Nano-Ag composite PZNNT-based piezoelectric ceramic and preparation method thereof

Abstract

The invention discloses a nano Ag composite PZNNT-based piezoelectric ceramic and a preparation method thereof, the chemical composition of the piezoelectric ceramic is 0.83 Pb (Zr1 / 2Ti1 / 2) O < 3 >-0.11 Pb (Zn1 / 3Nb2 / 3) O < 3 >-0.06 Pb (Ni1 / 3Nb2 / 3) O < 3-x > wt% Ag, 0 lt; x is less than or equal to 4; wherein 0.83 Pb (Zr < 1 / 2 > Ti < 1 / 2 >) O < 3 >-0.11 Pb (Zn < 1 / 3 > Nb < 2 / 3 >) O < 3 >-0.06 Pb (Ni < 1 / 3 > Nb < 2 / 3 >) O < 3 > is matrix ceramic powder, x represents the mass percent of nano Ag in the matrix ceramic powder, and abbreviated is PZNNT-xwt% Ag; according to the invention, the nano Ag is doped in the PZNNT-based piezoelectric ceramic matrix powder, and different nano Ag contents and particle sizes are set, so that the relative dielectric constant at room temperature is reduced while the piezoelectric strain constant is improved, and the nano Ag composite PZNNT-based piezoelectric ceramic with excellent piezoelectric property, relatively low dielectric loss and high energy conversion factor is obtained; the preparation method disclosed by the invention is simple to operate and relatively low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic-based piezoelectric conversion materials, and in particular to a nano-Ag composite PZNNT-based piezoelectric ceramic and a preparation method thereof. Background Art

[0002] Piezoelectric material is a functional material that can realize the mutual conversion between mechanical energy and electrical energy. In piezoelectric energy harvesting technology, it can convert useless or waste energy in the environment into electrical energy, providing a highly potential solution for the continuous power supply needs of wireless sensors. The performance indicators for evaluating piezoelectric materials are dielectric properties and piezoelectric properties. In recent years, it has become a research hotspot to continuously improve and improve the energy density of piezoelectric materials so that they can gradually meet the application needs of piezoelectric energy harvesters. According to the different components of piezoelectric ceramics, they can be divided into: lead-based piezoelectric ceramics and lead-free piezoelectric ceramics. The polycrystalline piezoelectric ceramics currently used in piezoelectric energy harvesters are mainly lead zirconate titanate-based piezoelectric ceramics. Compared with BaTiO 3 Base, (Na,K)NbO 3 PZT-based piezoelectric ceramics have better piezoelectric and dielectric properties. 1 / 2 Ti 1 / 2 ) 3 -Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -Pb(Ni 1 / 3 Nb 2 / 3 ) 3 (PZNNT)-based ceramic materials have attracted widespread attention due to their good temperature stability and high piezoelectric constant.

[0003] The energy harvesting factor is an important parameter of piezoelectric ceramics used in piezoelectric energy harvesters. The method to improve the energy conversion factor is to increase the piezoelectric strain constant d of the piezoelectric material by doping oxides. 33 value; or by adding a low relative dielectric constant ε r Relaxor ferroelectrics (Pb(In 1 / 2 Nb 1 / 2 ) 3 ), the second phase (ZnAl 2 O 4 ) Increase the piezoelectric voltage constant g of the material 33 At present, the piezoelectric strain constant d of commercial piezoelectric ceramics such as Morgan Electroceramics' PZT701 piezoelectric ceramics is 33 and energy conversion factor d 33 ×g 33 They are 153pC / N and 6273×10-15 m 2 / N; The Uchino research group at the University of Pennsylvania in the United States systematically studied the effects of doping and substitution of antimony, lithium, and manganese ions on the properties of PZNNT-based piezoelectric ceramics. Its piezoelectric strain constant d 33 is 239 pC / N, the relative dielectric constant ε r is 739, and the energy conversion factor d 33 ×g 33 is 8733×10 - 15 m 2 / N.

[0004] Facing the urgent demand of current piezoelectric energy harvesting devices for high-performance piezoelectric ceramics, it is urgent to further improve the energy conversion factor of piezoelectric ceramic materials. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a nano-Ag composite PZNNT-based piezoelectric ceramic and its preparation method. By doping nano-Ag in the PZNNT-based piezoelectric ceramic matrix powder and setting different nano-Ag contents and particle sizes, a nano-Ag composite PZNNT-based piezoelectric ceramic is obtained. Compared with the currently reported lead-based piezoelectric ceramics, this piezoelectric ceramic has excellent piezoelectric properties, low dielectric loss, and a high energy conversion factor, and has a very broad application prospect in the preparation of high-performance piezoelectric energy harvesting devices, and is an excellent candidate material in the field of piezoelectric energy harvesting.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of this piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 )O 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 )O 3 -xwt% Ag, 0 < x ≤ 4; wherein, 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 )O 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 )O 3is the matrix ceramic powder, and x represents the mass percentage of nano-Ag in the matrix ceramic powder, abbreviated as PZNNT-xwt% Ag.

[0008] When 0 < x ≤ 4, the particle size of nano-Ag is 80 - 200 nm, and when x = 1, the particle size of nano-Ag is 50 - 500 nm.

[0009] A preparation method of nano-Ag composite PZNNT-based piezoelectric ceramics includes the following steps:

[0010] Step 1, prepare PZNNT calcined powder;

[0011] According to the chemical formula of 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 )O 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 )O 3 , weigh a certain amount of PbO, TiO 2 , ZrO 2 , ZnO, Nb 2 O 5 , Ni(CH 3 COO) 2 ·4H 2 O to obtain a mixed raw material. The mixed raw material is ball-milled, dried, ground, sieved and then calcined to obtain PZNNT calcined powder;

[0012] Step 2, prepare PZNNT-Ag ceramic green body;

[0013] Mix and ball-mill the PZNNT calcined powder obtained in Step 1 and nano-Ag powder, then grind, granulate and dry-press to form a PZNNT-xwt% Ag ceramic green body;

[0014] The mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is greater than 0wt% and less than or equal to 4wt%, and the particle size of the nano-Ag is 80 - 200 nm;

[0015] Or, the mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is 1wt%, and the particle size of the nano-Ag is 50 - 500 nm;

[0016] Step 3, sinter the PZNNT-Ag ceramic green body;

[0017] The PZNNT-xwt%Ag ceramic green body obtained in step 2 is debound and then sintered to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic; a silver electrode is coated on the surface of the nano-Ag composite PZNNT-based piezoelectric ceramic, and polarization treatment is carried out.

[0018] In step 1, the calcination temperature is 700 - 800 °C, the heat preservation time is 1 - 3 h, and the heating rate is 2 - 10 °C / min.

[0019] In steps 1 and 2, the ball milling medium is anhydrous ethanol, the ball milling speed is 200 - 300 r / min, and the time is 10 - 14 h.

[0020] In step 2, dry pressing is carried out under an axial pressure of 6 - 10 MPa for 3 - 7 min for pressure holding.

[0021] In step 3, the debinding conditions are: heat preservation at 450 - 550 °C for 0.5 - 2 h, the sintering temperature is 940 - 980 °C, the heat preservation time is 1 - 3 h, and the heating rate is 2 - 10 °C / min.

[0022] In step 3, the surface of the sintered nano-Ag composite PZNNT-based piezoelectric ceramic is polished, and then a silver electrode is coated.

[0023] In step 3, the polarization process is: the polarization temperature is 100 - 140 °C, the polarization field strength is 2 - 5 kV / mm, and the polarization time is 20 - 60 min.

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

[0025] 1. The present invention uses a solid-phase method to prepare PZNNT calcined powder, and then nano-Ag is doped into the PZNNT calcined powder, which changes the intragranular structure, realizes the decoupling of the relative dielectric constant and the piezoelectric strain constant in the piezoelectric ceramic, reduces the room-temperature relative dielectric constant while increasing the piezoelectric strain constant, and obtains a nano-Ag composite PZNNT-based piezoelectric ceramic with excellent piezoelectric properties, low dielectric loss, and high energy conversion factor.

[0026] 2. The present invention prepares a nano-Ag composite PZNNT-based piezoelectric ceramic, namely PZNNT-xwt%Ag, by doping nano-Ag with different contents or particle sizes. Among them, when 0 < x ≤ 4 and the particle size of nano-Ag is 80 - 200 nm, the room-temperature relative dielectric constant ε r is 1927 - 2100, the room-temperature dielectric loss tanδ is 0.0165 - 0.0198, the piezoelectric strain constant d 33 is 387 - 441 pC / N, and the energy conversion factor d 33 ×g 338097~11400×10 -15 m 2 / N; when x = 1, the nano-Ag particle size is 50-500nm, the room temperature relative dielectric constant of the piezoelectric ceramic material ε r is 2012~2047, the room temperature dielectric loss tanδ is 0.0201~0.0203, and the piezoelectric strain constant d 33 389~408pC / N, energy conversion factor d 33 ×g 33 8329~9349×10 -15 m 2 / N; It can be seen that the energy harvesting performance of nano-Ag composite PZNNT-based piezoelectric ceramics has been further improved, which is better than the currently reported lead-based piezoelectric ceramics. It has a very broad application prospect in the preparation of high-performance piezoelectric energy harvesting devices and is an excellent candidate material in the field of piezoelectric energy harvesting.

[0027] 3. The ceramic matrix used in the present invention is a quaternary PZNNT piezoelectric ceramic, which has a wide control range and high piezoelectric performance and excellent temperature stability, so that it can meet the high requirements of the working environment during the application process. In addition, the preparation method of the nano-Ag composite PZNNT-based piezoelectric ceramic material provided by the present invention is prepared by a traditional solid phase reaction method, which is simple to operate and has low cost. The nano-Ag used as a non-ferroelectric phase reduces the dielectric properties of the ceramic to a certain extent. A small amount of Ag + Entering the crystal lattice promotes grain growth and improves the density of the ceramic material. At the same time, it exhibits good piezoelectric properties and improves the energy harvesting factor of the ceramic material.

[0028] In summary, the present invention obtains nano-Ag composite PZNNT-based piezoelectric ceramics by doping nano-Ag into PZNNT-based piezoelectric ceramic matrix powder and setting different nano-Ag contents and particle sizes. Compared with the currently reported lead-based piezoelectric ceramics, the piezoelectric ceramics have excellent piezoelectric properties, lower dielectric loss and high energy conversion factor, and have very broad application prospects in the preparation of high-performance piezoelectric energy harvesting devices. It is an excellent candidate material in the field of piezoelectric energy harvesting. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD patterns of PZNNT-xw%Ag piezoelectric ceramics with different nano-Ag contents.

[0030] Figure 2 Density diagram of PZNNT-xw%Ag piezoelectric ceramics with different nano-Ag contents.

[0031] Figure 3The SEM images of PZNNT-xw%Ag piezoelectric ceramics with different nano-Ag contents and the corresponding particle size distribution diagram, where: Figure 3 (a) is undoped, Figure 3 (b) is the doping mass percentage of 0.5wt% nano-Ag, Figure 3 (c) is the doping mass percentage of 1wt% nano-Ag, Figure 3 (d) is the doping mass percentage of 2wt% nano-Ag, Figure 3 (e) is the doping mass percentage of 3wt% nano-Ag, Figure 3 (f) The doping mass percentage is 4wt% nano-Ag.

[0032] Figure 4 is the relative dielectric constant ε of PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents at room temperature r and dielectric loss tanδ.

[0033] Figure 5 is the piezoelectric strain constant d of PZNNT-xwt%Ag ceramics with different nano-Ag contents 33 and energy conversion factor d 33 ×g 33 .

[0034] Figure 6 XRD patterns of PZNNT-1wt%Ag piezoelectric ceramics with different nano-Ag particle sizes.

[0035] Figure 7 Density diagram of PZNNT-1wt%Ag piezoelectric ceramics with different nano-Ag particle sizes.

[0036] Figure 8 The SEM images and particle size distribution diagram of PZNNT-1wt%Ag piezoelectric ceramics with different nano-Ag particle sizes are shown in Figure 2. Figure 8 (a) is the nano-Ag doped with a particle size of 50 nm. Figure 8 (b) is the nano-Ag doped with a particle size of 100 nm. Figure 8 (c) is the doping nano-Ag with a particle size of 500nm

[0037] Fig. 9 is the relative dielectric constant ε of PZNNT-1wt%Ag piezoelectric ceramics with different Ag nanoparticle sizes at room temperature r and dielectric loss tanδ.

[0038] Fig.10 is the piezoelectric strain constant d of PZNNT-1wt%Ag piezoelectric ceramics with different Ag nanoparticle sizes 33 and energy conversion factor d 33 ×g 33。 Detailed implementation manners

[0039] The technical solution of the invention will be further introduced below in conjunction with the accompanying drawings and embodiments.

[0040] The main raw materials used in the experiment were analytical pure PbO (purity 99.0%, Sinopharm Group), TiO 2 (purity 98.0%, Sinopharm Group), ZrO 2 (purity 99.0%, Sinopharm Group), ZnO (purity 99.0%, Sinopharm Group), Nb 2 O 5 (purity 99.5%, Sinopharm Group), Ni(CH 3 COO) 2 ·4H 2 O (purity 98.0%, Sinopharm Group), nano-Ag (purity 99.9%, Shanghai Pantian Powder Materials Co., Ltd.), the ball milling medium was anhydrous ethanol (purity 99.7%, Tianjin Damao Reagent), and polyvinyl alcohol (degree of polymerization 1750±50, Sinopharm Group).

[0041] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 )O 3 -0.06Pb(Ni 1 / 3 Nb 2 / ) O 3 -xwt%Ag, 0 < x ≤ 4, where 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 )O 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 )O 3 is the matrix ceramic powder, x represents the mass percentage of nano-Ag in the matrix ceramic powder, abbreviated as PZNNT-xwt%Ag.

[0042] When 0 < x ≤ 4 and the particle size of nano-Ag is 80 - 200 nm, the room temperature relative dielectric constant ε r of the nano-Ag composite PZNNT-based piezoelectric ceramic material (PZNNT-xwt%Ag) is 1927 - 2100, the room temperature dielectric loss tanδ is 0.0165 - 0.0198, and the piezoelectric strain constant d 33387~441pC / N, energy conversion factor d 33 ×g 33 8097~11400×10 -15 m 2 / N.

[0043] When x=1 and the nano-Ag particle size is 50-500nm, the room temperature relative dielectric constant ε of the nano-Ag composite PZNNT-based piezoelectric ceramic material (PZNNT-1wt%Ag) is r is 2012~2047, the room temperature dielectric loss tanδ is 0.0201~0.0203, and the piezoelectric strain constant d 33 389~408pC / N, energy conversion factor d 33 ×g 33 8329~9349×10 -15 m 2 / N.

[0044] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0045] Step 1: Preparation of PZNNT calcined powder:

[0046] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2O, obtain a mixed raw material, put the mixed raw material and anhydrous ethanol into a ball mill and mill for 10-14 hours at 200-300 rpm to obtain a slurry; the ball milling medium is zirconium balls, and the mass ratio is mixed raw material: zirconium balls: anhydrous ethanol = 1:3:1; the ball-milled slurry is placed in an oven and dried at 50-80°C for 4-6 hours to obtain a block mixture; the dried block mixture is ground with an agate mortar, and sieved to obtain a mixed powder with a sieve aperture of 100-300 mesh; then the mixed powder is placed in an alumina crucible and covered with a crucible cover, and placed in a muffle furnace for calcination to obtain PZNNT calcined powder; the calcination temperature is 700-800°C, the insulation time is 1-3h, and the heating rate is 2-10°C / min;

[0047] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0048] The PZNNT calcined powder and nano-Ag powder obtained in step 1 are placed in a ball mill, anhydrous ethanol is added, and the mixture is ball milled at 200-300 rpm for 10-14 hours, and then dried at 50-80°C for 4-6 hours to obtain PZNNT-xwt%Ag powder; polyvinyl alcohol is added to the PZNNT-xwt%Ag powder for grinding and granulation, and the mixture is passed through 100 mesh and 200 mesh sieves to obtain 75-150 μm PZNNT-xwt%Ag powder; a manual powder tablet press is used for dry pressing to obtain a PZNNT-xwt%Ag ceramic embryo, and the process conditions for dry pressing are: holding the mixture under an axial pressure of 6-10 MPa for 3-7 minutes;

[0049] The mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is greater than 0wt% and less than or equal to 4wt%, and the particle size of the nano-Ag is 80-200nm;

[0050] Alternatively, the mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is 1wt%, and the particle size of the nano-Ag is 50-500nm;

[0051] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0052] The PZNNT-xwt% Ag ceramic embryo obtained in step 2 is placed in a muffle furnace for debinding and then sintered to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, wherein the debinding conditions are as follows: keeping warm at 450-550°C for 0.5-2h, sintering temperature of 940-980°C, keeping warm time of 1-3h, and heating rate of 2-10°C / min; using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper to grind and polish the surface of the sintered body after sintering to make a 12mm×1mm ceramic disc; then coating a silver electrode on the surface of the polished ceramic disc and performing polarization treatment, and the polarization process is a polarization temperature of 100-140°C, a polarization field strength of 2-5kV / mm, and a polarization time of 20-60min.

[0053] Example 1

[0054] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -0.5wt%Ag.

[0055] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0056] Step 1: Preparation of PZNNT calcined powder:

[0057] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 200 rpm for 10 h to obtain a slurry; dry the ball-milled slurry at 50° C. for 4 h, grind, and sieve to obtain a mixed powder with a sieve aperture of 100 mesh; then calcine the mixed powder at 700° C. for 1 h to obtain PZNNT calcined powder; the heating rate is 2° C. / min;

[0058] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0059] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 200 rpm for 10 h, and then dried at 50°C for 4 h to obtain PZNNT-0.5wt%Ag powder; the PZNNT-0.5wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150μm PZNNT-0.5wt%Ag powder; then dry-pressed under an axial pressure of 6MPa for 3min to obtain a PZNNT-0.5wt%Ag ceramic embryo; the nano-Ag particle size is 80nm;

[0060] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0061] The PZNNT-0.5wt% Ag ceramic embryo obtained in step 2 is kept at 450°C for 0.5h for debinding, and then sintered at 940°C for 1h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 2°C / min; the surface of the sintered body after sintering is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 100°C, a polarization field strength of 2kV / mm, and a polarization time of 20min.

[0062] Example 2

[0063] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -1wt%Ag.

[0064] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0065] Step 1: Preparation of PZNNT calcined powder:

[0066] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2 O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 250 rpm for 12 h to obtain a slurry; dry the ball-milled slurry at 60° C. for 5 h, grind, and sieve to obtain a mixed powder with a mesh size of 200 mesh; then calcine the mixed powder at 750° C. for 2 h to obtain PZNNT calcined powder; the heating rate is 5° C. / min;

[0067] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0068] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 12 h, and then dried at 60° C. for 5 h to obtain PZNNT-1wt%Ag powder; the PZNNT-1wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150 μm PZNNT-1wt%Ag powder; and then dry-pressed under an axial pressure of 8 MPa for 5 min to obtain a PZNNT-1wt%Ag ceramic embryo; the nano-Ag particle size is 200 nm;

[0069] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0070] The PZNNT-1wt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 120°C, a polarization field strength of 3kV / mm, and a polarization time of 30min.

[0071] Example 3

[0072] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -2wt%Ag.

[0073] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0074] Step 1: Preparation of PZNNT calcined powder:

[0075] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 250 rpm for 12 h to obtain a slurry; dry the ball-milled slurry at 70° C. for 5 h, grind, and sieve to obtain a mixed powder with a sieve aperture of 150 mesh; then calcine the mixed powder at 750° C. for 2 h to obtain PZNNT calcined powder; the heating rate is 2° C. / min;

[0076] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0077] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 12 h, and then dried at 70°C for 5 h to obtain PZNNT-2wt%Ag powder; the PZNNT-2wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150 μm PZNNT-2wt%Ag powder; then dry-pressed under an axial pressure of 7 MPa for 4 min to obtain a PZNNT-2wt%Ag ceramic embryo; the nano-Ag particle size is 150 nm;

[0078] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0079] The PZNNT-2wt% Ag ceramic embryo obtained in step 2 is kept at 450°C for 1h for debinding, and then sintered at 940°C for 1h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 2°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 110°C, a polarization field strength of 2.5kV / mm, and a polarization time of 40min.

[0080] Example 4

[0081] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -3wt%Ag

[0082] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0083] Step 1: Preparation of PZNNT calcined powder:

[0084] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2 O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 300 rpm for 14 h to obtain a slurry; dry the ball-milled slurry at 80° C. for 6 h, grind, and sieve to obtain a mixed powder with a sieve aperture of 250 mesh; then calcine the mixed powder at 800° C. for 3 h to obtain PZNNT calcined powder; the heating rate is 10° C. / min;

[0085] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0086] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 300 rpm for 14 h, and then dried at 80°C for 6 h to obtain PZNNT-3wt%Ag powder; the PZNNT-3wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150μm PZNNT-3wt%Ag powder; then dry-pressed under an axial pressure of 9MPa for 6 min to obtain a PZNNT-3wt%Ag ceramic embryo; the nano-Ag particle size is 150nm;

[0087] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0088] The PZNNT-3wt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1.5h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 130°C, a polarization field strength of 4kV / mm, and a polarization time of 50min.

[0089] Example 5

[0090] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -4wt%Ag.

[0091] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0092] Step 1: Preparation of PZNNT calcined powder:

[0093] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 250 rpm for 14 h to obtain a slurry; dry the ball-milled slurry at 70° C. for 6 h, grind, and sieve to obtain a mixed powder with a sieve aperture of 300 mesh; then calcine the mixed powder at 800° C. for 3 h to obtain PZNNT calcined powder; the heating rate is 10° C. / min;

[0094] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0095] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 14 h, and then dried at 70°C for 6 h to obtain PZNNT-4wt%Ag powder; the PZNNT-4wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150μm PZNNT-4wt%Ag powder; then dry-pressed under an axial pressure of 10MPa for 7 min to obtain a PZNNT-xwt%Ag ceramic embryo; the nano-Ag particle size is 200nm;

[0096] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0097] The PZNNT-xwt% Ag ceramic embryo obtained in step 2 is kept at 550°C for 2h for debinding, and then sintered at 980°C for 3h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 10°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 140°C, a polarization field strength of 5kV / mm, and a polarization time of 60min.

[0098] Example 6

[0099] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -1wt%Ag.

[0100] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0101] Step 1: Preparation of PZNNT calcined powder:

[0102] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2 O, obtain a mixed raw material, put the mixed raw material and anhydrous ethanol into a ball mill and ball mill at 250 rpm for 12 hours to obtain a slurry; dry the ball-milled slurry at 60° C. for 5 hours, grind, and sieve to obtain a mixed powder with a mesh size of 200 mesh; then calcine the mixed powder at 750° C. for 2 hours to obtain PZNNT calcined powder; the heating rate is 5° C. / min;

[0103] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0104] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 12 h, and then dried at 60° C. for 5 h to obtain PZNNT-1wt%Ag powder; the PZNNT-1wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150 μm PZNNT-1wt%Ag powder; dry-pressing is performed under an axial pressure of 8 MPa for 5 min to obtain a PZNNT-xwt%Ag ceramic embryo; the nano-Ag particle size is 50 nm;

[0105] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0106] The PZNNT-1wt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 120°C, a polarization field strength of 3kV / mm, and a polarization time of 30min.

[0107] Example 7

[0108] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -1wt%Ag.

[0109] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0110] Step 1: Preparation of PZNNT calcined powder:

[0111] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2O, obtain a mixed raw material, put the mixed raw material and anhydrous ethanol into a ball mill and ball mill at 250 rpm for 12 hours to obtain a slurry; dry the ball-milled slurry at 60° C. for 5 hours, grind, and sieve to obtain a mixed powder with a mesh size of 200 mesh; then calcine the mixed powder at 750° C. for 2 hours to obtain PZNNT calcined powder; the heating rate is 5° C. / min;

[0112] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0113] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 12 h, and then dried at 60° C. for 5 h to obtain PZNNT-1wt%Ag powder; the PZNNT-1wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150 μm PZNNT-1wt%Ag powder; and then dry-pressed under an axial pressure of 8 MPa for 5 min to obtain a PZNNT-1wt%Ag ceramic embryo, wherein the nano-Ag particle size is 100 nm;

[0114] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0115] The PZNNT-1wt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 120°C, a polarization field strength of 3kV / mm, and a polarization time of 30min.

[0116] Example 8

[0117] A nano-Ag composite PZNNT-based piezoelectric ceramic, the chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 -1wt%Ag.

[0118] A method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic comprises the following steps:

[0119] Step 1: Preparation of PZNNT calcined powder:

[0120] According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 ) 3 -0.11Pb(Zn 1 / 3 Nb 2 / 3 ) 3 -0.06Pb(Ni 1 / 3 Nb 2 / 3 ) 3 Weigh a certain amount of PbO, TiO 2 、ZrO 2 、ZnO、Nb 2 O 5 、Ni(CH 3 COO 2 ·4H 2 O, obtain a mixed raw material, ball-mill the mixed raw material and anhydrous ethanol at 250 rpm for 12 h to obtain a slurry; dry the ball-milled slurry at 60° C. for 5 h, grind, and sieve to obtain a mixed powder with a mesh size of 200 mesh; then calcine the mixed powder at 750° C. for 2 h to obtain PZNNT calcined powder; the heating rate is 5° C. / min;

[0121] Step 2: Preparation of PZNNT-Ag ceramic embryo:

[0122] The PZNNT calcined powder obtained in step 1 and the nano-Ag powder are mixed, anhydrous ethanol is added, and the mixture is ball-milled at 250 rpm for 12 h, and then dried at 60° C. for 5 h to obtain PZNNT-1wt%Ag powder; the PZNNT-1wt%Ag powder is ground and granulated, and passed through 100-mesh and 200-mesh sieves to obtain 75-150 μm PZNNT-1wt%Ag powder; then dry-pressed under an axial pressure of 8 MPa for 5 min to obtain a PZNNT-1wt%Ag ceramic embryo; the nano-Ag particle size is 500 nm;

[0123] Step 3, sintering the PZNNT-Ag ceramic embryo;

[0124] The PZNNT-xwt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 120°C, a polarization field strength of 3kV / mm, and a polarization time of 30min.

[0125] Comparative Example 1

[0126] The processes and parameters of Comparative Example 1 and Example 2 are the same, except that: in step 2, no nano-Ag is added, and only the PZNNT ceramic embryo is prepared.

[0127] The dielectric and piezoelectric properties of the polarized nano-Ag composite PZNNT-based piezoelectric ceramics were tested after standing for 24 hours, and the energy harvesting factor was calculated.

[0128] Figure 1 The XRD patterns of PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents are shown in Figure 2. Figure 1 It can be seen that the PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents prepared by the present invention are all pure perovskite phases, and no impurity phases such as pyrochlore appear; and when 2θ is in the range of 43° to 46°, the addition of nano-Ag affects the content of the rhombohedral-tetragonal phase. This is because when a small amount of Ag is doped, Ag is in the form of Ag. + Enter the crystal lattice in the form of A-site substitution Pb 2+ , causing the system lattice to distort and a transition from a rhombohedral phase to a tetragonal phase; when the mass percentage of Ag increases to x = 1wt%, it indicates that Ag + The solubility limit has been reached in the ceramic lattice; and as the Ag content continues to increase, Ag no longer enters the lattice in the form of ions, but is enriched at the grain boundaries in the form of a single substance, which has little effect on the rhombohedral-tetragonal phase transformation.

[0129] Figure 2 The density diagram of PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents is shown in Figure 2. Figure 2 It can be seen that when the doping density of nano-Ag is higher, the density of PZNNT-xwt%Ag piezoelectric ceramics shows an upward trend with the increase of nano-Ag doping amount, which improves the compactness of the piezoelectric ceramics.

[0130] Figure 3The SEM images of PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents and the corresponding particle size distribution diagram, where: Figure 3 (a) is undoped, Figure 3 (b) is the doping mass percentage of 0.5wt% nano-Ag, Figure 3 (c) is the doping mass percentage of 1wt% nano-Ag, Figure 3 (d) is the doping mass percentage of 2wt% nano-Ag, Figure 3 (e) is the doping mass percentage of 3wt% nano-Ag, Figure 3 (f) is the doping mass percentage of 4wt% nano-Ag; with the increase of nano-Ag content, the pores of PZNNT-xwt%Ag piezoelectric ceramics gradually decrease, and the piezoelectric ceramics show better compactness; its particle size increases first and then decreases, and the corresponding average particle size The sizes are 2.68μm, 3.64μm, 4.18μm, 3.36μm, 2.56μm, and 2.20μm respectively. The reason why the particle size of PZNNT-xwt%Ag piezoelectric ceramics increases is that when the content of nano-Ag is small, Ag is in the form of Ag. + The nano-Ag enters the PZNNT ceramic lattice in the form of, generating oxygen vacancies, promoting the transfer of substances and energy between reactants, improving sintering behavior, and inducing a significant increase in grain size. The increase in particle size is beneficial to the improvement of the piezoelectric properties of piezoelectric ceramics. However, when the mass percentage of nano-Ag exceeds 1wt%, the amount of nano-Ag added exceeds the solid solubility limit of PZNNT-based piezoelectric ceramics. Nano-Ag gathers at the ceramic grain boundary in the form of a single substance, thereby inhibiting the growth of ceramic grains, and the particle size of PZNNT-xwt%Ag piezoelectric ceramics gradually decreases.

[0131] Figure 4 is the relative dielectric constant ε of PZNNT-xwt%Ag piezoelectric ceramics with different nano-Ag contents at room temperature r and dielectric loss tanδ; Figure 4 It can be seen that with the increase of nano-Ag content, the relative dielectric constant ε r and dielectric loss tanδ show a trend of decreasing first and then increasing; when the nano-Ag content is 1wt%, the relative dielectric constant ε of the piezoelectric ceramics r The dielectric loss tanδ and dielectric loss tanδ are reduced to the lowest values, which are 1927 and 0.0165 respectively; the relative dielectric constant ε r The reduction of dielectric loss tanδ is more conducive to improving the efficiency of energy conversion, which is very beneficial for application scenarios that require efficient energy conversion; when the mass percentage of nano-Ag is less than 1wt%, due to Ag + The electronegativity of Pb (7.576eV) is much smaller than that of Pb 2+(15.032eV), which will affect the oxygen octahedron in the perovskite structure after substitution, and then affect the Ti 4+ The ion displacement eventually reduces the relative dielectric constant ε r and dielectric loss tanδ; when the mass percentage of nano-Ag is greater than 1wt%, with the increase of Ag content, Ag is dispersed in the form of a single substance, causing the percolation effect, which increases the relative dielectric constant ε of the composite material r ; At the same time, the presence of Ag single substance at the grain boundary generates free charges, resulting in an increase in dielectric loss tanδ.

[0132] Figure 5 is the piezoelectric strain constant d of PZNNT-xwt%Ag ceramics with different nano-Ag contents 33 and energy conversion factor d 33 ×g 33 ;Depend on Figure 5 It can be seen that with the increase of nano-Ag content, the piezoelectric strain constant d 33 and energy conversion factor d 33 ×g 33 They all rise first and then fall, among which the energy conversion factor d 33 ×g 33 All higher than 8097×10 -15 m 2 / N, when the content of nano-Ag is 1wt%, the energy conversion factor d 33 ×g 33 Reach the maximum, that is, 11400×10 -15 m 2 / N; When the content of nano-Ag exceeds 1wt%, the piezoelectric strain constant d 33 This is because a large amount of Ag is enriched at the grain boundaries, and the percolation effect will cause the impedance of the composite material to decrease, resulting in the deterioration of the piezoelectric performance. The energy conversion factor d 33 ×g 33 Also with the decrease.

[0133] Figure 6 The XRD patterns of PZNNT-1wt%Ag piezoelectric ceramics with different Ag nanoparticle sizes are shown in Figure 2. Figure 6 It can be seen that with the increase of nano-Ag particle size, the transition from tetragonal phase to trigonal phase occurs. This is because when small-sized nano-Ag is added, Ag + Easier to enter the lattice to replace Pb 2+However, when the nano-Ag particle size is too large, the nano-Ag will not be completely dissolved into the PZNNT, resulting in a transformation from the tetragonal phase to the rhombohedral phase; when the mass percentage of nano-Ag is 1wt% and the particle size is 100nm, the tetragonal phase and rhombohedral phase of the PZNNT-1wt%Ag piezoelectric ceramics coexist and are very close to the quasi-modular phase boundary (MPB), and the piezoelectric ceramics exhibit excellent piezoelectric properties near the quasi-modular phase boundary (MPB).

[0134] Figure 7 The density diagram of PZNNT-1wt%Ag piezoelectric ceramics with different Ag nanoparticle sizes is shown in Figure 2. Figure 7 It can be seen that with the increase of nano-Ag particle size, the density of PZNNT-1wt%Ag piezoelectric ceramics first increases and then decreases, and the density of piezoelectric ceramics after adding nano-Ag exceeds 7.6g / cm 3 Especially when the nano-Ag particle size is 100nm, the density of PZNNT-1wt%Ag piezoelectric ceramics reaches the maximum, i.e. 7.868g / cm 3 Better than PZT-based piezoelectric ceramics (6.0~7.5g / cm 3 ), indicating that the PZNNT-1wt%Ag piezoelectric ceramics prepared by the present invention have high compactness.

[0135] Figure 8 The SEM images and particle size distribution diagram of PZNNT-1wt%Ag piezoelectric ceramics with different nano-Ag particle sizes are shown in Figure 2. Figure 8 (a) is the nano-Ag doped with a particle size of 50 nm. Figure 8 (b) is the nano-Ag doped with a particle size of 100 nm. Figure 8 (c) is nano-Ag with a doping particle size of 500nm; Figure 8 It can be seen that with the increase of nano-Ag particle size, the average particle size of PZNNT-1wt%Ag piezoelectric ceramics also increases. They are 4.00 μm, 4.77 μm, and 4.85 μm, respectively, indicating that the density of the PZNNT-1wt% Ag piezoelectric ceramics prepared by the present invention is improved, which is more conducive to the improvement of the piezoelectric properties of the material.

[0136] Fig. 9 is the relative dielectric constant ε of PZNNT-1wt%Ag piezoelectric ceramics with different Ag nanoparticle sizes at room temperature r and dielectric loss tanδ; Fig. 9 It can be seen that with the increase of nano-Ag particle size, the relative dielectric constant ε of PZNNT-1wt%Ag piezoelectric ceramics rThe dielectric loss tanδ first decreases and then increases, which is attributed to the low dielectric constant of the Ag material itself. When the nano-Ag particle size is too large (500nm), the percolation effect will be aggravated, resulting in a relative dielectric constant ε r and dielectric loss tanδ increase; when the nano-Ag particle size is 100nm, the relative dielectric constant ε of PZNNT-1wt%Ag piezoelectric ceramics r and dielectric loss tanδ are reduced to the lowest values, which are 2012.49 and 0.0201 respectively; the relative dielectric constant ε r As well as the reduction of dielectric loss tanδ, it is more conducive to the improvement of energy conversion factor, so that the material has good electrical signal transmission performance and stability.

[0137] Fig.10 is the piezoelectric strain constant and energy conversion factor of PZNNT-1wt%Ag piezoelectric ceramics with different nano-Ag particle sizes; Fig.10 It can be seen that with the increase of nano-Ag particle size, the piezoelectric strain constant d 33 and energy conversion factor d 33 ×g 33 First increases and then decreases; among them, the energy conversion factor d 33 ×g 33 All higher than 8329×10 -15 m 2 / N, when the nano-Ag particle size is 100nm, the energy conversion factor d 33 ×g 33 Reaching the maximum, that is, 9349×10 -15 m 2 / N; When the nano-Ag particle size gradually increases, the piezoelectric strain constant d 33 and energy conversion factor d 33 ×g 33 The reason for the increase first and then decrease is related to the increase in grain size distribution caused by the excessive size of nano-Ag particles and the increase in microstructural inhomogeneity. By doping nano-Ag into PZNNT-based piezoelectric ceramics, the energy conversion factor of PZNNT-based piezoelectric ceramics is improved, which can meet the practical application requirements of energy harvesting devices.

Claims

1. A nano-Ag composite PZNNT-based piezoelectric ceramic, characterized in that: The chemical composition of the piezoelectric ceramic is: 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O3 - 0.11Pb(Zn 1 / 3 Nb 2 / 3 )O3 - 0.06Pb(Ni 1 / 3 Nb 2 / 3 )O3 - x wt% Ag, 0 < x ≤ 4; wherein, 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O3 - 0.11Pb(Zn 1 / 3 Nb 2 / 3 )O3 - 0.06Pb(Ni 1 / 3 Nb 2 / 3 )O3 is the matrix ceramic powder, and x represents the mass percentage of nano-Ag in the matrix ceramic powder.

2. The nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 1, characterized in that: When 0 < x ≤ 4, the particle size of nano-Ag is 80 - 200 nm; when x = 1, the particle size of nano-Ag is 50 - 500 nm.

3. A method for preparing nano-Ag composite PZNNT-based piezoelectric ceramics, characterized in that: It includes the following steps: Step 1, prepare PZNNT calcined powder; According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O3-0.11Pb(Zn 1 / 3 Nb 2 / 3 )O3-0.06Pb(Ni 1 / 3 Nb 2 / 3 )O3 chemical formula: Weigh a certain amount of PbO, TiO2, ZrO2, ZnO, Nb2O5, Ni(CH3COO)2·4H2O to obtain a mixed raw material, and perform ball milling, drying, grinding, sieving and calcining on the mixed raw material in sequence to obtain PZNNT calcined powder; Step 2, prepare PZNNT-Ag ceramic green body; Mix and ball-mill the PZNNT calcined powder obtained in Step 1 and nano-Ag powder, then grind, granulate and dry-press to form a PZNNT-xwt%Ag ceramic green body; The mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is greater than 0wt% and less than or equal to 4wt%, and the particle size of the nano-Ag is 80 - 200 nm; Or, the mass percentage (xwt%) of the nano-Ag in the PZNNT calcined powder is 1wt%, and the particle size of the nano-Ag is 50 - 500 nm; Step 3, sinter the PZNNT-Ag ceramic green body; Debind the PZNNT-xwt%Ag ceramic green body obtained in Step 2 and then sinter it to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic; coat the surface of the nano-Ag composite PZNNT-based piezoelectric ceramic with silver electrodes and perform polarization treatment.

4. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 1, the calcination temperature is 700 - 800 °C, the heat preservation time is 1 - 3 h, and the heating rate is 2 - 10 °C / min.

5. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 2, dry-press is performed under an axial pressure of 6 - 10 MPa and the pressure is maintained for 3 - 7 min.

6. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 1 and Step 2, the ball-milling medium is anhydrous ethanol, the ball-milling speed is 200 - 300 rpm, and the time is 10 - 14 h.

7. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 3, the debinding conditions are: heat preservation at 450 - 550 °C for 0.5 - 2 h, the sintering temperature is 940 - 980 °C, the heat preservation time is 1 - 3 h, and the heating rate is 2 - 10 °C / min.

8. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 3, the surface of the sintered nano-Ag composite PZNNT-based piezoelectric ceramic is polished, and then silver electrodes are coated.

9. The method for preparing a nano-Ag composite PZNNT-based piezoelectric ceramic according to claim 3, characterized in that: In Step 3, the polarization process is a polarization temperature of 100 - 140 °C, a polarization field strength of 2 - 5 kV / mm, and a polarization time of 20 - 60 min.

10. According to the preparation method of a nano-Ag composite PZNNT-based piezoelectric ceramic described in claim 3, it is characterized in that: Step 1, prepare PZNNT calcined powder: According to 0.83Pb(Zr 1 / 2 Ti 1 / 2 )O3-0.11Pb(Zn 1 / 3 Nb 2 / 3 )O3-0.06Pb(Ni 1 / 3 Nb 2 / 3 )O3's chemical formula: Weigh a certain amount of PbO, TiO2, ZrO2, ZnO, Nb2O5, Ni(CH3COO)2·4H2O to obtain a mixed raw material, put the mixed raw material and anhydrous ethanol into a ball mill and mill at 250 rpm for 12 h to obtain a slurry; dry the milled slurry at 60°C for 5 h, grind, and sieve to obtain a mixed powder with a sieve aperture of 200 mesh; Then calcine the mixed powder at 750 °C for 2 h to obtain PZNNT calcined powder; the heating rate is 5 °C / min; Step 2, prepare PZNNT-Ag ceramic green body: Mix the PZNNT calcined powder obtained in Step 1 and nano-Ag powder, add anhydrous ethanol and ball-mill at 250 rpm for 12 h, then dry at 60 °C for 5 h to obtain PZNNT-1wt%Ag powder; grind and granulate the PZNNT-1wt%Ag powder, pass through 100-mesh and 200-mesh sieves to obtain PZNNT-1wt%Ag powder of 75 - 150 μm; then dry-press under an axial pressure of 8 MPa and maintain the pressure for 5 min to obtain a PZNNT-1wt%Ag ceramic green body, and the particle size of the nano-Ag is 100 nm; Step 3, sinter the PZNNT-Ag ceramic green body; The PZNNT-1wt% Ag ceramic embryo obtained in step 2 is kept at 500°C for 1h for debinding, and then sintered at 960°C for 2h to obtain a nano-Ag composite PZNNT-based piezoelectric ceramic, and the heating rate is 5°C / min; the surface of the sintered body is polished using 600 mesh, 1000 mesh, 1500 mesh and 2000 mesh sandpaper in sequence to form a 12mm×1mm ceramic disc; then a silver electrode is coated on the surface of the polished ceramic disc, and a polarization treatment is performed, and the polarization process is a polarization temperature of 120°C, a polarization field strength of 3kV / mm, and a polarization time of 30min.

Images