Sodium bismuth titanate-based ceramic with excellent temperature stability and preparation method thereof

Abstract

The invention discloses sodium bismuth titanate-based ceramic with excellent temperature stability and a preparation method of the sodium bismuth titanate-based ceramic, and belongs to the technical field of inorganic materials. The chemical formula of the sodium bismuth titanate-based ceramic provided by the invention is 0.96 [Bi < 0.5 > (Na < 0.82 > K < 0.18 >) < 0.5 >] < 1-x > La < x > (Ti < 1-y > Nb < y >) O < 3-0.04 > SrTiO3, x is 0.003-0.02, and y is 0.003-0.02. Nb < 5 + > and La < 3 + > ions are introduced into the sodium bismuth titanate-based ceramic, a traversal relaxation state can be induced at room temperature through component regulation and control, a defect dipole is formed at the same time, and through combination of a traversal relaxation state-ferroelectric phase change mechanism and an electrostrictive bending strain effect induced by the defect dipole, the defect dipole-induced electrostrictive relaxation state-ferroelectric phase change mechanism is formed. The electrostrictive strain performance of the sodium bismuth titanate-based ceramic is effectively improved, and the sodium bismuth titanate-based ceramic has a good application prospect in preparation of aerospace parts, new energy equipment or industrial control equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic materials, and in particular relates to a sodium bismuth titanate-based ceramic with excellent temperature stability and a preparation method thereof. Background Art

[0002] For (Bi 0.5 Na 0.5 )TiO3(BNT) based relaxor ferroelectric ceramics face a key challenge in temperature stability, which is usually higher than the relaxor-ferroelectric phase transition temperature (T f-r ), the response ability of the polar nano-regions (PNRs) of BNT-based materials weakens, resulting in electrostrain attenuation. This characteristic conflicts with the demand for stable strain output in high-temperature environments of actual applications (such as aerospace devices, new energy equipment, and industrial control equipment). Strain fluctuations under thermal shock will directly affect the displacement accuracy, driving force stability, and service life of the device, seriously restricting the engineering application of BNT-based ceramic materials under high-temperature and complex working conditions. How to break through the limitation of phase transition temperature on the electrostrain of BNT-based materials and achieve stable large strain output in a wide temperature range has become the core technical bottleneck that drives it from the laboratory to actual devices. Summary of the Invention

[0003] In order to overcome at least one of the problems existing in the above-mentioned prior art, one of the purposes of the present invention is to provide a sodium bismuth titanate-based ceramic by introducing Nb 5+ and La 3+ ions, and induced ergodic relaxation states at room temperature by component regulation, which expanded the electrostrain properties of BNT-based materials at high temperatures.

[0004] A second object of the present invention is to provide a method for preparing the above-mentioned sodium bismuth titanate-based ceramics.

[0005] A third object of the present invention is to provide an application of the above-mentioned sodium bismuth titanate-based ceramic.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a sodium bismuth titanate-based ceramic, wherein the chemical formula of the sodium bismuth titanate-based ceramic is 0.96[Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ] 1-x La x (Ti 1-y Nb y )O3-0.04SrTiO3, x is 0.003~0.02, y is 0.003~0.02.

[0008] The present invention is 0.96 (0.82BNT-0.18BKT)-0.04ST (0.96Bi 0.5 (Na 0.82 K 0.18 ) 0.5 Nb is introduced into the TiO3-0.04SrTiO3) matrix component 5+ and La 3+ ions, induced ergodic relaxation state at room temperature by composition regulation, and formed and Three defect dipoles, the sodium bismuth titanate-based ceramic has large electrostrain at room temperature and good strain stability in a wide temperature range, and still maintains excellent fatigue resistance and low strain hysteresis in high temperature environment.

[0009] In the present invention, the values ​​of x and y are independent of each other and can be the same or different. In some embodiments of the present invention, the values ​​of x and y are the same.

[0010] In some embodiments of the present invention, x is any one of 0.003, 0.005, 0.008, 0.01, 0.015 or 0.02, or a range of any two thereof.

[0011] In some embodiments of the present invention, y is any value of 0.003, 0.005, 0.008, 0.01, 0.015 or 0.02, or a range of values ​​therebetween.

[0012] In some embodiments of the present invention, the sodium bismuth titanate-based ceramic includes a textured sodium bismuth titanate-based ceramic or a non-textured sodium bismuth titanate-based ceramic; in some preferred embodiments of the present invention, the sodium bismuth titanate-based ceramic is selected from textured sodium bismuth titanate-based ceramic.

[0013] Both textured and non-textured sodium bismuth titanate-based ceramics of the present invention exhibit low dielectric loss and high electrostrain response. Furthermore, compared to non-textured ceramics, the textured ceramics of the present invention exhibit superior strain stability over a wide temperature range, maintaining superior fatigue resistance and lower strain hysteresis even at high temperatures.

[0014] In some embodiments of the present invention, the ceramic grains of the textured sodium bismuth titanate-based ceramics are arranged along <001> orientation.

[0015] In some embodiments of the present invention, the ceramic grain orientation degree of the textured sodium bismuth titanate-based ceramic is ≥80%; more specifically 80-95%; for example, it can be any value among 80%, 85%, 90% or 95% or any range between the two.

[0016] In some embodiments of the present invention, the average particle size of the ceramic grains of the sodium bismuth titanate-based ceramic is 1 to 5 μm; for example, it can be any value among 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, or a range between any two values.

[0017] In some embodiments of the present invention, the thickness of the sodium bismuth titanate-based ceramic is 0.1 to 1 mm; for example, it can be any value among 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or 1 mm, or a range between any two values.

[0018] The sodium bismuth titanate-based ceramic of the present invention has more excellent electrostrain response performance within a specific thickness range and exhibits better temperature stability and high-temperature strain performance.

[0019] The second aspect of the present invention provides a method for preparing the sodium bismuth titanate-based ceramics described in the first aspect of the present invention, comprising the following steps: according to the chemical formula of the sodium bismuth titanate-based ceramics, measuring the raw materials of each component in a stoichiometric ratio, and preparing the sodium bismuth titanate-based ceramics by a reaction template grain growth method or a solid phase method.

[0020] In some embodiments of the present invention, the textured sodium bismuth titanate-based ceramic is prepared by the reaction template grain growth method; and the non-textured sodium bismuth titanate-based ceramic is prepared by the solid phase method.

[0021] In some embodiments of the present invention, the reaction template grain growth method is specifically as follows: bismuth titanate template crystals are prepared through a molten salt system; according to the chemical formula of the sodium bismuth titanate-based ceramic, oxides or carbonates containing various elements are measured and mixed with the bismuth titanate template crystals, additives and solvents to obtain a ceramic slurry, and the reaction template grain growth method is used to tape-cast the ceramic slurry through a tape-casting process to obtain a single-layer tape-cast film, the single-layer tape-cast film is stacked to obtain a tape-cast green body, and the tape-cast green body is sequentially subjected to hot pressing, isostatic pressing, debinding and sintering to obtain the sodium bismuth titanate-based ceramic.

[0022] In some embodiments of the present invention, in the reaction template grain growth method, the height of the casting scraper in the casting process is 100 to 200 μm, for example, it can be 100 μm, 150 μm or 200 μm, etc.; the casting film belt speed is 0.5 to 2 cm / s, for example, it can be 0.5 cm / s, 1 cm / s, 1.5 cm / s or 2 cm / s, etc.; the casting machine temperature is 50 to 60°C, for example, it can be 50°C, 55°C or 60°C, etc.

[0023] By controlling the specific tape casting process, especially the tape casting scraper height, tape casting film belt speed and tape casting machine temperature, a tape casting film with more uniform thickness and better mechanical properties can be obtained, thereby ensuring the acquisition of sodium bismuth titanate-based ceramics with better and more stable performance.

[0024] In some embodiments of the present invention, in the reaction template grain growth method, the sintering temperature is 1100-1200°C, for example, it can be 1100°C, 1150°C or 1200°C; the sintering time is 4-7h, for example, it can be 4h, 5h, 6h or 7h.

[0025] In some embodiments of the present invention, the solid phase method is specifically as follows: according to the chemical formula of the sodium bismuth titanate-based ceramic, the oxides or carbonates containing each element are measured, and the ceramic is obtained by sequentially subjecting the ceramic to primary ball milling, pre-sintering, secondary ball milling, granulation, tableting, debinding and sintering.

[0026] In some embodiments of the present invention, in the solid phase method, the sintering temperature is 1100-1200°C, for example, 1100°C, 1150°C or 1200°C; the sintering time is 2-5h, for example, 2h, 3h, 4h or 5h.

[0027] The third aspect of the present invention provides an application of the sodium bismuth titanate-based ceramics described in the first aspect of the present invention in the preparation of aerospace devices, new energy equipment or industrial control equipment.

[0028] The beneficial effects of the present invention are: the present invention introduces Nb into sodium bismuth titanate-based ceramics 5+ and La 3+ ions can induce ergodic relaxation states at room temperature by controlling the composition, and at the same time form defect dipoles. By combining the ergodic relaxation state-ferroelectric phase transition mechanism and the electro-bending strain effect induced by the defect dipoles, the electro-strain properties of sodium bismuth titanate-based ceramics are effectively improved. It has good application prospects in the preparation of aerospace devices, new energy equipment or industrial control equipment.

[0029] Furthermore, the present invention texturizes the sodium bismuth titanate-based ceramic, which can effectively improve its electrostrain performance and exhibit good temperature stability and high-temperature strain performance over a wide temperature range, providing a new implementation path for the design of piezoelectric materials serving in high-temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart for preparing the non-textured sodium bismuth titanate-based ceramics in Example 1.

[0031] Figure 2 This is a flow chart for preparing template seed crystals synthesized by the molten salt method in Example 2.

[0032] Figure 3 This is a flow chart for preparing textured sodium bismuth titanate-based ceramics by the tape casting method in Example 2.

[0033] Figure 4 Schematic diagram of strain hysteresis calculation in an embodiment of the present invention.

[0034] Figure 5 These are SEM images of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1.

[0035] Figure 6 These are the XRD patterns of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1.

[0036] Figure 7 The dielectric temperature spectra of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1 at 1 kHz.

[0037] Figure 8 These are the hysteresis loops of the non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1.

[0038] Figure 9 Example 1 Bipolar strain curves and unipolar strain curves of non-textured sodium bismuth titanate-based ceramics with different compositions.

[0039] Figure 10 This is the electrostrain performance of the BNKST-8LaNb non-textured ceramic in Example 1.

[0040] Figure 11 These are the XRD patterns and cross-sectional SEM images of the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm in Example 2.

[0041] Figure 12 The dielectric temperature spectra of the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm in Example 2 at different frequencies.

[0042] Figure 13 This is the electrostrain performance of the 0.22 mm thick BNKST-8LaNb textured ceramic at 25°C in Example 2.

[0043] Figure 14 The electrostrain temperature stability of the BNKST-8LaNb non-textured ceramic in Example 1 and the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm in Example 2.

[0044] Figure 15 This is the electrostrain performance of the 0.22 mm thick BNKST-8LaNb textured ceramic at 200°C in Example 2.

[0045] Figure 16This is the fatigue resistance of the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm at 200°C in Example 2. DETAILED DESCRIPTION

[0046] The present invention will be described in further detail below by way of specific examples. It should be understood that the following examples are only intended to further illustrate the present invention and are not to be construed as limiting the scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth herein all fall within the scope of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description of the present invention, rather than being limited to the specific data exemplified below. The raw materials, reagents, or devices used in the following examples and comparative examples, unless otherwise specified, can be obtained from conventional commercial sources or can be obtained by existing known methods.

[0047] In the present invention, the ergodic relaxation state is a state between the ferroelectric and paraelectric phases, characterized by a nonlinear relationship between polarization intensity and electric field, and the polarization intensity cannot be completely restored to the initial state after the electric field is removed.

[0048] Remanent polarization intensity (P r ) is the polarization strength that a ferroelectric / piezoelectric material can maintain after the external electric field is removed.

[0049] Coercive field (E c ) is the minimum electric field strength required to flip a material from one polarization state to another.

[0050] Example 1

[0051] A non-textured sodium bismuth titanate-based ceramic 0.96[Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ] 1-x La x (Ti 1-y Nb y )O3-0.04SrTiO3 (non-textured BNKST-1000xLaNb, x=y=0.003, 0.005, 0.008, 0.01, 0.015 or 0.02) was prepared by traditional solid phase method, as shown in the flow chart. Figure 1 The specific steps are as follows:

[0052] The raw material powders (containing oxides or carbonates of the corresponding elements) were weighed according to the stoichiometric ratio of the non-textured sodium bismuth titanate-based ceramic formula and placed in a ball mill with a ball-to-powder ratio of 3:1. The milling medium was alcohol, the milling speed was 300 rpm, and the milling time was set to 12 hours. After ball milling, the powders were transferred to a porcelain plate and dried in an oven. After drying, they were screened through a 60-mesh sieve to ensure uniform dispersion. The dried raw material powders were transferred to a crucible and pre-calcined in a muffle furnace at a temperature of 5°C / min to 850°C for 3 hours. The calcined powders were then subjected to a second ball milling to improve powder uniformity, using the same milling parameters as the first milling. The calcined powders were then granulated with a 6wt% PVB solution (5% by weight of the powder mass). The powders were thoroughly ground to ensure uniform contact between the PVB and the powder, resulting in well-flowing and uniform granules. The pellets were then pressed into shape. An appropriate amount of granulation powder was weighed into a mold and initially formed by holding the pressure at 20 MPa for 30 seconds to obtain a circular green body with a diameter of 10 mm and a thickness of 1 mm. After vacuum packaging, cold isostatic pressing was performed, applying a pressure of 200 MPa and holding the pressure for 5 minutes to increase the density of the green body. The binder was then removed in a muffle furnace to remove the PVB added during the granulation process. The binder removal process was to increase the temperature to 500°C at a rate of 1°C / min and hold the temperature for 2 hours. Sintering is an important step in the formation of green bodies into porcelain. In order to reduce the volatilization of alkali metal elements during the sintering process, a powder-buried sintering method was adopted. The sintering was carried out at 1165°C for 3 hours to obtain non-textured sodium bismuth titanate-based ceramics with a thickness of 0.32 to 0.42 mm.

[0053] To facilitate subsequent electrical performance testing, a layer of silver paste was evenly applied to the upper and lower surfaces of the sintered ceramic using a screen printer. After being held at 720°C for 15 minutes, two silver electrodes were formed. Some electrical performance tests (such as dielectric, ferroelectric, and strain) are typically performed after electric field polarization at 5 kV / mm for 20-30 minutes.

[0054] In this example, different La 3+ Doping amount (x) and Nb 5+ Non-textured sodium bismuth titanate-based ceramics with a doping amount (y), wherein 0.96[Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ] 0.992 La 0.008 (Ti 0.992 Nb 0.008 )O3-0.04SrTiO3 is recorded as BNKST-8LaNb non-textured ceramics.

[0055] Example 2

[0056] A textured sodium bismuth titanate-based ceramic 0.96[Bi 0.5 (Na 0.82K 0.18 ) 0.5 ] 1-x La x (Ti 1-y Nb y )O3-0.04SrTiO3 (texture BNKST-1000xLaNb, x=y=0.003, 0.005, 0.008, 0.01, 0.015 or 0.02) was prepared by a reaction template grain growth method, and the specific steps are as follows:

[0057] The first step is to synthesize the flake template seed crystal. The preparation flow chart of the template seed crystal synthesized by the molten salt method is as follows: Figure 2 The specific steps are as follows:

[0058] The molten salt system used was a KCl-NaCl system, with a molar ratio of KCl to NaCl of 1.06:1, a molar ratio of Bi2O3 to TiO2 of 2:3, and a 3wt% excess of Bi2O3. The mass ratio of the raw material powder to the molten salt was 1.5:1. The molten salt and raw material powder were weighed proportionally and placed in a ball mill for 9 hours at a speed of 300 r / min. The seed crystal calcination system was 1100°C for 2 hours, with a heating rate of 5°C / min and a cooling rate of 3°C / min. After Bi2O3 and TiO2 fully reacted and grew in the molten salt, flaky Bi4Ti3O was obtained. 12 Seed crystals. Then use deionized water to wash several times to remove salt. The washing process requires heating and stirring to fully dissolve the salt. After drying, pure Bi4Ti3O 12 Seed crystal. The reaction equation is as follows:

[0059] 2Bi2O3+TiO2→Bi4Ti3O 12 (1)

[0060] The second step is to prepare textured sodium bismuth titanate-based ceramics by tape casting. The preparation flow chart is as follows: Figure 3 The specific steps are as follows:

[0061] The corresponding oxides or carbonates were weighed in a ball mill according to the stoichiometric ratio of the chemical formula of the textured sodium bismuth titanate-based ceramic. 4.5% dibutyl phthalate (DBP) as a plasticizer, 4.5% polyethylene glycol (PEG) as a dispersant, and 1% castor oil as a dispersant were added. Ethanol was added and the mixture was ball milled at 400 rpm for 4 hours. Then, 9% polyvinyl butyral (PVB) was added as a binder and the mixture was ball milled at 300 rpm for 12 hours. The total content of the glue was 18.5% of the total mass of the raw material powder and glue. After ball milling, Bi4Ti3O 12The seed crystals were mixed on a magnetic stirrer at a speed of 300 r / min for 2 hours. Then the mixture was transferred to a vacuum degassing machine, and the bubbles and a small amount of alcohol in the slurry were removed by vacuum while stirring, and finally a casting slurry with suitable viscosity, uniformity and no bubbles was obtained. The casting slurry after degassing was transferred to a casting machine and formed by a casting method to obtain a uniformly dispersed green sheet. Then, the textured sodium bismuth titanate-based ceramics were obtained through lamination, hot pressing, isostatic pressing, debinding, sintering and other processes. The thickness of the textured sodium bismuth titanate-based ceramics was 0.22 mm, 0.3 mm, 0.41 mm or 0.5 mm, respectively.

[0062] During the casting process, parameters such as the casting tape speed, the height of the scraper, and the temperature of the casting machine must be strictly controlled. These parameters, combined with the appropriate slurry viscosity, can produce qualified cast films. If the casting film tape speed is too fast, the casting slurry with a certain viscosity will not be able to fully expand under the action of the scraper shear force, resulting in uneven thickness of the cast film; if the casting film tape speed is too slow, the slurry may solidify due to staying on the film tape for too long, resulting in scratches and unevenness of the cast film. The height of the scraper is also a key parameter that directly determines the thickness of the film. The height of the scraper should be adjusted according to the viscosity of the slurry. If the scraper height is too low, the obtained film is thin, but the toughness is low, which will cause difficulties in subsequent lamination processes; if the scraper height is too high, it may cause the seed crystals to be poorly arranged under the scraper shear force. The heating temperature of the casting machine is also a critical parameter. If the temperature is too high, the organic solvent on the cast film will evaporate too quickly, resulting in problems such as low toughness and cracking of the cast film. The specific casting process and parameters in this case are as follows:

[0063] The mixed slurry is introduced into the slurry tank of the casting machine. The casting scraper height is adjusted to 150μm, the casting film speed is 1cm / s, and the casting machine temperature is set to 55°C. Under the uniform rotation of the casting base belt and the shear force of the scraper, the randomly arranged flake seed crystals in the slurry are oriented along the direction of the shear force, resulting in a uniform and flat single-layer cast film after drying. The cast film is cut into 6cm×6cm squares and laminated. Lamination is performed on a heating table or in a hot press at 85°C. The stacking is 2-3mm thick and then hot-pressed again. After cutting into small 1cm×1cm squares, the isostatic pressing is performed with a pressure of 200MPa for 5 minutes. The binder is then debinded. The debinding process is a heating program of 1°C / min to 600°C and a hold for 2 hours. After debinding, powder embedding and sintering were performed at 1165°C for 6 hours, ultimately yielding a densely textured sodium bismuth titanate-based ceramic. Before electrical testing, silver electrode slurry was screen-printed on both sides of the ceramic and sintered at 720°C for 15 minutes to produce the silver electrodes.

[0064] In this example, different La 3+ Doping amount (x) and Nb 5+Textured sodium bismuth titanate-based ceramics with doping amount (y), where 0.96[Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ] 0.992 La 0.008 (Ti 0.992 Nb 0.008 )O3-0.04SrTiO3 is recorded as BNKST-8LaNb textured ceramics.

[0065] Performance Testing

[0066] 1) Phase structure and microstructure characterization

[0067] The phase structure of the ceramic samples was determined by X-ray diffraction (XRD) analysis using a Cu Kα radiation source (λ = 0.15418 nm). By analyzing parameters such as the diffraction peak position, intensity, and half-maximum width, information such as the phase composition, unit cell parameters, and crystallinity of the samples could be obtained.

[0068] The microstructure of the ceramic samples was obtained by scanning electron microscopy (SEM). Before the cross-sectional morphology analysis, the samples were pretreated by keeping them at a temperature approximately 200°C below the ceramic sintering temperature for 15 minutes.

[0069] 2) Electrical performance test

[0070] Dielectric properties reflect the ability of a material to store charge in an electric field, and are essentially a macroscopic reflection of the charge polarization behavior within the material.

[0071] Among them, the relative dielectric constant (ε r ) is the core parameter, and the calculation formula is:

[0072]

[0073] Where ε is the dielectric constant and ε0 is the dielectric constant of vacuum. r A measure of the material's electric field energy storage capacity. The larger the value, the more electrical energy it can store under the same electric field. Therefore, high dielectric constant materials are widely used in the field of energy storage capacitors.

[0074] The dielectric loss tangent (tanδ) characterizes the energy loss of a dielectric under an electric field. It originates from mechanisms such as polarization relaxation and leakage conduction and is the ratio of active power (loss power) to reactive power. For high-frequency devices, low dielectric loss can significantly improve energy conversion efficiency. This paper uses an Agilent E4990A impedance analyzer to accurately collect the capacitance and dielectric loss characteristics of materials at different frequencies.

[0075] The piezoelectric effect is the core property of piezoelectric materials, including the direct piezoelectric effect (electric stress induces charge generation) and the inverse piezoelectric effect (electric field induces deformation), which realizes the mutual conversion of mechanical energy and electrical energy. The piezoelectric constant (d) is a key parameter to quantify the electromechanical conversion efficiency, among which the longitudinal piezoelectric strain constant d 33 It represents the piezoelectric response when the polarization direction is consistent with the stress direction. It is defined as the charge density generated by unit stress and is calculated as:

[0076]

[0077] ΔQ is the charge generated by the material under stress (unit: pC), and F is the applied stress (unit: N). 33 The instrument measures the charge output of piezoelectric materials when they are under pressure.

[0078] Ferroelectric properties are characterized by the spontaneous polarization of the material and the polarization reversal under an external electric field, which is manifested as a closed hysteresis loop. r ) characterizes the polarization state of the material after the external electric field is removed; the coercive field strength (E c ) reflects the minimum reverse electric field strength required for polarization reversal. The present invention uses the TF-2000 ferroelectric testing system to characterize the ferroelectric properties of piezoelectric ceramic samples and multilayer actuators.

[0079] Strain performance reflects the ability of a material to deform under the action of external force or electric field. It is a core indicator for the application of devices such as actuators and micro-displacers, and directly affects the displacement accuracy of the device. This paper focuses on the electrostrain caused by the inverse piezoelectric effect and uses the equivalent piezoelectric coefficient d 33 * To quantify the strain performance, the calculation formula is:

[0080]

[0081] E max is the maximum voltage applied in the strain curve (unit: V), S max The present invention uses the TF-2000 ferroelectric test system to accurately measure the displacement of piezoelectric ceramics and multilayer actuators under the inverse piezoelectric effect. Figure 4 Figure 2 is a schematic diagram of strain hysteresis calculation. Strain hysteresis (η) is calculated using the following formula:

[0082]

[0083] 1 / 2E max The strain difference at Figure 4 shown.

[0084] Performance test results

[0085] The following test results for hysteresis loops, bipolar strain curves, and unipolar strain curves are based on a test frequency of 1 Hz and a temperature of 25°C, unless otherwise specified. The different colors in the resulting curves correspond to different electric field ranges, corresponding to the range of the abscissa, unless otherwise specified.

[0086] 1) Properties of non-textured sodium bismuth titanate-based ceramics

[0087] Figure 5 The SEM images of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1 are shown below. (a) is x=y=0.003, (b) is x=y=0.005, (c) is x=y=0.008, (d) is x=y=0.01, (e) is x=y=0.015, and (f) is x=y=0.02. The SEM images show that all component samples have high density and clear grain boundaries, indicating the rationality of the sintering process parameters. When La 3+ and Nb 5+ When the doping amount (x, y) increases from 0.003 to 0.01, the grain size gradually increases; when the doping amount exceeds 0.015, the grain morphology changes, the grain edge shows a rounded feature, and the grain size is significantly reduced.

[0088] Figure 6 The XRD patterns of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1 are shown below; (a) is the overall XRD pattern, and (b) is the XRD magnified pattern at 2θ near 46.5°. The XRD diffraction results show that all component samples (x=y=0.003~0.02) are single perovskite structures, and no impurity peaks are detected; the {200} crystal plane diffraction peaks in the spectrum do not split, indicating that the material is a pseudo-cubic phase at room temperature. It is worth noting that when La 3+ and Nb 5+ When the doping amount (x, y) increases from 0.003 to 0.02, the {200} peak gradually shifts to a higher angle, indicating that La 3+ and Nb 5+ Doping leads to a decrease in unit cell parameters, especially for smaller radii Replaces the larger radius

[0089] Figure 7 The dielectric temperature spectra of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1 at 1 kHz show the relative dielectric constant (ε r ) and dielectric loss tangent (tanδ) with temperature, the test temperature range is 25 ~ 420 ℃. The figure shows that all component samples show a broadened dielectric peak, and with the increase of La 3+ and Nb5+ With the increase of doping amount (x, y), the relative dielectric constant gradually decreases; two significant dielectric anomaly peaks can be observed in all components, located at about 300℃ and 100℃ respectively, and no low-temperature ferroelectric-relaxation phase transition peak appears above room temperature, indicating that the system is in an ergodic relaxation state at room temperature under low doping content. Among them, the low-temperature peak at 100℃ corresponds to T R-T , representing the transition of the BNKST-xLaNb system from the rhombohedral R3c phase to the tetragonal P4bm phase; and T R-T With La 3+ and Nb 5+ The increase of doping amount gradually moves towards the low temperature direction, from the initial 123℃ to 73℃. In addition, as La 3+ and Nb 5+ As the doping level increases, the half-width of the dielectric peak gradually increases, indicating enhanced relaxation properties of the material. From the temperature variation curve of the dielectric loss tangent (tanδ) of different components in the figure, it can be seen that all components exhibit low dielectric loss in the range of 25-420℃.

[0090] Figure 8 The hysteresis loops of non-textured sodium bismuth titanate-based ceramics with different compositions in Example 1 are shown in the figure. When x=y=0.003, the hysteresis loop shows a contraction shape, indicating that the material is in the ergodic relaxation state at low doping concentration. 3+ and Nb 5+ With the increase of doping amount (x=y=0.008, 0.01, 0.015, 0.02), the shrinkage feature of the hysteresis loop becomes more obvious, indicating the increase of the relaxation state content in the material, which is specifically manifested in the remanent polarization intensity (P r ) and coercive field (E c ) decreases. With the increase of doping concentration, P r gradually decreases, indicating that the polarization strength retained by the material after the electric field is removed is weakened; with the increase of doping concentration, E c The value of the polarization of the material decreases gradually, indicating that the material's polarization reversal becomes easier under the action of an electric field. This is likely due to the increase in dopant ion concentration, which increases the disordered structure within the material. Furthermore, asymmetric behavior of the hysteresis loop is observed, indicating that the polarization response differs under positive and negative electric fields. This asymmetric behavior is closely related to the difference in the dynamic response of the defect dipoles, which are aligned after electric field polarization, under positive and negative electric fields.

[0091] Figure 9 Example 1 Bipolar strain curves and unipolar strain curves of non-textured sodium bismuth titanate-based ceramics with different compositions; (a) is the bipolar strain response curve, and (b) is the unipolar strain response curve. It is worth noting that, as Figure 9As shown in (a), the bipolar strain curves of all component samples show significant asymmetry, indicating that the material responds asymmetricly under positive and negative electric fields. This asymmetry is caused by the internal bias electric field formed by the defect dipole, but it may also be affected by the bending effect in thin piezoelectric ceramics. Figure 9 As shown in (b), with La 3+ and Nb 5+ With the increase of doping concentration, the unipolar strain shows a trend of increasing first and then decreasing. At low doping concentration (x=y=0.003), the unipolar strain is relatively low, and the unipolar strain value driven by 6kV / mm electric field is 0.55%; with the increase of doping concentration, the unipolar strain gradually increases, reaching a maximum value of 0.81% at x=y=0.008; with further increase of doping concentration (x=y>0.008), the unipolar strain begins to decrease, which is consistent with the change trend of the bipolar strain curve. Strain curve ( Figure 9 ), dielectric temperature spectrum ( Figure 7 ) and hysteresis loop ( Figure 8 ) mutually confirm and reveal La 3+ and Nb 5+ The regulation of the relaxation state of the system by doping.

[0092] Figure 10 The electrostrain properties of the BNKST-8LaNb non-textured ceramics in Example 1 are shown in Figure 1. (a) is the unipolar strain curve at different temperatures, (b) is the bipolar strain curve at 120°C, and (c) is the hysteresis loop at 120°C. Figure 10 As shown in (a), under a constant electric field strength (6kV / mm), the electrostrain of the material decays significantly with increasing temperature; at room temperature (25°C), the unipolar strain is 0.81%; however, as the temperature rises to 50°C, the strain value drops to 0.73%; when the temperature further rises to 120°C and 180°C, the strain drops to 0.68% and 0.52%, respectively; when the temperature reaches 230°C, the strain value drops to 0.31%, a decrease of 61.7% compared to room temperature, indicating that the electrostrain response performance of the material decays under high temperature environment. In addition, the strain hysteresis changes non-monotonically with increasing temperature. When the temperature gradually rises to 120°C, the strain hysteresis gradually decreases; when the temperature further increases, the strain hysteresis rebounds slightly. The strain and ferroelectric properties of BNKST-8LaNb non-textured ceramics at a high temperature of 120°C were further tested, as shown in the figure. Figure 10 As shown in (b) and (c), with the increase of electric field strength, the strain and polarization strength gradually increase. The bipolar strain curve and hysteresis loop at 120℃ show very small hysteresis and both show asymmetric characteristics. The coercive field (E c) are extremely low, namely -0.62kV / mm and 0.45kV / mm respectively. This asymmetry is closely related to the anisotropy of the defect dipole distribution inside the material.

[0093] The above performance tests demonstrate that Example 1, through compositional manipulation, can induce ergodic relaxation states in non-textured sodium bismuth titanate-based ceramics at room temperature. Example 1 exhibits low dielectric loss over a wide temperature range and achieves a high electrostrain response of 0.81% at 6 kV / mm at room temperature.

[0094] 2) Properties of textured sodium bismuth titanate-based ceramics

[0095] Furthermore, in Example 2, the ceramic component BNKST-8LaNb with x=y=0.008 in Example 1 was textured by the reaction template grain growth method (RTGG), which effectively improved the wide temperature range electrostrain stability of the ceramic. 12 (BiT) was used as a template and the grains were obtained by tape casting. <001> The oriented single-layer cast film is subjected to lamination, hot pressing, binder removal, sintering, mechanical polishing and other processes to obtain textured piezoelectric ceramics. For ceramic materials with a thickness of 0.22 mm, the orientation degree f calculated by the Lotgering method is (00l) It is about 88%, (00l) includes (001) and (002), and the calculation formula is as follows:

[0096]

[0097] P (00l) and P0 are the ratios of the sum of the peak intensities of (00l) plane to the sum of the peak intensities of all planes in textured and non-textured ceramics, respectively.

[0098] Figure 11 The XRD pattern and cross-sectional SEM image of the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm in Example 2; (a) is the XRD pattern, and (b) is the cross-sectional SEM image. Figure 11 As can be seen from (a), the {200} peak intensity is significantly enhanced, indicating that the grains are <001> Highly oriented; Figure 11 As can be seen in (b), the textured ceramics present a "brick-like" structure and are closely arranged along the thickness direction.

[0099] Figure 12 The dielectric temperature spectrum of the 0.22mm thick BNKST-8LaNb textured ceramic in Example 2 at different frequencies is shown in the figure. The test temperature range is 25-400℃. As the frequency increases, the T R-TThe dielectric anomaly peak shifts toward higher temperatures, and dielectric loss decreases above 300°C. Furthermore, the maximum relative permittivity corresponding to the highest dielectric peak in the BNKST-8LaNb textured ceramic is 3900, significantly lower than the maximum relative permittivity of 5000 for the untextured ceramic. This is likely due to the reduced dielectric response of the anisotropic grains along the c-axis in the textured ceramic. Consistent with the untextured ceramic, no dielectric anomaly peak corresponding to the ergodic relaxation-ferroelectric phase transition is observed near room temperature in the temperature-dependent dielectric curves of the textured sample, indicating that the BNKST-8LaNb textured ceramic is in an ergodic relaxation state at room temperature.

[0100] Figure 13 The electrostrain performance of the 0.22 mm thick BNKST-8LaNb textured ceramic at 25°C in Example 2 is shown in Figure 2. (a) is the bipolar SE curve, (b) is the hysteresis loop, (c) is the unipolar SE curve, and (d) is the strain value under different electric fields. 3+ and Nb 5+ The introduction of and Three types of defect dipoles, Figure 13 The bipolar strain curve (a) exhibits extreme asymmetry, which is closely related to the difference in dynamic response of the defect dipoles, which are aligned after electric field polarization, under positive and negative electric fields. On the other hand, BNKST-8LaNb textured ceramics (0.22 mm thick) also exhibit the electrobending effect of thin-thickness piezoelectric ceramics. Based on the mechanism of electrobending behavior of thin-thickness piezoelectric ceramics, the present invention establishes an electrobending mechanism based on defect dipoles, that is, the defect dipoles on the upper and lower surfaces of the ceramic are oriented inward. Under the action of an external electric field, the defect dipoles on the upper and lower surfaces respectively produce tensile / compressive responses. This asymmetric strain distribution triggers asymmetric deformation of the upper and lower surfaces, ultimately forming the electrobending effect. The proposed mechanism provides a new path for achieving large electrobending strain in BNK-based piezoelectric ceramics. Figure 13 (b) is the hysteresis loop of BNKST-8LaNb textured ceramics under different electric fields, showing obvious shrinkage characteristics. Its low residual polarization intensity (P r ~7.5μC / m 2 ) and low coercive field (E c ~0.7kV / mm) together reveal the ergodic relaxation characteristics of the material. Figure 13 (c) is the monopole strain curve under different electric fields. When the electric field value increases from 2kV / mm to 6kV / mm, the monopole strain value increases sharply from 0.35% to 2.1%. Figure 13(d) also shows that the unipolar strain value increases almost linearly with the increase of the electric field. The electrostrain response of BNKST-8LaNb textured ceramics has been greatly improved compared with that of non-textured ceramics (0.81%@6kV / mm), indicating that the coupling effect of grain orientation and electrobending effect has an enhancing effect on the electrostrain response of the system.

[0101] Given the importance of temperature stability for the practical application of piezoelectric materials, the temperature stability of the BNKST-8LaNb textured ceramics in Example 2 was further studied. The strain change rate (α) within a specific temperature range can be calculated using the following formula:

[0102]

[0103] T is the specific test temperature; α(T) is the strain change rate at the specific test temperature; S(T) is the strain at the specific test temperature; S(25°C) is the strain at 25°C.

[0104] Figure 14 The figure shows the electrostrain temperature stability of the BNKST-8LaNb non-textured ceramic in Example 1 and the BNKST-8LaNb textured ceramic with a thickness of 0.22 mm in Example 2; wherein, (a) is the unipolar strain curve of the BNKST-8LaNb textured ceramic at different temperatures measured at a frequency of 1 Hz; (b) is the S(T) / S(25°C) ratio and strain hysteresis of the textured and non-textured BNKST-8LaNb ceramics as a function of temperature; (c) is the unipolar strain curve of the BNKST-8LaNb non-textured ceramic at different temperatures measured at a frequency of 1 Hz. Figure 14 As shown in (a), the BNKST-8LaNb textured ceramic exhibits excellent electrostrain temperature stability over a wide temperature range of 25 to 250°C, with its unipolar strain value consistently maintained above 2%. The strain change rate α (250°C) is less than 4% across the wide temperature range of 25 to 250°C, significantly outperforming traditional piezoelectric ceramics such as PZT-5H, which exhibits a strain change rate of >30% from room temperature to 200°C. Figure 14Figure (b) further reveals the temperature dependence of the strain hysteresis of the BNKST-8LaNb textured ceramic. As the temperature rises from 25°C to 150°C, the strain hysteresis decreases from 48% to 15%. In the 150-200°C range, the strain hysteresis remains at 15%. Above 200°C, the strain hysteresis rebounds to 30%. In typical relaxor ferroelectrics, as the temperature increases, the relaxation state intensifies, and the strain hysteresis decreases accordingly. Notably, the electrobending strain in the BNKST-8LaNb textured ceramic, with a thickness of only 0.22 mm, becomes a significant component of the apparent strain. The electrobending effect, the synergistic coupling of the relaxor-ferroelectric phase transition, and grain orientation contribute to the material's large electrobending strain. Since the electrobending effect significantly intensifies with increasing temperature and drives a continuous increase in strain, it can be inferred that the temperature-dependent variation of the strain hysteresis in the BNKST-8LaNb textured ceramic is essentially a result of a competition between the attenuation of the strain hysteresis due to the enhanced relaxation state and the strengthening of the electrobending effect.

[0105] As a comparison, Figure 14 Figure (c) shows the temperature-dependent variation of the unipolar electrostrain of the BNKST-8LaNb non-textured ceramic. As the temperature rises from 25°C to 230°C, the electrostrain of the randomly oriented ceramic decreases from 0.80% to 0.31%, with a strain decay rate of 61%, demonstrating significant temperature sensitivity. Although both the non-textured and textured ceramics are 0.22 mm thick, the electrobending effect was minimized by reducing the diameter of the non-textured ceramic sample. The strain change rate of the non-textured ceramic is still much higher than that of the textured ceramic (α(250°C) < 4%), indicating that the synergistic effect of the electrobending effect and grain orientation plays a key role in improving the temperature stability of the electrostrain.

[0106] Given the urgent need for piezoelectric ceramic actuators in high-temperature service scenarios, research on piezoelectric materials with both excellent high-temperature stability and large electrostrain properties is of great significance. To this end, this paper further studied the electrostrain properties of BNKST-8LaNb textured ceramics at 200°C. Figure 15 The electrostrain properties of the 0.22 mm thick BNKST-8LaNb textured ceramics at 200°C in Example 2 are shown in Figure 2; (a) is the hysteresis loop under different electric fields; (b) is the bipolar strain curve at a frequency of 1 Hz; (c) is the unipolar strain curve; (d) is the change of the unipolar electrostrain value with the electric field; (e) is the comparison of the unipolar strain hysteresis at 25°C and 200°C; (f) is a comparison of the temperature stability of the textured BNKST-8LaNb ceramics and the lead-free and commercial lead-containing piezoelectric ceramics reported in the existing literature (KNN in the figure represents (K 0.485 Na 0.485 Sr 0.03)NbO3, reported in the literature "Wang B, Geng H, Zheng Z, et al. Giant electric field-induced strain with high temperature-stability in textured KNN-based piezoceramics for actuator applications [J]. Advanced Functional Materials, 2023, 33(20): 2214643."; PZT-5H represents PbZr 0.53 Ti 0.47 O3, reported in the literature "Wang D, Fotinich Y, Carman G P. Influence of temperature on the electromechanical and fatigue behavior of piezoelectricceramics [J]. Journal of Applied Physics, 1998, 83 (10): 5342-5350."; BNBT-KNLNS represents 0.97Bi 0.47 Na 0.47 Ba 0.06 TiO3-0.03K 0.47 Na 0.47 Li 0.06 Nb 0.99 Sb 0.01 O 2.99 , reported in the literature “Li T, Liu C, Shi P, et al. High-performance strain of lead-free relaxor-ferroelectricpiezoceramics by the morphotropic phase boundary modification[J]. Advanced Functional Materials, 2022, 32(32): 2202307.”; BF-BT represents 0.64BiFeO3-0.36BaTiO3, reported in the literature “Chen J, Daniels JE, Jian J, et al. Origin of large electric-field-inducedstrain in pseudo-cubic BiFeO3-BaTiO3 ceramics[J]. Acta Materialia, 2020, 197: 1-9.”).

[0107] like Figure 15 As shown in (a), compared with the PE loop at room temperature, the polarization intensity of the PE loop of the material at 200℃ is reduced, indicating that the ergodic relaxation characteristics of the material are enhanced under high temperature conditions. The bipolar SE curve of BNKST-8LaNb textured ceramics at 200℃ still shows obvious asymmetry ( Figure 15 (b)), indicating that the electrobending effect plays a significant role in the electrostrain behavior. Figure 15 As shown in (c) and (d), when the electric field value gradually increases from 2kV / mm to 6kV / mm, the unipolar electrostrain increases from 0.24% to 2.0%. Figure 15 (e) compares the strain hysteresis of textured ceramics at 25°C and 200°C. The strain hysteresis at room temperature is greater than 30%, while the strain hysteresis at 200°C remains at around 15%, which is significantly lower than that of commercial "soft" Pb(Zr,Ti)O3 (PZT) ceramics, whose hysteresis at high temperature is usually greater than 20%. Figure 15 (f) compares the temperature dependence of the electrostrain of BNKST-8LaNb textured ceramics with that of lead-free and commercial lead-based piezoelectric ceramics reported in existing literature. The shaded area represents the normalized deviation amplitude of the electrostrain relative to room temperature. It can be seen that the wide temperature range strain stability of BNKST-8LaNb textured ceramics is not only better than the lead-free systems such as BNT, KNN and BF based reported in the literature, but also surpasses traditional commercial lead-based piezoelectric ceramics (such as PZT-5H).

[0108] In order to study the high-temperature fatigue resistance of BNKST-8LaNb textured ceramics, the stability test of strain performance under electric field cycling was carried out at a high temperature of 200°C. Figure 16 The fatigue resistance of the 0.22 mm thick BNKST-8LaNb textured ceramic at 200°C in Example 2 is shown in Figure 2. During the test, the cyclic electric field frequency was 10 Hz, the test frequency was 1 Hz, and the BNKST-8LaNb textured ceramic underwent 10 6 After the electric field cycle loading, the unipolar strain increases slightly from the initial 2.0% to 2.1%, with a strain change rate of only 5%, and always maintains low hysteresis characteristics, showing excellent high-temperature fatigue stability. This excellent performance is due to the reversible ergodic relaxation state-ferroelectric phase transition, high <001> The synergistic effect of multiple mechanisms, including preferred grain orientation and defect dipole-induced electrobending effects, is evident in the synergistic effect. It is worth noting that BNKST-8LaNb textured ceramics not only maintain excellent strain-temperature stability over a wide temperature range of 25-250°C, but also maintain high electrostrain response even at temperatures up to 200°C for long periods. This combination of wide-temperature stability and high-temperature fatigue resistance makes textured BNKST-8LaNb ceramics an ideal candidate for high-precision actuators, smart sensors, and other devices in high-temperature environments.

[0109] In summary, in the embodiment of the present invention, Nb is introduced into the 0.96BNKT-0.04ST ceramic system. 5+ and La 3+ ions, by controlling the composition, induce an ergodic relaxation state at room temperature, simultaneously forming a defect dipole. This innovative combination of the ergodic relaxation state-ferroelectric phase transition mechanism and the electrobending effect induced by the defect dipole overcomes the limitation of the phase transition temperature on the temperature stability of the electrostrain. The main research results are as follows:

[0110] Nb 5+ and La 3+ ions occupy the B and A sites of the perovskite structure, forming and Three defect dipoles induce ergodic relaxation states at room temperature through composition control. <001> In the oriented textured BNKST-8LaNb piezoelectric ceramics, the ergodic relaxation state-ferroelectric phase transition mechanism is innovatively combined with the electro-bending strain effect induced by defect dipoles, achieving a large electro-strain of 2.1% at room temperature, and the strain fluctuation is less than 4% in the temperature range of 25-250℃. It shows excellent fatigue resistance (10 6 The results show that the strain of BNT-based piezoelectric ceramics has almost no attenuation after sub-unipolar electric field cycling and low hysteresis (15%). This confirms the advantages of the defect dipole-induced bending effect and the coupling effect of the relaxation-ferroelectric phase transition in achieving the temperature stability of strain, providing new ideas for the design of piezoelectric materials for service in high-temperature environments.

[0111] In summary, the present invention introduces Nb into sodium bismuth titanate-based ceramics. 5+ and La 3+ ions can induce ergodic relaxation states at room temperature by controlling the composition, and at the same time, defect dipoles are formed. By combining the ergodic relaxation state-ferroelectric phase transition mechanism with the electro-bending strain effect induced by the defect dipoles, the electro-strain properties of sodium bismuth titanate-based ceramics are effectively improved. It has good application prospects in the preparation of aerospace devices, new energy equipment or industrial control equipment.

Claims

1. A sodium bismuth titanate-based ceramic, characterized in that: The chemical formula of the sodium bismuth titanate-based ceramic is 0.96[Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ] 1-x La x (Ti 1-y Nb y )O3-0.04SrTiO3, x is 0.003~0.02, y is 0.003~0.

02.

2. The sodium bismuth titanate-based ceramic according to claim 1, characterized in that The sodium bismuth titanate-based ceramic includes a textured sodium bismuth titanate-based ceramic or a non-textured sodium bismuth titanate-based ceramic.

3. The sodium bismuth titanate-based ceramic according to claim 2, characterized in that The ceramic grains of the textured sodium bismuth titanate-based ceramic are <001> orientation; And / or, the ceramic grain orientation degree of the textured sodium bismuth titanate-based ceramic is ≥80%.

4. The sodium bismuth titanate-based ceramic according to claim 1, characterized in that The average particle size of the ceramic grains of the sodium bismuth titanate-based ceramic is 1 to 5 μm.

5. The sodium bismuth titanate-based ceramic according to claim 1, characterized in that The thickness of the sodium bismuth titanate-based ceramic is 0.1-1 mm.

6. A method for preparing sodium bismuth titanate-based ceramics as claimed in claims 1 to 5, characterized in that: The following steps are involved: According to the chemical formula of the sodium bismuth titanate-based ceramic, raw materials of various components in a stoichiometric ratio are measured and the sodium bismuth titanate-based ceramic is prepared by a reaction template grain growth method or a solid phase method.

7. The preparation method according to claim 6, characterized in that The reactive template grain growth method specifically comprises: preparing bismuth titanate template crystals through a molten salt system; according to the chemical formula of the sodium bismuth titanate-based ceramic, measuring oxides or carbonates containing various elements, mixing them with the bismuth titanate template crystals, additives and solvents to obtain a ceramic slurry; using the reactive template grain growth method, tape-casting the ceramic slurry through a tape-casting process to obtain a single-layer tape-cast film; stacking the single-layer tape-cast films to obtain a tape-cast green body; and sequentially subjecting the tape-cast green body to hot pressing, isostatic pressing, debinding and sintering to obtain the sodium bismuth titanate-based ceramic; The solid phase method specifically comprises the following steps: according to the chemical formula of the sodium bismuth titanate-based ceramic, oxides or carbonates containing various elements are measured, and the ceramic is subjected to primary ball milling, pre-sintering, secondary ball milling, granulation, tableting, debinding and sintering in sequence to obtain the sodium bismuth titanate-based ceramic.

8. The preparation method according to claim 7, characterized in that In the reaction template grain growth method, the height of the casting scraper in the tape casting process is 100-200 μm; the speed of the casting film belt is 0.5-2 cm / s; and the temperature of the casting machine is 50-60° C.

9. The preparation method according to claim 7, characterized in that In the reaction template grain growth method, the sintering temperature is 1100-1200° C. and the sintering time is 4-7 hours; And / or, in the solid phase method, the sintering temperature is 1100-1200° C.; the sintering time is 2-5 hours.

10. Use of the sodium bismuth titanate-based ceramics according to claims 1 to 5 in the preparation of aerospace devices, new energy equipment or industrial control equipment.

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