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

Abstract

The invention discloses doped and modified lead metaniobate-based high-temperature piezoelectric ceramic and a preparation method thereof. The invention relates to doped and modified lead metaniobate-based high-temperature piezoelectric ceramic. The general formula of the piezoelectric ceramic is PbNb2O6 + x mol% Nb2O5 + y wt% Sc2O3 + z wt% SrCO3 + delta mol% Ta2O5, in the formula, x is equal to 0-8, y is equal to 0-0.8, z is equal to 0-1, and delta is equal to 0-12. The problems that pure PbNb2O6 is difficult to sinter, low in density, low in piezoelectric coefficient and the like are solved by adding excessive Nb2O5; on the basis, Sc < 3 + >, Sr < 2 + > and Ta < 5 + > ions are doped in sequence, so that the piezoelectric property of the PbNb2O6-based piezoelectric ceramic is continuously improved while the high Curie temperature is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of piezoelectric ceramics, and in particular to a doped and modified lead metaniobate-based high-temperature piezoelectric ceramic and a preparation method thereof. Background Art

[0002] Lead niobate (PbNb2O6) has a high Curie temperature and a low mechanical quality factor, so it has great application prospects 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-phase sintering methods. The preparation of ferroelectric orthorhombic lead niobate is a great challenge because there is a rhombohedral to tetragonal phase transition during the traditional sintering process. This phase transition will cause abnormal grain growth of lead niobate during the ceramic formation process, accompanied by the generation of cracks and pores. Due to these defects and some other reasons, the piezoelectric properties of lead niobate are not good enough and the density is not high enough, which affects its application in high-temperature fields.

[0003] The above problems can be improved by doping and modifying PbNb2O6-based ceramics. There are three types of voids in lead niobate, namely A, B and C. Void A is divided into four-sided voids A1 and five-sided voids A2; Void B can be divided into two types of voids B1 and B2 due to the different surrounding environments caused by the degree of inclination of the oxygen octahedron; finally, there is a triangular void C. Studies have shown that the causes of piezoelectric properties are mainly divided into two parts: the contribution of domains and the contribution of spontaneous polarization. Spontaneous polarization is usually caused by the distortion of oxygen octahedrons, and there are many factors that affect the torsion of oxygen octahedrons in tungsten bronze systems, which indicates that the performance of lead niobate can be improved by element doping. Chemical doping is an effective method to improve the torsion of oxygen octahedrons. The doping modification of lead niobate mainly involves doping of A and B positions in the lattice. For the co-doping of A and B positions, Wu et al. adopted a two-step sintering process, using Sr 2+ 、 5+ Replace some of the Pb at the A position 2+ Nb with B 5+ , so that the grains are refined, the piezoelectric performance reaches 79pC / N, and the Curie temperature is slightly reduced. In addition, Venet et al. doped La in PbNb2O6 3+ , making PbNb2O6-based ceramics have a stable orthorhombic phase, but its Curie temperature drops sharply to about 270°C. Fang et al. increased the density of PbNb2O6-based ceramics by adding an appropriate amount of CuO and obtained a piezoelectric performance of 190pC / N, but the Curie temperature dropped to 395°C.

[0004] Although the previous methods of adding other components and changing the process can improve the density and piezoelectric properties of PbNb2O6-based piezoelectric ceramics, they often reduce the Curie temperature of the ceramics. In addition, in order to obtain a stable ferroelectric orthorhombic phase, the sample needs to be quenched after sintering. There are not many reports on the comprehensive improvement of the density of PbNb2O6-based ceramics by multi-element doping (simultaneous substitution of A / B positions), the improvement of sintering performance, and the improvement of piezoelectric properties and Curie temperature. Summary of the invention

[0005] In order to solve the problems of difficult sintering, low density and poor piezoelectric performance of lead metaniobate-based ceramics, the present invention provides a PbNb2O6+x mol%Nb2O5+y wt%Sc2O3+z wt%SrCO3+δmol%Ta2O5 doping system, and uses a traditional solid phase sintering method to prepare a PbNb2O6-based ceramic with high piezoelectric coefficient, high Curie temperature and high density through multi-element doping modification. Finally, a high strength, high piezoelectric coefficient (d 33 ) is 80pC / N, Curie temperature (T c ) is a high temperature piezoelectric ceramic of 636℃.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

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

[0008] Wherein, x=0-8, y=0-0.8, z=0-1, δ=0-12.

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

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

[0011] (1) weighing the raw materials PbO, Nb2O5, Sc2O3, SrCO3, and Ta2O5 according to the chemical composition ratio and adding water for the first ball milling;

[0012] (2) Drying the material after the first ball milling and then pre-calcining;

[0013] (3) adding a binder, a dispersant, and a defoamer to the pre-burned material for a second ball milling;

[0014] (4) The material after the second ball milling is spray granulated and pressed into blocks; then cold isostatic pressing, binder removal, sintering, silver coating and polarization are carried out in sequence to obtain PbNb2O6-based piezoelectric ceramic materials.

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

[0016] Preferably, in step (2), the pre-burning temperature is 700-900° C. and the time is 2-4 hours.

[0017] Preferably, in step (3), the mass ratio of the pre-burned material to the binder, dispersant, and defoamer is 1: (0.005-0.015): (0.005-0.015): (0.005-0.015). The present invention does not limit the specific binder, dispersant, and defoamer, and any conventionally used reagents can be used.

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

[0019] Preferably, in step (4), the debinding temperature is 450-600° C. and the temperature is kept for 2-4 hours.

[0020] Preferably, in step (4), the sintering temperature is 1100-1300° C. and the temperature is kept for 2-4 hours.

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

[0022] The high-temperature piezoelectric ceramics prepared by the solid phase synthesis method of the present invention have high density, high strength, good sintering performance and piezoelectric properties, and can be used in high-temperature sensors. The PbNb2O6-based high-temperature piezoelectric ceramics of the present invention belong to tungsten bronze non-filled structural materials. According to the different proportions of the raw materials, the sintered ceramics have a Curie temperature between 450-700°C and a piezoelectric coefficient d 33 The PbNb2O6-based high-temperature piezoelectric ceramic has good density, high strength, and good high-temperature stability. The X-ray powder diffraction of the prepared PbNb2O6-based high-temperature piezoelectric ceramic PbNb2O6+8mol%Nb2O5+0.2wt%Sc2O3+0.8wt%SrCO3+3mol%Ta2O5 shows that the ceramic has a tungsten bronze structure at room temperature and is a ferroelectric orthorhombic phase. The piezoelectric constant is 80Pc / N. At a frequency of 10KHz, the dielectric constant at room temperature reaches 321, and the coercive field strength E c is 23.83Kv / cm, and the residual polarization P r 3.96uc / cm2 The high-temperature piezoelectric ceramics prepared by PbNb2O6+8mol%Nb2O5+0.2wt%Sc2O3+0.8wt%SrCO3+3mol%Ta2O5 have good high-temperature stability, and the Curie temperature reaches 636℃.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention adopts the traditional solid phase sintering method to prepare PbNb2O6 based piezoelectric ceramics. Firstly, excessive Nb2O5 is added to solve the problems of sintering difficulty, low density and low piezoelectric coefficient of pure PbNb2O6. On the basis of the above, Sc is doped in sequence. 3+ , Sr 2+ 、 5+ ions, while ensuring a high Curie temperature, continue to improve the piezoelectric properties of PbNb2O6-based piezoelectric ceramics. The oxides of these elements are selected because their ionic radius is similar to the A / B occupier ion radius in the PbNb2O6-based ceramic lattice, and can be better incorporated and substituted. Multi-element doping makes the piezoelectric coefficient (d 33 ) increased from the initial 46pC / N to 80pC / N, and the Curie temperature (T c ) increased by nearly 12% (568°C to 636°C), and the volume density increased from 5.69g / cm 3 Increased to 6.30g / cm 3 (close to 96% of the theoretical density), the appropriate amount of doping can avoid the formation of non-ferroelectric rhombohedral phase in PbNb2O6-based ceramics, thereby stabilizing the ferroelectric orthorhombic phase and allowing conventional furnace cooling after sintering of the ceramics. The above results can promote the role of PbNb2O6-based piezoelectric ceramics in the field of high-temperature piezoelectricity and provide a method for comprehensively improving sintering performance, improving piezoelectric properties and high-temperature stability. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0028] Figure 4 The high temperature dielectric thermogram of the PbNb2O6-based ceramic when x=8, y=0.2 in Example 3;

[0029] Figure 5 X-ray diffraction patterns of the 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 thermogram of the PbNb2O6-based ceramic when x=8, y=0.2, z=0.8 in Example 4;

[0031] Figure 7 The scanning electron microscope (SEM) sintered surface image of the PbNb2O6-based piezoelectric ceramic in Example 5 when x=8, y=0.2, z=0.8, δ=3;

[0032] Figure 8 The scanning electron microscope (SEM) sintered cross-sectional image of the PbNb2O6-based piezoelectric ceramic in Example 5 when x=8, y=0.2, z=0.8, δ=3;

[0033] Fig. 9 The high temperature dielectric thermogram of the PbNb2O6-based ceramic when x=8, y=0.2, z=0.8, δ=3 in Example 5;

[0034] Fig.10 are the performance parameters of the PbNb2O6-based piezoelectric ceramics of Examples 1-5;

[0035] Fig.11 The appearance of the sintered sample of the PbNb2O6-based piezoelectric ceramic of Example 2-5;

[0036] Fig.12 1 is the X-ray diffraction pattern of the PbNb2O6-based piezoelectric ceramics of Examples 1-5. DETAILED DESCRIPTION

[0037] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0039] Example 1

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

[0041] 1) First ball milling: According to the composition formula of PbNb2O6-based piezoelectric ceramic material, PbO and Nb2O5 are used as raw materials. After weighing according to the stoichiometric ratio, agate balls and ultrapure water are mixed with the raw materials in proportion (agate balls: raw materials: ultrapure water = 2:1:1.5), and ball milled in a planetary ball mill for 12 hours;

[0042] 2) Drying: Dry the slurry after the first ball milling, put it into the furnace for pre-sintering synthesis, the pre-sintering temperature is 800℃, and keep it warm for 2.5h;

[0043] 3) Secondary ball milling: the raw material after pre-sintering is powdered and passed through a 180-mesh sieve, and then subjected to secondary ball milling for 12 hours, while adding 1wt% of a binder, 1wt% of a dispersant, and 1wt% of a defoamer accounting for 1wt% of the solid raw material powder mass;

[0044] 4) Spray granulation: spray granulate the slurry after secondary ball milling, and then press the powder into blocks at a pressure of 10 MPa;

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

[0046] 6) Debinding and sintering: The sample is debinded and sintered, the debinding temperature is 550°C (keeping temperature for 3 hours), and the sintering temperature is 1260°C (keeping temperature for 3 hours), and finally the sample blank is obtained;

[0047] 7) Silvering: Slice, polish and clean the ceramic blank and then silver-sinter at 700℃;

[0048] 8) Polarization: In 150°C silicone oil, a 4Kv / mm DC electric field was applied for polarization to obtain a PbNb2O6-based piezoelectric ceramic material.

[0049] Example 2

[0050] This embodiment provides a method for preparing a PbNb2O6-based piezoelectric ceramic material, which specifically refers to Embodiment 1 and includes the following steps:

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

[0052] Steps 2-8 are the same as those in Example 1 to obtain a PbNb2O6-based piezoelectric ceramic material.

[0053] The ceramic properties with different values ​​of x were tested, and the results are shown in Table 1 and Attached Figure 1-2 Table 1 shows the influence of different values ​​of x on the properties of PbNb2O6-based piezoelectric ceramics; Figure 1 It shows the influence of different values ​​of x on the ceramic phase; Figure 2 It represents the relationship curve of the dielectric constant and dielectric loss of PbNb2O6-based ceramics at different frequencies with temperature when x=8.

[0054] Table 1

[0055]

[0056] Example 3

[0057] This embodiment provides a method for preparing a PbNb2O6-based piezoelectric ceramic material, which specifically refers to Embodiment 1 and includes the following steps:

[0058] 1) First ball milling: According to the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+8mol%Nb2O5+ywt%Sc2O3, PbO, Nb2O5, and Sc2O3 are used as raw materials. After weighing them according to the stoichiometric ratio, agate balls and ultrapure water are mixed with the raw materials in proportion, and ball milled in a planetary ball mill for 12 hours;

[0059] Step 2-8) is the same as in Example 1 to obtain a PbNb2O6-based piezoelectric ceramic material.

[0060] Figure 3 It shows the influence of different values ​​of y on the physical 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 a PbNb2O6-based piezoelectric ceramic material, which specifically refers to Embodiment 1 and includes the following steps:

[0063] 1) First ball milling: According to the composition formula of PbNb2O6-based piezoelectric ceramic material, PbNb2O6+8mol%Nb2O5+0.2wt%Sc2O3+zwt%SrCO3, PbO, Nb2O5, Sc2O3, and SrCO3 are used as raw materials. After weighing them according to the stoichiometric ratio, agate balls and ultrapure water are mixed with the raw materials in proportion, and ball milled in a planetary ball mill for 12 hours;

[0064] Step 2-8) is the same as in Example 1.

[0065] Figure 5 It shows the influence of different values ​​of z on the physical phase when x=8 and y=0.2; Figure 6The graph shows 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 a PbNb2O6-based piezoelectric ceramic material, which specifically refers to Embodiment 1 and includes the following steps:

[0068] 1) First ball milling: According to 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 are used as raw materials, weighed according to the stoichiometric ratio, mixed with the raw materials in proportion with agate balls and ultrapure water, and ball milled in a planetary ball mill for 12 hours;

[0069] Step 2-8) is the same as in Example 1.

[0070] The scanning electron microscope (SEM) sintered surface image of the PbNb2O6-based piezoelectric ceramic of Example 5 is as follows: Figure 7 As shown, where x is 8, y is 0.2, z is 0.8, and δ is 3.

[0071] The scanning electron microscope (SEM) sintered cross-section image of the PbNb2O6-based piezoelectric ceramic of Example 5 is as follows: Figure 8 As shown, where x is 8, y is 0.2, z is 0.8, and δ is 3.

[0072] The relationship curve between the dielectric constant and dielectric loss of the PbNb2O6-based ceramic of Example 5 and the temperature is as follows: Fig. 9 As shown, where x is 8, y is 0.2, z is 0.8, and δ is 3.

[0073] The performance data of Examples 1-5 are as follows Fig.10 As shown, in Example 2, the value of x is 8; in Example 3, the value of x is 8, the value of y is 0.2; in Example 4, the value of x is 8, the value of y is 0.2, and the value of z is 0.8; in Example 5, the value of x is 8, the value of y is 0.2, the value of z is 0.8, and the value of δ is 3.

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

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

[0076] The embodiments of the present invention are 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 of these embodiments are made without departing from the principles and spirit of the present invention, and 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+δmol%Ta2O5; Wherein, x=0-8, y=0-0.8, z=0-1, δ=0-12.

2. The doped and modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 1, characterized in that: In the general formula, 4≤x≤8, 0.1≤y≤0.6, 0.1≤z≤0.8, and 2≤δ≤5.

3. A method for preparing the doped modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 1 or 2, characterized in that: The following steps are involved: (1) weighing the raw materials PbO, Nb2O5, Sc2O3, SrCO3, and Ta2O5 according to the chemical composition ratio and adding water for the first ball milling; (2) Drying the material after the first ball milling and then pre-calcining; (3) adding a binder, a dispersant, and a defoamer to the pre-burned material for a second ball milling; (4) The material after the second ball milling is spray granulated and pressed into blocks; then cold isostatic pressing, binder removal, sintering, silver coating and polarization are carried out in sequence to obtain PbNb2O6-based piezoelectric ceramic materials.

4. The method for preparing the doped modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (1), the first ball milling time is 12-14 hours.

5. The method for preparing the doped modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (2), the pre-burning temperature is 700-900° C. and the time is 2-4 hours.

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

7. The method for preparing the doped and modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (4), the cold isostatic pressing pressure is 200-250 MPa, and the holding time is 120-200 s.

8. The method for preparing the doped and modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (4), the debinding temperature is 450-600° C. and the temperature is kept for 2-4 hours.

9. The method for preparing the doped and modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (4), the sintering temperature is 1100-1300° C. and the temperature is kept for 2-4 hours.

10. The method for preparing the doped modified lead metaniobate-based high-temperature piezoelectric ceramic according to claim 3, characterized in that: In step (4), the polarization step is: applying 3.0-4.0Kv / mm DC electric field polarization in silicone oil.

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