Bismuth titanate-based high-entropy flexible material as well as preparation method and application thereof

Abstract

The invention relates to the field of functional ceramics, in particular to a bismuth titanate-based high-entropy flexible material as well as a preparation method and application thereof. The chemical formula of the bismuth titanate-based high-entropy flexible material is Bi < 4-4x > (LaNdPrSm) < x > Ti < 3 > O < 12 >, and x is less than or equal to 0.75. Different elements are introduced to the Bi position of a ferroelectric material Bi4Ti3O12 to regulate and control the configuration entropy of a system, so that the obtained bismuth titanate-based material overcomes the brittleness problem of a traditional ceramic film material, shows excellent flexibility of folding without breakage, and has a dielectric constant and temperature stability superior to those of a traditional polymer-based flexible dielectric material; the method can be used as a dielectric capacitor in the flexible wearable field and the like, meanwhile, the method provides a solution for flexible preparation of the ceramic material, and the application field of the ceramic material is expanded.

Description

Technical Field

[0001] The present invention relates to the field of functional ceramics, and particularly to a bismuth titanate-based high-entropy flexible material, a preparation method thereof, and an application thereof. Background Art

[0002] The rapid development of the flexible electronics field has put forward higher requirements for the research and development of high-performance flexible energy storage devices. Currently, the mainstream electrical energy storage devices mainly include four categories: fuel cells, lithium-ion batteries, electrochemical energy storage devices, and dielectric capacitors. Among them, dielectric capacitors exhibit significant advantages due to their unique polarization energy storage mechanism: extremely high power density (10 4 -10 7 W / kg), ultra-fast charge / discharge speed (in the microsecond or even nanosecond range), high working voltage (up to kilovolt level), and high safety. Therefore, they show broad application prospects in the field of high-performance energy storage. Generally, polymer-based dielectric capacitors (such as BOPP, PEI, PDMS, etc.) have good mechanical flexibility and thus have great application potential in the field of flexible energy storage. However, the poor thermo-mechanical stability and low dielectric constant of polymer-based materials limit their further application in complex environments. Ceramic-based dielectric materials are known for their excellent temperature stability and high dielectric constant and may become substitutes for polymer-based dielectrics. However, ceramics generally exhibit inherent brittleness at room temperature because the binding mode of the material mainly composed of ionic bonds or covalent bonds directly limits its plastic deformation ability. When an external force acts, due to the lack of an energy dissipation mechanism in ceramics, stress concentration at defects will cause cracks to rapidly expand according to Griffith's theory, showing macroscopic brittle fracture. Currently, the research on flexible ceramic thin film dielectric capacitors mainly focuses on depositing ceramic thin films on flexible substrates (mica sheets, metal foils, etc.), and by "borrowing" the bendable characteristics of the substrates, a certain flexibility is given to the ceramic thin film dielectric capacitors. However, such materials have significant limitations in practical applications: the mechanical mismatch and stress / strain concentration at the interface between the "hard" ceramic thin film and the "flexible" substrate will affect the growth quality of the dielectric thin film, reduce the densification and uniformity of the ceramic thin film, and thus lead to a significant reduction in energy storage performance. Therefore, realizing the flexible preparation of self-supporting ceramic dielectric materials without relying on substrates is the key to the development of advanced flexible electronics.

[0003] In the past few decades, people have been committed to improving the deformation ability of ceramic materials. A relatively common method is to reduce the size of the material to one-dimensional nanowires / nanofibers or two-dimensional ultrathin films. For example, a tensile fracture deformation of 4.84% was achieved in alumina-based ceramic nanofibers with a diameter of about 300 nm, and a tensile fracture deformation of 18% was achieved in amorphous SiO2 nanowires with a diameter of 5.3 nm; the crystalline La 0.7 Ca 0.3The MnO3 film exhibits a tensile deformation of 8.2%, but due to the formation of periodic cracks, when the thickness exceeds 20 nm, its maximum deformation value drops below 2%. Recently, in a single-crystalline ferroelectric BaTiO3 film with a thickness of 120 nm, a tensile strain of 10.05% can be achieved through the special dynamic evolution of ferroelectric nanodomains. Despite these advances, considering the low dimensions, difficult applications, and complex preparation processes of these materials, the practical applications of these materials are still very difficult. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this purpose, the present invention provides a bismuth titanate-based high-entropy flexible material, its preparation method and application. By introducing different elements at the Bi site of the ferroelectric material Bi4Ti3O 12 (bismuth titanate) to regulate the configurational entropy of the system, the obtained bismuth titanate-based material overcomes the brittleness problem of traditional ceramic thin film materials, exhibits excellent flexibility of folding without breaking, and both the dielectric constant and temperature stability are superior to traditional polymer-based flexible dielectric materials. It can be used as a dielectric capacitor in the flexible wearable field, etc. At the same time, this method also provides a solution idea for the flexible preparation of ceramic materials and expands its application fields.

[0005] For this purpose, the first aspect of the present invention provides a bismuth titanate-based high-entropy flexible material, and the chemical formula of the bismuth titanate-based high-entropy flexible material is Bi 4-4x (LaNdPrSm) x Ti3O 12 , where 0 < x ≤ 0.75.

[0006] To solve the deficiencies in the existing technology, the present invention introduces equal proportions of four elements, La, Nd, Pr, and Sm, at the Bi site of the ferroelectric material Bi4Ti3O 12 to regulate the configurational entropy of the material system, and then realizes the design of the intrinsic crystal structure of the material (including grain size and amorphous content, etc.). Finally, the obtained Bi4Ti3O 12 material has a nanocrystal / amorphous dual-phase structure. This structure not only enables it to overcome the brittleness problem of traditional ceramic thin film materials and exhibits excellent flexibility of folding without breaking, but also the dielectric constant and temperature stability are superior to traditional polymer-based flexible dielectric materials. The obtained bismuth titanate-based high-entropy flexible material can be used in flexible electronic devices, such as being used as a dielectric capacitor in the flexible wearable field, etc.

[0007] According to an embodiment of the present invention, the configurational entropy of the bismuth titanate-based high-entropy flexible material is 0.0R - 1.6R and is not 0.0R.

[0008] According to an embodiment of the present invention, the bismuth titanate-based high-entropy flexible material has an amorphous / nanocrystalline composite structure, the proportion of the amorphous structure is 50%-95%, and the size of the nanocrystals is 2-30 nm.

[0009] The second aspect of the present invention provides a method for preparing the bismuth titanate-based high-entropy flexible material described in the first aspect, including:

[0010] Taking bismuth salt, lanthanum salt, neodymium salt, praseodymium salt, samarium salt, and titanium salt according to the stoichiometric ratio, and mixing them with a solvent to obtain a sol, and obtaining an aged solution through aging treatment;

[0011] Depositing the aged solution on a substrate, and obtaining the bismuth titanate-based high-entropy flexible material through heat treatment and annealing treatment.

[0012] The method for realizing the flexibility of ceramic dielectric films through entropy regulation in the present invention provides a new solution idea for solving the brittleness problem of ceramic materials. The obtained flexible ceramic dielectric film (i.e., the bismuth titanate-based high-entropy flexible material) can be used as a dielectric capacitor in the flexible wearable field. At the same time, this method can be extended to other types of functional ceramic films, and it is expected to realize the flexible preparation of various ceramic materials, thereby expanding their application fields.

[0013] According to an embodiment of the present invention, the solvent includes at least one of propionic acid and acetic acid.

[0014] According to an embodiment of the present invention, the temperature of the heat treatment is 100-400 °C, and the time is 2-10 min.

[0015] According to an embodiment of the present invention, the annealing treatment includes: heating up to 500-700 °C at a rate of 10-30 °C / s, and holding for 20-60 min.

[0016] According to an embodiment of the present invention, the method further includes: spin-coating and depositing the aged solution on a substrate, and performing the heat treatment to obtain a single-layer film;

[0017] Repeating the deposition step of the single-layer film until the film thickness reaches the target thickness, and performing the annealing treatment on the obtained film material to obtain the bismuth titanate-based high-entropy flexible material.

[0018] According to an embodiment of the present invention, the rotation speed of the spin-coating is 3000-6000 rpm, and the time is 10-50 s.

[0019] According to an embodiment of the present invention, the substrate includes a hard material layer, a sacrificial layer, and a protective layer stacked in sequence, and the aged solution is deposited on the protective layer.

[0020] According to an embodiment of the present invention, the material of the hard material layer includes SrTiO3.

[0021] According to an embodiment of the present invention, the material of the sacrificial layer includes at least one of Sr3Al2O6, Sr4Al2O7, and LaSrMnO3.

[0022] According to an embodiment of the present invention, the material of the protective layer includes at least one of Au and Pt.

[0023] According to an embodiment of the present invention, the method further includes: covering a transfer layer on the surface of the bismuth titanate-based high-entropy flexible material to obtain a composite material, placing the composite material in water, dissolving the sacrificial layer so that the bismuth titanate-based high-entropy flexible material is separated from the substrate, obtaining an intermediate material in which the bismuth titanate-based high-entropy flexible material is combined with the transfer layer, and peeling the bismuth titanate-based high-entropy flexible material from the transfer layer to obtain a self-supporting bismuth titanate-based high-entropy flexible material.

[0024] The third aspect of the present invention provides an application of the bismuth titanate-based high-entropy flexible material described in the first aspect or the bismuth titanate-based high-entropy flexible material obtained by the method described in the second aspect in flexible electronic devices.

[0025] The fourth aspect of the present invention provides a flexible electronic device, which includes the bismuth titanate-based high-entropy flexible material described in the first aspect or the bismuth titanate-based high-entropy flexible material obtained by the method described in the second aspect.

[0026] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0028] Figure 1 Shows the morphology test results of different entropy value samples prepared in the embodiments and comparative examples of the present invention. Among them, Figure a is the XRD spectrum of BiTO-0R material, BiTO-0.9R material, and BiTO-1.6R material; Figure b is the HRTEM image of BiTO-1.6R material; Figure c is the HRTEM image of BiTO-0.9R material;

[0029] Figure 2 Shows the HRTEM image of the BiTO-0R material prepared in Comparative Example 1 of the present invention. Among them, Figure b corresponds to the boxed area in Figure a;

[0030] Figure 3Shows the mechanical test results of samples with different entropy values prepared in the embodiments of the present invention. Among them, Figure a is the SEM image of the BiTO-0.9R material during the bending process; Figure b is the maximum bending strain of the in-situ bending test of the BiTO-0.9R material obtained by finite element analysis simulation; Figure c is the SEM image of the BiTO-1.6R material during the bending process; Figure d is the maximum bending strain of the in-situ bending test of the BiTO-1.6R material obtained by finite element analysis simulation;

[0031] Figure 4 Shows the in-situ tensile test results of the BiTO-1.6R material prepared in Example 2 of the present invention. Among them, Figure a is the schematic diagram of the experimental device for in-situ tensile loading and a series of TEM images during the tensile process; Figure b is the stress-strain curve of the BiTO-1.6R material;

[0032] Figure 5 Shows the SEM image of the BiTO-0R material prepared in Comparative Example 1 of the present invention under external force;

[0033] Figure 6 Shows the dielectric constant and dielectric loss test diagrams of the BiTO-1.6R material prepared in Example 2 of the present invention at different temperatures. Detailed Description of the Invention

[0034] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0035] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0036] In the ranges disclosed herein, the endpoints and any value are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0037] To make it easier to understand the present invention, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which the present invention pertains.

[0038] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0039] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0040] According to an embodiment of the present invention, the first aspect of the present invention provides a bismuth titanate-based high entropy flexible material, the chemical formula of the bismuth titanate-based high entropy flexible material is Bi 4-4x (LaNdPrSm) x Ti3O 12 , where 0 <x≤0.75。

[0041] The present invention adopts Bi4Ti3O 12 The four elements La, Nd, Pr, and Sm were introduced into the Bi position in equal proportions, and the proportions of the introduced elements were adjusted to prepare Bi4Ti3O with different entropy values. 12 The value of x is not particularly limited and satisfies 0 <x≤0.75即可,例如x可为0.1、0.15、0.2、0.25、0.3、0.35、0.4、0.45、0.5、0.55、0.6、0.65、0.7、0.75等。

[0042] According to a specific embodiment of the present invention, the configuration entropy of the bismuth titanate-based high entropy flexible material is 0.0R-1.6R, and is not 0.0R. The calculation formula of the configuration entropy is: Where R is the ideal gas constant, x i 、x j represent the molar ratios of the elements in the cation and anion positions, respectively.

[0043] According to a specific embodiment of the present invention, the bismuth titanate-based high entropy flexible material is an amorphous / nanocrystalline composite structure, the amorphous structure accounts for 50%-95%, and the size of the nanocrystal is 2-30nm. This composite structure enables the material to overcome the brittleness problem of traditional ceramic thin film materials, showing excellent flexibility that can be folded without breaking, and the dielectric constant and temperature stability are better than traditional polymer-based flexible dielectric materials.

[0044] According to an embodiment of the present invention, the second aspect of the present invention provides a method for preparing a bismuth titanate-based high-entropy flexible material according to the first aspect, comprising:

[0045] (1) Take bismuth salt, lanthanum salt, neodymium salt, praseodymium salt, samarium salt, and titanium salt according to the stoichiometric ratio, and mix them with a solvent to obtain a sol, which is then aged to obtain an aged solution.

[0046] According to specific embodiments of the present invention, the specific types of the bismuth salt, lanthanum salt, neodymium salt, praseodymium salt, samarium salt, and titanium salt are not particularly limited as long as they can provide the corresponding metal ions. As some specific examples, organic salts containing various metal ions can be used, such as bismuth acetate, lanthanum acetate, neodymium acetate, titanium acetate, praseodymium acetate, samarium acetate, tetrabutyl titanate, etc.

[0047] According to specific embodiments of the present invention, the type of the solvent is not particularly limited, and those skilled in the art can select according to the situation. As some specific examples, propionic acid, acetic acid, etc. can be used. At the same time, a stabilizer, such as ethanolamine, can also be added in this step to adjust the pH value of the sol and improve the dispersibility, etc.

[0048] According to specific embodiments of the present invention, after obtaining the sol, it can be filtered to remove possible impurities therein. The filtered sol is subjected to a sealed static aging treatment, and the aging time is not particularly limited, for example, 7 - 12 days.

[0049] (2) Deposit the aged solution on a substrate, and obtain the bismuth titanate - based high - entropy flexible material through heat treatment and annealing treatment.

[0050] According to specific embodiments of the present invention, the deposition method is not particularly limited, including but not limited to spin - coating the aged solution into a film on the substrate by using the chemical solvent deposition method, and then performing heat treatment. The rotation speed and time of the spin - coating are not particularly limited and can be adjusted according to the state of the obtained film. For example, the rotation speed of the spin - coating is 3000 - 6000 rpm, and the time is 10 - 50 s. The number of spin - coating times is not particularly limited and can be adjusted according to the thickness requirement. For example, the spin - coating is repeated 2 - 9 times (i.e., 3 - 10 layers of films are obtained). A heat treatment step is required after each deposition.

[0051] According to specific embodiments of the present invention, the heat treatment temperature and time are not particularly limited, and those skilled in the art can select according to the situation. As some specific examples, the heat treatment temperature is 100 - 400 °C, and the time is 2 - 10

[0052] According to specific embodiments of the present invention, when the deposited film reaches the target thickness, the film is subjected to high - temperature annealing treatment, and the conditions of this treatment are not particularly limited. Those skilled in the art can select according to the situation. As some specific examples, it is heated to 500 - 700 °C at a rate of 10 - 30 °C / s and held for 20 - 60 min.

[0053] According to specific embodiments of the present invention, for the convenience of subsequently peeling and transferring the prepared material from the substrate for mechanical testing, the substrate can be provided to include a sacrificial layer and a protective layer in addition to the hard material layer. The hard material layer is the commonly used substrate material, such as SrTiO3, etc. The sacrificial layer is used to separate the bismuth titanate-based high-entropy flexible material from the substrate subsequently. It can be Sr3Al2O6, Sr4Al2O7, LaSrMnO3, etc. This material can be dissolved in water to achieve lossless and low-cost material transfer. The protective layer is provided to prevent the sacrificial layer from being dissolved by the solvent in the precursor sol during the spin coating process. The material of the protective layer can be Au, Pt, etc. The thickness of the protective layer can be 10 - 50 nm.

[0054] Specifically, after the deposition of the target material is completed using the aforementioned composite substrate, a transfer layer can be covered on the surface of the obtained sample (including the substrate and the target material), and then placed in deionized water. The prepared material is transferred to the surface of the transfer layer by dissolving the sacrificial layer. Subsequently, the target material is peeled off from the transfer layer to obtain the self-supporting bismuth titanate-based high-entropy flexible material for mechanical property detection. The material of the transfer layer is not particularly limited, including but not limited to polydimethylsiloxane (PDMS). The thickness of the transfer layer can be 30 - 100 μm.

[0055] The solution of the present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0056] Example 1

[0057] Weigh bismuth acetate, lanthanum acetate, neodymium acetate, titanyl acetate, praseodymium acetate, samarium acetate, and tetrabutyl titanate according to the stoichiometric ratio of 0.2M×10mL (corresponding to x = 0.25 in the chemical formula), and mix them in a propionic acid solvent (where the bismuth acetate raw material is 5% in excess of the stoichiometric ratio to make up for the volatilization of Bi element during the heat treatment process). Stir at 60°C for 10 min, then cool to room temperature and continue to stir for 5 - 7 h to obtain a clear and transparent precursor colloidal sol. Then, filter the sol using a filter membrane with a pore size of 0.2 μm to remove the possible impurities therein. The filtered sol needs to be sealed and left to age for 7 - 12 days.

[0058] The aged colloid was deposited on the Au / Sr3Al2O6 / SrTiO3 substrate by spin coating at a speed of 6000 rpm for 20 s to obtain a wet film. Then, heat treatments were carried out on a hot plate at 150 °C and 400 °C for 2 min and 10 min respectively. The heat-treated film was continuously spin-coated repeatedly to control the thickness of the deposited film, and the heat treatment steps needed to be repeated after each deposition. When the thickness of the film reached the desired value (3 layers in this example), the film was annealed at a high temperature using a rapid annealing furnace. The annealing conditions were: heating rate of 10 - 30 °C / s, annealing temperature of 600 °C, and holding time of 30 min, thus obtaining a bismuth titanate-based ceramic thin film material with an entropy of 0.9R, named BiTO-0.9R.

[0059] A layer of PDMS film was covered on the surface of the sample deposited on the hard substrate as a protective layer, and then the whole was immersed in deionized water. After 2 - 6 h, the sacrificial layer Sr3Al2O6 would gradually dissolve, and the bismuth titanate-based ceramic thin film transferred to the PDMS was obtained. Then, peeling was carried out in a focused ion beam-scanning electron microscope (FIB-SEM) system to obtain a self-supporting thin film sample for mechanical property testing.

[0060] Example 2

[0061] Bismuth acetate, lanthanum acetate, neodymium acetate, titanyl acetate, praseodymium acetate, samarium acetate, and tetrabutyl titanate were weighed according to the stoichiometric ratio of 0.2M×10 mL (corresponding to x = 0.75 in the chemical formula), and mixed in a propionic acid solvent (where the bismuth acetate raw material was 5% in excess of the stoichiometric ratio to make up for the volatilization of Bi element during the heat treatment). Stirring was carried out at 60 °C for 10 min, and then continued to stir for 5 - 7 h after cooling to room temperature to obtain a clear and transparent precursor colloidal sol. Then, the sol was filtered using a filter membrane with a pore size of 0.2 μm to remove the possible impurities therein. The filtered sol needed to be sealed and left to age for 7 - 12 days.

[0062] The aged colloid was deposited on the Au / Sr3Al2O6 / SrTiO3 substrate by spin coating at a speed of 6000 rpm for 20 s to obtain a wet film. Then, heat treatments were carried out on a hot plate at 150 °C and 400 °C for 2 min and 10 min respectively. The heat-treated film was continuously spin-coated repeatedly to control the thickness of the deposited film, and the heat treatment steps needed to be repeated after each deposition. When the thickness of the film reached the desired value (3 layers in this example), the film was annealed at a high temperature using a rapid annealing furnace. The annealing conditions were: heating rate of 10 - 30 °C / s, annealing temperature of 600 °C, and holding time of 30 min, thus obtaining a bismuth titanate-based ceramic thin film material with an entropy of 1.6R, named BiTO-1.6R.

[0063] Cover the surface of the sample deposited on the hard substrate with a PDMS film as a protective layer, and then immerse the whole in deionized water. After 2 - 6 h, the sacrificial layer Sr3Al2O6 will gradually dissolve, and a bismuth titanate-based ceramic film transferred to the PDMS will be obtained. Then, it is peeled in the FIB-SEM system to obtain a self-supporting film sample for mechanical property testing.

[0064] Comparative Example 1

[0065] Weigh bismuth acetate and tetrabutyl titanate according to the stoichiometric ratio of 0.2M×10mL (corresponding to x = 0 in the chemical formula), and mix them in a propionic acid solvent (where the bismuth acetate raw material is 5% in excess based on the stoichiometric ratio to make up for the volatilization of Bi element during the heat treatment). Stir at 60 °C for 10 min, then continue to stir for 5 - 7 h after cooling to room temperature to obtain a clear and transparent precursor colloidal sol. Then, filter the sol with a filter membrane with a pore size of 0.2 μm to remove possible impurities, and the filtered sol needs to be sealed and left to age for 7 - 12 days. The subsequent spin coating, heat treatment, annealing, transfer, and peeling processes are the same as those in Example 1, and the sample is abbreviated as BiTO-0R.

[0066] Test Example

[0067] The samples prepared in each example and comparative example were subjected to morphology testing and mechanical property testing, and the results are as follows:

[0068] (1) The samples prepared in each example and comparative example were subjected to X-ray diffraction experiments (XRD), and the results are shown in Figure 1 . Among them Figure 1 Figure a shows that with the increase of the entropy value, the amorphous structure gradually increases. Combining the results of high-resolution transmission electron microscopy (HRTEM) (see Figures b - c in Figure 1 and Figure 2 ), it can be known that the BiTO-0R material is a fully crystalline polycrystalline structure, and both the BiTO-0.9R material and the BiTO-1.6R material exhibit an amorphous / nanocrystalline composite structure. Among them, the size of the nanocrystals in the BiTO-1.6R material is about 2 nm, while the grain size of the BiTO-0.9R material is about 20 nm, and the amorphous content is lower than that of the BiTO-1.6R material.

[0069] Furthermore, the BiTO-0.9R and BiTO-1.6R materials were peeled in the FIB-SEM system for mechanical property testing. The results show that the BiTO-0.9R material fractured after undergoing a bending strain of 0.8% (see Figures a - b in Figure 3 ), while the BiTO-1.6R film can be bent 180° without fracture, and the maximum bending strain is 4.8% (seeFigure 3 (in Figure c-d). In addition, in-situ tensile tests show that the maximum tensile fracture strain of the BiTO-1.6R high-entropy thin film is 5.29% (see Figure 4 in Figure a-b), showing good tensile resistance.

[0070] (2) The materials prepared in the comparative example were tested by scanning electron microscopy (SEM), and the results are shown in Figure 5 . The results show that the BiTO-0R material suddenly ruptures under external force, showing brittleness. By comparison, the material provided by the present invention has better flexibility.

[0071] (3) The dielectric constant and dielectric loss of the prepared flexible BiTO-1.6R high-entropy thin film were tested at different temperatures, and the results are shown in Figure 6 , indicating that it has good dielectric constant stability in the temperature range of -100 to 200 °C, and the dielectric loss remains at a low level.

[0072] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0073] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A bismuth titanate-based high-entropy flexible material, characterized in that, The chemical formula of the bismuth titanate-based high-entropy flexible material is Bi 4-4x (LaNdPrSm) x Ti3O 12 , where 0 < x ≤ 0.

75.

2. The bismuth titanate-based high-entropy flexible material according to claim 1, wherein The configurational entropy of the bismuth titanate-based high-entropy flexible material is 0.0R - 1.6R and is not 0.0R; Optionally, the bismuth titanate-based high-entropy flexible material is an amorphous / nanocrystalline composite structure, the proportion of the amorphous structure is 50% - 95%, and the size of the nanocrystals is 2 - 30 nm.

3. A method for preparing the bismuth titanate-based high-entropy flexible material according to claim 1 or 2, characterized in that, It includes: Taking bismuth salt, lanthanum salt, neodymium salt, praseodymium salt, samarium salt, and titanium salt according to the stoichiometric ratio, and mixing them with a solvent to obtain a sol, and obtaining an aged solution through aging treatment; Depositing the aged solution on a substrate, and obtaining the bismuth titanate-based high-entropy flexible material through heat treatment and annealing treatment.

4. The method according to claim 3, characterized in that, The solvent includes at least one of propionic acid and acetic acid.

5. The method according to claim 3, characterized in that, The temperature of the heat treatment is 100 - 400 °C, and the time is 2 - 10 min; Optionally, the annealing treatment includes: heating to 500 - 700 °C at a rate of 10 - 30 °C / s, and holding for 20 - 60 min.

6. The method according to claim 3, wherein The method further includes: spin-coating and depositing the aged solution on a substrate, and performing the heat treatment to obtain a single-layer film; Repeating the deposition step of the single-layer film until the film thickness reaches the target thickness, and performing the annealing treatment on the obtained film material to obtain the bismuth titanate-based high-entropy flexible material; Optionally, the rotation speed of the spin-coating is 3000 - 6000 rpm, and the time is 10 - 50 s.

7. The method according to claim 3, wherein The substrate includes a hard material layer, a sacrificial layer, and a protective layer stacked in sequence, and the aged solution is deposited on the protective layer; Optionally, the material of the hard material layer includes SrTiO3; Optionally, the material of the sacrificial layer includes at least one of Sr3Al2O6, Sr4Al2O7, and LaSrMnO3; Optionally, the material of the protective layer includes at least one of Au and Pt.

8. The method according to claim 7, wherein The method further includes: covering a transfer layer on the surface of the bismuth titanate-based high-entropy flexible material to obtain a composite material, placing the composite material in water, dissolving the sacrificial layer so that the bismuth titanate-based high-entropy flexible material is separated from the substrate, obtaining an intermediate material in which the bismuth titanate-based high-entropy flexible material is composite with the transfer layer, and peeling the bismuth titanate-based high-entropy flexible material from the transfer layer to obtain a self-supporting bismuth titanate-based high-entropy flexible material.

9. Application of the bismuth titanate-based high-entropy flexible material according to claim 1 or 2 or the bismuth titanate-based high-entropy flexible material obtained by the method according to any one of claims 3 - 8 in flexible electronic devices.

10. A flexible electronic device, characterized in that, The flexible electronic device includes the bismuth titanate-based high-entropy flexible material according to claim 1 or 2 or the bismuth titanate-based high-entropy flexible material obtained by the method according to any one of claims 3 - 8.

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