown electric field is 725–912 kV / cm. Moreover, the preparation process of this invention is simple, it can work in extreme environments, and it is suitable for the preparation and application of multilayer ceramic capacitors. Attached Figure Description

[0021] Figure 1 These are X-ray diffraction patterns of the bismuth layered structure relaxor ceramics in Examples 1-3; Figure 2 This is a microscopic morphology image of the bismuth layered structure relaxor ceramic in Example 1; Figure 3 This is a microscopic morphology image of the bismuth layered structure relaxor ceramic in Example 2; Figure 4 This is a microscopic morphology image of the surface of the bismuth layered structure relaxor ceramic in Example 3; Figure 5 These are unipolar hysteresis loop diagrams of the bismuth layered structure relaxor ceramics in Examples 1-3; Figure 6 These are bipolar hysteresis loop diagrams of the bismuth layered structure relaxor ceramics in Examples 1-3; Figure 7This is the dielectric temperature spectrum of the bismuth layered relaxation ceramic in Example 1; Figure 8 This is the dielectric temperature spectrum of the bismuth layered relaxation ceramic in Example 2; Figure 9 This is the dielectric temperature spectrum of the bismuth layered relaxation ceramic in Example 3; Figure 10 This is a unipolar hysteresis loop diagram of the bismuth layered ceramics in Comparative Examples 1-4; Figure 11 This is a microscopic image of the surface morphology of the bismuth layered ceramic in Comparative Example 5. Figure 12 This is a microscopic morphology diagram of the surface of the bismuth layered ceramic in Comparative Example 6. Detailed Implementation

[0022] 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.

[0023] First, this invention provides a high-energy-storage-performance relaxor-type bismuth layered ceramic, the chemical composition of which is Bi. 4-x La x Ti3O 12 Where 1.10 ≤ x ≤ 1.40. Specifically, x can be any one of, but not limited to, 1.10, 1.20, 1.30, and 1.40, or any range between any two. When x < 1.10, La mainly enters the A-sites of the bismuth layered perovskite-like layer. Under this condition, although ion doping increases the local disorder of the material, (Bi₂O₂) 2+ The layer exerts compressive stress on the material, which effectively restricts its relaxation characteristics, preventing it from exhibiting relaxation behavior and maintaining stable ferroelectricity, resulting in poor energy storage performance. When x > 1.40, the material gradually transforms into a linear dielectric. During this process, the material's relaxation characteristics become excessively strong, leading to a significant reduction in polarization. Although it maintains a relatively high overall energy storage efficiency, the excessively low polarization directly causes a substantial decrease in energy density. In summary, at this point, the material's energy storage efficiency and energy density cannot achieve effective synergy, ultimately exhibiting poor energy storage performance.

[0024] In this invention, by using Bi4Ti3O 12The introduction of a specific amount of La element induced a relaxor-type bismuth layered ceramic with high energy storage properties. During La doping, the occupancy of La sites changes. When x is less than 1.1, La mainly enters the A-sites of the perovskite-like layer, greatly promoting relaxation, but does not reach (Bi₂O₂). 2+ Layer, relaxation behavior is affected by (Bi2O2) 2+ Layer suppression does not exhibit a long hysteresis loop, resulting in poor energy storage characteristics. However, when x > 1.1, it forces a very small amount of La... 3+ Entering (Bi2O2) 2+ Layer, (Bi2O2) 2+ Bi in the layer 3+ The material is replaced, resulting in a certain degree of distortion. This distortion is controlled within a certain range, maintaining structural stability while mitigating the effects of (Bi2O2). 2+ The compressive stress exerted by the layer on the perovskite-like material weakens its inhibitory effect on relaxation behavior, releasing the previously induced relaxation behavior and thus exhibiting high energy storage characteristics. Therefore, this characteristic is only achieved with a specific amount of La doping.

[0025] Furthermore, the present invention also provides a method for preparing the above-mentioned relaxor-type bismuth layered structure ceramic with high energy storage characteristics. The preparation method of the relaxor-type bismuth layered structure ceramic with high energy storage characteristics is illustrated below by way of example.

[0026] Titanium dioxide powder, bismuth oxide powder, and lanthanum oxide powder were weighed according to the stoichiometric ratio of a high-energy-storage-characteristic relaxable bismuth layered structure ceramic and mixed. The mixture was then calcined to obtain ceramic powder.

[0027] In an optional embodiment, the mixing method is ball milling; the parameters of the ball milling include: the milling medium is anhydrous ethanol, the milling balls are zirconia balls and zirconia columns, the milling speed is 240-260 r / min, and the milling time is 5-6 h. Preferably, the particle size of the zirconia balls is 6 mm, the size of the zirconia columns is 10 mm in diameter × 10 mm in height, and the number of zirconia balls and zirconia columns in the milling ball is equal; the milling speed can be, for example, but not limited to, any one or any two of 240 r / min, 250 r / min, and 260 r / min; the milling time can be, for example, but not limited to, any one or any two of 5 h, 5.5 h, and 6 h.

[0028] In an optional embodiment, the calcination temperature is 800–1050°C, and the time is 2–3 hours. Specifically, the calcination temperature can be, for example, but not limited to, any one or a range between any two of 800°C, 850°C, 900°C, 950°C, 1000°C, and 1050°C, and the calcination time can be any one or a range between any two of 2 hours, 2 hours and 15 minutes, 2 hours and 30 minutes, 2 hours and 45 minutes, and 3 hours.

[0029] The ceramic powder is mixed with a binder and granulated, then sieved and molded to obtain a ceramic green body.

[0030] In an optional embodiment, the binder is a 6-7 wt.% aqueous solution of polyvinyl alcohol; the amount of binder added is 6-7 wt% of the ceramic powder mass. The sieve mesh size is 40-80 mesh, preferably 40 mesh. The molding pressure is 1.5-5 MPa.

[0031] The ceramic green body is subjected to plasticizing and sintering to obtain the bismuth layered structure ceramic.

[0032] In an optional embodiment, the temperature for plastic removal is 600–750°C, and the time is 2–3 hours; the heating rate for plastic removal is 1–2°C / min; preferably, the temperature for plastic removal is 650°C, the time is 2 hours, and the heating rate is 2°C / min.

[0033] In an optional embodiment, the sintering temperature is 1100–1150°C, and the time is 2–4 hours; preferably, the sintering heating rate is 1–3°C / min; more preferably, the sintering heating rate is 2°C / min. The sintering temperature is one of the most critical parameters in the preparation method of this invention, directly determining the degree of densification and phase purity of the bismuth layered structure. If the temperature is too low, insufficient densification of the green body will result in a large number of pores, leading to increased dielectric loss and decreased breakdown field strength, making it impossible to achieve high energy density. If the temperature is too high, it will cause Bi element volatilization, destroying the integrity of the (Bi₂O₂)²⁺ layer, resulting in a reduction of relaxor active sites, and even the formation of impurities such as pyrochlore, losing relaxation properties. This invention controls the sintering temperature within the range of 1100–1150°C, which can simultaneously ensure high density and a pure bismuth layered phase. The holding time needs to be matched with the sintering temperature and controlled to be 2–4 hours. Too short a holding time leads to uneven grain growth, with unreacted raw material particles in some areas, affecting polarization uniformity; too long a holding time leads to excessive grain growth (e.g., grain size > 5 μm), reducing the number of grain boundaries, hindering domain wall movement during relaxation, and lowering energy storage efficiency. The superior ceramic performance of this invention depends on the high density of the sintered ceramic. Therefore, both the sintering temperature and holding time must be within the aforementioned range to obtain a relaxor-type bismuth layered ceramic with high energy storage characteristics.

[0034] In this invention, the hysteresis loop of the bismuth layered ceramic with high energy storage characteristics was tested using a TFAnalyzer 2000E ferroelectric analyzer. The recoverable energy storage density of the bismuth layered ceramic with high energy storage characteristics was also tested using the TFAnalyzer 2000E ferroelectric analyzer. The energy storage efficiency of the bismuth layered ceramic with high energy storage characteristics was further tested using the TFAnalyzer 2000E ferroelectric analyzer. Finally, the breakdown electric field of the bismuth layered ceramic with high energy storage characteristics was also tested using the TFAnalyzer 2000E ferroelectric analyzer.

[0035] The high-energy-storage-performance relaxor-type bismuth layered ceramic prepared by this invention has a recyclable energy storage density of 5.9–11.2 J / cm³. 3 The energy storage efficiency of the high-energy-storage-characteristic relaxor bismuth layered structure ceramic is 72.8–88.1%; the breakdown electric field of the high-energy-storage-characteristic relaxor bismuth layered structure ceramic is 725–912 kV / cm.

[0036] The high-energy-storage-performance relaxor-type bismuth layered ceramic prepared by this invention exhibits excellent relaxation properties and achieves a strength of 11.2 J / cm³. 3 With its high energy density and 88.1% energy storage efficiency, it is expected to be applied in pulse power capacitor devices.

[0037] 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.

[0038] Example 1

[0039] The chemical composition of the high-energy-storage-performance relaxor bismuth layered ceramic in Example 1 is Bi. 4-x La x Ti3O 12 x = 1.10, and its preparation method includes the following steps: (1) Weigh titanium dioxide powder, bismuth oxide powder, and lanthanum oxide powder according to the composition of high-energy-storage-characteristic relaxable bismuth layered structure ceramic (weighing is performed using an electronic balance, with a weighing accuracy of 0.001g); wherein, the purity of titanium dioxide is 99.9%, the purity of bismuth oxide is 99.999%, and the purity of lanthanum oxide is 99.99%; mix the weighed raw materials and put them into a nylon can, add anhydrous ethanol to the can no more than 2 / 3 of the height of the can, and use zirconia balls and zirconia columns as grinding balls (zirconia ball particle size is 6mm). Zirconia cylinders (10mm in diameter × 10mm in height, half in number) were mixed in a nylon can on a planetary ball mill at 240 rpm for 6 hours. The resulting powder was then dried in an oven and sieved through a 40-mesh nylon sieve. The sieved powder was then pressed into cylinders with a diameter of 65mm and a height of 20mm using a press. The cylinders were calcined at 850℃ for 2 hours in an atmospheric atmosphere, then crushed and passed through a 40-mesh sieve to obtain ceramic powder. (2) The ceramic powder is mixed with a binder and granulated, then sieved and molded to obtain a ceramic green body; wherein the binder is a 7 wt.% polyvinyl alcohol aqueous solution; the amount of binder added is 6.5% of the mass of the ceramic powder; a 40-mesh sieve is used for sieving, and the molding pressure is 1.5 MPa; the ceramic green body is a small cylindrical ceramic green body with a diameter of 13 mm and a height of 1 mm. (3) The ceramic green body is subjected to plastic removal and sintering to obtain bismuth layered ceramic; wherein the plastic removal temperature is 650℃ and the plastic removal time is 2h; the sintering heating rate is 2℃ / min, the sintering temperature is 1120℃ and the sintering time is 2h.

[0040] The bismuth layered ceramic prepared in Example 1 was subjected to X-ray diffraction testing, such as... Figure 1 As shown in the figure, the bismuth layered ceramic prepared in Example 1 is free of impurities.

[0041] Figure 2 This is a microscopic morphology image of the bismuth layered ceramic in Example 1. As shown in the figure, the bismuth layered ceramic prepared in Example 1 has a dense surface structure, with fine and uniform grains that exhibit the typical lamellar grain characteristics of a bismuth layered structure.

[0042] The bismuth layered ceramic prepared in Example 1 was ground flat on both sides, polished, and silver-plated with electrodes, and its electrical performance was tested (e.g., ...). Figures 5-7 As shown in the figure, the bismuth layered ceramic prepared in Example 1 clearly exhibits relaxation characteristics, and the hysteresis loops are significantly refined (as shown in the figure). Figures 5-6 (As shown). Curie temperature (T) m The dielectric peak decreased significantly, and the dielectric peak broadened, exhibiting characteristics of a dispersed phase transition (e.g., Figure 7(As shown). In summary, the bismuth layered ceramic prepared in Example 1, while possessing excellent relaxation properties, achieved ultra-high energy storage performance, with an energy storage density of 5.9 J / cm³. 3 The efficiency reached 72.8%.

[0043] Example 2

[0044] The preparation process of the high energy storage characteristic relaxable bismuth layered structure ceramic in this Example 2 is the same as that in Example 1, except that: x = 1.2, and the sintering temperature in step (3) is 1130℃.

[0045] The bismuth layered ceramic prepared in Example 2 was subjected to X-ray diffraction testing, such as... Figure 1 As shown in the figure, the bismuth layered ceramic prepared in Example 2 is free of impurities.

[0046] Figure 3 This is a microscopic morphology image of the bismuth layered ceramic structure prepared in Example 2. As can be seen from the image, the bismuth layered ceramic structure prepared in Example 2 has a dense surface and fine grains.

[0047] The bismuth layered ceramic prepared in Example 2 was ground flat on both sides, polished, and silver-plated with electrodes, and its electrical performance was tested (e.g., ...). Figure 5 , 6 As shown in Figure 8, the bismuth layered ceramic prepared in Example 2 exhibits relaxation characteristics, with a significantly refined hysteresis loop (as shown in Figure 8). Figure 5 , 6 (As shown). Curie temperature (T) m The dielectric peak decreased significantly, and the dielectric peak broadened, exhibiting obvious characteristics of a dispersed phase transition (e.g., Figure 8 (As shown). The bismuth layered ceramic prepared in Example 2 achieved an ultra-high energy density of 11.2 J / cm³ due to its excellent relaxation properties. 3 The efficiency reached 83.5%.

[0048] Example 3

[0049] The preparation process of the high energy storage characteristic relaxable bismuth layered structure ceramic in this embodiment 3 is the same as that in embodiment 1, except that: x = 1.4, and the sintering temperature in step (3) is 1140℃.

[0050] The bismuth layered ceramic prepared in Example 3 was subjected to X-ray diffraction testing, such as... Figure 1 As shown in the figure, the bismuth layered ceramic prepared in Example 3 is free of impurities.

[0051] Figure 4 This is a microscopic morphology image of the bismuth layered ceramic structure prepared in Example 3. As can be seen from the image, the bismuth layered ceramic structure prepared in Example 3 has a dense surface and fine grains.

[0052] The bismuth layered ceramic prepared in Example 3 was ground flat on both sides, polished, and silver-plated with electrodes, and its electrical performance was tested (e.g., ...). Figure 5 , 6 As shown in Figure 9, the bismuth layered ceramic prepared in Example 3 exhibits relaxation characteristics, with a significantly refined hysteresis loop (as shown in Figure 9). Figure 5 , 6 (As shown). Curie temperature (T) m The dielectric peak decreased significantly, and the dielectric peak broadened, exhibiting obvious characteristics of a dispersed phase transition (e.g., Figure 9 (As shown). The bismuth layered ceramic prepared in Example 3 achieved an ultra-high energy density of 7.2 J / cm³ due to its excellent relaxation properties. 3 The efficiency reached 88.1%.

[0053] Comparative Example 1

[0054] The preparation process of the bismuth layered ceramic in Comparative Example 1 is the same as that in Example 1, except that: x = 0, and the sintering temperature in step (3) is 1000℃.

[0055] The bismuth layered ceramic prepared in Comparative Example 1 was ground flat on both sides, polished, and silver-plated with electrodes. Its electrical performance was then tested (e.g., ...). Figure 10 As shown in the figure, the hysteresis loop of the bismuth layered ceramic prepared in Comparative Example 1 exhibits a typical square hysteresis loop of a ferroelectric material, with a storage density of less than 1 J / cm². 3 .

[0056] Comparative Example 2

[0057] The preparation process of the bismuth layered ceramic in Comparative Example 2 is the same as that in Example 1, except that: x = 0.5, and the sintering temperature in step (3) is 1050℃.

[0058] The bismuth layered ceramic prepared in Comparative Example 2 was ground flat on both sides, polished, and silver-plated with electrodes. Its electrical performance was then tested (e.g., ...). Figure 10 As shown in the figure, the hysteresis loop of the bismuth layered ceramic prepared in Comparative Example 2 exhibits a typical square hysteresis loop of a ferroelectric material, with a storage density of 1.0 J / cm³. 3 .

[0059] Comparative Example 3

[0060] The preparation process of the bismuth layered ceramic in Comparative Example 3 is the same as that in Example 1, except that: x = 1.0, and the sintering temperature in step (3) is 1100℃.

[0061] The bismuth layered ceramic prepared in Comparative Example 3 was ground flat on both sides, polished, and silver-plated with electrodes. Its electrical performance was then tested (e.g., ...). Figure 10As shown in the figure, the hysteresis loop of the bismuth layered ceramic prepared in Comparative Example 3 exhibits a typical square hysteresis loop of a ferroelectric material, with a storage density of 1.3 J / cm³. 3 .

[0062] Comparative Example 4

[0063] The preparation process of the bismuth layered ceramic in Comparative Example 4 is the same as that in Example 1, except that: x = 1.5, and the sintering temperature in step (3) is 1180℃.

[0064] The bismuth layered ceramic prepared in Comparative Example 4 was ground flat on both sides, polished, and silver-plated with electrodes. Its electrical performance was then tested (e.g., ...). Figure 10 As shown in the figure, the hysteresis loop of the bismuth layered ceramic prepared in Comparative Example 4 exhibits a significant refinement as the material transitions from a relaxor ferroelectric phase to a paraelectric phase. During this phase transition, the polarization intensity of the material decreases substantially, directly causing the storage density to drop to 4 J / cm². 3 The following factors significantly limit energy storage performance.

[0065] Comparative Example 5

[0066] The preparation process of the bismuth layered ceramic in Comparative Example 5 is the same as that in Example 1, except that the sintering temperature is 1200℃.

[0067] Figure 11 The figure shows the surface microstructure of the bismuth layered ceramic in Comparative Example 5. As can be seen from the figure, the sintering temperature of the bismuth layered relaxor ceramic prepared in Comparative Example 5 was too high, resulting in excessive volatilization of Bi element and the formation of a distinct second phase. Therefore, it was impossible to obtain a pure bismuth layered relaxor ceramic.

[0068] Comparative Example 6

[0069] The preparation process of the bismuth layered ceramic in Comparative Example 6 is the same as that in Example 1, except that the sintering temperature is 800℃.

[0070] Figure 12 The figure shows the surface microstructure of the bismuth layered ceramic in Comparative Example 6. As can be seen from the figure, the bismuth layered relaxed ceramic prepared in Comparative Example 6 has many pores between its grains, making it difficult to obtain a dense ceramic material.

[0071] Table 1 lists the composition and performance parameters of the bismuth layered ceramics prepared in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0072] Table 1:

[0073] As shown in Table 1, the breakdown field strength of the bismuth layered ceramics prepared in Examples 1-3 is generally higher than 700 kV / cm, and the energy storage density reaches 5.9-11.2 J / cm. 3 It possesses high potential for energy storage applications. Notably, when the La content exceeds 1%, bismuth lanthanum titanate ceramics exhibit strong relaxation behavior: the dielectric peak broadens significantly, demonstrating typical dielectric relaxation characteristics, while the Curie temperature (T0) also increases. m The temperature dropped below room temperature, marking the first time such a low Tf has been achieved in a bismuth layered ferroelectric material. m Among them, the energy storage performance of the ceramic is optimal when the La content is 1.2%, with an energy storage density as high as 11.2 J / cm³. 3 The efficiency reaches 83.5%; however, when the La content exceeds 1.2%, the ceramic hysteresis loop gradually approaches linearity, and the maximum polarization intensity (P) reaches 83.5%. max The decrease in La content leads to a reduction in both energy storage density and efficiency. In Comparative Example 3, the La content was too low, resulting in a decrease in La... 3+ Compare 3+ The substitution is limited to the perovskite-like layer and cannot eliminate (Bi2O2). 2+ The suppression of ceramic relaxation behavior prevented the acquisition of relaxable bismuth layered ceramics. In Comparative Example 4, the excessively high La content resulted in overly strong relaxation characteristics, causing the material to approach the linear dielectric region and significantly reduce polarization intensity, leading to a decrease in storage density to 4 J / cm². 3 The following methods cannot achieve high energy storage characteristics.

[0074] In summary, the high-energy-storage-characteristic relaxable bismuth layered structure ceramic effectively enhances energy storage performance through the regulation of relaxation behavior, which makes it show great application potential in the field of multilayer ceramic capacitors.

Claims

1. A relaxor-type bismuth layered ceramic with high energy storage characteristics, characterized in that, The chemical composition of the high-energy-storage-performance relaxor bismuth layered ceramic is Bi. 4-x La x Ti3O 12 , where 1.10≤x≤1.

40.

2. The high-energy-storage-characteristic relaxable bismuth layered structure ceramic according to claim 1, characterized in that, x＝1.2。 3. The high-energy-storage-characteristic relaxable bismuth layered structure ceramic according to claim 1 or 2, characterized in that, The recyclable energy storage density of the aforementioned high-energy-storage-performance relaxor bismuth layered ceramic is 5.9–11.2 J / cm³. 3 ; The energy storage efficiency of the high-energy-storage-characteristic relaxor bismuth layered ceramic is 72.8–88.1%. The breakdown electric field of the high-energy-storage-characteristic relaxor bismuth layered ceramic is 725–912 kV / cm.

4. A method for preparing a high-energy-storage-characteristic relaxable bismuth layered ceramic according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Weigh out titanium source, bismuth source and lanthanum source according to the stoichiometric ratio of high energy storage relaxation type bismuth layered structure ceramic and mix them. After calcination, ceramic powder is obtained. (2) The ceramic powder is mixed with the binder and granulated, then sieved and molded to obtain a ceramic green body; (3) The ceramic green body is subjected to plasticizing and sintering to obtain the high energy storage characteristic relaxor bismuth layered structure ceramic.

5. The preparation method according to claim 4, characterized in that, The titanium source is titanium dioxide powder; the bismuth source is bismuth oxide powder; the lanthanum source is lanthanum oxide powder; The binder is a polyvinyl alcohol aqueous solution with a concentration of 6-7 wt.%; the amount of binder added is 6-7 wt% of the ceramic powder mass.

6. The preparation method according to claim 4 or 5, characterized in that, The mixing method is ball milling; the parameters of the ball milling include: the ball milling medium is anhydrous ethanol, the grinding balls are zirconia balls and zirconia columns, the ball milling speed is 240-260 r / min, and the ball milling time is 5-6 h; The calcination temperature is 800–1050℃, and the time is 2–3 hours.

7. The preparation method according to any one of claims 4-6, characterized in that, The sieve mesh size is 40 to 80 mesh, preferably 40 mesh; The compression molding pressure is 1.5 to 5 MPa.

8. The preparation method according to any one of claims 4-7, characterized in that, In step (3), the temperature of the plastic discharge is 600-750℃ and the time is 2-3h; preferably, the heating rate of the plastic discharge is 1-2℃ / min. The sintering temperature is 1100–1150°C, and the time is 2–4 hours; preferably, the sintering heating rate is 1–3°C / min.

9. An energy storage ceramic element, characterized in that, include: The high-energy-storage-characteristic relaxable bismuth layered structure ceramic according to any one of claims 1-3, and the electrodes distributed on the surface of the high-energy-storage-characteristic relaxable bismuth layered structure ceramic.

10. The application of a high-energy-storage-characteristic relaxor bismuth layered structure ceramic according to any one of claims 1-3 in a multilayer ceramic capacitor.

Images