High Curie temperature lead-based pyroelectric material and preparation method thereof

Abstract

The invention belongs to the technical field of pyroelectric infrared detection, and particularly relates to a high Curie temperature lead-based pyroelectric material and a preparation method thereof, the chemical composition of the high Curie temperature lead-based pyroelectric material is Pb (Zr0. 9Ti0. 1) O3-xK2CO3, and x is more than or equal to 0.0 and less than or equal to 1.5% (mol). K2CO3 is doped into a PZT substrate, K < + > enters a crystal lattice and then replaces Pb < 2 + > at an A site to form an oxygen vacancy, polarization overturning is hindered, and the dielectric constant and the dielectric loss are reduced. As the radius of K < + > is larger than that of Pb < 2 + >, lattice distortion is further intensified, the polarization characteristic of the material is improved, and the material shows high pyroelectric performance and good temperature stability. In order to avoid element volatilization and reduce the sintering cost, a microwave sintering method is adopted, and the high-Curie-temperature lead-based pyroelectric ceramic material with good consistency can be efficiently prepared at low cost through process adjustment.

Description

Technical Field

[0001] The present invention belongs to the technical field of pyroelectric infrared detection, and in particular, relates to a high Curie temperature lead-based pyroelectric material and a preparation method thereof. Background Art

[0002] In the past decade, pyroelectric materials have been widely used in infrared detectors, and they play an irreplaceable role in military, national defense, aerospace, industry, medical and daily life. With the impact of the Internet of Things and smart home, pyroelectric sensors for human body detection have been further promoted. The demand for pyroelectric infrared sensors for human body detection is large, and ceramic materials with low manufacturing cost, short cycle, high output and good pyroelectric effect are more suitable as sensitive elements.

[0003] The biggest problem faced by pyroelectric materials in application is that it is difficult to have high pyroelectric performance while ensuring low dielectric constant, small dielectric loss and high depolarization temperature. It is generally believed that materials with high pyroelectric coefficient, low dielectric constant and low dielectric loss can ensure that pyroelectric sensors have excellent signal output characteristics, fast response time and low disturbance noise. The depolarization temperature of conventional pyroelectric materials is lower than 200℃. Pyroelectric sensors undergo high temperature (260℃) process during production, causing material performance failure. Therefore, the development of pyroelectric materials with high pyroelectric performance that are compatible with production processes is urgent and of great value in engineering applications. Summary of the invention

[0004] In view of the above background, the purpose of the present invention is to provide a high Curie temperature lead-based pyroelectric material. Providing a high Curie temperature lead-based pyroelectric material is another purpose of the present invention. To achieve the purpose, the present invention adopts the following technical solutions:

[0005] A high Curie temperature lead-based pyroelectric material, the chemical composition of which is Pb(Zr0.9Ti0.1)O3-xK2CO3, wherein 0.0≤x≤1.5% (mol), and the lead-based pyroelectric material is obtained by doping K2CO3 into a PZT matrix, K+ enters the lattice to replace Pb2+ at the A position to form an oxygen vacancy, hindering polarization reversal, thereby reducing the dielectric constant and dielectric loss, and the K+ radius is larger than Pb2+, aggravating the lattice distortion, improving the material polarization characteristics, and making the material exhibit high pyroelectric performance and temperature stability.

[0006] A method for preparing a high Curie temperature lead-based pyroelectric material comprises the following steps:

[0007] Step 1: Pb source, Zr source, Ti source and K source are weighed according to the stoichiometric ratio of the ceramic components, ball-milled and dried, pre-sintered, ball-milled and dried to obtain a solid solution powder;

[0008] Step 2: The solid solution powder obtained in step 1 is mixed with a binder to form granules, and then unidirectionally pressed into a ceramic body;

[0009] Step 3: Sintering the ceramic body obtained in step 2 by microwave to obtain a bulk ceramic;

[0010] Step 4: The bulk ceramic obtained in step 3 is subjected to electrode, polarization, and mechanical processing to obtain the product.

[0011] Preferably, the stoichiometry of the ceramic components in step 1 is controlled in the range of Pb(Zr0.9Ti0.1)O3-xK2CO3, where 0.0≤x≤1.5% (mol).

[0012] Preferably, in step 1, the Pb source is PbO, the Zr source is ZrO2, and the Ti source is TiO2, wherein the purity of the PbO, ZrO2, and TiO2 raw materials is higher than 99.5%, and the K source is K2CO3 with a purity higher than 99.00%. All raw materials are baked at 200°C for 1h before weighing to prevent moisture, and then ball milled and dried.

[0013] Preferably, the pre-sintering process described in step 1 requires that the powder be screened and then loaded into a crucible for compaction, open pre-sintering, the temperature be controlled at 800-850° C., the holding time be 2-3 h, and after sintering, ball milling and drying are performed to obtain a solid solution powder.

[0014] Preferably, the adhesive in step 2 is a 1wt% PVA aqueous solution, the amount of the PVA aqueous solution added is 8-10% of the mass of the powder, and after granulation, it is sieved through a 120-mesh sieve and aged in an oven at a temperature of 70-80°C.

[0015] Preferably, the molding described in step 2 is to press the solid solution powder into a cylindrical green embryo, using a cold press of 100-150Mpa for 2-5 minutes.

[0016] Preferably, the ceramic embryo body described in step 2 is a green embryo, and the diameter to thickness ratio of the cylindrical green embryo is controlled to be between 1-3.

[0017] Preferably, the microwave sintering described in step 3 is to place the ceramic body after debinding into a microwave workstation, raise the temperature to 1000-1100°C at a heating rate of 20-30°C / min, and keep the temperature for 20-40 minutes to obtain a ceramic block.

[0018] Preferably, the polarization process described in step 4 is to polarize the ceramic block of the completed electrode in an oil bath at 80° C. using an electric field of 6-7 kV / mm for 20-30 minutes, and then mechanically process it after standing for 24 hours.

[0019] Preferably, the product obtained in step 4 is subjected to performance testing. Specifically, under the test conditions of room temperature and 1kHz, the relative dielectric constant is 419-539, the dielectric loss is 0.0121-0.0168, and the pyroelectric coefficient is (1.5-2.8)

[0020] ×10-4C m-2K-1, and its depolarization temperature Td is 274-280℃.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This application provides a design of a high Curie temperature lead-based pyroelectric material component, which is obtained by doping K into the PZT matrix. 2 CO 3 , K + After entering the lattice, it replaces Pb at the A position 2+ Oxygen vacancies are formed, which hinder polarization reversal and reduce the dielectric constant and dielectric loss. + Radius larger than Pb 2+ , further aggravating the lattice distortion and improving the polarization characteristics of the material, making the material exhibit higher pyroelectric properties and good temperature stability.

[0023] (2) This application provides a method for preparing a high Curie temperature lead-based pyroelectric material. In order to avoid element volatilization and reduce sintering costs, this application adopts microwave sintering.

[0024] The method avoids deformation and cracking of materials during sintering by adjusting the material forming size and sintering process, thus improving the consistency and yield rate of materials. The standardized sintering temperature and polarization conditions enable the pyroelectric properties of high Curie temperature ceramic materials to be developed to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] (1) Figure 1 Examples 1 to 4 are different molar amounts of K 2 CO 3 The dielectric constant and dielectric loss of PZT-doped high Curie temperature pyroelectric ceramic materials vary with temperature.

[0026] (2) Figure 2 Examples 1 to 4 are different molar amounts of K 2 CO 3 Pyroelectric coefficient of doped PZT high Curie temperature pyroelectric ceramic material at room temperature. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The following are examples:

[0029] Example 1

[0030] Preparation of Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 The pyroelectric material, wherein x=0, comprises the following steps:

[0031] Step 1: PbO (99.5%), ZrO 2 (99.5%),TiO 2 (99.5%),K 2 CO 3 (99.0%), and baked in a muffle furnace at 200 °C for 1 h. 0.9 Ti 0.1 ) 3 -xK 2 CO 3 , (x=0) for weighing. After weighing, the raw material powder is put into a ball mill and ball milled for 24h (zirconium ball: anhydrous ethanol: material = 5:0.8:1). After ball milling, the slurry is put into an oven at 80℃ and dried through a 100-mesh sieve. After sieving, the raw material powder is put into a crucible and compacted, and the temperature is raised to 850℃ at a heating rate of 2℃ / min and kept warm for 2h. The pre-sintered solid solution is crushed and ball milled for 24h, and the material is dried.

[0032] Step 2: Add 8% PVA aqueous solution (1wt%) of the powder mass to the pre-sintered powder in step 1, then granulate and pass through a 120-mesh sieve. Let the sieved powder stand for 24 hours at an aging temperature of 75°C. Press the aged powder into a cylindrical green embryo, and use a cold isostatic press of 100Mpa for 2 minutes. The diameter of the cylindrical green embryo is 10mm and the thickness is 5mm. Put the green embryo into a muffle furnace for debinding, and heat it up at a rate of 1°C / min to 600°C and keep it warm for 2 hours.

[0033] Step 3: After debinding, place the ceramic body in a microwave workstation, raise the temperature to 1020°C at a heating rate of 22°C / min, and keep it warm for 20 minutes to obtain a ceramic block.

[0034] Step 4: Thin the ceramic block, cover both sides with silver electrodes, put it in an 80°C oil bath, polarize it with an electric field of 6kV / mm for 25 minutes, and test the material's pyroelectric coefficient, dielectric constant, dielectric loss, depolarization temperature and other data after standing for 24 hours.

[0035] Example 2

[0036] Preparation of Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 Pyroelectric material, wherein x=0.5%, and the steps are the same as those in Example 1.

[0037] Example 3

[0038] Preparation of Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 Pyroelectric material, wherein x=1.0%, and the steps are the same as those in Example 1.

[0039] Example 4

[0040] Preparation of Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 Pyroelectric material, wherein x=1.5%, and the steps are the same as those in Example 1.

[0041] Results Analysis

[0042] Table 1 lists the dielectric properties and pyroelectric properties of the pyroelectric ceramic materials of the examples

[0043]

[0044] Table 1

[0045] like Figure 1-Figure 2 As shown, Figure 1 Examples 1 to 4 are different molar amounts of K 2 CO 3 The dielectric constant and dielectric loss of PZT doped high Curie temperature pyroelectric ceramic materials vary with temperature. Figure 2 Examples 1 to 4 are different molar amounts of K 2 CO 3 The pyroelectric coefficient of the high Curie temperature pyroelectric ceramic material doped with PZT at room temperature shows that the high Curie temperature lead-based pyroelectric material provided in the present application is obtained by doping K 2 CO 3 , K+ After entering the lattice, it replaces Pb at the A position 2+ Oxygen vacancies are formed, which hinder polarization reversal and reduce the dielectric constant and dielectric loss. + Radius larger than Pb 2+ , further aggravating the lattice distortion and improving the polarization characteristics of the material, making the material exhibit higher pyroelectric properties and good temperature stability.

[0046] The present application provides a method for preparing a high Curie temperature lead-based pyroelectric material. In order to avoid element volatilization and reduce sintering costs, the present application adopts a microwave sintering method, which adjusts the material forming size, sintering process, etc. to avoid deformation and cracking of the material during the sintering process, thereby improving the consistency and yield of the material. The standardized sintering temperature and polarization conditions enable the pyroelectric properties of high Curie temperature ceramic materials to be developed to the greatest extent.

[0047] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high Curie temperature lead-based pyroelectric material, It is characterized in that The chemical composition of the lead-based pyroelectric material is Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 , wherein 0.0≤x≤1.5% (mol), the lead-based pyroelectric material is prepared by doping K into the PZT matrix 2 CO 3 Obtained, K + After entering the lattice, it replaces Pb at the A position 2+ The formation of oxygen vacancies hinders polarization reversal, resulting in a decrease in dielectric constant and dielectric loss, K + Radius larger than Pb 2+ , aggravating the lattice distortion, improving the polarization characteristics of the material, and making the material exhibit high pyroelectric properties and temperature stability.

2. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 1, It is characterized in that The following steps are involved: Step 1: Pb source, Zr source, Ti source and K source are weighed according to the stoichiometric ratio of the ceramic components, ball-milled and dried, pre-sintered, ball-milled and dried to obtain a solid solution powder; Step 2: The solid solution powder obtained in step 1 is mixed with a binder to form granules, and then unidirectionally pressed into a ceramic body; Step 3: Sintering the ceramic body obtained in step 2 by microwave to obtain a bulk ceramic; Step 4: The bulk ceramic obtained in step 3 is subjected to electrode, polarization, and mechanical processing to obtain the product.

3. A method for preparing a high Curie temperature lead-based pyroelectric material as claimed in claim 2, It is characterized in that The stoichiometry of the ceramic components in step 1 is controlled within the range of Pb(Zr 0.9 Ti 0.1 ) 3 -xK 2 CO 3 , where 0.0≤x≤1.5% (mol) interval.

4. A method for preparing a high Curie temperature lead-based pyroelectric material as claimed in claim 2, It is characterized in that The Pb source in step 1 is PbO, and the Zr source is ZrO 2 , Ti source is TiO 2 Among them, PbO, ZrO 2、 TiO 2 The purity of the raw materials is higher than 99.5%, and the K source is K 2 CO 3 , purity higher than 99.00%, all raw materials were baked at 200℃ for 1h before weighing to prevent moisture, and then ball milled and dried.

5. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 2, It is characterized in that The pre-sintering process described in step 1 requires that the powder be screened and then loaded into a crucible for compaction, open pre-sintering, the temperature be controlled at 800-850° C., the insulation time be 2-3 hours, and after sintering, the solid solution powder be obtained by ball milling and drying.

6. A method for preparing a high Curie temperature lead-based pyroelectric material as claimed in claim 2, It is characterized in that The adhesive in step 2 is a 1wt% PVA aqueous solution, and the amount of the PVA aqueous solution added is 8-10% of the mass of the powder. After granulation, it is sieved through a 120-mesh sieve and aged in an oven at a temperature of 70-80°C.

7. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 2, It is characterized in that The molding described in step 2 is to press the solid solution powder into a cylindrical green embryo, using a cold press of 100-150Mpa for 2-5 minutes.

8. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 2, It is characterized in that The ceramic embryo body described in step 2 is a green embryo, and the diameter to thickness ratio of the cylindrical green embryo is controlled to be between 1-3.

9. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 2, It is characterized in that The microwave sintering described in step 3 is to place the ceramic body after debinding into a microwave workstation, raise the temperature to 1000-1100°C at a heating rate of 20-30°C / min, and keep the temperature for 20-40 minutes to obtain a ceramic block.

10. The method for preparing a high Curie temperature lead-based pyroelectric material according to claim 2, It is characterized in that The polarization process described in step 4 is to polarize the ceramic block with the completed electrode in an oil bath at 80° C. using an electric field of 6-7 kV / mm for 20-30 minutes, and then mechanically process it after standing for 24 hours.

11. A method for preparing a high Curie temperature lead-based pyroelectric material as claimed in claim 2, It is characterized in that The product obtained in step 4 was subjected to performance testing. Specifically, under the test conditions of room temperature and 1kHz, the relative dielectric constant was 419-539, the dielectric loss was 0.0121-0.0168, and the pyroelectric coefficient was (1.5-2.8)×10 -4 Cm -2 K- 1 , its depolarization temperature T d It is 274-280℃.

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