A bismuth-layered piezoelectric ceramic material, its preparation method and application

Abstract

The present invention provides a bismuth-layered piezoelectric ceramic material, a preparation method thereof, and an application thereof. The bismuth-layered piezoelectric ceramic material of the present invention has a chemical composition of Bi4Ti 3‑x (Mg 1 / 2 W 1 / 2 ) x O 12 , where 0.005 ≤ x ≤ 0.1. The bismuth-layered piezoelectric ceramic material of the present invention uses the method of B-site composite doping to replace the B-site titanium ions in Bi4Ti3O 12 . Tungsten element and magnesium element are used for B-site doping, and its chemical composition is Bi4Ti 3‑x (Mg 1 / 2 W 1 / 2 ) x O 12 (BTMW). By combining the effects of the "soft" additive W 6+ and the synergistic effect of the "hard" additive Mg 2+ , the lattice distortion degree of the oxygen octahedron in the bismuth-layered structure of Bi4Ti3O 12 can be adjusted at the same time, so as to achieve the effect of improving the piezoelectric performance while maintaining a high Curie temperature. The present invention also provides a preparation method and an application of the bismuth-layered piezoelectric ceramic material.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric materials, and particularly relates to a bismuth-layered piezoelectric ceramic material, a preparation method thereof, and an application thereof. Background Art

[0002] Piezoelectric ceramics are a type of functional materials with positive and inverse piezoelectric effects that can achieve the mutual conversion between mechanical energy and electrical energy. They are widely used in various fields such as daily life, industrial production, and military, and are the key to preparing oscillators, filters, sensors, and transducers, etc. With the expansion of the application fields of piezoelectric devices and the requirements of the development of high-tech, the application of high-temperature piezoelectric materials in fields such as petrochemical industry, aerospace, new energy, nuclear energy, automotive industry, and national defense has become increasingly important. Therefore, higher requirements are put forward for the stable service of piezoelectric materials in high-temperature environments.

[0003] Bismuth-layered structure high-temperature piezoelectric ceramics are a type of piezoelectric ceramics with characteristics such as high Curie temperature (500°C - 970°C), low dielectric loss, and low aging rate, and are the preferred piezoelectric materials for preparing high-temperature vibration sensors. However, these materials have problems such as high coercive field and difficult polarization. At the same time, the special layered structure of these materials limits their spontaneous polarization. Under the action of an electric field, the spontaneous polarization is difficult to be oriented, so the piezoelectric activity is relatively low.

[0004] The properties of piezoelectric ceramics often affect each other. The higher the piezoelectric coefficient, the lower the Curie temperature tends to be. Therefore, there is still a need to develop a new piezoelectric material that can improve the piezoelectric properties of the material while maintaining a relatively high Curie temperature. Summary of the Invention

[0005] The present invention aims to solve at least one of the above technical problems existing in the prior art. For this reason, the present invention provides a bismuth-layered piezoelectric ceramic material that can have good piezoelectric properties while maintaining a relatively high Curie temperature.

[0006] The present invention also provides a preparation method of the bismuth-layered piezoelectric ceramic material.

[0007] The present invention also provides a piezoelectric device including the bismuth-layered piezoelectric ceramic material.

[0008] The first aspect of the present invention provides a bismuth-layered piezoelectric ceramic material with a chemical composition of Bi4Ti 3-x (Mg 1 / 2W 1 / 2 ) x O 12 , where 0.005 ≤ x ≤ 0.1.

[0009] One technical solution in the technical solution of the present invention regarding the bismuth-layered piezoelectric ceramic material has at least the following beneficial effects:

[0010] The present invention provides a bismuth-layered piezoelectric ceramic material, which uses B-site composite doping to replace the B-site titanium ions in Bi4Ti3O 12 and performs B-site doping with tungsten element and magnesium element. Its chemical composition is Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 (BTMW). By combining the effects of "soft" additive W 6+ and the synergistic effect of "hard" additive Mg 2+ , it can simultaneously adjust the lattice distortion degree of the oxygen octahedron in the Bi4Ti3O 12 bismuth-layered structure, so as to achieve the effect of improving piezoelectric properties while maintaining a high Curie temperature.

[0011] For Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 ceramics, the composite doping ion combination is (Mg 1 / 2 W 1 / 2 ) x 4+ , and the existing forms of W and Mg elements are W 6+ and Mg 2+ respectively.

[0012] According to some embodiments of the present invention, 0.03 ≤ x ≤ 0.07.

[0013] According to some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material at 25 °C is 15 pC / N to 23 pC / N, and the Curie temperature T c is 680 °C to 686 °C.

[0014] According to some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material at 25 °C is 19 pC / N to 23 pC / N, and the Curie temperature T c is 683 °C to 686 °C.

[0015] According to some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material after annealing at 500 °C is 12 pC / N to 21 pC / N.

[0016] According to some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material after annealing at 500 °C is 17 pC / N to 21 pC / N.

[0017] The second aspect of the present invention provides a method for preparing a bismuth-layered piezoelectric ceramic material, comprising the following steps:

[0018] S1: Weigh a Bi source, a Ti source, a Mg source, and a W source according to the chemical composition and mix them to obtain a mixed powder;

[0019] S2: After pre-sintering a part of the mixed powder, a pre-sintered powder is obtained;

[0020] S3: Press a part of the mixed powder that has not been pre-sintered into a shape to obtain a green body;

[0021] S4: Use the pre-sintered powder to bury the green body and then sinter it to obtain the bismuth-layered piezoelectric ceramic material.

[0022] One technical solution in the method for preparing a bismuth-layered piezoelectric ceramic material of the present invention has at least the following beneficial effects:

[0023] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easily available, the production cost is low, and it is easy to industrialize production.

[0024] The preparation method of the present invention directly granulates and tablets the powder that has not been pre-sintered to reduce the volatilization of Bi during the pre-sintering process. Compared with the traditional solid-phase method, the present invention prepares BTMW ceramics by two-step sintering, which can improve the density of the ceramics.

[0025] The preparation method of the present invention, through (Mg 1 / 2 W 1 / 2 ) x 4+ doping to replace the B-site Ti ions in Bi4Ti3O 12 , and directly performing two-step sintering on the powder that has not been pre-sintered to prepare BTMW ceramics. By reducing the volatilization of Bi and using the two-step method to improve the density of the ceramics, while maintaining its relatively high Curie temperature, the piezoelectric properties and their stability of the Bi4Ti3O 12 -based ceramics are improved.

[0026] In the preparation method of the present invention, B-site composite doping replaces Bi4Ti3O 12 , doping is carried out with tungsten and magnesium elements, and the composite doping ion combination is (Mg 1 / 2 W 1 / 2 ) x 4+ , that is, the composition is Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12, by inducing lattice distortion, the distribution of oxygen vacancies can be regulated simultaneously, achieving the effect of improving piezoelectric properties.

[0027] In the preparation method of the present invention, considering that Bi is volatile at high temperatures, the Bi in the raw materials can be made excessive. Granulation and tableting are carried out using uncalcined powders, which can reduce the volatilization of Bi during the pre-calcination process, while the calcined powder is used for powder burial sintering, which can reduce the volatilization of Bi during the sintering process and prevent the ceramic sheets from sticking. Then, the ceramic can be prepared by a two-step sintering method, which can improve the density of the ceramic.

[0028] In the preparation method of the present invention, through (Mg 1 / 2 W 1 / 2 ) x 4+ composite substitution, and after two-step sintering of the wafers prepared using uncalcined powders, the piezoelectric properties of the ceramic are improved, and at the same time, the Curie temperature is not reduced compared to that of pure Bi4Ti3O 12 ceramics (T c = 675 °C).

[0029] According to some embodiments of the present invention, the Bi source is excessive by 1 wt% to 5 wt%.

[0030] According to some embodiments of the present invention, the Bi source is excessive by 3 wt%.

[0031] According to some embodiments of the present invention, the Bi source includes Bi2O3.

[0032] According to some embodiments of the present invention, the purity of Bi2O3 can be 99.7%.

[0033] According to some embodiments of the present invention, the Ti source includes TiO2.

[0034] According to some embodiments of the present invention, the purity of TiO2 can be 98%.

[0035] According to some embodiments of the present invention, the Mg source includes MgO.

[0036] According to some embodiments of the present invention, the purity of MgO can be 99.99%.

[0037] According to some embodiments of the present invention, the W source includes WO3.

[0038] According to some embodiments of the present invention, the purity of WO3 can be 99%.

[0039] According to some embodiments of the present invention, in step S1, according to the chemical composition, the Bi source, Ti source, Mg source, and W source are weighed and mixed to obtain a mixed powder. The method is as follows:

[0040] Pour the prepared raw materials into a polytetrafluoroethylene ball milling tank, and at the same time add zirconia grinding balls. The mass ratio of the raw materials to the grinding balls is 1:3. The grinding balls of large, medium and small sizes are in a mass ratio of 3:4:3. Then add an appropriate amount of absolute ethanol to basically cover the grinding balls. Finally, cover the lid and carry out wet ball milling. The ball milling conditions are 300 rpm to 400 rpm, and the ball milling time is 4 h to 12 h. Dry the ball milled slurry at a temperature of 50 °C to 80 °C for 1 h to 3 h, and then carry out sieving treatment (through a 60-mesh sieve).

[0041] According to some embodiments of the present invention, in step S2, after pre-burning a part of the mixed powder, a pre-burned powder is obtained. The method is as follows: divide the mixed powder into two parts, pour one part into an alumina crucible for pre-burning to obtain a pre-burned powder, and reserve the pre-burned powder for powder embedding sintering during the sintering process. On the one hand, it can reduce the volatilization of Bi during the sintering process; on the other hand, it can prevent the ceramic chips from sticking.

[0042] According to some embodiments of the present invention, the temperature of the pre-burning is 750 °C to 850 °C.

[0043] According to some embodiments of the present invention, the temperature of the pre-burning is 800 °C.

[0044] According to some embodiments of the present invention, the time of the pre-burning is 2 h to 4 h.

[0045] According to some embodiments of the present invention, the time of the pre-burning is 2 h.

[0046] According to some embodiments of the present invention, in step S3, a part of the unmixed powder is pressed into a green body. The method includes:

[0047] Directly granulate and tablet a part of the unmixed powder, that is, add a binder to the unburned powder. The binder can be an alcohol solution of polyvinyl butyral (PVB). Add a PVB solution of 4 wt% - 6 wt% of the used powder mass and grind it evenly until the alcohol volatilizes. Then sieve the granulated powder (for example, through a 60-mesh sieve). Weigh a certain amount (for example, 0.35 g) of the granulated powder each time, pour it into a circular tablet mold with a diameter of about 10 mm, and keep the pressure at 5 MPa to 10 MPa for 10 s to 60 s to form a round tablet by pressure. Then carry out cold isostatic pressing treatment, the pressure is about 200 MPa, and the pressure holding time is 5 min to 30 min.

[0048] After that, carry out debinding treatment on the green body to remove the binder added during granulation. It can be kept at 350 °C for 1 h, and then heated to 500 °C and kept at this temperature for 1 h.

[0049] According to some embodiments of the present invention, in step S4, the green body is sintered after being buried in powder with the pre-sintered powder. The sintering method is to heat up to 1150°C - 1180°C and hold for 2 min - 5 min, and then cool down to 1000°C - 1080°C and hold for 2 h - 5 h.

[0050] According to some embodiments of the present invention, the sintering method is to heat up to 1170°C and hold for 2 min, and then cool down to 1080°C and hold for 2 h.

[0051] According to some embodiments of the present invention, the heating rate is 5°C / min - 10°C / min.

[0052] According to some embodiments of the present invention, the heating rate is 5°C / min.

[0053] According to some embodiments of the present invention, the cooling rate is 5°C / min - 10°C / min.

[0054] According to some embodiments of the present invention, the cooling rate is 5°C / min.

[0055] According to some embodiments of the present invention, the method further includes, after step S4, polishing the sintered ceramic wafer.

[0056] According to some embodiments of the present invention, the method further includes, after step S4, printing electrode material on the surface of the bismuth layer-structured piezoelectric ceramic material to form electrodes.

[0057] According to some embodiments of the present invention, silver paste can be printed on both sides of the ceramic wafer, and then held at 720°C for 15 min for high-temperature curing. Then, the sample is polarized by oil bath heating. The polarization temperature can be 25°C - 100°C, the polarization electric field can be 5 kV / mm - 8 kV / mm, and the polarization time can be 20 min - 30 min. Finally, the piezoelectric properties and other properties of the polarized ceramic wafer can be tested.

[0058] The third aspect of the present invention provides a piezoelectric device including the bismuth layer-structured piezoelectric ceramic material described above.

[0059] One technical solution in the technical solution of the present invention regarding the piezoelectric device has at least the following beneficial effects:

[0060] The piezoelectric device of the present invention, since it includes the bismuth layer-structured piezoelectric ceramic material of the present invention, thus has all the technical effects of the bismuth layer-structured piezoelectric ceramic material. Specifically:

[0061] Due to the bismuth-layered piezoelectric ceramic material of the present invention, it can have good piezoelectric properties while maintaining a relatively high Curie temperature. Therefore, it is possible to improve the performance and sensitivity of piezoelectric devices such as sensors and actuators.

[0062] Operating at a high Curie temperature, piezoelectric ceramic materials are generally more stable. This means that the performance of the device will be more consistent, reducing the impact of temperature changes on performance, thereby improving the reliability of the device.

[0063] The mismatch effect refers to the change in material properties caused by temperature changes in piezoelectric devices, resulting in a decrease in device performance. A high Curie temperature can reduce the impact of the mismatch effect, enabling the device to maintain stable performance over a wider temperature range.

[0064] In addition, some specific applications require operation in high-temperature environments, such as engines and high-temperature heating devices. Using piezoelectric ceramic materials with a high Curie temperature allows piezoelectric devices to operate normally under these extreme conditions.

[0065] Some high-power piezoelectric devices may generate more heat due to energy losses. Using materials with a high Curie temperature can, to a certain extent, reduce the heat dissipation problem caused by energy losses. Brief Description of the Drawings

[0066] Figure 1 is a flowchart for the preparation of the bismuth-layered piezoelectric ceramic material.

[0067] Figure 2 is a comparison diagram of the conventional sintering method and the two-step sintering method of the present invention.

[0068] Figure 3 is the piezoelectric coefficient d of the bismuth-layered piezoelectric ceramic materials prepared in Examples 1 to 4 after annealing at 500 °C 33 measurement results. Detailed Description of the Invention

[0069] The following are specific examples of the present invention, and the technical solutions of the present invention are further described in combination with the examples, but the present invention is not limited to these examples.

[0070] In some embodiments of the present invention, the present invention provides a bismuth-layered piezoelectric ceramic material with a chemical composition of Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 , 0.005 ≤ x ≤ 0.1.

[0071] It can be understood that the present invention provides a bismuth-layered piezoelectric ceramic material, which uses B-site composite doping to replace Bi4Ti3O 12In the way of titanium ions at the B site, tungsten element and magnesium element are used for B-site doping, and its chemical composition is Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 (BTMW). Combining the action of the "soft" additive W 6+ and the synergistic effect of the "hard" additive Mg 2+ can adjust the lattice distortion degree of the oxygen octahedron in the Bi4Ti3O 12 bismuth-layered structure, so as to improve the piezoelectric properties while maintaining a high Curie temperature.

[0072] One feature of "soft" additives is that their valence is higher than that of the cations they replace. The so-called "softness" can be understood as making the properties of the material "soft", such as having a low coercive field strength, an increase in volume resistivity, etc. Replacing with low-valence cations will have the opposite effect to that of "soft" additives, that is, it will make the properties of the material "hard".

[0073] For Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 ceramics, the combined doping ion combination is (Mg 1 / 2 W 1 / 2 ) x 4+ , and the existing forms of W and Mg elements are W 6+ and Mg 2+ .

[0074] It should be noted that, structurally, the Curie temperature T c of bismuth-layered structure piezoelectric ceramics is related to the tolerance factor t,

[0075]

[0076] where r A 、r B 、r O represent the radii of the A-site cation, B-site cation and oxygen ion respectively. Generally speaking, the smaller t is, the higher T c . When W 6+ and Mg 2+ replace Ti 4+ , the t value becomes smaller, thus increasing T c .

[0077] When W 6+Substituted Ti 4+ When substituted, the oxygen vacancy concentration can be reduced. The process is as follows:

[0078]

[0079] Mg 2+ Substituted Ti 4+ After substitution, defect centers can be formed, which form strong binding dipoles with the simultaneously formed oxygen vacancies. Therefore, these oxygen vacancies are also regarded as external oxygen vacancies and do not participate in the conduction process, thus achieving the purpose of regulating the distribution of oxygen vacancies. The process is as follows:

[0080]

[0081] When (Mg 1 / 2 W 1 / 2 ) x 4+ Substitutes for B-site Ti as a whole 4+ It is an equivalent substitution, and generally no oxygen vacancies will be artificially introduced. Therefore, by substituting (Mg 1 / 2 W 1 / 2 ) x 4+ for the B-site titanium ions in Bi4Ti3O 12 , the lattice distortion degree and the oxygen vacancy distribution can be adjusted, so as to improve the piezoelectric properties of Bi4Ti3O 12 ceramics while maintaining its relatively high Curie temperature.

[0082] In some embodiments of the present invention, 0.03 ≤ x ≤ 0.07.

[0083] In some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material at 25°C is 15 pC / N to 23 pC / N, and the Curie temperature T c is 680°C to 686°C.

[0084] In some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material at 25°C is 19 pC / N to 23 pC / N, and the Curie temperature T c is 683°C to 686°C.

[0085] In some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material after annealing at 500°C is 12 pC / N to 21 pC / N.

[0086] In some embodiments of the present invention, the piezoelectric coefficient d 33 of the bismuth-layered piezoelectric ceramic material after annealing at 500°C is 17 pC / N to 21 pC / N.

[0087] It should be noted that from the perspective of complex doping and substitution of Ti by high- and low-valence cations at the B site 4+ For Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 , where W 6+ , Mg 2+ elements can also be replaced by a combination of high- and low-valence metal cations with a radius close to that of Ti 4+ , such as Ta 5+ , Sb 5+ and other high-valence cations and Mn 3+ , Ni 2+ and other low-valence cation combinations.

[0088] In some other embodiments of the present invention, the present invention provides a method for preparing a bismuth-layered piezoelectric ceramic material, and the preparation process is referred to Figure 1 as shown, including the following steps:

[0089] S1: Weigh the Bi source, Ti source, Mg source, and W source according to the chemical composition and mix them to obtain a mixed powder;

[0090] S2: After pre-firing a part of the mixed powder, obtain a pre-fired powder;

[0091] S3: Press and form a part of the mixed powder that has not been pre-fired to obtain a green body;

[0092] S4: Use the pre-fired powder to bury the green body and then sinter it to obtain a bismuth-layered piezoelectric ceramic material.

[0093] It can be understood that the preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easy to obtain, the production cost is low, and it is easy to industrialize.

[0094] The preparation method of the present invention directly granulates and tablets the powder without pre-firing to reduce the volatilization of Bi during the pre-firing process. Compared with the traditional solid-phase method, the present invention prepares BTMW ceramics by two-step sintering, which can improve the density of the ceramics.

[0095] The preparation method of the present invention, through (Mg 1 / 2 W 1 / 2 ) x 4+ doping to replace the B-site Ti ions in Bi4Ti3O 12 , and directly performs two-step sintering on the powder without pre-firing to prepare BTMW ceramics. By reducing the volatilization of Bi and using the two-step method to improve the density of the ceramics, while maintaining its high Curie temperature, it improves Bi4Ti3O12 Piezoelectric properties and stability of the base ceramics.

[0096] In the preparation method of the present invention, the B-site composite doping replaces Bi4Ti3O 12 , doped with tungsten element and magnesium element, and the composite doping ion combination is (Mg 1 / 2 W 1 / 2 ) x 4+ , that is, the composition is Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 . By inducing lattice distortion, the oxygen vacancy distribution can be regulated simultaneously, achieving the effect of improving piezoelectric properties.

[0097] In the preparation method of the present invention, considering that Bi is volatile at high temperatures, the Bi in the raw materials can be made excessive, and the powder that has not been pre-fired is used for granulation and pressing, which can reduce the volatilization of Bi during the pre-firing process; while the calcined powder is used for buried powder sintering, which can reduce the volatilization of Bi during the sintering process and prevent the ceramic sheets from sticking. Then, the ceramic is prepared by a two-step sintering method, which can improve the density of the ceramic. The sintering method of the two-step method of the present invention is different from the conventional sintering method as shown in Figure 2 .

[0098] In the preparation method of the present invention, through (Mg 1 / 2 W 1 / 2 ) x 4+ composite substitution, and after two-step sintering of the wafers prepared from the powder that has not been pre-fired, the piezoelectric properties of the ceramic are improved, and at the same time, the Curie temperature is not reduced compared with that of pure Bi4Ti3O 12 ceramics (T c = 675 °C).

[0099] In some embodiments of the present invention, the Bi source is excessive by 1 wt% - 5 wt%.

[0100] In some embodiments of the present invention, the Bi source is excessive by 3 wt%.

[0101] In some embodiments of the present invention, the Bi source includes Bi2O3.

[0102] In some embodiments of the present invention, the purity of Bi2O3 can be 99.7%.

[0103] In some embodiments of the present invention, the Ti source includes TiO2.

[0104] In some embodiments of the present invention, the purity of TiO2 can be 98%.

[0105] In some embodiments of the present invention, the Mg source includes MgO.

[0106] In some embodiments of the present invention, the purity of MgO can be 99.99%.

[0107] In some embodiments of the present invention, the W source includes WO3.

[0108] In some embodiments of the present invention, the purity of WO3 can be 99%.

[0109] In some embodiments of the present invention, in step S1, according to the chemical composition, the Bi source, Ti source, Mg source, and W source are weighed and mixed to obtain a mixed powder. The method is as follows:

[0110] The prepared raw materials are poured into a polytetrafluoroethylene ball milling tank, and at the same time, zirconia grinding balls are added. The mass ratio of the raw materials to the grinding balls is 1:3. The grinding balls of three sizes, large, medium, and small, are in a mass ratio of 3:4:3. Then, an appropriate amount of absolute ethanol is added to basically cover the grinding balls. Finally, the lid is covered for wet ball milling. The ball milling conditions are 300 rpm to 400 rpm, and the ball milling time is 4 h to 12 h. The ball-milled slurry is dried at a temperature of 50°C to 80°C for 1 h to 3 h, and then sieved (through a 60-mesh sieve).

[0111] In some embodiments of the present invention, in step S2, after pre-burning part of the mixed powder, a pre-burned powder is obtained. The method is as follows: The mixed powder is divided into two parts. One part is poured into an alumina crucible for pre-burning to obtain a pre-burned powder, which is reserved for buried powder sintering during the sintering process. On the one hand, it can reduce the volatilization of Bi during the sintering process; on the other hand, it can prevent the ceramic sheets from sticking.

[0112] In some embodiments of the present invention, the pre-burning temperature is 750°C to 850°C.

[0113] In some embodiments of the present invention, the pre-burning temperature is 800°C.

[0114] In some embodiments of the present invention, the pre-burning time is 2 h to 4 h.

[0115] In some embodiments of the present invention, the pre-burning time is 2 h.

[0116] In some embodiments of the present invention, in step S3, part of the mixed powder that has not been pre-burned is pressed into a green body. The method includes:

[0117] Directly granulate and tablet part of the unpresintered mixed powder, that is, add a binder to the powder without presintering. The binder can be an alcohol solution of polyvinyl butyral (PVB). Add 4wt%-6wt% of the PVB solution based on the mass of the powder and grind it evenly until the alcohol volatilizes. Then, screen the granulated powder (for example, it can pass through a 60-mesh sieve). Weigh a certain amount (for example, 0.35g) of the granulated powder each time, pour it into a circular tablet mold with a diameter of about 10mm, and keep the pressure at 5MPa - 10MPa for 10s - 60s to form a round tablet by pressure. Then, perform cold isostatic pressing treatment, with a pressure of about 200MPa and a holding time of 5min - 30min.

[0118] After that, perform debinding treatment on the green body to remove the binder added during granulation. It can be kept at 350°C for 1h and then heated to 500°C and kept at that temperature for 1h.

[0119] In some embodiments of the present invention, in step S4, use the presintered powder to bury the green body and then sinter it. The sintering method is to heat up to 1150°C - 1180°C and keep it for 2min - 5min, and then cool down to 1000°C - 1080°C and keep it for 2h - 5h.

[0120] It should be noted that in step S4, burying the powder means spreading the presintered powder on the round green body. This method can, on the one hand, reduce the volatilization of Bi during sintering; on the other hand, several green bodies can be stacked, and the green bodies are separated by the presintered powder to prevent the ceramic chips from sticking.

[0121] In some embodiments of the present invention, the sintering method is to heat up to 1170°C and keep it for 2min, and then cool down to 1080°C and keep it for 2h.

[0122] In some embodiments of the present invention, the heating rate is 5°C / min - 10°C / min.

[0123] In some embodiments of the present invention, the heating rate is 5°C / min.

[0124] In some embodiments of the present invention, the heating rate is 5°C / min - 10°C / min.

[0125] In some embodiments of the present invention, the cooling rate is 5°C / min.

[0126] In some embodiments of the present invention, the method further includes, after step S4, polishing the sintered ceramic round tablet.

[0127] In some embodiments of the present invention, the method further includes, after step S4, printing electrode material on the surface of the bismuth layer-structured piezoelectric ceramic material to form an electrode.

[0128] In some embodiments of the present invention, silver paste can be printed on both sides of a ceramic wafer, and then heat preservation is carried out at 720 °C for 15 min for high-temperature curing. After that, the sample is polarized by oil bath heating. The polarization temperature can be 25 °C to 100 °C, the polarization electric field can be 5 kV / mm to 8 kV / mm, and the polarization time can be 20 min to 30 min. Finally, the piezoelectric properties and other properties of the polarized ceramic wafer can be tested.

[0129] In some other embodiments of the present invention, the present invention provides a piezoelectric device, including the bismuth-layered piezoelectric ceramic material of the present invention.

[0130] It can be understood that the piezoelectric device of the present invention, due to including the bismuth-layered piezoelectric ceramic material of the present invention, thus has all the technical effects of the bismuth-layered piezoelectric ceramic material. Specifically:

[0131] Since the bismuth-layered piezoelectric ceramic material of the present invention can have good piezoelectric properties while maintaining a relatively high Curie temperature. Therefore, the performance and sensitivity of piezoelectric devices such as sensors and actuators can be improved.

[0132] Operating at a high Curie temperature, the piezoelectric ceramic material is usually more stable. This means that the performance of the device will be more consistent, reducing the influence of temperature changes on performance, thereby improving the reliability of the device.

[0133] The mismatch effect refers to the change in material properties caused by temperature changes in a piezoelectric device, resulting in a decrease in device performance. A high Curie temperature can reduce the influence of the mismatch effect and enable the device to maintain stable performance over a wider temperature range.

[0134] In addition, some specific applications need to work in a high-temperature environment, such as engines and high-temperature heating devices. Using a piezoelectric ceramic material with a high Curie temperature can enable the piezoelectric device to operate normally under these extreme conditions.

[0135] Some high-power piezoelectric devices may generate more heat due to energy loss. Using a material with a high Curie temperature can, to a certain extent, reduce the heat dissipation problem caused by energy loss.

[0136] Next, the technical solution of the present invention will be better understood by combining specific embodiments.

[0137] Example 1

[0138] In this example, a bismuth-layered piezoelectric ceramic material with a chemical composition of Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12, x is 0.01. The specific preparation process is as follows:

[0139] Weigh Bi2O3 (99.7%), TiO2 (98%), MgO (99.99%), and WO3 (99%) powders according to the stoichiometric ratio. Considering that Bi is volatile at high temperatures, Bi2O3 is in excess by 3 wt%;

[0140] Pour the prepared raw materials into a polytetrafluoroethylene ball milling tank, and at the same time add zirconia grinding balls. The ratio of the raw materials to the grinding balls is 1:3 by mass. The grinding balls of large, medium, and small sizes are in a mass ratio of 3:4:3. Then add an appropriate amount of anhydrous ethanol to basically cover the grinding balls, and finally cover the lid for wet ball milling. The ball milling conditions are 400 r / min and the ball milling time is 4 h. Dry the ball milled slurry, dry it at 50 - 80 °C for 2 h, and then perform sieving treatment (through a 60-mesh sieve);

[0141] Divide the powder into two parts. Pour one part into an alumina crucible for pre-sintering at a pre-sintering temperature of 800 °C for 2 h;

[0142] The powder that has not been pre-sintered is directly granulated and pressed. That is, a binder is added to the powder that has not been pre-sintered. The binder used in this example is an alcohol solution of polyvinyl butyral (PVB). Add 4 wt% PVB solution based on the mass of the powder and grind it evenly until the alcohol volatilizes. Then perform sieving treatment (through a 60-mesh sieve) on the granulated powder. Weigh 0.35 g of the granulated powder each time, pour it into a circular pressing die with a diameter of 10 mm, keep the pressure at 8 MPa for 30 s, and press it into a round piece. Then perform cold isostatic pressing treatment, with a pressure of 200 MPa and a holding time of 20 min;

[0143] Perform debinding treatment on the green body to remove the binder added during granulation, that is, keep it at 350 °C for 1 h and then raise the temperature to 500 °C for 1 h;

[0144] Use the pre-sintered powder to bury the sample after debinding, and then perform two-step sintering, that is, quickly raise the temperature to a higher temperature of 1170 °C and keep it for 2 min, and then quickly lower the temperature to 1080 °C and keep it for 2 h. The heating and cooling rate is 5 °C / min;

[0145] Polish the sintered ceramic round piece, then print silver paste on both sides, and then perform high-temperature curing at 720 °C for 15 min;

[0146] Polarize the sample by oil bath heating, with a polarization temperature of 80 °C, a polarization electric field of 6 kV / mm, and a polarization time of 20 min.

[0147] Example 2

[0148] In this example, a bismuth-layered piezoelectric ceramic material was prepared. The difference from Example 1 is that x is 0.03.

[0149] Example 3

[0150] In this example, a bismuth-layered piezoelectric ceramic material was prepared. The difference from Example 1 is that x is 0.05.

[0151] Example 4

[0152] In this example, a bismuth-layered piezoelectric ceramic material was prepared. The difference from Example 1 is that x is 0.07.

[0153] Performance Test 1

[0154] The performance parameters of the bismuth-layered piezoelectric ceramic materials prepared in Examples 1 to 4 were tested, as shown in Table 1 and Figure 3 as shown.

[0155] Table 1

[0156]

[0157] Comparative Example 1

[0158] In this comparative example, a bismuth-layered piezoelectric ceramic material with a chemical composition of Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 was prepared, where x is 0.01. The specific preparation process is as follows:

[0159] Weigh the powders of Bi2O3 (99.7%), TiO2 (98%), MgO (99.99%), and WO3 (99%) according to the stoichiometric ratio. Considering that Bi is volatile at high temperatures, Bi2O3 is taken in an excess of 3 wt%.

[0160] Pour the prepared raw materials into a polytetrafluoroethylene ball-milling tank, and at the same time add zirconia grinding balls. The mass ratio of the raw materials to the grinding balls is 1:3, and the mass ratio of the large, medium, and small grinding balls is 3:4:3. Then add an appropriate amount of anhydrous ethanol to basically cover the grinding balls, and finally cover the lid for wet ball milling. The ball milling conditions are 400 r / min and the ball milling time is 4 h. Dry the ball-milled slurry at a temperature of 50 - 80 °C for 2 h, and then perform sieving (through a 60-mesh sieve);

[0161] Pour all the powder into an alumina crucible for pre-sintering at a pre-sintering temperature of 800 °C for 2 h. After pre-sintering, divide the powder into two parts;

[0162] A part of the pre-sintered powder was directly granulated and pressed. That is, a binder was added to the pre-sintered powder. The binder used in this comparative example was an alcohol solution of polyvinyl butyral (PVB). A 4wt% PVB solution was added to the powder and ground thoroughly until the alcohol evaporated. Then, the granulated powder was sieved (through a 60-mesh sieve). Each time, 0.35 g of the granulated powder was weighed and poured into a circular pressing mold with a diameter of 10 mm, and held under pressure at 8 MPa for 30 s to form a round piece by pressing. Then, cold isostatic pressing was carried out at a pressure of 200 MPa for 20 min;

[0163] The green body was debinded to remove the binder added during granulation, that is, held at 350 °C for 1 h and then heated to 500 °C and held for 1 h;

[0164] Another part of the pre-sintered powder was used to bury the sample after debinding, and then two-step sintering was carried out, that is, quickly raised to a higher temperature of 1170 °C and held for 2 min, and then quickly lowered to 1080 °C and held for 2 h, with a heating and cooling rate of 5 °C / min;

[0165] The sintered ceramic round pieces were polished, then silver paste was printed on both sides, and then high-temperature curing was carried out at 720 °C for 15 min;

[0166] The samples were polarized by oil bath heating at a polarization temperature of 80 °C, a polarization electric field of 6 kV / mm, and a polarization time of 20 min.

[0167] Comparative Example 2

[0168] A bismuth-layered piezoelectric ceramic material was prepared in this comparative example. The difference from Comparative Example 1 was that x was 0.03.

[0169] Comparative Example 3

[0170] A bismuth-layered piezoelectric ceramic material was prepared in this comparative example. The difference from Comparative Example 1 was that x was 0.05.

[0171] Comparative Example 4

[0172] A bismuth-layered piezoelectric ceramic material was prepared in this comparative example. The difference from Comparative Example 1 was that x was 0.07.

[0173] Performance Test 2

[0174] The performance parameters of the bismuth-layered piezoelectric ceramic materials prepared in Comparative Examples 1 to 4 were tested, as shown in Table 2.

[0175] Table 2

[0176]

[0177] Compared with Table 1, it can be seen that compared with the BTMW ceramic samples in the embodiment that were directly sintered by the two-step method without pre-firing, the piezoelectric properties of the samples prepared in the comparative example are relatively poor, so there is no need to continue the piezoelectric performance stability test.

[0178] The bismuth layered piezoelectric ceramic material of the present invention adopts W 6+ and Mg 2+ Perform B-site composite doping to replace Bi4Ti3O 12 Ti4 in middle B position + If only W 6+ Although donor doping can improve the piezoelectric properties of BIT-based ceramics to a certain extent, the Curie temperature will decrease slightly. 2+ Replace Ti in BIT 4+ , which is acceptor doping, will theoretically reduce the resistivity of the ceramic and make it more difficult to polarize. 6+ and Mg 2+ Composite doping, combined with "soft" additives W 6+ Function and "hard" additive Mg 2+ The synergistic effect of Bi4Ti3O 12 The degree of lattice distortion of the oxygen octahedron in the bismuth layered structure enables it to achieve the effect of improving the piezoelectric performance while maintaining a high Curie temperature.

[0179] In some embodiments of the present invention, the present invention provides a piezoelectric device, which contains the bismuth layered piezoelectric ceramic material of the present invention.

[0180] It can be understood that the piezoelectric device of the present invention, because it includes the bismuth layered piezoelectric ceramic material of the present invention, has all the technical effects of the bismuth layered piezoelectric ceramic material. Specifically:

[0181] Since the bismuth layered piezoelectric ceramic material of the present invention can maintain a relatively high Curie temperature while having good piezoelectric properties, the performance and sensitivity of piezoelectric devices such as sensors, drivers and the like can be improved.

[0182] Operating at a high Curie temperature, piezoelectric ceramic materials are generally more stable. This means the performance of the device will be more consistent, reducing the impact of temperature changes on performance, thereby improving the reliability of the device.

[0183] The mismatch effect refers to the change in material properties caused by temperature changes in piezoelectric devices, which leads to a decrease in device performance. A high Curie temperature can reduce the impact of the mismatch effect and keep the device stable over a wider temperature range.

[0184] In addition, some specific applications need to work in high-temperature environments, such as engines, high-temperature heating devices, etc. Using piezoelectric ceramic materials with a high Curie temperature in these environments can enable piezoelectric devices to operate normally under these extreme conditions.

[0185] Some high-power piezoelectric devices may generate more heat due to energy loss. Using materials with a high Curie temperature can, to a certain extent, reduce the heat dissipation problems caused by energy loss.

[0186] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

Claims

1. A bismuth layer-structured piezoelectric ceramic material, characterized in that, The chemical composition is Bi4Ti 3-x (Mg 1 / 2 W 1 / 2 ) x O 12 ,0.005 ≤ x ≤ 0.1; The bismuth-layered piezoelectric ceramic material described above is prepared by the following steps: S1: According to the chemical composition, weigh the Bi source, Ti source, Mg source, and W source and mix them to obtain a mixed powder; S2: After pre-sintering part of the mixed powder, obtain a pre-sintered powder; S3: Press and form part of the mixed powder that has not been pre-sintered to obtain a green body; S4: Use the pre-sintered powder to bury the green body and then sinter it to obtain the bismuth-layered piezoelectric ceramic material.

2. The bismuth layer-structured piezoelectric ceramic material according to claim 1, wherein The piezoelectric coefficient of the bismuth layer-structured piezoelectric ceramic material at 25 °C d 33 is 15 pC / N to 23 pC / N, and the Curie temperature T c is 680 °C to 686 °C.

3. The bismuth layer-structured piezoelectric ceramic material according to claim 1, wherein The piezoelectric coefficient of the bismuth-layered piezoelectric ceramic material after annealing at 500 °C d 33 is 12 pC / N to 21 pC / N.

4. The bismuth layer-structured piezoelectric ceramic material according to claim 1, wherein The Bi source includes Bi2O3.

5. The bismuth-layered piezoelectric ceramic material according to claim 1, characterized in that, The Ti source includes TiO2.

6. The bismuth-layered piezoelectric ceramic material according to claim 1, wherein The Mg source includes MgO.

7. The bismuth layer-structured piezoelectric ceramic material according to claim 1, wherein, The W source includes WO3.

8. The bismuth-layered piezoelectric ceramic material according to claim 1, wherein The temperature of the pre-sintering is 750°C to 850°C.

9. The bismuth-layered piezoelectric ceramic material according to claim 1, wherein The time of the pre-sintering is 2 h to 4 h.

10. The bismuth layer-structured piezoelectric ceramic material according to claim 1, characterized in that, The sintering method is to raise the temperature to 1150°C to 1180°C and hold for 2 min to 5 min, and then lower the temperature to 1000°C to 1080°C and hold for 2 h to 5 h.

11. The bismuth-layered piezoelectric ceramic material according to claim 10, wherein, The heating rate is 5°C / min to 10°C / min, and the cooling rate is 5°C / min to 10°C / min.

12. The bismuth-layered piezoelectric ceramic material according to claim 1, characterized in that, When preparing the bismuth-layered piezoelectric ceramic material described above, it further includes printing an electrode material on the surface of the bismuth-layered piezoelectric ceramic material after step S4 to form an electrode.

13. A piezoelectric device, characterized in that, It includes the bismuth-layered piezoelectric ceramic material according to any one of claims 1 to 12.

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