Sodium bismuth titanate-based high-entropy piezoelectric ceramic material and preparation method thereof

Abstract

According to the sodium bismuth titanate-based high-entropy piezoelectric ceramic material and the preparation method thereof, a high-entropy phase Bi < 0.2 > Na < 0.2 > Ba < 0.2 > Sr < 0.2 > Ca < 0.2 > TiO < 3 > is introduced into a classic ferroelectric material Bi < 0.5 > Na < 0.5 > TiO < 3 >, and lattice distortion, disorder degree and electric domain morphology in a system are subjected to multi-dimensional regulation and control, so that the piezoelectric property in the system is effectively enhanced (the piezoelectric coefficient d33 and the electromechanical coupling coefficient Kp are improved), and the piezoelectric property is improved. The road of performance regulation and control of the lead-free piezoelectric material is further broadened, and an important research basis is provided for development and design of related sodium bismuth titanate-based piezoelectric devices. The sodium bismuth titanate-based high-entropy piezoelectric ceramic material prepared by the invention is excellent in piezoelectric property, simple in preparation process, good in repeatability, low in cost and suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of functional ceramic materials technology, and in particular to a sodium bismuth titanate-based high-entropy piezoelectric ceramic material and its preparation method. Background Technology

[0002] With the rapid development of 5G / 6G communication, precision actuation, and sensing technologies, modern electronic devices are increasingly demanding high-performance, highly stable, and environmentally friendly piezoelectric materials. Piezoelectric ceramics, as core materials for converting mechanical energy into electrical energy, directly determine the precision and reliability of related devices based on their performance. Currently, the commercial piezoelectric market is still dominated by lead-based materials, such as lead zirconate titanate. However, the lead pollution problems caused by these materials during production, use, and disposal seriously contradict the global trend of green development. Therefore, developing high-performance lead-free piezoelectric ceramics has become an urgent task. Among numerous lead-free candidate materials, sodium bismuth titanate-based ceramics stand out due to their high Bi content at the A-site. 3+ With Pb 2+ Having the same 6s 2 With its lone-pair electron configuration, sodium bismuth titanate (SBT) ceramics exhibit high Curie temperatures and large spontaneous polarization intensities, making them one of the most promising systems to replace lead-based piezoelectric materials. However, the inherent high coercivity and low depolarization temperature of SBT ceramics limit their piezoelectric properties. A common solution is to optimize the piezoelectric properties of SBT ceramics through relaxation behavior. However, traditional relaxation construction methods often have certain uncertainties, and exploring the multidimensional correlation between microstructure, relaxation, and piezoelectricity relies on high-throughput material preparation, which seriously hinders the development and research of strong piezoelectric systems based on SBT. Therefore, how to more directly and effectively improve the piezoelectric properties of SBT ceramic materials has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0003] To address the above shortcomings, this invention provides a sodium bismuth titanate-based high-entropy piezoelectric ceramic material and its preparation method. This sodium bismuth titanate-based high-entropy piezoelectric ceramic material exhibits excellent piezoelectric coefficient d. 33 electromechanical coupling coefficient K p This effectively enhances the piezoelectric properties.

[0004] The technical solution to achieve the objective of this invention is:

[0005] A sodium bismuth titanate-based high-entropy piezoelectric ceramic material, wherein the chemical composition of the sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2TiO3, where x is the number of moles, ranging from 0.05 to 0.25.

[0006] A method for preparing a sodium bismuth titanate-based high-entropy piezoelectric ceramic material, comprising the above-mentioned sodium bismuth titanate-based high-entropy piezoelectric ceramic material, the method comprising the following steps:

[0007] 1) According to the stoichiometric ratio (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3: Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder were weighed as raw materials and mixed. The mixture was ball-milled once, and then dried by liquid transfer to obtain the precursor powder.

[0008] 2) The precursor powder obtained in step 1) is pre-calcined to obtain pre-calcined powder;

[0009] 3) The pre-fired powder obtained in step 2) is subjected to secondary ball milling, and then dried by liquid transfer to obtain ceramic powder;

[0010] 4) The ceramic powder obtained in step 3) is granulated, pressed into sheets, and the binder is removed to obtain a ceramic green body;

[0011] 5) The ceramic green body obtained in step 4) is sintered, polished, and then calcined with silver to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0012] Preferably, in step 1), the purity of the raw material powder is ≥99.0%, and the raw material is dried at 120 ℃ for 6 h before mixing; the parameters of the ball milling include: the ball milling medium is anhydrous ethanol, the rotation speed is 150 r / min, the ball milling time is 24 h, and the powder after ball milling is dried at a constant temperature of 95 ℃.

[0013] Preferably, the pre-firing temperature in step 2) is 850 °C and the pre-firing time is 3 h.

[0014] Preferably, the parameters for the secondary ball milling in step 3) include: the ball milling medium is anhydrous ethanol, the rotation speed is 150 r / min, and the ball milling time is 24 h; the powder after ball milling is dried at a constant temperature of 95 ℃.

[0015] Preferably, the binder used for granulation in step 4) is polyvinyl alcohol (5 wt% PVA); the pressing parameters include: a pressure of 520 MPa, grinding the ceramic powder evenly and pressing it into a circular ceramic green body with a diameter of 12 mm; the debinding procedure is: heating to 200 ℃ at a heating rate of 2 ℃ / min and holding for 2 h, then heating to 300 ℃ and holding for 1 h, then heating to 500 ℃ and holding for 10 h, and then naturally cooling to room temperature.

[0016] Preferably, the sintering temperature in step 5) is 1130 ℃ and the sintering time is 2 h; the sintered ceramic sheet is polished to a thickness of 1 mm; the upper and lower surfaces of the polished ceramic sheet are uniformly coated with a high-temperature silver paste electrode with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min.

[0017] This technical solution has the following advantages compared with existing technologies:

[0018] The (1-x)Bi prepared by this technical solution 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 By varying the content of the high-entropy phase in TiO3 (x=0.05~0.25) ceramic materials, the disordered state can be quantitatively introduced into the system, thereby effectively controlling its lattice structure, domain structure, and piezoelectric properties. Experimental results show that the maximum piezoelectric coefficient d of the sodium bismuth titanate-based high-entropy piezoelectric ceramic material provided by this technical solution is [value missing]. 33 Up to 128 pC / N, maximum electromechanical coupling coefficient K p It can reach 0.42. Attached Figure Description

[0019] Figure 1 (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 XRD pattern of TiO3 ceramics;

[0020] Figure 2 (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2The piezoelectric coefficient d of TiO3 ceramics 33 Curve showing the change of x;

[0021] Figure 3 (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 The electromechanical coupling coefficient K of TiO3 ceramics p The curve showing how x changes. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings, embodiments, and comparative examples. However, this is not intended to limit the scope of the invention. The following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The specific process parameters in the following embodiments are only preferred numerical examples. That is, those skilled in the art can select parameters within a suitable range based on the description herein, and are not intended to be limited to the specific numerical values ​​in the examples below. Unless otherwise specified, the following embodiments and comparative examples are made by mixing Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder, and TiO2 powder with a purity greater than 99% in a stoichiometric ratio.

[0023] All piezoelectric performance tests in the following examples and comparative examples were performed using quasi-static d-tests. 33 The tester measures the piezoelectric coefficient d of sodium bismuth titanate-based piezoelectric ceramic materials. 33 The resonance spectrum of sodium bismuth titanate-based piezoelectric ceramic material was tested using a high-temperature dielectric integrated measurement system, and the electromechanical coupling coefficient K of the ceramic material was calculated using equation (1). p : (1);

[0024] In equation (1), f r and f a These are the resonant frequency and the anti-resonant frequency, respectively.

[0025] Example 1:

[0026] The chemical composition of sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2TiO3, where x is 0.05, has an entropy value that can be calculated according to equation (2):

[0027] (2);

[0028] In equation (2), R is the gas constant, x i Let i be the mole fraction of any i component; the entropy value can be obtained as 0.74R using formula (2);

[0029] The preparation method comprises the following steps:

[0030] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder, and dry them at 120 ℃ for 6 h. Weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0031] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0032] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0033] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0034] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0035] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0036] 7) Debinding: The round ceramic green body pressed in step 6) is heated to 200 ℃ at a heating rate of 2 ℃ / min and held for 2 h, then heated to 300 ℃ and held for 1 h, then heated to 500 ℃ and held for 10 h, and then naturally cooled to room temperature to obtain the round ceramic green body after debinding.

[0037] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0038] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0039] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0040] The obtained 0.95Bi 0.5 Na 0.5 TiO3-0.05Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0041] Example 2:

[0042] The chemical composition of sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3, where x is 0.10, has an entropy value that can be calculated according to equation (2):

[0043] (2);

[0044] In equation (2), R is the gas constant, x i Let i be the mole fraction of any i-th component; the entropy value can be obtained as 0.78R using formula (2);

[0045] The preparation method comprises the following steps:

[0046] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder, and dry them at 120 ℃ for 6 h. Weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0047] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0048] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0049] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0050] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0051] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0052] 7) Debinding: The round ceramic green body pressed in step 6) is heated to 200 ℃ at a heating rate of 2 ℃ / min and held for 2 h, then heated to 300 ℃ and held for 1 h, then heated to 500 ℃ and held for 10 h, and then naturally cooled to room temperature to obtain the round ceramic green body after debinding.

[0053] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0054] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0055] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0056] The obtained 0.9Bi 0.5 Na 0.5 TiO3-0.1Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0057] Example 3:

[0058] The chemical composition of sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3, where x is 0.15, has an entropy value that can be calculated according to equation (2):

[0059] (2);

[0060] In equation (2), R is the gas constant, x i Let i be the mole fraction of any i-th component; the entropy value can be obtained as 0.83R using formula (2);

[0061] The preparation method comprises the following steps:

[0062] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder, and dry them at 120 ℃ for 6 h. Weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0063] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0064] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0065] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0066] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0067] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0068] 7) Debinding: The pressed circular ceramic green body from step 6) is heated to 200℃ at a rate of 2℃ / min and held for 2 hours, then heated to 300℃ and held for 1 hour, then heated to 500℃ and held for 10 hours. It is then allowed to cool naturally to room temperature to obtain the debinded circular ceramic green body.

[0069] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0070] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0071] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0072] The obtained 0.85Bi 0.5 Na 0.5 TiO3-0.15Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0073] Example 4:

[0074] The chemical composition of sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3, where x is 0.20, has an entropy value that can be calculated according to equation (2):

[0075] (2);

[0076] In equation (2), R is the gas constant, x iLet i be the mole fraction of any i-th component; the entropy value can be obtained as 0.88R using formula (2);

[0077] The preparation method comprises the following steps:

[0078] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder, and dry them at 120 ℃ for 6 h. Weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0079] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0080] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0081] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0082] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0083] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0084] 7) Debinding: The pressed circular ceramic green body from step 6) is heated to 200℃ at a rate of 2℃ / min and held for 2 hours, then heated to 300℃ and held for 1 hour, then heated to 500℃ and held for 10 hours. It is then allowed to cool naturally to room temperature to obtain the debinded circular ceramic green body.

[0085] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0086] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0087] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0088] The obtained 0.8Bi 0.5 Na 0.5 TiO3-0.2Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0089] Example 5:

[0090] The chemical composition of sodium bismuth titanate-based high-entropy piezoelectric ceramic material is: (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3, where x is 0.25, has an entropy value that can be calculated according to equation (2):

[0091] (2);

[0092] In equation (2), R is the gas constant, x i Let i be the mole fraction of any i-th component; the entropy value can be obtained as 0.92R using formula (2);

[0093] The preparation method comprises the following steps:

[0094] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder, and dry them at 120 ℃ for 6 h. Weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0095] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0096] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0097] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0098] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0099] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0100] 7) Debinding: The round ceramic green body pressed in step 6) is heated to 200 ℃ at a heating rate of 2 ℃ / min and held for 2 h, then heated to 300 ℃ and held for 1 h, then heated to 500 ℃ and held for 10 h, and then naturally cooled to room temperature to obtain the round ceramic green body after debinding.

[0101] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0102] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0103] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

[0104] The obtained 0.75Bi 0.5 Na 0.5 TiO3-0.25Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0105] Comparative example:

[0106] The chemical composition of sodium bismuth titanate piezoelectric ceramic material is: Bi 0.5 Na 0.5 TiO3

[0107] The preparation method comprises the following steps:

[0108] 1) Weighing raw materials: Calculate the required mass of raw materials, weigh Bi2O3 powder, Na2CO3 powder and TiO2 powder, dry them at 120 ℃ for 6 h, and weigh the dried raw materials according to the stoichiometric ratio of the above chemical formulas.

[0109] 2) Mixing and ball milling: Place the weighed raw materials from step 1) into a ball mill jar (agate jar), use anhydrous ethanol as the grinding medium, and ball mill for 24 hours at a speed of 150 r / min.

[0110] 3) Discharge and drying: Transfer the ball-milled material from step 2) into a beaker using a dropper and place it in a water bath to dry at a constant temperature of 95 ℃;

[0111] 4) Pre-calcined powder: The powder dried in step 3) is manually ground in a mortar and pestle. After being ground evenly, it is placed in a corundum crucible and pre-calcined in a muffle furnace at a temperature of 850 ℃ for 3 h with a heating rate of 5 ℃ / min.

[0112] 5) Secondary ball milling: The powder pre-calcined in step 4) is ball-milled again using the process used in steps 2) and 3), dried, and then ground into a uniform powder.

[0113] 6) Granulation and tableting: Weigh the powder after grinding in step 5), add polyvinyl alcohol (5 wt% PVA) as a binder, grind evenly, put the powder into a tableting mold with a diameter of 12 mm, and press it into a round ceramic green body using a tableting machine at a pressure of 520 MPa.

[0114] 7) Debinding: The round ceramic green body pressed in step 6) is heated to 200 ℃ at a heating rate of 2 ℃ / min and held for 2 h, then heated to 300 ℃ and held for 1 h, then heated to 500 ℃ and held for 10 h, and then naturally cooled to room temperature to obtain the round ceramic green body after debinding.

[0115] 8) Sintering: The circular ceramic green body obtained in step 7) after the binder has been removed is sintered at 1130 °C for 2 h at a heating rate of 5 °C / min.

[0116] 9) Polishing and grinding: Polish the sintered circular ceramic material from step 8) to a thickness of 1 mm using a polishing machine;

[0117] 10) Silver calcination: The upper and lower surfaces of the polished circular ceramic material in step 9) are uniformly coated with high-temperature silver paste electrodes with a diameter of 10 mm, and then calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate piezoelectric ceramic material.

[0118] For the prepared Bi 0.5 Na 0.5 XRD patterns and piezoelectric properties were tested on TiO3 ceramic samples.

[0119] Figure 1 The XRD patterns of the sodium bismuth titanate-based high-entropy ceramic materials prepared in Examples 1-5 and the sodium bismuth titanate ceramic materials prepared in the comparative examples show that (1-x)Bi 0.5 Na 0.5 TiO3-xBi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3 (x=0, 0.05, 0.10, 0.15, 0.20, 0.25) all exhibited a high-quality perovskite pure phase. Within the instrument's detection accuracy range, no obvious second phase was observed.

[0120] Figure 2 The piezoelectric coefficients d of the sodium bismuth titanate-based high-entropy ceramic materials prepared in Examples 1-5 and the sodium bismuth titanate ceramic materials prepared in the comparative examples are shown. 33 The curve showing the change of x indicates that as the content of the high-entropy phase increases, the piezoelectric coefficient d of the prepared ceramic material increases. 33 The piezoelectric coefficient d increases monotonically, reaching a maximum of 122 pC / N at x=0.25. The high-entropy ceramic materials based on sodium bismuth titanate prepared in Examples 1-5 all have a higher piezoelectric coefficient d than the sodium bismuth titanate ceramic materials prepared in the comparative example. 33 The high entropy indicates that the introduction of the high-entropy phase effectively enhances the piezoelectric properties of the sodium bismuth titanate-based ceramic material system.

[0121] Figure 3 The electromechanical coupling coefficient K is the electromechanical coupling coefficient of the sodium bismuth titanate-based high-entropy ceramic materials prepared in Examples 1-5 and the sodium bismuth titanate ceramic materials prepared in the comparative example. p The curve showing the change with x indicates that as the content of the high-entropy phase increases, the piezoelectric coefficient K of the prepared ceramic material increases. p It shows a monotonically increasing trend, reaching a maximum value of 0.42 when x=0.25. The electromechanical coupling coefficient K of the sodium bismuth titanate-based high-entropy ceramic materials prepared in Examples 1-5 is significantly higher than that of the sodium bismuth titanate ceramic materials prepared in the comparative example. p The high entropy indicates that the introduction of the high-entropy phase effectively enhances the piezoelectric properties of the sodium bismuth titanate-based ceramic material system.

[0122] Table 1 shows the piezoelectric properties of sodium bismuth titanate-based high-entropy piezoelectric ceramic materials:

[0123] x <![CDATA[d 33 (pN / C)]]> <![CDATA[K p ]]> Comparative Example 0 81 0.26 Example 1 0.05 84 0.30 Example 2 0.10 90 0.32 Example 3 0.15 96 0.34 Example 4 0.20 108 0.40 Example 5 0.25 122 0.42 .

Claims

1. A sodium bismuth titanate-based high-entropy piezoelectric ceramic material, characterized in that, The chemical composition of the sodium bismuth titanate-based high-entropy piezoelectric ceramic material is (1- x )Bi 0.5 Na 0.5 TiO3- x Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3, in which x The value is the number of moles, ranging from 0.05 to 0.

25.

2. The sodium bismuth titanate-based high-entropy piezoelectric ceramic material according to claim 1, characterized in that, The configurational entropy of the sodium bismuth titanate-based high-entropy piezoelectric ceramic material is 0.7 R~1.0 R.

3. A method for preparing a sodium bismuth titanate-based high-entropy piezoelectric ceramic material, characterized in that, The method, comprising the sodium bismuth titanate-based high-entropy piezoelectric ceramic material according to any one of claims 1 or 2, includes the following steps: 1) According to the stoichiometric ratio (1- x )Bi 0.5 Na 0.5 TiO3- x Bi 0.2 Na 0.2 Ba 0.2 Sr 0.2 Ca 0.2 TiO3: Bi2O3 powder, Na2CO3 powder, BaCO3 powder, SrCO3 powder, CaCO3 powder and TiO2 powder were weighed as raw materials and mixed. The mixture was ball-milled once, and then dried by liquid transfer to obtain the precursor powder. 2) The precursor powder obtained in step 1) is pre-calcined to obtain pre-calcined powder; 3) The pre-fired powder obtained in step 2) is subjected to secondary ball milling, and then dried by liquid transfer to obtain ceramic powder; 4) The ceramic powder obtained in step 3) is granulated, pressed into sheets, and the binder is removed to obtain a ceramic green body; 5) The ceramic green body obtained in step 4) is sintered, polished, and then calcined with silver to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

4. The method for preparing the sodium bismuth titanate-based high-entropy piezoelectric ceramic material according to claim 3, characterized in that, In step 1), the purity of the raw material powder is ≥99.0%, and the raw material is dried at 120 ℃ for 6 h before mixing; the parameters of the ball milling include: the ball milling medium is anhydrous ethanol, the rotation speed is 150 r / min, the ball milling time is 24 h, and the powder after ball milling is dried at a constant temperature of 95 ℃.

5. The method for preparing the sodium bismuth acid-based high-entropy piezoelectric ceramic material according to claim 3, characterized in that, The pre-firing temperature in step 2) is 850 ℃ and the pre-firing time is 3 h.

6. The method for preparing the sodium bismuth acid-based high-entropy piezoelectric ceramic material according to claim 3, characterized in that, The parameters for the secondary ball milling in step 3) include: the ball milling medium is anhydrous ethanol, the rotation speed is 150 r / min, and the ball milling time is 24 h; the powder after ball milling is dried at a constant temperature of 95 ℃.

7. The method for preparing the sodium bismuth acid-based high-entropy piezoelectric ceramic material according to claim 3, characterized in that, The binder used for granulation in step 4) is 5 wt% polyvinyl alcohol; the pressing parameters include: a pressure of 520 MPa, grinding the ceramic powder evenly and pressing it into a circular ceramic green body with a diameter of 12 mm; the debinding procedure is: heating to 200 ℃ at a heating rate of 2 ℃ / min and holding for 2 h, then heating to 300 ℃ and holding for 1 h, then heating to 500 ℃ and holding for 10 h, and then naturally cooling to room temperature.

8. The method for preparing the sodium bismuth acid-based high-entropy piezoelectric ceramic material according to claim 3, characterized in that, The sintering temperature in step 5) is 1130 ℃ and the sintering time is 2 h. The sintered ceramic sheet is polished to a thickness of 1 mm. The upper and lower surfaces of the polished ceramic sheet are uniformly coated with a high-temperature silver paste electrode with a diameter of 10 mm. Then, it is calcined at 800 ℃ for 20 min to obtain sodium bismuth titanate-based high-entropy piezoelectric ceramic material.

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