A Sm ion doped PZT based piezoelectric ceramic material and preparation method thereof

Abstract

This invention relates to an Sm ion-doped PZT-based piezoelectric ceramic material, represented by the following general chemical formula: Pb 1‑y Ga y (Zr 1‑z Ti z ) m Ta 1‑m O3+xwt%Sm, where x=0.05~1.05, xwt% represents the percentage content of Sm in the total mass of the piezoelectric ceramic material; y=0.015~0.025, z=0.45~0.50, m=0.95~0.98. Sm ion-doped PZT-based piezoelectric ceramic powder was prepared by solid-state reaction method, and then piezoelectric ceramic materials with high Curie temperature, high piezoelectric constant, and high dielectric constant were prepared by combining processes such as pressing, debinding, sintering, silver coating, and polarization. The results show that the Curie temperature Tc of the piezoelectric ceramic material of this invention is greater than 380℃, while the dielectric constant is greater than 900, and the piezoelectric constant d... 33 Greater than 300 pC / N.

Description

Technical Field

[0001] The invention belongs to the technical field of piezoelectric ceramic materials, and in particular relates to a Sm ion-doped PZT-based piezoelectric ceramic material and a preparation method thereof. Background Art

[0002] The normal operation of power equipment is crucial to ensure the safe operation of the power system. If large current shocks, moisture, loose fasteners, etc. occur during the operation of power equipment, partial discharge will often occur, causing potential hidden dangers. Ultrasonic monitoring is currently a common method for partial discharge monitoring. Piezoelectric ceramics have the advantages of high control accuracy, fast response speed, good linearity, and low power consumption. They have been widely used in many fields such as electronics, communications, and medicine.

[0003] Patent application CN115466117A discloses a low-temperature prepared PZT-based piezoelectric ceramic with an ultra-high piezoelectric constant. The general formula of the piezoelectric ceramic is

[0004] Pb 1-x-y-v Li x Ca y [Ni 1 / 3 Nb 2 / 3 ] u (Sm,Eu,Gd) v (Ti, Zr) 1-u O represents, 0≤x≤0.025, 0≤y≤0.001, 0.1≤u≤0.6, 0.01≤v≤0.025. The solid phase reaction method is used to prepare the PZT-based piezoelectric ceramic powder calcined at 750-850℃, and then the ceramic material is prepared by granulation, tableting, debinding, sintering, silver sintering, polarization and other processes. The results show that the PZT-based piezoelectric ceramic material is prepared at a sintering temperature of 900-960℃, which has an ultra-high piezoelectric constant d33=936pC / N, but its Curie temperature is below 130℃. Patent application CN113683414A provides a samarium-doped PZT piezoelectric nanopowder and its preparation method and application. The samarium-doped PZT piezoelectric nanopowder is prepared by a hydrothermal doping process and adding alkyl polyoxyethylene ether, which can effectively reduce the particle size of the prepared powder material and correspondingly improve its piezoelectric performance; and the preparation method is simple and low in cost. The particle size of the samarium-doped PZT piezoelectric powder is 300-400nm; the piezoelectric constant d33 reaches 510pC / N, and it can be effectively used in piezoelectric devices when prepared into piezoelectric ceramics. However, the patent does not pay attention to the high-temperature stability of the material, which poses application risks. The document "Study on Sm-doped Enhanced Piezoelectric Properties of PZT-based Relaxor Ferroelectric Ceramics" (Dong Chang et al., Journal of Inorganic Materials, Vol. 36, No. 12, December 2021) discloses the piezoelectric ceramics prepared by it, which have the following properties: high piezoelectric coefficient d 33 ~824pC / N, high voltage constant g33 ~27.1×10 –3 m 2 / C and relatively high Curie temperature T C ~178℃, and the electrostrain is less than 5% in the range of room temperature to 150℃. Although the piezoelectric ceramic has a certain temperature stability, its Curie temperature is still insufficient.

[0005] With the continuous progress and development of modern science and technology, some important fields are in urgent need of electronic equipment that can work stably at high temperatures, such as petrochemical, electric power, metallurgy and mining, aerospace, etc. The piezoelectric materials used in these electronic equipment must meet the following two conditions when used in high temperature environments. First, the material should have a high Curie temperature so that its piezoelectricity and other comprehensive properties will not be affected by high temperature; second, the piezoelectric parameters of the material can remain stable within a wide temperature range, thereby ensuring that the electronic equipment can work normally during operation, so that it can be suitable for more complex use environments.

[0006] The commercially used lead zirconate titanate piezoelectric ceramic materials, such as those in the above literature, can provide higher piezoelectric constants, but the improvement and increase of Curie temperature is limited, generally below 380°C. Due to the heat-activated aging process, its safe use temperature is limited to 1 / 2 of the Curie temperature. High-temperature piezoelectric ceramic materials with excellent piezoelectric properties and use temperatures below 380°C can no longer meet the requirements of current high-tech development. In addition, the piezoelectric materials used in commercial high-temperature sensors are limited to single crystal materials such as LiNbO3, with complex production processes and extremely expensive prices. In addition, there are currently no high-temperature piezoelectric ceramic sensor products with excellent performance and use temperatures above 350°C in China, and there are few research reports on such devices abroad.

[0007] Therefore, high-temperature piezoelectric ceramic materials have become a hot topic in recent years. How to provide high-performance piezoelectric ceramic materials with high Curie temperature, high piezoelectric constant and high dielectric constant, and use them for the manufacture of high-performance piezoelectric sensors or ultrasonic monitors for partial discharge detection of power equipment by taking advantage of their broadband and high-sensitivity characteristics, and provide high value-added products, has become a technical problem that needs to be solved in this field. Summary of the invention

[0008] In view of the defects existing in the above-mentioned prior art, the object of the present invention is to provide a Sm ion-doped PZT-based piezoelectric ceramic material and a preparation method thereof, which can provide a piezoelectric ceramic material with high Curie temperature, high piezoelectric constant and high dielectric constant.

[0009] Specifically, the present invention provides a Sm ion-doped PZT-based piezoelectric ceramic material represented by the following chemical formula: Pb 1-y Ga y (Zr1-z Ti z ) m Ta 1-m O3+xwt%Sm, wherein x=0.05-1.05, xwt% represents the percentage content of Sm in the total mass of the piezoelectric ceramic material; y=0.015-0.025, z=0.45-0.50, m=0.95-0.98.

[0010] In order to obtain satisfactory comprehensive performance, the chemical formula of the piezoelectric ceramic material of the present invention can be further expressed as: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.1~1.

[0011] Furthermore, the Curie temperature Tc of the piezoelectric ceramic material is greater than 380°C, preferably greater than 400°C, and the dielectric constant is greater than 900, and the piezoelectric constant d 33 Greater than 300pC / N, and Curie temperature Tc, dielectric constant and piezoelectric constant d 33 Adjustable within a wide range.

[0012] Based on the traditional PbZrO3-PbTiO3 (PZT) material, the present invention chooses to incorporate high-performance elements to optimize performance. The appropriate amount of Sm ions, a lanthanide rare earth element, can improve the dielectric properties and piezoelectric properties of PZT piezoelectric ceramics in a balanced manner. The Sm ion content has strict restrictions. When its content is too low, for example, x is below 0.1, especially when it is less than 0.05, it plays a very small role. Even if a higher Curie temperature can be obtained, the improvement of its overall dielectric properties and piezoelectric properties is not obvious enough; but when its content is too high, especially when x is greater than 1.05, its Curie temperature drops more significantly. In summary, x values ​​between 0.05 and 1.05, preferably 0.1 to 1.0, can take into account the comprehensive performance of the material.

[0013] In a second aspect, with respect to the above-mentioned piezoelectric ceramic material, the present invention further provides a method for preparing the piezoelectric ceramic material, comprising the following steps:

[0014] (1) The raw materials are mixed by ball milling, and then dried, ground, sieved, and pre-pressed in sequence. The pre-pressed bulk material is calcined at 750-900° C. for 1-2 hours under closed conditions;

[0015] (2) crushing the material calcined in step (1), ball milling it for a second time, drying it, sieving it, adding the PVA aqueous solution, grinding it thoroughly, and sieving it again;

[0016] (3) molding the sieved material in step (2) to obtain a green sheet, degreasing and debinding the green sheet, and then sintering at 1100° C. to 1300° C. to obtain a sintered body;

[0017] (4) polishing the sintered body obtained in step (3), applying medium-temperature silver paste on the surface and then drying it, and sintering it at 600-700° C. for 1-2 hours to obtain a silver-coated ceramic sheet;

[0018] (5) The silver-coated ceramic sheet obtained in step (4) is polarized in silicone oil, taken out and naturally aged in air to obtain a piezoelectric ceramic material.

[0019] Furthermore, in step (1), each raw material is divided into two groups, the first group includes Pb3O4, ZrO2 and TiO2, and the second group includes Ta, GaO and Sm; the order of adding each raw material to the ball mill is: first add one from the first group, then add one from the second group, and cycle until all raw materials are added. The raw materials are added to the ball mill in the order of more and less, and the ball milling is effectively prevented from deviating from the chemical ratio caused by the adhesion of the material with a smaller content. After testing and optimization, Pb3O4, Ta2O5, ZrO2, GaO, TiO2, Sm, or Pb3O4, GaO, ZrO2, Ta2O5, TiO2, Sm are added in order.

[0020] Furthermore, in step (1), star ball milling is carried out in a ball mill, and the weight ratio of balls in the ball mill: total amount of raw materials: anhydrous ethanol is (1.8-2.5):1:(0.5-1), the speed of the ball mill is 200-300 rad / min, and the time is 10-12 h; the drying temperature is 80-100° C.; and the sieving is through a 60-80 mesh sieve.

[0021] Furthermore, in step (2), the mass percentage concentration of the PVA aqueous solution is 10% to 15%, and the amount of the PVA aqueous solution added is 5 to 8% of the total mass of the raw materials; the sieving is through a 250-350 mesh sieve; and the re-sieving is through a 60-80 mesh sieve. In addition, the preferred degree of polymerization of PVA is 1700 to 1800, the viscosity is moderate, and the bonding effect is good. When the PVA polymerization degree is too large, the chain segments are long, the bonding force and elasticity are large, which is not conducive to subsequent molding and other operations; when the polymerization degree is too small, the chain segments are short, the elasticity and bonding force are small, and it does not act as an adhesive.

[0022] Furthermore, in step (3), degreasing, debinding and sintering include the following steps:

[0023] S3.1 Raise the temperature to 200-220°C at a rate of 0.5-1°C / min and keep warm for 1-2h;

[0024] S3.2 Raise the temperature to 500-600℃ at a heating rate of 1-3℃ / min and keep it at this temperature for 1-2h;

[0025] S3.3 Heating at a rate of 2-5°C / min to 800-900°C and keeping at this temperature for 1-2h;

[0026] S3.4 Heat up to 1100-1300℃ at a heating rate of 1-2℃ / min and keep warm for 1-2h, then cool with the furnace.

[0027] The degreasing and sintering steps have a great influence on the material properties. The heating rate, target temperature and holding time of each link must be explored through a lot of experiments. The binder in the molded green sheet is a polymer compound with a lot of carbon. When the carbon is insufficient in oxygen, it burns to produce carbon monoxide with strong reducing properties. Carbon monoxide takes away the oxygen in PZT to form carbon dioxide, which reduces the metal oxides to conductive metals (such as Pb) and low-valent oxides with semiconductor properties (such as Ti2O3), affecting the color, porcelain-forming properties, silver burning, polarization and final properties of the ceramic. Therefore, before sintering, the green sheet must be degreased and debinded. According to the volatility of the PVA binder, the heating rate and holding time of degreasing and debinding need to be strictly controlled. 100-200℃ is the volatilization zone of water, which needs to be heated slowly and kept warm for a period of time; 200-600℃ is the volatilization zone of PVA, and the binder is completely removed at a high temperature of 500-600℃ for a period of time.

[0028] Since Pb is volatile at high temperatures, small-sized blanks with simple shapes can be heated up quickly and kept warm for a short period of time. However, for large blanks with complex shapes, the heating speed should be slowed down and the holding time should be extended to ensure uniform sintering of the product. It is preferred to sinter in a sealed sintering furnace to avoid lead loss.

[0029] Furthermore, in step (4), the silver powder content of the medium-temperature silver paste is 60-75wt%, the viscosity is 550-650Pa·s, the silver powder is spherical silver powder with a particle size of 0.5-3μm, and D50=0.8-1μm; the drying temperature is 80-100°C; and the sintering silver layer has a thickness of 1-2μm.

[0030] Furthermore, in step (5), the silicone oil temperature is 120-130° C., and the polarization is carried out at a DC voltage of 2-3 kV / mm for 15-20 min; and the natural aging time is 20-24 h.

[0031] In a third aspect, the present invention also provides the use of the piezoelectric ceramic material in manufacturing a piezoelectric sensor or an ultrasonic monitor.

[0032] The present invention has the advantages that:

[0033] (1) The present invention adopts reasonable raw material types and ratios to obtain a high comprehensive performance piezoelectric ceramic material with high Curie temperature, high piezoelectric constant and high dielectric constant. It has a single perovskite structure, breaks through the defect of insufficient Curie temperature of conventional lead zirconate titanate system piezoelectric ceramics, and provides material support for the development of commercial high-temperature sensors.

[0034] (2) A preparation method designed for the high-performance piezoelectric ceramic material of the present invention is provided. For example, in the preparation process of the piezoelectric ceramic material, the raw materials are added in the order of first adding a large amount of raw material and then adding a small amount of raw material. The raw materials are added to the ball mill in the order of more and then less, which effectively prevents the deviation of the chemical ratio caused by the adhesion of the material with a small content to the wall, ensures that the actual ratio of the final material is extremely small compared with the theoretical ratio, and effectively prepares a piezoelectric ceramic material with excellent comprehensive properties such as high Curie temperature, high dielectric constant and high piezoelectric constant. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below. The described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. The terms "include", "comprise", "have" and "contain" should be understood in a broad and open sense, that is, they are not limited to the listed contents. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] A Sm ion doped PZT based piezoelectric ceramic material, in particular a piezoelectric ceramic material for manufacturing a piezoelectric sensor, such as a high temperature piezoelectric sensor, is represented by the following chemical formula: Pb 1-y Ga y (Zr 1-z Ti z ) m Ta 1-m O3+xwt%Sm, wherein x=0.05-1.05, xwt% represents the percentage of Sm in the total mass of the piezoelectric ceramic material; y=0.015-0.025, z=0.45-0.50, m=0.95-0.98. Preferably, the chemical formula can be further expressed as the following composition: Pb 0.98 Ga 0.02 (Zr 0.52 Ti0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.1~1.

[0038] Through reasonable proportioning, the Curie temperature Tc of the piezoelectric ceramic material of the present invention is greater than 380°C, preferably greater than 400°C, and the dielectric constant is greater than 900, and the piezoelectric constant d 33 Greater than 300C / N.

[0039] Based on the traditional PbZrO3-PbTiO3 (PZT) material, the present invention selects to dope high-performance elements for performance optimization. The appropriate doping of lanthanide rare earth element Sm ions can improve the dielectric properties and piezoelectric properties of PZT piezoelectric ceramics in a balanced manner. With the increase of the amount of Sm ion doping, the perovskite structure of the piezoelectric ceramic itself remains unchanged, and it has a single perovskite structure. The rhombohedral crystal phase content of the material composition decreases at the MPB, and the MPB approaches another crystal phase, namely the tetrahedral crystal phase. In terms of the internal microstructure of the ceramic, the doping of Sm ions inhibits the growth of ceramic grains, making the grains smaller, and as the doping concentration increases, the grain size further decreases, but the trend slows down. The domain size is positively correlated with the 1 / 2 power of the grain size. The decrease in domain size can reduce the clamping effect during polarization reversal and increase the response speed, thereby obtaining better piezoelectric performance. On the other hand, fine grains can withstand higher mechanical strength, which plays an extremely important role in high-frequency ultrasonic applications.

[0040] The incorporation of Ga ions and Ta ions is beneficial to improving the Curie temperature and temperature stability of piezoelectric ceramic materials.

[0041] In order to obtain the above-mentioned high-performance piezoelectric ceramic material, the present invention specifically proposes a method for preparing the piezoelectric ceramic material, comprising the following steps:

[0042] (1) According to the chemical formula Pb 1-y Ga y (Zr 1-z Ti z ) m Ta 1-m O3+xwt%Sm, wherein x=0.05-1.05, xwt% represents the percentage content of Sm in the total mass of the piezoelectric ceramic material; y=0.015-0.025, z=0.45-0.50, m=0.95-0.98, and the raw materials are weighed; preferably, according to the chemical formula Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04O3+xwt%Sm, wherein x=0.1~1, Pb3O4, GaO, Ta2O5, TiO2, ZrO2, Sm are used as raw materials, and each raw material is weighed; each raw material is added into a ball mill for star-type ball milling mixing, the weight ratio of balls in the ball mill: total amount of raw materials: anhydrous ethanol is (1.8~2.5):1:(0.5~1), the rotation speed of the ball mill is 200~300rad / min, and the time is 10~12h; after ball milling, drying (preferably the drying temperature is 80~100℃), grinding, sieving (preferably sieving through a 60~80 mesh sieve), and pre-pressing are carried out in sequence, and the block material after pre-pressing is calcined at 750~900℃ under closed conditions for 1~2h; this calcination belongs to the pre-burning step, which is beneficial to the full uniformity of the solid-phase chemical reaction of each raw material, the formation of a solid solution with a fixed composition, and the formation of a main crystal phase. Remove carbon dioxide and moisture from the raw materials to reduce the firing shrinkage and deformation of the green body, so as to control the product's external dimensions.

[0043] The specific order of adding raw materials is: divide the raw materials into two groups, the first group includes Pb3O4, ZrO2 and TiO2, and the second group includes Ta, GaO and Sm; the order of adding each raw material to the ball mill is: first add one from the first group, then add one from the second group, and cycle until all the raw materials are added. The order of adding follows the principle of first adding a large amount of raw materials (i.e., the raw materials of the first group) and then adding a small amount of raw materials (i.e., the raw materials of the second group), and then adding the raw materials to the ball mill in the order of more and less, so as to effectively prevent the deviation of the chemical ratio caused by the adhesion of the material with a smaller content. The specific matching order between the two groups can be combined according to actual needs.

[0044] (2) The calcined material in step (1) is crushed and ball-milled for a second time (the conditions of the second ball-milling can be the same as those of the previous ball-milling or can be slightly adjusted), then dried, sieved (preferably sieved through a 250-350 mesh sieve), PVA aqueous solution is added, fully ground, and sieved again (preferably sieved through a 60-80 mesh sieve); preferably, the mass percentage concentration of the PVA aqueous solution is 10%-15%, the amount of the PVA aqueous solution added is 5-8% of the total mass of the raw materials, and the degree of polymerization of the PVA is 1700-1800, the viscosity is moderate, and the bonding effect is good. When the PVA polymerization degree is too large, the chain segments are long, the bonding force and elasticity are large, which is not conducive to subsequent molding and other operations; when the polymerization degree is too small, the chain segments are short, the elasticity and bonding force are small, and it does not play the role of an adhesive.

[0045] (3) The sieved material in step (2) is molded to obtain a green sheet, the green sheet is degreased and debinded at 500-600° C., and then sintered at 1100-1300° C. for 1-2 hours to obtain a sintered body; specifically, the degreasing and debinding and heat-insulating sintering include the following steps:

[0046] S3.1 Raise the temperature to 200-220°C at a rate of 0.5-1°C / min and keep warm for 1-2h;

[0047] S3.2 Raise the temperature to 500-600℃ at a heating rate of 1-3℃ / min and keep it at this temperature for 1-2h;

[0048] S3.3 Heating at a rate of 2-5°C / min to 800-900°C and keeping at this temperature for 1-2h;

[0049] S3.4 Heat up to 1100-1300℃ at a heating rate of 1-2℃ / min and keep warm for 1-2h, then cool with the furnace.

[0050] The binder in the molded green sheet is a polymer compound with a high carbon content. When the carbon is insufficient in oxygen, it burns to produce highly reducing carbon monoxide. Carbon monoxide takes away the oxygen in PZT to form carbon dioxide, which reduces the metal oxide to conductive metals (such as Pb) and low-valent oxides with semiconductor properties (such as Ti2O3), affecting the color, porcelain-forming properties, silver burning, polarization and final performance of the ceramic. Therefore, before sintering, the green sheet must be plasticized. According to the volatility of the PVA binder, the heating rate and insulation time of plasticizing need to be strictly controlled. 100-200℃ is the volatilization zone of water, which needs to be heated slowly and kept warm for a period of time; 200-600℃ is the volatilization zone of PVA, and the high temperature of 500-600℃ is kept warm for a period of time to completely debond.

[0051] Since Pb is volatile at high temperatures, small-sized blanks with simple shapes can be heated up quickly and kept warm for a short period of time. However, for large blanks with complex shapes, the heating speed should be slowed down and the holding time should be extended to ensure uniform sintering of the product. Sealed sintering is preferred to avoid lead loss.

[0052] (4) polishing the sintered body obtained in step (3), then applying medium-temperature silver paste on the surface, drying at 80-100° C., and sintering at 600-700° C. for 1-2 hours to obtain a silver-coated ceramic sheet, wherein the silver layer thickness is 1-2 μm; wherein the silver powder content of the medium-temperature silver paste is 60-75 wt %, the viscosity is 550-650 Pa·s, the silver powder is spherical silver powder with a particle size of 0.5-3 μm, and D50 is 0.8-1 μm;

[0053] (5) polarizing the silver-coated ceramic sheet obtained in step (4) in silicone oil at a temperature of 120 to 130° C. at a DC voltage of 2 to 3 kV / mm for 10 to 30 min, and then taking it out and naturally aging it in air for 20 to 24 h to obtain a piezoelectric ceramic material.

[0054] Example 1

[0055] The piezoelectric ceramic material sample of this embodiment has the following chemical formula: Pb 0.98 Ga0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.8.

[0056] The method for preparing the piezoelectric ceramic material specifically comprises the following steps:

[0057] (1) The raw materials are weighed according to the stoichiometric ratio of the above chemical formula, and then added into a ball mill in the order of Pb3O4, Ta2O5, ZrO2, GaO, TiO2, and Sm for star-shaped ball milling; the weight ratio of ball: material: anhydrous ethanol in the ball mill is 2:1:0.7, the ball mill speed is 200 rad / min, and the mixed materials are taken out after ball milling for 12 hours, and the mixed materials are placed in an oven, dried at 90°C, and then placed in a mortar and ground through a 60-mesh sieve; the sieved materials are placed in a mold for pre-pressing, and the pre-pressed block materials are placed in a crucible and sealed with a cover, and calcined at 850°C for 2 hours.

[0058] (2) The calcined material in step (1) is crushed, ball-milled for a second time, dried, and passed through a 325-mesh sieve. A 12% PVA aqueous solution is added at a ratio of 6% of the total mass of the raw material, and the mixture is fully ground in a mortar and then passed through a 60-mesh sieve.

[0059] (3) The material screened in step (2) is molded to obtain a green sheet; the green sheet is first degreased and debinded, and then heat-insulated and sintered to obtain a sintered body. The specific degreasing and debinding and heat-insulated sintering process includes the following steps:

[0060] S3.1 Raise the temperature to about 210℃ at a heating rate of 1℃ / min and keep it at that temperature for 1h;

[0061] S3.2 Raise the temperature to about 500°C at a heating rate of 2°C / min and keep it at this temperature for 1.5h;

[0062] S3.3 Heating at a rate of 3°C / min to about 850°C and keeping at that temperature for 1h;

[0063] S3.4 Heat the temperature to about 1180℃ at a heating rate of 1℃ / min and keep it at this temperature for 1.5h, then cool it in the furnace.

[0064] (4) polishing the sintered body obtained in step (3), applying medium-temperature silver paste on the surface thereof, drying at 80° C., and sintering at 600° C. for 1.5 h to obtain a silver-coated ceramic sheet; wherein the silver powder content of the medium-temperature silver paste is 70 wt %, the viscosity is 600 Pa·s, the silver powder is spherical silver powder with a particle size of 0.5 to 3 μm, and D50 is 0.8 to 1 μm; and the thickness of the silver layer is about 1.5 μm;

[0065] (5) The silver-coated ceramic sheet obtained in step (4) is placed in silicone oil at 120° C., polarized at a DC voltage of 3 kV / mm for 15 min, and then taken out and naturally aged in air for 24 h to obtain a ceramic sheet.

[0066] The ceramic sheet was tested for performance, and the results were: 33 =1080PC / N, Tc=390℃, εr=1380.

[0067] Example 2

[0068] The piezoelectric ceramic material samples of this embodiment and embodiment 1 have different chemical formulas, but are produced using the same preparation process as embodiment 1.

[0069] Example 2 The chemical formula of the sample is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=1.0, the performance test of the ceramic sheet of comparative example 1 was carried out, and the results obtained were:

[0070] d 33 =890C / N, Tc=385℃, ε r =1510.

[0071] Example 3

[0072] The piezoelectric ceramic material samples of this embodiment and embodiment 1 have different chemical formulas, but are produced using the same preparation process as embodiment 1.

[0073] Example 3 The chemical formula of the sample is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.1, the performance test of the ceramic sheet of comparative example 1 was carried out, and the results obtained were:

[0074] d 33 =330PC / N, Tc=485℃, ε r =1200.

[0075] Example 4

[0076] The piezoelectric ceramic material sample of this embodiment has the following chemical formula: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 )0.96 Ta 0.04 O3+xwt%Sm, where x=0.4.

[0077] The method for preparing the piezoelectric ceramic material specifically comprises the following steps:

[0078] (1) The raw materials were weighed according to the stoichiometric ratio of the above chemical formula, and then added into a ball mill in the order of Pb3O4, GaO, ZrO2, Ta2O5, TiO2, and Sm for star-shaped ball milling; and the weight ratio of ball: material: anhydrous ethanol in the ball mill was 2:1:0.7, and the ball milling speed was 250 rad / min. After ball milling for 12 hours, the mixed material was taken out and placed in an oven, dried at 85°C, and then placed in a mortar and ground through a 65-mesh sieve. The sieved material was placed in a mold for pre-pressing, and the pre-pressed block material was placed in a crucible and sealed with a cover, and calcined at 900°C for 1.5 hours.

[0079] (2) The calcined material in step (1) is crushed, ball-milled for a second time, dried, and passed through a 250-mesh sieve. A 12% PVA aqueous solution is added at a ratio of 6% of the total mass of the raw material, and the mixture is fully ground in a mortar and then passed through a 65-mesh sieve.

[0080] (3) The material screened in step (2) is molded to obtain a green sheet; the green sheet is first degreased and debinded, and then heat-insulated and sintered to obtain a sintered body. The specific degreasing and debinding and heat-insulated sintering process includes the following steps:

[0081] S3.1 Raise the temperature to about 220℃ at a heating rate of 1℃ / min and keep it at that temperature for 1h;

[0082] S3.2 Raise the temperature to about 600℃ at a heating rate of 2℃ / min and keep it at this temperature for 1.5h;

[0083] S3.3 Heating at a rate of 4°C / min to about 900°C and keeping at that temperature for 1h;

[0084] S3.4 Heat up to about 1200℃ at a heating rate of 1℃ / min and keep at this temperature for 2h, then cool in the furnace.

[0085] (4) polishing the sintered body obtained in step (3), applying medium-temperature silver paste on the surface thereof, drying at 85° C., and sintering at 600° C. for 2 h to obtain a silver-coated ceramic sheet; wherein the silver powder content of the medium-temperature silver paste is 70 wt %, the viscosity is 600 Pa·s, the silver powder is spherical silver powder with a particle size of 0.5 to 3 μm, and D50 is 0.8 to 1 μm; and the thickness of the silver layer is about 1.5 μm;

[0086] (5) The silver-coated ceramic sheet obtained in step (4) is placed in silicone oil at 125° C., polarized at a DC voltage of 2.5 kV / mm for 20 min, and then taken out and naturally aged in air for 22 h to obtain a ceramic sheet.

[0087] The ceramic sheet was tested for performance, and the results were: 33 =520PC / N, Tc=440℃, εr=1460.

[0088] Example 5

[0089] The piezoelectric ceramic material samples of this embodiment have the same chemical composition as that of Example 4, but the order in which the raw materials are added to the ball mill is different. Pb3O4, Ta2O5, GaO, Sm, ZrO2, and TiO2 are added to the ball mill in this order for star-type ball milling, and the rest of the preparation process is the same.

[0090] The ceramic sheet was tested for performance, and the results were: 33 =320PC / N, Tc=433℃, εr=978.

[0091] Comparative Example 1

[0092] The piezoelectric ceramic material samples of this comparative example and Example 1 have different chemical formulas, but are produced using the same preparation process as Example 1.

[0093] The chemical formula of the sample in Comparative Example 1 is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=1.1, the performance test of the ceramic sheet of comparative example 1 was carried out, and the results obtained were:

[0094] d 33 =760PC / N, Tc=330℃, ε r =1410.

[0095] Comparative Example 2

[0096] The piezoelectric ceramic material samples of this comparative example and Example 1 have different chemical formulas, but are produced using the same preparation process as Example 1.

[0097] The chemical formula of the sample in comparative example 2 is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.02, the performance test of the ceramic sheet of comparative example 1 was carried out, and the results obtained were:

[0098] d 33=190PC / N, Tc=498℃, εr=820.

[0099] Comparative Example 3

[0100] The sample of this comparative example is not doped with Sm ions, that is, it has a different chemical formula from the piezoelectric ceramic material sample of Example 1, and correspondingly has a different raw material composition and addition sequence. The rest of the preparation process is the same as that of Example 1.

[0101] The chemical formula of the sample in comparative example 3 is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3, Pb3O4, Ta2O5, ZrO2, TiO2 and GaO were added to the ball mill in the order of star milling. The performance of the ceramic slices of the comparative example 3 was tested, and the results were as follows: 33 =150PC / N, Tc=510℃, εr=780.

[0102] Some parameters and test results of Examples 1-5 and Comparative Examples 1-3 can be seen in Table 1:

[0103] Table 1 Performance test results of Examples 1-5 and Comparative Examples 1-3

[0104]

[0105] The above introduces the preferred embodiments of the present invention, which is intended to make the spirit of the present invention clearer and easier to understand, but is not intended to limit the present invention. All modifications, substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection outlined by the claims attached to the present invention.

Claims

1. A method for preparing a Sm ion-doped PZT-based piezoelectric ceramic material, characterized in that: The piezoelectric ceramic material is represented by the following chemical formula: Pb 1-y Ga y (Zr 1-z Ti z ) m Ta 1-m O3+xwt%Sm, wherein x=0.1-0.4, xwt% represents the percentage of Sm in the total mass of the piezoelectric ceramic material; y=0.015-0.025, z=0.45-0.50, m=0.95-0.98; the Curie temperature Tc of the piezoelectric ceramic material is ≥440°C, and the piezoelectric constant d 33 ≥330pC / N, dielectric constant ≥1200; The preparation method comprises the following steps: (1) The raw materials are mixed by ball milling, and then dried, ground, sieved, and pre-pressed in sequence. The pre-pressed bulk material is calcined at 750-900° C. for 1-2 hours under closed conditions; (2) crushing the material calcined in step (1), ball milling it for a second time, drying it, sieving it, adding the PVA aqueous solution, grinding it thoroughly, and sieving it again; (3) molding the sieved material in step (2) to obtain a green sheet, degreasing and debinding the green sheet, and then sintering at 1100° C. to 1300° C. to obtain a sintered body; Debinding and sintering include the following steps: S3.1 Raise the temperature to 200-220°C at a rate of 0.5-1°C / min and keep warm for 1-2h; S3.2 Raise the temperature to 500-600℃ at a heating rate of 1-3℃ / min and keep it at this temperature for 1-2h; S3.3 Heating at a rate of 2-5°C / min to 800-900°C and keeping at this temperature for 1-2h; S3.4 Raise the temperature to 1100-1300℃ at a heating rate of 1-2℃ / min and keep at this temperature for 1-2h, then cool with the furnace; (4) polishing the sintered body obtained in step (3), applying medium-temperature silver paste on the surface and drying it, sintering it at 600-700° C. for 1-2 hours to obtain a silver-coated ceramic sheet with a silver layer thickness of 1-2 μm; the medium-temperature silver paste has a silver powder content of 60-75 wt %, a viscosity of 550-650 Pa·s, and the silver powder is a spherical silver powder with a particle size of 0.5-3 μm, and D50=0.8-1 μm; (5) The silver-coated ceramic sheet obtained in step (4) is polarized in silicone oil, taken out and naturally aged in air to obtain a piezoelectric ceramic material.

2. The preparation method according to claim 1, characterized in that The chemical formula is: Pb 0.98 Ga 0.02 (Zr 0.52 Ti 0.48 ) 0.96 Ta 0.04 O3+xwt%Sm, where x=0.1~0.

4.

3. The preparation method according to claim 1, characterized in that: In step (1), the raw materials are divided into two groups, the first group includes Pb3O4, ZrO2 and TiO2, and the second group includes Ta, GaO and Sm; the order of adding the raw materials to the ball mill is: first add one from the first group, then add one from the second group, and repeat until all the raw materials are added.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (1), star ball milling is performed in a ball mill, and the weight ratio of balls in the ball mill: the total amount of raw materials: anhydrous ethanol is (1.8-2.5):1:(0.5-1), the rotation speed of the ball mill is 200-300 rad / min, and the time is 10-12 h; the drying temperature is 80-100° C.; and the sieving is through a 60-80 mesh sieve.

5. The method for preparing the Sm ion-doped PZT-based piezoelectric ceramic material according to claim 4, characterized in that: In step (2), the mass percentage concentration of the PVA aqueous solution is 10% to 15%, and the amount of the PVA aqueous solution added is 5 to 8% of the total mass of the raw materials; The sieving is through a 250-350 mesh sieve; the further sieving is through a 60-80 mesh sieve.

6. The preparation method according to claim 4, characterized in that: In step (4), the drying temperature is 80-100°C.

7. The preparation method according to claim 4, characterized in that: In step (5), the silicone oil temperature is 120-130° C., and the silicone oil is polarized at a DC voltage of 2-3 kV / mm for 15-20 min; the natural aging time is 20-24 h.

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