Na / ba / nb / ga / sb / mo doped caBi2Nb2O9 high-temperature piezoelectric ceramic material and preparation method thereof

Abstract

This invention discloses a Na / Ba / Nd / Ga / Sb / Mo 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 Na with 12 coordination groups + Ba 2+ 、Nd 3+ Composition of complex high-valence ions [Na 0.15 Ba 0.3 Nd 0.55 ] 2.4+ Doping substitution is performed on Nb at the B site. 5+ Ions, using Ga with 6 coordination groups 2+ Sb 5+ Mo 6+ Composition of complex high-valence ions [Ga 0.05 Sb 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+ layers and perovskite structure lattice layers, and its chemical general 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+ layers and perovskite structure CaNb2O3 layers, 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, and provide a Na / Ba / Nd / Ga / Sb / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material. Aiming at the Ca 2+ ions in the A position of the CaBi2Nb2O9 ceramic material, Na + , Ba 2+, Nd 3+ The composite high-valence ion [Na 0.15 Ba 0.3 Nd 0.55 ] 2.4+ The doping substitution is carried out on the Nb 5+ ion at the B site, and the composite high-valence ion Ga 2+ , Sb 5+ , Mo 6+ is used. 0.05 Sb 0.3 Mo 0.65 ] 5.5+ The doping substitution is carried out 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 / Ba / Nd / Ga / Sb / 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 / Ba / Nd / Ga / Sb / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material provided by the present application is composed of the composite high-valence ion [Na + , Ba 2+ , Nd 3+ ] 0.15 Ba 0.3 Nd 0.55 ] 2.4+ The Ca 2+ ion at the A site in CaBi2Nb2O9 is doped and substituted, and the composite high-valence ion [Ga 2+ , Sb 5+ , Mo 6+ ] 0.05 Sb 0.3 Mo 0.65 ] 5.5+ The Nb 5+ ion at the B site in CaBi2Nb2O9 is doped and substituted, and the chemical general formula of the formed product is Ca 1-x [Na 0.15 Ba 0.3 Nd 0.55 ] x Bi2Nb 2-y [Ga 0.05 Sb 0.3 Mo 0.65 ] yO9, wherein 0.025≤x≤0.065, 0.02≤y≤0.055.

[0007] In the above scheme, the piezoelectric ceramic material of the present application has a d 33 ≥ 20.0 pC / N, T C ≥ 900℃; the resistivity (ρ) is ≥ 3.5×10 8 Ω·cm, the dielectric loss (tanδ) is ≤ 0.25%; the d 33 ≥ 17.0 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 Na / Ba / Nd / Ga / Sb / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, comprising the following steps:

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

[0011] CaCO3, Na2CO3, BaCO3, Nd2O3, Bi2O3, Nb2O5, Ga2O3, Sb2O3, and MoO3 are used as raw materials corresponding to Ca, Na, Ba, Nd, Bi, Nb, Ga, Sb, and Mo 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 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 to raise the temperature to 830-880℃ at a rate of 5℃ / min and keep 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 / Ba / Nd / Ga / Sb / 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+ Ba 0.15 Nd 0.3 ] 0.55 2.4+ with higher valence than the A-site Ca 5+ ion to dope and replace it, so as to improve the mixing entropy of the material. At the same time, the composite ion [Ga 0.05 Sb 0.3 Mo 0.65 ] 5.5+ with higher valence than the B-site Nb m-1 ion is doped and replaced, so that both A and B sites generate electrons due to defects, thus enhancing the bismuth oxide layer (Bi2O2) m and the perovskite-like layer (ABO 3m+1 ) 2- . 2+ m-1 m 3m+1 2- ​​​​​The interaction between the two types of defects can further regulate the growth behavior of the crystal grains, and thus locally produce polar nanodomains, 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 doped with Na, Ba and Nd at the Ca site and doped with Ga, Sb and Mo at the Nb site has a Curie temperature of more than 900 DEG C, a piezoelectric constant d 33 ≥ 20.0 pC / N, a d 33 ≥ 17.0 pC / N after 800 DEG C annealing, a resistivity ≥ 3.5 x 10 8 Ω·cm at 500 DEG C, and a dielectric loss ≤ 0.25%. 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 accompanying 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 / Ba / Nd / Ga / Sb / Mo 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 [Na 0.15 Ba 0.3 Nd 0.55 ] 0.06 Bi2Nb 1.975 [Ga 0.05 Sb0.3 Mo 0.65 ] 0.025 O9, a method for preparing the same, the steps of which are as follows:

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

[0029] CaCO3, Na2CO3, BaCO3, Nd2O3, Bi2O3, Nb2O5, Ga2O3, Sb2O3, and MoO3 with a purity of 99.9% are used as raw materials corresponding to Ca, Na, Ba, Nd, Bi, Nb, Ga, Sb, and Mo 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 using 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 850°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 placed in a cylindrical graphite mold with a diameter of 20 mm, and placed in a spark plasma sintering furnace. The pressure is set to 40 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 then the pressure is released. The material is 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 general 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, the upper and lower surfaces of the polished decarburized sintered product are coated with silver electrodes. The material is then calcined at a rate of 5°C / min to 750°C for 30 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] Embodiment Two:

[0035] The embodiment is a preparation method of Na / Ba / Nd / Ga / Sb / 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:

[0037] Ca 0.95 [Na 0.15 Ba 0.3 Nd 0.55 ] 0.05 Bi2Nb 1.96 [[Ga 0.05 Sb 0.3 Mo 0.65 ] 0.04 O9.

[0038] 2、The calcination temperature in step (1) is 860℃, and the holding time is 5h.

[0039] 3、The calcination system in step (2-1) is: the pressure is set to 45MPa, the direct current pulse current is 620A, first heated to 900℃ at 100℃ / min, then heated to 1000℃ at 20℃ / min, once calcined, after holding for 5min, the temperature is reduced 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.

[0040] Embodiment Three:

[0041] The embodiment is a preparation method of Na / Ba / Nd / Ga / Sb / Mo doped CaBi2Nb2O9 high-temperature piezoelectric ceramic material, which is different from Embodiment One in that:

[0042] 1、The chemical general formula of the embodiment is:

[0043] Ca 0.975 [Na 0.15 Ba 0.3 Nd 0.55 ] 0.025 Bi2Nb 1.95 [[Ga 0.05 Sb 0.3 Mo 0.65 ] 0.05 O9.

[0044] 2、The calcination temperature in step (1) is 860℃, and the holding time is 3.5h.

[0045] 3. The calcination process in step (2-1) is as follows: set the pressure to 45MPa 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.

[0046] Comparative example:

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The performance test results of the piezoelectric ceramic materials in the embodiments and comparative examples of the present invention are shown in Table 1.

[0051] Table 1. Performance of piezoelectric ceramic materials in embodiments and comparative examples of the present invention.

[0052]

Claims

1. A method for preparing a Na / Ba / Nd / Ga / Sb / Mo doped CaBi₂Nb₂O₉ high-temperature piezoelectric ceramic material, characterized in that: The high-temperature piezoelectric ceramic material is a composite high-valence ion [Na + , Ba 2+ , Nd 3+ ] with 12 coordination 0.15 , Ba 0.3 , Nd 0.55 ] 2.4+ Doping substitutes Ca in the A position of CaBi2Nb2O9 2+ Ion, a composite high-valence ion [Ga 2+ , Sb 5+ , Mo 6+ ] with 6 coordination 0.05 , Sb 0.3 , Mo 0.65 ] 5.5+ Doping substitutes Nb in the B position of CaBi2Nb2O9 5+ Ion, forming a chemical general formula of Ca 1-x [Na 0.15 , Ba 0.3 , Nd 0.55 ] x Bi2Nb 2-y [Ga 0.05 , Sb 0.3 , Mo 0.65 ] y O9, wherein 0.025≤x≤0.065, 0.02≤y≤0.055; the preparation method comprises the following steps: (1) Preparation of pre-synthesized precursor powder CaCO3, Na2CO3, BaCO3, Nd2O3, Bi2O3, Nb2O5, Ga2O3, Sb2O3, MoO3 are used as raw materials corresponding to Ca, Na, Ba, Nd, Bi, Nb, Ga, Sb, Mo 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 the Na / Ba / Nd / Ga / Sb / Mo 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 the Na / Ba / Nd / Ga / Sb / Mo 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 the Na / Ba / Nd / Ga / Sb / Mo 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 1-4, wherein the product is characterized in that: the piezoelectric ceramic material d 33 ≥ 20.0 pC / N, T C ≥ 900 °C; resistivity at 500 °C ρ ) ≥ 3.5 x 10 8 Ω-cm, dielectric loss (tan δ ) ≤ 0.25%; after annealing at 800 °C d 33 ≥ 17.0 pC / N.

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