A PMN-PT-based piezoelectric material with a large coercive field and a preparation method thereof

Abstract

This invention relates to a PMN-PT-based piezoelectric material with a large coercive field and its preparation method. Unlike traditional PMN-PT ceramics where the Mg / Nb ratio is 1:2, this design deviates from the 1:2 integral ratio of Mg / Nb. The general elemental composition of this ceramic material is: (Pb... 1‑x Ln x )[(Mg (1+z) / 3 Nb (2‑z) / 3 ) y Ti 1‑y ] 1‑x / 4 O3, where Ln is a rare earth element, 0≤x≤0.05, 0.65≤y≤0.80, 0

Description

Technical Field

[0001] This invention belongs to the field of functional ceramic materials technology, and relates to a PMN-PT-based piezoelectric material with a large coercive field and its preparation method. Background Technology

[0002] Piezoelectric materials can realize the interconversion of mechanical energy and electrical energy. They have many physical effects such as piezoelectric effect and inverse piezoelectric effect, and therefore have very important applications in many fields such as sensors, transducers and actuators.

[0003] PbMg 1 / 3 Nb 2 / 3 O3-PbTiO3 (PMN-PT) is a composite perovskite piezoelectric material. When the PT content is 28%–35%, the material is located in the quasi-isomorphic phase boundary region. PMN-PT at the quasi-isomorphic phase boundary exhibits excellent piezoelectric, pyroelectric, and electro-optic properties. For example, PMN-PT piezoelectric single crystals are the core material for next-generation ultrasound probes and have received widespread attention internationally.

[0004] For example, CN114804873A discloses a transparent electro-optic ceramic material with high electro-optic coefficient and high temperature stability, and its preparation method. The elemental composition of this ceramic material is: (Pb 1-x Ln x )[(Mg 1 / 3 Nb 2 / 3 ) y Ti 1-y ] 1-x / 4 O3, where Ln is a rare earth element, 0.01≤x≤0.05, 0.90≤y≤0.70; the rare earth doping content in this ceramic material is distributed in a gradient along the thickness direction of the ceramic material, and this electro-optic ceramic has a high electro-optic coefficient and high temperature stability.

[0005] Although PMN-PT-based piezoelectric materials possess high piezoelectric coefficients, their coercivity is very low. For PMN-PT-based single crystals, the coercivity is typically around 2–3 kV / cm; for PMN-PT-based ceramics, it is typically around 3–5 kV / cm. This low coercivity makes these materials prone to depolarization under strong electric fields, leading to performance degradation or even failure. To improve the coercivity of PMN-PT-based piezoelectric materials, researchers often use In or Sc doping to form PIN-PMN-PT or ternary systems. However, In₂O₃ and Sc₂O₃ are expensive, significantly increasing costs. Furthermore, preparing large-size ternary PMN-PT-based single crystals is more difficult than preparing binary single crystals, thus limiting the practical application of these materials.

[0006] For the reasons mentioned above, it is necessary to develop a simple and low-cost method to improve the coercive field of PMN-PT-based piezoelectric ceramics. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned defects by providing a PMN-PT-based piezoelectric material with a large coercive field and its preparation method. This invention studies PMN-PT-based piezoelectric materials as relaxor ferroelectrics with a composite perovskite structure. The ceramic contains a large number of nanodomains, which move very easily under the action of an electric field. Therefore, PMN-PT-based piezoelectric materials generally have a low coercive field. Based on this, this invention adopts a method of deviating the stoichiometric ratio of Mg / Nb from 1:2 when designing the composition, which can reduce the content of nanodomains in the ceramic and significantly improve the coercive field of the ceramic. This invention proposes a simple and low-cost composition design method to improve PMN-PT-based piezoelectric materials.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] The first objective of this invention is to provide a PMN-PT-based piezoelectric material with a large coercive field, wherein the elemental composition of the PMN-PT-based piezoelectric material is: (Pb 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 O3, where Ln is a rare earth element, 0≤x≤0.05, 0.65≤y≤0.80, 0 <z≤0.02。

[0010] Furthermore, the rare earth element (lanthanide element) represented by Ln is selected from one or more of lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm).

[0011] The second objective of this invention is to provide a method for preparing the above-mentioned PMN-PT-based piezoelectric material with a large coercive field. The preparation method includes the following steps: firstly, magnesium niobate is synthesized, then PMN-PT ceramic is synthesized by solid-state method, and finally the ceramic is sintered in air to obtain PMN-PT piezoelectric ceramic (PMN-PT-based piezoelectric material).

[0012] Furthermore, the preparation method includes the following steps:

[0013] a) According to Mg (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 The general formula involves accurately weighing MgO and Nb2O5, followed by ball milling, calcination, and a second ball milling process to obtain Mg. (1+z) / 3 Nb (2-z) / 3 O(4-z) / 2 Ceramic powder;

[0014] b) According to (Pb) 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 Accurately weigh PbO, TiO2, and Ln2O3 according to the general formula, and add them to the Mg prepared in step a). (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 PMN-PT ceramic powder is obtained by ball milling, calcination, and ball milling again in ceramic powder.

[0015] c) Add a binder to the PMN-PT ceramic powder obtained in step b), granulate, press into shape, and remove plastic to obtain a ceramic green body;

[0016] d) Place the ceramic blank obtained in step c) into a hot press furnace and sinter it in an air atmosphere to obtain a PMN-PT piezoelectric ceramic with a large coercive field, which is the PMN-PT-based piezoelectric material with a large coercive field.

[0017] Further, in step a), the ball milling uses deionized water or alcohol as the medium and the planetary ball milling lasts for 4 to 6 hours; in step a), the second ball milling uses deionized water or alcohol as the medium and the planetary ball milling lasts for 4 to 6 hours.

[0018] Furthermore, in step a), the calcination temperature is 900–1200°C.

[0019] Further, in step b), according to (Pb) 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 O3 general formula for accurate weighing of PbO, TiO2, Ln2O3 in stoichiometric ratio.

[0020] Furthermore, in step b), the calcination temperature is 800–1000°C.

[0021] Further, in step b), the ball milling uses deionized water or alcohol as the medium, and the planetary ball milling lasts for 4 to 6 hours; in step b), the second ball milling uses deionized water or alcohol as the medium, and the planetary ball milling lasts for 4 to 6 hours.

[0022] Furthermore, in step c), the pressing and molding process involves dry pressing into a circular sheet.

[0023] Further, in step c), the pressing is performed by dry pressing with a pressure of 200 MPa into a circular sheet with a diameter of 15 mm.

[0024] Furthermore, in step c), the adhesive used is a conventional PMN-PT preparation adhesive.

[0025] Furthermore, in step d), the sintering is carried out at 1150–1300°C for 2–4 hours.

[0026] Furthermore, the coercivity of the PMN-PT-based piezoelectric material with a large coercivity field is 9–12 kV / cm.

[0027] Furthermore, the obtained PMN-PT-based piezoelectric material can be used in applications requiring strong electric fields, showing broad application prospects.

[0028] Compared with the prior art, the present invention has the following characteristics:

[0029] 1) The PMN-PT-based piezoelectric material preparation method provided by this invention does not use expensive dopants such as In and Sc. It only changes the Mg / Nb ratio, deviating it from half of that of traditional PMN-PT materials. Using this method, the coercive field of PMN-PT ceramics increases significantly, from 3–5 kV / cm in conventional PMN-PT ceramics to 9–12 kV / cm. This is beneficial for the application of PMN-PT ceramics under strong fields and has broad application prospects. Furthermore, the preparation method of this invention has advantages such as simple operation, short cycle time, low cost, and ease of large-scale production.

[0030] 2) The PMN-PT-based piezoelectric material preparation method provided by the present invention has a significantly improved coercive field compared with PMN-PT ceramics prepared by traditional methods. Therefore, it is not easy to depolarize and is more suitable for use under strong electric fields. Attached Figure Description

[0031] Figure 1 The X-ray diffraction pattern of the PMN-PT-based piezoelectric material prepared in Example 1 is shown below.

[0032] Figure 2 Here is a scanning electron microscope (SEM) image of the fracture surface of the PMN-PT-based piezoelectric material prepared in Example 1;

[0033] Figure 3 The diagram shows the hysteresis loop of the PMN-PT-based piezoelectric material prepared in Example 1 and a comparison diagram with the PMN-PT-based piezoelectric material with a Mg / Nb content of 1:2 in the comparative example.

[0034] Figure 4 The images show the bidirectional electrostrain diagrams of the PMN-PT-based piezoelectric materials prepared in Examples 1-4. Detailed Implementation Modes

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the accompanying drawings and the following embodiments are only used to illustrate the present invention, rather than limiting the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0036] In the present technical solution, features such as preparation means, materials, structures or composition ratios that are not clearly stated are regarded as common technical features disclosed in the prior art.

[0037] The present technical solution relates to a composition design method for increasing the coercive field of Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT) based piezoelectric materials. Different from the traditional PMN-PT ceramics where Mg / Nb is 1:2, in this design, the Mg / Nb deviates from the stoichiometric ratio of 1:2. The general elemental composition of this ceramic material is: (Pb 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 [[ID=2s]]) y Ti 1-y 1-x / 4 O3, where Ln is a rare earth element, 0 ≤ x ≤ 0.05, 0.65 ≤ y ≤ 0.80, 0 < z ≤ 0.02. The preparation method of this material is as follows: First, synthesize magnesium niobate, then synthesize PMN-PT ceramics by the solid-phase method, and finally sinter the ceramics into porcelain in air. The PMN-PT piezoelectric ceramics prepared by this method have a significantly increased coercive field compared with the PMN-PT ceramics prepared by the traditional method, so they are not easily depolarized and are more suitable for use under strong electric fields.

[0038] In the following examples, the raw materials used are all commercially available. [[ID=३३]]

[0039] Example 1

[0040] This example provides a PMN-PT based piezoelectric material with a large coercive field. The elemental composition of the PMN-PT based piezoelectric material is: (Pb 0.98 La 0.02 )[(Mg 1.02 / 3 Nb 1.98 / 3 ) 0.70 Ti 0.30 0.995 O3, and its preparation method includes the following steps:

[0041] a) According to Mg 1.02 / 3 Nb 1.98 / 3 O​​1.99 MgO and Nb2O5 in stoichiometric ratio were accurately weighed using a general formula, and then planetary ball milled for 6 hours using deionized water as the medium. After calcination at 1100℃ for 4 hours, the MgNb2O6 ceramic powder was obtained by planetary ball milling for 6 hours again using deionized water as the medium.

[0042] b) According to (Pb) 0.98 La 0,02 )[(Mg 1.02 / 3 Nb 1.98 / 3 ) 0.70 Ti 0.30 ] 0,995 O3 general formula, accurately weigh PbO, TiO2, and La2O3 in stoichiometric ratios and add them to the Mg prepared in step a). 1.02 / 3 Nb 1.98 / 3 O 1.99 In the ceramic powder, deionized water was used as the medium for planetary ball milling for 6 hours, followed by calcination at 850℃. Then, deionized water was used again as the medium for planetary ball milling for 6 hours, followed by drying to obtain the desired ceramic powder.

[0043] c) Add 8% by weight of a 5% PVA solution as a binder to the ceramic powder obtained in step b), then granulate the mixture and dry press it into 15mm diameter discs under a pressure of 200MPa, and then remove the plastic from the discs.

[0044] d) By placing the ceramic in a high-temperature furnace and sintering it at 1260℃ for 2 hours in an air atmosphere, PMN-PT-based piezoelectric ceramics with a large coercive field can be obtained. Its main electrical properties are listed in Table 1 below.

[0045] Table 1 shows the main electrical properties of the PMN-PT-based piezoelectric ceramics in Example 1.

[0046]

[0047] Figure 1 This is the X-ray diffraction pattern of the PMN-PT-based piezoelectric material prepared in this embodiment. Figure 1 It is evident that the obtained PMN-PT is mainly composed of perovskite phase, but also contains trace amounts of pyrochlore phase.

[0048] Figure 2 This is a scanning electron microscope (SEM) image of the fracture surface of the PMN-PT-based piezoelectric material prepared in this embodiment. Figure 2 It is evident that the prepared ceramic material has high density, with a grain size between 2 and 5 μm.

[0049] Figure 3The hysteresis loop of the PMN-PT-based piezoelectric material (PMN-PT-N) prepared in this embodiment is shown, and compared with that of the comparative example PMN-PT-based piezoelectric material (PMN-PT-S) with a Mg / Nb molar ratio of 1 / 2. Figure 3 It can be seen that for PMN-PT-based piezoelectric materials with a Mg / Nb molar ratio of 1 / 2, the coercive field is only 4.9 kV / cm; while for PMN-PT-N with a Mg / Nb molar ratio deviating from 1 / 2, the coercive field is as high as 9.4 kV / cm. Figure 3 This also fully demonstrates the significant effect of this method on increasing the coercive field of PMN-PT materials.

[0050] Figure 4 The image shows the bidirectional electrostriction of the PMN-PT-based piezoelectric material prepared in Example 1. Figure 4 It can be seen that this ceramic has good piezoelectric properties, and its quasi-static d 33 It is 620pC / N.

[0051] Comparative Example

[0052] This comparative example provides a PMN-PT-based piezoelectric material (PMN-PT-S) with a Mg / Nb molar ratio of 1 / 2. The elemental composition of the PMN-PT-based piezoelectric material is: (Pb... 0.98 La 0.02 )[(Mg 1 / 3 Nb 2 / 3 ) 0.70 Ti 0.30 ] 0.995 O3 has a different elemental composition from the PMN-PT-based piezoelectric material in Example 1, and is prepared using the same method as in Example 1.

[0053] Example 2

[0054] This embodiment provides a PMN-PT-based piezoelectric material with a large coercive field. The elemental composition of the PMN-PT-based piezoelectric material is: (Pb 0.99 Nd 0.01 )[(Mg 1.01 / 3 Nb 1.99 / 3 ) 0.65 Ti 0.35 ] 0.9975 O3, the preparation method of which includes the following steps:

[0055] a) According to Mg 1.01 / 3 Nb 1.99 / 3 O 1.995 MgO and Nb2O5 in stoichiometric ratio were accurately weighed using a general formula, and then planetary ball milled for 6 hours using deionized water as the medium. After calcination at 1100℃ for 4 hours, the MgNb2O6 ceramic powder was obtained by planetary ball milling for 6 hours again using deionized water as the medium.

[0056] b) According to (Pb) 0.99 Nd 0,01 )[(Mg 1.01 / 3 Nb 1.99 / 3 ) 0.65 Ti 0.35 ] 0.9975 O3 general formula, accurately weigh PbO, TiO2, Nd2O3 in stoichiometric ratio and add to Mg obtained in step a). 1.01 / 3 Nb 1.99 / 3 O 1.995 In the ceramic powder, deionized water was used as the medium for planetary ball milling for 6 hours, followed by calcination at 850℃. Then, deionized water was used again as the medium for planetary ball milling for 6 hours, followed by drying to obtain the desired ceramic powder.

[0057] c) Add 8% by mass of a 5% PVA solution as a binder to the ceramic powder obtained in step b), then granulate the mixture and dry press it into 15mm diameter discs under a pressure of 200MPa, and then remove the plastic from the discs.

[0058] d) Place the ceramic in a high-temperature furnace and sinter it at 1260℃ for 2 hours in an air atmosphere to obtain PMN-PT-based piezoelectric ceramics with a large coercive field. The main electrical properties are listed in Table 2 below.

[0059] Table 2 shows the main electrical properties of the PMN-PT-based piezoelectric ceramics in Example 2.

[0060]

[0061] Example 3

[0062] This embodiment provides a PMN-PT-based piezoelectric material with a large coercive field. The elemental composition of the PMN-PT-based piezoelectric material is: (Pb 0.95 Nd 0.05 )[(Mg 1.005 / 3 Nb 1.995 / 3 ) 0.65 Ti 0.35 ] 0.9875 O3 has a different elemental composition from the PMN-PT-based piezoelectric material in Example 1, and is prepared using the same method as in Example 1.

[0063] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A PMN-PT-based piezoelectric material with a large coercive field, wherein the elemental composition of the PMN-PT-based piezoelectric material is: (Pb 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 O3, where Ln is a rare earth element, 0 < x ≤0.05, 0.65≤ y ≤0.80, 0< z ≤0.02; By using a stoichiometric ratio of Mg / Nb that deviates from 1:2, the content of nanodomains in ceramics is reduced, thereby improving the coercive field of the ceramics. The coercivity of the PMN-PT-based piezoelectric material with a large coercivity field is 9~12 kV / cm; The preparation method of the PMN-PT-based piezoelectric material with a large coercive field includes the following steps: a) According to Mg (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 The general formula involves accurately weighing MgO and Nb2O5, followed by ball milling, calcination, and a second ball milling process to obtain Mg. (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 Ceramic powder; b) According to (Pb) 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 Accurately weigh PbO, TiO2, and Ln2O3 according to the general formula, and add them to the Mg prepared in step a). (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 PMN-PT ceramic powder is obtained by ball milling, calcination, and ball milling again in ceramic powder. c) Add a binder to the PMN-PT ceramic powder obtained in step b), granulate, press into shape, remove plastic, and obtain a ceramic green body; d) Place the ceramic blank obtained in step c) into a hot press furnace and sinter it in air atmosphere to obtain a PMN-PT piezoelectric ceramic with a large coercive field, which is the PMN-PT-based piezoelectric material with a large coercive field.

2. The PMN-PT-based piezoelectric material with a large coercive field according to claim 1, characterized in that, The rare earth element represented by Ln is selected from one or more of lanthanum, praseodymium, neodymium, and samarium.

3. A method for preparing a PMN-PT-based piezoelectric material with a large coercive field as described in any one of claims 1 or 2, characterized in that, Includes the following steps: a) According to Mg (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 The general formula involves accurately weighing MgO and Nb2O5, followed by ball milling, calcination, and a second ball milling process to obtain Mg. (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 Ceramic powder; b) According to (Pb) 1-x Ln x )[(Mg (1+z) / 3 Nb (2-z) / 3 ) y Ti 1-y ] 1-x / 4 Accurately weigh PbO, TiO2, and Ln2O3 according to the general formula, and add them to the Mg prepared in step a). (1+z) / 3 Nb (2-z) / 3 O (4-z) / 2 PMN-PT ceramic powder is obtained by ball milling, calcination, and ball milling again in ceramic powder. c) Add a binder to the PMN-PT ceramic powder obtained in step b), granulate, press into shape, remove plastic, and obtain a ceramic green body; d) Place the ceramic blank obtained in step c) into a hot press furnace and sinter it in air atmosphere to obtain a PMN-PT piezoelectric ceramic with a large coercive field, which is the PMN-PT-based piezoelectric material with a large coercive field.

4. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step a), the ball milling uses deionized water or alcohol as the medium and the planetary ball milling is performed for 4-6 hours. In step a), the re-milling uses deionized water or alcohol as the medium and is performed for 4-6 hours.

5. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step a), the calcination temperature is 900~1200 ℃.

6. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step b), the calcination temperature is 800~1000 ℃.

7. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step b), the ball milling uses deionized water or alcohol as the medium and performs planetary ball milling for 4-6 hours; In step b), the re-milling uses deionized water or alcohol as the medium and is performed for 4-6 hours using planetary ball milling.

8. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step c), the pressing is performed by dry pressing with a pressure of 200 MPa into a disc with a diameter of 15 mm.

9. The method for preparing a PMN-PT-based piezoelectric material with a large coercive field according to claim 3, characterized in that, In step d), the sintering is carried out at 1150~1300 °C for 2~4 h.

Images