A high-entropy component-modified barium titanate-based relaxor ferroelectric material, a ferroelectric film with high energy storage characteristics, and a preparation method thereof

Abstract

The present invention relates to a high-entropy component-modified barium titanate-based relaxor ferroelectric material, a ferroelectric thin film with high energy storage characteristics, and a preparation method thereof. The chemical composition of the high-entropy component-modified barium titanate-based relaxor ferroelectric material is: (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, where 0.08 ≤ x ≤ 0.14. The ferroelectric thin film with high energy storage characteristics is composed of a substrate, a lanthanum nickelate conductive layer in the middle, and a barium titanate-based relaxor ferroelectric thin film on the top. The preparation method of the ferroelectric thin film with high energy storage characteristics includes: (1) preparing a lanthanum nickelate conductive layer epitaxially grown along the substrate; (2) coating a barium titanate-based precursor solution on the surface of the lanthanum nickelate conductive layer and performing pre-annealing treatment; (3) performing final annealing treatment on the material after the pre-annealing treatment is completed.

Description

Technical Field

[0001] The invention belongs to the technical field of functional ceramic films, and in particular relates to a high-entropy component-modified barium titanate-based relaxor ferroelectric material, a ferroelectric film with high energy storage characteristics, and a preparation method thereof. Background Art

[0002] Ultrafast charge / discharge processes and ultrahigh power density make dielectrics important components in modern electrical and electronic devices, especially in pulsed power systems. However, in recent years, the energy storage performance of existing dielectrics has been increasingly unable to meet the growing demand for miniaturization and integration, which has stimulated further research on dielectrics with higher energy density and efficiency. Among various inorganic dielectrics, perovskite relaxor ferroelectrics are considered to be promising candidates for energy storage applications, with high dielectric constants and relatively high efficiency.

[0003] According to the state of the material, dielectric materials can be roughly divided into three categories: ceramics, polymers, and thin films. Compared with bulk materials, film capacitors have higher voltage resistance; compared with polymer materials, film capacitors have higher polarization and better temperature stability, so their comprehensive energy storage characteristics are the best. The energy storage density of dielectric materials themselves is low and cannot achieve high endurance, so research on them is mainly focused on improving their energy storage density and optimizing reliability. How to further improve the energy storage performance of film capacitors is a key issue that needs to be solved urgently, and it is also the focus of current research. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention aims to provide a high-entropy component-modified barium titanate-based relaxor ferroelectric material, a ferroelectric film with high energy storage characteristics and a preparation method thereof. 1 / 5 Ni 1 / 5Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3 doping, compared with the low entropy component Bi(Ni 2 / 3 Nb 1 / 3 )O3 achieves a comprehensive improvement in the breakdown electric field and energy storage density of ferroelectric films, providing relaxor ferroelectric energy storage materials with more application potential for large-scale integrated circuits.

[0005] In one aspect, the present invention provides a high entropy component-modified barium titanate-based relaxor ferroelectric material, wherein the chemical composition of the high entropy component-modified barium titanate-based relaxor ferroelectric material is: (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5)O3, where 0.08≤x≤0.14; when x<0.08, the content of the high entropy component is low, and the effect on the structure of the barium titanate matrix is ​​not obvious, resulting in a low energy storage density; when x>0.14, the content of the high entropy component is too high, exceeding the reasonable range, resulting in a low energy storage density.

[0006] In the present invention, the high entropy bismuth-based component Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, forming BaTiO3-Bi(Mg 1 / 5Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3 solid solution relaxor ferroelectric material, and obtained ferroelectric films with greatly improved breakdown electric field and energy storage density.

[0007] On the other hand, the present invention also provides a ferroelectric film with high energy storage characteristics, which is composed of a substrate, a lanthanum nickelate conductive layer located in the middle and a barium titanate-based relaxor ferroelectric film located on the top, and the material composition of the barium titanate-based relaxor ferroelectric film is the barium titanate-based relaxor ferroelectric material modified by the high entropy component.

[0008] Preferably, the breakdown electric field of the ferroelectric film with high energy storage characteristics is 2.441-3.902 MV / cm; the energy storage density is 27.5-57.4 J / cm 3 ; The energy storage efficiency is 69.6~77.3%.

[0009] Preferably, the method for preparing the ferroelectric thin film with high energy storage characteristics comprises the following steps:

[0010] preparing a lanthanum nickelate conductive layer epitaxially grown along a substrate;

[0011] A barium titanate-based precursor solution is coated on the surface of the lanthanum nickelate conductive layer for pre-annealing treatment; the pre-annealing treatment is divided into three stages, the first stage is drying at 160-200° C. for 4-10 minutes, the second stage is pyrolysis at 400-500° C. for 5-10 minutes, and the third stage is annealing at 700-750° C. for 3-5 minutes;

[0012] The material after the pre-annealing treatment is subjected to a final annealing treatment, wherein the temperature of the final annealing treatment is 700-750° C. and the time is 10-30 minutes; thus a ferroelectric film with high energy storage characteristics is obtained.

[0013] Preferably, preparing a lanthanum nickelate conductive layer epitaxially grown along a substrate comprises:

[0014] (1) dissolving lanthanum nitrate in glacial acetic acid, adding acetylacetone after complete dissolution, and finally adding nickel acetate, and obtaining a lanthanum nickelate precursor solution after complete dissolution; the concentration of lanthanum nitrate in the lanthanum nickelate precursor solution is 0.15-0.2 mol / L; the molar ratio of lanthanum nitrate to nickel acetate is 1:1; the obtained lanthanum nickelate precursor solution is allowed to stand for aging; the standing aging time is 24-48 hours;

[0015] (2) coating the aged lanthanum nickelate precursor solution in step (1) onto the surface of the substrate, and then performing a pre-annealing treatment;

[0016] (3) After repeating step (2) several times, a final annealing treatment is performed to obtain a lanthanum nickelate conductive layer epitaxially grown along the substrate.

[0017] Preferably, the pre-annealing treatment is divided into three stages, the first stage is drying at 160-200°C for 4-10 minutes, the second stage is pyrolysis at 400-500°C for 5-10 minutes, and the third stage is annealing at 700-750°C for 3-5 minutes; the temperature of the final annealing treatment is 700-750°C and the time is 10-30 minutes.

[0018] Preferably, according to the chemical composition of the barium titanate-based relaxor ferroelectric material modified by the high entropy component, bismuth acetate, barium acetate, zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are weighed; bismuth acetate and barium acetate are successively dissolved in a mixture of glacial acetic acid and acetylacetone to obtain solution A; the weighed zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are successively dissolved in a mixture of glacial acetic acid, ethylene glycol methyl ether and acetylacetone to obtain solution B; finally, solutions A and B are mixed to obtain a barium titanate-based precursor solution.

[0019] Preferably, in the mixed solution of glacial acetic acid and acetylacetone, the volume ratio of glacial acetic acid to acetylacetone is (2-3):(1-2); in the mixed solution of glacial acetic acid, ethylene glycol methyl ether and acetylacetone, the volume ratio of glacial acetic acid, ethylene glycol methyl ether and acetylacetone is (6-8):(2-4):(4-6).

[0020] Preferably, the concentration of bismuth acetate in solution A is 0.0352-0.0616 mol / L; the concentration of tetrabutyl titanate in solution B is 0.344-0.368 mol / L.

[0021] Preferably, the volume ratio of solution A to solution B is 1:1.

[0022] The present invention adds high entropy component Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5)O3 is used to regulate the local lattice distortion of the barium titanate matrix, thereby improving its energy storage properties. Due to the presence of a variety of different atomic sizes, masses, and electronegativity elements in the high entropy components, the barium titanate matrix produces a large local lattice distortion. For thin film materials, local lattice distortion has a significant effect on its domain structure and electrical properties.

[0023] Beneficial effects:

[0024] In the present invention, the high entropy bismuth-based component Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, changed the electrical properties of the high energy storage ferroelectric film: breakdown electric field 2.441 ~ 3.902MV / cm; recoverable energy storage density 27.5 ~ 57.4J / cm 3 , the energy storage efficiency is 69.6-77.3%. The obtained material has the advantages of high electric field resistance, high energy storage density, lead-free and environmentally friendly, providing a relaxor ferroelectric energy storage material with more application potential for large-scale integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a scanning electron microscope image of a cross section of the barium titanate-based relaxor ferroelectric thin film in Example 3;

[0026] Figure 2 High-resolution θ-2θ and φ scan images of the barium titanate-based relaxor ferroelectric thin film in Example 3;

[0027] Figure 3 1 is a unipolar hysteresis loop diagram of Examples 1-4 and Comparative Example 1;

[0028] Figure 4 It is a graph showing the changes in energy storage density and breakdown electric field of Examples 1-4 and Comparative Example 1;

[0029] Figure 5 The unipolar hysteresis loop diagrams of Examples 1-4 and Comparative Examples 2-3;

[0030] Figure 6 The graphs are the changes of energy storage density and breakdown electric field of Examples 1-4 and Comparative Examples 2-3;

[0031] Figure 7 The unipolar hysteresis loop diagrams of Example 3 and Comparative Examples 4-5;

[0032] Figure 8 It is a graph showing the changes in energy storage density and breakdown electric field of Example 3 and Comparative Examples 4-5;

[0033] Fig. 9The unipolar hysteresis loop diagrams of Example 3 and Comparative Examples 6-7;

[0034] Fig.10 It is a graph showing the changes in energy storage density and breakdown electric field of Example 3 and Comparative Examples 6-7. DETAILED DESCRIPTION

[0035] To further explain the content, features and practical effects of the present invention, the present invention is described in detail below in conjunction with the embodiments. It should be pointed out that the modification method of the design of the present invention is not limited to these specific implementation methods. Without departing from the spirit and connotation of the design of the present invention, the equivalent replacement and modification made by those skilled in the art on the basis of reading the content of the present invention are also within the scope of the present invention.

[0036] The following is an exemplary description of a method for preparing a ferroelectric thin film with high energy storage characteristics provided by the present invention.

[0037] (1) Prepare a lanthanum nickelate precursor solution. Weigh appropriate amounts of lanthanum nitrate and nickel acetate to make the molar ratio of lanthanum ions to nickel ions 1:1. First, dissolve the weighed lanthanum nitrate in an appropriate amount of glacial acetic acid, heat and stir in a water bath at 60-80°C for 10-15 minutes until it is completely dissolved. Then add an appropriate amount of acetylacetone to make the volume ratio of acetylacetone to glacial acetic acid 1:2. Keep warm at 60-80°C for 15-30 minutes. Finally, add the weighed nickel acetate, heat and stir in a water bath at 60-80°C for 10-15 minutes until it is completely dissolved, and obtain a green and clear lanthanum nickelate precursor solution. The concentration of lanthanum nitrate in the obtained lanthanum nickelate precursor solution is 0.15-0.2 mol / L. Let the lanthanum nickelate precursor solution stand for 24-48 hours for subsequent coating.

[0038] (2) Spin coating the aged lanthanum nickelate precursor solution onto the substrate surface, followed by pre-annealing.

[0039] The ferroelectric film prepared by the present invention is an epitaxial film, so a single crystal oxide is used as a substrate, such as LaAlO3, MgO, and SrTiO3. In the present invention, a (001) oriented single crystal SrTiO3 (10×10×0.5 mm) is selected as a substrate. The (001) oriented single crystal SrTiO3 substrate (10×10×0.5 mm) is ultrasonically cleaned with acetone, deionized water, and alcohol for 3 to 5 minutes in sequence, and then the substrate is blown dry with high-purity nitrogen.

[0040] In an optional embodiment, the spin coating has a rotation speed of 3000 to 4000 rpm and a time of 20 to 30 seconds.

[0041] The pre-annealing treatment is divided into three stages: the first stage is drying at 160-200°C for 4-10 minutes, the second stage is pyrolysis at 400-500°C for 5-10 minutes, and the third stage is annealing at 700-750°C for 3-5 minutes. The purpose of the pre-annealing treatment of the present invention is to crystallize the single-layer film obtained by spin coating, thereby obtaining the target film material. Among them, drying makes the excess solvent in the wet film, such as acetic acid, acetylacetone, and ethylene glycol methyl ether volatilize; pyrolysis is to remove the residual solvent and most of the organic part to form an amorphous film; annealing makes the amorphous film densified and then forms the desired crystalline phase.

[0042] (3) After repeating step (2) several times, a final annealing treatment is performed to obtain a lanthanum nickelate conductive layer epitaxially grown along the substrate.

[0043] In an optional embodiment, the temperature of the final annealing treatment is 700-750° C. and the time is 10-30 minutes. The purpose of the final annealing treatment of the present invention is to fully densify and crystallize the film.

[0044] (4) Prepare a barium titanate-based precursor solution. According to the chemical composition of (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5Nb 1 / 5)O3, wherein the stoichiometric ratio of 0.08≤x≤0.14 is 0.08≤x≤0.14. Appropriate amounts of bismuth acetate, barium acetate, zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are weighed. The bismuth acetate is weighed 10 mol% more than the aforementioned stoichiometric ratio. First, the weighed bismuth acetate and barium acetate are dissolved in a mixture of glacial acetic acid and acetylacetone in turn, and heated and stirred in a water bath at 60-90°C for 15-30 minutes to obtain solution A. The volume ratio of glacial acetic acid and acetylacetone is (2-3): (1-2). Subsequently, the weighed zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are dissolved in a mixture of glacial acetic acid, ethylene glycol methyl ether and acetylacetone in turn, and stirred at room temperature for 30-45 minutes to obtain solution B. The volume ratio of glacial acetic acid, ethylene glycol methyl ether and acetylacetone is (6-8): (2-4): (4-6). The concentration of bismuth acetate in solution A is 0.0352-0.0616 mol / L. The concentration of tetrabutyl titanate in solution B is 0.344-0.368 mol / L. Finally, solutions A and B are mixed (volume ratio of 1:1), stirred at room temperature for 1-2 hours, and aged for 24-48 hours to obtain a barium titanate-based precursor solution with a preset concentration of 0.2 mol / L. If the preset concentration of the barium titanate-based precursor solution is too large, the thickness of the single-layer spin coating will be too large, and the film cannot be fully densified in the pre-annealing stage, affecting the quality of the film; if the preset concentration of the barium titanate-based precursor solution is too small, the thickness of the single-layer spin coating will be too small, the film thickness will be thin, and the dead layer effect at the bottom electrode-film interface will be aggravated.

[0045] (5) Spin coating the barium titanate-based precursor solution obtained in step (4) onto the surface of the lanthanum nickelate conductive layer obtained in step (3), followed by pre-annealing.

[0046] In an optional embodiment, the spin coating speed is 4000-6000 rpm, and the time is 20-30 seconds.

[0047] The pre-annealing treatment is divided into three stages: the first stage is drying at 160-200° C. for 4-10 minutes, the second stage is pyrolysis at 400-500° C. for 5-10 minutes, and the third stage is annealing at 700-750° C. for 3-5 minutes.

[0048] (6) After repeating step (5) several times, a final annealing treatment is performed to obtain a barium titanate-based relaxor ferroelectric thin film.

[0049] In an optional embodiment, the temperature of the final annealing treatment is 700-750°C and the time is 10-30 minutes. If the annealing temperature is too low, the driving force for film growth is insufficient, the crystallinity deteriorates, and the film quality is poor; if the annealing temperature is too high, the film grows excessively, the grains become larger, and its electrical resistance deteriorates.

[0050] The purpose of coating the lanthanum nickelate precursor solution on the substrate of the present invention is: (1) since the substrate used is an oxide insulating substrate, it cannot meet the subsequent electrical performance test requirements, so it is necessary to coat a layer of conductive lanthanum nickelate film on the substrate to form a metal-dielectric-metal sandwich structure with the barium titanate-based relaxor ferroelectric film and the upper metal electrode to meet the electrical performance test requirements; (2) lanthanum nickelate can also be used as a growth template for the barium titanate-based relaxor ferroelectric film, which can reduce the crystallization temperature of the barium titanate-based relaxor ferroelectric film to a certain extent.

[0051] Film capacitors are usually composed of two electrodes, upper and lower electrodes, and a dielectric in the middle. Their performance mainly depends on the dielectric material in the middle. The energy stored in the capacitor when it is charged is the area enclosed by the left side of the charging curve in the PE curve, which can be expressed as: The released electrical energy (hereinafter referred to as energy storage density) is the area enclosed by the left side of the discharge curve in the PE curve, which can be expressed as: The efficiency of electrical energy release (hereinafter referred to as energy storage efficiency) can be expressed as: η = W rec / (W rec +W loss )×100%. It can be seen that in order to further improve the energy storage performance of film capacitors, it is necessary to further improve their electric field strength and polarization intensity difference (larger saturation polarization intensity P max and a smaller residual polarization intensity P r ). The present invention uses high entropy component Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3 doping, compared with the low entropy component Bi(Ni 2 / 3 Nb 1 / 3 )O3 realizes the comprehensive improvement of the breakdown electric field and energy storage density of the barium titanate-based relaxor ferroelectric thin film material. This is due to: (1) the presence of a variety of elements with different atomic sizes, masses and electronegativity in the high entropy component causes a large local lattice distortion in the barium titanate matrix. For thin film materials, local lattice distortion has a significant effect on its domain structure, electrical properties, etc. Therefore, the present invention aims to improve the breakdown electric field and energy storage density of the barium titanate-based relaxor ferroelectric thin film material by adding the high entropy component Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, to regulate the local lattice distortion of the barium titanate matrix, thereby improving its energy storage density; (2) by introducing high entropy components, the disorder of the perovskite B site is regulated, in particular, the introduction of Mg with a large ionic radius in equal molar amounts 2+ 、Ni 2+ 、Zn 2+ 、Zr 4+ , Nb5+ ions to aggravate the lattice distortion and further increase the site disorder, reduce the residual polarization intensity, induce the generation and enhancement of relaxation characteristics, reduce the grain size, increase the breakdown field strength, and thus obtain excellent energy storage density.

[0052] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0053] Example 1

[0054] The ferroelectric film with high energy storage characteristics is composed of a substrate, a lanthanum nickelate conductive layer in the middle and a barium titanate-based relaxor ferroelectric film on the top. The material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5Zr 1 / 5 Nb 1 / 5 )O3(x=0.08). The preparation method comprises:

[0055] (1) Weigh appropriate amounts of lanthanum nitrate and nickel acetate to make the molar ratio of lanthanum ions to nickel ions 1:1. First, dissolve the weighed lanthanum nitrate in an appropriate amount of glacial acetic acid, heat and stir in a 60°C water bath for 15 minutes until it is completely dissolved, add an appropriate amount of acetylacetone, so that the volume ratio of acetylacetone to glacial acetic acid is 1:2, and keep warm at 60°C for 30 minutes. Then add the weighed nickel acetate, heat and stir in a 60°C water bath for 15 minutes until it is completely dissolved, and obtain a green clear solution with a solution concentration of 0.15 mol / L. Let the mixed solution stand and age for 24 hours to obtain a lanthanum nickelate precursor solution;

[0056] (2) A (001) oriented single crystal SrTiO3 substrate (10×10×0.5 mm) was ultrasonically cleaned with acetone, deionized water, and alcohol for 3 to 5 min, and then the substrate was blown dry with high-purity nitrogen;

[0057] (3) Spin coating the lanthanum nickelate precursor onto the substrate surface at a speed of 3000 rpm for 25 seconds. Place the substrate in a rapid annealing furnace for pre-annealing. The pre-annealing is divided into three stages: the first stage is drying at 200°C for 10 minutes, the second stage is pyrolysis at 450°C for 5 minutes, and the third stage is annealing at 750°C for 5 minutes.

[0058] (4) After repeating step (3) 7 times, a final annealing treatment is performed in a rapid annealing furnace: the temperature is kept at 750° C. for 30 minutes. Thus, a lanthanum nickel oxide conductive layer epitaxially grown along the substrate is obtained;

[0059] (5) According to the chemical formula (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, wherein the stoichiometric ratio of x=0.08 and the preset concentration of the barium titanate-based precursor solution is 0.2mol / L, weigh appropriate amounts of bismuth acetate, barium acetate, zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate. First, dissolve the weighed bismuth acetate and barium acetate in a mixture of glacial acetic acid and acetylacetone in turn, wherein bismuth acetate is weighed at most 10mol%, and heat and stir in a water bath at 80°C for 30 minutes to obtain solution A; then dissolve the weighed zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate in a mixture of glacial acetic acid, ethylene glycol methyl ether and acetylacetone in turn, and stir at room temperature for 30 minutes to obtain solution B; wherein the volume ratio of glacial acetic acid, ethylene glycol methyl ether and acetylacetone is 7:3:5; finally, mix solutions A and B, stir at room temperature for 2 hours, and stand and age for 48 hours to obtain the barium titanate-based precursor solution;

[0060] (6) Spin coating the barium titanate-based precursor solution obtained in step (5) onto the surface of the lanthanum nickelate conductive layer obtained in step (4) at a spin coating speed of 5000 rpm for 25 seconds. Then place it in a rapid annealing furnace for pre-annealing. The pre-annealing is divided into three stages: the first stage is drying at 200°C for 4 minutes, the second stage is pyrolysis at 450°C for 5 minutes, and the third stage is annealing at 750°C for 5 minutes.

[0061] (7) After repeating step (6) 8 times, a final annealing treatment is performed in a rapid annealing furnace at 750° C. for 30 minutes to obtain a barium titanate-based relaxor ferroelectric thin film.

[0062] Example 2

[0063] The preparation method is similar to that of Example 2, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3(x=0.10).

[0064] Example 3

[0065] The preparation method is similar to that of Example 1, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3(x=0.12).

[0066] Figure 1 This is a cross-sectional scanning electron microscope image of the barium titanate-based relaxor ferroelectric film in Example 3. As can be seen from the figure, the barium titanate-based relaxor ferroelectric film prepared in Example 3 is composed of an STO substrate at the bottom, a lanthanum nickelate conductive layer in the middle, and a barium titanate-based relaxor ferroelectric film layer at the top. It can be seen that each layer is dense and non-porous, and has clear boundaries, indicating that the film growth quality is good.

[0067] Figure 2 The high resolution of the barium titanate-based relaxor ferroelectric film in Example 3 Scan and θ-2θ scan. It can be seen from the figure that there is only (001) diffraction peak, and both the barium titanate-based relaxor ferroelectric film and the STO substrate show four-fold symmetry, indicating that the film grows epitaxially along the substrate.

[0068] Example 4

[0069] The preparation method is similar to that of Example 1, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3(x=0.14).

[0070] Comparative Example 1

[0071] The preparation method is similar to that of Example 1, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Ni 2 / 3 Nb 1 / 3 )O3(x=0.10). In step (5), according to the chemical formula (1-x)BaTiO3-xBi(Ni 2 / 3Nb 1 / 3)O3, wherein the stoichiometric ratio of x=0.10 and the preset concentration of the solution is 0.2mol / L, appropriate amounts of bismuth acetate, barium acetate, nickel acetate, niobium ethoxide and tetrabutyl titanate are weighed. First, the weighed bismuth acetate and barium acetate are dissolved in a mixture of glacial acetic acid and acetylacetone in turn, wherein bismuth acetate is weighed as much as 10mol%, and heated in a water bath at 80°C and stirred for 30 minutes to obtain solution A; then, the weighed nickel acetate, niobium ethoxide and tetrabutyl titanate are dissolved in a mixture of glacial acetic acid and acetylacetone in turn, and stirred at room temperature for 30 minutes to obtain solution B; wherein the volume ratio of glacial acetic acid to acetylacetone is 2:1; finally, solutions A and B are mixed, stirred at room temperature for 2 hours, and allowed to stand and age for 48 hours to obtain the barium titanate-based precursor solution.

[0072] Comparative Example 2

[0073] The preparation method is similar to that of Example 1, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3(x=0.06).

[0074] Comparative Example 3

[0075] The preparation method is similar to that of Example 1, except that the material composition of the barium titanate-based relaxor ferroelectric film is (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3(x=0.16).

[0076] Comparative Example 4

[0077] The preparation method is similar to that of Example 3, except that in step (5), the preset concentration of the barium titanate-based precursor solution is 0.15 mol / L.

[0078] Comparative Example 5

[0079] The preparation method is similar to that of Example 3, except that in step (5), the preset concentration of the barium titanate-based precursor solution is 0.25 mol / L.

[0080] Comparative Example 6

[0081] The preparation method is similar to that of Example 3, except that the annealing temperature of the third stage of the pre-annealing treatment in step (6) and the final annealing temperature in step (7) are both 650°C.

[0082] Comparative Example 7

[0083] The preparation method is similar to that of Example 3, except that the annealing temperature of the third stage of the pre-annealing treatment in step (6) and the final annealing temperature in step (7) are both 800°C.

[0084] Pt electrodes were prepared on the surface of the barium titanate-based relaxor ferroelectric films prepared in Examples 1-4 and Comparative Examples 1-7 by magnetron sputtering: background vacuum <4.6×10-4Pa, deposition power 100W, deposition pressure 1Pa, deposition atmosphere pure Ar, target-substrate spacing 80mm, target material Pt target. The ferroelectric performance was tested by dynamic hysteresis test method, the test frequency was 1kHz, and the test results were as follows: Figure 3-10 shown.

[0085] Figure 3 1 is a unipolar hysteresis loop diagram of Examples 1-4 and Comparative Example 1; Figure 4 The figure shows the changes in energy storage density and breakdown electric field of Examples 1-4 and Comparative Example 1. 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3 compared to Bi(Ni 2 / 3 Nb 1 / 3 )O3 can improve the electrical resistance and saturation polarization strength of barium titanate-based relaxor ferroelectric films.

[0086] Figure 5 The unipolar hysteresis loop diagrams of Examples 1-4 and Comparative Examples 2-3; Figure 6 The diagram shows the changes in energy storage density and breakdown electric field of Examples 1-4 and Comparative Examples 2-3. As can be seen from the figure, when x < 0.08, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Examples 1-4. This is because the x content is low and the effect on the barium titanate matrix is ​​not obvious, resulting in its energy storage performance being lower than that of Examples 1-4. When x > 0.14, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Examples 1-4. This is because the x content is high, exceeding the reasonable range, resulting in the aggravation of the negative effect of the high entropy component on the barium titanate matrix, thereby making its energy storage performance lower than that of Examples 1-4.

[0087] Figure 7 The unipolar hysteresis loop diagrams of Example 3 and Comparative Examples 4-5; Figure 8It is a graph showing the changes in energy storage density and breakdown electric field of Example 3 and Comparative Examples 4-5. It can be seen from the figure that when the preset concentration of the barium titanate-based precursor solution is 0.15 mol / L, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Example 3. This is because the film thickness obtained at a low concentration is relatively thin, which aggravates the dead layer effect at the bottom electrode-film interface, resulting in poor electrical resistance of the film, thereby making its energy storage performance lower than that of Example 3. When the preset concentration of the barium titanate-based precursor solution is 0.25 mol / L, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Example 3. This is because the thickness of the single-layer film increases at a high concentration, leaving more pores in the pre-annealing stage, resulting in poor electrical resistance of the film, thereby making its energy storage performance lower than that of Example 3.

[0088] Fig. 9 The unipolar hysteresis loop diagrams of Example 3 and Comparative Examples 6-7; Fig.10 The diagram shows the changes in energy storage density and breakdown electric field of Example 3 and Comparative Examples 6-7. As can be seen from the figure, when the annealing temperature is 650°C, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Example 3. This is because the annealing temperature is low and the film is not fully grown and crystallized, resulting in poor quality and lower energy storage performance than Example 3. When the annealing temperature is 800°C, the energy storage performance of the barium titanate-based relaxor ferroelectric film is lower than that of Example 3. This is because the annealing temperature is too high, the film grows excessively, the grains become larger, and the electrical resistance is reduced, making its energy storage performance lower than that of Example 3.

[0089] Table 1 shows the composition, process parameters and energy storage performance parameters of the ferroelectric thin film prepared by the present invention:

[0090]

[0091] As shown in Table 1, compared with Bi(Ni 2 / 3 Nb 1 / 3 )O3 component, high entropy Bi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3 component can significantly improve the electrical resistance and energy storage properties of ferroelectric films. When x = 0.12, the energy storage density reaches the optimal value (57.4 J / cm 3 ), the breakdown electric field is 3.902MV / cm, and the energy storage efficiency is 69.6%.

Claims

1. A ferroelectric thin film with high energy storage characteristics, characterized in that: The ferroelectric film with high energy storage characteristics is composed of a substrate, a lanthanum nickelate conductive layer in the middle and a barium titanate-based relaxor ferroelectric film on the top; the material composition of the barium titanate-based relaxor ferroelectric film is a barium titanate-based relaxor ferroelectric material modified by a high entropy component, and its chemical composition is: (1-x)BaTiO3-xBi(Mg 1 / 5 Ni 1 / 5 Zn 1 / 5 Zr 1 / 5 Nb 1 / 5 )O3, wherein 0.12≤x≤0.14; the energy storage density of the ferroelectric film with high energy storage characteristics is 46.5~57.4J / cm 3 .

2. The ferroelectric thin film with high energy storage characteristics according to claim 1, characterized in that: The breakdown electric field of the ferroelectric film with high energy storage characteristics is 2.765-3.902 MV / cm; the energy storage efficiency is 69.6-77.3%.

3. The method for preparing a ferroelectric thin film with high energy storage characteristics according to claim 1 or 2, characterized in that: The following steps are involved: preparing a lanthanum nickelate conductive layer epitaxially grown along a substrate; A barium titanate-based precursor solution is coated on the surface of the lanthanum nickelate conductive layer for pre-annealing treatment; the pre-annealing treatment is divided into three stages, the first stage is drying at 160-200° C. for 4-10 minutes, the second stage is pyrolysis at 400-500° C. for 5-10 minutes, and the third stage is annealing at 700-750° C. for 3-5 minutes; The material after the pre-annealing treatment is subjected to a final annealing treatment, wherein the temperature of the final annealing treatment is 700-750° C. and the time is 10-30 minutes; thus a ferroelectric film with high energy storage characteristics is obtained.

4. The preparation method according to claim 3, characterized in that: The method of preparing a lanthanum nickelate conductive layer epitaxially grown along a substrate comprises: (1) dissolving lanthanum nitrate in glacial acetic acid, adding acetylacetone after complete dissolution, and finally adding nickel acetate, and obtaining a lanthanum nickelate precursor solution after complete dissolution; the concentration of lanthanum nitrate in the lanthanum nickelate precursor solution is 0.15-0.2 mol / L; the molar ratio of lanthanum nitrate to nickel acetate is 1:1; allowing the obtained lanthanum nickelate precursor solution to stand for aging; the standing aging time is 24-48 hours; (2) coating the aged lanthanum nickelate precursor solution in step (1) onto the surface of the substrate, and then performing a pre-annealing treatment; (3) After repeating step (2) several times, a final annealing treatment is performed to obtain a lanthanum nickel oxide conductive layer epitaxially grown along the substrate.

5. The preparation method according to claim 3, characterized in that: According to the chemical composition of the barium titanate-based relaxor ferroelectric material modified by the high entropy component, bismuth acetate, barium acetate, zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are weighed; bismuth acetate and barium acetate are sequentially dissolved in a mixed solution of glacial acetic acid and acetylacetone to obtain solution A; the weighed zinc acetate, magnesium ethoxide, nickel acetate, zirconium n-propoxide, niobium ethoxide and tetrabutyl titanate are sequentially dissolved in a mixed solution of glacial acetic acid, ethylene glycol methyl ether and acetylacetone to obtain solution B; finally, solutions A and B are mixed to obtain a barium titanate-based precursor solution.

6. The preparation method according to claim 5, characterized in that: In the mixed solution of glacial acetic acid and acetylacetone, the volume ratio of glacial acetic acid to acetylacetone is (2-3):(1-2); in the mixed solution of glacial acetic acid, ethylene glycol methyl ether and acetylacetone, the volume ratio of glacial acetic acid, ethylene glycol methyl ether and acetylacetone is (6-8):(2-4):(4-6).

7. The preparation method according to claim 5, characterized in that The concentration of bismuth acetate in solution A is 0.0352-0.0616 mol / L; the concentration of tetrabutyl titanate in solution B is 0.344-0.368 mol / L.

8. The preparation method according to claim 5 or 7, characterized in that: The volume ratio of solution A to solution B is 1:1.

Images