Calcium bismuth titanate-based high-entropy piezoelectric ceramic with high piezoelectric property and preparation method of calcium bismuth titanate-based high-entropy piezoelectric ceramic

Abstract

The invention relates to a calcium bismuth titanate-based high-entropy piezoelectric ceramic with high piezoelectric property and a preparation method thereof. The chemical composition of the calcium bismuth titanate-based high-entropy piezoelectric ceramic is Ca < 1-x > (Na < 1 / 6 > Bi < 1 / 6 > Li < 1 / 6 > Ce < 1 / 6 > K < 1 / 6 > Bi < 1 / 6 >) < x > Bi < 4 > Ti < 3.9 > (Nb < 1 / 2 > Mn < 1 / 2 >) < 0.1 > O < 15 >, and x is larger than or equal to 0.1 and smaller than or equal to 0.5. The room-temperature piezoelectric coefficient of the calcium bismuth titanate-based high-entropy piezoelectric ceramic provided by the invention can reach 28.1 pC / N, and meanwhile, the Curie temperature is kept at 700 DEG C or above.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramics and relates to a high-entropy piezoelectric ceramic based on bismuth calcium titanate with high piezoelectric properties and its preparation method. Background Technology

[0002] Piezoelectric materials possess unique electromechanical energy conversion characteristics and are core components of sensors, transducers, and actuators used in modern industry. With the rapid development of science and technology, the demand for piezoelectric devices capable of stable operation in extreme high-temperature environments is increasingly urgent, such as high-temperature piezoelectric accelerometers used to monitor the structural health of aerospace engines and nuclear reactors. Against this backdrop, the development of high-performance piezoelectric ceramics with high Curie temperatures is crucial. Bismuth layered piezoelectric ceramics have attracted much attention due to their high Curie temperature, low aging rate, and excellent fatigue resistance. Their typical layered structure consists of m pseudo-perovskite layers and fluorite layers alternately stacked along the c-axis. Among all bismuth layered piezoelectric ceramics, CaBi4Ti4O... 15 CBT ceramics, due to their high Curie temperature of 780°C and excellent thermal depolarization capability, are considered one of the most promising candidate materials for high-temperature applications. However, the two-dimensional orientation of spontaneous polarization in CBT ceramics restricts the spatial rotation of the polarization vector, leading to a decrease in its piezoelectric coefficient. d 33 The ratio of pC / N is generally low (<10 pC / N), which cannot meet the actual application requirements of high-temperature piezoelectric devices.

[0003] To improve the piezoelectric properties of CBT ceramics, researchers have explored various strategies, including chemical composition design, defect engineering, and texture engineering. For example, Zhou et al. (Journal of Inorganic Materials, 40, 719, 2025) utilized space charge polarization to enhance the piezoelectric properties of CBT-based ceramics by self-doping Bi ions at the A-site. d 33 The ratio was increased to 20.1 pC / N. Wen et al. (Ceramics International, 51, 28236, 2025) employed a strategy of Ce doping at the A-site and co-doping at the B-site (Mo, Ga), which increased the ratio to 20.1 pC / N. d 33 The efficiency was further increased to 24.7 pC / N. Furthermore, Wang et al. (Journal of the American Ceramics Society, 108, e20207, 2025) successfully synthesized pure CBT ceramics through texture engineering. d 33 Optimized to 24.3 pC / N. Nevertheless, existing studies report that the piezoelectric coefficient of CBT ceramics...d 33 It is still generally difficult to exceed 25 pC / N.

[0004] In recent years, the high-entropy strategy of introducing at least five different ions into solid solutions has been proven to effectively improve material properties. This is mainly attributed to its high-entropy effect, lattice distortion effect, retarded diffusion effect, and "cocktail" effect. Currently, this strategy has shown initial success in improving the ferroelectric and resistive properties of CBT ceramics. Zhang et al. (Acta Materialia, 229, 117815, 2022) designed (Ca... 0.2 Sr 0.2 Ba 0.2 Pb 0.2 Nd 0.1 Na 0.1 Bi4Ti4O 15 Ceramics were studied, and complex ferroelectric behavior and field-induced phase transitions were reported. Lu et al. (Lu, et al., Journal of Materials, 11, 100945, 2025) introduced disordered structures and various lattice distortions into CBT-based ceramics through non-equimolar high-entropy design, significantly increasing its high-temperature resistivity at 500℃ to 1.18 × 10⁻⁶. 8 Ω·cm. However, it should be emphasized that none of the above studies focused on improving piezoelectric properties, and the results... d 33 The values ​​are only 12.6 pC / N and 14 pC / N, respectively. Therefore, there is an urgent need to further optimize the chemical composition design of high-entropy CBT ceramics to achieve breakthroughs. d 33 bottleneck. Summary of the Invention

[0005] To address the issue of poor piezoelectric properties in bismuth calcium titanate piezoelectric ceramics, this invention provides a high-entropy bismuth calcium titanate-based high-entropy piezoelectric ceramic with high piezoelectric properties and its preparation method. The composition of the bismuth calcium titanate ceramic is designed using a high-entropy A-site and equivalent substitution B-site strategy, thereby obtaining a bismuth calcium titanate piezoelectric ceramic with high piezoelectric properties. This meets the requirements for piezoelectric ceramic materials used in high-temperature piezoelectric vibration sensors, promoting its application in high-temperature fields.

[0006] On one hand, the present invention provides a high-entropy piezoelectric ceramic based on calcium bismuth titanate with high voltage performance, wherein the chemical composition of the high-entropy piezoelectric ceramic is Ca. 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Where x is the molar percentage, 0.1≤x≤0.5; wherein, by controlling x below 0.5, the reduction of the polarization reversal energy barrier and the improvement of spontaneous polarization brought about by the increase of entropy are utilized to obtain piezoelectric ceramic materials with high voltage electrical properties; if the value of x is greater than 0.5, the configuration entropy will gradually decrease, which is contrary to the purpose of this invention to improve the ceramic performance by using a high entropy strategy.

[0007] Preferably, the bismuth-calcium titanate-based high-entropy piezoelectric ceramic has a room-temperature piezoelectric coefficient of 21.1–29.1 pC / N and a Curie temperature >700℃.

[0008] On the other hand, the present invention provides a method for preparing bismuth calcium titanate-based high-entropy piezoelectric ceramics with high piezoelectric properties, comprising: using Bi2O3, CaCO3, Na2CO3, Li2CO3, K2CO3, CeO2, TiO2, Nb2O5 and MnO2 as raw materials, according to Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 The above raw material powders are weighed in a stoichiometric ratio of (0.1≤x≤0.5), mixed and synthesized to obtain ceramic powders; the obtained ceramic powders are sintered to obtain the bismuth calcium titanate-based high-entropy piezoelectric ceramics.

[0009] Preferably, the mixing method is wet planetary ball milling, and the parameters of the wet planetary ball milling include: the mass ratio of raw material powder: anhydrous ethanol: milling media = 1:(0.5~0.9):(1.2~1.8), the milling time is 2~6 hours, and the milling media is agate balls.

[0010] Preferably, the synthesis temperature is 700–900°C and the time is 2–4 hours; more preferably, the temperature is increased to 800–900°C at a heating rate not exceeding 2°C / min, held for 1–3 hours, and then cooled to room temperature in the furnace.

[0011] Preferably, the sintering conditions include: heating to 850-950°C at a heating rate not exceeding 3°C / min, then heating to 1000-1100°C at a heating rate not exceeding 2°C / min, holding at that temperature for 1-3 hours, and then cooling to room temperature in the furnace.

[0012] Preferably, the preparation method further includes fine grinding of the synthesized ceramic powder; the fine grinding parameters include: the mass ratio of ceramic powder: anhydrous ethanol: milling media = 1:(0.5~0.9):(1.2~1.8), and the fine grinding time is 4~8 hours.

[0013] Preferably, the preparation method further includes: adding a binder to finely ground and dried ceramic powder for granulation, then pressing and molding the powder to obtain a ceramic green body, and then sintering the ceramic green body.

[0014] Preferably, the amount of binder added is 4 to 8 wt% of the ceramic powder; more preferably, the binder is polyvinyl alcohol.

[0015] Preferably, the conditions for descaling include: heating to 700-800°C at a heating rate not exceeding 2°C / min, holding at that temperature for less than 3 hours, and then cooling with the furnace.

[0016] Preferably, the preparation method further includes: coating the surface of the obtained bismuth calcium titanate-based high-entropy piezoelectric ceramic with platinum, drying and calcining to cure it, and finally performing polarization treatment.

[0017] Preferably, the conditions for the platinum curing treatment include: heating to 800-900°C at a heating rate of no more than 2°C / min and holding at that temperature for no more than 60 minutes, and then cooling to room temperature in the furnace; The polarization treatment conditions include: applying an electric field of 8 to 12 kV / mm at 160 to 200°C for 10 to 20 minutes. Beneficial effects

[0018] This invention combines the design principles of high-entropy materials with the characteristics of bismuth layered piezoelectric materials. By introducing six equimolar amounts of ions at the A-site and simultaneously introducing (Nb / Mn) ion pairs at the B-site, a method was designed to improve piezoelectric performance while maintaining a high Curie temperature. This resulted in a high-entropy piezoelectric ceramic based on bismuth calcium titanate. The obtained bismuth calcium titanate-based high-entropy piezoelectric ceramic exhibits a room-temperature piezoelectric coefficient of 28.1 pC / N, while maintaining a Curie temperature above 700 °C, making it the bismuth calcium titanate-based piezoelectric ceramic with the highest reported piezoelectric coefficient to date. Attached Figure Description

[0019] Figure 1 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) xBi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 X-ray diffraction patterns of CBT, C6BT, and CBTNM (x=0.1, 0.3, 0.5); Figure 2 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Dielectric temperature spectra (1 MHz) of CBT, C6BT, and CBTNM (x=0.1, 0.3, 0.5); Figure 3 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Resistivity as a function of temperature for (x=0.1, 0.3, 0.5), CBT, C6BT and CBTNM; Figure 4 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 PE hysteresis loops of CBT, C6BT, and CBTNM (x=0.1, 0.3); Figure 5 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 PE hysteresis (x=0.5). Detailed Implementation

[0020] To more clearly illustrate the technical solution, features, and practical effects of the present invention, a detailed description is provided below with reference to specific embodiments. It should be understood that the modification method of the present invention is not limited to the described embodiments. Equivalent substitutions or modifications made by those skilled in the art based on the teachings of the present invention, without departing from the spirit of the invention, are also within the scope of protection of the claims of the present invention. In each embodiment, unless otherwise specified, the percentage content refers to mass percentage content.

[0021] First, this invention provides a high-entropy piezoelectric ceramic based on bismuth calcium titanate with high voltage performance, wherein the chemical composition of the bismuth calcium titanate piezoelectric ceramic is Ca. 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Where x is the molar percentage (0.1 ≤ x ≤ 0.5). A high-entropy strategy was employed to enhance spontaneous polarization intensity and reduce the polarization reversal energy barrier, thereby obtaining a bismuth calcium titanate-based high-temperature piezoelectric ceramic with high piezoelectric properties. This meets the requirements of high-temperature piezoelectric ceramic components for high-temperature piezoelectric ceramic materials, strongly promoting the application of high-temperature piezoelectric ceramic materials in high-temperature fields, and is expected to be applied in high-temperature piezoelectric vibration sensors at 480℃ and above. In some examples, the piezoelectric coefficient of the bismuth calcium titanate piezoelectric ceramic is 21.1–29.1 pC / N. This represents a significant improvement in piezoelectric performance compared to pure bismuth calcium titanate ceramic (piezoelectric coefficient of 8.6 pC / N).

[0022] In this invention, a high-entropy strategy is introduced at the A-site to achieve flexible design of local polarization configurations and reduce the polarization reversal energy barrier. Simultaneously, the size mismatch of the Nb / Mn ions at the B-site (Nb...) 5+ The ionic radius is 0.64 Å, Mn 3+ The ionic radius is 0.645 Å, while Ti 4+The increased lattice distortion caused by the ionic radius of 0.605 Å also helps to improve spontaneous polarization, thereby synergistically optimizing piezoelectric performance.

[0023] In addition, the present invention also provides a preparation process for the above-mentioned bismuth titanate calcium-based high-entropy piezoelectric ceramic, which specifically includes processes such as batching, mixing, synthesis, fine grinding, granulation, molding, plasticizing, and sintering.

[0024] The following is an exemplary description of the preparation method of the bismuth titanate calcium-based high-entropy piezoelectric ceramic with high voltage electrical properties provided by the present invention.

[0025] According to Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Bi₂O₃, CaCO₃, Na₂CO₃, Li₂CO₃, K₂CO₃, CeO₂, TiO₂, Nb₂O₅ and MnO₂ powders were weighed in a stoichiometric ratio of (0.1≤x≤0.5) and then synthesized into ceramic powders by wet planetary ball milling.

[0026] In an optional embodiment, in a wet planetary ball mill, the raw material powder: anhydrous ethanol: milling media = 1:(0.5~0.9):(1.2~1.8) is mixed for 2~6 hours, and the milling media are agate balls. The milled mixture is then dried in a constant temperature oven at 50~100℃.

[0027] In an optional embodiment, the synthesis conditions are as follows: synthesis at 700–900°C for 2–4 hours. Preferably, the temperature is increased to 800–900°C at a heating rate not exceeding 2°C / min, held for 1–3 hours, and then cooled to room temperature in the furnace to obtain the corresponding synthesized product.

[0028] The synthesized material is subjected to secondary planetary ball milling (i.e. fine grinding) and drying.

[0029] In an optional embodiment, fine grinding is performed for 4 to 8 hours at a mass ratio of the compound: anhydrous ethanol: milling media = 1:(0.5 to 0.9):(1.2 to 1.8). The milling media are agate balls. After secondary planetary ball milling, the mixture is dried at 50 to 100°C.

[0030] A binder is added to the finely ground and dried powder for granulation. After aging, the powder is pressed into shape and heated to remove plastic, thus obtaining a ceramic body.

[0031] In an optional embodiment, the binder is 7 wt.% polyvinyl alcohol (PVA); the amount of binder added is 4 to 8 wt.% of the dried powder.

[0032] The molding and desizing conditions are as follows: the granulated powder is pressed into discs with a diameter of 13 mm and a thickness of 2 mm using a pressure of 80–150 MPa. The pressed discs are then heated to 700–800 °C at a heating rate not exceeding 2 °C / min and held at that temperature for no more than 3 hours.

[0033] The ceramic blank after desizing was placed in a five-sided heating furnace. Meanwhile, in order to reduce the volatilization of bismuth oxide at high temperature, the synthesized ceramic powder was used as a filler and sintered to obtain bismuth calcium titanate piezoelectric ceramic sheets.

[0034] In an optional embodiment, the sintering conditions are as follows: heating to 850-950°C at a heating rate not exceeding 3°C / min, then heating to 1000-1100°C at a heating rate not exceeding 2°C / min, holding at that temperature for 1-3 hours, and then cooling to room temperature with the furnace.

[0035] The bismuth calcium titanate piezoelectric ceramic sheet is processed to the required size, cleaned, screen-printed with platinum paste, dried, calcined with platinum, and then electrodes are applied and polarized to obtain the bismuth calcium titanate piezoelectric ceramic.

[0036] In an optional embodiment, the platinum calcination conditions are: heating to 800–900°C at a heating rate not exceeding 2°C / min, and holding at that temperature for no more than 60 minutes. The polarization conditions are: applying an electric field of 8–12 kV / mm at 160–200°C, and polarizing for 10–20 minutes.

[0037] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Example 1

[0038] In this embodiment 1, Ca was prepared using a solid-state sintering method. 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) xBi4Ti 3.9 (Nb 1 / 2Mn 1 / 2 ) 0.1 O 15 (0.1≤x≤0.5) Piezoelectric ceramics, where x=0.1: (1) Using Bi2O3, CaCO3, Na2CO3, Li2CO3, K2CO3, CeO2, TiO2, Nb2O5 and MnO2 powders as raw materials, according to the chemical formula Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 The raw material powder was calculated and then placed in a ball mill jar for ball milling and mixing. The mass ratio of raw material powder, anhydrous ethanol, and ball milling media (agate balls) was 1:0.65:1.5. The mixture was wet-milled using a planetary ball mill for 4 hours to ensure uniform mixing. The mixed slurry was dried at 80°C and passed through a 40-mesh sieve. The sieved powder was pressed into blocks and then placed in an alumina crucible. The crucible was heated to 850°C at a heating rate of 2°C / min in a high-temperature furnace, held at that temperature for 2 hours, and then cooled with the furnace to obtain the ceramic blocks required for synthesis. (2) After mechanically crushing the synthesized ceramic blocks and passing them through a 40-mesh sieve, the sieved powder was finely ground using a wet planetary ball mill. The fine grinding parameters included: the mass ratio of ceramic powder to anhydrous ethanol to the ball milling media (agate balls) was 1:0.6:1.5, and the ball milling time was 6 hours. Then, 6 wt.% of binder (7 wt.% PVA aqueous solution) was added to the finely ground powder, and the powder was ground and granulated. The granulated powder was pressed into blocks and aged at room temperature for 24 hours. The aged blocks were crushed and ground in a mortar and passed through a 40-mesh sieve again to obtain granular powder with good flowability. Then, the powder was pressed into a circular blank with a diameter of 13 mm using a specific mold on a press. The blank was then heated to 750°C at a heating rate of 2 ℃ / min in a low-temperature furnace and held for 2 hours to remove plastic. (3) Place the powder with the same composition as the ceramic body as the filler in a sealed alumina crucible, and place the ceramic body on the filler; then put the crucible into a high temperature furnace and heat it to 900°C at a heating rate of 3°C / min, and then heat it to 1050°C at a heating rate of 2°C / min, hold it for 2 hours and cool it to room temperature with the furnace to obtain the desired ceramic sheet. (4) The obtained ceramic sheet is processed to a thickness of 0.5 mm, then ultrasonically cleaned, dried, and wire-screened with platinum on both sides. Then, the temperature is raised to 850℃ at a rate of 2℃ / min and kept at that temperature for 30 minutes to cure the platinum paste. Finally, polarization is performed. The polarization conditions are: apply a 10 kV / mm electric field to silicone oil at 180℃ for 10 minutes to obtain the bismuth calcium titanate piezoelectric ceramic. Example 2

[0039] The preparation process of the bismuth calcium titanate-based high-entropy piezoelectric ceramic in Example 2 is the same as in Example 1, except that x = 0.3. Example 3

[0040] The preparation process of the bismuth calcium titanate-based high-entropy piezoelectric ceramic in Example 3 is the same as in Example 1, except that x=0.5. Comparative Example 1

[0041] The preparation process of the pure bismuth calcium titanate piezoelectric ceramic in Comparative Example 1 is the same as in Example 1, except that the chemical composition is CaBi4Ti4O (CBT). Comparative Example 2

[0042] The preparation process of the bismuth titanate calcium-based piezoelectric ceramic in Comparative Example 2 is the same as in Example 2, the only difference being that the chemical composition is Ca. 0.7 (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) 0.3 Bi4Ti4O 15 (C6BT). Comparative Example 3

[0043] The preparation process of the bismuth calcium titanate-based piezoelectric ceramic in Comparative Example 3 is the same as in Example 1, except that the chemical composition is CaBi4Ti. 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 (CBTNM).

[0044] Testing was performed on the polarized bismuth-calcium titanate-based high-entropy piezoelectric ceramics: Curie temperature T c Tests were conducted according to GB / T 3389.3; the phase structure of the bismuth calcium titanate-based high-entropy piezoelectric ceramic was analyzed using an Aeris X-ray diffractometer from PANalyical; and a ZJ-3A quasi-static X-ray diffractometer from the Institute of Acoustics, Chinese Academy of Sciences was used. d 33The tester measures the piezoelectric ceramics at room temperature. d 33 The test frequency was 110Hz; the DC resistivity of the ceramic was measured using a HRMS-1000I high-temperature resistance testing system developed by Bailibo, connected to a Keithley 6517B electrometer / high-resistance meter. The test results of various properties of the bismuth titanate-based high-entropy piezoelectric ceramic of this invention are shown in Table 1.

[0045] Table 1: .

[0046] As can be seen from Table 1, the introduction of high entropy at the A site and the (Nb / Mn) ion pair at the B site improves the ceramic with x=0.3. d 33 The pC / N ratio was significantly increased to 28.1, three times that of pure CBT ceramics, reaching the highest value reported to date for CBT-based piezoelectric ceramics. It is worth noting that the x=0.3 ceramic... d 33 The higher entropy introduced by the A-site alone and the B-site alone (Nb / Mn) ion pair indicates that both are more conducive to the development of the Nb / Mn ion pair. d 33 synergistic improvement.

[0047] Figure 1 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 X-ray diffraction patterns of CBT, C6BT, and CBTNM (x=0.1, 0.3, 0.5). From Figure 1 As can be seen, the main diffraction peaks of all samples are in agreement with CBT (PDF# 52-1460). With increasing x, the configuration entropy increases from 0.65R (x=0.1) to 1.72R (x=0.5). However, significant Bi content was detected in the x=0.5 ceramic with the high configuration entropy. 1.74 Ti2O 6.624 Impurity phase (PDF# 89-4732). This impurity phase can cause the main phase to deviate from the stoichiometry, which may in turn affect the piezoelectric properties.

[0048] Figure 2 For the present invention Ca 1-x (Na 1 / 6 Bi1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Dielectric temperature spectra of CBT, C6BT, and CBTNM (x=0.1, 0.3, 0.5). From Figure 2 As can be seen, the Curie temperature of ceramics decreases slightly after the introduction of high-entropy A-site and (Nb / Mn) ion pairs at B-site, but the Curie temperature of x=0.3 ceramics with superior overall performance is still as high as 740℃.

[0049] Figure 3 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 Resistivity versus temperature for (x=0.1, 0.3, 0.5), CBT, C6BT, and CBTNM. From... Figure 3 As can be seen, the resistivity of all samples decreases with increasing temperature, which is attributed to the increase in thermally activated carrier concentration. At 500℃, the resistivity of bismuth calcium titanate-based high-entropy piezoelectric ceramics is increased by 1-2 orders of magnitude compared to CBT ceramics, with the resistivity of the ceramic at x=0.3 reaching 1.32×10⁻⁶. 6 Ω·cm.

[0050] Figure 4 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 PE hysteresis loops of CBT, C6BT, and CBTNM (x=0.1, 0.3). Figure 4 As can be seen from this, the ceramic with x=0.3 has the largest spontaneous polarization intensity (P s =27.44μC cm -2 ) and the lowest coercive field ( E c =1.24 kV / mm), indicating that the introduction of high entropy at the A site and (Nb / Mn) ion pairs at the B site successfully reduced the polarization reversal energy barrier and improved the spontaneous polarization intensity by enhancing lattice distortion, which is beneficial for achieving high voltage performance.

[0051] Figure 5 For the present invention Ca 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 The PE hysteresis loop at (x=0.5). Figure 5 As can be seen, the PE loop of the x=0.5 ceramic exhibits significant leakage current, which severely hinders the full polarization of the ceramic. This phenomenon is likely related to the impurity phase Bi. 1.74 Ti2O 6.624 This is related to the deviation of the main phase from the stoichiometric ratio. This also explains why, although the ceramic with x=0.5 has a larger configurational entropy, its... d 33 However, it failed to improve further.

Claims

1. A high-entropy piezoelectric ceramic based on bismuth calcium titanate, characterized in that, The chemical composition of the bismuth titanate calcium-based high-entropy piezoelectric ceramic is Ca. 1-x (Na 1 / 6 Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 , where x is the mole percentage, 0.1≤x≤0.

5.

2. The bismuth calcium titanate-based high-entropy piezoelectric ceramic according to claim 1, characterized in that, The bismuth titanate calcium-based high-entropy piezoelectric ceramic has a room temperature piezoelectric coefficient of 21.1–29.1 pC / N and a Curie temperature >700℃.

3. A method for preparing a bismuth calcium titanate-based high-entropy piezoelectric ceramic according to claim 1 or 2, characterized in that, include: Using Bi₂O₃, CaCO₃, Na₂CO₃, Li₂CO₃, K₂CO₃, CeO₂, TiO₂, Nb₂O₅, and MnO₂ as raw materials, according to Ca 1-x (Na 1 / 6Bi 1 / 6 Li 1 / 6 Ce 1 / 6 K 1 / 6 Bi 1 / 6 ) x Bi4Ti 3.9 (Nb 1 / 2 Mn 1 / 2 ) 0.1 O 15 The above raw material powders are weighed in a stoichiometric ratio of (0.1≤x≤0.5), mixed and synthesized to obtain ceramic powders; the obtained ceramic powders are sintered to obtain the bismuth calcium titanate-based high-entropy piezoelectric ceramics.

4. The preparation method according to claim 3, characterized in that, The mixing method is wet planetary ball milling. The parameters of the wet planetary ball milling include: the mass ratio of raw material powder: anhydrous ethanol: milling media = 1:(0.5~0.9):(1.2~1.8), the milling time is 2~6 hours, and the milling media is agate balls.

5. The preparation method according to claim 3 or 4, characterized in that, The synthesis temperature is 700–900°C, and the time is 2–4 hours; preferably, the temperature is increased to 800–900°C at a heating rate not exceeding 2°C / min, held for 1–3 hours, and then cooled to room temperature in the furnace.

6. The preparation method according to any one of claims 3-5, characterized in that, The sintering conditions include: heating to 850-950°C at a heating rate not exceeding 3°C / min, then heating to 1000-1100°C at a heating rate not exceeding 2°C / min, holding at that temperature for 1-3 hours, and then cooling to room temperature in the furnace.

7. The preparation method according to any one of claims 3-6, characterized in that, The preparation method further includes fine grinding of the synthesized ceramic powder; the fine grinding parameters include: the mass ratio of ceramic powder: anhydrous ethanol: ball milling media = 1:(0.5~0.9):(1.2~1.8), and the fine grinding time is 4~8 hours.

8. The preparation method according to any one of claims 3-7, characterized in that, The finely ground and dried ceramic powder is granulated by adding a binder, then pressed and molded to obtain a ceramic green body, which is then sintered. The amount of binder added is 4 to 8 wt% of the ceramic powder; preferably, the binder is polyvinyl alcohol.

9. The preparation method according to any one of claims 3-8, characterized in that, The conditions for removing the plastic include: heating to 700-800°C at a heating rate not exceeding 2°C / min, holding at that temperature for less than 3 hours, and then cooling with the furnace.

10. The preparation method according to any one of claims 3-9, characterized in that, The preparation method further includes: coating the surface of the obtained bismuth calcium titanate-based high-entropy piezoelectric ceramic with platinum, drying and calcining platinum to cure it, and finally performing polarization treatment. The conditions for the platinum curing treatment include: heating to 800-900°C at a heating rate not exceeding 2°C / min and holding at that temperature for no more than 60 minutes, and then cooling to room temperature in the furnace. The polarization treatment conditions include: applying an electric field of 8 to 12 kV / mm at 160 to 200°C for 10 to 20 minutes.

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