K / ba / y / cr / v / w doped ca bi2nb2o9 high-temperature piezoelectric ceramic material and preparation method thereof

Abstract

This invention discloses a K / Ba / Y / Cr / V / W-doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material and its preparation method, 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 [K 0.2 Ba 0.2 Y 0.6 ] 2.4+ Doping substitution is performed on Nb at the B site. 5+ Ions, using Cr with 6 coordination groups 2+ V 5+ W 6+ Composition of complex high-valence ions [Cr 0.1 V 0.2 W 0.7 ] 5.4+ 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 present application relates to the technical field of piezoelectric ceramic materials, and particularly relates 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 type of piezoelectric ceramic contains lead, which is harmful to the environment and human body in the production, use and waste disposal processes, and the Curie temperature of this type 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 properties.

[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 properties, 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 properties 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 K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, and for the Ca 2+ ions in the A position of the CaBi2Nb2O9 ceramic material, K + , Ba 2+ , Y 3+The composite high-valence ion [K 0.2 Ba 0.2 Y 0.6 ] 2.4+ The Nb 5+ ion at the B site is doped and substituted by Cr 2+ , V 5+ , and W 6+ to form a composite high-valence ion [Cr 0.1 V 0.2 W 0.7 ] 5.4+ The doped and substituted CaBi2Nb2O9 is modified by the above-mentioned composite doping to improve the piezoelectric performance and high-temperature resistivity while maintaining a high Curie temperature, thereby providing a new type of environmentally friendly piezoelectric ceramic material with excellent comprehensive electrical properties. Another purpose of the present application is to provide a preparation method of the K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material.

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

[0006] The K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material provided by the present application is composed of a composite high-valence ion [K + , Ba 2+ , and Y 3+ with 12 coordination. 0.2 Ba 0.2 Y 0.6 ] 2.4+ The Ca 2+ ion at the A site of CaBi2Nb2O9 is doped and substituted by a composite high-valence ion [Cr 2+ , V 5+ , and W 6+ with 6 coordination. 0.1 V 0.2 W 0.7 ] 5.4+ The Nb 5+ ion at the B site of CaBi2Nb2O9 is doped and substituted by a composite high-valence ion [Cr 1-x , V 0.2 , and W 0.2 ] 0.6 ] x Bi2Nb 2-y [Cr 0.1 V 0.2 W 0.7 ] y O9, wherein 0.02≤x≤0.065 and 0.015≤y≤0.04.

[0007] In the above scheme, the piezoelectric ceramic material of the present application has a d 33 ≥ 19 pC / N, T C ≥ 893℃; 500℃, resistivity (p) ≥ 2.5 x 10 8 Ω·cm, dielectric loss (tan delta) ≤ 0.35%; d 33 ≥ 16 pC / N.

[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-mentioned K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, comprising the following steps:

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

[0011] CaCO3, K2CO3, BaCO3, Y2O3, Bi2O3, Nb2O5, Cr2O3, V2O5, and WO3 are used as raw materials corresponding to Ca, K, Ba, Y, Bi, Nb, Cr, V, and W in the chemical formula; the raw materials are weighed according to the stoichiometry in the chemical formula, and then subjected to a first ball milling treatment with anhydrous ethanol as the ball milling medium; 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, thereby obtaining a carbon-removed sintered product; finally, the carbon-removed sintered product is subjected to polarization treatment to obtain the high-temperature piezoelectric ceramic material.

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

[0015] Further, in step (2) of the preparation method of the present invention, the first calcination treatment is as follows: the pressure of the discharge plasma sintering furnace is 40-45 MPa and the DC pulse current is 600-650 A. First, the temperature is 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 stopped, and then the pressure is released and the furnace is cooled to room temperature. The second calcination treatment 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.

[0016] In the above scheme, the polarization treatment in step (2) of the preparation method of the present invention is as follows: first, the surface of the 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 700-800℃ at 5℃ / min and calcined for 20-30min, and then cooled to room temperature in the furnace; finally, polarization is performed in high-temperature silicone oil at 180-200℃ with a DC voltage of 10-15kV / mm for 25-35min.

[0017] The product was prepared using the above-mentioned method for preparing K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic materials.

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

[0019] (1) During the preparation of CaBi₂Nb₂O₉ piezoelectric ceramic materials, bismuth volatilization at high temperatures inevitably leads to the formation of bismuth vacancies, resulting in vacancy defects. To address this phenomenon, this invention employs a valence ratio A-site Ca... 2+ High-valence complex ions [K] 0.2 Ba 0.2 Y 0.6 ] 2.4+ Doping and substitution are performed to increase the mixing entropy of the material. Simultaneously, the valence ratio of B-site Nb is employed. 5+ High-concentration complex ions [Cr] 0.1 V 0.2 W 0.7 ] 5.4+ Doping and substitution are performed on it so that both A and B sites have defects that cause the perovskite-like layer (A) to be formed. m- 1B m O 3m+1 ) 2- Electrons are generated, thereby strengthening the bismuth-oxygen layer (Bi2O2). 2+ and perovskite-like layer (A m-1 B m O 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 density of the material after sintering is high, and the CaBi2Nb2O9 high-temperature piezoelectric ceramic material with excellent performance can be obtained.

[0021] (3) The CaBi2Nb2O9 piezoelectric ceramic material doped with K, Ba and Y at the Ca site and Cr, V and W at the Nb site has a Curie temperature of more than 893℃, a piezoelectric constant d 33 ≥ 19 pC / N, a d 33 ≥ 16 pC / N after annealing at 800℃, a resistivity ≥ 2.5 × 10 8 Ω·cm at 500℃, and a dielectric loss ≤ 0.35%. 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 fields, and has a wide application prospect in high-temperature electronic equipment.

[0022] (4) The advanced ceramic preparation process is adopted in the preparation method, 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 method is suitable for large-scale industrial production and is helpful for 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 One:

[0027] The preparation method of the K / Ba / Y / Cr / V / W doped type CaBi2Nb2O9 high-temperature piezoelectric ceramic material in the embodiment is disclosed, and the chemical general formula of the piezoelectric ceramic material is Ca 0.94 [K 0.2 Ba 0.2 Y 0.6 ] 0.06 Bi2Nb 1.985 [Cr 0.1 V 0.2 W0.7 0.015 O9, a preparation method of which comprises the following steps:

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

[0029] CaCO3, K2CO3, BaCO3, Y2O3, Bi2O3, Nb2O5, Cr2O3, V2O5, WO3 with a purity of 99.9% are used as raw materials corresponding to Ca, K, Ba, Y, Bi, Nb, Cr, V, and W in the above chemical formula. The raw materials are weighed according to the stoichiometry in the above chemical formula, and then ball-milled in a planetary ball mill at a rotation speed of 400 r / min for 24 h with anhydrous ethanol as the ball-milling medium, with a ball: material: anhydrous ethanol ratio of 4:1:3. The obtained material is dried, sieved through an 80-mesh sieve, and then pressed into a shape under a pressure of 4 MPa. The shaped material is placed in a sealed crucible, heated to 840°C at a rate of 5°C / min, and calcined in an oxidizing atmosphere for 4 h. The calcined material is ground, sieved through an 80-mesh sieve, and then subjected to a second ball-milling treatment using the same process as the first ball-milling treatment. The obtained material is dried, ground, and sieved through an 80-mesh sieve to obtain the pre-synthesized precursor powder.

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

[0031] (2-1) 0.8 g of the above pre-synthesized precursor powder is loaded into a cylindrical graphite mold with a diameter of 20 mm, and placed in a spark plasma sintering furnace. The pressure is set to 45 MPa, and the direct current pulse current is set to 600 A. The temperature is first raised to 900°C at a rate of 100°C / min, and then raised to 960°C at a rate of 20°C / min. The material is subjected to a first calcination treatment, and then cooled to 600°C at a rate of 50°C / min. The direct current pulse current is stopped, and the pressure is released. The material is then cooled to room temperature in the furnace to obtain a carbon-containing sintered product.

[0032] (2-2) The carbon-containing sintered product is placed in a conventional high-temperature furnace and subjected to a second calcination treatment in an air atmosphere at a rate of 5°C / min to 750°C for decarburization. The material is kept at this temperature for 4.5 h and then cooled to room temperature in the furnace to obtain a decarburized sintered product.

[0033] (2-3) The decarburized sintered product is subjected to the following polarization treatment. The surface of the decarburized sintered product is first polished. Then, silver electrodes are applied to the upper and lower surfaces of the polished decarburized sintered product. The material is then calcined at a rate of 5°C / min to 800°C for 25 min, and then cooled to room temperature in the furnace. Finally, the material is polarized in a high-temperature silicon oil at 180°C under a direct current voltage of 10-15 kV / mm for 30 min to obtain the high-temperature piezoelectric ceramic material.

[0034] Example Two:​

[0035] The embodiment is a preparation method of K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, which is different from the embodiment one in that:

[0036] 1、The chemical general formula of the embodiment is Ca 0.955 [K 0.2 Ba 0.2 Y 0.6 ] 0.045 Bi2Nb 1.97 [Cr 0.1 V 0.2 W 0.7 ] 0.03 O9.

[0037] 2、The calcination temperature in step (1) is 880 ℃, and the holding time is 5 h.

[0038] 3、The calcination system in step (2-1) is as follows: the pressure is set to 40 MPa, the direct current pulse current is 620 A, the temperature is first increased to 900 ℃ at a rate of 100 ℃ / min, then increased to 1000 ℃ at a rate of 20 ℃ / min, and one calcination treatment is performed, after holding for 5 min, 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 K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, which is different from the embodiment one in that:

[0041] 1、The chemical general formula of the embodiment is Ca 0.975 [K 0.2 Ba 0.2 Y 0.6 ] 0.025 Bi2Nb 1.96 [Cr 0.1 V 0.2 W 0.7 ] 0.04 O9.

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

[0043] 3. The calcination process in step (2-1) is as follows: set the pressure to 40MPa and the DC pulse current to 620A. First, raise the temperature to 900℃ at 100℃ / min, then raise it to 980℃ 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 84% 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 K / Ba / Y / Cr / V / W doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material, characterized in that: One of the high-temperature piezoelectric ceramic materials is a K-type material with 12 coordination groups. + Ba 2+ Y 3+ The complex high-valence ion [K] 0.2 Ba 0.2 Y 0.6 ] 2.4+ Doping of Ca at the A-site in CaBi₂Nb₂O₉ 2+ ions, with Cr having 6 coordination 2+ V 5+ W 6+ The complex high-valence ion [Cr 0.1 V 0.2 W 0.7 ] 5.4+ Nb doping at the B site in CaBi₂Nb₂O₉ 5+ The ions that form the general chemical formula Ca 1-x [K 0.2 Ba 0.2 Y 0.6 ] x Bi2Nb 2-y [Cr 0.1 V 0.2 W 0.7 ] y O9, where 0.02≤x≤0.065, 0.015≤y≤0.04; the preparation method includes the following steps: (1) Preparation of pre-synthesized precursor powder CaCO3, K2CO3, BaCO3, Y2O3, Bi2O3, Nb2O5, Cr2O3, V2O5, WO3 are used as raw materials corresponding to Ca, K, Ba, Y, Bi, Nb, Cr, V, W in the chemical formula; the raw materials are proportioned according to the stoichiometry in the chemical formula, and then subjected to one-time ball milling treatment with anhydrous ethanol as the ball milling medium; 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 and sieved, and subjected to two-time ball milling treatment, and the obtained material is dried, ground, and sieved to obtain the pre-synthesized precursor powder; (2) Preparation of high-temperature piezoelectric ceramic material The pre-synthesized precursor powder is loaded into a graphite mold and subjected to one-time calcination treatment in a spark plasma sintering furnace to obtain a carbon-containing sintered product; then the carbon-containing sintered product is subjected to two-time calcination treatment in an ordinary high-temperature furnace under air atmosphere to remove carbon and obtain a carbon-removed sintered product; finally, the carbon-removed sintered product is subjected to polarization treatment to obtain the high-temperature piezoelectric ceramic material.

2. The preparation method of K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material according to claim 1, characterized in that: In step (1), the pressure for pressing into a shape is 4-6 MPa; the calcination treatment is to increase the temperature to 830-880℃ at a rate of 5℃ / min, and keep the temperature for 3-5 h.

3. The preparation method of K / Ba / Y / Cr / V / W doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material according to claim 1, characterized in that: In step (2), the one-time calcination treatment is to increase the temperature to 900℃ at a rate of 100℃ / min, and then increase the temperature to 950-1000℃ at a rate of 20℃ / min in a spark plasma sintering furnace with a pressure of 40-45 MPa and a direct current pulse current of 600-650 A, keep the temperature for 5-6 min, then decrease the temperature to 600℃ at a rate of 50℃ / min, stop the direct current pulse current, release the pressure, and cool to room temperature in the furnace; the two-time calcination treatment is to increase the temperature to 700-750℃ at a rate of 5℃ / min, keep the temperature for 4-4.5 h, and cool to room temperature in the furnace.

4. The preparation method of K / Ba / Y / Cr / V / W-doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material according to claim 1, characterized in that: In step (2), the polarization treatment is to polish the surface of the carbon-removed sintered product first; then perform electrode coating treatment, i.e. silver electrodes are coated on the upper and lower surfaces of the polished carbon-removed sintered product; then increase the temperature to 700-800℃ at a rate of 5℃ / min, keep the temperature for 20-30 min, and cool to room temperature in the furnace; finally, polarize in high-temperature silicon oil at 180-200℃ with a direct current voltage of 10-15 kV / mm, and the polarization time is 25-35 min.

5. The product prepared by the method of any one of claims 1 to 4, characterized in that: the piezoelectric ceramic material d 33 ≥ 19 pC / N, T C ≥ 893°C; resistivity at 500°C ρ ) ≥ 2.5 x 10 8 Ω-cm, dielectric loss (tan δ ) ≤ 0.35%; after annealing at 800°C d 33 ≥ 16 pC / N.

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