A pyroelectric sensor system combined with a thermoelectric refrigeration device and a preparation method thereof

Abstract

The present invention belongs to the field of infrared sensor technology, and in particular to a pyroelectric sensor system combined with a thermoelectric cooling device and a preparation method thereof, wherein the pyroelectric sensor system comprises a pyroelectric sensor, a thermoelectric cooling device, and an aluminum heat sink, and the pyroelectric sensor is composed of a tube cap, a lens, a pyroelectric ceramic sensitive element, a circuit board, a base, a conductive gasket, a signal processing chip, and a pin, and the pyroelectric ceramic sensitive element is made of a lead-free pyroelectric ceramic material 0.99 (99.7% Na 0.5 Bi 0.5 TiO3‑0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3 was polarized. Compared with BNT-NBT, the BNT-NBT-Mn of the present invention has a higher room temperature pyroelectric coefficient of 7.58×10 ‑4 Cm ‑2 K ‑1 and a depolarization temperature of 182°C; and successfully prepared a pyroelectric sensor, whose response rate and detection rate can meet the application requirements; on this basis, continuous monitoring of the pyroelectric sensor was achieved by using temperature control of a thermoelectric cooler.

Description

Technical Field

[0001] The present invention belongs to the technical field of infrared sensors, and in particular relates to a pyroelectric sensor system combined with a thermoelectric refrigeration device and a preparation method thereof. Background Art

[0002] The pyroelectric effect refers to the charge release phenomenon in which the spontaneous polarization intensity of the pyroelectric material changes with the change of the ambient temperature. Sensors based on the pyroelectric effect have been commercially applied, in which pyroelectric materials are the core sensitive elements. The effectiveness of pyroelectric sensors depends on the inherent properties of the pyroelectric materials used, which in turn are determined by the size of the pyroelectric coefficient. In addition, the detection figure of merit also directly reflects the performance and potential of pyroelectric materials in the field of infrared detection. In order to improve the detection rate of pyroelectric materials, it is necessary to consider increasing the pyroelectric coefficient at room temperature while reducing the dielectric constant and dielectric loss of the material. In addition to the parameters of the pyroelectric coefficient and the detection figure of merit, the depolarization temperature of the pyroelectric material is also very important, which determines the temperature range for stable operation of the device.

[0003] The most widely used intrinsic pyroelectric materials are lead-based ceramics, such as lead zirconate titanate (PZT). However, these materials contain a large amount of lead, which is very harmful to the living environment and human health. Therefore, lead-free pyroelectric ceramics need to be developed, among which Na 0.5 Bi 0.5 TiO3(BNT) based ceramics have a large room temperature pyroelectric coefficient (2.80×10 -4 Cm -2 K -1 ), large remnant polarization strength (37μCcm -2 ) and high Curie temperature (325℃), it is considered to be one of the lead-free thermoelectric ceramics that are promising to replace lead-based materials. BNT-based ceramics can optimize pyroelectric properties by constructing morphotropic phase boundaries (MPBs) and relaxation phase transitions or combining with high thermal conductivity materials. However, despite the great improvement in the pyroelectric properties of the materials, there are few reports on pyroelectric sensors made of BNT-based ceramics. At the same time, pyroelectric sensors are insensitive to static temperature conditions and only respond to temperature changes. Therefore, several methods have been proposed to achieve continuous detection through devices, such as optical choppers, scanning mirrors, etc. However, the above systems require mechanical components, which makes them large, heavy and expensive. There is an urgent need to find a new method to achieve continuous detection. Thermoelectric cooling technology is a common cooling method that can effectively cope with changes in external temperature without mechanical components. Therefore, the local temperature of the pyroelectric sensor can be regulated by a thermoelectric cooler. This temperature modulation activates the pyroelectric sensor, thereby facilitating the generation of electrical signals. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a pyroelectric sensor system combined with a thermoelectric refrigeration device, which can achieve continuous detection under a constant temperature state and improve stability and sensitivity, and has the advantages of simple preparation and low cost.

[0005] To this end, based on the inventor's prior work (CN114133239B), after further research and development, the first aspect of the present invention provides a lead-free pyroelectric ceramic material, the chemical composition of the lead-free pyroelectric ceramic material is: 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3, or 0.99(99%Na 0.5 Bi 0.5 TiO3-1%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3, wherein 99.7%, 0.3%, and 1% are molar percentages, and 0.99 and 0.01 are molar ratios.

[0006] The second aspect of the present invention provides a method for preparing the lead-free pyroelectric ceramic material, the method comprising the following steps:

[0007] Step 1: According to the lead-free pyroelectric ceramic material 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3 or 0.99(99%Na 0.5 Bi 0.5 TiO3-1%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3 stoichiometric ratio weigh Bi2O3, Na2CO3, TiO2, MnCO3 raw materials;

[0008] Step 2, ball milling the raw materials to obtain a mixed powder, the specific process is: using a polyurethane ball mill, using zirconium balls as the ball milling medium, and anhydrous ethanol as the ball milling solvent for ball milling mixing, wherein the mass ratio of the raw materials to anhydrous ethanol is (1:0.8)-(1:1.2), and the ball milling time is 12-24h;

[0009] Step 3, drying, sieving, pre-calcining, secondary ball milling, drying, granulating, tableting, and sintering the mixed powder in sequence to obtain the lead-free pyroelectric ceramic material; wherein the drying conditions are: drying at 60-100°C for 10-12h; the sieving conditions are: passing through a 60-100 mesh sieve; the pre-calcining conditions are: heating to 850-900°C at 200°C / h and then keeping warm for 2-4h; the secondary ball milling conditions are: using zirconium balls as ball milling media, anhydrous ethanol as ball milling solvent, the mass ratio of the pre-calcined powder to the ball milling solvent is (1:0.6)-(1:0.8), and the ball milling time is 10 -12h; the granulation conditions are: using a polyvinyl alcohol aqueous solution with a mass fraction of 3%-5% as a binder, and the amount of the binder added is 10%-20% of the mass of the powder after drying; the tableting conditions are: maintaining a pressure of 3-5min at 15-20Mpa; the sintering conditions are: heating to 550-600℃ at 2.5℃ / min and keeping it for 1-2h, then heating to 1160-1180℃ at 2.5℃ / min and keeping it for 2-4h, then cooling to 850-900℃ at 2.5℃ / min and keeping it for 0.5-1h, and finally cooling naturally to room temperature.

[0010] The third aspect of the present invention provides a pyroelectric sensor, which includes a tube cap, a lens, a pyroelectric ceramic sensitive element, a circuit board, a base, a conductive gasket, a signal processing chip and a pin; and a preparation method thereof includes the following steps:

[0011] Step 1, grinding the obtained lead-free pyroelectric ceramic material to a thickness of 0.3 mm, then screen-printing the upper and lower surfaces of the ground lead-free pyroelectric ceramic material with silver paste, drying, and placing it in a muffle furnace at 750° C. for 10 minutes, wherein the silver paste forms an electrode; after taking it out, applying a DC voltage of 7 kV / mm for polarization at room temperature for 20 minutes;

[0012] Step 2: grind the lead-free pyroelectric ceramic material polarized in step 1 to a thickness of 80-100 μm, and cut it into 20 mm×20 mm pyroelectric ceramic sensitive elements using a dicing machine;

[0013] Step 3, fix the circuit board on the upper surface of the base, and then fix the signal processing chip on the circuit board, so that the signal processing chip is electrically connected to the circuit board; then fix the pyroelectric ceramic sensitive element on the circuit board through the conductive gasket, so that the pyroelectric ceramic sensitive element is fixed on the upper surface of the conductive gasket, so that the pyroelectric ceramic sensitive element is located on the upper layer of the signal processing chip, forms a stacked structure with the signal processing chip, and is electrically connected to the signal processing chip; there are two conductive gaskets, which are fixed on the circuit board and respectively arranged on both sides of the signal processing chip, and the pyroelectric ceramic sensitive element is bridged on the two conductive gaskets; the mounting pins are fixed at the lower end of the base, so that the pins are electrically connected to the signal processing chip through the circuit board; the tube cap with a lens is assembled on the base, so that the tube cap covers the pyroelectric ceramic sensing element and the circuit board, and the lens is located directly above the pyroelectric ceramic sensitive element, so that the fixed infrared radiation can be effectively radiated to the pyroelectric ceramic sensitive element, and the pyroelectric sensor is obtained.

[0014] A fourth aspect of the present invention provides a pyroelectric sensor system combined with a thermoelectric cooling device. The preparation method of the pyroelectric sensor system comprises the following steps:

[0015] The prepared pyroelectric sensor was electrically connected to a 3cm×3cm thermoelectric cooling device, which was a commercially available device. The hot end of the thermoelectric cooling device was connected to an aluminum heat sink, and the cold end of the thermoelectric cooling device was connected to the pyroelectric sensor.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] The lead-free pyroelectric ceramic provided by the present invention effectively reduces leakage current by doping MnCO3, and enhances ferroelectricity, piezoelectricity and pyroelectricity. At the same time, the generated oxygen vacancies accumulate at the domain wall, affecting the movement of the domain wall, thereby reducing dielectric loss. Based on this, compared with BNT-NBT, BNT-NBT-Mn has a higher room temperature pyroelectric coefficient of 7.58×10 -4 Cm -2 K -1 and a depolarization temperature of 182°C; a pyroelectric sensor was successfully prepared using BNT-NBT-Mn ceramics, and the response rate and detection rate of the sensor can meet the application requirements; continuous monitoring of the pyroelectric sensor was achieved by using temperature control of a thermoelectric cooling device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The pyroelectric coefficient diagram of the lead-free pyroelectric ceramic material in Examples 1-3 of the present invention;

[0019] Figure 2Schematic diagram of XRD of the lead-free pyroelectric ceramic material in Example 1 and Example 2 of the present invention;

[0020] Figure 3 The SEM images of the lead-free pyroelectric ceramic materials in Examples 1 and 2 of the present invention;

[0021] Figure 4 is a perspective schematic diagram of a pyroelectric sensor according to an embodiment of the present invention;

[0022] Figure 5 Schematic diagram of a pyroelectric sensor system combined with a thermoelectric cooling device in an embodiment of the present invention, wherein FIG (a) is a pyroelectric sensor, FIG (b) is a thermoelectric cooling device, FIG (c) is a pyroelectric sensor system combined with a thermoelectric cooling device, and FIG (d) is a structural schematic diagram of a pyroelectric sensor system combined with a thermoelectric cooling device;

[0023] Figure 6 1 is a voltage performance diagram of a pyroelectric sensor system combined with a thermoelectric cooling device in an embodiment of the present invention.

[0024] Figure 7 The dielectric constant and dielectric loss of the lead-free pyroelectric ceramic material of Example 1 of the present invention at room temperature;

[0025] Figure 8 is the voltage response (R v ) and specific detection rate (D * ). DETAILED DESCRIPTION

[0026] The technical scheme in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art 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 limited by the attached claims and their equivalents.

[0027] The lead-free pyroelectric ceramic material of the present invention and the device based thereon are described in detail below through specific embodiments.

[0028] Example 1

[0029] This embodiment provides a lead-free pyroelectric ceramic material, the chemical composition of which is: 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O15 )-0.01MnCO3, prepared by the following method:

[0030] (1) Weigh 119.286 g of Bi2O3, 26.259 g of Na2CO3, 79.943 g of TiO2, and 1.150 g of MnCO3 as raw materials;

[0031] (2) using a 500 ml polyurethane ball mill to wet-mill the raw materials, the milling medium is zirconium balls, the milling solvent is anhydrous ethanol, the mass ratio of the milling medium, the raw materials, and anhydrous ethanol is 100:40:40, and the milling time is 12 h to obtain a mixed powder;

[0032] (3) The mixed powder was dried at 80°C for 12 hours and then passed through a 100-mesh sieve. The sieved powder was placed in a muffle furnace and heated to 850°C at 200°C / h for pre-calcination for 2 hours. The pre-calcined powder was secondary ball-milled in a polyurethane ball mill using zirconium balls as ball milling media and anhydrous ethanol as ball milling solvent. The mass ratio of the pre-calcined powder to the ball milling solvent was 1:0.6, and the ball milling time was 12 hours to obtain ceramic powder; the ceramic powder was dried at 80°C for 12 hours, passed through a 100-mesh sieve, and 5% by mass polyvinyl alcohol (model 1788, the same below, not repeated) was used. The solution is used as a binder for granulation, and the amount of the binder added is 20% of the mass of the ceramic powder. After granulation, it is pressed into tablets. The pressing condition is to maintain the pressure at 15Mpa for 3 minutes, and then put it into a muffle furnace for sintering. The specific sintering process is: heating to 600℃ at 2.5℃ / min and keeping it for 1h, then heating to 1160℃ at 2.5℃ / min and keeping it for 4h, then cooling to 850℃ at 2.5℃ / min and keeping it for 0.5h, and finally naturally cooling to room temperature (25℃, the same below) to obtain the lead-free pyroelectric ceramic material, named sample-1.

[0033] The obtained sample-1 was polished to a thickness of 0.3 mm, and then the polished sample-1 was screen-printed on its upper and lower surfaces with high-temperature silver paste, dried, and placed in a muffle furnace at 750° C. for 10 minutes, and the silver paste formed an electrode; after being taken out, a DC voltage of 7 kV / mm was applied at room temperature for polarization for 20 minutes, and the pyroelectric coefficient of the sample was tested as follows: Figure 1 As shown, compared with the inventor’s authorized prior work (ZL202111271379.6), the pyroelectric coefficient is increased from 5.28×10 -4 Cm -2 K -1 Increased to 7.58×10 -4 Cm -2 K -1 The XRD pattern of the sample obtained in Example 1 is as follows: Figure 2 As shown in the SEM images Figure 3 (a) shown.

[0034] Example 2

[0035] This embodiment provides a lead-free pyroelectric ceramic material, the chemical composition of which is: 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3, prepared by the following method:

[0036] (1) Weigh 119.286 g of Bi2O3, 26.259 g of Na2CO3, 79.943 g of TiO2, and 1.150 g of MnCO3 as raw materials;

[0037] (2) using a 500 ml polyurethane ball mill to wet-mill the raw materials, the milling medium is zirconium balls, the milling solvent is anhydrous ethanol, the mass ratio of the milling medium, the raw materials, and anhydrous ethanol is 100:40:40, and the milling time is 12 h to obtain a mixed powder;

[0038] (3) The mixed powder was dried at 80°C for 12 hours and then passed through a 100-mesh sieve. The sieved powder was placed in a muffle furnace and heated to 850°C at 200°C / h for pre-calcination for 2 hours. The pre-calcined powder was secondary ball-milled in a polyurethane ball mill using zirconium balls as ball milling media and anhydrous ethanol as ball milling solvent. The mass ratio of the pre-calcined powder to the ball milling solvent was 1:0.6, and the ball milling time was 12 hours to obtain ceramic powder. The ceramic powder was dried at 80°C for 12 hours and passed through a 100-mesh sieve. A 5% polyvinyl alcohol aqueous solution was used as a binder for granulation. The amount of binder added was 20% of the mass of the ceramic powder. After granulation, the tablet was pressed. The tablet pressing condition was 15 MPa and the pressure was maintained for 3 minutes. Then, the solution was placed in a muffle furnace for sintering. The specific sintering process was: heating to 600°C at 2.5°C / min and keeping warm for 1 hour. Then, heating to 1160°C at 2.5°C / min and keeping warm for 0.5 hour. Then, the solution was naturally cooled to room temperature to obtain sample 2.

[0039] The obtained sample-2 was polished to a thickness of 0.3 mm, and then the upper and lower surfaces of the polished sample-2 were screen-printed with high-temperature silver paste, dried, and placed in a muffle furnace at 750° C. for 10 min, and the silver paste formed an electrode; after being taken out, a DC voltage of 7 kV / mm was applied at room temperature for polarization for 20 min, and the pyroelectric coefficient of the prepared sample was tested as follows: Figure 1 As shown, in this embodiment 2, a one-step sintering method is used as a comparison with embodiment 1. It can be seen that the pyroelectric coefficient and depolarization temperature of the lead-free pyroelectric ceramic both show a downward trend. The XRD spectrum of the obtained sample is as follows: Figure 2 As shown in the SEM images Figure 3(b) as shown.

[0040] Example 3

[0041] This embodiment provides a lead-free pyroelectric ceramic material, the chemical composition of which is: 0.99 (99% Na 0.5 Bi 0.5 TiO3-1%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3, which is prepared by the following method:

[0042] (1) Weigh 125.816 g of Bi2O3, 26.259 g of Na2CO3, 81.606 g of TiO2, and 1.150 g of MnCO3 as raw materials;

[0043] (2) using a 500 ml polyurethane ball mill to wet-mill the raw materials, the milling medium is zirconium balls, the milling solvent is anhydrous ethanol, the mass ratio of the milling medium, the raw materials, and anhydrous ethanol is 100:40:40, and the milling time is 12 h to obtain a mixed powder;

[0044] (3) The mixed powder was dried at 80°C for 12 hours and then passed through a 100-mesh sieve. The sieved powder was placed in a muffle furnace and heated to 850°C at 200°C / h for pre-calcination for 2 hours. The pre-calcined powder was subjected to secondary ball milling in a polyurethane ball mill using zirconium balls as ball milling media and anhydrous ethanol as ball milling solvent. The mass ratio of the pre-calcined powder to the ball milling solvent was 1:0.6, and the ball milling time was 12 hours to obtain ceramic powder. The ceramic powder was dried at 80°C for 12 hours, passed through a 100-mesh sieve, and 5% by mass polyethylene was used. The enol aqueous solution was used as a binder for granulation, and the amount of the binder added was 20% of the mass of the ceramic powder. After granulation, the tablets were pressed under a pressure of 15 MPa for 3 minutes, and then placed in a muffle furnace for sintering. The specific sintering process was: heating to 600°C at 2.5°C / min and keeping warm for 1 hour, then heating to 1160°C at 2.5°C / min and keeping warm for 4 hours, then cooling to 850°C at 2.5°C / min and keeping warm for 0.5 hours, and finally naturally cooling to room temperature to obtain sample-3.

[0045] Sample-3 was polished to a thickness of 0.3 mm, and then the upper and lower surfaces of the polished sample-3 were screen-printed with high-temperature silver paste, dried, and placed in a muffle furnace at 750°C for 10 minutes to form electrodes with the silver paste; after being taken out, a DC voltage of 7 kV / mm was applied at room temperature for 20 minutes to polarize the sample, and the pyroelectric coefficient of the sample was tested as follows: Figure 1 As shown, in Example 3, 1% Na 0.5 Bi 4.5 Ti4O 15By comparison, it can be seen that the pyroelectric coefficient and depolarization temperature of sample-3 are still within the optimal range; at the same time, compared with the prior work authorized by the inventor (ZL202111271379.6), it can be seen from Examples 1-3 that the introduction of MnCO3 can improve the pyroelectric properties of lead-free pyroelectric ceramic samples of different proportions.

[0046] Example Preparation of pyroelectric sensor

[0047] This embodiment provides a pyroelectric sensor, which includes a tube cap, a lens, a pyroelectric ceramic sensitive element, a circuit board, a base, two conductive pads, a signal processing chip and pins. The preparation method of the pyroelectric sensor includes the following steps:

[0048] The circuit board is fixed on the upper surface of the base, and then the signal processing chip is fixed on the circuit board, so that the signal processing chip is electrically connected to the circuit board; the polarized sample-1 is polished to a thickness of 80-100 μm and cut into 20 mm×20 mm pyroelectric ceramic sensitive elements using a dicing machine, two conductive gaskets are arranged on both sides of the signal processing chip and fixed on the circuit board, and the pyroelectric ceramic sensitive element is bridged on the two conductive gaskets, so that the pyroelectric ceramic sensitive element is located on the upper layer of the signal processing chip, forms a stacked structure with the signal processing chip, and is electrically connected to the signal processing chip; the mounting pins are fixed at the lower end of the base, so that the pins are electrically connected to the signal processing chip through the circuit board; a tube cap with a lens is assembled on the base, so that the tube cap covers the pyroelectric ceramic sensing element and the circuit board, and the lens is located directly above the pyroelectric ceramic sensitive element, so as to ensure that the fixed infrared radiation can be effectively radiated to the pyroelectric ceramic sensitive element, so as to obtain the pyroelectric sensor.

[0049] The connection method of the above-mentioned tube cap, lens, pyroelectric ceramic sensitive element, circuit board, base, conductive gasket, signal processing chip and pins of the pyroelectric sensor is as follows: Figure 4 shown.

[0050] Embodiments Pyroelectric sensor system combined with thermoelectric cooling device

[0051] This embodiment provides a method for preparing a pyroelectric sensor system combined with a thermoelectric cooling device, comprising the following steps:

[0052] The pyroelectric sensor prepared above is electrically connected to a 3cm×3cm thermoelectric cooling device to obtain a pyroelectric sensor system combined with a thermoelectric cooling device. The thermoelectric cooling device is a commercially available device. The hot end of the thermoelectric cooling device is connected to an aluminum heat sink, and the cold end of the thermoelectric cooling device is connected to the pyroelectric sensor. Since the response of the pyroelectric sensor is highly dependent on its temperature change, the pyroelectric sensor system of this embodiment is connected to a test source meter through a relay for testing. During the test, the thermoelectric cooling device is first turned off, and the hand is placed 1 cm above the surface of the pyroelectric sensor in the pyroelectric sensor system combined with the thermoelectric cooling device of this embodiment, and the voltage signal is tested for 30-40 seconds; then, the hand is removed so that the pyroelectric sensor system is not affected by the heat of the hand, and then the thermoelectric cooling device is turned on, and the voltage signal is continuously tested for 30-40 seconds after the signal stabilizes; finally, when the thermoelectric cooling device is turned on, the hand is put back to the previous position, that is, 1 cm above the surface of the pyroelectric sensor, and the voltage signal is continuously tested for 30-40 seconds after the signal stabilizes.

[0053] The structural diagram of the pyroelectric sensor system combined with the thermoelectric cooling device is shown in Figure 5 The test results are shown in Figure 6 shown.

[0054] Depend on Figure 1 The pyroelectric coefficient curve of the lead-free pyroelectric ceramic material shows that the pyroelectric coefficient and depolarization temperature of the lead-free pyroelectric ceramic material prepared by the two-step sintering method of Example 1 at 25°C are both improved, which are 7.58×10 - 4 Cm -2 K -1 and 182°C. Depend on Figure 2 It can be seen from the XRD schematic diagram that the lead-free pyroelectric ceramic materials obtained in Example 1 and Example 2 are both pure perovskite phase. Figure 3 The SEM images show that the lead-free pyroelectric ceramic material prepared in Example 1 (a) has a larger grain size, mainly large-sized grains, and the lead-free pyroelectric ceramic material prepared in Example 2 (b) has a smaller grain size, mainly small-sized grains. Relatively speaking, the grain boundary density in the product obtained in Example 2 is larger, and the lead-free pyroelectric ceramic materials prepared in Examples 1 and 2 have clear grain boundaries and good crystallinity. In addition, the two-step sintering method in Example 1 increases the pores between the grains in the lead-free pyroelectric ceramic material.

[0055] Figure 5 This is a schematic diagram of the appearance of a pyroelectric sensor system combined with a thermoelectric cooling device, in which the hot end of the thermoelectric cooling device is connected to an aluminum heat sink, and the cold end of the thermoelectric cooling device is connected to a pyroelectric sensor. It can be seen that the device is small in size and easy to assemble. Figure 6is the test signal of the pyroelectric sensor system, and the output voltage is tested based on the pyroelectric effect in response to temperature changes. When the thermoelectric cooling device is turned off and a person's hand is close to the pyroelectric sensor, a voltage of 0.75V can be obtained when it is stable; when the person's hand is removed and the thermoelectric cooling device is turned on at the same time, the temperature of the pyroelectric sensor drops due to being at the cold end of the thermoelectric cooling device, generating an opposite pyroelectric current and a voltage of -0.4V. This phenomenon shows that the thermoelectric cooling device can activate the pyroelectric sensor. Finally, when the thermoelectric cooling device is turned on and a person's hand is close to the pyroelectric sensor, a voltage of 1.12V is generated. This phenomenon may be attributed to the increase in temperature difference in the pyroelectric ceramic sensitive element. In short, the thermoelectric cooling device can realize continuous monitoring of the pyroelectric sensor, that is, the effective voltage amplitude is continuously obtained when the thermoelectric cooling device is turned on.

[0056] In summary, the lead-free pyroelectric ceramic material provided by the present invention is prepared by solid phase reaction. Appropriate doping of Mn can effectively reduce leakage current, enhance ferroelectricity, piezoelectricity and pyroelectricity. Therefore, the lead-free pyroelectric ceramic material can achieve up to 7.58×10 -4 Cm -2 K -1 The pyroelectric coefficient and depolarization temperature of 182℃ were obtained. At the same time, a low dielectric constant ε r 496 and dielectric loss tanδ is 0.021 (such as Figure 7 ), the detection rate merit is improved. The lead-free pyroelectric ceramic material of the present invention is used to successfully prepare a pyroelectric sensor, and the voltage response and specific detection rate are 1.63×10 5 VW -1 and 3.14×10 8 cmHz 1 / 2 W -1 , can meet the application requirements (such as Figure 8 ). Finally, continuous monitoring of the pyroelectric sensor was achieved by using a thermoelectric cooling device to control the temperature.

[0057] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A pyroelectric sensor system combined with a thermoelectric cooling device, the pyroelectric sensor system comprising a pyroelectric sensor, a thermoelectric cooling device, and an aluminum heat sink, characterized in that: The preparation method of the pyroelectric sensor system comprises the following steps: The pyroelectric sensor is electrically connected to a thermoelectric cooling device; the hot end of the thermoelectric cooling device is connected to an aluminum heat sink, and the cold end of the thermoelectric cooling device is connected to the pyroelectric sensor; The pyroelectric sensor comprises a tube cap, a lens, a pyroelectric ceramic sensitive element, a circuit board, a base, a conductive gasket, a signal processing chip, and a pin; the preparation method of the pyroelectric sensor comprises the following steps: Step 1, grinding the lead-free pyroelectric ceramic material to a suitable thickness, then screen-printing the upper and lower surfaces of the ground lead-free pyroelectric ceramic material with silver paste, drying, and placing it in a muffle furnace for heat treatment, wherein the silver paste forms an electrode; after taking it out, applying a DC voltage for polarization at room temperature; Step 2, grinding the lead-free pyroelectric ceramic material polarized in step 1 to a thickness of 80-100 μm, and cutting it into block-shaped pyroelectric ceramic sensitive elements using a dicing machine; Step 3, fix the circuit board on the upper surface of the base, and then fix the signal processing chip on the circuit board, so that the signal processing chip is electrically connected to the circuit board; then fix the pyroelectric ceramic sensitive element on the circuit board through the conductive gasket, so that the pyroelectric ceramic sensitive element is fixed on the upper surface of the conductive gasket, so that the pyroelectric ceramic sensitive element is located on the upper layer of the signal processing chip, forms a stacked structure with the signal processing chip, and is electrically connected to the signal processing chip; there are two conductive gaskets, which are fixed on the circuit board and respectively arranged on both sides of the signal processing chip, and the pyroelectric ceramic sensitive element is bridged on the two conductive gaskets; fix the mounting pins at the lower end of the base, so that the pins are electrically connected to the signal processing chip through the circuit board; assemble the tube cap with a lens on the base, so that the tube cap covers the pyroelectric ceramic sensing element and the circuit board, and the lens is located directly above the pyroelectric ceramic sensitive element, so that the fixed infrared radiation can be effectively radiated to the pyroelectric ceramic sensitive element, that is, the pyroelectric sensor is obtained; The chemical composition of the lead-free pyroelectric ceramic material is: 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3, or 0.99(99%Na 0.5 Bi 0.5 TiO3-1%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3; The preparation method of the lead-free pyroelectric ceramic material comprises the following steps: Step (1), according to the lead-free pyroelectric ceramic material 0.99 (99.7% Na 0.5 Bi 0.5 TiO3-0.3%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3 or 0.99(99%Na 0.5 Bi 0.5 TiO3-1%Na 0.5 Bi 4.5 Ti4O 15 )-0.01MnCO3 stoichiometric ratio weigh Bi2O3, Na2CO3, TiO2, MnCO3 raw materials; Step (2), ball milling the raw materials to obtain a mixed powder, the specific process is: using a polyurethane ball mill, using zirconium balls as the ball milling medium, and anhydrous ethanol as the ball milling solvent to perform ball milling, wherein the mass ratio of the raw materials to the anhydrous ethanol is 1:0.8-1:1.2, and the ball milling time is 12-24 hours; Step (3), drying, sieving, pre-calcining, secondary ball milling, drying, granulating, tableting, and sintering the mixed powder in sequence to obtain the lead-free pyroelectric ceramic material; wherein the drying conditions are: drying at 60-100°C for 10-12h; the sieving conditions are: passing through a 60-100 mesh sieve; the pre-calcining conditions are: heating to 850-900°C at 200°C / h and then keeping warm for 2-4h; the secondary ball milling conditions are: using zirconium balls as ball milling media, anhydrous ethanol as ball milling solvent, the mass ratio of the pre-calcined powder to the ball milling solvent is 1:0.6-1:0.8, and the ball milling time is 10 -12h; the granulation conditions are: using a polyvinyl alcohol aqueous solution with a mass fraction of 3-5% as a binder, and the amount of the binder added is 10%-20% of the mass of the powder after drying; the tableting conditions are: maintaining the pressure at 15-20Mpa for 3-5min; the sintering conditions are: heating to 550-600℃ at 2.5℃ / min and keeping it for 1-2h, then heating to 1160-1180℃ at 2.5℃ / min and keeping it for 2-4h, then cooling to 850-900℃ at 2.5℃ / min and keeping it for 0.5-1h, and finally cooling naturally to room temperature.

2. The pyroelectric sensor system according to claim 1, characterized in that: The dimensions of the pyroelectric ceramic sensitive element are 20 mm in length and 20 mm in width.

3. The pyroelectric sensor system according to claim 1, characterized in that: The suitable thickness in step 1 is 0.3 mm, the heat treatment is to keep the temperature at 750° C. for 10 min, the DC voltage is 7 kV / mm, and the polarization time is 20 min.

4. The pyroelectric sensor system according to claim 1, characterized in that: The dimensions of the thermoelectric cooling device are 3 cm in length and 3 cm in width.

Images