Doped modified lead metaniobate-based high-temperature piezoelectric ceramic and preparation method thereof

Abstract

The application discloses a doped modified lead metaniobate-based high-temperature piezoelectric ceramic and a preparation method thereof. The doped modified lead metaniobate-based high-temperature piezoelectric ceramic has a general formula of PbNb2O6+x mol% Nb2O5+y wt% Sc2O3+z wt% SrCO3+delta mol% Ta2O5; wherein x=0-8, y=0-0.8, z=0-1, and delta=0-12. The application solves the problems of sintering difficulty, low density and low piezoelectric coefficient of pure PbNb2O6 by adding excess Nb2O5; on the basis, Sc 3+ , Sr 2+ , and Ta 5+ ions are doped in sequence, so that the piezoelectric performance of the PbNb2O6-based piezoelectric ceramic is continuously improved while the high Curie temperature is ensured.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramics technology, specifically to a doped and modified lead niobate-based high-temperature piezoelectric ceramic and its preparation method. Background Technology

[0002] Lead metaniobate (PbNb₂O₆) possesses a high Curie temperature and a low mechanical quality factor, making it a promising candidate for applications in high-temperature actuators and sensors. However, the ferroelectric orthorhombic phase of PbNb₂O₆ is metastable, and this ferroelectric phase is difficult to obtain using traditional solid-state sintering methods. The preparation of ferroelectric orthorhombic lead metaniobate is a significant challenge because the trigonal-to-tetragonal phase transition occurs during conventional sintering. This phase transition causes abnormal grain growth in lead metaniobate during ceramic formation, accompanied by cracks and porosity. These defects, along with other factors, result in insufficient piezoelectric properties and low density in lead metaniobate, thus hindering its application in high-temperature fields.

[0003] The aforementioned problems can be improved by doping PbNb2O6-based ceramics. Lead niobate contains three types of vacuoles: A, B, and C. A-vacuoles are further divided into quadrilateral vacuoles (A1) and pentagonal vacuoles (A2); B-vacuoles, due to the varying environments caused by the tilt of the oxygen octahedrons, can be divided into B1 and B2; finally, there are triangular vacuoles (C). Studies have shown that the piezoelectric properties are mainly caused by two factors: domain contribution and spontaneous polarization contribution. Spontaneous polarization is usually caused by the twisting of the oxygen octahedron, and many factors influence the twisting of the oxygen octahedron in the tungsten bronze system, indicating that the properties of lead niobate can be improved through elemental doping. Chemical doping is an effective method to improve the twisting of the oxygen octahedron. The doping modification of lead niobate mainly involves doping the A-site and B-site in the crystal lattice. For co-doping of A and B sites, Wu et al. used a two-step sintering process, using Sr... 2+ Ta 5+ Pb replacing part of A site 2+ With B position Nb 5+ This refines the grain size, achieving a piezoelectric property of 79 pC / N, while slightly reducing the Curie temperature. Furthermore, Venet et al. doped La into PbNb2O6. 3+ This gives PbNb2O6-based ceramics a stable orthorhombic phase, but its Curie temperature drops sharply to around 270℃. Fang et al. increased the density of PbNb2O6-based ceramics by adding an appropriate amount of CuO, obtaining a piezoelectric property of 190 pC / N, but the Curie temperature decreased to 395℃.

[0004] While previous methods of adding other components and modifying the process can improve the density and piezoelectric properties of PbNb2O6-based piezoelectric ceramics, they often simultaneously decrease the Curie temperature. Furthermore, to obtain a stable ferroelectric orthorhombic phase, quenching is required after sintering. There are few reports on multi-element doping (simultaneous substitution at A / B sites) that comprehensively improves the density, sintering performance, piezoelectric properties, and Curie temperature of PbNb2O6-based ceramics. Summary of the Invention

[0005] To address the challenges of sintering difficulties, low density, and insufficient piezoelectric properties in lead niobate-based ceramics, this invention provides a PbNb₂O₆ + x mol% Nb₂O₅ + y wt% Sc₂O₃ + z wt% SrCO₃ + δ mol% Ta₂O₅ doping system. Using conventional solid-state sintering methods, multi-element doping modification is employed to prepare PbNb₂O₆-based ceramics with high piezoelectric coefficients, high Curie temperatures, and high density. Ultimately, a ceramic with high strength and a high piezoelectric coefficient (d...) is successfully prepared. 33 The value is 80 pC / N, and the Curie temperature (T) is... c It is a high-temperature piezoelectric ceramic with a temperature of 636℃.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a doped and modified lead niobate-based high-temperature piezoelectric ceramic, wherein the general formula of the piezoelectric ceramic is PbNb2O6+x mol%Nb2O5+y wt%Sc2O3+z wt%SrCO3+δmol%Ta2O5;

[0008] In the formula, x = 0 - 8, y = 0 - 0.8, z = 0 - 1, and δ = 0 - 12.

[0009] Preferably, in the general formula, 4≤x≤8, 0.1≤y≤0.6, 0.1≤z≤0.8, and 2≤δ≤5.

[0010] A second aspect of the present invention provides a method for preparing the doped and modified lead niobate-based high-temperature piezoelectric ceramic, comprising the following steps:

[0011] (1) Weigh the raw materials PbO, Nb2O5, Sc2O3, SrCO3, and Ta2O5 according to their chemical composition ratio, add water, and then perform the first ball milling.

[0012] (2) The material after the first ball milling is dried and then pre-calcined;

[0013] (3) Add binder, dispersant and defoamer to the pre-calcined material and ball mill it a second time;

[0014] (4) Spray granulation of the material after the second ball milling, press into blocks; then proceed with cold isostatic pressing, debinding, sintering, silvering and polarization to obtain PbNb2O6-based piezoelectric ceramic material.

[0015] Preferably, in step (1), the first ball milling time is 12-14 hours.

[0016] Preferably, in step (2), the pre-firing temperature is 700-900℃ and the time is 2-4h.

[0017] Preferably, in step (3), the mass ratio of the pre-calcined material to the binder, dispersant, and defoamer is 1:(0.005-0.015):(0.005-0.015):(0.005-0.015). This invention does not limit the specific binder, dispersant, and defoamer; any conventionally used reagents are acceptable.

[0018] Preferably, in step (4), the pressure of the cold isostatic pressing is 200-250 MPa, and the holding time is 120-200 s.

[0019] Preferably, in step (4), the temperature of the glue discharge is 450-600℃, and the temperature is maintained for 2-4 hours.

[0020] Preferably, in step (4), the sintering temperature is 1100-1300℃, and the holding time is 2-4h.

[0021] Preferably, in step (4), the polarization step is: applying a DC electric field of 3.0-4.0 Kv / mm to the silicone oil for polarization.

[0022] The high-temperature piezoelectric ceramic prepared by the solid-state synthesis method described in this invention exhibits high density, high strength, and excellent sintering and piezoelectric properties, making it suitable for use in high-temperature sensors. The PbNb2O6-based high-temperature piezoelectric ceramic of this invention belongs to a non-filled tungsten bronze structure material. Depending on the proportion of raw materials, the Curie temperature of the sintered ceramic can be between 450-700℃, and the piezoelectric coefficient d... 33 With a piezoelectric constant between 60-90 Pc / N, this PbNb2O6-based high-temperature piezoelectric ceramic exhibits good density, high strength, and excellent high-temperature stability. X-ray powder diffraction analysis of the prepared PbNb2O6-based high-temperature piezoelectric ceramic (PbNb2O6 + 8 mol% Nb2O5 + 0.2 wt% Sc2O3 + 0.8 wt% SrCO3 + 3 mol% Ta2O5) revealed that the ceramic possesses a tungsten bronze structure at room temperature and is a ferroelectric orthorhombic phase. The piezoelectric constant is 80 Pc / N, and the dielectric constant at room temperature reaches 321 at 10 kHz, with a coercive field E... c It is 23.83 Kv / cm, and the remanent polarization P r 3.96 uc / cm2 The high-temperature piezoelectric ceramic prepared by PbNb2O6 + 8mol%Nb2O5 + 0.2wt%Sc2O3 + 0.8wt%SrCO3 + 3mol%Ta2O5 exhibits good high-temperature stability, with a Curie temperature reaching 636℃.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention employs a traditional solid-state sintering method to prepare PbNb2O6-based piezoelectric ceramics. First, it addresses the difficulties in sintering pure PbNb2O6, such as low density and low piezoelectric coefficient, by adding excess Nb2O5. Building upon this foundation, Sc is then sequentially doped... 3+ 、Sr 2+ Ta 5+ Ions are used to further improve the piezoelectric properties of PbNb₂O₆-based piezoelectric ceramics while ensuring a high Curie temperature. The oxides of these elements were chosen because their ionic radii are similar to the radii of the A / B occupier ions in the PbNb₂O₆ ceramic lattice, allowing for better incorporation and substitution. Multi-element doping increases the piezoelectric coefficient (d) of PbNb₂O₆-based ceramics. 33 The Curie temperature (T) was increased from the initial 46 pC / N to 80 pC / N. c The temperature increased by nearly 12% (from 568℃ to 636℃), and the bulk density increased from 5.69 g / cm³. 3 Increased to 6.30 g / cm³ 3 (Approximately 96% of the theoretical density), an appropriate doping amount can prevent the formation of the non-ferroelectric rhombohedral phase in PbNb2O6-based ceramics, thereby stabilizing the ferroelectric orthorhombic phase and allowing for conventional furnace cooling after ceramic sintering. These results can promote the role of PbNb2O6-based piezoelectric ceramics in the high-temperature piezoelectric field and provide a method for comprehensively improving sintering performance, enhancing piezoelectric properties, and improving high-temperature stability. Attached Figure Description

[0025] Figure 1 X-ray diffraction patterns of PbNb2O6-based piezoelectric ceramics with different x values ​​in Example 2;

[0026] Figure 2 The high-temperature dielectric temperature spectrum of the PbNb2O6-based ceramic when x=8 in Example 2;

[0027] Figure 3 The X-ray diffraction patterns of PbNb2O6-based piezoelectric ceramics with different y values ​​when x=8 in Example 3 are shown.

[0028] Figure 4 The high-temperature dielectric temperature spectrum of PbNb2O6-based ceramics in Example 3 when x = 8 and y = 0.2;

[0029] Figure 5 X-ray diffraction patterns of PbNb2O6-based piezoelectric ceramics with different z values ​​when x=8 and y=0.2 in Example 4;

[0030] Figure 6 The high-temperature dielectric temperature spectrum of PbNb2O6-based ceramics in Example 4 when x = 8, y = 0.2, z = 0.8;

[0031] Figure 7 The image shows the sintered surface of the PbNb2O6-based piezoelectric ceramic with x=8, y=0.2, z=0.8, and δ=3 in Example 5.

[0032] Figure 8 The image shows a scanning electron microscope (SEM) cross-sectional view of the PbNb2O6-based piezoelectric ceramic with x=8, y=0.2, z=0.8, and δ=3 in Example 5.

[0033] Figure 9 The high-temperature dielectric temperature spectrum of PbNb2O6-based ceramics in Example 5 when x = 8, y = 0.2, z = 0.8, and δ = 3;

[0034] Figure 10 The performance parameters of the PbNb2O6-based piezoelectric ceramics in Examples 1-5 are shown below.

[0035] Figure 11 The appearance of the PbNb2O6-based piezoelectric ceramic sintered samples from Examples 2-5;

[0036] Figure 12 The X-ray diffraction patterns are of the PbNb2O6-based piezoelectric ceramics in Examples 1-5. Detailed Implementation

[0037] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0039] Example 1

[0040] This embodiment provides a method for preparing PbNb2O6-based piezoelectric ceramic materials, specifically including the following steps:

[0041] 1) First ball milling: Based on the composition formula PbNb2O6 of PbNb2O6 piezoelectric ceramic material, PbO and Nb2O5 were weighed according to the stoichiometric ratio, and then mixed with agate balls and ultrapure water in a certain proportion (agate balls: raw materials: ultrapure water = 2:1:1.5). The mixture was then ball milled in a planetary ball mill jar for 12 hours.

[0042] 2) Drying: Dry the slurry after one ball milling, put it into a furnace for pre-firing and synthesis, the pre-firing temperature is 800℃, and the temperature is held for 2.5h;

[0043] 3) Secondary ball milling: The pre-calcined and synthesized raw materials are pulverized and passed through a 180-mesh sieve, and then ball milled for 12 hours. At the same time, 1 wt% of binder, 1 wt% of dispersant and 1 wt% of defoamer are added according to the mass of solid raw material powder.

[0044] 4) Spray granulation: The slurry after secondary ball milling is spray granulated, and then the powder is pressed into blocks under a pressure of 10MPa;

[0045] 5) Cold isostatic pressing: pressure at 250MPa, holding time at 180s;

[0046] 6) Debinding and sintering: The sample was debinded and sintered. The debinding temperature was 550℃ (held for 3 hours), and the sintering temperature was 1260℃ (held for 3 hours) to obtain the sample blank.

[0047] 7) Silvering: The ceramic blank is sliced, polished, cleaned, and then silvered, and fired at 700℃.

[0048] 8) Polarization: PbNb2O6-based piezoelectric ceramic materials were prepared by applying a DC electric field of 4Kv / mm in silicone oil at 150℃.

[0049] Example 2

[0050] This embodiment provides a method for preparing PbNb2O6-based piezoelectric ceramic materials, specifically referring to Embodiment 1, including the following steps:

[0051] 1) First ball milling: Based on the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+x mol%Nb2O5, PbO and Nb2O5 are used as raw materials. After weighing according to the stoichiometric ratio, they are mixed with agate balls and ultrapure water in proportion and ball milled in a planetary ball mill jar for 12 hours.

[0052] Steps 2-8 are the same as in Example 1, and PbNb2O6-based piezoelectric ceramic materials are obtained.

[0053] The ceramic properties were tested for different values ​​of x, and the results are shown in Table 1 and Appendix 2. Figure 1-2 As shown in Table 1. Table 1 illustrates the effect of different values ​​of x on various properties of PbNb2O6-based piezoelectric ceramics; Figure 1 This indicates the effect of different values ​​of x on the ceramic phase; Figure 2 The curves represent the relationship between the dielectric constant and dielectric loss of PbNb2O6-based ceramics at different frequencies and temperature when x = 8.

[0054] Table 1

[0055]

[0056] Example 3

[0057] This embodiment provides a method for preparing PbNb2O6-based piezoelectric ceramic materials, specifically referring to Embodiment 1, including the following steps:

[0058] 1) First ball milling: Based on the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+8mol%Nb2O5+ywt%Sc2O3, PbO, Nb2O5, and Sc2O3 were weighed according to the stoichiometric ratio, and then mixed with agate balls and ultrapure water in proportion. The mixture was then ball-milled in a planetary ball mill jar for 12 hours.

[0059] Steps 2-8) are the same as in Example 1, and PbNb2O6-based piezoelectric ceramic materials are obtained.

[0060] Figure 3 This represents the effect of different values ​​of y on the phase when x = 8; Figure 4 The graph shows the relationship between the dielectric constant and dielectric loss of PbNb2O6-based ceramics at different frequencies and temperature when x = 8 and y = 0.2.

[0061] Example 4

[0062] This embodiment provides a method for preparing PbNb2O6-based piezoelectric ceramic materials, specifically referring to Embodiment 1, including the following steps:

[0063] 1) First ball milling: Based on the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+8mol%Nb2O5+0.2wt%Sc2O3+zwt%SrCO3, PbO, Nb2O5, Sc2O3, and SrCO3 were weighed according to the stoichiometric ratio, and then mixed with agate balls and ultrapure water in proportion. The mixture was then ball-milled in a planetary ball mill jar for 12 hours.

[0064] Steps 2-8) are the same as in Example 1.

[0065] Figure 5 This indicates the effect of different values ​​of z on the phase composition when x = 8 and y = 0.2. Figure 6The curves show the relationship between the dielectric constant and dielectric loss of PbNb2O6-based ceramics at different frequencies and temperature when x = 8, y = 0.2, and z = 0.8.

[0066] Example 5

[0067] This embodiment provides a method for preparing PbNb2O6-based piezoelectric ceramic materials, specifically referring to Embodiment 1, including the following steps:

[0068] 1) First ball milling: Based on the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+8mol%Nb2O5+0.2wt%Sc2O3+0.8wt%SrCO3+δmol%Ta2O5, PbO, Nb2O5, Sc2O3, SrCO3, and Ta2O5 were weighed according to the stoichiometric ratio, and then mixed with agate balls and ultrapure water in proportion. The mixture was then ball-milled in a planetary ball mill jar for 12 hours.

[0069] Steps 2-8) are the same as in Example 1.

[0070] Scanning electron microscopy (SEM) surface image of the PbNb2O6-based piezoelectric ceramic in Example 5 after sintering is shown below. Figure 7 As shown, x takes the value of 8, y takes the value of 0.2, z takes the value of 0.8, and δ takes the value of 3.

[0071] Scanning electron microscopy (SEM) cross-sectional image of the PbNb2O6-based piezoelectric ceramic in Example 5 after sintering is shown below. Figure 8 As shown, x takes the value of 8, y takes the value of 0.2, z takes the value of 0.8, and δ takes the value of 3.

[0072] The dielectric constant and dielectric loss of the PbNb2O6-based ceramic in Example 5 are shown in the following curves as a function of temperature. Figure 9 As shown, x takes the value of 8, y takes the value of 0.2, z takes the value of 0.8, and δ takes the value of 3.

[0073] Performance data for Examples 1-5 are as follows Figure 10 As shown, in Example 2, x is 8; in Example 3, x is 8 and y is 0.2; in Example 4, x is 8, y is 0.2 and z is 0.8; in Example 5, x is 8, y is 0.2, z is 0.8 and δ is 3.

[0074] The appearance of the PbNb2O6-based piezoelectric ceramic sintered samples in Examples 2-5 is as follows: Figure 11As shown, in Example 2, x is 8; in Example 3, x is 8 and y is 0.2; in Example 4, x is 8, y is 0.2 and z is 0.8; in Example 5, x is 8, y is 0.2, z is 0.8 and δ is 3.

[0075] X-ray powder diffraction patterns of PbNb2O6-based piezoelectric ceramics sintered in Examples 1-5 are as follows: Figure 12 As shown, in Example 2, x is 8; in Example 3, x is 8 and y is 0.2; in Example 4, x is 8, y is 0.2 and z is 0.8; in Example 5, x is 8, y is 0.2, z is 0.8 and δ is 3.

[0076] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A doped and modified lead metaniobate-based high-temperature piezoelectric ceramic, characterized in that, The general formula of the piezoelectric ceramic is PbNb2O6+x mol%Nb2O5+y wt%Sc2O3+z wt%SrCO3+δ mol%Ta2O5; In the formula, 4≤x≤8, 0.1≤y≤0.6, 0.1≤z≤0.8, and 2≤δ≤5.

2. A method for preparing the doped and modified lead niobate-based high-temperature piezoelectric ceramic according to claim 1, characterized in that, Includes the following steps: (1) Weigh the raw materials PbO, Nb2O5, Sc2O3, SrCO3 and Ta2O5 according to the chemical composition ratio, add water and ball mill for the first time; (2) The material after the first ball milling is dried and then pre-calcined; (3) Add binder, dispersant and defoamer to the pre-calcined material and ball mill it a second time; (4) Spray granulation of the material after the second ball milling, press into blocks; then proceed with cold isostatic pressing, debinding, sintering, silvering and polarization to obtain PbNb2O6-based piezoelectric ceramic material.

3. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (1), the first ball milling time is 12-14 h.

4. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (2), the pre-firing temperature is 700-900 ℃ and the time is 2-4 h.

5. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (3), the mass ratio of the pre-fired material to the binder, dispersant and defoamer is 1:(0.005-0.015):(0.005-0.015):(0.005-0.015).

6. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (4), the pressure of the cold isostatic pressing is 200-250 MPa, and the holding time is 120-200 s.

7. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (4), the temperature of the glue discharge is 450-600 ℃, and the temperature is maintained for 2-4 h.

8. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (4), the sintering temperature is 1100-1300 ℃, and the holding time is 2-4 h.

9. The method for preparing doped and modified lead niobate-based high-temperature piezoelectric ceramics according to claim 2, characterized in that, In step (4), the polarization step is to apply a DC electric field of 3.0-4.0 Kv / mm to the silicone oil for polarization.

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