A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic and preparation method thereof

Abstract

The present invention discloses a lead-free piezoelectric ceramic based on sodium bismuth titanate co-doped at A and B sites and a preparation method thereof. The preparation method adopted by the present invention is to dope lanthanum tantalate into the sodium bismuth titanate ceramic matrix, and to dope LaTaO4 to make La 3+ The Ta enters the A site of the perovskite structure, while the Ta enters the B site, inducing a ferroelectric-nonpolar phase transition and increasing crystal structural distortion. This results in an A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic, resulting in exceptionally high electrostrain performance, making it ideal for use in piezoelectric actuators. The preparation method of the present invention offers simple steps, stable product performance, and suitability for mass production.

Description

Technical Field

[0001] The present invention belongs to the field of piezoelectric ceramics, in particular to an A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic and a preparation method thereof. Background Art

[0002] Ferroelectric (FE) ceramics have been widely used in actuators, sensors and ultrasonic motors. Lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) is one of the most widely used functional ceramics. For PZT, typical doping ions (such as La 3+ 、Bi 3+ 、Nb 5+ and Sb 5+ ) have been used to increase ferroelectric properties.

[0003] Due to the volatility of lead, there is a need to develop competitive lead-free ferroelectric ceramics. Recently, many researchers have devoted themselves to the study of ferroelectricity and electric field-induced strain based on binary solid solutions of bismuth sodium titanate (BNT), such as BNT-BT, BNT-BKT, and BNT-ST, which are considered to be the most promising alternatives to PZT as materials for actuator applications.

[0004] Numerous studies have shown that La-doped 3+ Entering the A site of the perovskite structure can induce a ferroelectric-nonpolar phase transition, which can produce huge strain. Inverse piezoelectric constant (the ratio of displacement to electric field, S / E)d 33 * As high as 650pm / V; similarly, La is doped into BNT-BT 3+ , which can also enhance ferroelectricity. The highest strain at 70kV / cm is 0.35. Secondly, doping Ta5+ into the B site of the perovskite structure can cause structural distortion, thereby increasing the electrostrain. Summary of the Invention

[0005] In order to further improve the strain properties of NBT-based lead-free ferroelectric ceramics, the present invention provides a preparation method of A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics to obtain A- and B-site co-doped sodium bismuth titanate-based large-strain lead-free piezoelectric ceramics, so that the lead-free piezoelectric ceramics have ultra-large electrostrain properties and are suitable for use in piezoelectric actuators.

[0006] The present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a method for preparing an A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic, wherein lanthanum tantalate is doped in the sodium bismuth titanate ceramic matrix, and LaTaO4 is used for doping. 3+It enters the A site of the perovskite structure, and Ta enters the B site of the perovskite structure, inducing a ferroelectric-nonpolar phase transition and increasing the crystal structure distortion, thereby obtaining A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics.

[0008] In a second aspect, the present invention provides another method for preparing an A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic, comprising:

[0009] Preparation of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 powder, also known as NBT-BT powder: Using a traditional solid-phase method, BiO2, Na2CO3, Ba2CO3, and TiO2 are sequentially mixed, ball-milled, dried, pre-calcined, ball-milled again, and dried again;

[0010] La2O3 and Ta2O5 were added to 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 powder, wherein the molar ratio of La2O3 to Ta2O5 was 1:1. The mixing, ball milling, drying, pre-calcining, secondary ball milling and drying processes were sequentially adopted to obtain NBT-BT+xLaTaO4 solid solution powder, wherein 0.02≤x≤0.04, and x is the mass ratio of LaTaO4 in the sodium bismuth titanate-based lead-free piezoelectric ceramic to the sodium bismuth titanate-based lead-free piezoelectric ceramic.

[0011] In a third aspect, the present invention provides another method for preparing an A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic, comprising:

[0012] Step 1) Preparation of 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 powder, i.e., NBT-BT powder: using a traditional solid phase method, BiO2, Na2CO3, Ba2CO3, and TiO2, sequentially through mixing, ball milling, drying, pre-calcining, secondary ball milling, and secondary drying;

[0013] Step 2) Adding La2O3 and Ta2O5 to the NBT-BT powder: First, weigh La2O3 and Ta2O5 powders with a molar ratio of 1:1, and add them to the NBT-BT powder prepared in step 1) according to the NBT-BT+xLaTaO4 chemical ratio, 0.02≤x≤0.04, where x is the mass ratio of LaTaO4 to sodium bismuth titanate-based lead-free piezoelectric ceramics. Then, mixing, ball milling, drying, pre-calcining, secondary ball milling, and secondary drying are carried out in sequence to obtain NBT-BT+xLaTaO4 powder;

[0014] Step 3), powder pressing: adding 3wt% to 7wt% of polyvinyl alcohol solution to NBT-BT+xLaTaO4 powder to granulate, and then using a press to press into round tablets;

[0015] Step 4), sintering: remove the polyvinyl alcohol from the pressed disc, then continue to heat it to 1050-1250° C. and keep it for 1-6 hours, and then cool it to obtain the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic.

[0016] The A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics prepared by the above three methods have ultra-large strain properties, and the strain value under an electric field of 75 kV / cm is greater than 0.34%.

[0017] Furthermore, in the step 1), the ball milling time is 11-24 hours, the pre-calcination temperature is 800-900° C., the pre-calcination time is 1-6 hours, and the secondary ball milling time is 11-24 hours.

[0018] Furthermore, in the step 2), the ball milling time is 4-7 hours, the pre-calcination temperature is 850-950° C., the pre-calcination time is 1-6 hours, and the secondary ball milling time is 4-7 hours.

[0019] After ball milling (i.e., primary ball milling) and secondary ball milling, a powder with uniform and refined composition is obtained, thereby further improving the comprehensive performance of sodium bismuth titanate-based lead-free piezoelectric ceramics.

[0020] The pre-firing temperature selected in steps 1) and 2) can cause the carbon element and part of the oxygen element in the carbide and oxide to be ablated, so as to prepare sodium bismuth titanate-based lead-free piezoelectric ceramics having the above-mentioned chemical composition, and this method can further improve the piezoelectric properties of sodium bismuth titanate-based lead-free piezoelectric ceramics.

[0021] Furthermore, in the step 4), the heating rate is 1-5°C / min, and the cooling method is furnace cooling.

[0022] Furthermore, in the step 4), the sintering temperature is 1100-1200° C. and the holding time is 2-4 hours, thereby further improving the temperature stability of the sodium bismuth titanate-based lead-free piezoelectric ceramic.

[0023] Furthermore, the ball milling and secondary ball milling are both wet ball milling, the solvent is anhydrous ethanol, and the ball milling speed is 200-300 rpm.

[0024] Furthermore, the pre-firing temperature in step 1) is preferably 850°C, the pre-firing temperature in step 2) is preferably 900°C; and the sintering temperature in step 4) is 1140°C.

[0025] In a fourth aspect, the present invention provides an A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic, which is prepared using the above-mentioned preparation method.

[0026] The technical solution of the present invention has the following advantages:

[0027] The present invention utilizes LaTaO4 doping to make La 3+ Entering the A site of the perovskite structure, Ta enters the B site of the perovskite structure, inducing a ferroelectric-nonpolar phase transition and increasing the crystal structure distortion, thereby obtaining a large strain lead-free piezoelectric ceramic, making its strain value greater than 0.34% under an electric field of 75kv / cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and specific implementation methods.

[0029] Figure 1 This is the XRD phase result diagram in the test example of the present invention;

[0030] Figure 2 This is the SEM microstructure diagram of the product obtained in Example 1 of the present invention;

[0031] Figure 3 This is the SEM microstructure diagram of the product obtained in Example 2 of the present invention;

[0032] Figure 4 This is the SEM microstructure diagram of the product obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0033] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0034] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0035] Example 1

[0036] This embodiment provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, the steps of which are as follows:

[0037] 1) 2.503 g of Na2CO3, 1.190 g of BaCO3, 11.061 g of Bi2O3, and 8.15 g of TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder 1;

[0038] 2) 0.194 g La2O3 and 0.264 g Ta2O5 were added to the mixed powder 1 obtained in step 1), and the mixture was wet-milled in a ball mill using anhydrous ethanol for 12 h at a speed of 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 900°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol for 6 h at a speed of 250 rpm, and after ball milling, the material was dried at 60°C for 6 h to obtain mixed powder 2;

[0039] 3) pressing the mixed powder obtained in step 2) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0040] 4) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0041] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this embodiment is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-0.02LaTaO4, and its SEM microstructure is as follows: Figure 2 shown.

[0042] Example 2

[0043] This embodiment provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, the steps of which are as follows:

[0044] 1) 2.503 g of Na2CO3, 1.190 g of BaCO3, 11.061 g of Bi2O3, and 8.15 g of TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder 1;

[0045] 2) 0.291 g La2O3 and 0.395 g Ta2O5 were added to the mixed powder 1 obtained in step 1), and the mixture was wet-milled in a ball mill using anhydrous ethanol for 12 h at a speed of 250 rpm. After ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 900°C for 3 h. The sintered material was wet-milled in a ball mill using anhydrous ethanol for 6 h at a speed of 250 rpm. After ball milling, the material was dried at 60°C for 6 h to obtain mixed powder 2;

[0046] 3) pressing the mixed powder obtained in step 2) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0047] 4) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0048] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this embodiment is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-0.03LaTaO4, and its SEM microstructure is as follows: Figure 3 shown.

[0049] Example 3

[0050] This embodiment provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, the steps of which are as follows:

[0051] 1) 2.503 g of Na2CO3, 1.190 g of BaCO3, 11.061 g of Bi2O3, and 8.15 g of TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder 1;

[0052] 2) 0.389 g La2O3 and 0.527 g Ta2O5 were added to the mixed powder 1 obtained in step 1), and the mixture was wet-milled in a ball mill using anhydrous ethanol for 12 h at a speed of 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 900°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol for 6 h at a speed of 250 rpm, and after ball milling, the material was dried at 60°C for 6 h to obtain mixed powder 2;

[0053] 3) pressing the mixed powder obtained in step 2) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0054] 4) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0055] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this embodiment is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-0.04LaTaO4, and its SEM microstructure is as follows: Figure 4 shown.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, the steps of which are as follows:

[0058] 1) 2.503 g Na2CO3, 1.190 g BaCO3, 11.061 g Bi2O3, and 8.15 g TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder;

[0059] 2) pressing the mixed powder obtained in step 1) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0060] 3) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0061] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this comparative example is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3.

[0062] Comparative Example 2

[0063] This comparative example provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, comprising the following steps:

[0064] 1) 2.503 g of Na2CO3, 1.190 g of BaCO3, 11.061 g of Bi2O3, and 8.15 g of TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder 1;

[0065] 2) 0.097 g La2O3 and 0.132 g Ta2O5 were added to the mixed powder 1 obtained in step 1), and the mixture was wet-milled in a ball mill using anhydrous ethanol for 12 h at a speed of 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 900°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol for 6 h at a speed of 250 rpm, and after ball milling, the material was dried at 60°C for 6 h to obtain mixed powder 2;

[0066] 3) pressing the mixed powder obtained in step 2) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0067] 4) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0068] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this comparative example is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-0.01LaTaO4.

[0069] Comparative Example 3

[0070] This comparative example provides a method for preparing sodium bismuth titanate-based lead-free piezoelectric ceramics, the steps of which are as follows:

[0071] 1) 2.503 g of Na2CO3, 1.190 g of BaCO3, 11.061 g of Bi2O3, and 8.15 g of TiO2 were mixed and wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 850°C for 3 h; the sintered material was wet-milled in a ball mill using anhydrous ethanol as the milling solvent, the milling time was 12 h, and the milling speed was 250 rpm; after ball milling, the material was dried at 60°C for 12 h to obtain a mixed powder 1;

[0072] 2) 0.486 g La2O3 and 0.659 g Ta2O5 were added to the mixed powder 1 obtained in step 1), and the mixture was wet-milled in a ball mill using anhydrous ethanol for 12 h at a speed of 250 rpm. After ball milling, the material was dried at 60°C for 24 h, and the dried material was sintered in air at 900°C for 3 h. The sintered material was wet-milled in a ball mill using anhydrous ethanol for 6 h at a speed of 250 rpm. After ball milling, the material was dried at 60°C for 6 h to obtain mixed powder 2;

[0073] 3) pressing the mixed powder obtained in step 2) into a disc with a diameter of 10 mm and a thickness of 1.0 mm at a pressure of 10 MPa for 60 seconds;

[0074] 4) Sintering the ceramic green body obtained in step 3) in air at a sintering temperature of 1140° C. for 3 hours.

[0075] The general formula of the sodium bismuth titanate-based lead-free piezoelectric ceramic provided in this comparative example is: 0.94Na0.5Bi0.5TiO3-0.06BaTiO3-0.05LaTaO4.

[0076] Test Case

[0077] The sodium bismuth titanate-based lead-free piezoelectric ceramics obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to XRD phase analysis, SEM microstructure testing, and strain performance testing.

[0078] The XRD phase analysis equipment was from PANalytical BV, the Netherlands, and the test conditions were a copper target.

[0079] The SEM microstructure testing equipment was the German GeminiSEM300, and the testing condition was the secondary electron mode.

[0080] The strain performance testing equipment was from aixACCT Systems GmbH, Germany, and the testing condition was 10 Hz.

[0081] The test results are shown in Table 1.

[0082] Table 1

[0083] Strain under 75kV electric field (%) Example 1 (x=0.02) 0.39 Example 2 (x=0.03) 0.56 Example 3 (x=0.04) 0.35 Comparative Example 1 (x=0.00) 0.34 Comparative Example 2 (x=0.01) 0.25 Comparative Example 3 (x=0.05) 0.18

[0084] XRD phase results are as follows Figure 1 As shown, all phases present a typical perovskite structure, and with the increase of x content, the crystal symmetry gradually increases.

[0085] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics, characterized in that: Lanthanum tantalate is doped into sodium bismuth titanate ceramic matrix by LaTaO4 doping. 3+ Entering the A site of the perovskite structure, Ta enters the B site of the perovskite structure, inducing a ferroelectric-nonpolar phase transition and increasing the crystal structure distortion, thereby obtaining A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics; the specific preparation method is as follows: Preparation of 0.94Na 0.5 Bi 0.5 TiO3-0.06BaTiO3 powder, also known as NBT-BT powder, is prepared by a traditional solid-phase method by mixing BiO2, Na2CO3, Ba2CO3, and TiO2, followed by ball milling, drying, pre-calcination, secondary ball milling, and secondary drying. In 0.94Na 0.5 Bi 0.5 La2O3 and Ta2O5 are added to TiO3-0.06BaTiO3 powder, wherein the molar ratio of La2O3 to Ta2O5 is 1:

1. The mixing, ball milling, drying, pre-calcining, secondary ball milling and drying processes are sequentially adopted to obtain NBT-BT+xLaTaO4 solid solution powder, wherein 0.02≤x≤0.04, and x is the mass ratio of LaTaO4 in the sodium bismuth titanate-based lead-free piezoelectric ceramic to the sodium bismuth titanate-based lead-free piezoelectric ceramic.

2. A method for preparing A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics, characterized in that: Lanthanum tantalate is doped into sodium bismuth titanate ceramic matrix by LaTaO4 doping. 3+ Entering the A site of the perovskite structure, Ta enters the B site of the perovskite structure, inducing a ferroelectric-nonpolar phase transition and increasing the crystal structure distortion, thereby obtaining A- and B-site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramics; the specific preparation method is as follows: Step 1), prepare 0.94Na 0.5 Bi 0.5 TiO3-0.06BaTiO3 powder, also known as NBT-BT powder, is prepared by a traditional solid-phase method using BiO2, Na2CO3, Ba2CO3, and TiO2, followed by mixing, ball milling, drying, pre-calcining, secondary ball milling, and secondary drying. Step 2), adding La2O3 and Ta2O5 to the NBT-BT powder: first weigh La2O3 and Ta2O5 powders with a molar ratio of 1:1, and add them to the NBT-BT powder prepared in step 1) according to the chemical ratio of NBT-BT+xLaTaO4, 0.02≤x≤0.04, where x is the mass ratio of LaTaO4 in the sodium bismuth titanate-based lead-free piezoelectric ceramic to the sodium bismuth titanate-based lead-free piezoelectric ceramic, and sequentially prepare NBT-BT+xLaTaO4 powder by mixing, ball milling, drying, pre-calcining, secondary ball milling and secondary drying; Step 3), powder pressing: adding 3wt% to 7wt% of polyvinyl alcohol solution to NBT-BT+xLaTaO4 powder to granulate, and then using a press to press into round tablets; Step 4), sintering: remove the polyvinyl alcohol from the pressed disc, then continue to heat it to 1050-1250℃ and keep it for 1-6 hours. After cooling, obtain the A and B site co-doped sodium bismuth titanate based lead-free piezoelectric ceramic.

3. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 2, characterized in that: In the step 1), the ball milling time is 11-24 hours, the pre-calcination temperature is 800-900° C., the pre-calcination time is 1-6 hours, and the secondary ball milling time is 11-24 hours.

4. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 2, characterized in that: In the step 2), the ball milling time is 4-7 hours, the pre-calcination temperature is 850-950° C., the pre-calcination time is 1-6 hours, and the secondary ball milling time is 4-7 hours.

5. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 2, characterized in that: In the step 4), the heating rate is 1-5°C / min, and the cooling method is furnace cooling.

6. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 2, characterized in that: In the step 4), the sintering temperature is 1100-1200° C. and the holding time is 2-4 hours.

7. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 2, characterized in that: The pre-firing temperature in step 1) is 850°C, the pre-firing temperature in step 2) is 900°C, and the sintering temperature in step 4) is 1140°C.

8. The method for preparing the A and B site co-doped sodium bismuth titanate-based lead-free piezoelectric ceramic according to claim 1 or 2, characterized in that: The ball milling and secondary ball milling are both wet ball milling, the solvent is anhydrous ethanol, and the ball milling speed is 200-300 rpm.

9. A lead-free piezoelectric ceramic co-doped with sodium bismuth titanate at A and B sites, characterized in that: The invention discloses a novel nanostructured carbonyl phosphate ...

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