阅读说明：本技术 一种压电薄膜及其制备方法 (Piezoelectric film and preparation method thereof ) 是由 王英辉 王盛凯 于 2020-12-16 设计创作，主要内容包括：本申请公开了一种压电薄膜及其制备方法,该方法包括制备溶解有压电材料粉体的溶液；将溶液流延至基板的表面,以在表面上形成液膜；将带有液膜的基板置于高压电场环境中进行极化,待液膜中的溶剂蒸发完毕,得到压电薄膜。本申请的方法利用溶解有压电材料的溶液在基板的表面形成液膜,然后将带有液膜的基板置于高压环境中,蒸发结晶的同时对液膜进行高压极化,可以使液膜中的压电材料分子结晶度、晶相转变有较大的提升,从而增加压电薄膜压电系数；高压极化是在制备压电薄膜的过程中,有效降低压电薄膜被高压击穿的风险；并且,采用流延的方式形成液膜,避免薄膜在拉伸过程中内部产生缺陷,提升压电薄膜品质,同时降低对设备的要求,简化制作工艺。(The application discloses a piezoelectric film and a preparation method thereof, wherein the method comprises the steps of preparing a solution in which piezoelectric material powder is dissolved; casting the solution onto a surface of a substrate to form a liquid film on the surface; and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated. The method forms a liquid film on the surface of the substrate by using a solution dissolved with a piezoelectric material, then places the substrate with the liquid film in a high-pressure environment, evaporates and crystallizes, and simultaneously carries out high-pressure polarization on the liquid film, so that the molecular crystallinity and the crystal phase transformation of the piezoelectric material in the liquid film are greatly improved, and the piezoelectric coefficient of the piezoelectric film is increased; the high-voltage polarization effectively reduces the risk of high-voltage breakdown of the piezoelectric film in the process of preparing the piezoelectric film; and moreover, a liquid film is formed by adopting a tape casting mode, so that the defect of the film generated in the stretching process is avoided, the quality of the piezoelectric film is improved, the requirement on equipment is reduced, and the manufacturing process is simplified.)

1. A method for preparing a piezoelectric film, comprising:

preparing a solution in which piezoelectric material powder is dissolved;

casting the solution onto a surface of a substrate to form a liquid film on the surface;

and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated.

2. The method of preparing a piezoelectric thin film according to claim 1, further comprising, before said casting the solution onto the surface of the substrate:

removing bubbles from the solution.

3. The method of manufacturing a piezoelectric thin film according to claim 2, wherein the removing bubbles in the solution includes:

carrying out ultrasonic treatment on the solution to remove bubbles in the solution;

and placing the solution after ultrasonic treatment in a vacuum environment, and removing bubbles in the solution again.

4. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the preparing of the solution in which the piezoelectric material powder is dissolved includes:

dissolving the piezoelectric material powder in a solvent to obtain a prefabricated solution;

and stirring the prefabricated solution and adding the piezoelectric material powder into the prefabricated solution to obtain the solution.

5. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the piezoelectric material powder is any one of:

polyvinylidene fluoride, trifluoroethylene, polyvinylidene fluoride doped with a dielectric material, trifluoroethylene doped with a dielectric material.

6. The method for manufacturing a piezoelectric thin film according to claim 5, wherein the dielectric material is any one of:

barium titanate, silica, lead zirconate titanate.

7. The method for manufacturing a piezoelectric thin film according to claim 1, wherein the substrate is any one of:

organic glass, ordinary glass, sapphire.

8. The method for preparing a piezoelectric thin film according to claim 1, wherein the solvent is any one or any combination of the following:

n-methyl pyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

9. The method of manufacturing a piezoelectric thin film according to any one of claims 1 to 8, wherein the surface of the substrate has a roughness of less than 1.0 μm.

10. A piezoelectric thin film produced by the method for producing a piezoelectric thin film according to any one of claims 1 to 9.

Technical Field

The application relates to the technical field of flexible sensing, in particular to a piezoelectric film and a preparation method thereof.

Background

Polyvinylidene fluoride (PVDF) is a semi-crystalline polymer in normal state, has the characteristics of high flexibility, low density and low impedance, and has been reported to have 5 crystal forms such as α, β, γ, δ and e, which are formed under different conditions and can be mutually converted under certain conditions (action of heat, electric field, mechanical and radiation energy). Among them, the beta crystal form is the most important, and the beta crystal form is easily polarized due to the fact that the unit cells contain trans-molecular chains with strong polarity, generates a piezoelectric effect and is applied to the aspects of piezoelectricity and pyroelectricity.

Taking PVDF piezoelectric film as an example, the process flow of preparing the flexible piezoelectric film is roughly: firstly, performing crystallization molding treatment on PVDF powder by adopting methods such as hot pressing/tape casting/extrusion to form a PVDF film, wherein the content of an alpha phase in the PVDF film is high, then performing uniaxial normal-temperature stretching, extrusion and the like on the PVDF film to convert partial crystals in the PVDF film into a beta phase to obtain the PVDF piezoelectric film, and performing high-pressure polarization treatment after obtaining the PVDF piezoelectric film to improve the content of the beta phase. The method has the following three problems that firstly, the PVDF piezoelectric film is already manufactured, the promotion of the content of beta phase and the molecular crystallinity is limited when polarization is carried out, so that the piezoelectric coefficient of the piezoelectric film is smaller, secondly, the PVDF piezoelectric film has the risk of being broken down by a high-voltage electric field during polarization, thirdly, when a stretching mode is adopted, structural defects are easily generated in the PVDF film, the requirement on equipment is higher, the pull-up ratio needs to be strictly controlled, the manufactured PVDF film is thinner, and the molecular orientation is usually disordered.

Therefore, how to solve the above technical problems should be a great concern to those skilled in the art.

Disclosure of Invention

The piezoelectric film and the preparation method thereof are provided to improve the piezoelectric coefficient of the piezoelectric film, reduce the risk of breakdown of the piezoelectric film, reduce the requirements on equipment and simplify the manufacturing process.

In order to solve the above technical problem, the present application provides a method for preparing a piezoelectric thin film, including:

preparing a solution in which piezoelectric material powder is dissolved;

casting the solution onto a surface of a substrate to form a liquid film on the surface;

and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated.

Optionally, before the casting the solution onto the surface of the substrate, further comprising:

removing bubbles from the solution.

Optionally, the removing bubbles in the solution includes:

carrying out ultrasonic treatment on the solution to remove bubbles in the solution;

and placing the solution after ultrasonic treatment in a vacuum environment, and removing bubbles in the solution again.

Optionally, the preparing the solution in which the piezoelectric material powder is dissolved includes:

dissolving the piezoelectric material powder in a solvent to obtain a prefabricated solution;

and stirring the prefabricated solution and adding the piezoelectric material powder into the prefabricated solution to obtain the solution.

Optionally, the piezoelectric material powder is any one of the following:

polyvinylidene fluoride, trifluoroethylene, polyvinylidene fluoride doped with a dielectric material, trifluoroethylene doped with a dielectric material.

Optionally, the dielectric material is any one of the following:

barium titanate, silica, lead zirconate titanate.

Optionally, the substrate is any one of the following:

organic glass, ordinary glass, sapphire.

Optionally, the solvent is any one or any combination of the following:

n-methyl pyrrolidone, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

Optionally, the roughness of the surface of the substrate is less than 1.0 micron.

The present application also provides a piezoelectric film produced by the method for producing a piezoelectric film according to any one of the above-mentioned persons.

The application provides a piezoelectric film preparation method, which comprises the following steps: preparing a solution in which piezoelectric material powder is dissolved; casting the solution onto a surface of a substrate to form a liquid film on the surface; and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated.

Therefore, the piezoelectric film preparation method of the application forms a liquid film on the surface of the substrate by using a solution in which the piezoelectric material is dissolved, then places the substrate with the liquid film in a high-pressure environment, evaporates and crystallizes, and simultaneously carries out high-pressure polarization on the liquid film, so that the molecular crystallinity and the crystal phase transformation of the piezoelectric material in the liquid film are greatly improved, and the piezoelectric coefficient of the piezoelectric film is increased; the high-voltage polarization in the application effectively reduces the risk of high-voltage breakdown of the piezoelectric film in the process of preparing the piezoelectric film; and, adopt the mode of curtain coating to form the liquid film in this application, avoid the film to produce the defect in tensile in-process is inside, promote piezoelectric film quality, reduce the requirement to equipment simultaneously, simplify the preparation technology.

In addition, the application also provides a piezoelectric film with the advantages.

Drawings

For a clearer explanation of the embodiments or technical solutions of the prior art of the present application, the drawings needed for the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a flowchart of a method for manufacturing a piezoelectric thin film according to an embodiment of the present disclosure;

fig. 2 is a flowchart of another piezoelectric film manufacturing method according to an embodiment of the present disclosure.

Detailed Description

In order that those skilled in the art will better understand the disclosure, the following detailed description will be given with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.

As described in the background section, in the prior art, when a PVDF flexible piezoelectric film is prepared, after the PVDF film is obtained, uniaxial normal-temperature stretching, extrusion and the like are performed to convert part of crystals in the PVDF film into a β phase, so as to obtain the PVDF piezoelectric film, and then the PVDF piezoelectric film is subjected to high-voltage polarization treatment, so that the piezoelectric coefficient of the prepared piezoelectric film is small, and the PVDF piezoelectric film has a risk of being broken down by a high-voltage electric field during polarization.

In view of the above, the present application provides a method for manufacturing a piezoelectric thin film, please refer to fig. 1, where fig. 1 is a flowchart of a method for manufacturing a piezoelectric thin film according to an embodiment of the present application, the method including:

step S101: preparing a solution in which the piezoelectric material powder is dissolved.

It should be noted that, in the present application, whether or not the solution is in a saturated state is not particularly limited, as the case may be.

As a specific embodiment, the preparing a solution in which a piezoelectric material powder is dissolved includes:

step S1011: and dissolving the piezoelectric material powder in a solvent to obtain a prefabricated solution.

The piezoelectric material powder includes, but is not limited to, any of the following:

polyvinylidene fluoride, trifluoroethylene (TRFE for short), polyvinylidene fluoride doped with a dielectric material, and trifluoroethylene doped with a dielectric material. Wherein the dielectric material includes, but is not limited to, any one of barium titanate, silicon dioxide, lead zirconate titanate.

It should also be noted that the solvent includes, but is not limited to, any one or any combination of the following:

n-methylpyrrolidone (NMP), Dimethylformamide (DMF), Dimethylacetamide (DMAC), and Dimethylsulfoxide (DMSO).

Step S1012: and stirring the prefabricated solution and adding the piezoelectric material powder into the prefabricated solution to obtain the solution.

Due to the fact that the viscosity of the solvent is high, the stirring time is preferably 4-12 h, and therefore the piezoelectric material powder is completely dissolved in the solvent.

As another specific embodiment, the piezoelectric material powder is directly dissolved in a solvent and stirred to obtain a desired solution.

Preferably, the particle size of the piezoelectric material powder is between 1nm and 1 μm, inclusive, for example, 8nm, 20nm, 100nm, 500nm, 700nm, 850nm, 900nm, etc., so as to accelerate the dissolution rate of the piezoelectric material powder in the solvent, accelerate the piezoelectric film preparation efficiency,

step S102: casting the solution onto a surface of a substrate to form a liquid film on the surface.

The solution is cast to the surface of the substrate in a casting mode, so that defects generated inside the piezoelectric film in the stretching process can be avoided, and the quality of the piezoelectric film is reduced.

Preferably, the flow of the solution is uniformly spread to the surface of the substrate to obtain a piezoelectric thin film having a uniform thickness.

It should be noted that the type of the substrate is not particularly limited in this application and may be selected. For example, the substrate may be organic glass, ordinary glass, sapphire, quartz glass, or the like, wherein the organic glass (PMMA) is polymethyl methacrylate, the ordinary glass mainly contains sodium silicate, silica, and calcium silicate, and the quartz glass contains silica.

Preferably, the roughness of the surface of the substrate is less than 1.0 micrometer (μm), for example, 0.1 μm, 0.5 μm, 0.7 μm, 0.9 μm, and the like, and the smaller the roughness of the substrate surface, i.e., the smoother the substrate surface, so that the smoother the surface of the finally obtained piezoelectric thin film, the higher the flatness, and the improved the quality of the piezoelectric thin film.

Step S103: and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated.

The piezoelectric material is crystallized in the process of liquid film evaporation, and high-pressure polarization is carried out in the crystallization process, namely the high-pressure polarization is carried out in the process of obtaining the piezoelectric film. The field intensity of the high-voltage electric field is between 10MV/M and 50MV/M, and preferably the field intensity of the high-voltage electric field is the maximum field intensity which does not break down the liquid film.

It should be noted that the high voltage electric field may be a continuous dc high voltage electric field or an ac high voltage electric field, and is not particularly limited in this application.

According to the piezoelectric film preparation method, a liquid film is formed on the surface of the substrate by utilizing a solution in which a piezoelectric material is dissolved, then the substrate with the liquid film is placed in a high-pressure environment, high-pressure polarization is carried out on the liquid film while evaporation crystallization is carried out, the molecular crystallinity and the crystal phase transformation of the piezoelectric material in the liquid film can be greatly improved, and the piezoelectric coefficient of the piezoelectric film is increased; the high-voltage polarization in the application effectively reduces the risk of high-voltage breakdown of the piezoelectric film in the process of preparing the piezoelectric film; and, adopt the mode of curtain coating to form the liquid film in this application, avoid the film to produce the defect in tensile in-process is inside, promote piezoelectric film quality, reduce the requirement to equipment simultaneously, simplify the preparation technology.

Referring to fig. 2, fig. 2 is a flowchart of another method for manufacturing a piezoelectric film according to an embodiment of the present disclosure, including:

step S201: preparing a solution in which the piezoelectric material powder is dissolved.

Step S202: removing bubbles from the solution.

Optionally, the removing bubbles in the solution includes:

carrying out ultrasonic treatment on the solution to remove bubbles in the solution;

and placing the solution after ultrasonic treatment in a vacuum environment, and removing bubbles in the solution again.

Optionally, the ultrasonic treatment time is 30min to 120min, so as to achieve a better defoaming effect; further, the time for vacuum bubble removal of the solution in a vacuum environment is 30min to 120min, so that bubbles still existing in the solution after ultrasonic treatment are further removed, the bubbles are completely removed, and the compactness of the piezoelectric film is improved.

It should be noted that the bubbles in the solution can also be removed by sonication alone or by vacuum debubbling alone.

Step S203: casting the solution from which the bubbles are removed onto a surface of a substrate to form a liquid film on the surface.

Step S204: and (3) putting the substrate with the liquid film in a high-voltage electric field environment for polarization, and obtaining the piezoelectric film after the solvent in the liquid film is evaporated.

The application also provides a piezoelectric film, and the piezoelectric film is prepared by the piezoelectric film preparation method in any embodiment.

The following explains the preparation method of the piezoelectric film by taking the preparation of the polyvinylidene fluoride piezoelectric film as an example.

Step 1, dissolving PVDF powder in N-methyl pyrrolidone to obtain a prefabricated solution;

step 2, stirring the prefabricated solution and continuously adding PVDF powder into the prefabricated solution to obtain a saturated PVDF solution;

step 3, carrying out ultrasonic treatment on the saturated PVDF solution, wherein the ultrasonic treatment time is 90 min;

step 4, placing the saturated PVDF solution after ultrasonic treatment in a vacuum environment for vacuum defoaming, wherein the vacuum defoaming time is 90 min;

step 5, uniformly casting the saturated PVDF solution subjected to vacuum defoaming on the surface of the organic glass;

and 6, putting the organic glass in a high-voltage electric field environment for polarization, and obtaining the PVDF piezoelectric film after the solvent in the saturated PVDF solution is evaporated. High-pressure polarization is carried out in the evaporation crystallization process of the saturated PVDF solution, so that the crystallinity and the content of beta-phase crystals in the PVDF piezoelectric film can be improved.

The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The piezoelectric thin film and the method for manufacturing the same provided by the present application are described in detail above. The principles and embodiments of the present application are explained herein using specific examples, which are provided only to help understand the method and the core idea of the present application. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.