A KNN-based lead-free piezoelectric ceramic material

Abstract

The present invention relates to the field of electronic ceramic materials, in particular to a KNN-based lead-free piezoelectric ceramic material, the chemical composition of which is as follows: (1-α)(K x Na 1‑x )(Nb y Ta 1‑y ) 3 ‑αMRAlO 4 + sintering aid, wherein α, x, and y are atomic percentages; α is 0.01-0.1; x is 0.4-0.6; y is 0.85-0.99; M is a Group IIA element; R is a rare earth element; the amount of sintering aid is (1-α)(K x Na 1‑x )(Nb y Ta 1‑y ) 3 ‑αMRAlO 4 The KNN-based lead-free piezoelectric ceramic material prepared by the present invention has excellent piezoelectric properties and has great application potential in the field of piezoelectric ceramic sensors.

Description

Technical Field

[0001] The invention relates to the field of electronic ceramic materials, in particular to a KNN-based lead-free piezoelectric ceramic material. Background Art

[0002] With the rapid development of the electronics industry, the demand for micro energy storage electronic components such as capacitors and integrated circuits is increasing, and higher requirements are also placed on the performance and preparation process of such products. In response to the concept of green, coordinated and sustainable development, environmentally friendly micro energy storage components have become a hot spot for research and development, attracting the attention and research of many scientific researchers at home and abroad, including the electronic ceramic industry, which has a history of decades of development.

[0003] Lead zirconate titanate ceramics have always dominated the field of piezoelectric applications due to their good piezoelectric properties. However, the long-term use of lead zirconate titanate ceramics will cause environmental pollution. As people pay more attention to environmental issues, finding new lead-free piezoelectric ceramics to replace lead-containing piezoelectric ceramics has become one of the hot topics in material research.

[0004] KNN-based lead-free piezoelectric ceramics have attracted much attention due to their environmental friendliness and high Curie temperature, and are expected to be widely used in transducers, drivers, sensors and other fields. However, the piezoelectric properties of high-purity KNN ceramics are poor (d 33 =72-90pC / N) seriously limits the industrial production and practical application of KNN ceramics. Summary of the invention

[0005] Purpose of the invention: In view of the above technical problems, the present invention proposes a KNN-based lead-free piezoelectric ceramic material.

[0006] The technical solutions adopted are as follows:

[0007] A KNN-based lead-free piezoelectric ceramic material, the chemical composition of which is as follows:

[0008] (1-α)(K x Na 1-x )(Nb y Ta 1-y )O3-αMRAlO4+sintering aid

[0009] Wherein, α, x, and y are atomic percentages;

[0010] α is 0.01-0.1;

[0011] x is 0.4-0.6;

[0012] y is 0.85-0.99;

[0013] M is a Group IIA element;

[0014] R is a rare earth element;

[0015] The amount of the sintering aid is (1-α)(K x Na 1-x )(Nb y Ta 1-y )O3-αMRAlO4 mass 0.1-1%.

[0016] Further, α is 0.03-0.06.

[0017] Further, α is 0.04.

[0018] Further, x is 0.45-0.55, and y is 0.9-0.95.

[0019] Further, x is 0.5 and y is 0.92.

[0020] Furthermore, M is Ca, Sr or Ba, and R is Sm.

[0021] Further, the sintering aid includes transition metal oxide and LiBiO2;

[0022] The weight ratio of the transition metal oxide to LiBiO2 is 1-5:1-5.

[0023] Furthermore, the transition metal oxide is CoO.

[0024] Furthermore, the preparation method of the above-mentioned KNN-based lead-free piezoelectric ceramic material is as follows:

[0025] Weigh the raw materials according to the chemical composition, mix and ball-mill them, then dry them. Pre-sinter them at 850-950℃ for 1-4h, then ball-mill them again and dry them. Add a binder to granulate them, and dry-press them into a green body. Heat the green body to 650-700℃ and keep it for 1-3h to debind, then heat it to 1250-1350℃ and keep it for sintering for 2-4h, and finally cool it to room temperature with the furnace.

[0026] Furthermore, the sintering is carried out in a mixed atmosphere consisting of nitrogen and hydrogen, wherein the volume fraction of hydrogen is 10-40%.

[0027] Beneficial effects of the present invention:

[0028] The present invention provides a KNN-based lead-free piezoelectric ceramic material. By introducing a perovskite-like composite oxide MRA1O4 to form a new multi-component solid solution system, the KNN-based ceramic material is transformed from a trigonal-tetragonal coexisting phase to a single pseudo-cubic phase, which plays a significant role in promoting the improvement of the electrostrain of the KNN-based ceramic material.

[0029] Sintering aids can reduce the sintering temperature and produce more liquid phase during the sintering process, filling the pores between grains and inhibiting the formation of impurity phases, increasing the density of ceramics and improving piezoelectric properties;

[0030] Sintering in a reducing atmosphere can reduce the grain size of KNN-based lead-free piezoelectric ceramic materials, thereby reducing the size of the electric domain, reducing the activation energy of the electric domain reversal, making the electric domain reversal easier, and can improve the piezoelectric properties of KNN-based lead-free piezoelectric ceramic materials and improve the density to a certain extent, so that the performance of KNN-based lead-free piezoelectric ceramic materials has been further optimized;

[0031] The KNN-based lead-free piezoelectric ceramic material prepared by the present invention has excellent piezoelectric properties and has great application potential in the field of piezoelectric ceramic sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the SEM image of the KNN-based lead-free piezoelectric ceramic material prepared in Example 1. DETAILED DESCRIPTION

[0033] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. The techniques not mentioned in the present invention are all referenced to the prior art. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0034] Embodiment 1:

[0035] A KNN-based lead-free piezoelectric ceramic material, the chemical composition of which is as follows:

[0036] 0.96(K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4+LiBiO2+CoO

[0037] The dosage of LiBiO2 and CoO is 0.96 (K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4 is 0.1% by mass.

[0038] The preparation method of the above-mentioned KNN-based lead-free piezoelectric ceramic material is as follows:

[0039] The raw materials Na2CO3, K2CO3, Nb2O5, Ta2O5, CaCO3, Sm2O3, Al2O3, LiBiO2 and CoO were weighed according to the chemical composition and milled in a planetary ball mill with water as the ball milling medium for 10 hours and then dried. The obtained mixed powder was heated to 900℃ at a rate of 10℃ / min in an air atmosphere and pre-calcined for 4 hours, then added to the ball milling tank of the planetary ball mill again, and continued to ball mill for 5 hours and dried, and polyethylene with a mass concentration of 8% was added. The alcohol solution is used as a binder for granulation, and the sieved powder is added into a mold and dry-pressed into a green body under a pressure of 200 MPa. The green body is transferred to a muffle furnace, and the muffle furnace is first evacuated and then a mixed gas composed of nitrogen and hydrogen is introduced. The volume fraction of hydrogen in the mixed gas is 30%. The muffle furnace is sealed, and the temperature is first increased to 680°C at a rate of 20°C / min and kept for debinding for 2 hours, and then increased to 1350°C at a rate of 5°C / min and kept for sintering for 2 hours, and finally cooled to room temperature with the furnace.

[0040] Embodiment 2:

[0041] A KNN-based lead-free piezoelectric ceramic material, the chemical composition of which is as follows:

[0042] 0.96(K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4+LiBiO2+CoO

[0043] The dosage of LiBiO2 and CoO is 0.96 (K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4 is 0.1% and 0.2% by mass.

[0044] The preparation method of the above-mentioned KNN-based lead-free piezoelectric ceramic material is as follows:

[0045] The raw materials Na2CO3, K2CO3, Nb2O5, Ta2O5, CaCO3, Sm2O3, Al2O3, LiBiO2 and CoO were weighed according to the chemical composition and milled in a planetary ball mill with water as the ball milling medium for 10 hours and then dried. The obtained mixed powder was heated to 900℃ at a rate of 10℃ / min in an air atmosphere and pre-calcined for 4 hours, then added to the ball milling tank of the planetary ball mill again, and continued to ball mill for 5 hours and dried, and polyethylene with a mass concentration of 8% was added. The alcohol solution is used as a binder for granulation, and the sieved powder is added into a mold and dry-pressed into a green body under a pressure of 200 MPa. The green body is transferred to a muffle furnace, and the muffle furnace is first evacuated and then a mixed gas composed of nitrogen and hydrogen is introduced. The volume fraction of hydrogen in the mixed gas is 30%. The muffle furnace is sealed, and the temperature is first increased to 680°C at a rate of 20°C / min and kept for debinding for 2 hours, and then increased to 1350°C at a rate of 5°C / min and kept for sintering for 2 hours, and finally cooled to room temperature with the furnace.

[0046] Embodiment 3:

[0047] A KNN-based lead-free piezoelectric ceramic material, the chemical composition of which is as follows:

[0048] 0.96(K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4+LiBiO2+CoO

[0049] The dosage of LiBiO2 and CoO is 0.96 (K 0.5 Na 0.5 )(Nb 0.92 Ta 0.08 )O3-0.04CaSmAlO4 0.2% and 0.1% by mass.

[0050] The preparation method of the above-mentioned KNN-based lead-free piezoelectric ceramic material is as follows:

[0051] The raw materials Na2CO3, K2CO3, Nb2O5, Ta2O5, CaCO3, Sm2O3, Al2O3, LiBiO2 and CoO were weighed according to the chemical composition and milled in a planetary ball mill with water as the ball milling medium for 10 hours and then dried. The obtained mixed powder was heated to 900℃ at a rate of 10℃ / min in an air atmosphere and pre-calcined for 4 hours, then added to the ball milling tank of the planetary ball mill again, and continued to ball mill for 5 hours and dried, and polyethylene with a mass concentration of 8% was added. The alcohol solution is used as a binder for granulation, and the sieved powder is added into a mold and dry-pressed into a green body under a pressure of 200 MPa. The green body is transferred to a muffle furnace, and the muffle furnace is first evacuated and then a mixed gas composed of nitrogen and hydrogen is introduced. The volume fraction of hydrogen in the mixed gas is 30%. The muffle furnace is sealed, and the temperature is first increased to 680°C at a rate of 20°C / min and kept for debinding for 2 hours, and then increased to 1350°C at a rate of 5°C / min and kept for sintering for 2 hours, and finally cooled to room temperature with the furnace.

[0052] Comparative Example 1:

[0053] The same as Example 1, except that a KNN-based lead-free piezoelectric ceramic material has the following chemical composition:

[0054] 0.96(K 0.5 Na 0.5 )NbO3-0.04CaSmAlO4+LiBiO2+CoO

[0055] The dosage of LiBiO2 and CoO is 0.96 (K 0.5 Na 0.5 )0.1% by mass of NbO3-0.04CaSmAlO4.

[0056] The preparation method of the above-mentioned KNN-based lead-free piezoelectric ceramic material is as follows:

[0057] According to the chemical composition, the raw materials Na2CO3, K2CO3, Nb2O5, CaCO3, Sm2O3, Al2O3, LiBiO2 and CoO were weighed and milled in a planetary ball mill with water as the ball milling medium for 10 hours and then dried. The obtained mixed powder was heated to 900℃ at a rate of 10℃ / min in an air atmosphere and pre-calcined for 4 hours. Then, it was added to the ball milling tank of the planetary ball mill again, and the ball milling was continued for 5 hours and dried. A polyvinyl alcohol solution with a mass concentration of 8% was added. As a binder granulation, the sieved powder is added into the mold and dry-pressed into a green body under a pressure of 200MPa. The green body is transferred to a muffle furnace. The muffle furnace is first evacuated and then a mixed gas composed of nitrogen and hydrogen is introduced. The volume fraction of hydrogen in the mixed gas is 30%. The muffle furnace is sealed, and the temperature is first increased to 680℃ at a rate of 20℃ / min and kept for 2h to debind, and then increased to 1350℃ at a rate of 5℃ / min and kept for sintering for 2h, and finally cooled to room temperature with the furnace.

[0058] Comparative Example 2:

[0059] It is basically the same as Example 1, except that CaSmAlO4 is not added.

[0060] Comparative Example 3:

[0061] It is basically the same as Example 1, except that LiBiO2 is not added.

[0062] Comparative Example 4:

[0063] It is basically the same as Example 1, except that CoO is not added.

[0064] Comparative Example 5:

[0065] It is basically the same as Example 1, except that the debinding and sintering are performed in an air atmosphere.

[0066] Performance Test:

[0067] The KNN-based lead-free piezoelectric ceramic materials prepared in Examples 1-3 and Comparative Examples 1-5 of the present invention were polished, and then silver paste was brushed on the upper and lower surfaces, and then cured at 600° C. for 30 min, immersed in silicone oil at 70° C. and polarized with a DC electric field of 3 kv / mm for 30 min as samples for performance testing;

[0068] Use ZJ-3A quasi-static d 33 The tester measures the piezoelectric constant of the sample, and uses Agilent's HP4192 precision impedance analyzer to test the dielectric loss tanδ, resonant frequency, anti-resonant frequency and corresponding impedance of the sample, and calculates the electromechanical coupling coefficient k of the sample based on this. p and mechanical quality factor Q m ;

[0069] The test results are shown in Table 1 below:

[0070] Table 1:

[0071] ;

[0072] It can be seen from Table 1 above that the KNN-based lead-free piezoelectric ceramic material prepared in the present invention has excellent piezoelectric properties and has great application potential in the field of piezoelectric ceramic sensors.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A KNN-based lead-free piezoelectric ceramic material, It is characterized in that Its chemical composition is as follows: (1-α)(K x Na 1-x )(Nb y Ta 1-y ) 3 -αCaSmAlO 4 +Sintering Aids Wherein, α, x, and y are atomic percentages; α is 0.01-0.1; x is 0.4-0.6; y is 0.85-0.99; The amount of the sintering aid is (1-α)(K x Na 1-x )(Nb y Ta 1-y ) 3 -αCaSmAlO 4 0.1-1% of mass; The sintering aid includes CoO and LiBiO 2 ; The CoO and LiBiO 2 The weight ratio is 1-5:1-5.

2. The KNN-based lead-free piezoelectric ceramic material according to claim 1, It is characterized in that α is 0.03-0.

06.

3. The KNN-based lead-free piezoelectric ceramic material according to claim 1, It is characterized in that α is 0.

04.

4. The KNN-based lead-free piezoelectric ceramic material according to claim 1, It is characterized in that x is 0.45-0.55, and y is 0.9-0.

95.

5. The KNN-based lead-free piezoelectric ceramic material according to claim 1, It is characterized in that x is 0.5 and y is 0.

92.

6. The KNN-based lead-free piezoelectric ceramic material according to claim 1, It is characterized in that The preparation method is as follows: Weigh the raw materials according to the chemical composition, mix and ball-mill them, then dry them. Pre-sinter them at 850-950℃ for 1-4h, then ball-mill them again and dry them. Add a binder to granulate them, and dry-press them into a green body. Heat the green body to 650-700℃ and keep it for 1-3h to debind, then heat it to 1250-1350℃ and keep it for sintering for 2-4h, and finally cool it to room temperature with the furnace.

7. The KNN-based lead-free piezoelectric ceramic material according to claim 6, It is characterized in that The sintering is carried out in a mixed atmosphere of nitrogen and hydrogen, wherein the volume fraction of hydrogen is 10-40%.

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