Potassium-sodium niobate-based piezoelectric ceramic and preparation method thereof

Abstract

The invention relates to the field of piezoelectric ceramic materials, in particular to potassium-sodium niobate-based piezoelectric ceramic and a preparation method thereof, the chemical structure of the potassium-sodium niobate-based piezoelectric ceramic is as follows: (1-alpha-beta) Lix (Na1 / 2K1 / 2) 1-xNb1-y (W1 / 2Mn1 / 2) yO3-alpha (Ln2-zSrz) CuO4-beta Bi2O3, Ln is a lanthanide rare earth element; 0 < x < = 0.1, 0 < y < = 0.1, and 0 < z < = 0.5; 0 < alpha < = 0.05, 0 < beta < = 0.05, and the potassium-sodium niobate-based piezoelectric ceramic prepared by the method has excellent piezoelectric properties and has wide application prospects in the fields of transduction, filtering, ultrasonic detection and the like.

Description

Technical Field

[0001] The present invention relates to the field of piezoelectric ceramic materials, and particularly to a sodium potassium niobate-based piezoelectric ceramic and a preparation method thereof. Background Art

[0002] As a main representative of piezoelectric ceramics, lead zirconate titanate-based piezoelectric ceramics are widely used in the fields of transducers, filters, and ultrasonic detection due to their excellent piezoelectric properties and occupy an important position in the market. However, lead zirconate titanate-based piezoelectric ceramics have a high lead content, and lead is toxic and volatile. Therefore, such piezoelectric ceramics will cause harm to people's physical health and living environment during the preparation, application, and disposal processes. Therefore, the research and development of environmentally friendly lead-free piezoelectric ceramics have become a research hotspot.

[0003] Among them, sodium potassium niobate-based lead-free piezoelectric ceramics are considered to be one of the most promising candidate materials to replace lead zirconate titanate-based piezoelectric ceramics due to their good piezoelectric properties and high Curie temperature. However, the piezoelectric properties of pure sodium potassium niobate-based lead-free piezoelectric ceramics are still far from those of lead zirconate titanate-based piezoelectric ceramics. Therefore, in order to make sodium potassium niobate-based piezoelectric ceramics practical, further modification is needed to improve their performance. Summary of the Invention

[0004] Object of the Invention: Aiming at the above technical problems, the present invention provides a sodium potassium niobate-based piezoelectric ceramic and a preparation method thereof.

[0005] The technical solution adopted is as follows:

[0006] A sodium potassium niobate-based piezoelectric ceramic, whose chemical structure is as follows:

[0007] ((I-α-β)Li x (Na 1 / 2 K 1 / 2 ) 1-x Nb 1-y (W 1 / 2 Mn 1 / 2 ) y O3-α(Ln 2-z Sr z )CuO4-βBi2O3

[0008] Wherein, Ln is a lanthanide rare earth element;

[0009] 0<x≤0.1, 0<y≤0.1, 0<z≤0.5;

[0010] 0<α≤0.05, 0<β≤0.05.

[0011] Furthermore, Ln is La.

[0012] Further, 0.02 ≤ x ≤ 0.08, 0.02 ≤ y ≤ 0.08, 0.05 ≤ z ≤ 0.15.

[0013] Further, x = 0.06, y = 0.05, z = 0.1.

[0014] Further, 0.01 ≤ α ≤ 0.02, 0.005 ≤ β ≤ 0.015.

[0015] Further, α = 0.015, β = 0.01.

[0016] The present invention provides a preparation method of sodium potassium niobate-based piezoelectric ceramics:

[0017] Mix Li x (Na 1 / 2 K 1 / 2 ) 1-x Nb 1-y (W 1 / 2 Mn 1 / 2 ) y O3, (Ln 2-z Sr z )CuO4, Bi2O3 by ball milling and then dry to obtain a mixed powder. Granulate the mixed powder, sieve it, and press it to obtain a green body. The green body can be sintered after heating to remove the binder.

[0018] Furthermore, the preparation method of the above sodium potassium niobate-based piezoelectric ceramics is as follows:

[0019] According to the stoichiometric ratio, pour Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 into a ball milling tank for ball milling and mixing. The ball milling medium is anhydrous ethanol. After drying the mixed material obtained by ball milling, pre-burn it in a muffle furnace to obtain a first powder;

[0020] Respectively use lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source, deionized water as the solvent, and citric acid as the complexing agent. Dissolve lanthanum nitrate, strontium nitrate, and copper nitrate in an appropriate amount of deionized water according to the stoichiometric ratio, stir to prepare a transparent solution, then add citric acid, stir to obtain a homogeneous solution, and then dropwise add ammonia water, stir to obtain a sol. Age and dry the sol to obtain a xerogel. Grind the xerogel and then calcine it to obtain a second powder;

[0021] Pour the first powder, the second powder, and Bi2O3 into a ball milling tank for ball milling and mixing. After drying the mixed material obtained by ball milling, mix it with a polyvinyl alcohol solution for granulation and sieving, and then press it into a green body. Place the green body in a muffle furnace, first heat it to remove the binder and then sinter it.

[0022] Further, the pressure during pressing is 100 - 200 MPa.

[0023] Furthermore, the debinding temperature is 600 - 800 °C.

[0024] Furthermore, the sintering temperature is 950 - 1050 °C.

[0025] Advantages of the present invention:

[0026] The present invention provides a sodium potassium niobate-based piezoelectric ceramic. The strong electronegativity of W 6+ can significantly improve the piezoelectric properties of sodium potassium niobate-based through lattice distortion-induced phase boundary, oxygen vacancy-regulated domain movement, and polarization enhancement, enabling Mn 4+ and W 6+ to be doped in a molar ratio of 1:1 for composite doping, maintaining the electron conservation state at the B-site and replacing the B-site elements, which can synergistically optimize piezoelectric anisotropy, inhibit the volatilization of alkali metals, reduce grain boundary defects. At the same time, the introduction of low-valence Mn at the B-site 4+ causes oxygen vacancies that lead to lattice shrinkage and increase the density of the piezoelectric ceramic;

[0027] (Ln 2-u Sr u )CuO4 can cause lattice distortion through lattice substitution at the A- and B-sites, induce the orthorhombic phase to tetragonal phase transformation, promote the formation of a morphotropic phase boundary, thereby optimizing the piezoelectric response and enhancing the piezoelectric properties. It can also act as a sintering aid, improving the ceramic sintering performance, increasing the density of the ceramic. The addition of Bi2O3 can improve the sintering performance of the piezoelectric ceramic, reduce the sintering temperature, inhibit the volatilization of alkali metals, and increase the sintering density;

[0028] The sodium potassium niobate-based piezoelectric ceramic prepared by the present invention has excellent piezoelectric properties and has broad application prospects in the fields of transducers, filters, and ultrasonic detection. Description of the Drawings

[0029] Figure 1 It is the SEM image of the sodium potassium niobate-based piezoelectric ceramic prepared in Example 1. Detailed Embodiments

[0030] For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. Technologies not mentioned in the present invention refer to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel experiments and adopt the same treatment steps and parameters.

[0031] Example 1:

[0032] This example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0033] 0.975Li 0.06 (Na 1 / 2K 1 / 2 ) 0.94 Nb 0.95 (W 1 / 2 Mn 1 / 2 ) 0.05 O3-0.015(La 1.9 Sr 0.1 )CuO4-0.01Bi2O3

[0034] The preparation method of the above sodium potassium niobate-based piezoelectric ceramics is as follows:

[0035] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 are poured into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a forward and reverse alternating operation mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is pre-fired in a muffle furnace at 750 °C for 2 h to obtain the first powder;

[0036] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid)=1.9:0.1:1:6, dissolve lanthanum nitrate, strontium nitrate, and copper nitrate in an appropriate amount of deionized water, stir to prepare a transparent solution, then add citric acid, stir to obtain a homogeneous solution, and then gradually add ammonia water to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a xerogel. The xerogel is ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder;

[0037] Pour the first powder, the second powder, and Bi2O3 into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a forward and reverse alternating operation mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is mixed with a 5 wt.% polyvinyl alcohol solution, granulated, and passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min. After heat preservation and degumming for 2 h, it is then heated to 950 °C at a rate of 5 °C / min and sintered for 3 h. The SEM image of the sodium potassium niobate-based piezoelectric ceramics prepared in this example is shown in Figure 1 , it can be seen that the grain boundaries are clear, there are few pores between the grain boundaries, the ceramic is relatively dense, and no obvious pores are seen.

[0038] Example 2:

[0039] This example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0040] 0.975Li0.06 (Na 1 / 2 K 1 / 2 ) 0.94 Nb 0.95 (W 1 / 2 Mn 1 / 2 ) 0.05 O3-0.015(La 1.9 Sr 0.1 )CuO4-0.01Bi2O3

[0041] The preparation method of the above sodium potassium niobate-based piezoelectric ceramic is as follows:

[0042] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 are poured into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a positive and negative alternating running mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is pre-fired in a muffle furnace at 750 °C for 2 h to obtain the first powder material;

[0043] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid) = 1.9:0.1:1:6, dissolve lanthanum nitrate, strontium nitrate, and copper nitrate in an appropriate amount of deionized water, stir to prepare a transparent solution, then add citric acid, stir to obtain a homogeneous solution, and then gradually add ammonia water to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a dry gel. The dry gel is ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder material;

[0044] Pour the first powder material, the second powder material, and Bi2O3 into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a positive and negative alternating running mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is mixed with a 5 wt.% polyvinyl alcohol solution, granulated, and passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min, held for 2 h for degumming, and then heated to 1000 °C at a rate of 5 °C / min and held for sintering for 3 h to obtain the product.

[0045] Example 3:

[0046] This example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0047] 0.975Li 0.06 (Na 1 / 2 K1 / 2 ) 0.94 Nb 0.95 (W 1 / 2 Mn 1 / 2 ) 0.05 O3-0.015(La 1.9 Sr 0.1 )CuO4-0.01Bi2O3

[0048] The preparation method of the above sodium potassium niobate-based piezoelectric ceramic is as follows:

[0049] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, MnO2, and Sb2O3 are poured into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a forward and reverse alternating operation mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is pre-fired in a muffle furnace at 750 °C for 2 h to obtain the first powder material;

[0050] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid)=1.9:0.1:1:6, dissolve lanthanum nitrate, strontium nitrate, and copper nitrate in an appropriate amount of deionized water, stir to prepare a transparent solution, then add citric acid, stir to obtain a homogeneous solution, and then gradually add ammonia water to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a dry gel. After grinding the dry gel, it is calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder material;

[0051] Pour the first powder material, the second powder material, and Bi2O3 into a ball mill jar for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, the ball milling is carried out in a forward and reverse alternating operation mode, the interval time is 1 h, and the total ball milling time is 10 h. After drying the mixed material obtained by ball milling, it is mixed with a 5 wt.% polyvinyl alcohol solution for granulation and passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min. After heat preservation and degumming for 2 h, it is then heated to 1050 °C at a rate of 5 °C / min and sintered at this temperature for 3 h to obtain the product.

[0052] Example 4:

[0053] This example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0054] 0.975Li 0.06 (Na 1 / 2 K 1 / 2 ) 0.94 Nb0.95 (W 1 / 2 Mn 1 / 2 ) 0.05 O3-0.015(La 1.95 Sr 0.05 )CuO4-0.01Bi2O3

[0055] The preparation method of the above sodium potassium niobate-based piezoelectric ceramic is as follows:

[0056] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 are poured into a ball milling tank for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, and the ball milling is carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it is pre-fired in a muffle furnace at 750 °C for 2 h to obtain the first powder material;

[0057] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid) = 1.95:0.05:1:6, lanthanum nitrate, strontium nitrate, and copper nitrate are dissolved in an appropriate amount of deionized water, stirred to form a transparent solution, then citric acid is added, stirred to obtain a homogeneous solution, and then ammonia water is added dropwise to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a dry gel. The dry gel is ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder material;

[0058] The first powder material, the second powder material, and Bi2O3 are poured into a ball milling tank for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, and the ball milling is carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it is mixed with a 5 wt.% polyvinyl alcohol solution, granulated, passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min, held for 2 h for degumming, and then heated to 950 °C at a rate of 5 °C / min and held for 3 h for sintering to obtain the product.

[0059] Example 5:

[0060] This example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0061] 0.975Li 0.06 (Na 1 / 2 K 1 / 2 ) 0.94 Nb 0.95 (W 1 / 2 Mn1 / 2 ) 0.05 O3 - 0.015(La 1.85 Sr 0.15 )CuO4 - 0.01Bi2O3

[0062] The preparation method of the above - mentioned sodium potassium niobate - based piezoelectric ceramics is as follows:

[0063] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 are poured into a ball - milling tank for ball - milling and mixing. The ball - milling medium is anhydrous ethanol, the ball - milling speed is 300 r / min, and the ball - milling is carried out in a forward - and - reverse alternating operation mode with an interval time of 1 h and a total ball - milling time of 10 h. After drying the mixed material obtained by ball - milling, it is pre - sintered in a muffle furnace at 750 °C for 2 h to obtain the first powder material;

[0064] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid)=1.85:0.15:1:6, lanthanum nitrate, strontium nitrate, and copper nitrate are dissolved in an appropriate amount of deionized water, stirred to form a transparent solution, then the added citric acid is added, stirred to obtain a homogeneous solution, and then ammonia water is added dropwise to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a dry gel. The dry gel is ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder material;

[0065] The first powder material, the second powder material, and Bi2O3 are poured into a ball - milling tank for ball - milling and mixing. The ball - milling medium is anhydrous ethanol, the ball - milling speed is 300 r / min, and the ball - milling is carried out in a forward - and - reverse alternating operation mode with an interval time of 1 h and a total ball - milling time of 10 h. After drying the mixed material obtained by ball - milling, it is mixed with a 5 wt.% polyvinyl alcohol solution, granulated, passed through an 80 - mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min, held for 2 h for degumming, and then heated to 950 °C at a rate of 5 °C / min and held for 3 h for sintering.

[0066] Comparative Example 1:

[0067] It is basically the same as Example 1, except that (La 1.85 Sr 0.15 )CuO4 is not added.

[0068] Comparative Example 2:

[0069] It is basically the same as Example 1, except that La2CuO4 is used instead of (La 1.85 Sr 0.15 )CuO4.

[0070] This comparative example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is as follows:

[0071] 0.975Li 0.06 (Na 1 / 2 K 1 / 2 ) 0.94 Nb 0.95 (W 1 / 2 Mn 1 / 2 ) 0.05 O3 - 0.01La2CuO4 - 0.01Bi2O3

[0072] The preparation method of the above sodium potassium niobate-based piezoelectric ceramic is as follows:

[0073] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, Nb2O5, WO3, and MnO2 were poured into a ball mill tank for ball milling and mixing. The ball milling medium was anhydrous ethanol, the ball milling speed was 300 r / min, and the ball milling was carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it was pre-calcined in a muffle furnace at 750 °C for 2 h to obtain the first powder;

[0074] Using lanthanum nitrate and copper nitrate as the lanthanum source and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Cu):n(citric acid) = 2:1:6, lanthanum nitrate and copper nitrate were dissolved in an appropriate amount of deionized water, stirred to form a transparent solution, then citric acid was added, stirred to obtain a homogeneous solution, and then ammonia water was added dropwise to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol was obtained. The sol was aged at 80 °C for 10 h and then dried to obtain a dry gel. The dry gel was ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder;

[0075] The first powder, the second powder, and Bi2O3 were poured into a ball mill tank for ball milling and mixing. The ball milling medium was anhydrous ethanol, the ball milling speed was 300 r / min, and the ball milling was carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it was mixed with a 5 wt.% polyvinyl alcohol solution, granulated, passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body was placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min. After holding for 2 h to remove the binder, it was then heated to 950 °C at a rate of 5 °C / min and held for 3 h for sintering.

[0076] Comparative Example 3:

[0077] It is basically the same as Example 1, except that no composite ion doping is carried out;

[0078] This comparative example provides a sodium potassium niobate-based piezoelectric ceramic, and its chemical structure is shown as follows:

[0079] 0.975Li 0.06 (Na 1 / 2 K 1 / 2 ) 0.94 NbO3-0.015(La 1.9 Sr 0.1 )CuO4-0.01Bi2O3

[0080] The preparation method of the above sodium potassium niobate-based piezoelectric ceramic is as follows:

[0081] According to the stoichiometric ratio, Li2CO3, Na2CO3, K2CO3, and Nb2O5 are poured into a ball milling tank for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, and the ball milling is carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it is pre-fired in a muffle furnace at 750 °C for 2 h to obtain the first powder;

[0082] Using lanthanum nitrate, strontium nitrate, and copper nitrate as the lanthanum source, strontium source, and copper source respectively, deionized water as the solvent, and citric acid as the complexing agent, according to the molar ratio of n(La):n(Sr):n(Cu):n(citric acid)=1.9:0.1:1:6, lanthanum nitrate, strontium nitrate, and copper nitrate are dissolved in an appropriate amount of deionized water, stirred to form a transparent solution, then citric acid is added, stirred to obtain a homogeneous solution, and then ammonia water is added dropwise to adjust the pH of the solution to 2. After stirring at room temperature for 1 h, a sol is obtained. The sol is aged at 80 °C for 10 h and then dried to obtain a dry gel. The dry gel is ground and then calcined in a muffle furnace at 600 °C for 2 h to obtain the second powder;

[0083] The first powder, the second powder, and Bi2O3 are poured into a ball milling tank for ball milling and mixing. The ball milling medium is anhydrous ethanol, the ball milling speed is 300 r / min, and the ball milling is carried out in a forward and reverse alternating operation mode with an interval time of 1 h and a total ball milling time of 10 h. After drying the mixed material obtained by ball milling, it is mixed with a 5 wt.% polyvinyl alcohol solution, granulated, passed through an 80-mesh sieve, and then pressed into a green body at 150 MPa. The green body is placed in a muffle furnace and heated to 700 °C at a rate of 1 °C / min. After holding for degassing for 2 h, it is then heated to 950 °C at a rate of 5 °C / min and held for sintering for 3 h.

[0084] Comparative Example 4:

[0085] It is basically the same as Example 1, except that Bi2O3 is not added.

[0086] Performance test:

[0087] The surfaces of the sodium potassium niobate-based piezoelectric ceramics prepared in Examples 1-5 and Comparative Examples 1-4 were polished respectively, silver paste was coated on both sides, and they were kept at 550 °C for 30 min. Finally, they were polarized in silicone oil at 110 ± 5 °C under a DC voltage of 4 kV / mm for 20 min and then left for 24 h to be used as specimens to test their electrical properties.

[0088] A ZJ-3AN type quasi-static piezoelectric constant tester was used to measure the room-temperature piezoelectric constant of the specimens;

[0089] A precision impedance analyzer (Agilent HP4294A) was used to measure and analyze the electromechanical coupling coefficient kp, mechanical quality factor Qm, and dielectric loss tanδ (25 °C, 1 v, 1 kHz) of the specimens;

[0090] The test results are shown in Table 1 below:

[0091] Table 1:

[0092]

[0093] As can be seen from Table 1 above, the sodium potassium niobate-based piezoelectric ceramics prepared by the present invention have excellent piezoelectric properties;

[0094] Among them, through the comparison of Examples 1-3, it can be seen that the sintering temperature will affect the piezoelectric properties of the sodium potassium niobate-based piezoelectric ceramics. When the sintering temperature is 1000 °C, the piezoelectric properties of the prepared sodium potassium niobate-based piezoelectric ceramics are the best;

[0095] Through the comparison of Example 1 with Examples 4-5, it can be seen that when n(La):n(Sr) = 1.9:0.1, the piezoelectric properties of the prepared sodium potassium niobate-based piezoelectric ceramics are the best;

[0096] Through the comparison of Example 1 with Comparative Examples 1 and 2, it can be seen that the addition of (La 1.85 Sr 0.15 )CuO4 and Sr 2+ doping play a positive role in improving the piezoelectric properties of the sodium potassium niobate-based piezoelectric ceramics;

[0097] Through the comparison of Example 1 with Comparative Example 3, it can be seen that the doping of (W 1 / 2 Mn 1 / 2 ) 5+ plays a positive role in improving the piezoelectric properties of the sodium potassium niobate-based piezoelectric ceramics;

[0098] Through the comparison of Example 1 with Comparative Example 4, it can be seen that the addition of Bi2O3 plays a positive role in improving the piezoelectric properties of the sodium potassium niobate-based piezoelectric ceramics.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A sodium potassium niobate-based piezoelectric ceramic, characterized in that, Its chemical structure is shown as follows: (1-α-β)Li x (Na 1 / 2 K 1 / 2 ) 1-x Nb 1-y (W 1 / 2 Mn 1 / 2 ) y O3-α(Ln 2-z Sr z )CuO4-βBi2O3 Among them, Ln is a lanthanide rare earth element; 0 < x ≤ 0.1, 0 < y ≤ 0.1, 0 < z ≤ 0.5; 0＜α≤0.05，0＜β≤0.05。 2. The sodium potassium niobate-based piezoelectric ceramic according to claim 1, wherein, Ln is La.

3. The sodium potassium niobate-based piezoelectric ceramic according to claim 1, characterized in that, 0.02 ≤ x ≤ 0.08, 0.02 ≤ y ≤ 0.08, 0.05 ≤ z ≤ 0.

15.

4. The sodium potassium niobate-based piezoelectric ceramic according to claim 1, characterized in that, x = 0.06, y = 0.05, z = 0.

1.

5. The sodium potassium niobate-based piezoelectric ceramic according to claim 1, characterized in that, 0.01≤α≤0.02，0.005≤β≤0.015。 6. The sodium potassium niobate-based piezoelectric ceramic according to claim 1, characterized in that, α＝0.015，β＝0.01。 7. A method for preparing a sodium potassium niobate-based piezoelectric ceramic according to any one of claims 1-6, characterized in that, Mix Li x (Na 1 / 2 K 1 / 2 ) 1-x with Nb 1-y (W 1 / 2 Mn 1 / 2 ) y O3, (Ln 2-z Sr z )CuO4, and Bi₂O₃, ball-mill them and then dry to obtain a mixed powder. Granulate the mixed powder, sieve it, and press it to obtain a green body. Sinter the green body after heating to remove the binder.

8. The preparation method of the sodium potassium niobate-based piezoelectric ceramic according to claim 7, characterized in that, The pressure during pressing is 100 - 200 MPa.

9. The preparation method of the sodium potassium niobate-based piezoelectric ceramic according to claim 7, characterized in that, The debinding temperature is 600 - 800 °C.

10. The preparation method of the sodium potassium niobate-based piezoelectric ceramic according to claim 7, characterized in that, The sintering temperature is 950 - 1050 °C.

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