A non-stoichiometric bismuth sodium titanate ceramic material at site A, its preparation method, and its applications.

Abstract

This invention relates to the field of piezoelectric ceramic materials technology, and provides a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A-site, its preparation method, and its applications. The chemical formula of the sodium bismuth titanate ceramic material is Na. 0.5‑y Bi 0.5‑x TiO3, wherein 0≤x≤0.4, 0≤y≤0.4. This invention, through compositional design and control, prepares sodium bismuth titanate piezoelectric ceramics with non-chemically composed A-sites via solid-state sintering. Different A-site defects respectively improve the coercivity and piezoelectric coefficient of the sodium bismuth titanate piezoelectric ceramics. The matrix Na... 0.5 Bi 0.5 The coercive field of TiO3 ceramics is 70 kV / cm, and the piezoelectric coefficient d is... 33 A piezoelectric ceramic sample with a coercive field of 81 kV / cm at x = 0.03 and y = 0 can achieve a piezoelectric coefficient d of 95 pC / N. 33 .

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic materials technology, and particularly relates to a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A site, its preparation method, and its application. Background Technology

[0002] Piezoelectric ceramics, based on the positive and negative piezoelectric effects, can be used to make transducers, piezoelectric actuators, etc. A transducer is a device that can convert an input high-frequency electrical oscillation signal into mechanical vibration energy of the same frequency and radiate it outward. It can be used to make ultrasonic transducers, sensors, etc. Piezoelectric actuators achieve small and precise displacement controlled by electrical signals. They have unique advantages such as extremely fast response, extremely high displacement resolution, large output force, and low power consumption. They are widely used in various fields, such as scanning electron microscope probes, semiconductor manufacturing, medical ultrasound imaging, and industrial non-destructive testing equipment.

[0003] With industrial development, the application scenarios of transducers are becoming increasingly complex, such as high-frequency, high-voltage alternating electric fields and high-temperature environments. This places higher demands on the long-term operational stability of transducers. Increasing the coercivity of piezoelectric ceramics means that the electric domains within the material are less likely to be flipped by an external electric field or external stress, thus enhancing the device's resistance to depolarization. This ensures that the transducer can maintain its original polarization state and excellent electroacoustic conversion performance under high voltage, high temperature, and long-term continuous operation conditions. The high d-value of piezoelectric materials... 33 It can effectively improve the sensitivity of sensors, the response capability and deformation capability of piezoelectric actuators. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A site, thereby addressing the problems mentioned in the background art.

[0005] This invention is implemented as follows: a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A-site, wherein the chemical formula of the sodium bismuth titanate ceramic material with the non-stoichiometric composition at the A-site is Na. 0.5-y Bi 0.5-x TiO3, wherein 0≤x≤0.4, 0≤y≤0.4.

[0006] Preferably, x = 0.03 and y = 0.

[0007] Preferably, x = 0 and y = 0.03.

[0008] Another objective of this invention is a method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at site A, comprising the following steps: Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide, and sodium carbonate. The raw materials are dried, weighed by molar ratio, and then mixed with alcohol to obtain a mixed slurry. Drying: The slurry is dried to remove ethanol and ground to obtain a uniformly mixed raw material powder; Tableting and firing: Dry powder is pressed into shape using a mold and then fired in a high-temperature furnace; Ball milling and drying: Add alcohol to the fired ceramic blocks and pulverize them by ball milling to obtain a mixed slurry, then dry to obtain ceramic powder; Granulation and molding: Ceramic powder is sieved, PVA solution is added to it, it is ground, sieved again, pressed and shaped, and then statically pressed to form a ceramic green body; Debinding and sintering: The ceramic green body is debinded and sintered at high temperature, and after cooling, sodium bismuth titanate ceramic material with non-stoichiometric composition at position A is obtained.

[0009] Preferably, in the tableting and firing step, the pressing pressure is 8-12 MPa, the reaction temperature is 880-930℃, and the time is 3-3.5 h.

[0010] Preferably, in the granulation step, the pressure of grinding, sieving, and pressing is 15-18 MPa, and the pressure of static pressing is 235-265 MPa.

[0011] Preferably, in the glue removal step, the heat preservation temperature is 490-510℃ and the time is 60-80min.

[0012] Preferably, in the sintering step, the high-temperature sintering temperature is 1140-1170℃ and the time is 2-2.5h.

[0013] Another objective of this invention is the application of the sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A site in piezoelectric devices.

[0014] This invention relates to the field of piezoelectric ceramic materials technology, and provides a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A-site, its preparation method, and its applications. The chemical formula of the sodium bismuth titanate ceramic material is Na. 0.5-y Bi 0.5-x TiO3, wherein 0≤x≤0.4, 0≤y≤0.4. This invention, through compositional design and control, prepares sodium bismuth titanate piezoelectric ceramics with non-chemical composition at the A-site by solid-state sintering. Different A-site defects respectively improve the coercivity and piezoelectric coefficient of the sodium bismuth titanate piezoelectric ceramics. The matrix Na... 0.5 Bi 0.5 The coercive field of TiO3 ceramics is 70 kV / cm, and the piezoelectric coefficient d is... 33 A piezoelectric ceramic sample with a coercive field of 81 kV / cm at x = 0.03 and y = 0 can achieve a piezoelectric coefficient d of 95 pC / N. 33 . Attached Figure Description

[0015] Figure 1 The XRD pattern of the material prepared in Comparative Example 1 of this invention; Figure 2 The hysteresis loop of the material prepared in Comparative Example 1 of this invention; Figure 3 The XRD pattern of the material prepared in Example 1 of this invention; Figure 4 The hysteresis loop of the material prepared in Example 1 of this invention; Figure 5 The XRD pattern of the material prepared in Example 2 of this invention; Figure 6 The hysteresis loop of the material prepared in Example 2 of this invention; Figure 7 The XRD pattern of the material prepared in Example 3 of this invention; Figure 8 The hysteresis loop of the material prepared in Example 3 of this invention; Figure 9 The XRD pattern of the material prepared in Example 4 of this invention; Figure 10 The hysteresis loop of the material prepared in Example 4 of this invention; Figure 11 The XRD pattern of the material prepared in Example 5 of this invention; Figure 12 The XRD pattern of the material prepared in Example 6 of this invention; Figure 13 The XRD pattern of the material prepared in Example 7 of this invention; Figure 14 The XRD pattern of the material prepared in Example 8 of this invention; Figure 15 The figures show the coercive field statistics of Comparative Example 1 and Examples 1-4 of the present invention, and the piezoelectric coefficient statistics of the materials prepared in Comparative Example 1 and Examples 5-8. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0017] A non-stoichiometric bismuth sodium titanate ceramic material at the A-site, its preparation method, and its application, wherein the chemical formula of the non-stoichiometric bismuth sodium titanate ceramic material at the A-site is Na. 0.5-y Bi 0.5-xTiO3, wherein 0≤x≤0.4, 0≤y≤0.4, is prepared by the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, weigh them by molar ratio and add 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: The slurry is placed in an 80℃ oven for constant temperature drying to remove ethanol, and then ground with a mortar and pestle to obtain a uniformly mixed ceramic powder. (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into shape at 16 MPa, and fire the shaped ceramic sheet at 900℃ for 3 hours. (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled to obtain a slurry, and then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mixture is shaped at 12MPa, ground, and then passed through a 150-mesh sieve to ensure that the PVA is evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed under a pressure of 200MPa. Then, it isostatically pressed at 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material with non-chemical composition at position A.

[0018] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0019] Example 1: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0.01, y = 0, its preparation method includes the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.245:0.25 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0020] Example 2: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0.02, y = 0, its preparation method includes the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.24:0.25 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0021] Example 3: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-yBi 0.5- x TiO3, x = 0.03, y = 0, its preparation method includes the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.235:0.23 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0022] Example 4: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0.04, y = 0, its preparation method includes the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.23:0.25 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0023] Example 5: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0, y = 0.01, is prepared by the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.25:0.245 and 2 times the mass of alcohol is added to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0024] Example 6: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-yBi 0.5- x TiO3, x = 0, y = 0.02, is prepared by the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.25:0.24 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0025] Example 7: A non-stoichiometric bismuth titanate sodium ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0, y = 0.03, is prepared by the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.25:0.235 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0026] Example 8: A non-stoichiometric component sodium bismuth titanate ceramic material with the chemical formula Na 0.5-y Bi 0.5- x TiO3, x = 0, y = 0.04, is prepared by the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.25:0.23 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0027] Comparative Example 1: A sodium bismuth titanate ceramic material with the chemical formula Na 0.5-y Bi0.5-x TiO3, x = 0, y = 0, its preparation method includes the following steps: (1) Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide and sodium carbonate with a purity of ≥99.9%. After drying the raw materials in an oven at 120℃, they are weighed in a molar ratio of 1:0.25:0.25 and mixed with 2 times the mass of alcohol to obtain a mixed slurry. (2) Drying: Place the slurry in an 80℃ oven to dry at a constant temperature, remove the alcohol, and grind it with a mortar and pestle to obtain a uniformly mixed ceramic powder; (3) Pressing and firing: Pass the powder through a 150-mesh sieve, use a mold to press the dry powder into round discs at 16 MPa, and fire the discs at 900℃ for 3 hours; (4) Ball milling and drying: The fired ceramic blocks are ground in a grinding bowl, transferred to a planetary ball mill for further grinding, and 2 times the mass of alcohol is added. The mixture is ball milled at 300 speed for 8 hours to obtain a mixed slurry, which is then dried to obtain ceramic powder. (5) Granulation and molding: The powder is passed through a 150-mesh sieve, and then a 3% PVA solution is added to it. The mass of PVA added is 0.8% of the mass of the powder. After grinding, it is passed through a 150-mesh sieve to make the PVA evenly mixed in the ceramic powder. The powder particles are placed in a mold and pressed into shape under a pressure of 12MPa. Then, it is pressed further under isostatic pressure of 250MPa to form a ceramic green body. (6) Debinding and sintering: The ceramic green body is kept at 500℃ for 1 hour to remove the binder, then heated to 1150℃ for 2 hours and cooled to obtain sodium bismuth titanate ceramic material.

[0028] Performance testing: The material prepared in Comparative Example 1 was tested, and the XRD values ​​were obtained as follows: Figure 1 As shown, according to Figure 1 It can be seen that it has a complete perovskite structure with no second phase; Hysteresis loop test was performed on Comparative Example 1, and the hysteresis loop was obtained as follows: Figure 2 As shown, the coercive field E c It is 70 kV / cm; The material prepared in Example 1 was tested, and the XRD pattern was obtained as follows: Figure 3 As shown, there is no significant difference compared to Comparative Example 1; it exhibits a complete perovskite structure with no obvious second phase, and the hysteresis loop is as follows. Figure 4 As shown, the coercive field E c It is 70 kV / cm; The material prepared in Example 2 was tested, and the XRD pattern was obtained as follows: Figure 5 As shown, there is no significant difference compared to Comparative Example 1; it exhibits a complete perovskite structure with no obvious second phase, and the hysteresis loop is as follows. Figure 6As shown, the coercive field E increases to 76 kV / cm; The material prepared in Example 3 was tested, and the XRD pattern was obtained as follows: Figure 7 As shown, there is no significant difference compared to Comparative Example 1; it exhibits a complete perovskite structure with no obvious second phase, and the hysteresis loop is as follows. Figure 8 As shown, the coercive field E c Increased to 81 kV / cm; The material prepared in Example 4 was tested, and the XRD pattern was obtained as follows: Figure 9 As shown, there is no significant difference compared to Comparative Example 1, exhibiting a complete perovskite structure. A weak second-phase characteristic peak is observed and marked with ◆, indicating it is Na₂Ti₆O. 13 ; The hysteresis loop is obtained as follows Figure 10 As shown, the coercive field E c Reduced to 68kV / cm; The coercive field E of Comparative Example 1 and Examples 1, 2, 3, and 4 c Statistics such as Figure 15 As shown, Example 3 can effectively increase the coercive field, while Example 4 reduces the coercive field; The material prepared in Example 5 was tested, and the XRD pattern was obtained as follows: Figure 11 As shown, there is no significant difference compared to Comparative Example 1, and it shows a complete perovskite structure with no obvious second phase; The material prepared in Example 6 was tested, and the XRD pattern was obtained as follows: Figure 12 As shown, there is no significant difference compared to Comparative Example 1, and it shows a complete perovskite structure with no obvious second phase; The material prepared in Example 7 was tested, and the XRD pattern was obtained as follows: Figure 13 As shown, there is no significant difference compared to Comparative Example 1, and it shows a complete perovskite structure with no obvious second phase; The material prepared in Example 8 was tested, and the XRD pattern was obtained as follows: Figure 14 As shown, there is no significant difference compared to Comparative Example 1. It shows a complete perovskite structure. Weak second-phase characteristic peaks were observed and marked with ◆. The comparison is TiO2. The piezoelectric coefficient d33 of Comparative Example 1 and Examples 5, 6, 7, and 8 are statistically analyzed as follows: Figure 15 As shown, Example 7 can effectively improve the piezoelectric coefficient, while Example 8 reduces the piezoelectric coefficient.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-stoichiometric bismuth titanate sodium ceramic material at position A, characterized in that, The chemical formula of the sodium bismuth titanate ceramic material, which is a non-stoichiometric component at position A, is Na. 0.5-y Bi 0.5-x TiO3, wherein 0≤x≤0.4, 0≤y≤0.

4.

2. The sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 1, characterized in that, The x = 0.04 and y = 0.

3. The sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 1, characterized in that, The values ​​are x = 0 and y = 0.

03.

4. A method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A-site as described in claim 1, 2, or 3, characterized in that, Includes the following steps: Weighing and mixing: The raw materials are titanium dioxide, bismuth oxide, and sodium carbonate. The raw materials are dried, weighed by molar ratio, and then mixed with alcohol to obtain a mixed slurry. Drying: The slurry is dried to remove ethanol and ground to obtain a uniformly mixed raw material powder; Tableting and firing: Dry powder is pressed into shape using a mold and then fired in a high-temperature furnace; Ball milling and drying: Add alcohol to the fired ceramic blocks and pulverize them by ball milling to obtain a mixed slurry, then dry to obtain ceramic powder; Granulation and molding: Ceramic powder is sieved, PVA solution is added to it, it is ground, sieved again, pressed and shaped, and then statically pressed to form a ceramic green body; Debinding and sintering: The ceramic green body is debinded and sintered at high temperature, and after cooling, sodium bismuth titanate ceramic material with non-chemical composition at site A is obtained.

5. The method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 4, characterized in that, In the tableting and firing process, the pressing pressure is 8-12 MPa, the reaction temperature is 880-930℃, and the time is 3-3.5 h.

6. The method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 4, characterized in that, In the granulation and molding process, the pressure of grinding, sieving, and pressing is 15-18 MPa, and the pressure of static pressing is 235-265 MPa.

7. The method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 4, characterized in that, In the glue removal step, the heat preservation temperature is 490-510℃ and the time is 60-80min.

8. The method for preparing sodium bismuth titanate ceramic material with a non-stoichiometric composition at position A according to claim 4, characterized in that, In the sintering step, the high-temperature sintering temperature is 1140-1170℃ and the time is 2-2.5h.

9. The application of a sodium bismuth titanate ceramic material with a non-stoichiometric composition at the A site as described in claim 1, 2 or 3 in piezoelectric devices.

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