Lead-free pyroelectric ceramic material with high depoling temperature, method for preparing the same and use thereof

Abstract

This invention belongs to the field of pyroelectric infrared detection technology, specifically providing a lead-free pyroelectric ceramic material with a high depolarization temperature. The chemical composition of the lead-free pyroelectric ceramic material is: 0.99Bi. x Na y TiO3-0.01BaTiO3; where x and y are molar percentages, and x / y=(0.4-0.5) / (0.5-0.6). Through Bi x Na y A small amount of BaTiO3 was added to TiO3, and the contents of Na and Bi were adjusted. A small amount of Ba... 2+ Introducing Bi to form a stable R3c rhombohedral phase structure lattice 3+ Na + Ion volatilization creates defects that increase the electrical conductivity of the material, making it easier to polarize. This, in turn, greatly improves the room-temperature pyroelectric coefficient of the material even with little change in depolarization temperature.

Description

Technical Field

[0001] This invention pertains to pyroelectric infrared detection, specifically relating to a lead-free pyroelectric ceramic material with high depolarization temperature, its preparation method, and its applications. Background Technology

[0002] The pyroelectric effect refers to the phenomenon where a material experiences charge separation due to temperature changes. This charge separation creates a potential difference across the material, thus generating a voltage. Pyroelectric materials are widely used in uncooled infrared detectors. Uncooled infrared detectors based on the pyroelectric effect offer advantages such as fast response, low signal hysteresis, high sensitivity, wide receiving spectrum, and good recognition. They have wide applications not only in infrared imaging, night vision equipment, and fire safety, but also hold great potential in the next generation of smart homes.

[0003] Pyroelectric materials, as the core sensing elements of uncooled infrared detectors, are crucial in determining the performance of these detectors. Therefore, the research and development of high-performance pyroelectric materials is of great significance. Common commercially available pyroelectric sensing elements are mainly lead-based materials such as lead zirconate titanate (PZT) and lead titanate (PT). However, lead-based materials are highly susceptible to lead pollution during production and after disposal, endangering human health and violating the principles of sustainable development. Therefore, finding lead-free pyroelectric sensing elements to replace lead-based materials is urgently needed.

[0004] Currently, lead-free pyroelectric materials mainly include barium strontium niobate (SBN), barium titanate (BT), sodium bismuth titanate (BNT), sodium potassium niobate (KNN), and bismuth layered ferroelectric (BLSF) ceramics. While KNN and BLSF ceramics have high depolarization temperatures, their room-temperature pyroelectric coefficients are low. SBN, BT, and BNT have high room-temperature pyroelectric coefficients, but their low depolarization limits their practical applications. Furthermore, the Curie temperatures of SBN and BT are below 150°C, making it difficult to increase their depolarization temperatures. Uncooled infrared detectors used in next-generation smart home applications must be compatible with surface-mount reflow soldering processes to achieve device miniaturization and integration. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that it is difficult to achieve both room temperature pyroelectric coefficient and depolarization temperature in existing lead-free pyroelectric materials.

[0006] Therefore, the present invention provides a lead-free pyroelectric ceramic material with a high depolarization temperature, wherein the chemical composition of the lead-free pyroelectric ceramic material is: 0.99Bi x Na y TiO3-0.01BaTiO3; where x and y are molar percentages, and x / y = (0.4-0.5) / (0.5-0.6).

[0007] Specifically, the above x / y = 0.5 / 0.5, 0.45 / 0.55, 0.49 / 0.55, 0.4 / 0.6 or 0.47 / 0.6.

[0008] The present invention also provides a method for preparing the above-mentioned lead-free pyroelectric ceramic material, comprising the following steps:

[0009] (1) Weigh out Bi2O3, Na2CO3, TiO2, and BaCO3 raw materials according to the stoichiometric ratio of lead-free pyroelectric ceramic materials;

[0010] (2) The raw materials are ball-milled and mixed to obtain a mixed powder;

[0011] (3) The obtained mixed powder is successively dried, sieved, pre-fired, ball-milled twice, dried, granulated, pressed into tablets and sintered to obtain the lead-free pyroelectric ceramic material.

[0012] Specifically, the ball milling conditions in steps (2) and (3) above are as follows: a polyurethane ball milling jar is used, zirconium balls are used as the ball milling medium, and anhydrous ethanol is used as the ball milling solvent for ball milling and mixing.

[0013] Specifically, in step (2) above, the mass ratio of raw material to ball milling solvent during ball milling is 1:0.8-1:1.2, and the ball milling time is 10-12h; in step (3) during secondary ball milling, the mass ratio of pre-calcined powder to ball milling solvent is 1:0.6-1:0.8, and the ball milling time is 10-12h.

[0014] Specifically, the pre-firing conditions in step (3) above are: heating to 850-900℃ at 180℃ / h and then holding for 4-6 hours.

[0015] Specifically, in step (3) above, a polyvinyl alcohol aqueous solution with a mass fraction of 3-5% is used as a binder for granulation; the amount of binder added is 10-20% of the mass of the dried powder.

[0016] Specifically, the tableting conditions in step (3) above are: holding pressure at 100-150 MPa for 4-6 minutes.

[0017] Specifically, the sintering procedure in step (3) above is as follows: heat up to 550-600℃ at 5℃ / min and hold for 1.5-2h, then heat up to 1140-1160℃ at 3℃ / min and hold for 2-4h, and then cool to room temperature with the furnace.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] 1. The high depolarization temperature lead-free pyroelectric ceramic material provided by this invention is obtained by using 0.99Bi... x Nay TiO3-0.01BaTiO3 pyroelectric ceramics were obtained by adjusting the contents of Na and Bi. (The remaining text appears to be incomplete and possibly contains errors. A more accurate translation would require the full context.) x Na y A small amount of BaTiO3 was added to TiO3, and the contents of Na and Bi were adjusted. 2+ Introducing an R3c rhombohedral phase structure to stabilize its crystal lattice increases the depolarization temperature of lead-free pyroelectric sensitive ceramics from 220℃ to 240℃. When the x / y ratio is 0.49 / 0.55, the depolarization temperature can reach up to 240℃. 3+ Na + Ion volatilization creates defects that lower the electrical conductivity energy barrier of the ceramic, making the ions more active and thus more sensitive to temperature changes. This results in an increase in its room-temperature pyroelectric coefficient, from 3.08 × 10⁻⁶. -4 C m -2 K -1 Increased to 17.71×10 -4 C m -2 K -1 When the Bi / Na content ratio is 0.49 / 0.55, its room temperature pyroelectric coefficient can reach a maximum of 17.71 × 10⁻⁶. -4 C m -2 K -1 This lead-free pyroelectric ceramic material can be used as the core sensitive element of an uncooled infrared detector.

[0020] 2. The method for preparing high depolarization temperature lead-free pyroelectric ceramic materials provided by this invention uses a solid-state method to prepare 0.99Bi x Na y The sintering temperature of lead-free pyroelectric ceramics (TiO3-0.01BaTiO3) is as follows: heat to 550-600℃ at a rate of 5℃ / min and hold for 1.5-2 hours, then heat to 1130-1150℃ at a rate of 3℃ / min and hold for 3-5 hours, followed by furnace cooling to room temperature. This method can simply and effectively improve both the room temperature pyroelectric coefficient and depolarization temperature of lead-free pyroelectric ceramics. (The text also mentions using 0.99Bi...) x Na y Lead-free pyroelectric ceramics were obtained by adjusting the Na and Bi contents in TiO3-0.01BaTiO3 pyroelectric ceramics. Only the Na content was adjusted. + Bi 3+ The proportion in ceramics is maintained at 0.99Bi. 0.5 Na 0.5 The TiO3-0.01BaTiO3 structure is stable perovskite, and its increased conductivity makes it easier to polarize, thus improving the room temperature pyroelectric coefficient of the material.

[0021] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is an XRD diagram of the lead-free pyroelectric ceramic material in an embodiment of the present invention.

[0023] Figure 2 This is a SEM image of the lead-free pyroelectric ceramic material in an embodiment of the present invention.

[0024] Figure 3 This is a diagram showing the pyroelectric coefficient of the lead-free pyroelectric ceramic material in this embodiment of the invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0026] This invention provides a lead-free pyroelectric ceramic material with a high depolarization temperature, wherein the chemical composition of the lead-free pyroelectric ceramic material is: 0.99Bi. x Na y TiO3-0.01BaTiO3; which is in 0.99Bi x Na y TiO3-0.01BaTiO3 was obtained by adjusting the content of Na and Bi, where x and y are molar percentages, and x / y = (0.4-0.5) / (0.5-0.6).

[0027] The ratio of x to y is preferably 0.5 / 0.5, 0.45 / 0.55, 0.49 / 0.55, 0.4 / 0.6, or 0.47 / 0.6. More preferably, x / y = 0.49 / 0.55.

[0028] This invention also provides a method for preparing the above-mentioned lead-free pyroelectric ceramic material, by means of Bi x Na y A small amount of BaTiO3 was added to TiO3, and the contents of Na and Bi were adjusted. A small amount of Ba... 2+ Introducing Bi to form a stable R3c rhombohedral phase structure lattice 3+ Na +Ion volatilization creates defects that increase the material's electrical conductivity, making it easier to polarize. This, in turn, significantly improves the room-temperature pyroelectric coefficient with minimal change in depolarization temperature. The preparation method includes the following steps:

[0029] (1) Weigh out Bi2O3, Na2CO3, TiO2 and BaCO3 raw materials according to the stoichiometric ratio of lead-free pyroelectric ceramic materials.

[0030] (2) The raw materials are ball-milled and mixed to obtain a mixed powder.

[0031] Specifically, the milling jar is a polyurethane milling jar, the milling media is zirconium balls, the milling solvent is anhydrous ethanol, the mass ratio of raw material to milling solvent is 1:0.8-1:1.2, and the milling time is 10-12 hours.

[0032] (3) Bake the resulting mixed powder in an oven at 60-100℃ for 5-8 hours, pass it through a 60-100 mesh sieve, and take the material passing through the 60-100 mesh sieve for pre-calcination.

[0033] The preheating conditions are: heat up to 850-900℃ at a rate of 180℃ / h and then hold at that temperature for 4-6 hours.

[0034] The pre-calcined powder is then subjected to a second ball milling process. A polyurethane ball milling jar is used, zirconium balls are used as the milling media, and anhydrous ethanol is used as the milling solvent. The mass ratio of the pre-calcined powder to the milling solvent is 1:0.6-1:0.8, and the milling time is 10-12 hours. After the second ball milling, the powder is baked in an oven at 60-100℃ for 5-8 hours.

[0035] After drying, the powder is granulated, and a 3-5% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation; the amount of binder added is 10-20% of the mass of the dried powder.

[0036] After granulation, the material is pressed into tablets at 100-150 MPa for 4-6 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0037] The sintering process is as follows: heat up to 550-600℃ at 5℃ / min and hold for 1.5-2 hours, then heat up to 1140-1160℃ at 3℃ / min and hold for 2-4 hours, and then cool to room temperature with the furnace.

[0038] The following specific embodiments illustrate the effects of the high depolarization temperature lead-free pyroelectric ceramic material of the present invention, its preparation method, and its application.

[0039] Example 1:

[0040] This embodiment provides a lead-free pyroelectric ceramic material with a high depolarization temperature, whose chemical composition is: 0.99Bi 0.5Na 0.5 TiO3-0.01BaTiO3 is prepared by the following method:

[0041] (1) Weigh 115.672g of Bi2O3, 26.230g of Na2CO3, 80.026g of TiO2 and 1.978g of BaCO3 powder raw materials according to the stoichiometric ratio of 1mol of lead-free pyroelectric ceramic material.

[0042] (2) The raw materials are ball-milled and mixed using a wet ball milling process to obtain a mixed powder.

[0043] The ball milling jar is a 500ml polyurethane ball milling jar, the ball milling media is zirconium balls, the ball milling solvent is anhydrous ethanol, the mass ratio of ball milling media, raw material and anhydrous ethanol is 100:40:40, and the ball milling time is 12h.

[0044] (3) The resulting mixed powder is baked at 80°C for 5 hours, passed through an 80-mesh sieve, and the sieve material is pre-burned.

[0045] The preheating conditions are: heat up to 850℃ at a rate of 180℃ / h and then hold at that temperature for 6 hours.

[0046] The pre-calcined powder was subjected to a second ball milling process. A polyurethane ball milling jar was used, zirconium balls were used as the milling media, and anhydrous ethanol was used as the milling solvent. The mass ratio of milling media, pre-calcined powder, and anhydrous ethanol was 100:40:40, and the milling time was 12 hours. After the second ball milling, the powder was baked at 80℃ for 5 hours and then passed through an 80-mesh sieve.

[0047] After drying, the powder is granulated. A 4% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder added is 15% of the mass of the dried powder.

[0048] After granulation, the material is pressed into tablets at 120 MPa for 5 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0049] The sintering process is as follows: heat up to 600℃ at 5℃ / min and hold for 2 hours, then heat up to 1150℃ at 3℃ / min and hold for 4 hours, and then cool to room temperature with the furnace.

[0050] The XRD pattern of the lead-free pyroelectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2 As shown in (a). The sintered lead-free pyroelectric ceramic material was polished to 0.3 mm, silver paste was screen-printed, dried, and held at 600℃ for 20 minutes. After polarization with a DC voltage of 4.5 kV / mm at room temperature for 30 minutes, the pyroelectric coefficient of the sample was tested as follows. Figure 3 As shown.

[0051] Example 2:

[0052] This embodiment provides a lead-free pyroelectric ceramic material with a high depolarization temperature, whose chemical composition is: 0.99Bi 0.45 Na 0.55 TiO3-0.01BaTiO3 is prepared by the following method:

[0053] (1) Weigh 104.841g of Bi2O3, 28.881g of Na2CO3, 80.026g of TiO2 and 1.978g of BaCO3 powder raw materials according to the stoichiometric ratio of 1mol of lead-free pyroelectric ceramic material.

[0054] (2) The raw materials are ball-milled and mixed using a wet ball milling process to obtain a mixed powder.

[0055] The ball milling jar is a 500ml polyurethane ball milling jar, the ball milling media is zirconium balls, the ball milling solvent is anhydrous ethanol, the mass ratio of ball milling media, raw material and anhydrous ethanol is 100:40:40, and the ball milling time is 12h.

[0056] (3) The resulting mixed powder is baked at 80°C for 5 hours, passed through an 80-mesh sieve, and the sieve material is pre-burned.

[0057] The preheating conditions are: heat up to 850℃ at a rate of 180℃ / h and then hold at that temperature for 6 hours.

[0058] The pre-calcined powder was subjected to a second ball milling process. A polyurethane ball milling jar was used, zirconium balls were used as the milling media, and anhydrous ethanol was used as the milling solvent. The mass ratio of milling media, pre-calcined powder, and anhydrous ethanol was 100:40:40, and the milling time was 12 hours. After the second ball milling, the powder was baked at 80℃ for 5 hours and then passed through an 80-mesh sieve.

[0059] After drying, the powder is granulated. A 4% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder added is 15% of the mass of the dried powder.

[0060] After granulation, the material is pressed into tablets at 120 MPa for 5 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0061] The sintering process is as follows: heat up to 600℃ at 5℃ / min and hold for 2 hours, then heat up to 1150℃ at 3℃ / min and hold for 4 hours, and then cool to room temperature with the furnace.

[0062] The XRD pattern of the lead-free pyroelectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2As shown in (b). The sintered lead-free pyroelectric ceramic material was polished to 0.3 mm, silver paste was screen-printed, dried, and held at 600℃ for 20 minutes. After polarization with a DC voltage of 4.5 kV / mm at room temperature for 30 minutes, the pyroelectric coefficient of the sample was tested as follows. Figure 3 As shown.

[0063] Example 3:

[0064] This embodiment provides a lead-free pyroelectric ceramic material with a high depolarization temperature, whose chemical composition is: 0.99Bi 0.49 Na 0.55 TiO3-0.01BaTiO3 is prepared by the following method:

[0065] (1) Weigh 114.160g of Bi2O3, 28.881g of Na2CO3, 80.026g of TiO2 and 1.978g of BaCO3 powder raw materials according to the stoichiometric ratio of 1mol of lead-free pyroelectric ceramic material.

[0066] (2) The raw materials are ball-milled and mixed using a wet ball milling process to obtain a mixed powder.

[0067] The ball milling jar is a 500ml polyurethane ball milling jar, the ball milling media is zirconium balls, the ball milling solvent is anhydrous ethanol, the mass ratio of ball milling media, raw material and anhydrous ethanol is 100:40:40, and the ball milling time is 12h.

[0068] (3) The resulting mixed powder is baked at 80°C for 5 hours, passed through an 80-mesh sieve, and the sieve material is pre-burned.

[0069] The preheating conditions are: heat up to 850℃ at a rate of 180℃ / h and then hold at that temperature for 6 hours.

[0070] The pre-calcined powder was subjected to a second ball milling process. A polyurethane ball milling jar was used, zirconium balls were used as the milling media, and anhydrous ethanol was used as the milling solvent. The mass ratio of milling media, pre-calcined powder, and anhydrous ethanol was 100:40:40, and the milling time was 12 hours. After the second ball milling, the powder was baked at 80℃ for 5 hours and then passed through an 80-mesh sieve.

[0071] After drying, the powder is granulated. A 4% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder added is 15% of the mass of the dried powder.

[0072] After granulation, the material is pressed into tablets at 120 MPa for 5 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0073] The sintering process is as follows: heat up to 600℃ at 5℃ / min and hold for 2 hours, then heat up to 1150℃ at 3℃ / min and hold for 4 hours, and then cool to room temperature with the furnace.

[0074] The XRD pattern of the lead-free pyroelectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2 As shown in (c). The sintered lead-free pyroelectric ceramic material was polished to 0.3 mm, silver paste was screen-printed, dried, and held at 600℃ for 20 minutes. After polarization with a DC voltage of 4.5 kV / mm at room temperature for 30 minutes, the pyroelectric coefficient of the sample was tested as follows. Figure 3 As shown.

[0075] Example 4:

[0076] This embodiment provides a lead-free pyroelectric ceramic material with a high depolarization temperature, whose chemical composition is: 0.99Bi 0.4 Na 0.6 TiO3-0.01BaTiO3 is prepared by the following method:

[0077] (1) Weigh 90.192g of Bi2O3, 31.507g of Na2CO3, 80.026g of TiO2 and 1.978g of BaCO3 powder raw materials according to the stoichiometric ratio of 1mol of lead-free pyroelectric ceramic material.

[0078] (2) The raw materials are ball-milled and mixed using a wet ball milling process to obtain a mixed powder.

[0079] The ball milling jar is a 500ml polyurethane ball milling jar, the ball milling media is zirconium balls, the ball milling solvent is anhydrous ethanol, the mass ratio of ball milling media, raw material and anhydrous ethanol is 100:40:40, and the ball milling time is 12h.

[0080] (3) The resulting mixed powder is baked at 80°C for 5 hours, passed through an 80-mesh sieve, and the sieve material is pre-burned.

[0081] The preheating conditions are: heat up to 850℃ at a rate of 180℃ / h and then hold at that temperature for 6 hours.

[0082] The pre-calcined powder was subjected to a second ball milling process. A polyurethane ball milling jar was used, zirconium balls were used as the milling media, and anhydrous ethanol was used as the milling solvent. The mass ratio of milling media, pre-calcined powder, and anhydrous ethanol was 100:40:40, and the milling time was 12 hours. After the second ball milling, the powder was baked at 80℃ for 5 hours and then passed through an 80-mesh sieve.

[0083] After drying, the powder is granulated. A 4% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder added is 15% of the mass of the dried powder.

[0084] After granulation, the material is pressed into tablets at 120 MPa for 5 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0085] The sintering process is as follows: heat up to 600℃ at 5℃ / min and hold for 2 hours, then heat up to 1150℃ at 3℃ / min and hold for 4 hours, and then cool to room temperature with the furnace.

[0086] The XRD pattern of the lead-free pyroelectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2 As shown in (d), the sintered lead-free pyroelectric ceramic material was polished to 0.3 mm, silver paste was screen-printed, dried, and held at 600℃ for 20 minutes. After polarization with a DC voltage of 4.5 kV / mm at room temperature for 30 minutes, the pyroelectric coefficient of the sample was tested as follows. Figure 3 As shown.

[0087] Example 5:

[0088] This embodiment provides a lead-free pyroelectric ceramic material with a high depolarization temperature, whose chemical composition is: 0.99-0.99Bi. 0.47 Na 0.6 TiO3-0.01BaTiO3 is prepared by the following method:

[0089] (1) Weigh 109.500g of Bi2O3, 31.507g of Na2CO3, 80.026g of TiO2 and 1.978g of BaCO3 powder raw materials according to the stoichiometric ratio of 1mol of lead-free pyroelectric ceramic material.

[0090] (2) The raw materials are ball-milled and mixed using a wet ball milling process to obtain a mixed powder.

[0091] The ball milling jar is a 500ml polyurethane ball milling jar, the ball milling media is zirconium balls, the ball milling solvent is anhydrous ethanol, the mass ratio of ball milling media, raw material and anhydrous ethanol is 100:40:40, and the ball milling time is 12h.

[0092] (3) The resulting mixed powder is baked at 80°C for 5 hours, passed through an 80-mesh sieve, and the sieve material is pre-burned.

[0093] The preheating conditions are: heat up to 850℃ at a rate of 180℃ / h and then hold at that temperature for 6 hours.

[0094] The pre-calcined powder was subjected to a second ball milling process. A polyurethane ball milling jar was used, zirconium balls were used as the milling media, and anhydrous ethanol was used as the milling solvent. The mass ratio of milling media, pre-calcined powder, and anhydrous ethanol was 100:40:40, and the milling time was 12 hours. After the second ball milling, the powder was baked at 80℃ for 5 hours and then passed through an 80-mesh sieve.

[0095] After drying, the powder is granulated. A 4% (w / w) polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder added is 15% of the mass of the dried powder.

[0096] After granulation, the material is pressed into tablets at 120 MPa for 5 minutes, followed by sintering to obtain the lead-free pyroelectric ceramic material.

[0097] The sintering process is as follows: heat up to 600℃ at 5℃ / min and hold for 2 hours, then heat up to 1150℃ at 3℃ / min and hold for 4 hours, and then cool to room temperature with the furnace.

[0098] The XRD pattern of the lead-free pyroelectric ceramic material prepared in this embodiment is as follows: Figure 1 As shown, the SEM image is as follows: Figure 2 As shown in (e). The sintered lead-free pyroelectric ceramic material was polished to 0.3 mm, silver paste was screen-printed, dried, and held at 600℃ for 20 minutes. After polarization with a DC voltage of 4.5 kV / mm at room temperature for 30 minutes, the pyroelectric coefficient of the sample was tested as follows. Figure 3 As shown.

[0099] Depend on Figure 1 As can be seen from the XRD diagram, the lead-free pyroelectric ceramic materials provided by this invention are all pure perovskite phases.

[0100] Figure 2 The SEM images show that the lead-free pyroelectric ceramic material provided by the present invention has uniform grain size, clear grain boundaries, and good crystallinity; and the grain size of the pyroelectric ceramic decreases significantly with the change of Bi / Na ratio.

[0101] Figure 3 The pyroelectric coefficient curve of the lead-free pyroelectric ceramic shows that as the Bi / Na ratio changes, 0.99Bi x Na y The depolarization temperature of TiO3-0.01BaTiO3 ceramics is increased, as is the room-temperature pyroelectric coefficient; overall, when x / y = 0.49 / 0.55, 0.99Bi 0.49 Na 0.55 TiO3-0.01BaTiO3 ceramic exhibits the best pyroelectric properties, with a room-temperature pyroelectric coefficient of 17.71 × 10⁻⁶. -4 C m -2 K -1 Its depolarization temperature is 240℃, and its pyroelectric coefficient is greater than 17×10 at 25-30℃. -4 C m -2 K -1 .

[0102] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A lead-free pyroelectric ceramic material with high depolarization temperature, characterized in that: The chemical composition of the lead-free pyroelectric ceramic material is: 0.99Bi. x Na y TiO3-0.01BaTiO3; where x and y are molar percentages, and x / y = (0.4-0.5) / (0.55-0.6).

2. The lead-free pyroelectric ceramic material with high depolarization temperature as described in claim 1, characterized in that: The x / y values ​​are 0.45 / 0.55, 0.49 / 0.55, 0.4 / 0.6, or 0.47 / 0.

6.

3. The method for preparing the lead-free pyroelectric ceramic material according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Weigh out Bi2O3, Na2CO3, TiO2, and BaCO3 raw materials according to the stoichiometric ratio of lead-free pyroelectric ceramic materials; (2) The raw materials are ball-milled and mixed to obtain a mixed powder; (3) The obtained mixed powder is successively dried, sieved, pre-fired, ball-milled twice, dried, granulated, pressed into tablets and sintered to obtain the lead-free pyroelectric ceramic material.

4. The method for preparing the lead-free pyroelectric ceramic material as described in claim 3, characterized in that, The ball milling conditions in steps (2) and (3) are as follows: a polyurethane ball milling jar is used, zirconium balls are used as the ball milling medium, and anhydrous ethanol is used as the ball milling solvent for ball milling and mixing.

5. The method for preparing the lead-free pyroelectric ceramic material as described in claim 4, characterized in that: In step (2), the mass ratio of raw material to ball milling solvent during ball milling is 1:0.8-1:1.2, and the ball milling time is 10-12h. In step (3), the mass ratio of pre-calcined powder to ball milling solvent during secondary ball milling is 1:0.6-1:0.8, and the ball milling time is 10-12h.

6. The method for preparing the lead-free pyroelectric ceramic material as described in claim 3, characterized in that, The preheating conditions in step (3) are: heating to 850-900℃ at 180℃ / h and then holding for 4-6 hours.

7. The method for preparing the lead-free pyroelectric ceramic material as described in claim 3, characterized in that, In step (3), a polyvinyl alcohol aqueous solution with a mass fraction of 3-5% is used as a binder for granulation; the amount of binder added is 10-20% of the mass of the dried powder.

8. The method for preparing the lead-free pyroelectric ceramic material as described in claim 3, characterized in that, The tableting conditions in step (3) are: holding pressure at 100-150 MPa for 4-6 minutes.

9. The method for preparing lead-free pyroelectric ceramic material as described in claim 3, characterized in that, The sintering process in step (3) is as follows: heat up to 550-600℃ at 5℃ / min and hold for 1.5-2h, then heat up to 1140-1160℃ at 3℃ / min and hold for 2-4h, and then cool to room temperature with the furnace.

10. The application of the lead-free pyroelectric ceramic material as described in any one of claims 1-2 in uncooled infrared detectors.

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