Na / sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material and preparation method thereof

Abstract

This invention discloses a Na / Sr / Ce / Cr / Ta / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material, targeting the Ca at the A-site of the CaBi₂Nb₂O₉ ceramic material. 2+ Ions, using K with 12 coordination sites + Ba 2+ Y 3+ Composition of complex high-valence ions [Na 0.2 Sr 0.4 Ce 0.4 ] 2.6+ Doping substitution is performed on Nb at the B site. 5+ Ions, using Cr with 6 coordination groups 2+ Ta 5+ Mo 6+ Composition of complex high-valence ions [Cr 0.05 Ta 0.3 Mo 0.65 ] 5.5+ By performing doping and substitution, and through the aforementioned composite doping modification, the piezoelectric properties and high-temperature resistivity are improved while maintaining a high Curie temperature. This results in a novel, environmentally friendly piezoelectric ceramic material with excellent overall electrical properties. This material exhibits good high-temperature stability and has broad application prospects in high-temperature fields. The preparation method of this invention employs advanced ceramic preparation technology, with low firing temperature, low preparation cost, simple and easy-to-operate process, and easily controllable influencing factors. It is suitable for mass industrial production and facilitates its promotion and application.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of piezoelectric ceramic materials, in particular to a preparation method of a doped bismuth layer-structured bismuth calcium niobate high-temperature piezoelectric ceramic material. BACKGROUND

[0002] At present, the most widely used piezoelectric ceramic material is lead zirconate titanate piezoelectric ceramic, but this kind of piezoelectric ceramic contains lead, which is harmful to the environment and human body in the production, use and waste treatment processes, and the Curie temperature of this kind of piezoelectric ceramic is generally below 400 DEG C. Due to the existence of the depolarization phenomenon of piezoelectric materials, the piezoelectric materials cannot work normally above the Curie temperature. With the rapid development of aerospace, geological exploration and other work and the demand for sustainable development of human society, it is necessary to seek an environmentally friendly piezoelectric material with high Curie temperature and excellent piezoelectric performance.

[0003] Bismuth layer-structured ceramics have the characteristics of high Curie temperature, small dielectric loss, obvious anisotropy of electromechanical coupling coefficient, high resistivity, no pollution, small leakage current and excellent ferroelectric performance, and are candidate materials suitable for high-temperature environments. The bismuth layer-structured ceramic material is composed of bismuth layer-structured (Bi2O2) 2+ and perovskite structure lattice layers, and its chemical formula is (Bi2O2) 2+ (A m-1 B m O 3m+1 ) 2- Among them, CaBi2Nb2O9 (CBN) is a typical bismuth layer-structured ferroelectric material, A is 12-coordinated Ca 2 + , B is 6-coordinated Nb 5+ , m=2, composed of fluorite structure (Bi2O2) 2+ layer and perovskite structure CaNb2O3 layer, and the Curie temperature (T C ≈943 DEG C) of the material is the highest among bismuth layer-structured ceramics, but the piezoelectric constant is very low (d 33 ≈6 pC / N). Therefore, how to maintain high Curie temperature while improving piezoelectric activity and obtaining CBN piezoelectric ceramic material with excellent comprehensive electrical performance has become an important research topic in the field of high-temperature piezoelectric ceramic materials. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, provide a Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, and for the Ca 2+ ion at the A site of the CaBi2Nb2O9 ceramic material, K + , Ba 2+ , Y3+ The composite high-valence ion [Na 0.2 Sr 0.4 Ce 0.4 ] 2.6+ The Nb 5+ ion at the B site is doped and substituted by Cr 2+ , Ta 5+ , Mo 6+ with 6 coordination. 0.05 Ta 0.3 Mo 0.65 ] 5.5+ The doping substitution is performed so that the piezoelectric performance and high-temperature resistivity are improved while the high Curie temperature is maintained through the above-mentioned composite doping modification, thereby providing a new type of environment-friendly piezoelectric ceramic material with excellent comprehensive electrical performance. Another purpose of the present application is to provide a preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material.

[0005] The purpose of the present application is achieved by the following technical solutions.

[0006] The Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material provided by the present application is composed of the composite high-valence ion [Na + , Ba 2+ , Y 3+ with 12 coordination. 0.2 Sr 0.4 Ce 0.4 ] 2.6+ The Ca 2+ ion at the A site in CaBi2Nb2O9 is doped and substituted by the composite high-valence ion [Cr 2+ , Ta 5+ , Mo 6+ with 6 coordination. 0.05 Ta 0.3 Mo 0.65 ] 5.5+ The Nb 5+ ion at the B site in CaBi2Nb2O9 is doped and substituted by the composite high-valence ion [Cr 1-x , Ta 0.2 , Mo 0.4 ] 0.4 ] x Bi2Nb 2-y [Cr 0.05 Ta 0.3 Mo 0.65 ] y O9, wherein 0.015≤x≤0.045 and 0.025≤y≤0.06.

[0007] In the above scheme, the piezoelectric ceramic material of the present application has a d 33 ≥21.5 pC / N, T C ≥900℃; 500℃, resistivity (ρ) ≥4.2×10 8 Ω·cm, dielectric loss (tan δ) ≤0.20%; d 33 ≥18.2 pC / N after annealing at 800℃.

[0008] Another object of the present application is achieved by the following technical scheme:

[0009] The present application provides a preparation method of the above Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, comprising the following steps:

[0010] (1) Preparation of pre-synthesized precursor powder

[0011] CaCO3, Na2CO3, SrCO3, CeO2, Bi2O3, Nb2O5, Cr2O3, Ta2O5, and MoO3 are used as raw materials corresponding to Ca, Na, Sr, Ce, Bi, Nb, Cr, Ta, and Mo in the chemical formula; the raw materials are weighed according to the stoichiometry in the chemical formula, then subjected to a first ball milling treatment with anhydrous ethanol as the ball milling medium, and the obtained material is dried, sieved, and pressed into a shape, and then subjected to calcination treatment in a sealed crucible; then the calcined material is ground, sieved, and subjected to a second ball milling treatment, and the obtained material is dried, ground, and sieved to obtain the pre-synthesized precursor powder;

[0012] (2) Preparation of high-temperature piezoelectric ceramic material

[0013] The pre-synthesized precursor powder is loaded into a graphite mold and subjected to a first calcination treatment in a spark plasma sintering furnace to obtain a carbon-containing sintered product; then the carbon-containing sintered product is subjected to a second calcination treatment in a general high-temperature furnace under an air atmosphere to remove carbon and obtain a decarburized sintered product; finally, the decarburized sintered product is subjected to polarization treatment to obtain the high-temperature piezoelectric ceramic material.

[0014] Further, in the preparation method, the pressure for pressing into a shape in step (1) is 4-6 MPa; the calcination treatment is performed by increasing the temperature to 830-880℃ at a rate of 5℃ / min and maintaining the temperature for 3-5 h.

[0015] Further, the step (2) of the preparation method is once calcination treatment, the pressure of the discharge plasma sintering furnace is 40-45 MPa, the direct current pulse current is 600-650 A, the temperature is first increased to 900 DEG C at the rate of 100 DEG C / min, then increased to 950-1000 DEG C at the rate of 20 DEG C / min, after keeping warm for 5-6 min, the temperature is decreased to 600 DEG C at the rate of 50 DEG C / min, the direct current pulse current is stopped, then the pressure is released, and the furnace is cooled to room temperature; the secondary calcination treatment is to increase to 700-750 DEG C at the rate of 5 DEG C / min, keep warm for 4-4.5 h, and cool to room temperature with the furnace.

[0016] In the above scheme, the polarization treatment in the step (2) of the preparation method is that the surface of the decarburization fired product is first polished; then the upper and lower surfaces of the polished decarburization fired product are coated with silver electrodes; then calcination is carried out at the rate of 5 DEG C / min to 700-800 DEG C, keeping warm for 20-30 min, and cooling to room temperature with the furnace; finally, polarization is carried out in high-temperature silicon oil at 180-200 DEG C under the direct current voltage of 10-15 kV / mm, and the polarization time is 25-35 min.

[0017] The product prepared by the preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material.

[0018] The present application has the following beneficial effects:

[0019] (1) In the process of preparing CaBi2Nb2O9 piezoelectric ceramic material, bismuth vacancies are inevitably formed due to the volatilization of bismuth at high temperature, thus generating vacancy defects. In view of this phenomenon, the present application adopts the composite high-valence ion [Na 2+ Sr 0.2 Ce 0.4 ] 0.4 with higher valence than the A-site Ca 2.6+ ion to dope and replace it, so as to improve the mixing entropy of the material. At the same time, the composite ion [Cr 5+ Ta 0.05 Mo 0.3 ] 0.65 with higher valence than the B-site Nb 5.5+ ion is doped and replaced, so that both A and B sites generate electrons due to defects, thus enhancing the bismuth oxygen layer (Bi2O2) m-1 and the perovskite-like layer (ABO m ) 3m+1 . 2- 2+ m-1 m 3m+1 2- ​​​​​The interaction between the two kinds of ions can further regulate the growth behavior of the crystal grains, and make the local crystal grains polarized, so that the CaBi2Nb2O9 high-temperature piezoelectric ceramic material with excellent performance is finally obtained.

[0020] (2) The advanced spark plasma sintering technology is adopted in the application, and the sintering temperature and time required by the sintering technology are low, so that the energy consumption is low, and the material has high density after sintering, and the CaBi2Nb2O9 high-temperature piezoelectric ceramic material with excellent performance can be obtained.

[0021] (3) The CaBi2Nb2O9 piezoelectric ceramic material of the application is doped with Na, Sr and Ce at the Ca site, and Cr, Ta and Mo at the Nb site, the Curie temperature is above 900 DEG C, the piezoelectric constant d 33 ≥21.5pC / N, the d 33 ≥18.2pC / N after 800 DEG C annealing, the resistivity is ≥4.2*10 8 Ω*cm at 500 DEG C, and the dielectric loss is ≤0.20%. The material has good high-temperature stability, and can fully meet the application requirements of piezoelectric ceramic sensors, transducers, brakes and other elements in high-temperature environment, and has a wide application prospect in high-temperature electronic equipment.

[0022] (4) The advanced ceramic preparation process is adopted in the preparation method of the application, the sintering temperature is low, the preparation cost is low, the process is simple and easy to operate, the influencing factors are easy to control, and the application is suitable for large-scale industrial production and is helpful to popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0023] The application will be further described in detail below with reference to the embodiments and the drawings:

[0024] Figure 1 is the XRD crystal phase spectrum of the piezoelectric ceramic material of the embodiment and the comparative example of the application;

[0025] Figure 2 is the piezoelectric constant d 33 of the piezoelectric ceramic material of the embodiment and the comparative example of the application. DETAILED DESCRIPTION

[0026] Example 1:

[0027] The preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped type CaBi2Nb2O9 high-temperature piezoelectric ceramic material in the embodiment is disclosed, the chemical general formula of the piezoelectric ceramic material is Ca 1.96 [Na 0.2 Sr 0.4 Ce 0.4 ] 0.04 Bi2Nb 1.97 [Cr 0.05 Ta0.3 Mo 0.65 ] 0.03 O9, the preparation method and steps are as follows:

[0028] (1) Preparation of pre-synthesized precursor powder

[0029] Using CaCO3, Na2CO3, SrCO3, CeO2, Bi2O3, Nb2O5, Cr2O3, Ta2O5, and MoO3 with a purity of 99.9% as raw materials corresponding to Ca, Na, Sr, Ce, Bi, Nb, Cr, Ta, and Mo in the above general chemical formulas, the raw materials were weighed according to the stoichiometry in the above general chemical formulas. Then, anhydrous ethanol was used as the ball milling medium, and the ratio of ball:material:anhydrous ethanol was 4:1:3, at a rotation speed of 400 r / s. The material was first ball-milled on a planetary ball mill for 24 hours. The resulting material was dried, passed through an 80-mesh sieve, pressed into shape at 4 MPa, and placed in a sealed crucible. It was then calcined at 830°C in an oxidizing atmosphere at a rate of 5°C / min for 5 hours. The calcined material was then ground, passed through an 80-mesh sieve, and then ball-milled a second time using the same process as the first ball milling. The resulting material was then dried, ground, and passed through an 80-mesh sieve to obtain the pre-synthesized precursor powder.

[0030] (2) Preparation of high temperature piezoelectric ceramic materials

[0031] (2-1) Take 0.8g of the above pre-synthesized precursor powder and put it into a cylindrical graphite mold with a diameter of 20mm. Place it in a spark plasma sintering furnace, set the pressure to 44MPa and the DC pulse current to 640A. First, heat the furnace to 900℃ at 100℃ / min, then heat it to 960℃ at 20℃ / min for one calcination treatment. After holding the temperature for 6min, reduce the temperature to 600℃ at a cooling rate of 50℃ / min, stop the DC pulse current, release the pressure, and cool the furnace to room temperature to obtain carbon-containing calcined products.

[0032] (2-2) The above carbon-containing calcined products are placed in a common high-temperature furnace and subjected to a second calcination treatment at 750°C at 5°C / min under an air atmosphere to decarbonize. The temperature is maintained for 4 hours and then cooled to room temperature with the furnace to obtain decarbonized calcined products.

[0033] (2-3) The above decarburized calcined product is subjected to the following polarization treatment: First, the surface of the above decarburized calcined product is polished; then, electrode coating treatment is performed, that is, silver electrodes are applied to the upper and lower surfaces of the polished decarburized calcined product; then, the temperature is increased to 800℃ at 5℃ / min and calcined for 20min, and then cooled to room temperature in the furnace; finally, a DC voltage of 10~15kV / mm is applied in high-temperature silicone oil at 180℃ for polarization, and the polarization time is 25min, thus obtaining the high-temperature piezoelectric ceramic material.

[0034] Embodiment Two

[0035] The embodiment is a preparation method of a Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, which is different from Embodiment One in that:

[0036] 1. The chemical general formula of the embodiment is Ca 1.97 [Na 0.2 Sr 0.4 Ce 0.4 ] 0.03 Bi2Nb 1.95 [Cr 0.05 Ta 0.3 Mo 0.65 ] 0.05 O9.

[0037] 2. The calcination temperature in step (1) is 860℃, and the holding time is 4h.

[0038] 3. The calcination system in step (2-1) is as follows: the pressure is set to 42MPa, the direct current pulse current is 620A, the temperature is first increased to 900℃ at a rate of 100℃ / min, then increased to 980℃ at a rate of 20℃ / min, and one calcination treatment is performed, and after holding for 5min, the temperature is decreased to 600℃ at a rate of 50℃ / min, the direct current pulse current is stopped, then the pressure is released, and the furnace is cooled to room temperature, to obtain a carbon-containing calcined product.

[0039] Embodiment Three

[0040] The embodiment is a preparation method of a Na / Ba / Nd / Ga / Sb / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, which is different from Embodiment One in that:

[0041] 1. The chemical general formula of the embodiment is Ca 1.98 [Na 0.2 Sr 0.4 Ce 0.4 ] 0.02 Bi2Nb 1.94 [Cr 0.05 Ta 0.3 Mo 0.65 ] 0.06 O9.

[0042] 2. The calcination temperature in step (1) is 880℃, and the holding time is 3.5h.

[0043] 3. The calcination process in step (2-1) is as follows: set the pressure to 42MPa and the DC pulse current to 620A. First, raise the temperature to 900℃ at 100℃ / min, then raise it to 950℃ at 20℃ / min for one calcination treatment. After holding the temperature for 5min, lower the temperature to 600℃ at a cooling rate of 50℃ / min, stop the DC pulse current, then release the pressure, and cool the furnace to room temperature to obtain carbon-containing calcined products.

[0044] Comparative example:

[0045] An undoped high-temperature piezoelectric ceramic material with the general chemical formula CaBi2Nb2O9 was used as a comparative example, and its preparation steps were the same as in Example 1.

[0046] The XRD phase diagrams of the piezoelectric ceramic materials in the embodiments and comparative examples of this invention are as follows: Figure 1 As shown, from Figure 1 As can be seen from the data, the diffraction peaks of the piezoelectric ceramic materials prepared in each embodiment and comparative example are in complete agreement with the standard spectrum PDF 00-49-0608, indicating that the obtained materials are single-phase CaBi2Nb2O9 materials.

[0047] The piezoelectric constant d of the piezoelectric ceramic materials in the embodiments and comparative examples of the present invention 33 The curve of temperature change is as follows Figure 2 As shown. From Figure 2 It can be seen that, from room temperature to 600℃, the d of the piezoelectric ceramic material in the embodiments of the present invention... 33 The value decreases slightly with increasing temperature; at 800℃, d 33 The value remains above 85% of that at room temperature, indicating that the material has good temperature stability, which is beneficial for its application in high-temperature fields.

[0048] The performance test results of the piezoelectric ceramic materials in the embodiments and comparative examples of the present invention are shown in Table 1.

[0049] Table 1. Performance of piezoelectric ceramic materials in embodiments and comparative examples of the present invention.

[0050]

Claims

1. A method for preparing a Na / Sr / Ce / Cr / Ta / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material, characterized in that: The high-temperature piezoelectric ceramic material is composed of K with 12 coordination groups. + Ba 2+ Y 3+ The complex high-valence ion [Na] 0.2 Sr 0.4 Ce 0.4 ] 2.6+ Doping of Ca at the A-site in CaBi₂Nb₂O₉ 2+ ions, with Cr having 6 coordination 2+ Ta 5+ Mo 6+ The complex high-valence ion [Cr] 0.05 Ta 0.3 Mo 0.65 ] 5.5+ Nb doping at the B site in CaBi₂Nb₂O₉ 5+ The ions that form the general chemical formula Ca 1-x [Na 0.2 Sr 0.4 Ce 0.4 ] x Bi2Nb 2-y [Cr 0.05 Ta 0.3 Mo 0.65 ] y O9, where 0.015≤x≤0.045, 0.025≤y≤0.06; the preparation method includes the following steps: (1) Preparation of pre-synthesized precursor powder Using CaCO3, Na2CO3, SrCO3, CeO2, Bi2O3, Nb2O5, Cr2O3, Ta2O5, and MoO3 as raw materials corresponding to Ca, Na, Sr, Ce, Bi, Nb, Cr, Ta, and Mo in the general chemical formula, the raw materials are proportioned according to the stoichiometry in the general chemical formula. Then, anhydrous ethanol is used as the ball milling medium for a first ball milling process. The resulting material is dried, sieved, pressed into shape, and then placed in a sealed crucible for calcination. The calcined material is then ground, sieved, and subjected to a second ball milling process. The resulting material is dried, ground, and sieved to obtain the pre-synthesized precursor powder. (2) Preparation of high-temperature piezoelectric ceramic materials The pre-synthesized precursor powder is loaded into a graphite mold and placed in a spark plasma sintering furnace for a first calcination treatment to obtain a carbon-containing calcined product. Then, the carbon-containing calcined product is placed in a conventional high-temperature furnace for a second calcination treatment in an air atmosphere to decarburize it, resulting in a decarburized calcined product. Finally, the decarburized calcined product is subjected to polarization treatment to obtain a high-temperature piezoelectric ceramic material.

2. The preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material according to claim 1, characterized in that: The pressing pressure in step (1) is 4-6 MPa; the calcination treatment is to raise the temperature to 830-880℃ at 5℃ / min and keep it at that temperature for 3-5 h.

3. The preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material according to claim 1, characterized in that: In step (2), the first calcination process is as follows: the pressure of the discharge plasma sintering furnace is 40-45 MPa and the DC pulse current is 600-650 A. The temperature is first raised to 900°C at 100°C / min, then raised to 950-1000°C at 20°C / min, held for 5-6 min, and then lowered to 600°C at a cooling rate of 50°C / min. The DC pulse current is then stopped, the pressure is released, and the furnace is cooled to room temperature. The second calcination process is as follows: the temperature is raised to 700-750°C at 5°C / min, held for 4-4.5 h, and then cooled to room temperature.

4. The preparation method of the Na / Sr / Ce / Cr / Ta / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material according to claim 1, characterized in that: The polarization process in step (2) involves first polishing the surface of the decarburized product; then applying an electrode coating, i.e., applying silver electrodes to the upper and lower surfaces of the polished decarburized product; then calcining at 5°C / min to 700-800°C, holding for 20-30 min, and then cooling to room temperature in the furnace; finally, polarizing in high-temperature silicone oil at 180-200°C with a DC voltage of 10-15 kV / mm for 25-35 min.

5. The product prepared using the method for preparing Na / Sr / Ce / Cr / Ta / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material according to any one of claims 1-4, characterized in that: The piezoelectric ceramic material d 33 ≥21.5 pC / N T C ≥900℃; resistivity at 500℃ ( ρ )≥4.2×10 8 Ω·cm, dielectric loss (tan δ ≤0.20%; after annealing at 800℃ d 33 ≥18.2pC / N.

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