Piezoelectric ceramics, their preparation methods and applications

Abstract

This invention discloses a piezoelectric ceramic, its preparation method, and its applications. The preparation method of the piezoelectric ceramic includes: mixing Pb, Zr, Ti, Nb, Zn, Ni, Mg, and W sources until homogeneous; pre-firing the mixture at 800-850°C in air to obtain a pre-fired material; mixing Li₂CO₃ with the pre-fired material until homogeneous to obtain a piezoelectric ceramic material; granulating the mixture; pressing it into shape; sintering it at 900-950°C in air; and polarizing it in silicone oil to obtain the piezoelectric ceramic. This invention constructs a piezoelectric ceramic with a composite perovskite structure through doping with Zn, Ni, Nb, Mg, and W. The piezoelectric ceramic of this invention has a high Curie temperature and piezoelectric constant. The high Curie temperature allows it to maintain good piezoelectric properties at higher temperatures.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramics technology, specifically relating to a piezoelectric ceramic, its preparation method, and its application. Background Technology

[0002] Lead zirconate titanate (PZT)-based piezoelectric ceramics have been widely used in the manufacture of actuators, sensors, filters, and ultrasonic transducers due to their excellent electrical properties and low production costs. However, the sintering temperature of traditional PZT-based piezoelectric ceramics is typically above 1200℃. On the one hand, the sintering process generates significant lead volatilization, polluting the environment and posing a health hazard. On the other hand, when designing multilayer piezoelectric ceramic products, the PZT-based piezoelectric ceramics need to be co-fired with the electrode materials. Commonly used electrode materials have melting points of 962℃ for silver, 1083℃ for copper, and 1554℃ for palladium. To match the sintering temperature of PZT-based piezoelectric ceramics, the industry typically uses silver-palladium alloys during the sintering of multilayer piezoelectric ceramic products. However, palladium is very expensive, significantly increasing costs. Therefore, lowering the sintering temperature of PZT-based piezoelectric ceramics and using other metals instead of palladium can not only avoid the environmental and health hazards caused by Pb volatilization but also significantly reduce production costs.

[0003] Furthermore, with the rapid development of consumer electronics, smart homes, automobiles, and semiconductors, piezoelectric ceramics have new application demands in areas such as acoustic compensation, touch control, motors, and flow control. These demands require piezoelectric ceramic materials to possess high Curie temperatures (typically above 300℃), low losses, and high piezoelectric properties. This ensures stable performance and low leakage current at different operating temperatures, minimal heat generation during long-term use, and a long lifespan. However, it is well known that achieving piezoelectric properties, Curie temperature, and dielectric loss simultaneously at low sintering temperatures is difficult. Therefore, balancing different performance parameters to meet product application requirements is crucial. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a piezoelectric ceramic that solves the problem of the difficulty in preparing piezoelectric ceramics with both high piezoelectric properties and high Curie temperatures at low sintering temperatures. The piezoelectric ceramic can be expressed as "(1-xy)Pb(Zr 0.5 Ti 0.5 )O3-xPb((Ni a Zn 1-a ) 1 / 3 Nb 2 / 3 )O3-yPb(Mg 1 / 2 W 1 / 2 )O3+Li2O.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned piezoelectric ceramic.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] A piezoelectric ceramic comprising: a solid solution formed of PZT, PZN-PNN, and PMW, and Li, wherein Li is doped in the solid solution, and the structural formula of PZN-PNN is Pb((Ni a Zn 1-a ) 1 / 3 Nb 2 / 3 The structural formula of Pb(Zr)O3 and PZT is Pb(Zr)O3. 0.5 Ti 0.5 The structural formula of Pb(Mg)O3,PMW is Pb(Mg) 1 / 2 W 1 / 2 O3, wherein, by molar fraction, the ratio of PZT, PZN-PNN and PMW is (1-xy):x:y, 0 <x<0.18,0<y<0.05,x+y<0.18,0<a<1。

[0008] In the above technical solution, PZN-PNN is a solid solution formed by lead zinc niobate and lead nickel niobate.

[0009] In the above technical solution, Li is introduced from Li2CO3, Pb is introduced from Pb source, Zr is introduced from Zr source, Ti is introduced from Ti source, Nb is introduced from Nb source, Zn is introduced from Zn source, Ni is introduced from Ni source, Mg is introduced from Mg source, and W is introduced from W source. The mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source, and W source, where M = 0.01~1.

[0010] In the above technical solution, the preferred values ​​are: 0.3 ≤ a ≤ 0.5, 0.09 <x<0.15,0<y<0.03。

[0011] Of the above technical solutions, the preferred value is 0.13. <x<0.15,0.01<y<0.03,M=0.4~0.6。

[0012] A method for preparing piezoelectric ceramics includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source, and W source until homogeneous; pre-firing at 800-850°C in air atmosphere to obtain a pre-fired synthetic material; mixing Li2CO3 with the pre-fired synthetic material until homogeneous to obtain a piezoelectric ceramic material; granulating; pressing; sintering at 900-950°C in air atmosphere; and polarizing in silicone oil to obtain the piezoelectric ceramic. The ratio of Pb in the Pb source, Zr in the Zr source, Ti in the Ti source, Nb in the Nb source, Zn in the Zn source, Ni in the Ni source, Mg in the Mg source, and W in the W source, by molar proportions, is 1:0.5(1-xy):0.5(1-xy): : : : : The mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source, where M = 0.01~1.

[0013] In the above technical solution, the Pb source is Pb3O4, the Zr source is ZrO2, the Ti source is TiO2, the Nb source is Nb2O5, the Zn source is ZnO, the Ni source is NiO, the Mg source is MgO, and the W source is WO3.

[0014] In the above technical solution, the pre-firing time is 3~5 hours and the sintering time is 3~6 hours.

[0015] In the above technical solution, granulation uses a binder, and the mass of the binder is 8 to 15 wt% of the mass of the piezoelectric ceramic material.

[0016] In the above technical solution, the adhesive is a polyvinyl alcohol aqueous solution, and the content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10~20wt%.

[0017] In the above technical solution, Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source are mixed and ball-milled until uniform, wherein the ball milling is a wet ball milling.

[0018] In the above technical solution, Li2CO3 and the pre-calcined material are mixed and ball-milled until uniform, and the ball milling is a wet ball milling.

[0019] In the above technical solution, the medium for wet ball milling is water.

[0020] In the above technical solution, the wet ball milling is followed by drying.

[0021] In the above technical solution, the polarization field strength is 1~3KV / mm, and the polarization temperature is 120~150℃.

[0022] The above preparation method is applied to improving the piezoelectric constant, mechanical quality factor, dielectric loss and / or Curie temperature of piezoelectric ceramics.

[0023] In the above technical solution, the piezoelectric ceramic has a piezoelectric constant ≥520pC / N and a Curie temperature ≥320℃.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention constructs a piezoelectric ceramic with a composite perovskite structure by doping with Zn, Ni, Nb, Mg, and W. The piezoelectric ceramic of this invention has a high Curie temperature and piezoelectric constant. The high Curie temperature enables it to maintain good piezoelectric properties at higher temperatures, thus broadening the application range of the material.

[0026] 2. This invention optimizes the doping amounts of Zn, Ni, Nb, Mg, and W to reduce defects and impurities inside piezoelectric ceramics, thereby improving the dielectric properties of piezoelectric ceramics and reducing dielectric loss. This is very important for the fabrication of high-performance electrical devices.

[0027] 3. This invention uses Li₂CO₃ as a sintering aid, which lowers the sintering temperature and improves sintering activity, thus facilitating the preparation of dense and uniform piezoelectric ceramics and improving the stability of their mechanical and electrical properties. Li₂CO₃ has a low melting point of 723℃. In the early and middle stages of sintering, the liquid phase formed by the melting of Li₂CO₃ can encapsulate and wet oxide particles, promoting the dissolution and diffusion of oxide particles, resulting in ceramic densification. In the later stages of sintering, Li ions are drawn back into the main lattice for doping modification, and small-sized Li ions replace B sites to form acceptor doping. Attached Figure Description

[0028] Figure 1 SEM image of the piezoelectric ceramic material prepared in Example 2;

[0029] Figure 2 SEM image of the piezoelectric ceramic material prepared in Example 10;

[0030] Figure 3 The XRD diffraction patterns of the piezoelectric ceramic materials prepared in Examples 1, 3 and 10 are shown. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0032] The doping of high-valence W and Nb ions may enable Pb at the A site to... 2+The shift in charge further alters the lattice structure and symmetry, thus affecting the performance of piezoelectric ceramics. Simultaneously, defects such as oxygen vacancies are introduced to maintain charge balance, influencing charge distribution and polarization behavior within the crystal. The presence of oxygen vacancies can act as charge compensation centers, regulating the internal electric field distribution, promoting the movement of polarization domain walls and polarization reversal, thereby improving material performance.

[0033] In addition, doping elements such as Zn, Ni, Nb, Mg, and W can affect the polarization behavior of materials by changing the electronic structure and lattice vibration modes of crystals, thereby improving the piezoelectric and dielectric properties of materials.

[0034] In the following examples and comparative examples, the Pb source is Pb3O4, the Zr source is ZrO2, the Ti source is TiO2, the Nb source is Nb2O5, the Zn source is ZnO, the Ni source is NiO, the Mg source is MgO, the W source is WO3, and the Mn source is MnO2.

[0035] In the following examples and comparative examples, the medium used in wet ball milling is water, and the grinding balls are zirconium balls.

[0036] In the following examples and comparative examples, the adhesive is an aqueous solution of polyvinyl alcohol, and the content of polyvinyl alcohol in the aqueous solution is 15 wt%.

[0037] Example 1 (for comparison)

[0038] A method for preparing a piezoelectric ceramic material (PZT-PNN-PMW structure) includes: mixing Pb source, Zr source, Ti source, Nb source, Ni source, Mg source and W source, wet ball milling until homogeneous (wet ball milling to particle size D50=0.7μm), drying to moisture content <1%, pre-calcining at 850℃ for 4h in air atmosphere to obtain a pre-calcined material; mixing the sintering aid Li2CO3 with the pre-calcined material, wet ball milling until homogeneous to obtain a mixture with a particle size of 500~700nm, drying to moisture content <0.3% to obtain the piezoelectric ceramic material; granulating (granulation using a binder, the mass of the binder being 10wt% of the mass of the piezoelectric ceramic material); pressing and molding (performed in a tablet press at a pressure of 4MPa); and sintering at 950℃ for 4h in air atmosphere. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃), wherein, by molar fraction, the ratio of Pb in the Pb source, Zr in the Zr source, Ti in the Ti source, Nb in the Nb source, Ni in the Ni source, Mg in the Mg source, and W in the W source was 1:0.5(1-xy):0.5(1-xy): : : : a=1, x=0.09, y=0.03, the mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Ni source, Mg source and W source, M=0.5.

[0039] Example 6 (for comparison)

[0040] A method for preparing a piezoelectric ceramic (PZT-PZN-PMW structure) includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source, Mg source and W source, wet ball milling until homogeneous (wet ball milling to particle size D50=0.7μm), drying to moisture content <1%, pre-firing at 850℃ for 4h in air atmosphere to obtain a pre-fired synthesized material; mixing a sintering aid Li2CO3 with the pre-fired synthesized material, wet ball milling until homogeneous to obtain a mixture with a particle size of 500~700nm, drying to moisture content <0.3% to obtain a piezoelectric ceramic material; granulating (granulation using a binder, the mass of the binder being 10wt% of the mass of the piezoelectric ceramic material); pressing and molding (performed in a tablet press at a pressure of 4MPa); and sintering at 950℃ for 4h in air atmosphere. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃). The ratio of Pb in the Pb source, Zr in the Zr source, Ti in the Ti source, Nb in the Nb source, Zn in the Zn source, Mg in the Mg source, and W in the W source, by molar fraction, was 1:0.5(1-xy):0.5(1-xy). : : : a=0, x=0.09, y=0.03, the mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Mg source and W source, M=0.5.

[0041] Examples 2-5 and Examples 7-13

[0042] A method for preparing a piezoelectric ceramic (PZT-PZN-PNN-PMW structure) includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source, wet ball milling until homogeneous (wet ball milling to particle size D50=0.7μm), drying to moisture content <1%, pre-firing at 850℃ for 4h in air atmosphere to obtain a pre-fired synthesized material; mixing a sintering aid Li2CO3 with the pre-fired synthesized material, wet ball milling until homogeneous to obtain a mixture with a particle size of 500~700nm, drying to moisture content <0.3% to obtain the piezoelectric ceramic material; granulating (granulation using a binder, the mass of the binder being 10wt% of the mass of the piezoelectric ceramic material); pressing and molding (performed in a tablet press at a pressure of 4MPa); and sintering at 950℃ for 4h in air atmosphere. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃). The ratio of Pb in the Pb source, Zr in the Zr source, Ti in the Ti source, Nb in the Nb source, Zn in the Zn source, Ni in the Ni source, Mg in the Mg source, and W in the W source, by molar fraction, was 1:0.5(1-xy):0.5(1-xy). : : : : The mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source, and x, y, a and M are shown in Table 1.

[0043] Table 1

[0044]

[0045] Comparative Example 1

[0046] A piezoelectric ceramic (PZT-PZN-PNN structure, 0.83Pb(Zr)) 0.5 Ti 0.5 O3-0.17Pb((Ni 0.4 Zn 0.6 ) 1 / 3Nb 2 / 3The preparation method of (O3+Li2O) includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source and Ni source, wet ball milling until uniform (wet ball milling to particle size D50=0.7μm), drying to moisture <1%, pre-calcining at 850℃ for 4h in air atmosphere to obtain pre-calcined synthesized material, mixing sintering aid Li2CO3 with pre-calcined synthesized material, wet ball milling until uniform to obtain a mixture with a particle size of 500~700nm, drying to moisture <0.3% to obtain piezoelectric ceramic material, granulating (granulation using a binder, the mass of the binder being 10wt% of the mass of the piezoelectric ceramic material), pressing and molding (carried out in a tablet press with a pressure of 4MPa), and sintering at 950℃ for 4h in air atmosphere. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃). The ratio of Pb in Pb source, Zr in Zr source, Ti in Ti source, Nb in Nb source, Zn in Zn source, and Ni in Ni source by molar fraction was 1:0.415:0.415:0.113:0.034:0.023. The mass of Li2CO3 was 0.5% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, and Ni source.

[0047] Comparative Example 2

[0048] A method for preparing a piezoelectric ceramic (PZT-PZN-PNN-PMW structure) is basically the same as that in Example 11, except that the sintering aid Li2CO3 is not added.

[0049] The piezoelectric ceramic prepared in Comparative Example 2 was not fully sintered and could not be used for subsequent testing.

[0050] Comparative Example 3

[0051] A method for preparing a piezoelectric ceramic (PZT-PZN-PNN-PMW structure) is basically the same as that in Example 2, except that a=0.4, x=0.18, and y=0.02.

[0052] Comparative Example 4

[0053] A piezoelectric ceramic (PZT-PZN-PNN-PMN structure, 0.83Pb(Zr)) 0.5 Ti 0.5 O3-0.15Pb((Ni 0.4 Zn 0.6 ) 1 / 3 Nb 2 / 3 O3-0.02Pb(Mg) 1 / 2 Nb 1 / 2The preparation method of Pb, Zr, Ti, Nb, Zn, Ni, and Mg sources includes: mixing Pb, Zr, Ti, Nb, Zn, Ni, and Mg sources, wet ball milling until homogeneous (particle size D50 = 0.7 μm), drying to a moisture content of <1%, and pre-calcining at 850°C for 4 hours in air to obtain a pre-calcined material; mixing the sintering aid Li2CO3 with the pre-calcined material, wet ball milling until homogeneous to obtain a mixture with a particle size of 500-700 nm, drying to a moisture content of <0.3% to obtain a piezoelectric ceramic material; granulating (granulation using a binder, the mass of which is 10 wt% of the mass of the piezoelectric ceramic material); pressing and molding (performed in a tablet press at a pressure of 4 MPa); and sintering at 950°C for 4 hours in air. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃). The ratio of Pb in Pb source, Zr in Zr source, Ti in Ti source, Nb in Nb source, Zn in Zn source, Ni in Ni source, and Mg in Mg source was 1:0.415:0.415:0.11:0.03:0.02:0.01 by molar proportions. The mass of Li2CO3 was 0.5% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, and Mg source.

[0054] Comparative Example 5

[0055] A piezoelectric ceramic (PZT-PZN-PNN-PMW structure, 0.83Pb(Zr)) 0.5 Ti 0.5 O3-0.15Pb((Ni 0.4 Zn 0.6 ) 1 / 3 Nb 2 / 3 O3-0.02Pb(Mn) 1 / 2 W 1 / 2The preparation method of Pb, Zr, Ti, Nb, Zn, Ni, Mn and W sources includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mn source and W source, wet ball milling until homogeneous (wet ball milling to particle size D50=0.7μm), drying to moisture content <1%, and pre-calcining at 850℃ for 4h in air atmosphere to obtain pre-calcined material; mixing sintering aid Li2CO3 with pre-calcined material, wet ball milling until homogeneous to obtain a mixture with a particle size of 500~700nm, drying to moisture content <0.3% to obtain piezoelectric ceramic material; granulating (granulation using a binder, the mass of the binder being 10wt% of the mass of the piezoelectric ceramic material); pressing and molding (performed in a tablet press at a pressure of 4MPa); and sintering at 950℃ for 4h in air atmosphere. Piezoelectric ceramics were obtained by polarizing in silicone oil (polarization field strength of 3KV / mm, polarization temperature of 120℃). The ratio of Pb in Pb source, Zr in Zr source, Ti in Ti source, Nb in Nb source, Zn in Zn source, Ni in Ni source, Mn in Mn source, and W in W source, by molar fraction, was 1:0.415:0.415:0.1:0.03:0.02:0.01:0.01. The mass of Li2CO3 was 0.5% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mn source, and W source.

[0056] The results of the piezoelectric ceramics prepared in Examples 1-13 and Comparative Examples 1-5 are as follows (piezoelectric constant (d) 33 Unless otherwise specified, dielectric loss and mechanical quality factor are obtained by testing at room temperature (20~25℃).

[0057] Table 2

[0058]

[0059] Figure 1 This is a SEM image of the piezoelectric ceramic material prepared in Example 2. Figure 2 SEM image of the piezoelectric ceramic material prepared in Example 10.

[0060] Figure 3 The XRD diffraction patterns of the piezoelectric ceramic materials prepared in Examples 1, 3, and 10 are shown below. Figure 3 It can be seen that the strongest diffraction peak corresponds to the (110) crystal plane, while the (100) diffraction peak is relatively weak, indicating that the piezoelectric ceramic is a typical perovskite structure. At the same time, no diffraction peaks of pyrochlore or other impurities were observed in the XRD pattern, indicating that the doping element was B-site doped according to the formula design and completely entered the crystal lattice.

[0061] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A piezoelectric ceramic, characterized in that, include: A solid solution formed by PZT, PZN-PNN, and PMW, with Li doped in the solid solution. PZN-PNN is a solid solution formed by lead zinc niobate and lead nickel niobate. The structural formula of PZN-PNN is Pb((Ni a Zn 1-a ) 1 / 3 Nb 2 / 3 The structural formula of Pb(Zr)O3 and PZT is Pb(Zr)O3. 0.5 Ti 0.5 The structural formula of Pb(Mg)O3,PMW is Pb(Mg) 1 / 2 W 1 / 2 O3, in which, by molar fraction, the ratio of PZT, PZN-PNN and PMW is (1-xy):x:y, x=0.14, y=0.02, a=0.4; The preparation method of piezoelectric ceramics includes: mixing Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source until homogeneous, pre-firing at 850℃ for 4 hours in air atmosphere to obtain pre-fired synthesized material, mixing Li2CO3 and the pre-fired synthesized material until homogeneous to obtain piezoelectric ceramic material, granulating, pressing and molding, sintering at 950℃ for 4 hours in air atmosphere, polarizing in silicone oil to obtain piezoelectric ceramics, wherein the polarization field strength is 3KV / mm, the polarization temperature is 120℃, and the ratio of Pb in Pb source, Zr in Zr source, Ti in Ti source, Nb in Nb source, Zn in Zn source, Ni in Ni source, Mg in Mg source and W in W source by molar fraction is 1:0.5(1-xy):0.5(1-xy): : : : : The mass of Li2CO3 is M% of the sum of the masses of Pb source, Zr source, Ti source, Nb source, Zn source, Ni source, Mg source and W source, M=0.

5.

2. The piezoelectric ceramic according to claim 1, characterized in that, Granulation uses a binder, the mass of which is 8-15 wt% of the piezoelectric ceramic material.

3. The piezoelectric ceramic according to claim 2, characterized in that, The adhesive is an aqueous solution of polyvinyl alcohol, and the content of polyvinyl alcohol in the aqueous solution is 10~20wt%.

Images