Magnetoelectric composite material with piezoelectric sub-layer structure and preparation method thereof

Abstract

The application discloses a magnetoelectric composite material with a piezoelectric layered structure, which comprises a composite piezoelectric layer and a magnetostrictive composite layer, wherein the piezoelectric medium in the composite piezoelectric layer is distributed in a ferroelectric polymer matrix in the form of a deposited layer, and the magnetostrictive composite layer is formed by mixing a ferroelectric polymer and magnetic particles. The magnetoelectric composite material provided by the application has both ferroelectricity and ferromagnetism, has a high voltage coefficient and a magnetoelectric voltage coefficient, is good in flexibility, can be curled, is simple in preparation process operation, can be prepared in a large area, and can be used in the fields of magnetoelectric sensors, energy harvesters and other functional devices.

Description

Technical Field

[0001] This invention belongs to the field of magnetoelectric functional materials and their preparation technology, specifically relating to a magnetoelectric composite material with a piezoelectric layered structure and its preparation method. Background Technology

[0002] With the rapid development of electronic materials and devices, single-function materials are insufficient to meet the miniaturization and multifunctionality requirements of new electronic components. Therefore, the development of multifunctional composite materials has become a research hotspot in the materials field. Multiferromagnetic-electric composite materials are a new type of multifunctional material that combines piezoelectric and magnetostrictive phases to achieve strong coupling. They not only possess all the properties of single ferroelectric and ferromagnetic materials, but also exhibit a novel functional effect—the magnetoelectric coupling effect—generated by the ordered coupling of ferroelectric and magnetic forces. This allows for the mutual conversion and control of electrical and magnetic energy, as well as electrical and magnetic information, making them potentially applicable in fields such as energy harvesting, sensors, data storage, tunable capacitors and inductors, spintronic devices, and multi-state storage components.

[0003] Compared to ferroelectric ceramics, ferroelectric polymers exhibit better flexibility, greater anti-aging properties, and greater elastic deformation compared to inorganic ceramics. While ceramic-based magnetoelectric composites possess high magnetoelectric coupling performance, their matrix is ​​still predominantly ceramic, inevitably leading to poor overall flexibility, insufficient fatigue resistance, and susceptibility to breakage and performance degradation during use. Polymer-based magnetoelectric composites offer new avenues for the design and fabrication of next-generation functional materials and devices in chemical, physical, and biological wearable and soft robotics fields, attracting significant attention from researchers. On one hand, these materials retain the advantages of both organic polymers and magnetic materials, such as piezoelectric, ferroelectric, and magnetostrictive properties, and can generate strong magnetoelectric coupling responses. On the other hand, compared to traditional bulk materials, polymer-based magnetoelectric composites offer advantages such as good processability and mechanical properties, high flexibility, and the ability to form various complex shapes. Polymer-based magnetoelectric composites primarily consist of ferromagnetic nanoparticles or nanofibers dispersed within ferroelectric polymers. These materials possess excellent flexibility and bending resistance, making them better suited to the development of flexible electronics technology and playing a crucial role in the development of multifunctional integrated micro- and nano-devices. Currently, many studies focus on improving the magnetoelectric coupling performance of polymer-based magnetoelectric composites by changing the type of magnetic filler material, optimizing volume content, and adjusting the input field strength. However, these methods have very limited effects on improving magnetoelectric coupling performance, making it difficult to apply the resulting devices in practical applications. By utilizing microstructure and composite configuration design, the magnetoelectric coupling performance of polymer-based magnetoelectric composites can be significantly improved while maintaining good flexibility and processability, providing a wider range of applications. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a magnetoelectric composite material with excellent comprehensive magnetoelectric performance. This composite material has a magnetoelectric conversion coefficient, good mechanical properties, and a simple preparation process, dimensional stability, and high production efficiency. It solves the problems of low magnetoelectric coupling performance and complex preparation processes in existing technologies, and can be used in the field of flexible electronic functional devices such as flexible magnetoelectric sensors and energy harvesters.

[0005] The technical solution of the present invention is as follows:

[0006] A magnetoelectric composite material with a piezoelectric layered structure includes a composite piezoelectric layer and a magnetostrictive composite layer. The piezoelectric medium in the composite piezoelectric layer is distributed in the form of a deposited layer in a ferroelectric polymer matrix. The magnetostrictive composite layer is composed of a mixture of ferroelectric polymer and magnetic particles.

[0007] Preferably, the ferroelectric polymer is vinylidene fluoride-trifluoroethylene copolymer P (VDF-TrFE) or polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP).

[0008] Preferably, the piezoelectric dielectric in the composite piezoelectric layer is nano-BaTiO3 or nano-Bi. 0.5 Na 0.5 TiO3, nano-Pb(Zr) 0.52 Ti 0.48 One or more of O3, with a particle size of 50nm to 200nm.

[0009] Preferably, the magnetic particles in the magnetostrictive composite layer are spinel ferrite, which can be NiFe2O4 or Ni 0.8 Zn 0.2 Fe2O4 with a particle size of 0.05μm to 2μm, wherein the mass ratio of spinel ferrite to ferroelectric polymer is 0.2 to 0.5:1.

[0010] Preferably, the thickness ratio of the composite piezoelectric layer to the magnetostrictive composite layer is 1:3 to 1:6.

[0011] The present invention also provides a method for preparing the above-mentioned magnetoelectric composite material with a piezoelectric layered structure, comprising the following steps:

[0012] Step 1, Piezoelectric paste preparation: Dissolve piezoelectric nanoparticles in an inorganic solvent, and sonicate to obtain a uniform piezoelectric paste;

[0013] Step 2, piezoelectric powder layer formation: The piezoelectric paste obtained in Step 1 is uniformly coated onto the substrate using a scraping or printing process. The wet film is heated and then cooled and dried. After the solvent has completely evaporated, the piezoelectric powder layer is formed.

[0014] Step 3, coating the piezoelectric powder layer with ferroelectric polymer: the ferroelectric polymer solution is coated onto the piezoelectric powder layer obtained in step 2 using spin coating or blade coating process, the resulting composite wet film is heated and pre-cured until the ferroelectric polymer solution completely penetrates into the piezoelectric powder layer and encapsulates the nanoparticles to obtain the composite piezoelectric layer;

[0015] Step 4, forming of magnetostrictive composite layer: ferrite particles and ferroelectric polymer composite slurry are prepared in a mass ratio of 0.2 to 0.5:1, stirred evenly, and coated on any surface of the composite piezoelectric layer obtained in step 3 by spin coating or scraping to obtain a layered wet film.

[0016] Step 5, Curing and Shaping of Magnetoelectric Composite Film: The layered wet film obtained in Step 4 is cured at high temperature, cooled, and peeled off from the substrate to obtain the magnetoelectric composite material.

[0017] Preferably, in step one, the inorganic solvent is one of ethanol, ethylene glycol, or acetone.

[0018] Preferably, in step three, the heating pre-curing time is 5-8 minutes and the temperature is 80-90°C.

[0019] Preferably, in step five, the high-temperature curing temperature is 200–210°C, and the curing time is 10–20 min.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The composite material provided by this invention is designed with a layered structure at the microstructure level. This layered configuration increases the resistivity of the composite material and reduces the leakage current, improves the polarization capability of the composite material, significantly improves the polarization charge and piezoelectric properties of the composite material, and achieves high tunability of the magnetoelectric coupling performance of the composite material.

[0022] 2. This invention obtains a magnetostrictive composite layer by composite filling of submicron ferrite particles with ferroelectric material. The magnetostrictive layer generates a large deformation under the action of a magnetic field and is directly loaded onto the ferroelectric polymer matrix with layered piezoelectric nanoparticles, generating a large voltage output.

[0023] 3. Both the composite piezoelectric layer and the magnetostrictive composite layer of the present invention contain ferroelectric polymers, which can make the composite piezoelectric layer and the magnetostrictive composite layer tightly bonded through the ferroelectric polymer matrix contained in both. The polymer solution penetrates into the interior of the piezoelectric powder layer and covers the surface of the nanomaterial. While constructing a flexible piezoelectric layer, it avoids the problem of cracking and delamination caused by the mismatch of the moduli of the piezoelectric medium and the magnetostrictive medium. It realizes that the magnetoelectric composite material can maintain high magnetoelectric coupling performance while having large-angle or large-range curling, folding and high stability.

[0024] 4. The preparation method provided by this invention achieves uniform film thickness of polymer-based magnetoelectric composite materials, and the resulting polymer magnetoelectric composite materials have good flexibility and stable performance. The thickness of the magnetoelectric composite material of this invention can be freely adjusted as needed, ranging from tens of micrometers to millimeters. It can also be arbitrarily cut into shapes according to the occasion. The process is simple to operate, can be mass-produced, and has low intermediate costs. This method is applicable to the preparation of other functional polymer-based composite materials such as dielectric energy storage polymers. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the preparation process of a magnetoelectric composite material with a piezoelectric layered structure according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the magnetoelectric composite material structure obtained in Example 1 of the present invention;

[0028] Figure 3 This is a cross-sectional morphology diagram of the magnetoelectric composite material obtained in Example 1 of the present invention;

[0029] Figure 4 These are bending and torsion photographs of the magnetoelectric composite material obtained in Example 1 of this invention;

[0030] Figure 5 X-ray image of the magnetoelectric composite material prepared in Example 1 of this invention;

[0031] Figure 6 The hysteresis loop diagram of the magnetoelectric composite material obtained in Example 1 of this invention;

[0032] Figure 7 The image shows the magnetoelectric voltage coefficient curve of the magnetoelectric composite material obtained in Example 1 of this invention. Detailed Implementation

[0033] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0034] Example 1:

[0035] The magnetoelectric composite material with a piezoelectric layered structure provided in this embodiment consists of a composite piezoelectric layer and a magnetostrictive composite layer. The composite piezoelectric layer has a thickness of 100 μm, and BaTiO3 piezoelectric powder with an average particle size of 100 nm is distributed in the ferroelectric polymer matrix through a deposition layer. The magnetostrictive composite layer has a thickness of 400 μm and is composed of a mixture of ferroelectric polymer and spinel ferrite NiFe2O4 magnetic particles, with a mixing mass ratio of 0.3. In this embodiment, the ferroelectric polymer is a vinylidene fluoride-trifluoroethylene copolymer P(VDF-TrFE).

[0036] The preparation method of the above-mentioned piezoelectric layered magnetoelectric composite material includes the following steps:

[0037] (1) Take 0.3g of nano BaTiO3 powder, add ethanol, prepare a 10mg / mL nano BaTiO3 and ethanol mixed solution, and sonicate for 30min to obtain piezoelectric paste;

[0038] (2) Clean the glass substrate with ethanol ultrasonically, and dry it in an oven at 60°C; apply a layer of piezoelectric paste obtained in step (1) to the clean substrate with a thickness of 150μm; place the obtained piezoelectric wet film in an oven, heat it at 60°C for 20min, and cool it naturally to room temperature to obtain a piezoelectric powder layer.

[0039] (3) Take 5g of P(VDF-TrFE) powder and place it in 30mL of DMF polar solvent. Stir magnetically for 30min to obtain a ferroelectric polymer solution. Coat the surface of the piezoelectric powder layer prepared in step (2) with the obtained ferroelectric polymer solution. The thickness of the scraper is 150μm. Place the coated wet film in an oven and heat it at 80℃ for 8min to pre-cur it (until the ferroelectric polymer completely penetrates into the piezoelectric powder layer and encapsulates the nanoparticles) to obtain a composite piezoelectric layer.

[0040] (4) Take 1.5g of magnetic NiFe2O4 particles and 12mL of ferroelectric polymer solution obtained in step (3), mix them and stir thoroughly, and sonicate for 30min to obtain ferrite particle and ferroelectric polymer composite slurry; apply magnetic composite slurry to the surface of composite piezoelectric layer obtained in step (3), with a scraper thickness of 600μm, to obtain a layered wet film.

[0041] (5) The layered wet film obtained in step (4) is dried in a drying oven at 80°C for 2 hours, and then the temperature is raised to 200°C and kept for 10 minutes. After curing and cooling, the film is peeled off from the substrate to obtain a flexible magnetoelectric composite material with a thickness of 500 μm.

[0042] Magnetoelectric composite performance test: After the magnetoelectric composite thin film material is obtained by ultrasonic cleaning step (5), low temperature conductive silver paste is coated on its front and back sides, dried, and placed in silicone oil at 110℃ for voltage polarization treatment with an electric field of 5kV / mm. After polarization for 1 hour, it is taken out and the magnetoelectric composite performance test is performed.

[0043] Through the above preparation process (as shown in the appendix) Figure 1 The magnetoelectric composite material (shown in the figure) has a layered structure as shown in the attached diagram. Figure 2 As shown. Figure 3 The image shows the cross-sectional morphology of the prepared magnetoelectric composite material. Figure 3 The cross-section of the magnetoelectric composite material in the left image shows no obvious microstructural defects such as pores, and it is clearly divided into two layers. The upper layer is a piezoelectric layer with deposited piezoelectric BaTiO3 nanopowder, and the lower layer is a magnetostrictive composite layer. Both layers are connected by a ferrite polymer matrix. In the magnified view of the layered microstructure (i.e. Figure 3 (Right figure) There is a clear boundary between the piezoelectric layer and the magnetostrictive composite layer, and the piezoelectric nanoparticles are distributed in the ferroelectric polymer matrix. Figure 4 The optical photographs show the flexible characteristics of this magnetoelectric composite material, including its bending and torsion capabilities. Figure 5 This is the XRD pattern of the magnetoelectric composite material provided in this embodiment. The magnetoelectric composite material provided in this embodiment is denoted as BT / (P@NFO), while the magnetoelectric composite material provided in the comparative example is denoted as P@NFO@BT. The raw materials and proportions used in the comparative example are the same as in this embodiment. The magnetoelectric composite material provided in the comparative example is prepared by a coating process in which BaTiO3 and NiFe2O4 are uniformly dispersed in a ferroelectric polymer matrix, where BT represents BaTiO3 and NFO represents NiFe2O4. Figure 5 It can be seen that this embodiment and the comparative embodiment are composed of NiFe2O4, BaTiO3 and ferroelectric polymer phases, without the formation of impurity phases. For example... Figure 6 As shown, the magnetoelectric composite material provided in this embodiment possesses excellent ferroelectric properties, and compared to the magnetoelectric composite material with layered nano-BaTiO3 distribution in the ferroelectric polymer matrix, the saturation polarization intensity is significantly improved. For example... Figure 7 As shown, the flexible magnetoelectric composite material prepared in this embodiment has a high magnetoelectric voltage coefficient, which can realize the efficient conversion of magnetic energy and electrical energy, and obtains a maximum magnetoelectric voltage coefficient of 83.38 (mV / cm·Oe). At the same time, the magnetoelectric composite material can obtain a large self-biased magnetoelectric voltage coefficient of 7.43 (mV / cm·Oe) when the bias magnetic field is 0Oe.

[0044] Example 2:

[0045] The difference between this embodiment and Embodiment 1 is that the piezoelectric layer thickness is 50 μm, and the piezoelectric dielectric in the piezoelectric layer uses Pb(Zr) with a particle size of 100 nanometers.0.52 Ti 0.48 O3; the thickness of the magnetostrictive composite layer is 300 μm.

[0046] The preparation method of this magnetoelectric composite material with a piezoelectric layered structure includes the following steps:

[0047] (1) Take 0.5g of nano Pb(Zr) 0.52 Ti 0.48 )O3 powder, add ethanol to prepare a 10 mg / mL nano BaTiO3 and ethanol mixed solution, and sonicate for 30 min to obtain piezoelectric paste;

[0048] (2) Clean the glass substrate ultrasonically with ethanol and dry it in a 60°C oven; coat a layer of piezoelectric Pb(Zr) onto the clean substrate. 0.52 Ti 0.48 O3 slurry, with a doctor blade thickness of 80μm, the wet film was placed in an oven and heated at 60℃ for 20min, and then naturally cooled to room temperature to obtain the piezoelectric powder layer;

[0049] (3) Weigh 5g of P(VDF-TrFE) powder and place it in 30mL of DMF polar solvent. Stir magnetically for 30min to obtain ferroelectric polymer solution. Spin coat the polymer solution onto the surface of the piezoelectric powder layer obtained in step (2) at a spin coating speed of 1200r / min for 20s. Place the spin-coated wet film in an oven and heat at 80℃ for 5min to pre-cur.

[0050] (4) Take 1.5g of magnetic NiFe2O4 particles and 12mL of the ferroelectric polymer solution prepared in step (2), mix them and stir thoroughly, and sonicate for 30min to obtain a composite slurry of ferrite particles and ferroelectric polymer; spin coat the magnetic composite slurry onto the surface of the composite piezoelectric layer obtained in step (3) at a spin coating speed of 1200r / min for 30s, and repeat twice.

[0051] (5) The layered wet film was dried in a drying oven at 80°C for 2 hours, and then the temperature was increased to 200°C and kept for 10 minutes. After curing and cooling, the film was peeled off from the substrate to obtain a flexible magnetoelectric composite material with a thickness of 300 μm.

[0052] The comprehensive magnetoelectric performance test is the same as in Example 1. The magnetoelectric composite material in this example has a high magnetoelectric voltage coefficient, which can realize the efficient conversion of magnetic energy and electrical energy. The maximum magnetoelectric voltage coefficient is 80.12 (mV / cm·Oe). At the same time, the magnetoelectric composite material can obtain a large self-biased magnetoelectric voltage coefficient of 6.64 (mV / cm·Oe) when the bias magnetic field is 0Oe.

[0053] Example 3:

[0054] The difference between this embodiment and Embodiment 1 is that the magnetostrictive composite layer is composed of a ferroelectric polymer and spinel ferrite Ni. 0.8 Zn 0.2 The magnetic particles are mixed with Fe2O4 at a mass ratio of 0.4, and the magnetostrictive composite layer is 300 μm thick. The ferroelectric polymer is polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP).

[0055] The preparation method of this magnetoelectric composite material with a piezoelectric layered structure includes the following steps:

[0056] (1) Take 0.3g of nano BaTiO3 powder, add ethanol, prepare a 10mg / mL nano BaTiO3 and ethanol mixed solution, and sonicate for 30min to obtain piezoelectric paste;

[0057] (2) Clean the glass substrate with ethanol using ultrasonic cleaning, and dry it in an oven at 60°C; apply a layer of piezoelectric BaTiO3 slurry to the clean substrate with a thickness of 100μm, place the wet film in an oven, heat it at 60°C for 20min, and cool it naturally to room temperature to obtain the piezoelectric powder layer.

[0058] (3) Weigh 5g of P(VDF-TrFE) powder and place it in 30mL of DMF polar solvent. Stir magnetically for 30min to obtain ferroelectric polymer solution. Coat the polymer solution on the surface of the piezoelectric powder layer obtained in step (2) with a scraper thickness of 100μm. Place the coated wet film in an oven and heat at 80℃ for 8min to pre-cur.

[0059] (4) Take 2g of magnetic Ni 0.8 Zn 0.2 12 mL of Fe2O4 particles and the ferroelectric polymer solution prepared in step (2) were mixed and stirred thoroughly, and ultrasonically treated for 30 min to obtain a composite slurry of ferrite particles and ferroelectric polymer; magnetic composite slurry was then coated on the surface of the composite piezoelectric layer obtained in step (3) with a scraper thickness of 500 μm.

[0060] (5) The layered wet film was dried in a drying oven at 80°C for 2 hours, and then the temperature was increased to 200°C and kept for 10 minutes. After curing and cooling, the film was peeled off from the substrate to obtain a flexible magnetoelectric composite material with a thickness of 400 μm.

[0061] The method for testing the comprehensive magnetoelectric performance in this embodiment is the same as in Embodiment 1. The resulting magnetoelectric composite material has a high magnetoelectric voltage coefficient, which can realize efficient conversion between magnetic energy and electrical energy. The maximum magnetoelectric voltage coefficient is 90.12 (mV / cm·Oe), and a relatively large self-biased magnetoelectric voltage coefficient of 8.13 (mV / cm·Oe) can be obtained.

Claims

1. A magnetoelectric composite material with a piezoelectric layered structure, characterized in that: The magnetoelectric composite material includes a composite piezoelectric layer and a magnetostrictive composite layer. In the composite piezoelectric layer, the piezoelectric medium is distributed in the form of a deposited layer in the ferroelectric polymer matrix. The magnetostrictive composite layer is composed of a mixture of ferroelectric polymer and magnetic particles. The mass ratio of magnetic particles to ferroelectric polymer in the magnetostrictive composite layer is 0.2~0.5:

1.

2. The magnetoelectric composite material with a piezoelectric layered structure as described in claim 1, characterized in that: The ferroelectric polymer is vinylidene fluoride-trifluoroethylene copolymer P (VDF-TrFE) or polyvinylidene fluoride-hexafluoropropylene copolymer P (VDF-HFP).

3. The magnetoelectric composite material with a piezoelectric layered structure as described in claim 1, characterized in that: The piezoelectric dielectric in the composite piezoelectric layer is nano-BaTiO3 and nano-Bi. 0.5 Na 0.5 TiO3, nano-Pb(Zr) 0.52 Ti 0.48 One or more of O3, with a particle size range of 50 nm to 200 nm.

4. The magnetoelectric composite material with a piezoelectric layered structure as described in claim 1, characterized in that: The magnetic particles in the magnetostrictive composite layer are spinel ferrite NiFe2O4 or Ni 0.8 Zn 0.2 One of the Fe2O4 types, with a particle size range of 0.05 μm to 2 μm.

5. The magnetoelectric composite material with a piezoelectric layered structure as described in claim 1, characterized in that: The thickness ratio of the composite piezoelectric layer to the magnetostrictive composite layer is 1:3 to 1:

6.

6. A method for preparing a magnetoelectric composite material with a piezoelectric layered structure, characterized in that, Includes the following steps: Step (1) Piezoelectric paste preparation: Dissolve piezoelectric nanoparticles in an inorganic solvent to obtain piezoelectric paste; Step (2) Piezoelectric powder layer formation: The piezoelectric paste obtained in step (1) is uniformly coated on the substrate, the wet film is heated and cooled to dry, forming a piezoelectric powder layer; Step (3) Coating the piezoelectric powder layer with ferroelectric polymer: Coating the ferroelectric polymer solution onto the piezoelectric powder layer obtained in step (2) to obtain a composite wet film, and pre-curing it by heating to obtain a composite piezoelectric layer; Step (4) Magnetostrictive composite layer forming: Prepare a composite slurry of ferrite particles and ferroelectric polymer at a mass ratio of 0.2~0.5:1, stir evenly, and coat any surface of the composite piezoelectric layer obtained in step (3) with the composite slurry to obtain a layered wet film; Step (5) Curing and molding of magnetoelectric composite film: After curing and cooling the layered wet film obtained in step (4), the magnetoelectric composite material is obtained.

7. The preparation method according to claim 6, characterized in that: In the composite piezoelectric layer, the piezoelectric dielectric is distributed in the form of a deposited layer in the ferroelectric polymer matrix.

8. The preparation method according to claim 6, characterized in that: In step (3), the heating pre-curing time is 5~8 min and the temperature is 80~90 ℃.

9. The preparation method according to claim 6, characterized in that: In step (5), the curing temperature is 200~210 °C and the curing time is 10~20 min.

10. The preparation method according to claim 6, characterized in that: Step (3) Heat the obtained composite wet film to pre-cur it until the ferroelectric polymer solution completely penetrates into the piezoelectric powder layer.

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