Sodium bismuth titanate-based lead-free ferroelectric film

Abstract

The invention belongs to the technical field of ferroelectric materials, and particularly relates to a Sr0. 4Na0. 2NbO3 doped Bi0. 5Na0. 5TiO3 (BNT) based ferroelectric film and a preparation method of the Sr0. 4Na0. 2NbO3 based ferroelectric film. A modified sodium bismuth titanate Bi0. 5Na0. 5TiO3 (BNT)-based material is doped with A / B site elements, Sr0. 4Na0. 2NbO3 with a tungsten bronze structure is selected as a doping component, the chemical composition is (0.94-x) Bi0. 5Na0. 5Na0. 2NbO3, the doping amount of the Sr0. 4Na0. 2NbO3 is 0.01-0.1, the doping amount of the Sr0. 4Na0. 2NbO3 is 0.01-0.1, and 1 mol% of manganese is additionally doped on the basis of the Sr0. 4Na0. 2NbO3. The lead-free ferroelectric film is prepared by a sol-gel method. The breakdown resistance (Eb) and recoverable energy storage density (Wrec) of the sodium bismuth titanate-based lead-free ferroelectric film prepared according to the invention are remarkably improved, compared with an undoped sample, the Eb is improved by 56%, the maximum polarization intensity (Pmax) reaches 102.4 [mu] C / cm < 2 >, and the Wrec is improved from 94.11 J / cm < 3 > to 128.82 J / cm < 3 > and improved by 37%.

Description

Technical Field

[0001] This invention relates to the field of ferroelectric materials technology, specifically to a Sr... 0.4 Na 0.2 NbO3-doped Bi 0.5 Na 0.5 Preparation method of TiO3(BNT) based ferroelectric thin film. Background Technology

[0002] Dielectric capacitors, due to their extremely high power density, ultrafast charge and discharge rates, unique switching characteristics, and rapid electromechanical response, have become a promising and ideal choice for advanced high-precision information storage and pulse power systems. Ferroelectrics are a special type of dielectric material that exhibits spontaneous polarization within a certain temperature range. Ferroelectric materials in thin film form, due to their anisotropic structural characteristics at different scales, have their ferroelectric properties significantly affected by factors such as crystal phase, grain size, nanodomains, spontaneous polarization, and ion displacement. Furthermore, their light weight and small size have led to their widespread application in many fields in recent years, especially in pulse power devices for energy storage. (Bismuth sodium titanate Bi) 0.5 Na 0.5 TiO3 (BNT), as a typical ferroelectric material, possesses high intrinsic polarization and, compared to traditional lead-containing ferroelectric materials, is more in line with the requirements of sustainable development. However, pure BNT suffers from a relatively large remanent polarization (P0). r ) and lower puncture strength (E b This allows it to recover its energy storage density (W). rec The relatively low polarization intensity of BNT-based films significantly limits their application in energy storage devices. Therefore, it is necessary to explore suitable modification methods to improve the Ep of the modified BNT-based films while maintaining a high polarization intensity. b This improves the energy storage performance of the thin film. Summary of the Invention

[0003] The purpose of this invention is to provide a Sr 0.4 Na 0.2 NbO3-doped sodium bismuth titanate-based ferroelectric thin films and their preparation methods are used to address the current E-type dielectric capacitors. b With W rec Lower-level issues.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a Sr 0.4 Na 0.2 NbO3-doped BNT-based ferroelectric thin films, wherein the Sr 0.4 Na 0.2The chemical composition of the NbO3-doped BNT-based ferroelectric thin film is: (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3:1 mol% Mn (x = 0.01 ~ 0.1).

[0006] The application further provides a Sr 0.4 Na 0.2 A preparation method of the NbO3-doped BNT-based ferroelectric thin film comprises the following steps:

[0007] (1) Bismuth acetate, sodium acetate, potassium acetate, zirconium acetate, barium acetate, strontium acetate and manganese acetate are weighed according to stoichiometric ratios, and then dissolved in acetic acid to obtain solution A after stirring at 70 ℃ for 30 min;

[0008] (2) Acetylacetone (AcAc) and tetrabutyl titanate are added to ethylene glycol methyl ether according to stoichiometric ratios, and then stirred at 40 ℃ for 30 min to obtain solution B;

[0009] (3) Solution A and solution B are mixed, and a stoichiometric amount of ethoxy niobium is added, and then stirred at 80 ℃ for 30 min and stirred at room temperature for 12 h after aging, to obtain a precursor solution after filtration;

[0010] (4) The precursor solution is spin-coated on a substrate with a conductive coating, and then heat-treated;

[0011] (5) After repeating the process of (4) several times to reach a target thickness, postannealing is performed to obtain a series of Sr 0.4 Na 0.2 NbO3-doped BNT-based ferroelectric thin films.

[0012] Further, the volume ratio of acetic acid to ethylene glycol methyl ether is 3:2;

[0013] In the step (1), the bismuth acetate, sodium acetate and potassium acetate are weighed in excess of 10 mol%.

[0014] In the step (2), the molar ratio of tetrabutyl titanate to AcAc is 1:2.

[0015] Further, the concentration of the precursor solution is set to 0.1 ~ 0.3 mol / L; and the aging time is 1 ~ 7 days.

[0016] Further, the substrate with the conductive coating is Pt / Ti / SiO2 / Si or LaNiO3 / SiO2 / Si; the substrate is cleaned in deionized water, anhydrous ethanol and ethylene glycol at 60 DEG C under ultrasonic for 15 min before spin coating of the precursor solution; the spin coating speed is 2500-4000 r / min, and the spin coating time is 30 s.

[0017] Further, the heat treatment is divided into three stages: the first stage is evaporation at 200 DEG C for 5 min; the second stage is pyrolysis at 400 DEG C for 5 min; and the third stage is crystallization at 700 DEG C for 5 min.

[0018] Further, the post-annealing process is holding at 725 DEG C for 30 min.

[0019] Further, the (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3 film has a thickness of 100-500 nm.

[0020] The application also provides a Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric film in the preparation of energy storage capacitors, the capacitor from bottom to top is: Si, SiO2, Ti, Pt, Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric film and Ag.

[0021] The application has the following beneficial effects:

[0022] The application introduces Sr 0.4 Na 0.2 NbO3 into the BNT-based ferroelectric material to obtain (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3 ferroelectric film. Compared with the original component, the breakdown strength is increased by about 56%, the maximum polarization strength (P max ) is up to 102.4 muC / cm 2 , and the energy storage density is increased from 94.11 J / cm 3 .increased to 128.82 J / cm 3 , increased by about 37%. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The ferroelectric thin film made for the present application (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3:1 mol% Mn ferroelectric thin film microcapacitor structure diagram;

[0024] Figure 2 The surface particle size distribution histogram of the ferroelectric thin film made for Comparative Example 1;

[0025] Figure 3 The surface particle size distribution histogram of the ferroelectric thin film made for Example 2;

[0026] Figure 4 The frequency-dielectric property curve diagram of the ferroelectric thin film made for Examples 1-5 and Comparative Example 1;

[0027] Figure 5 The electric hysteresis loop diagram of the ferroelectric thin film made for Examples 1-5 and Comparative Example 1;

[0028] Figure 6 The breakdown strength versus coercive field comparison diagram of the ferroelectric thin film made for Examples 1-5 and Comparative Example 1;

[0029] Figure 7 The maximum polarization strength versus remanent polarization strength difference comparison diagram of the ferroelectric thin film made for Examples 1-5 and Comparative Example 1;

[0030] Figure 8 The recoverable energy storage density versus efficiency comparison diagram of the ferroelectric thin film made for Examples 1-5 and Comparative Example 1. DETAILED DESCRIPTION

[0031] The present application provides a Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric thin film, the chemical composition of the Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric thin film is: (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr0.4 Na 0.2 NbO3: 1 mol% Mn(x = 0, 0.02, 0.04, 0.06, 0.08, 0.1)。

[0032] The application also provides a Sr 0.4 Na 0.2 A preparation method of the BNT-based ferroelectric thin film doped with Na

[0033] (1) Bismuth acetate, sodium acetate, potassium acetate, zirconium acetate, barium acetate, strontium acetate and manganese acetate are weighed according to stoichiometric ratios respectively, and then dissolved in acetic acid to obtain solution A after stirring at 70 ℃ for 30 min.

[0034] (2) Acetylacetone (AcAc) and tetrabutyl titanate are added to ethylene glycol methyl ether according to stoichiometric ratios, and then stirred at 40 ℃ for 30 min to obtain solution B.

[0035] (3) Solution A and solution B are mixed, and stoichiometric amount of ethoxy niobium is added, and then stirred at 80 ℃ for 30 min and stirred at room temperature for 12 h, and then the precursor solution is obtained after filtration and aging.

[0036] (4) The precursor solution is spin-coated on a substrate with a conductive coating, and then heat treatment is performed.

[0037] (5) After the process of (4) is repeated several times to reach the target thickness, postannealing is performed to obtain the (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3 (x = 0, 0.02, 0.04, 0.06,0.08, 0.1)ferroelectric thin film.

[0038] In the application, the volume ratio of acetic acid to ethylene glycol methyl ether is 3:2;

[0039] In the step (1), the bismuth acetate, sodium acetate and potassium acetate are weighed with an excess of 10 mol%.

[0040] In the step (2), the molar ratio of tetrabutyl titanate to AcAc is 1:2.

[0041] In the application, the concentration of the precursor solution is set to 0.1-0.3 mol / L, preferably 0.25-0.3 mol / L; and the aging time is 1-7 days, preferably 1-5 days.

[0042] In the present application, the substrate with conductive coating is Pt / Ti / SiO2 / Si or LaNiO3 / SiO2 / Si, preferably Pt / Ti / SiO2 / Si; the substrate should be ultrasonically cleaned in deionized water, anhydrous ethanol and ethylene glycol at 60 ℃ for 15 min before spin coating the precursor solution; the spin coating speed is 2500-4000 r / min, preferably 3000 r / min, and the spin coating time is 30 s.

[0043] In the present application, the heat treatment is divided into three stages: the first stage is evaporation at 200 ℃ for 5 min; the second stage is pyrolysis at 400 ℃ for 5 min; and the third stage is crystallization at 700 ℃ for 5 min.

[0044] In the present application, the post-annealing process is heat preservation at 725 ℃ for 30 min.

[0045] In the present application, the (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3 ferroelectric thin film has a thickness of 100-500 nm, preferably 277 nm of the thin film with x = 0.04.

[0046] The present application also provides a Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric thin film in the preparation of energy storage capacitor, the capacitor from bottom to top is respectively: Si, SiO2, Ti, Pt, Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric thin film and Ag.

[0047] In the present application, the preparation method of the capacitor comprises the following steps:

[0048] (1) The mesh mask is cut to the appropriate size, and the mask is placed on the prepared (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2The NbO3 ferroelectric film surface is covered by a mask plate, which covers about 2 / 3 area of the film sample and leaves 1 / 3 square area, and then the ferroelectric film is fixed on the slide glass with the mask plate by using the iron fluoride tape.

[0049] (2) Turn on the total power supply of the high vacuum resistance heat evaporation coating equipment, set the default 20 DEG C of the water chiller and confirm that the refrigeration compressor is in the normal working state, and turn on the total power supply of the coating machine.

[0050] (3) Open the exhaust valve, and wait for the vacuum gauge to show 10 5 Pa, open the chamber door valve, and push open the chamber door.

[0051] (4) Put the silver particles into the molybdenum boat corresponding to the evaporation source with the rubber gloves, open the substrate baffle, loosen the two fixing screws, take off the substrate tray, fix the slide glass loaded with the ferroelectric film and the mask plate on the substrate tray, insert the substrate tray into the support slot with the front surface downward and fix it with screws, and close the substrate baffle.

[0052] (5) Close the chamber door, and tighten the chamber door fixing bolt.

[0053] (6) Close the exhaust valve, open the mechanical pump, open the pre-evacuation valve, open the molecular pump when the low vacuum pressure of the vacuum chamber is less than 5 Pa, open the main valve, and wait for the vacuum gauge to show less than 5.0*10 -4 Pa, and then perform the coating operation.

[0054] (7) Edit the coating program, and set the material parameters.

[0055] (8) Turn on the evaporation power supply, rotate the evaporation power supply current adjusting knob, slowly increase the current, wait for the film thickness instrument to show a stable value, open the substrate rotation, open the substrate baffle, set the film thickness instrument to zero, and when the preset thickness is reached, the film thickness instrument control power supply is automatically turned off; after the evaporation is completed, the capacitor is obtained.

[0056] In the present application, the size of the mask plate is 0.3-0.5 mm in radius, preferably 0.3 mm.

[0057] In the present application, the material parameters of the coating program include: material density 10.5 g / cm 3 , co-evaporation factor default 100%, Z factor 0.53, and film thickness 100 nm.

[0058] In the present application, the current is slowly increased to 2-3 Å, preferably 2.5 Å, in the film thickness instrument.

[0059] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present application:

[0060] Example 1

[0061] (1) 0.92Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.02Sr 0.4 Na 0.2 NbO3: 1 mol% Mn were weighed out in molar ratios of 1.172 g of C6H9BiO6, 0.127 g of CH3COONa, 0.149 g of CH3COOK, 0.542 g of C8H 12 O8Zr, 0.092 g of C4H6BaO4, 0.01 g of C4H6O4Sr, and 0.015 g of Mn(CH3COO)4•4H2O. Dissolved in 10.5 mL of acetic acid and stirred at 70 °C for 30 min to obtain solution A.

[0062] (2) 7 mL of ethylene glycol methyl ether was measured, 0.856 g of acetylacetone was added dropwise into the ethylene glycol methyl ether, stirred at room temperature for 1 min, then 1.438 g of tetrabutyl titanate was added dropwise into the mixed solution, stirred at 40 °C for 30 min to obtain solution B.

[0063] (3) After solution A and solution B were cooled to room temperature, solution A and solution B were mixed, then 0.038 g of ethoxy niobium was added dropwise, stirred at 80 °C for 30 min, the heating was turned off and stirred at room temperature for 12 h, filtered with a filter with a diameter of 0.22 µm and aged for 2 days to obtain 0.92Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.02Sr 0.4 Na 0.2 NbO3: 1 mol% Mn precursor solution.

[0064] (4) The Pt / Ti / SiO2 / Si(001) substrate was cut into square pieces with a side length of about 1 cm with a cutting knife, and the substrate was ultrasonically cleaned in deionized water, anhydrous ethanol, isopropanol at 60 °C for 15 min.

[0065] (5) The substrate was placed on the spin coater, the adsorption button was pressed, and the 0.92Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3O3-0.06BaTiO3-0.02Sr 0.4 Na 0.2 NbO3: 1 mol% Mn precursor solution was dropped on a Pt / Ti / SiO2 / Si(001) substrate with a rotation speed of 3000 r / min and a spin-coating time of 30 s. The wet film sample after spin-coating was transferred to a rapid thermal processing device, evaporated at 200 ℃ for 5 min, pyrolyzed at 400 ℃ for 5 min, and crystallized at 700 ℃ for 5 min.

[0066] (6) After repeating the process of (5) for 8 times, the sample was transferred to a muffle furnace and kept at 725 ℃ for 30 min to obtain a 0.92Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.02Sr 0.4 Na 0.2 NbO3: 1 mol% Mn ferroelectric thin film.

[0067] (7) An Ag electrode with a thickness of about 100 nm was evaporated on the surface of the above-mentioned ferroelectric thin film using a high-vacuum resistance thermal evaporation coating device to obtain a capacitor.

[0068] Example 2

[0069] The difference from Example 1 is that the molecular formula is 0.9Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.04Sr 0.4 Na 0.2 NbO3: 1 mol% Mn, and the thickness of the ferroelectric thin film is 277 nm.

[0070] Example 3

[0071] The difference from Example 1 is that the molecular formula is 0.88Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.06Sr 0.4 Na 0.2 NbO3: 1 mol% Mn, and the thickness of the ferroelectric thin film is 280.64 nm.

[0072] Example 4

[0073] The difference from Example 1 is that the molecular formula is 0.86Bi. 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.08Sr 0.4 Na 0.2 NbO3: 1 mol% Mn, the thickness of the ferroelectric thin film is 294.67 nm.

[0074] Example 5

[0075] The difference from Example 1 is that the molecular formula is 0.84Bi. 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.1Sr 0.4 Na 0.2 NbO3: 1 mol% Mn, the thickness of the ferroelectric thin film is 300.85 nm.

[0076] Comparative Example 1

[0077] (1) According to the molecular formula 0.94Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 The molar ratios of O3-0.06BaTiO3:1 mol% in Mn were as follows: 1.198 g of C6H9BiO6, 0.127 g of CH3COONa, 0.152 g of CH3COOK, and 0.554 g of C8H 12 O8Zr, 0.092 g of C4H6BaO4, and 0.015 g of Mn(CH3COO)4•4H2O were dissolved in 10.5 mL of acetic acid and stirred at 70 °C for 30 min to obtain solution A.

[0078] (2) Measure 7 mL of ethylene glycol methyl ether, add 0.863 g of acetylacetone to the ethylene glycol methyl ether, stir at room temperature for 1 min, then add 1.466 g of tetrabutyl titanate to the mixed solution, stir at 40 ℃ for 30 min to obtain solution B.

[0079] (3) After solution A and solution B have cooled to room temperature, they are mixed and stirred at room temperature for 12 h. After filtration, the mixture is aged for 2 days to obtain 0.94 Bi. 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3O3-0.06BaTiO3: 1 mol% Mn precursor solution.

[0080] (4) The Pt / Ti / SiO2 / Si(001) substrate is cut into square pieces with a side length of about 1 cm by a cutter, and the substrate is ultrasonically cleaned in deionized water, anhydrous ethanol and isopropanol at 60 ℃ for 15 min.

[0081] (5) The substrate is placed on a spin coater, and the adsorption button is pressed. The aged 0.94Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3: 1 mol% Mn precursor solution is added dropwise on the Pt / Ti / SiO2 / Si(001) substrate, and the rotation speed is set to 3000 r / min, and the spin coating time is 30 s. The wet film sample after spin coating is transferred to a rapid thermal processing device, evaporated at 200 ℃ for 5 min, pyrolyzed at 400 ℃ for 5 min, and crystallized at 700 ℃ for 5 min.

[0082] (6) After repeating the process of (5) for 8 times, the sample is transferred to a muffle furnace and kept at 725 ℃ for 30 min, to obtain a 0.94Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3: 1 mol% Mn ferroelectric thin film with a thickness of about 260.42 nm.

[0083] (7) A high vacuum resistance thermal evaporation coating device is used to evaporate an Ag electrode with a thickness of about 100 nm on the surface of the above-mentioned ferroelectric thin film, to obtain a capacitor.

[0084] From the above examples, the application provides a Sr 0.4 Na 0.2 NbO3 doped BNT-based ferroelectric thin film, a preparation method thereof and an application thereof in a capacitor. Figure 1 The (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3: 1 mol% Mn ferroelectric thin film micro-capacitor structure diagram can be observed from bottom to top in order of Si, SiO2, Ti, Pt, ferroelectric thin film and Ag.Figure 2 The surface grain size distribution histogram of 0.94Bi 0.5 Na 0.25 K 0.2 5Ti 0.7 Zr 0.3 O3-0.06BaTiO3ferroelectric thin film is shown. The average grain size is about 69.97 nm. Figure 3 The surface grain size distribution histogram of 0.9Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.04Sr 0.4 Na 0.2 NbO3: 1mol% Mn ferroelectric thin film is shown. The average grain size is about 38.16 nm. It is shown that the introduction of Sr 0.4 Na 0.2 NbO3can refine the grain size of the ferroelectric thin film. By analyzing Figure 4 The change trend of the dielectric constant under different proportions, we can draw some important conclusions. In examples 1-5, with the increase of the amount of Sr 0.4 Na 0.2 NbO3, the dielectric constant of the ferroelectric thin film is improved, and the tangent value of the dielectric loss angle only has a slight increase, which shows that the introduction of Sr 0.4 Na 0.2 NbO3maintains the good dielectric properties of the ferroelectric thin film. Figure 5 The surface grain size distribution histogram of (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3: 1 mol% Mn microcapacitor test obtained hysteresis loop diagram. By observing the diagram, we can see that there are differences in hysteresis behavior between different examples and the control example. Figure 6 The surface grain size distribution histogram of (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3: 1 mol% Mn ferroelectric thin film is shown. The average grain size is about 38.16 nm. It is shown that the introduction of Sr b) and coercive field (E c A comparison of the two examples. Observation clearly shows that Example 2 has a higher E... b (reaching approximately 4300 kV / cm) and relatively low E compared to other embodiments c This improvement is mainly based on two aspects: First, Sr 0.4 Na 0.2 The introduction of NbO3 induces lattice shrinkage within the ferroelectric thin film material, refining the grain size and increasing the number of grain boundaries. These grain boundaries act as barriers to prevent electron beam breakdown. Secondly, doping with SNNs can introduce small-sized polar nanoregions (PNRs) with high resistivity at their interfaces. Figure 7 The (0.94-x)Bi prepared in Examples 1-5 and Comparative Example 1 are shown. 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 A comparison graph showing the difference between the maximum polarization and the remanent polarization of the NbO3:1 mol% Mn ferroelectric thin film. This indicates that the 0.9Bi prepared in Example 2... 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-0.04Sr 0.4 Na 0.2 NbO3: 1 mol% Mn ferroelectric thin film with Sr doping 0.4 Na 0.2 NbO3 maintained a high ΔP. Through the analysis of... Figure 5 By calculating the hysteresis loop in the sample, we obtained the (0.94-x)Bi prepared in Examples 1-5 and Comparative Example 1. 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 Recoverable energy storage density (W) of NbO3:1 mol% Mn microcapacitor rec And energy storage efficiency (η). For example... Figure 8 As shown, while the energy storage efficiency decreased slightly, the energy storage density of these microcapacitors increased by 37%, reaching an astonishing 128.82 J / cm². 3 Compared to the original composition, the breakdown strength was improved by approximately 56%, and the maximum polarization intensity (P) was also increased. max) up to 102.4 μC / cm 2 , the energy storage density is increased from 94.11 J / cm 3 to 128.82 J / cm 3 , about 37%. This result shows that SNN doping is an effective means to improve the energy storage performance of BNT-based ferroelectric thin film microcapacitors. By optimizing the doping concentration of SNN, we successfully obtained excellent energy storage density. This technical breakthrough has broad development prospects in the field of future high-energy pulse power devices.

[0085] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, several improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A sodium bismuth titanate-based lead-free ferroelectric thin film, characterized by: The ferroelectric thin film material is a sodium bismuth titanate Bi 0.5 Na 0.5 TiO3 (BNT) based material, Sr 0.4 Na 0.2 NbO3 is selected as a doping component, and the chemical composition is (0.94-x) Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3, and 0.5-2 mol% of manganese is additionally doped.

2. The sodium bismuth titanate-based lead-free ferroelectric thin film according to claim 1, characterized by: (0.94-x)Bi 0.5 Na 0.25 K 0.25 Ti 0.7 Zr 0.3 O3-0.06BaTiO3-xSr 0.4 Na 0.2 NbO3thin film 0.4 Na 0.2 NbO3thin film 3. The sodium bismuth titanate-based lead-free ferroelectric thin film of claim 1, wherein: The doping amount of manganese in the thin film is 1-1.5 mol%.

4. The sodium bismuth titanate-based lead-free ferroelectric thin film of claim 1, wherein: The thickness of the thin film is 100-500 nm.

5. The sodium bismuth titanate-based lead-free ferroelectric thin film of claim 1, wherein: The thin film preparation comprises the following steps: (1) The precursor solution is prepared by sol-gel method. Bismuth acetate, sodium acetate, potassium acetate, zirconium acetate, barium acetate, strontium acetate and manganese acetate are weighed according to the stoichiometric ratio respectively, and then dissolved in acetic acid. Stirring at 70-80 ℃ for 30-120 min to obtain solution A. (2) According to the stoichiometric ratio, acetylacetone (AcAc) and tetrabutyl titanate are added to ethylene glycol methyl ether, and stirred at 40-50 ℃ for 30-60 min to obtain solution B. (3) Mix solution A and solution B, add stoichiometric amount of ethoxy niobium, stir at 70-80 ℃ for 30-120 min, then stir at room temperature for 12 h, filter and age to obtain the precursor solution. (4) Spin coating the precursor solution on the substrate with conductive coating, and then heat treatment. (5) Repeat the process of (4) several times to reach the target thickness, then perform post annealing to obtain the required ferroelectric thin film.

6. The method of claim 5, wherein the method further comprises: The volume ratio of acetic acid to ethylene glycol methyl ether is 3:1.8-2.5, in step (1), the excess amount of bismuth acetate, sodium acetate and potassium acetate is 10-12 mol%, in step (2), the molar ratio of tetrabutyl titanate to AcAc is 1:2-3.

7. The method of claim 5, wherein the method further comprises: The concentration of the precursor solution is set to 0.15-0.3 mol / L.

8. The method of claim 5, wherein the method further comprises: The aging time of the precursor solution is 1-7 days.

9. The method of claim 5, wherein the method further comprises: The heat treatment is divided into three stages: the first stage is evaporation at 200-250 ℃ for 3-5 min, the second stage is pyrolysis at 350-450 ℃ for 3-5 min, and the third stage is crystallization at 650-730 ℃ for 3-5 min. The post annealing process is to keep the temperature at 700-730 ℃ for 25-60 min.

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