Piezoelectric ceramic material, preparation method thereof and energy collection device

Abstract

The invention provides a piezoelectric ceramic material, a preparation method thereof and an energy collection device, the chemical composition of the piezoelectric ceramic material is Na < 0.5 > Bi < 4.5 > Ti < 4-z > Mn < x > Nb < y > O < 15 >, x is greater than 0 and less than or equal to 0.08, y is greater than or equal to 0 and less than or equal to 0.12, and x + y = z. According to the piezoelectric ceramic material provided by the invention, a proper amount of manganese element and niobium element are introduced into the bismuth layered ceramic Na0. 5Bi4. 5Ti4O15, and the proportion of the manganese element and the niobium element is controlled, so that the piezoelectric ceramic material is more easily polarized, the piezoelectric property of the piezoelectric ceramic material is remarkably improved, and the stability of the piezoelectric property under a high-temperature condition is improved. Meanwhile, the piezoelectric ceramic material provided by the invention is a lead-free material and conforms to the concept of environmental protection.

Description

Technical Field

[0001] The present application belongs to the technical field of piezoelectric ceramic materials, and specifically relates to piezoelectric ceramic materials and preparation methods thereof, and energy collection devices. Background Art

[0002] When microsensor devices are used in high-temperature environments such as aerospace, nuclear reactors, and geothermal energy, it is usually difficult to replace batteries, so the microsensor devices need to have the ability to be self-powered. Piezoelectric materials can convert vibration energy in the environment into electrical energy to achieve self-powered microsensors. Commonly used piezoelectric materials Pb(Zr,Ti)O 3 The Curie temperature is low and is not suitable for high temperature environments. Currently, bismuth layered ceramics are used to replace Pb(Zr,Ti)O 3 Piezoelectric materials, although bismuth layered ceramics have a high Curie temperature and have potential in high-temperature applications, their piezoelectric properties are poor. Summary of the invention

[0003] In view of this, the first aspect of the present application provides a piezoelectric ceramic material, the chemical composition of the piezoelectric ceramic material is Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 , where 0<x≤0.08, 0≤y≤0.12, x+y=z.

[0004] The piezoelectric ceramic material provided in the first aspect of the present application is based on the classic bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 (NBT) is used as the matrix material. Aiming at the shortcomings of NBT-based ceramics, appropriate amounts of manganese and niobium elements are introduced to jointly adjust the performance of piezoelectric ceramic materials.

[0005] First, the introduction of appropriate amounts of manganese and niobium elements causes the electric domain to shift from macrodomain to nanodomain, promotes the response of the external electric field, and makes it difficult for the space charge of the ferroelectric domain to gather on the domain wall during the rapid flipping process, reducing the fixed effect of the domain wall, and thus making the piezoelectric ceramic material easier to be polarized, thereby improving the piezoelectric coefficient of the piezoelectric ceramic material, that is, the piezoelectric performance. In addition, the introduction of appropriate amounts of manganese and niobium elements also improves the stability of the piezoelectric performance, that is, the piezoelectric coefficient of the piezoelectric ceramic material will not decay significantly from room temperature to high temperature.

[0006] Secondly, the introduction of appropriate amounts of manganese and niobium makes the grain size of the ceramic uniform and refined, improves the density of the ceramic, reduces the defects inside the ceramic, and thus reduces the dielectric loss of the piezoelectric ceramic material. At the same time, the increase in density allows the piezoelectric ceramic material to be polarized under a higher polarization electric field, so that the piezoelectric ceramic material can exert better piezoelectric properties.

[0007] In summary, the piezoelectric ceramic material provided by the present application is formed by using the bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 By introducing an appropriate amount of manganese and niobium and controlling the ratio of the two, the piezoelectric ceramic material is more easily polarized, thereby significantly improving the piezoelectric performance of the piezoelectric ceramic material and improving the stability of the piezoelectric performance under high temperature conditions. At the same time, the piezoelectric ceramic material provided in this application is a lead-free material, which conforms to the concept of green environmental protection.

[0008] The piezoelectric ceramic material is a bismuth layered structure and is a layered perovskite structure ceramic material with m=4.

[0009] Wherein, when x=0.06, y=0.04, the piezoelectric coefficient d of the piezoelectric ceramic material at 300°C is 33 is 38-42pC / N, and the Curie temperature T c It is 665-675℃.

[0010] When 0≤y≤0.12, the dielectric loss tanδ of the piezoelectric ceramic material first decreases and then increases with the introduction of niobium element.

[0011] A second aspect of the present application provides a method for preparing a piezoelectric ceramic material, the preparation method comprising:

[0012] The sodium source, bismuth source, titanium source, manganese source, and niobium source are prepared according to the chemical formula Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 The raw material is weighed in a stoichiometric ratio, wherein 0<x≤0.08, 0≤y≤0.12, x+y=z;

[0013] The raw materials are subjected to a first ball milling and a first sintering in sequence to obtain a mixed material;

[0014] The mixed material is subjected to a second ball milling, tablet pressing, binder removal, and a second sintering in sequence to obtain a ceramic sheet;

[0015] The ceramic sheet is subjected to a polarization process to obtain a piezoelectric ceramic material.

[0016] The preparation method provided in the second aspect of the present application is to prepare Na by solid phase sintering method. 0.5 Bi 4.5 Ti 4- z Mn x Nb y O 15 Piezoelectric ceramic materials have obtained lead-free ceramics with high-voltage electrical properties with high-temperature stability. The method is simple, easy to prepare, and convenient for large-scale production. It has significant economic and social value and provides new lead-free materials for self-powered energy collection of microsensor devices, which is in line with the concept of green environmental protection.

[0017] During the first ball milling, the ratio of the raw material to the first ball milling solvent is 1:(0.8-1.2), and the direction of ball milling is changed every 20-40 minutes; during the second ball milling, the ratio of the mixture to the second ball milling solvent is 1:(0.6-0.8), and the direction of ball milling is changed every 20-40 minutes.

[0018] Wherein, during the debinding, the mixed material after tableting is placed in a crucible covered with a landfill material and heated at a temperature of 550-650° C. for a heat preservation time of 1.5-2 hours.

[0019] During the second sintering, the landfill covers the debinding mixture, and the landfill and the debinding mixture are heated for the first time at a temperature of 750-850°C and a holding time of 2-4h, and then heated for the second time at a temperature of 980-1080°C and a holding time of 2-4h.

[0020] Among them, during the polarization process, a conductive material is applied to the surface of the ceramic sheet, and heated and fired to convert the conductive material into an electrode. The firing temperature is 550-650°C, and the insulation time is 5-15 minutes. The ceramic sheet after firing the electrode is polarized to obtain a piezoelectric ceramic material.

[0021] A third aspect of the present application provides an energy collection device, the energy collection device comprising the piezoelectric ceramic material provided in the first aspect of the present application, and the energy collection device satisfies at least one of the following conditions:

[0022] The peak open circuit voltage of the energy harvesting device at 300°C is 2.0-2.5V;

[0023] The energy density of the energy harvesting device at 300°C is 0.0025-0.0030 μW / mm 3 .

[0024] The energy collection device provided in the third aspect of the present application uses the piezoelectric ceramic material provided in the first aspect of the present application, so that the energy collection device still has good power supply performance at a high temperature of 300°C. It is convenient to apply the energy collection device to a complex environment with high temperature, thereby realizing the self-power supply of micro sensors in a green power system. It has significant social significance and economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the implementation modes of the present application, the drawings required for use in the implementation modes of the present application will be described below.

[0026] Figure 1 1 is an XRD spectrum of the piezoelectric ceramic material when y=0, and x=0, 0.02, 0.04, 0.06, and 0.08 in one embodiment of the present application.

[0027] Figure 2 This is the XRD spectrum of the piezoelectric ceramic material when x=0.06, and y=0, 0.04, 0.08, and 0.12 in another embodiment of the present application.

[0028] Figure 3 This is a graph and a partial enlarged graph showing the relationship between the dielectric loss of the piezoelectric ceramic material and the temperature when x=0.06 and y=0, 0.04, 0.08, and 0.12 in one embodiment of the present application.

[0029] Figure 4 1 is a process flow chart of a method for preparing a piezoelectric ceramic material in one embodiment of the present application.

[0030] Figure 5 This is a process flow chart included in S200 in one embodiment of the present application.

[0031] Figure 6 This is a process flow chart included in S300 in one embodiment of the present application.

[0032] Figure 7 This is a process flow chart of S300 in another embodiment of the present application.

[0033] Figure 8 This is a process flow chart included in S300 in another embodiment of the present application.

[0034] Fig. 9 This is a process flow chart included in S400 in one embodiment of the present application.

[0035] Fig.10 Schematic diagram of an energy harvesting device in one embodiment of the present application.

[0036] Fig.111 is a scanning electron microscope image of a piezoelectric ceramic material when y=0, and x=0, 0.02, 0.04, 0.06, and 0.08 in one embodiment of the present application.

[0037] Fig.12 This is a graph showing the relationship between the dielectric constant of a piezoelectric ceramic material and temperature when y=0, and x=0, 0.02, 0.04, 0.06, and 0.08 in one embodiment of the present application, and a partially enlarged graph.

[0038] Fig.13 It is a graph showing the relationship between the dielectric loss of the piezoelectric ceramic material and the temperature when y=0 and x=0, 0.02, 0.04, 0.06, and 0.08 in one embodiment of the present application and a partial enlarged graph.

[0039] Fig.14 2 is a diagram of the piezoelectric coefficient of the piezoelectric ceramic material at room temperature when y=0, and x=0, 0.02, 0.04, 0.06, and 0.08 in one embodiment of the present application.

[0040] Fig.15 This is a scanning electron microscope image of a piezoelectric ceramic material when x=0.06, and y=0, 0.04, 0.08, and 0.12 in another embodiment of the present application.

[0041] Fig.16 This is a diagram of the actual density and relative density of the piezoelectric ceramic material when x=0.06, and y=0, 0.04, 0.08, and 0.12 in another embodiment of the present application.

[0042] Fig.17 This is a graph showing the relationship between the dielectric constant of the piezoelectric ceramic material and the temperature when x=0.06 and y=0, 0.04, 0.08, and 0.12 in another embodiment of the present application and a partial enlarged graph.

[0043] Fig.18 This is a piezoelectric coefficient diagram of the piezoelectric ceramic material at room temperature when x=0.06, and y=0, 0.04, 0.08, and 0.12 in another embodiment of the present application.

[0044] Fig.19 Graph showing the piezoelectric coefficient of a piezoelectric ceramic material under different polarization temperature conditions when x=0.06 and y=0, 0.04, 0.08, and 0.12 in one embodiment of the present application.

[0045] Fig. 20 1 is a temperature-dependent piezoelectric coefficient curve of a piezoelectric ceramic material when x=0.06 and y=0, 0.04, 0.08, and 0.12 in one embodiment of the present application. DETAILED DESCRIPTION

[0046] The following are preferred implementations of the present application. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application, and these improvements and modifications are also considered to be within the scope of protection of the present application.

[0047] In the description of the present invention, it should be understood that the weight of the relevant components mentioned in the embodiments of the present invention can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components in the embodiments of the present invention is proportionally enlarged or reduced, it is within the scope disclosed by the present invention. Specifically, the weight described in the embodiments of the present invention can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0048] In addition, unless the context clearly uses otherwise, the expression of the singular form of a word should be understood to include the plural form of the word. The term "includes" or "having" is intended to specify the existence of a feature, quantity, step, operation, element, part or combination thereof, but is not used to exclude the existence or possible addition of one or more other features, quantities, steps, operations, elements, parts or combinations thereof.

[0049] Before introducing the technical solution of the present application, the technical problems in the related technology are introduced in detail.

[0050] Microsensor devices have the advantages of small size and low power consumption, and are widely used in measuring temperature, pressure, torque, acceleration, etc. Traditional chemical batteries are not suitable for microsensors due to their large size, limited life, frequent replacement, and environmentally unfriendly materials. Especially in some special fields, such as aerospace, nuclear reactors, geothermal energy and other high-temperature environments, battery replacement is risky and even costs a huge price. Therefore, it is of great practical significance to realize the self-power supply of high-temperature microsensor devices. The technology of collecting and utilizing energy in the environment around microsensor devices, such as renewable energy such as solar energy, wind energy, and thermal energy, has become a hot topic for many scholars. Compared with energy such as solar energy, wind energy, and thermal energy, the collection of vibration energy in the environment has the advantages of low cost, easy preparation, and stable acquisition channels. This technology is also more suitable for microsensor devices.

[0051] Piezoelectric materials can convert vibration energy in the environment into electrical energy, thereby powering microsensors. Currently, the most widely used piezoelectric material is Pb(Zr,Ti)O 3(PZT) system materials, but on the one hand, the Curie temperature of this system material is generally around 300°C, while the actual application temperature of piezoelectric materials is generally 2 / 3 of the Curie temperature. Therefore, the actual application temperature of PZT system materials is below 200°C, which is difficult to apply in high temperature environments. On the other hand, due to the harm of lead-based materials to the environment, all parties have begun to restrict the application of lead-based materials. Therefore, in a social environment where environmental protection is increasingly valued, the research and development and application of environmentally friendly high-temperature lead-free piezoelectric ceramic materials are issues that need to be urgently addressed in the field of piezoelectric ceramic materials. The piezoelectric materials currently used in high-temperature environments are mainly piezoelectric single crystal materials with very limited piezoelectric properties, and the materials have problems such as complex production processes and high costs.

[0052] Bismuth layered ceramics have great potential in high-temperature applications due to their high Curie temperature, high resistivity, good fatigue resistance, obvious anisotropy, and high electromechanical coupling coefficient. However, the ultra-long c-axis of the perovskite layer in the bismuth layered structure hinders the flipping of the electric dipole, resulting in a high coercive field strength that makes it impossible for the ceramic to be fully polarized, making it difficult to improve the piezoelectric coefficient representing its piezoelectric properties, limiting the development of bismuth layered ceramics in practical applications.

[0053] In view of this, in order to solve the above problems, the present application provides a piezoelectric ceramic material. The chemical composition of the piezoelectric ceramic material provided in this embodiment is Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 , where 0<x≤0.08, 0≤y≤0.12, x+y=z.

[0054] The piezoelectric ceramic material provided in this embodiment is mainly used to convert vibration energy in the environment into electrical energy, and then transmit the electrical energy to electrical equipment or energy storage equipment.

[0055] In this embodiment, the piezoelectric ceramic mainly includes sodium (Na), bismuth (Bi), titanium (Ti), manganese (Mn), niobium (Nb), and oxygen (O), and the ratio of each element is about Na:Bi:Ti:Mn:Nb:O=0.5:4.5:4-z:x:y:15, that is, the chemical formula of the piezoelectric ceramic is Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15. Wherein 0<x≤0.08, 0≤y≤0.12, x+y=z, that is, the addition ratio of manganese element is greater than 0 and not greater than 0.08, the addition ratio of niobium element is not less than 0 and not greater than 0.12, and the sum of the addition ratios of manganese element and niobium element is equal to the reduction ratio of titanium element.

[0056] In this embodiment, the classic bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 (NBT) is used as the matrix material. Aiming at the shortcomings of NBT-based ceramics, appropriate amounts of manganese and niobium elements are introduced to jointly adjust the performance of piezoelectric ceramic materials.

[0057] First, the introduction of appropriate amounts of manganese and niobium elements causes the electric domain to shift from macrodomain to nanodomain, promotes the response of the external electric field, and makes it difficult for the space charge of the ferroelectric domain to gather on the domain wall during the rapid flipping process, reducing the fixed effect of the domain wall, and thus making the piezoelectric ceramic material easier to be polarized, thereby improving the piezoelectric coefficient of the piezoelectric ceramic material, that is, the piezoelectric performance. In addition, the introduction of appropriate amounts of manganese and niobium elements also improves the stability of the piezoelectric performance, that is, the piezoelectric coefficient of the piezoelectric ceramic material will not decay significantly from room temperature to high temperature.

[0058] Secondly, the introduction of appropriate amounts of manganese and niobium makes the grain size of the ceramic uniform and refined, improves the density of the ceramic, reduces the defects inside the ceramic, and thus reduces the dielectric loss of the piezoelectric ceramic material. At the same time, the increase in density allows the piezoelectric ceramic material to be polarized under a higher polarization electric field, so that the piezoelectric ceramic material can exert better piezoelectric properties.

[0059] When 0<x≤0.08, the proportion of manganese is appropriate, which can increase the piezoelectric properties of the piezoelectric ceramic material. When x>0.08, due to excessive addition of manganese, the basic structure of the piezoelectric ceramic material may change, making the piezoelectric performance of the piezoelectric ceramic material not significantly improved, or even decreased. Specifically, the value of x, that is, the proportion of manganese, can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08.

[0060] When 0≤y≤0.12, the proportion of niobium is appropriate, which can increase the piezoelectric properties of the piezoelectric ceramic material. When y>0.12, due to excessive addition of niobium, the basic structure of the piezoelectric ceramic material may change, making the piezoelectric performance of the piezoelectric ceramic material not significantly improved, or even decreased. Specifically, the value of y, that is, the proportion of niobium, can be 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12. When y=0, it means that only manganese is introduced into the piezoelectric ceramic material without niobium.

[0061] In summary, this embodiment is achieved by using bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 By introducing an appropriate amount of manganese and niobium and controlling the ratio of the two, the piezoelectric ceramic material is more easily polarized, thereby significantly improving the piezoelectric performance of the piezoelectric ceramic material and improving the stability of the piezoelectric performance under high temperature conditions. At the same time, the piezoelectric ceramic material provided in this embodiment is a lead-free material, which conforms to the concept of green environmental protection.

[0062] Please refer to Figure 1-Figure 2 In this embodiment, the piezoelectric ceramic material is a bismuth layered structure, and is a layered perovskite structure ceramic material with m=4.

[0063] As can be seen from the above, the piezoelectric ceramic of this embodiment is a bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 On the basis of this, the present embodiment also conducts phase structure test, such as Figure 1-Figure 2 shown. Figure 1 for Na 0.5 Bi 4.5 Ti 4-x Mn x O 15 (x=0, 0.02, 0.04, 0.06, 0.08) XRD diffraction patterns of ceramic samples with 2θ diffraction angles in the range of 20°-70° and 30°-35°. Figure 1 It can be seen that the introduction of manganese element did not produce other impurity phases. All ceramic samples have a single m=4 orthorhombic bismuth layered structure, and the crystal plane index (119) of the strongest diffraction peak is consistent with the strongest peak of bismuth layered structure ceramics (112m+1).

[0064] Figure 2 for Na 0.5 Bi 4.5 Ti 3.94-y Mn 0.06 Nb y O 15 (y=0, 0.04, 0.08, 0.12) XRD diffraction patterns of ceramic samples with 2θ diffraction angles in the range of 20~70° and 30~35°. Figure 2 It can be seen that the introduction of niobium element does not produce other impurity phases. All ceramic samples have a single orthorhombic bismuth layered structure with m=4. The crystal plane index of the strongest diffraction peak (1 1 9) is consistent with the strongest peak of bismuth layered structure ceramics (1 1 2m+1).

[0065] From the above results, it can be seen that the introduction of manganese and niobium elements in this embodiment does not destroy the Na 0.5 Bi 4.5 Ti 4 O 15 The bismuth layered structure of the matrix, after the introduction of manganese and niobium elements, the piezoelectric ceramic material is still a stable bismuth layered structure, and the crystal plane index of the strongest diffraction peak is (1 1 9), which is consistent with the strongest peak of the bismuth layered structure ceramic (1 1 2m+1)m=4, that is, the piezoelectric ceramic material is a layered perovskite structure ceramic material with m=4. That is to say, after adding manganese and niobium elements, the material still maintains the excellent properties of the bismuth layered structure, with a high Curie temperature and good piezoelectric performance.

[0066] In this embodiment, when x=0.06 and y=0.04, the piezoelectric coefficient d of the piezoelectric ceramic material at 300°C is 33 is 38-42pC / N, and the Curie temperature T c The piezoelectric coefficient is a reflection of the piezoelectric properties of the material. The higher the piezoelectric coefficient, the better the piezoelectric properties of the material. The Curie temperature is the critical point for the transformation of ferromagnetic materials into paramagnetic materials. When the temperature exceeds the Curie temperature, the performance of the material will drop significantly. Therefore, the operating temperature of piezoelectric ceramic materials generally does not exceed 2 / 3 of the Curie temperature.

[0067] In this embodiment, bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 Based on the above, when the ratio of manganese is 0.06 and the ratio of niobium is 0.04, the chemical composition is Na 0.5 Bi 4.5 Ti 3.9 Mn 0.06 Nb 0.04 O 15 The piezoelectric ceramic material has a good piezoelectric coefficient of 38-42C / N at a high temperature of 300°C, and the Curie temperature of the piezoelectric ceramic material with this chemical composition is relatively high at 665-675°C.

[0068] In this embodiment, the ratio of manganese introduced into the piezoelectric ceramic material is 0.06, and the ratio of niobium introduced into the piezoelectric ceramic material is 0.04, that is, the chemical composition of the piezoelectric ceramic material is Na 0.5 Bi 4.5 Ti 3.9 Mn 0.06 Nb 0.04 O 15, so that the piezoelectric ceramic material still has a good piezoelectric coefficient of 38-42pC / N under high temperature conditions of 300℃, and the piezoelectric ceramic material also has a high Curie temperature of 665-675℃. That is, the piezoelectric ceramics of this embodiment can still be used under high temperature conditions of 300℃, and have good piezoelectric properties, which provides support for high-temperature application scenarios of piezoelectric ceramic materials. And compared with the pure NBT-based ceramic material without adding manganese and niobium elements at 300℃, the d 33 =10pC / N is about 300% higher.

[0069] Specifically, the piezoelectric coefficient d of the piezoelectric ceramic material in this embodiment at 300°C is 33 It can be 38pC / N, 39pC / N, 40pC / N, 41pC / N, 42pC / N. The Curie temperature T of piezoelectric ceramic material c It can be 665°C, 668°C, 670°C, 671.3°C, 673°C, and 675°C.

[0070] In this embodiment, when 0≤y≤0.12, the dielectric loss tanδ of the piezoelectric ceramic material first decreases and then increases with the introduction of niobium. Piezoelectric ceramic materials consume energy during conduction and polarization, and inevitably convert part of the electrical energy into heat energy. In this process, the electrical energy consumed per unit time is called dielectric loss. For most dielectric materials, low dielectric loss can effectively ensure that the piezoelectric ceramic material performs optimally.

[0071] In this embodiment, when 0≤y≤0.12, that is, when the introduction ratio of niobium is 0-0.12, the dielectric loss of the piezoelectric ceramic material decreases first and then increases with the introduction of niobium element. Figure 3 As shown, Na 0.5 Bi 4.5 Ti 3.94- y Mn 0.06 Nb y O 15 (y=0, 0.04, 0.08, 0.12), as y increases, the curve of tanδ shows a trend of first decreasing and then increasing, and the dielectric loss reaches a minimum value when y=0.04. That is to say, when 0≤y<0.04, as y increases, the dielectric loss of the piezoelectric ceramic material gradually decreases, and when 0.04<y≤0.12, as y increases, the dielectric loss of the piezoelectric ceramic material gradually increases.

[0072] In this embodiment, by introducing an appropriate amount of niobium, the piezoelectric coefficient of the piezoelectric ceramic material is increased, and the dielectric loss of the piezoelectric ceramic material is reduced. When the niobium doping ratio is 0.04, the dielectric loss of the piezoelectric ceramic material is the smallest. By reducing the dielectric loss, the piezoelectric ceramic material can exert better performance.

[0073] Please refer to Figure 4 This embodiment provides a method for preparing a piezoelectric ceramic material, and the method includes S100, S200, S300, and S400. S100, S200, S300, and S400 are described in detail as follows.

[0074] S100, a sodium source, a bismuth source, a titanium source, a manganese source, and a niobium source are mixed according to the chemical formula Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 The raw materials are weighed in a stoichiometric ratio, wherein 0<x≤0.08, 0≤y≤0.12, and x+y=z. In this embodiment, the raw materials sodium source, bismuth source, titanium source, manganese source, and niobium source can be prepared according to the chemical equation Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 Weigh accurately.

[0075] In this embodiment, the sodium source can be Na 2 CO 3 、Na 2 SO 4 The bismuth source may be Bi 2 O 3 、NaBiO 3 The titanium source may be TiO 2 、Ti(SO 4 ) 2 The manganese source may be MnO 2 、Mn(SO 4 ) 2 One or more of the manganese-containing compounds. The niobium source may be Nb 2 O 5 、LiNbO 3 Oxygen can be provided by oxygen in other raw material compounds or by oxygen in the air. 2 CO 3 、Bi2 O 3 、TiO 2 、MnO 2 , Nb 2 O 5 The raw materials are schematically illustrated.

[0076] S200, the raw materials are subjected to the first ball milling and the first sintering in sequence to obtain a mixed material. Ball milling is an important grinding method. Ball milling can crush the materials into uniform powder and mix them evenly. The raw materials are ground into powder and mixed evenly by the first ball milling. Sintering is to transform the powdered materials into a dense body, which is mainly used in the production of ceramics, powder metallurgy, refractory materials, ultra-high temperature materials, etc. The first sintering is used to initially form Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 Piezoelectric ceramic crystal phase.

[0077] S300, the mixture is subjected to a second ball milling, tableting, binder removal, and a second sintering in sequence to obtain a ceramic sheet. The main purpose of the second ball milling is to break up the mixture after the first sintering and grind it into powder. Tableting refers to pressing the mixture mixed with a binder into the shape of a ceramic body. Binding removal refers to the removal of the binder inside the ceramic body by heating. The main purpose of the second sintering is to sinter the ceramic body into a ceramic sheet.

[0078] S400, performing a polarization process on the ceramic sheet to obtain a piezoelectric ceramic material.

[0079] Polarization refers to the application of a strong DC electric field to piezoelectric ceramic materials so that the electric domains in the ceramics are oriented along the direction of the electric field. It is also called artificial polarization treatment or single domain treatment. Piezoelectric ceramic materials must be polarized before they have piezoelectric properties.

[0080] In this embodiment, Na is prepared by solid phase sintering method. 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 Piezoelectric ceramic materials have obtained lead-free ceramics with high-voltage electrical properties with high-temperature stability. The method is simple, easy to prepare, and convenient for large-scale production. It has significant economic and social value and provides new lead-free materials for self-powered energy collection of microsensor devices, which is in line with the concept of green environmental protection.

[0081] From the above content, we can know the general process of the preparation method of piezoelectric ceramic materials. Next, the detailed steps in the process will be introduced step by step in detail.

[0082] From the above content, it can be seen that the raw materials need to be first ball milled to crush and mix evenly. Please refer to Figure 5 In this embodiment, S200 "performing a first ball milling and a first sintering on the raw material in sequence to obtain a mixed material" includes S210. The detailed description of S210 is as follows: during the first ball milling, the ratio of the raw material to the first ball milling solvent is 1:(0.8-1.2), and the direction of ball milling is changed every 20-40 minutes.

[0083] During the first ball milling, the ratio of raw materials to the first ball milling solvent can be 1: (0.8-1.2), and the direction of the ball milling can be changed every 20-40 minutes. Through the above operation, the effect of the first ball milling is better, the particle size of the powder after ball milling is smaller, the mixing is more uniform, and the contact between the materials is more sufficient, so that the effect of the subsequent first sintering is better.

[0084] Specifically, in this embodiment, all weighed raw materials can be placed in a clean ball milling jar, ball milling media and ball milling solvent are added, and the ratio of raw materials to the first ball milling solvent is 1: (0.8-1.2), the ball milling speed is adjusted to 200-300r / min, the ball milling time is 15-17h for ball milling, and the ball milling direction is changed every 20-40min during the first ball milling to grind the raw materials into powder and mix the raw materials evenly. Optionally, the ball milling jar can be a 500ml polyurethane ball milling jar, the ball milling media can be zirconium balls, and the ball milling solvent can be anhydrous ethanol.

[0085] Specifically, the ratio of the raw material to the ball milling solvent during the first ball milling can be 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2. The time for changing the direction during the first ball milling can be changed every 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0086] After the first ball milling, the mixed raw materials are dried at 60-100℃ for 5-8h to remove the ball milling solvent. The dried powder is sieved through a 60-100 mesh sieve, and the sieved material is poured into a crucible and heated to 750-900℃ at a heating rate of 150-250℃ / h, and kept warm for 2-4h for the first sintering to initially form Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 piezoelectric ceramic crystal phase to obtain a mixed material.

[0087] From the above content, it can be seen that the mixed material after the first sintering needs to be crushed and ground by a second ball mill. Please refer to Figure 6In this embodiment, S300, "subjecting the mixed material to a second ball milling, tableting, binder removal, and a second sintering in sequence to obtain a ceramic sheet" includes S310. The detailed description of S310 is as follows: During the second ball milling, the ratio of the mixed material to the second ball milling solvent is 1:(0.6-0.8), and the direction of ball milling is changed every 20-40 minutes.

[0088] During the second ball milling, the ratio of the mixed material to the second ball milling solvent can be 1: (0.6-0.8), and the direction of the ball milling can be changed every 20-40 minutes. Through the above operation, the effect of the second ball milling is better, the particle size of the powder after ball milling is smaller, the mixing is more uniform, and the contact between the materials is more sufficient, so that the subsequent second sintering effect is better.

[0089] Specifically, in this embodiment, the mixed material obtained by the first sintering can be crushed and put into a ball mill, and a ball milling medium and a ball milling solvent are added, and the ratio of the mixed material to the second ball milling solvent is 1: (0.6-0.8). The ball milling speed is adjusted to 200-300r / min, the ball milling time is 22-26h for ball milling, and the direction of ball milling is changed every 20-40min, so as to refine the powder particle size of the mixed material and prevent the phenomenon of uneven mixing in the subsequent process. Optionally, the ball mill can be a 500ml polyurethane ball mill, the ball milling medium can be a zirconium ball, and the ball milling solvent can be anhydrous ethanol.

[0090] Specifically, the ratio of the mixed material to the ball milling solvent during the second ball milling can be 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8. The time for changing the direction during the second ball milling can be changed every 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes.

[0091] The mixture after the second ball milling is dried at 60-100°C for 5-8h to remove the ball milling solvent. After drying, the powder is passed through a 60-100 mesh sieve, and the sieved material is added with an adhesive for granulation. Optionally, the adhesive can be a 3%-5% aqueous solution of polyvinyl alcohol (PVA), and the amount of adhesive added can be 15%-25% of the mass of the sieved material. After granulation, the mixture is dried at 60-100°C, and attention is paid to the dryness of the powder. Overly wet powder is easy to adhere to the screen during subsequent screening, resulting in waste, while overly dry powder will cause difficulty in screening.

[0092] From the above content, it can be seen that the ceramic body needs a debinding process to remove the adhesive. Please refer to Figure 7In this embodiment, S300, "subjecting the mixed material to a second ball milling, tableting, debinding, and a second sintering in sequence to obtain a ceramic sheet" includes S320. The detailed description of S320 is as follows: during the debinding, the mixed material after tableting is placed in a crucible covered with a landfill material and heated at a temperature of 550-650°C for a holding time of 1.5-2h.

[0093] In this embodiment, the binder removal temperature is set at 550-650° C. and kept at this temperature for 1.5-2 hours, so that the binder is discharged more completely and the binder removal effect is better, thereby preventing the binder from affecting the growth of ceramic grains during the subsequent high-temperature sintering process.

[0094] Specifically, in this embodiment, an appropriate amount of dried powder can be weighed, and tabletted at a pressure of 4-8 MPa and maintained at the pressure for 1-3 minutes to obtain a ceramic body with a thickness of 1-2 mm. The tabletted mixture is placed in a crucible covered with a landfill material and heated at a heating rate of 150-250°C / h to 550-650°C, and maintained at this temperature for 1.5-2 hours.

[0095] Specifically, the debinding temperature may be 550° C., 580° C., 600° C., 620° C., or 650° C. The insulation time may be 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, or 2.0 h.

[0096] From the above content, it can be seen that the ceramic body after debinding needs to be sintered for the second time to obtain ceramic sheets. Please refer to Figure 8 In this embodiment, S300, "subjecting the mixture to a second ball milling, tablet pressing, binder removal, and second sintering in sequence to obtain a ceramic sheet" includes S330. The detailed description of S330 is as follows: during the second sintering, the landfill covers the binder-removed mixture, and the landfill and the binder-removed mixture are heated for the first time at a temperature of 750-850°C for a holding time of 2-4h, and then heated for the second time at a temperature of 980-1080°C for a holding time of 2-4h.

[0097] In this embodiment, the two-step sintering method is used to make the grains dense enough during the growth process, which is conducive to the ceramic to exert better performance. Through the burying method, the ceramic embryo is buried in the filler zirconium oxide powder, which reduces the volatilization of bismuth oxide in the ceramic material during high-temperature sintering.

[0098] Specifically, in this embodiment, the ceramic body after debinding can be completely covered with a landfill material, and the landfill material can be zirconium oxide powder, and then the ceramic body is heated. First, the temperature is raised to 750-850°C at a heating rate of 150-250°C / h, and kept at this temperature for 2-4 hours, and then the temperature is raised to 980-1080°C at the same heating rate and kept for 2-4 hours. Then, the temperature is lowered to 750-850°C at 150-250°C / h and kept for 2-4 hours, and finally cooled to room temperature with the furnace to obtain a ceramic sheet.

[0099] Specifically, the temperature of the first heating may be 750° C., 780° C., 800° C., 820° C., 850° C. The temperature of the second heating may be 980° C., 1000° C., 1020° C., 1040° C., 1060° C., 1080° C. The holding time of the first heating and the second heating may be 2 h, 2.5 h, 3 h, 3.5 h, 4 h.

[0100] From the above content, it can be seen that the fired ceramic sheet still needs to undergo a polarization process. Please refer to Fig. 9 In this embodiment, S400, "performing a polarization process on the ceramic sheet to obtain a piezoelectric ceramic material" includes S410. The detailed description of S410 is as follows: during the polarization process, a conductive material is applied to the surface of the ceramic sheet, and heated and fired to convert the conductive material into an electrode, the firing temperature is 550-650°C, the heat preservation time is 5-15 minutes, and the ceramic sheet after firing the electrode is polarized to obtain a piezoelectric ceramic material.

[0101] In this embodiment, the ceramic sheet is polarized to have piezoelectric properties. The firing temperature and the holding time are set during firing, so that the piezoelectric ceramic material is more fully polarized and has better piezoelectric properties.

[0102] Specifically, during the polarization process, the sintered ceramic sheet can be thinned, and the conductive material can be evenly applied to the ceramic surface with a brush and dried. Optionally, the conductive material is a conductive silver paste. The dried ceramic sheet is heated to solidify the conductive material and transform it into an electrode. The heating temperature is 550-650°C and the temperature is kept for 5-15 minutes. Then, a direct current voltage of 5-15 kV / mm is applied to the ceramic sheet at 100-140°C for polarization for 12-17 minutes to obtain a piezoelectric ceramic material.

[0103] Specifically, the electrode firing temperature may be 550° C., 580° C., 600° C., 620° C., or 650° C. The insulation time may be 5 min, 7 min, 10 min, 12 min, or 15 min.

[0104] Please refer to Fig.10This embodiment provides an energy collection device, which includes a piezoelectric ceramic material as provided in the above embodiment of the present application, and the energy collection device satisfies at least one of the following conditions: the peak value of the open circuit voltage of the energy collection device at 300°C is 2.0-2.5V; the power generation energy density of the energy collection device at 300°C is 0.0025-0.0030μW / mm 3 .

[0105] The energy collection device provided in this embodiment is mainly used to recycle the vibration energy in the environment and convert it into electrical energy, which is then used to power the microsensor, thereby realizing the self-powering of the microsensor. The energy collection device in this embodiment mainly includes piezoelectric ceramic material, mass block, electrode, and fixed base. The energy collection device in this embodiment is fixed to the vibration source through a fixed base, the piezoelectric ceramic material is fixed to the fixed base, the electrodes are arranged on opposite sides of the piezoelectric ceramic material, and the mass block is fixed to the fixed base. Fig.10 The upper surface of the piezoelectric ceramic material shown. When the vibration source vibrates, the mass block generates pressure on the piezoelectric ceramic material, and a voltage difference is generated on the surface of the piezoelectric ceramic and subsequently transmitted to the microsensor or energy storage device that needs power through the electrode. Optionally, the energy harvesting device can be a cantilever beam single-layer energy harvester.

[0106] The energy harvesting device in this embodiment has at least one of the following characteristics, that is, it can satisfy only one characteristic or both characteristics: the energy harvesting device has an open circuit voltage peak of 2.0-2.5V at 300°C; the energy harvesting device has an open circuit voltage peak of 0.0025-0.0030μW / mm at 300°C 3 power generation energy density.

[0107] The energy harvesting device in this embodiment uses the piezoelectric ceramic material in this embodiment, so that the energy harvesting device has an open circuit voltage peak of 2.0-2.5V and a current of 0.0025-0.0030μW / mm at a high temperature of 300°C. 3 At least one of the two characteristics of power generation energy density, that is, the energy harvesting device still has good power supply performance at a high temperature of 300°C. It is convenient to apply the energy harvesting device to complex high-temperature environments, thereby realizing the self-power supply of microsensors in green power systems, which has significant social significance and economic value.

[0108] Specifically, the peak open circuit voltage of the energy harvesting device in this embodiment at 300°C is 2.0V, 2.1V, 2.2V, 2.3V, 2.4V, and 2.5V. The power generation energy density of the energy harvesting device at 300°C is 0.0025μW / mm 3 、0.0026μW / mm 3 、0.0027μW / mm3 、0.0028μW / mm 3 、0.0029μW / mm 3 、0.0030μW / mm 3 .

[0109] In order to enable those skilled in the art to clearly understand the implementation details and operations of the present invention, and to demonstrate the significant improvement in the performance of the method for preparing piezoelectric ceramic materials in the embodiments of the present invention, the above technical solutions are illustrated by multiple embodiments below.

[0110] Embodiment 1:

[0111] Weigh 1 mol Na 0.5 Bi 4.5 Ti 4 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (320.12g) powder raw materials are mixed and mixed evenly by wet ball milling process, and the ball milling time is 16 hours. After the uniformly ball-milled powder is dried at 80°C, it is sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture is ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder is dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo is heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet is polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 4 O 15 .

[0112] Embodiment 2:

[0113] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.98 Mn 0.02 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (318.519 g), MnO 2(1.74g) powder raw materials were mixed and mixed evenly using a wet ball milling process for 16 hours. After the evenly ball-milled powder was dried at 80°C, it was sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture was ball-milled for 12 hours to obtain a ceramic powder, and then the ceramic powder was dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo was heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet was polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.98 Mn 0.02 O 15 .

[0114] Embodiment 3:

[0115] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.96 Mn 0.04 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (316.919 g), MnO 2 (3.479g) powder raw materials are mixed and mixed evenly by wet ball milling process, and the ball milling time is 16 hours. After the uniformly ball-milled powder is dried at 80°C, it is sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture is ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder is dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo is heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet is polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.96 Mn 0.04 O 15 .

[0116] Embodiment 4:

[0117] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.94 Mn 0.06 O 15 Required Na2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (315.318 g), MnO 2 (5.219g) powder raw materials were mixed and mixed evenly by wet ball milling process for 16 hours. After the uniformly ball-milled powder was dried at 80°C, it was sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture was ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder was dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo was heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet was polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.94 Mn 0.06 O 15 .

[0118] Embodiment 5:

[0119] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.92 Mn 0.08 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (313.718 g), MnO 2 (6.959g) powder raw materials are mixed and mixed evenly by wet ball milling process, and the ball milling time is 16 hours. After the uniformly ball-milled powder is dried at 80°C, it is sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture is ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder is dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo is heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet is polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.92 Mn 0.08 O 15 .

[0120] Embodiment 6:

[0121] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.9 Mn 0.06 Nb 0.04 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (312.117 g), MnO 2 (5.219 g), Nb 2 O 5 (5.322g) powder raw materials are mixed and mixed evenly by wet ball milling process, and the ball milling time is 16 hours. After the uniformly ball-milled powder is dried at 80°C, it is sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture is ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder is dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo is heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet is polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.9 Mn 0.06 Nb 0.04 O 15 .

[0122] Embodiment 7:

[0123] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.86 Mn 0.06 Nb 0.08 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (308.916g), MnO 2 (5.219 g), Nb 2 O 5(10.643g) powder raw materials were mixed and mixed evenly by wet ball milling process for 16 hours. After the evenly ball-milled powder was dried at 80°C, it was sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture was ball-milled for 12 hours to obtain ceramic powder, and then the ceramic powder was dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo was heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet was polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.86 Mn 0.06 Nb 0.08 O 15 .

[0124] Embodiment 8:

[0125] Weigh 1 mol Na 0.5 Bi 4.5 Ti 3.82 Mn 0.06 Nb 0.12 O 15 Required Na 2 CO 3 (26.524g), Bi 2 O 3 (1059g), TiO 2 (305.715g), MnO 2 (5.219 g), Nb 2 O 5 (15.965g) powder raw materials were mixed and mixed evenly using a wet ball milling process for 16 hours. After the evenly ball-milled powder was dried at 80°C, it was sintered for the first time at 800°C for 3 hours to obtain a mixture. The mixture was ball-milled for 12 hours to obtain a ceramic powder, and then the ceramic powder was dried at 80°C, passed through an 80-mesh sieve, granulated and pressed to obtain a ceramic embryo. The ceramic embryo was heated to 600°C at 200°C / h and kept warm for 1h, then heated to 980°C at 200°C / h and kept warm for 3h, then cooled to 800°C at 200°C / h and kept warm for 3h, and finally cooled to room temperature with the furnace to obtain a ceramic sheet, and the ceramic sheet was polarized to obtain the piezoelectric ceramic material Na 0.5 Bi 4.5 Ti 3.82 Mn 0.06 Nb 0.12 O 15 .

[0126] After obtaining the piezoelectric ceramic material products of Examples 1-8, the present application also conducted a variety of performance tests on the products obtained in Examples 1-8 to verify the excellent performance of the piezoelectric ceramic materials in the present application.

[0127] Please refer to Figure 1 The XRD phase structure test results of Examples 1-5 show that the introduction of manganese element does not produce other miscellaneous products. All ceramic samples have a single m=4 orthorhombic bismuth layered structure, and the crystal plane index (1 1 9) of the strongest diffraction peak is consistent with the strongest peak (1 1 2m+1) of the bismuth layered structure ceramics.

[0128] Please refer to Fig.11 It can be seen from the scanning electron microscope (SEM) images of Examples 1-5 that the surface grains of all samples are "flat fish scale-like", which is a typical bismuth layered structure feature. In addition, the density of pure NBT ceramics in Example 1 is relatively poor. The introduction of an appropriate amount of manganese elements can make the grain size of the ceramics uniform and refined, thereby improving the density of the ceramic material. And with the introduction of manganese elements, the grain size shows a trend of first decreasing and then increasing, and when the introduction ratio of manganese elements is 0.06, the grain size is the smallest, which effectively improves the chemical properties of the piezoelectric ceramic material.

[0129] Please refer to Figure 12-13 , it can be seen from the temperature variation diagram of the dielectric properties of Examples 1-5 that with the introduction of manganese, the dielectric constant of the ceramic material shows a trend of gradually increasing. It can be seen from the temperature variation diagram of the dielectric loss of Examples 1-5 that with the introduction of manganese, the dielectric loss of the ceramic material shows a trend of first decreasing and then increasing, and the dielectric loss is the smallest when the introduction ratio of manganese is 0.06, and tanδ=0.0066 at room temperature. At the same time, the dielectric loss has an obvious loss peak at around 650°C, and the corresponding temperature here is the Curie temperature of the ceramic material.

[0130] Please refer to Fig.14 It can be seen from the room temperature piezoelectric coefficient diagram of Examples 1-5 that with the introduction of manganese, the piezoelectric coefficient shows a trend of first increasing and then decreasing, and the best room temperature piezoelectric performance is obtained when the manganese content is 0.06. 33 =28pC / N.

[0131] Please refer to Figure 2 The XRD phase structure test results of Example 1, Example 4, and Examples 6-8 show that the co-introduction of manganese and niobium elements does not produce other miscellaneous products. All ceramic samples have a single m=4 orthorhombic bismuth layered structure, and the crystal plane index (1 1 9) of the strongest diffraction peak is consistent with the strongest peak (1 1 2m+1) of the bismuth layered structure ceramics.

[0132] Please refer to Figure 15-16It can be seen from the scanning electron microscope (SEM) images of Example 1, Example 4, and Examples 6-8 that the surface grains of all samples are "flat fish scale-like", which is a typical bismuth layered structure feature. In addition, the density of pure NBT ceramics in Example 1 is relatively poor, and the introduction of an appropriate amount of niobium element can make the grain size of the ceramic uniform and refined. And with the introduction of niobium element, the grain size shows a trend of first decreasing and then increasing, and when the introduction ratio of niobium element is 0.04, the grain size is the smallest, the relative density is greater, and the compactness is the best.

[0133] Please refer to Figure 3 , Fig.17 , it can be seen from the temperature variation diagram of the dielectric properties of Example 1, Example 4, and Examples 6-8 that with the introduction of niobium, the dielectric constant of the ceramic material shows a trend of gradually increasing. It can be seen from the temperature variation diagram of the dielectric loss of Example 1, Example 4, and Examples 6-8 that the dielectric loss tanδ has been kept below 0.03 in the range of room temperature to 500°C. And with the introduction of niobium, the dielectric loss of the ceramic material shows a trend of first decreasing and then increasing, indicating that the introduction of an appropriate amount of niobium can reduce the loss of NBT-based ceramics at high temperatures and improve its high temperature stability.

[0134] Moreover, when the introduction ratio of niobium is 0.04, the dielectric loss is the smallest, tanδ=0.0065 at room temperature, and the dielectric loss remains the smallest at high temperature (above 500°C). At the same time, there is an obvious loss peak at around 670°C, indicating that when the introduction ratio of niobium is 0.04, the Curie temperature of the piezoelectric ceramic material reaches 670°C.

[0135] Please refer to Fig.18 The piezoelectric coefficient curves of Example 1, Example 4, and Examples 6-8 show that the introduction of niobium effectively improves the piezoelectric properties of NBT-based ceramics. Overall, when the niobium content is 0.04, the piezoelectric performance is the best, and the piezoelectric coefficient reaches 33pC / N at room temperature.

[0136] Please refer to Fig.19 From the piezoelectric coefficient diagrams of Examples 1, 4, and 6-8 at different polarization temperatures, it can be seen that with the increase of polarization temperature, the room temperature piezoelectric coefficient d 33 However, when the polarization temperature exceeds 120℃, d 33 The piezoelectric coefficient d remains unchanged or decreases slightly. This may be because at higher temperatures, space charges tend to accumulate at the grain boundaries, making it difficult for polarization to be sufficient or breakdown failure occurs, resulting in a 33 reduce.

[0137] Please refer to Fig. 20From the piezoelectric coefficient test graphs of Example 1, Example 4, and Examples 6-8 from room temperature to 450°C, it can be seen that all samples have good temperature stability, and the piezoelectric coefficient d 33 When the niobium content is 0.04, the piezoelectric coefficient rises to d 33 =40pC / N.

[0138] In summary, the following conclusions can be clearly drawn from the results of the above various performance tests: the piezoelectric ceramic material in this embodiment is formed by the bismuth layered ceramic Na 0.5 Bi 4.5 Ti 4 O 15 By introducing appropriate amounts of manganese and niobium elements and controlling the ratio between the two, the structure of the piezoelectric ceramic material is made denser, the piezoelectric performance is significantly improved, and the stability of the piezoelectric performance under high temperature conditions is improved. At the same time, the dielectric loss of the piezoelectric ceramic material is significantly reduced.

[0139] The above describes the contents provided by the implementation methods of the present application in detail, and describes and illustrates the principles and implementation methods of the present application. These descriptions are only used to help understand the method and its core ideas of the present application. However, the contents of this specification should not be construed as limiting the present application, and those skilled in the art may make various changes and modifications to the present application without departing from the spirit and scope of the present application. These modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents.

Claims

1. A piezoelectric ceramic material, characterized in that: The chemical composition of the piezoelectric ceramic material is Na 0.5 Bi 4.5 Ti 4- z Mn x Nb y O 15 , where 0<x≤0.08, 0≤y≤0.12, x+y=z.

2. The ceramic material according to claim 1, characterized in that The piezoelectric ceramic material is a bismuth layered structure and is a layered perovskite structure ceramic material with m=4.

3. The ceramic material according to claim 1, characterized in that When x=0.06, y=0.04, the piezoelectric coefficient d of the piezoelectric ceramic material at 300°C is 33 is 38-42pC / N, and the Curie temperature T c It is 665-675℃.

4. The ceramic material according to claim 1, characterized in that When 0≤y≤0.12, the dielectric loss tanδ of the piezoelectric ceramic material first decreases and then increases with the introduction of niobium element.

5. A method for preparing a piezoelectric ceramic material, characterized in that: The preparation method comprises: The sodium source, bismuth source, titanium source, manganese source, and niobium source are prepared according to the chemical formula Na 0.5 Bi 4.5 Ti 4-z Mn x Nb y O 15 The raw material is weighed in a stoichiometric ratio, wherein 0<x≤0.08, 0≤y≤0.12, x+y=z; The raw materials are subjected to a first ball milling and a first sintering in sequence to obtain a mixed material; The mixed material is subjected to a second ball milling, tablet pressing, binder removal, and a second sintering in sequence to obtain a ceramic sheet; The ceramic sheet is subjected to a polarization process to obtain a piezoelectric ceramic material.

6. The preparation method according to claim 5, characterized in that: During the first ball milling, the ratio of the raw material to the first ball milling solvent is 1:(0.8-1.2), and the direction of ball milling is changed every 20-40 minutes; during the second ball milling, the ratio of the mixed material to the second ball milling solvent is 1:(0.6-0.8), and the direction of ball milling is changed every 20-40 minutes.

7. The preparation method according to claim 5, characterized in that: During the debinding process, the mixed material after tableting is placed in a crucible covered with a landfill material and heated at a temperature of 550-650° C. for a holding time of 1.5-2 hours.

8. The preparation method according to claim 5, characterized in that: During the second sintering, the landfill covers the debinding mixture, and the landfill and the debinding mixture are heated for the first time at a temperature of 750-850°C for 2-4 hours, and then heated for the second time at a temperature of 980-1080°C for 2-4 hours.

9. The preparation method according to claim 5, characterized in that: During the polarization process, a conductive material is applied to the surface of the ceramic sheet, and heated and fired to convert the conductive material into an electrode. The firing temperature is 550-650°C, and the insulation time is 5-15 minutes. The ceramic sheet after firing the electrode is polarized to obtain a piezoelectric ceramic material.

10. An energy collection device, characterized in that: The energy collection device comprises the piezoelectric ceramic material according to any one of claims 1 to 4, and the energy collection device satisfies at least one of the following conditions: The peak open circuit voltage of the energy harvesting device at 300°C is 2.0-2.5V; The energy density of the energy harvesting device at 300°C is 0.0025-0.0030 μW / mm 3 .

Images