A sodium bismuth titanate-based relaxor ferroelectric ceramic and a preparation method thereof

Abstract

This invention relates to the field of relaxor ferroelectric ceramic dielectric energy storage materials, specifically to a sodium bismuth titanate-based relaxor ferroelectric ceramic and its preparation method, wherein the chemical composition of the sodium bismuth titanate-based relaxor ferroelectric ceramic is (1-x)BNLT. ‑x BAN, of which BNLT is 0.9Bi 0.5 Na 0.5 TiO3-0.1Bi 0.5 Li 0.5 TiO3, BAN is BaAl 0.5 Nb 0.5 The value of O3 and x ranges from 0.06 to 0.18. When x = 0.15, the ceramic exhibits excellent performance with a recoverable energy storage density (Wrec) of not less than 14.0 J / cm³ and an energy storage efficiency (η) of not less than 84% under an electric field of 775 kV / cm. This invention employs a solid-state reaction sintering process, which is simple to prepare and low in cost, making it suitable for high-performance energy storage capacitors in pulsed power systems.

Description

Technical Field

[0001] This invention relates to the field of relaxor ferroelectric ceramic dielectric energy storage materials, specifically to a sodium bismuth titanate-based relaxor ferroelectric ceramic and its preparation method. Background Technology

[0002] In pulsed power systems, dielectric capacitors need to combine high power density and fast charge / discharge capabilities. However, traditional dielectric materials face the challenge of synergistically optimizing breakdown field strength (Eb), maximum polarization (Pm), and remanent polarization (Pr). Existing strategies such as polar nanodomains and defect engineering can improve relaxation characteristics, but they are often accompanied by a significant decrease in Pm, making it difficult to simultaneously achieve high recoverable energy density (Wrec) and energy storage efficiency (η). Pure Bi 0.5 Na 0.5 TiO3 ceramics possess high local polarity due to the lone pair electron effect of Bi³⁺, but the volatilization of Bi₂O₃ during sintering leads to an increase in oxygen vacancies, reducing resistivity and Eb, thus limiting their practical applications. Summary of the Invention

[0003] To address the shortcomings of the existing technologies, the present invention aims to provide a sodium bismuth titanate-based relaxor ferroelectric ceramic and its preparation method, overcoming the problems of low breakdown field strength and difficulty in simultaneously achieving energy density and efficiency in existing relaxor ferroelectric ceramics. This invention fully considers the intrinsic characteristics of different ions (such as ionic polarity and radius), as well as the band gap and sinterability of different components. Through chemical modification to induce local structural distortion, multiphase nanodomain coexistence, and oxygen vacancy suppression, a high recoverable energy density W is achieved. rec High energy storage efficiency η and excellent overall performance.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A sodium bismuth titanate-based relaxor ferroelectric ceramic, the chemical composition of which is represented by the following general formula: (1-x)BNLT - x BAN, of which BNLT is 0.9Bi 0.5 Na 0.5 TiO3-0.1Bi 0.5 Li 0.5 TiO3, BAN is BaAl 0.5 Nb 0.5 O3, the range of x is 0.06≤x≤0.18.

[0005] In a preferred embodiment of the present invention, the value of x is in the range of 0.12≤x≤0.15.

[0006] In a preferred embodiment of the present invention, when x=0.15, the recoverable energy storage density Wrec of the ceramic under an electric field of 775kV / cm is not less than 14.0 J / cm³, and the energy storage efficiency η is not less than 84%.

[0007] A method for preparing a sodium bismuth titanate-based relaxor ferroelectric ceramic includes the following steps: Bi2O3, Na2CO3, Li2CO3, BaCO3, Al2O3, Nb2O5 and TiO2 were used as raw materials and subjected to a first ball milling and mixing in a solvent to obtain a mixture.

[0008] The mixture was calcined to obtain precursor powder.

[0009] The precursor powder was ball-milled a second time, and a binder was added for granulation and sieving.

[0010] The granulated and sieved powder is pressed into a green body, and after debinding, it is sintered to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

[0011] In a preferred embodiment of the present invention, in the first ball milling, the solvent is ethanol, the mass-to-volume ratio of solvent to raw material is 1-1.5 mL / g, the rotation speed is 300-500 rpm, and the time is 12-24 h; in the second ball milling, the rotation speed is 300-650 rpm, and the time is 12-16 h.

[0012] In a preferred embodiment of the present invention, the calcination time is 2-4 hours, the calcination temperature is 750-900℃, and the calcination heating rate is 4-6℃ / min.

[0013] In a preferred embodiment of the present invention, the binder is a polyvinyl alcohol aqueous solution with a mass fraction of 3%-5%, and the mass ratio of the binder (based on PVA dry material) to the precursor powder is 1:5-15; after granulation, it passes through a 300-400 mesh sieve.

[0014] In a preferred embodiment of the present invention, the diameter of the green body is 10 mm; the debinding temperature is 500-600℃, the debinding time is 2-3 h, and the debinding heating rate is 3-5℃ / min.

[0015] In a preferred embodiment of the present invention, the sintering time is 2-3 hours, the sintering temperature is 1150-1180°C, and the sintering heating rate is 4-6°C / min.

[0016] (1-x) BNLT -xThe performance breakthrough of the BAN series is achieved through a triple synergistic strategy of "local structural distortion - coexistence of multiphase nanodomains - oxygen vacancy suppression," which solves the problems of "high polarization but high loss" in pure BNLT and "low stability and low E" in traditional BaTiO3-based ceramics. b The core pain point: ionic radius mismatch (Ba 2+ / Li + Inducing lattice distortion and enhancing unit cell polarizability; multi-element doping (Al) 3+ / Nb 5+ Disrupting long-range order to form 3-8nm PNRs reduces hysteresis loss; Nb 5+ Suppressing oxygen vacancies and refining grains improves insulation, breaking through E b Bottleneck; where x=0.15 is the optimal doping ratio to achieve W rec E b A perfect balance with stability.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. The sodium bismuth titanate-based relaxor ferroelectric ceramic of the present invention, by introducing BaAl... 0.5 Nb 0.5 O3 (BAN) vs. 0.9Bi 0.5 Na 0.5 TiO3-0.1Bi 0.5 Li 0.5 Chemical modification of the TiO3 (BNLT) matrix to achieve Ba 2+ Al 3+ 、Nb 5+ The synergistic doping modification effect of multiple elements, the introduction of the above ions effectively regulates lattice distortion, induces the formation of multi-scale polar nanodomains, enhances the relaxation characteristics of the material, and reduces residual polarization; appropriate proportion of BAN doping helps to suppress the formation of oxygen vacancies during sintering, and improves the resistivity and breakdown field strength of the material.

[0018] 2. The sodium bismuth titanate-based relaxor ferroelectric ceramic of the present invention achieves a synergistic balance of high polarization intensity, high breakdown field strength and strong relaxation characteristics by optimizing the doping amount (x value) of BAN, thereby enabling the material to simultaneously obtain high recoverable energy storage density and high energy storage efficiency.

[0019] 3. The preparation method of the sodium bismuth titanate-based relaxor ferroelectric ceramic of the present invention adopts a mature and controllable solid-state reaction sintering process, which does not require complex equipment, has low process cost, and is easy to achieve large-scale preparation. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the sodium bismuth titanate-based relaxor ferroelectric ceramic prepared in Example 1.

[0021] Figure 2 This is a SEM image of the sodium bismuth titanate-based relaxor ferroelectric ceramic of Example 1.

[0022] Figure 3 This is the single-stage energy storage loop of the sodium bismuth titanate-based relaxor ferroelectric ceramic of Example 1.

[0023] Figure 4 The total energy storage density (W) of the sodium bismuth titanate-based relaxor ferroelectric ceramic of Example 1 under different electric field strengths. total Effective energy storage density (W) rec ) and energy storage efficiency (ƞ). Detailed Implementation

[0024] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0026] Example 1: x = 0.15 (1) Press (1- x BNLT- x BAN ( x =0.15) Weigh out 21.87 g of Bi2O3, 5.26 g of Na2CO3, 0.72 g of Li2CO3, 3.28 g of BaCO3, 1.31 g of Al2O3, 4.85 g of Nb2O5, and 10.68 g of TiO2, with a weighing error within ± 0.0005 g. Pour the weighed raw materials into a ball mill jar, mix with alcohol, and ball mill for 12 h to obtain a mixture.

[0027] (2) The mixture was then dried at 100 °C for 3 h and calcined at 780 °C for 3 h to form a precursor.

[0028] (3) Then, the precursor powder was added to 0.5 wt.% PVA binder, ground and granulated, and formed into a sheet-like preform with a diameter of 10 mm and a thickness of 1 mm under a pressure of 6 MPa. The preform was covered with powder of the same composition to prevent Bi volatilization, placed in a crucible, heated to 550℃ at 5℃ / min and held for 2.5 h to remove the binder, and then sintered at 1080℃ for 2 h at the same rate to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

[0029] Example 2: x = 0.18 (1) The raw material proportioning is the same as in Example 1, except that the ceramic material composition is: (1- x BNLT- x BAN x = 0.18), the weighing error is within ± 0.0005 grams. Pour the weighed raw materials into a ball mill jar, mix with alcohol and ball mill for 12 hours to obtain a mixture.

[0030] (2) The mixture was then dried at 100°C for 3 h and calcined at 780°C for 3 h to form a precursor.

[0031] (3) Then, the precursor powder was added to 0.5 wt.% PVA binder, ground and granulated, and formed into a sheet-like preform with a diameter of 10 mm and a thickness of 1 mm under a pressure of 6 MPa. The preform was covered with powder of the same composition to prevent Bi volatilization, placed in a crucible, heated to 550℃ at 5℃ / min and held for 2.5 h to remove the binder, and then sintered at 1080℃ for 2 h at the same rate to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

[0032] Example 3: x =0.12 (1) The raw material proportioning is the same as in Example 1, except that the ceramic material composition is: (1- x BNLT- x BAN x =0.12), the weighing error is within ± 0.0005 grams. Pour the weighed raw materials into a ball mill jar, mix with alcohol and ball mill for 12 hours to obtain a mixture.

[0033] (2) The mixture is then dried at 100°C for 3 h and calcined at 780°C for 3 h to form a precursor.

[0034] (3) Then, the precursor powder was added to 0.5 wt.% PVA binder, ground and granulated, and formed into a sheet-like preform with a diameter of 10 mm and a thickness of 1 mm under a pressure of 6 MPa. The preform was covered with powder of the same composition to prevent Bi volatilization, placed in a crucible, heated to 550℃ at 5℃ / min and held for 2.5 h to remove the binder, and then sintered at 1080℃ for 2 h at the same rate to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

[0035] Example 4: x =0.06 (1) The raw material proportioning is the same as in Example 1, except that the ceramic material composition is: (1- x BNLT- x BAN x =0.06), the weighing error is within ± 0.0005 grams. Pour the weighed raw materials into a ball mill jar, mix with alcohol and ball mill for 12 hours to obtain a mixture.

[0036] (2) The mixture was then dried at 100°C for 3 h and calcined at 780°C for 3 h to form a precursor.

[0037] (3) Then, the precursor powder was added to 0.5 wt.% PVA binder, ground and granulated, and formed into a sheet-like preform with a diameter of 10 mm and a thickness of 1 mm under a pressure of 6 MPa. The preform was covered with powder of the same composition to prevent Bi volatilization, placed in a crucible, heated to 550℃ at 5℃ / min and held for 2.5 h to remove the binder, and then sintered at 1080℃ for 2 h at the same rate to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

[0038] Comparative Example 1: x =0 (pure BNLT) (1) The raw material proportioning is the same as in Example 1, except that the ceramic material composition is: (1- x BNLT- x BAN ( x =0), the weighing error is within ± 0.0005 grams. Pour the weighed raw materials into a ball mill jar, mix with alcohol and ball mill for 12 hours to obtain a mixture.

[0039] (2) The mixture is then dried at 100°C for 3 h and calcined at 780°C for 3 h to form a precursor.

[0040] (3) Then, the precursor powder was added to 0.5 wt.% PVA binder and ground into granules, and formed into a sheet-like preform with a diameter of 10 mm and a thickness of 1 mm under a pressure of 6 MPa. The preform was covered with powder of the same composition to prevent Bi volatilization, and placed in a crucible. The temperature was first increased to 550℃ at 5℃ / min and held for 2.5 h to remove the binder. Then, the temperature was increased to 1080℃ at the same rate and sintered for 2 h to obtain pure BNLT.

[0041] Comparative Example 2 Commercially available BaTiO3 powder was sintered at 1250 °C for 2 h to obtain traditional BaTiO3-based ceramics.

[0042] Results Analysis Figure 1 (XRD) verifies the successful formation and lattice distortion of the perovskite solid solution, providing a structural basis for improving energy storage performance; Figure 2 (SEM) confirms the high density and uniform grain distribution of the ceramic, ensuring a high breakdown field strength; Figure 3 (energy storage loop) shows the excellent polarization characteristics of "high Pm + low Pr", which is the core prerequisite for high energy storage density and efficiency. Figure 4 (electric field dependence curve) quantifies the optimal energy storage performance (14.21 J / cm²). 3 (84.28%), verifying the application potential of this ceramic under high electric fields.

[0043] The fundamental difference between pure BNLT and traditional BaTiO3-based ceramics lies in the fact that pure BNLT possesses long-range ferroelectric order and high oxygen vacancies, resulting in "high polarization but low efficiency and low E2O3". b "Unable to meet pulse power requirements; traditional BaTiO3-based ceramics suffer from low structural control flexibility and poor stability, W" rec E b All are at low levels; (1-x) BNLT -x BAN achieves superior performance across the board by simultaneously optimizing polarization, loss, and insulation through multi-scale structural engineering, thus verifying the advanced nature and universality of this design strategy.

[0044] Overall results show that through the synergistic strategy of "BAN doping-induced lattice distortion + multiphase nanodomain regulation + oxygen vacancy suppression", this (1-x)BNLT -x BAN relaxor ferroelectric ceramics have successfully overcome the performance bottlenecks of traditional materials, possessing excellent comprehensive energy storage performance, and fully meeting the application requirements of pulse power systems for dielectric capacitors.

[0045] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0046] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A sodium bismuth titanate-based relaxor ferroelectric ceramic, characterized in that, The chemical composition of the ceramic is represented by the following general formula: (1-x)BNLT -x BAN, of which BNLT is 0.9Bi 0.5 Na 0.5 TiO3-0.1Bi 0.5 Li 0.5 TiO3, BAN is BaAl 0.5 Nb 0.5 O3, the range of x is 0.06≤x≤0.

18.

2. The sodium bismuth titanate-based relaxor ferroelectric ceramic according to claim 1, characterized in that, The value of x is in the range of 0.12 ≤ x ≤ 0.

15.

3. The sodium bismuth titanate-based relaxor ferroelectric ceramic according to claim 1, characterized in that, When x=0.15, the recoverable energy storage density W of the ceramic under an electric field of 775kV / cm is... rec Not less than 14.0 J / cm³, and energy storage efficiency η not less than 84%.

4. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 1, characterized in that, Includes the following steps: Bi2O3, Na2CO3, Li2CO3, BaCO3, Al2O3, Nb2O5 and TiO2 were used as raw materials and subjected to a first ball milling and mixing in a solvent to obtain a mixture; The mixture was calcined to obtain precursor powder; The precursor powder is subjected to a second ball milling, and a binder is added for granulation and sieving. The granulated and sieved powder is pressed into a green body, and after debinding, it is sintered to obtain sodium bismuth titanate-based relaxor ferroelectric ceramic.

5. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 4, characterized in that, In the first ball milling, the solvent was ethanol, the mass-to-volume ratio of solvent to raw material was 1-1.5 mL / g, the rotation speed was 300-500 rpm, and the time was 12-24 h; in the second ball milling, the rotation speed was 300-650 rpm, and the time was 12-16 h.

6. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 4, characterized in that, The calcination time is 2-4 hours, the calcination temperature is 750-900℃, and the calcination heating rate is 4-6℃ / min.

7. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 4, characterized in that, The binder is an aqueous solution of polyvinyl alcohol, with a mass fraction of 3%-5%, and the mass ratio of binder to precursor powder is 1:5-15; after granulation, it passes through a 300-400 mesh sieve.

8. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 4, characterized in that, The diameter of the green body is 10mm; the debinding temperature is 500-600℃, the debinding time is 2-3h, and the debinding heating rate is 3-5℃ / min.

9. The method for preparing sodium bismuth titanate-based relaxor ferroelectric ceramics according to claim 4, characterized in that, The sintering time is 2-3 hours, the sintering temperature is 1150-1180℃, and the sintering heating rate is 4-6℃ / min.

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