KR20220152747A - Manufacturing method of magnetoelectric composite and magnetoelectric composite using them - Google Patents

Abstract

The present invention relates to a manufacturing method of a magnetoelectric compound and a magnetoelectric compound manufactured by the same, which can effectively induce aligned polarization of a piezoelectric layer. According to one embodiment of the present invention, the manufacturing method of a magnetoelectric compound comprises: a step of preparing a magnetostriction layer; a step of coating a magnetostriction solution including a first solvent and a ferrite-based magnetostriction material on the magnetostriction layer to form a coating layer to manufacture a half-finished product; a step of heat-treating the half-finished product to increase the specific surface area and surface charge of the coating layer; and a step of coating a piezoelectric solution including a piezoelectric material on the coating layer, and heat-treating the coated piezoelectric solution to form a piezoelectric layer while inducing aligned polarization of the piezoelectric material. According to another embodiment of the present invention, the magnetoelectric compound comprises: a magnetostriction layer; a coating layer formed on the magnetostriction layer, including a ferrite-based magnetostriction material, and having a contact angle of 1-40°; and a piezoelectric layer formed on the coating layer, and including a piezoelectric material of which aligned polarization is induced by the surface charge of the coating layer.

Description

Manufacturing method of magnetoelectric composite and magnetoelectric composite manufactured thereby

The present invention relates to a method for manufacturing a magnetoelectric composite based on magnetostrictive and piezoelectric properties and a magnetoelectric composite manufactured thereby.

The magnetoelectric complex includes a magnetostrictive phase and a piezoelectric phase, and magnetostriction is induced in the magnetostrictive phase according to a change in an external magnetic field. As a result, it has a magnetoelectric characteristic that can obtain an output voltage.

Magnetoelectric composites are applied to various fields such as energy harvesting devices, highly sensitive magnetic field sensors, actuators, memory devices, and drug delivery systems due to the magnetoelectric properties described above.

As one of these magnetoelectric composites, a magnetoelectric composite having a laminated structure including a piezoelectric layer having piezoelectricity and a magnetostrictive layer laminated on the piezoelectric layer and having magnetostrictive properties is used. A magnetoelectric composite having a laminated structure according to the prior art has been manufactured by bonding a piezoelectric layer and a magnetostrictive layer using an epoxy adhesive.

However, as the self-electric composite having a laminated structure manufactured according to the prior art uses an epoxy adhesive, not only the cost of providing the epoxy adhesive and the process of applying and curing the epoxy adhesive must be accompanied, but the applied When the epoxy adhesive is cured, magnetostriction of the magnetostrictive layer is hindered due to the strength of the epoxy adhesive, and strain transmission loss to the piezoelectric layer occurs, resulting in a drop in output voltage.

In addition, in the magnetoelectric laminate according to the prior art, it is essential to induce aligned polarization of the piezoelectric phase in order to obtain a magnetoelectric output voltage, and accordingly, a poling process for applying a high field is essential in manufacturing the magnetoelectric laminate. There was a disadvantage that the process was complicated because it was required.

Republic of Korea Patent Registration No. 10-1305271, registered on September 2, 2013 Republic of Korea Patent Publication No. 10-2018-0021457, published on March 5, 2018

An object of the present invention is to solve the above problems, and in the manufacture of a magnetoelectric composite, not only do not use an epoxy adhesive, but also do not require a poling process for inducing aligned polarization of a piezoelectric phase. A method for manufacturing a magnetoelectric composite by forming a coating layer containing a field magnetostrictive material to manufacture a semi-finished product, heat-treating the formed semi-finished product, and forming a piezoelectric layer on the coating layer to manufacture a magnetoelectric composite, and a magnetoelectric composite manufactured thereby is to provide

The object of the present invention is not limited to the object mentioned above, and other objects not mentioned will be clearly understood from the description below.

In order to achieve the above object, a method for manufacturing a magnetoelectric composite according to an embodiment of the present invention includes preparing a magnetostrictive layer, applying a magnetostrictive solution containing a ferrite-based magnetostrictive material and a first solvent on the magnetostrictive layer to form a coating layer. forming a semi-finished product, heat-treating the semi-finished product to increase the surface charge and specific surface area of the coating layer, applying a piezoelectric solution containing a piezoelectric material on the coating layer, and heat-treating the applied piezoelectric solution to align the piezoelectric material and forming a piezoelectric layer while inducing a polarization.

In order to achieve the above object, a magnetoelectric composite according to another embodiment of the present invention is formed on a magnetostrictive layer, a coating layer formed on the magnetostrictive layer and containing a ferritic magnetostrictive material and having a contact angle of 1 to 40 °, and a coating layer, and a piezoelectric layer including a piezoelectric material in which ordered polarization is induced by the surface charge of the coating layer.

The method for manufacturing a magnetoelectric composite according to an embodiment of the present invention and the magnetoelectric composite manufactured thereby can expect the following effects.

In the manufacture of the magnetoelectric composite, the surface charge of the coating layer may increase as the semi-finished product is heat-treated, and accordingly, the piezoelectric layer formed on the coating layer is induced to polarize the piezoelectric layer in order by the surface charge of the coating layer, resulting in a separate poling process Even if this is not accompanied, the magnetoelectric output voltage can be expressed.

By applying a piezoelectric solution on the coating layer and subjecting it to heat treatment to form a piezoelectric layer, the magnetostrictive phase and the piezoelectric phase can be combined without using a separate adhesive. Accordingly, when the magnetostrictive layer and the coating layer are magnetostricted, the strain is effectively transferred to the piezoelectric layer. can

In the manufacture of the magnetoelectric composite, as the semi-finished product is heat-treated, the specific surface area of the coating layer increases, and as a result, the contact area between the coating layer and the piezoelectric layer is relatively increased, so that the electrostatic interaction between the coating layer and the piezoelectric layer can be achieved more effectively. Aligned polarization induction of the layers can be achieved more effectively.

1 is a flow chart showing the sequence of a method for manufacturing a magnetoelectric composite according to an embodiment of the present invention.
2 is a view for explaining a magnetoelectric composite according to another embodiment of the present invention.
3a and 3b are diagrams showing magnetic hysteresis curve measurement results according to Test Example 1;
4 is a view showing the results of X-ray diffraction analysis according to Test Example 2.
5 is a graph showing contact angle measurement results according to Test Example 3.
6a to 6d are views showing the contact angle measurement results according to Test Example 3 and the analysis results using a scanning electron microscope.
7 is a diagram showing analysis results using a coupled ion beam electron microscope/energy dispersive spectrometer according to Test Example 4;
8 is a view showing the results of infrared spectroscopy analysis according to Test Example 5;
9 is a view showing the results of X-ray diffraction analysis according to Test Example 5.
10A to 10C are diagrams showing measurement results of magnetoelectric output voltages according to Test Example 8;

Advantages and features of the present invention, and methods of achieving them, will become clear with reference to the detailed description of the following embodiments taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only the present embodiments make the disclosure of the present invention complete, and those skilled in the art in the art to which the present invention belongs It is provided to fully inform the person of the scope of the invention. Meanwhile, terms used in this specification are for describing embodiments, and are not intended to limit the present invention. In this specification, singular forms also include plural forms unless specifically stated otherwise in a phrase.

A method for manufacturing a magnetoelectric composite according to an embodiment of the present invention includes time-sequential steps for manufacturing a magnetoelectric composite according to another embodiment of the present invention.

For convenience of explanation, substantially the same components are described with identical reference numerals in the description of the manufacturing method of the magnetoelectric composite according to the embodiments of the present invention and the magnetoelectric composite manufactured thereby, and repeated description is omitted. do.

Hereinafter, a method for manufacturing a magnetoelectric composite according to embodiments of the present invention and a magnetoelectric composite manufactured thereby will be described with reference to the accompanying drawings.

Referring to FIG. 1 , the method for manufacturing a magnetoelectric composite according to an embodiment of the present invention includes a magnetostrictive layer preparation step (S100), a semi-finished product manufacturing step (S200), a heat treatment step (S300), and a piezoelectric layer forming step (S400). include

Referring to FIG. 2 , a magnetoelectric composite 10 according to another embodiment of the present invention includes a magnetostrictive layer 100 , a coating layer 200 , a piezoelectric layer 300 and an oxide layer 400 .

First, a magnetostrictive layer is prepared (S100).

The magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) is not limited as long as it has ferromagnetism and includes a material having magnetostriction that is accompanied by mechanical deformation when magnetized. For example, It may include at least one selected from ferromagnetic metals, ferritic ceramics, magnetostrictive alloys and magnetic shape memory alloys.

Here, the ferromagnetic metal may include nickel (Ni), cobalt (Co), and iron (Fe), and ferritic ceramics may include Fe ₃ O ₄ , NiFe ₂ O ₄ , MnFe ₂ O ₄ , (Ni,Zn)Fe ₂ O ₄ , (Mn,Zn)Fe ₂ O ₄ , CoFe ₂ O ₄ and γ-Fe ₂ O ₃ , and the magnetostrictive alloy may include Terfenol-D, Gafenol, Samfenol-D, Metglas and FeCoB. can

Preferably, the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) may include nickel (Ni).

The magnetostrictive layer preparation step (S100) may be to prepare the magnetostrictive layer 100 in the form of a film having a predetermined thickness, but is not limited thereto.

The magnetostrictive layer preparation step ( S100 ) may further include an etching step.

The etching step may be a step of removing impurities that may exist in the magnetostrictive layer 100 by treating the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step S100 with an etching solution.

The etching step may be a step of removing impurities that may exist in the magnetostrictive layer 100 by immersing the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step S100 in an etching solution for a predetermined time.

In the etching step, the etching solution is not limited as long as it can remove impurities from the magnetostrictive layer 100, but may include hydrogen fluoric acid, hydrogen peroxide, and water.

When the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) includes nickel, the etching step is performed by treating the magnetostrictive layer 100 in an etching solution to obtain nickel oxide (NiO), which is an impurity that may exist in the magnetostrictive layer 100. ) may be a step of removing.

A semi-finished product is manufactured by forming a coating layer 200 containing a ferrite-based magnetostrictive material on the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) (S200).

If the coating layer 200 formed on the magnetostrictive layer 100 in the semi-finished product manufacturing step (S200) includes a ferrite-based magnetostrictive material, the coating layer 200 has a negative surface charge, so in the piezoelectric layer forming step (S400) to be described later, the coating layer 200 has a negative surface charge. The piezoelectric layer 300 formed on 200 and the coating layer 200 can interact electrostatically, and thus, aligned polarization of the piezoelectric layer 300 can be induced without a separate poling process. have.

The ferrite-based magnetostrictive material included in the coating layer 200 formed on the magnetostrictive layer 100 in the semi-finished product manufacturing step (S20) may have a form of AFe ₂ O ₄ .

Here, A may include one selected from among cobalt (Co), iron (Fe), manganese (Mn), nickel (Ni), and zinc (Zn), and may be preferably cobalt.

Cobalt is known to have relatively excellent magnetic properties, and accordingly, when A is cobalt, the magnetoelectric composite 10 manufactured according to an embodiment of the present invention may have more excellent magnetic properties.

Meanwhile, the piezoelectric material included in the piezoelectric layer 300 is known to have various crystal structures, and when the aligned polarization of the piezoelectric material included in the piezoelectric layer 300 is induced, the crystallinity of the piezoelectric material increases and at the same time the crystal structure can be converted into a crystal structure with a relatively high piezoelectricity.

For example, polyvinylidene fluoride, which is a piezoelectric material, is known to have a plurality of crystal phases including an α phase and a β phase, and when aligned polarization is induced, polyvinylidene fluoride At the same time as the crystallinity is increased, the crystal structure may be converted into a beta phase having relatively high piezoelectricity.

That is, when the piezoelectric material included in the piezoelectric layer 300 includes polyvinylidene fluoride, the ordered polarization of the piezoelectric layer 300 occurs as the coating layer 200 and the piezoelectric layer 300 interact electrostatically. When induced, the crystallinity of the piezoelectric material included in the piezoelectric layer 300 may be increased, and the crystal structure of polyvinylidene fluoride, which is a piezoelectric material, may be converted into a beta phase having relatively high piezoelectricity.

The semi-finished product manufacturing step (S200) may include a magnetostrictive solution manufacturing step (S210) and a magnetostrictive solution application step (S220).

The magnetostrictive solution preparation step (S210) may be a step of preparing a magnetostrictive solution containing a ferrite-based magnetostrictive material.

The magnetostrictive solution preparation step (S210) may be a step of preparing a magnetostrictive solution including a ferrite magnetostrictive material by mixing a precursor of the ferrite magnetostrictive material and the first solvent.

For example, when the magnetostrictive solution prepared in the magnetostrictive solution manufacturing step (S210) includes a ferrite-based magnetostrictive material having a form of CoFe ₂ O ₄ , the magnetostrictive solution manufacturing step (S210) includes ferrite having a form of CoFe ₂ O ₄ Iron nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O) and cobalt nitrate hexahydrate (Co(NO ₃ ) ₂ ) 6H ₂ O), which are precursors of field magnetostrictive materials, are mixed with 2-methoxyethanol as the first solvent. It may be a step of preparing a magnetostrictive solution including a ferrite-based magnetostrictive material having a form of CoFe ₂ O ₄ by mixing with (2-methoxy ethanol).

When the magnetostrictive solution containing the ferrite magnetostrictive material is prepared by mixing the ferrite magnetostrictive material precursor and the first solvent in the magnetostrictive solution preparation step (S210), the first solvent can dissolve the ferrite magnetostrictive material precursor without damaging it. Any solvent that can be used is not limited, and may be, for example, a solvent containing at least one selected from water and alcohol, and may include 2-methoxyethanol.

In the magnetostrictive solution application step (S220), a coating layer 200 is formed by applying the magnetostrictive solution prepared in the magnetostrictive solution preparation step (S210) on the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) to manufacture a semi-finished product may be a step.

In the magnetostrictive solution application step (S220), the magnetostrictive solution prepared in the magnetostrictive solution preparation step (S210) is applied on the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100), and the applied magnetostrictive solution is heated at 100 to 250 ° C. It may be a step of forming the coating layer 200 by drying in.

The semi-finished product manufactured in the semi-finished product manufacturing step (S200) is heat-treated (S300).

In the heat treatment step (S300), when the semi-finished product manufactured in the semi-finished product manufacturing step (S200) is heat-treated, the surface charge of the coating layer 200 may increase.

In the heat treatment step (S300), heat treatment of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) can improve the crystallinity of the coating layer 200, and when the crystallinity of the coating layer 200 is improved, the surface charge of the coating layer 200 increases. can increase

In the heat treatment step (S300), when the surface charge of the coating layer 200 is increased by heat-treating the semi-finished product manufactured in the semi-finished product manufacturing step (S200), the piezoelectric layer ( 300) and the coating layer 200 can be relatively smoother in electrostatic interaction, and thus, aligned polarization of the piezoelectric layer 300 can be induced relatively more effectively.

The first solvent may remain in the coating layer 200 of the semi-finished product manufactured in the semi-finished product manufacturing step (S200), and when the semi-finished product is heat-treated in the heat treatment step (S300), the first solvent remaining in the coating layer 200 is evaporated and removed. can

At this time, as the first solvent remaining in the coating layer 200 is evaporated and removed, pores may be formed in the coating layer 200, and as the surface of the coating layer 200 is roughened by the formed pores, the coating layer 200 may increase the specific surface area of

That is, when the specific surface area of the coating layer 200 increases as the first solvent remaining in the coating layer 200 is removed by heat-treating the semi-finished product in the heat treatment step (S300), the contact area between the coating layer 200 and the piezoelectric layer 300 increases. By relatively increasing the aligned polarization of the piezoelectric layer 300 can be more effectively induced.

In addition, when the semi-product manufactured in the semi-finished product manufacturing step (S200) is heat-treated in the heat treatment step (S300), the surface of the coating layer 200 becomes rough as the crystal grains of the ferritic magnetostrictive material included in the coating layer 200 grow. As a result, the specific surface area of the coating layer 200 may increase.

That is, when the specific surface area of the coating layer 200 is increased by the crystal grain growth of the ferritic magnetostrictive material included in the coating layer 200 by heat-treating the semi-finished product in the heat treatment step (S300), the contact between the coating layer 200 and the piezoelectric layer 300 Since the area is relatively increased, aligned polarization of the piezoelectric layer 300 can be more effectively induced.

However, if the crystal grains of the ferritic magnetostrictive material included in the coating layer 200 are excessively grown in the heat treatment step (S300), the pores formed in the coating layer 200 may be filled by the growing crystal grains. Accordingly, the coating layer 200 ), the specific surface area of the coating layer 200 may rather decrease.

In the heat treatment step (S300), when the semi-finished product manufactured in the semi-finished product manufacturing step (S200) is heat-treated, the surface charge and specific surface area of the coating layer 200 may increase, and accordingly, the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300). ) may have a contact angle of 1 to 40°.

Meanwhile, the contact angle described throughout the specification of the present invention may mean a water contact angle.

If the contact angle of the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300) exceeds 40°, it may mean that the surface charge and specific surface area of the coating layer 200 are not sufficiently improved. Accordingly, the coating layer 200 and the piezoelectric layer 300 may not effectively achieve an electrostatic interaction.

Preferably, the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300) may have a contact angle of 7 or more and less than 35°.

Meanwhile, when the semi-finished product is heat-treated in the heat treatment step (S300), not only can the surface charge and specific surface area of the coating layer 200 be increased, but also the magnetostrictive layer 100 is oxidized so that there is a gap between the magnetostrictive layer 100 and the coating layer 200. An oxide layer 400 may be formed.

As the oxide layer 400 is formed between the magnetostrictive layer 100 and the coating layer 200 in the heat treatment step (S300), the magnetoelectric composite 10 according to another embodiment of the present invention may include the oxide layer 400. have.

The oxide layer 400 may be formed by oxidizing the magnetostrictive layer 100 as the semi-finished product is heat treated in the heat treatment step (S300), and may have antiferromagnetism.

The oxide layer 400 may include nickel oxide (NiO) when the magnetostrictive layer 100 prepared in the magnetostrictive layer preparation step (S100) includes nickel.

If the magnetostrictive layer 100 has ferromagnetism and the oxide layer 400 has antiferromagnetism, the magnetic spin aligned in one direction of the magnetostrictive layer 100 having ferromagnetism at the interface between the magnetostrictive layer 100 and the oxide layer 400 has antiferromagnetism. An exchange spring effect can occur by aligning some of the reversely aligned magnetic spins of the oxide layer 400 in the same direction, and when the exchange spring effect occurs, the coercive force of the semi-finished product is small. and permeability may increase.

That is, if the magnetostrictive layer 100 has ferromagnetism and the oxide layer 400 has antiferromagnetism, the magnetization of the semi-finished product obtained in the heat treatment step (S300) can be made in a relatively lower DC electric field range, according to an embodiment of the present invention. Magnetic properties of the manufactured magnetoelectric composite 10 may be improved.

The heat treatment step (S300) may be a step of heat-treating the semi-finished product manufactured in the semi-finished product manufacturing step (S200) at a temperature greater than 400 and less than 700°C.

In the heat treatment step (S300), if the heat treatment temperature of the semi-finished product is 400 ° C or less, the heat treatment temperature of the semi-finished product is low, so that the surface charge and specific surface area of the coating layer 200 may not be sufficiently increased, and the magnetostrictive layer ( 100) is not effectively oxidized, so the formation of the oxide layer 400 may not be performed smoothly.

In the heat treatment step (S300), when the heat treatment temperature of the semi-finished product is 700° C. or higher, the ferritic magnetostrictive material included in the coating layer 200 is melted due to the high heat treatment temperature of the semi-finished product, so that ions of the magnetostrictive material may be formed, and ions of the formed magnetostrictive material may be formed. As the magnetic properties of the coating layer 200 decrease by being diffused into the coating layer 200, the magnetic properties of the magnetoelectric composite 10 manufactured according to an embodiment of the present invention may decrease.

In the heat treatment step (S300), when the heat treatment temperature of the semi-finished product is 700° C. or higher, the crystal grains of the ferritic magnetostrictive material included in the coating layer 200 grow excessively due to the high heat treatment temperature of the semi-finished product, so that pores formed in the coating layer 200 can be removed. Accordingly, the specific surface area of the coating layer 200 may decrease.

In addition, in the heat treatment step (S300), when the heat treatment temperature of the semi-finished product is 700° C. or higher, the oxidation layer 400 is excessively formed due to the high heat treatment temperature of the semi-finished product, so that the ratio of the oxide layer 400 to the magnetostrictive layer 100 increases, resulting in the magnetic field of the semi-finished product. characteristics may decrease.

Preferably, the heat treatment step (S300) may be a step of heat-treating the semi-finished product manufactured in the semi-finished product manufacturing step (S200) at more than 400 ° C and less than 600 ° C, or may be a step of heat-treating at 500 to 600 ° C.

In the heat treatment step (S300), the heat treatment of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) may be performed for 30 minutes to 6 hours.

In the semi-finished product manufacturing step (S200), if the heat treatment time of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) is less than 30 minutes, the heat treatment time is too short, and the formation of the oxide layer 400 may not be sufficiently performed, and by heat-treating the semi-finished product, the coating layer ( 200) may decrease the effect of increasing the surface charge and specific surface area.

In the semi-finished product manufacturing step (S200), when the heat treatment time of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) exceeds 6 hours, the heat treatment time is sufficient and the surface charge and specific surface area of the coating layer 200 are sufficiently increased by heat-treating the semi-finished product. Further heat treatment may be meaningless, and the heat treatment time may be too long, so that the oxide layer 400 may be excessively formed and the magnetic properties of the semi-finished product may decrease.

Preferably, in the heat treatment step (S300), the heat treatment of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) may be performed for 1 to 5 hours, or may be performed for 2 to 4 hours.

More preferably, in the heat treatment step (S300), the heat treatment of the semi-finished product manufactured in the semi-finished product manufacturing step (S200) may be performed for 2 hours.

A piezoelectric layer 300 is formed on the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300) (S400).

The piezoelectric layer forming step (S400) may be a step of forming a piezoelectric layer 300 including a piezoelectric material having piezoelectric properties on the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300).

The piezoelectric layer forming step (S400) is a step of manufacturing the magnetoelectric composite 10 by forming a piezoelectric layer 300 containing a piezoelectric material having piezoelectric properties on the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300). can be

The piezoelectric layer forming step (S400) may include a piezoelectric solution preparation step (S410), a piezoelectric solution application step (S420), and a piezoelectric solution heating step (S430).

The piezoelectric solution preparation step ( S410 ) may be a step of preparing a piezoelectric solution by mixing a piezoelectric material and a second solvent.

In the piezoelectric solution preparation step (S410), the piezoelectric material is not limited as long as it includes a material having piezoelectricity, but may preferably include a polymer having piezoelectricity, for example, polyvinylidene fluoride (PVDF) ), polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)), polyvinylidene fluoride-tetrafluoroethylene (P(VDF-TeFE)) and It may contain at least one selected from triglycine sulphate.

In preparing the piezoelectric solution in the piezoelectric solution preparation step (S410), the second solvent mixed with the piezoelectric material is not limited as long as it can dissolve the piezoelectric material, but is preferably a polar solvent capable of dissolving the piezoelectric material. may be, for example, dimethylformamide (DMF), acetone, dimethylsulfoxide (DMSO), N-methylpyrrolidone (N-Methyl-2-pyrrolidone, NMP), methylethyl One selected from ketone (Methyl Ethyl Ketone, MEK), dimethylacetamide (DMAc), tetrahydrofuran (THF), hexamethylphosphoramide (HMPA) and triethyl phosphate It may contain, more preferably may be N- methylpyrrolidone (NMP).

The piezoelectric solution preparation step ( S410 ) may be a step of preparing a piezoelectric solution having a concentration of the piezoelectric material greater than 5 and less than 10wt% by mixing the piezoelectric material and the second solvent.

If the concentration of the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) is 5 wt% or less, the concentration of the piezoelectric material is too low and the second solvent evaporates too quickly in the piezoelectric solution heating step (S430), leading to ordered polarization of the piezoelectric material. may not sufficiently occur, and the piezoelectricity of the piezoelectric layer 300 formed in the piezoelectric layer forming step (S400) may deteriorate because the amount of the piezoelectric material included in the piezoelectric solution is too small.

If the concentration of the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) exceeds 10wt%, as the concentration of the piezoelectric material becomes too high, the viscosity of the piezoelectric solution becomes too high, making it difficult to induce aligned polarization of the piezoelectric material.

The piezoelectric solution application step (S420) may be a step of applying the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) on the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300).

In the piezoelectric solution application step (S420), when the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) is applied on the coating layer 200 of the semi-finished product, the piezoelectric material included in the piezoelectric solution electrostatically interacts with the coating layer 200. and, accordingly, an ordered polarization state of the piezoelectric material can be induced.

In the piezoelectric solution application step (S420), when the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) is applied on the coating layer 200 of the semi-finished product, the coating layer 200 has a negative surface charge, so the piezoelectric solution included in the piezoelectric solution The material may have an electrostatic interaction with the coating layer 200, and thus, an ordered polarization of the piezoelectric material may be induced.

The piezoelectric solution application step (S420) may be a step of applying the piezoelectric solution prepared in the piezoelectric solution preparation step (S410) to a thickness of 200 or more and less than 400 μm on the coating layer 200 of the semi-finished product obtained in the heat treatment step (S300). .

If the thickness of the piezoelectric solution applied on the coating layer 200 of the semi-finished product in the piezoelectric solution application step (S420) is less than 200 μm, the thickness of the piezoelectric layer 300 formed during heat treatment in the piezoelectric solution heating step (S430) becomes too thin. It may be difficult to obtain a reliable magnetoelectric output voltage from the magnetoelectric composite 10 manufactured according to an embodiment of the present invention.

In the piezoelectric solution application step (S420), when the thickness of the piezoelectric solution applied on the coating layer 200 of the semi-finished product is 400 μm or more, the thickness of the piezoelectric solution applied is too thick and the distance between the coating layer 200 and the coating layer 200 of the applied piezoelectric solution is too thick. There may be a part where the electrostatic interaction with the coating layer 200 is not achieved, and the piezoelectric material included in the part where the electrostatic interaction with the coating layer 200 is not effectively made in the applied piezoelectric solution has an ordered polarization. Since the state is not effectively induced, the piezoelectricity of the piezoelectric layer 300 manufactured in the piezoelectric layer forming step (S400) may deteriorate.

The piezoelectric solution heating step (S430) may be a step of forming the piezoelectric layer 300 on the coating layer 200 by heat-treating the semi-finished product coated with the piezoelectric solution on the coating layer 200 obtained in the piezoelectric solution application step (S420). .

The piezoelectric solution heating step (S430) heat-treats the semi-product coated with the piezoelectric solution on the coating layer 200 obtained in the piezoelectric solution application step (S420) to form a piezoelectric layer 300 on the coating layer 200, thereby forming a magnetoelectric composite ( 10) may be a step of preparing.

The piezoelectric solution heating step (S430) heat-treats the semi-product coated with the piezoelectric solution obtained in the piezoelectric solution application step (S420) to evaporate the second solvent of the piezoelectric solution applied on the coating layer 200 to form the piezoelectric layer 300. It may be a step to

The piezoelectric solution heating step (S430) heat-treats the piezoelectric solution coated with the piezoelectric solution obtained in the piezoelectric solution application step (S420) by heat-treating the piezoelectric solution while inducing aligned polarization of the piezoelectric materials included in the piezoelectric solution. It may be a step of forming the layer 300 .

In the piezoelectric solution heating step (S430), when the semi-finished product coated with the piezoelectric solution is heat-treated, thermal energy is applied to the piezoelectric material included in the piezoelectric solution applied on the coating layer 200, so that the aligned polarization state of the piezoelectric material is more actively induced. can

Accordingly, the piezoelectric layer 300 formed in the heating of the piezoelectric solution (S430) may include a piezoelectric material in which aligned polarization is induced by the surface charge of the coating layer 200.

Meanwhile, when the piezoelectric solution is applied on the coating layer 200 of the semi-finished product in the piezoelectric solution application step (S420), gaps may exist in the piezoelectric solution applied on the coating layer 200, and the piezoelectric solution is heated in the piezoelectric solution heating step (S430). When the coated semi-finished product is heat-treated, the piezoelectric material shrinks as the second solvent evaporates, removing pores existing in the piezoelectric solution applied on the coating layer 200, thereby forming the piezoelectric layer 300.

In the piezoelectric solution heating step (S430), when the piezoelectric layer 300 is formed as the second solvent of the piezoelectric solution applied on the coating layer 200 evaporates, the voids present in the piezoelectric solution are not sufficiently removed, and the piezoelectric layer 300 If the magnetoelectric composite 10 is manufactured according to an embodiment of the present invention, the magnetoelectric characteristics of the magnetoelectric composite 10 may decrease.

In the piezoelectric solution heating step (S430), the piezoelectric solution applied on the coating layer 200 obtained in the piezoelectric solution application step (S420) and the coating layer 200 are heat-treated at 50 or more and less than 110 ° C, so that the piezoelectric layer ( 300) may be a step of forming.

In the piezoelectric solution heating step (S430), if the heat treatment temperature is less than 50 ° C, the thermal energy applied to the piezoelectric material included in the piezoelectric solution applied on the coating layer 200 is insufficient, so that the aligned polarization state of the piezoelectric material is not effectively induced. may not be

In addition, if the heat treatment temperature in the piezoelectric solution heating step (S430) is less than 50° C., the evaporation rate of the second solvent is too low, so that pores existing in the piezoelectric solution may not be effectively removed. Accordingly, the formed piezoelectric layer 300 A void may remain in the magnetoelectric composite 10 manufactured according to the embodiment of the present invention, and thus the magnetoelectric characteristics of the magnetoelectric composite 10 may decrease.

In the piezoelectric solution heating step (S430), when the heat treatment temperature is 110° C. or higher, the evaporation rate of the second solvent included in the applied piezoelectric solution is so fast that the second solvent completely evaporates before the aligned polarization state of the piezoelectric material is sufficiently induced. Therefore, the piezoelectricity of the piezoelectric layer 300 manufactured in the piezoelectric layer forming step (S400) may deteriorate because the aligned polarization state of the piezoelectric material is not sufficiently induced.

In the piezoelectric solution heating step (S430), the semi-finished product coated with the piezoelectric solution on the coating layer 200 obtained in the piezoelectric solution application step (S420) is heat-treated to form a piezoelectric layer 300 having a thickness of 15 or more and less than 60 μm on the coating layer 200. It may be a step of forming a piezoelectric layer 300 having a thickness of 20 or more and less than 55 μm, or may be a step of forming a piezoelectric layer 300 having a thickness of 22 or more and less than 55 μm, or a piezoelectric layer having a thickness of 26 or more and less than 55 μm. It may be a step of forming the layer 300, a step of forming the piezoelectric layer 300 having a thickness of 22 or more and less than 33 μm, or a step of forming the piezoelectric layer 300 having a thickness of 26 or more and less than 31 μm.

According to the manufacturing method of the magnetoelectric composite according to another embodiment of the present invention, the magnetoelectric composite 10 exhibiting a sufficient magnetoelectric output voltage can be manufactured without a separate polling process.

The magnetoelectric composite 10 manufactured according to another embodiment of the present invention has the maximum magnetoelectric output voltage when measuring the magnetoelectric output voltage under the conditions of an alternating magnetic field of 1 Oe (Oersted, Oersted), a direct current magnetic field of -1000 to 1000 Oe, and a frequency of 1 kHz. The value may be 350 to 1250 μV/cm·Oe.

Preferably, the magnetoelectric composite 10 prepared according to another embodiment of the present invention has a maximum value of the magnetoelectric output voltage when the magnetoelectric output voltage is measured under the conditions of an alternating magnetic field of 100e, a direct current magnetic field of -1000 to 10000e, and a frequency of 1kHz. It may be greater than 375 and less than 1250 μV / cm Oe, more preferably, the maximum value of the magnetoelectric output voltage may be greater than 375 and less than 1231 μV / cm Oe, and may be greater than 467 and less than 1231 μV / cm Oe.

<Example 1>

1. Preparation of magnetostrictive layer

First, nickel (manufacturer: MTI Korea) in the form of a film having a thickness of 30 μm was prepared as the magnetostrictive layer 100. The prepared magnetostrictive layer 100 was mixed with hydrogen fluoride (product number: 33258, manufacturer: Alfa Aesar), hydrogen peroxide (product number: 4104-4100, manufacturer: Daejung Chemical Gold) and deionized water 1: 1: 20 for 15 minutes to remove impurities that may exist in the magnetostrictive layer 100. After taking out the magnetostrictive layer 100 from the etching solution, it was washed with deionized water and ethanol and dried.

2. Manufacturing and heat treatment of semi-finished products

(1) Manufacture of magnetostrictive solution

Iron nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O, product number: 216828, manufacturer: Sigma-Aldrich) 2 mmol and cobalt nitrate hexahydrate (Co(NO ₃ ) ₂ ) 6H2O, which are precursors of magnetostrictive materials, Product number: 239267, manufacturer: Sigma-Aldrich) 1 mmol was mixed with 2-methoxy ethanol (product number: 284467, manufacturer: Sigma-Aldrich) as the first solvent and stirred for 1 hour. After stabilization (aging) for 24 hours, a magnetostrictive solution containing a ferrite-based magnetostrictive material having a CoFe ₂ O ₄ form was prepared.

(2) Application of magnetostrictive solution

(1) The magnetostrictive solution prepared in Preparation of Magnetostrictive Solution was applied to the magnetostrictive layer 100 prepared in 1. Preparation of Magnetostrictive Layer, and dried at 200° C. to prepare a coating layer 200 to prepare a semi-finished product.

(3) Heat treatment of semi-finished products

(2) The semi-finished product obtained from the application of the magnetostrictive solution was heat-treated at 600° C. for 2 hours. At this time, the heat treatment of the semi-finished product used an electric heating furnace.

3. Formation of piezoelectric layer

piezoelectric material polyvinylidene fluoride (product number: 182702, manufacturer: Sigma-Aldrich) 1g and the second solvent N-methylpyrrolidone (product number: 443778, manufacturer: Sigma-Aldrich) 9g were mixed in a 30ml vial (vial), and mixed at 150 rpm using a magnetic bar at 50 ° C. for 5 hours to prepare a piezoelectric solution having a concentration of 10 wt% of the piezoelectric material.

The prepared piezoelectric solution was applied on the coating layer 200 of the semi-finished product to a thickness of 200 μm, and the coating layer 200 and the piezoelectric solution applied on the coating layer 200 were heat-treated at 80° C. for 8 hours to form the coating layer 200. A piezoelectric layer 300 was formed on the magnetoelectric composite 10.

<Example 2>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, 3. When the piezoelectric solution was applied on the coating layer 200 of the semi-finished product in the formation of the piezoelectric layer, it was applied to a thickness of 300 μm instead of 200 μm.

<Example 3>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, 3. In the formation of the piezoelectric layer, the piezoelectric solution was heat-treated at 50°C for 8 hours instead of heat-treated at 80°C for 8 hours.

<Example 4>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, 3. In the formation of the piezoelectric layer, when the piezoelectric solution was applied on the coating layer 200 of the semi-finished product, it was applied to a thickness of 300 μm instead of 200 μm, and the piezoelectric solution was heat treated at 80 ° C for 8 hours Instead, heat treatment was performed at 50° C. for 8 hours.

<Example 5>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, (3) in the heat treatment of the semi-finished product, instead of heat-treating the semi-finished product at 600°C for 2 hours, it was heat-treated at 500°C for 2 hours.

<Example 6>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, when preparing the piezoelectric solution in 3. Formation of the piezoelectric layer, a piezoelectric solution having a concentration of 7.5wt% of the piezoelectric material was prepared instead of preparing a piezoelectric solution having a concentration of 10wt% of the piezoelectric material.

<Comparative Example 1>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, 3. In the formation of the piezoelectric layer, when the piezoelectric solution was applied on the coating layer 200 of the semi-finished product, it was applied to a thickness of 400 μm instead of 200 μm.

<Comparative Example 2>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, instead of heat-treating the piezoelectric solution at 80° C. for 8 hours, heat treatment was performed at 110° C. for 8 hours.

<Comparative Example 3>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, 3. In the formation of the piezoelectric layer, when the piezoelectric solution was applied on the coating layer 200 of the semi-finished product, it was applied to a thickness of 300 μm instead of 200 μm, and the piezoelectric solution was heat treated at 80 ° C for 8 hours Instead, heat treatment was performed at 110° C. for 8 hours.

<Comparative Example 4>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, (3) heat treatment of semi-finished products was performed at 400 ° C for 2 hours instead of heat treatment at 600 ° C for 2 hours.

<Comparative Example 5>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, (3) heat treatment of the semi-finished product was performed at 700 ° C for 2 hours instead of heat treatment at 600 ° C for 2 hours.

<Comparative Example 6>

A magnetoelectric composite 10 was manufactured in the same manner as in Example 1. However, when preparing a piezoelectric solution in 3. Formation of the piezoelectric layer, a piezoelectric solution having a piezoelectric material concentration of 5wt% was prepared instead of a piezoelectric solution having a piezoelectric material concentration of 10wt%.

Manufacturing conditions of the magnetoelectric composites 10 according to Examples 1 to 6 and Comparative Examples 1 to 6 are summarized in Table 1 below.

Semi-manufactures
Heat treatment temperature (℃) piezoelectric solution
Coating thickness (㎛) piezoelectric solution
Concentration (wt%) piezoelectric solution
Heat treatment temperature (℃) Example 1 600 200 10 80 Example 2 600 300 10 80 Example 3 600 200 10 50 Example 4 600 300 10 50 Example 5 500 200 10 80 Example 6 600 200 7.5 80 Comparative Example 1 600 400 10 80 Comparative Example 2 600 200 10 110 Comparative Example 3 600 300 10 110 Comparative Example 4 400 200 10 80 Comparative Example 5 700 200 10 80 Comparative Example 6 600 200 5 80

In Table 1, 'semi-finished product heat treatment temperature' means the temperature at which the semi-finished product is heat-treated in (3) heat treatment of the semi-finished product, and 'piezoelectric solution coating thickness' means the thickness at which the piezoelectric solution is applied in 3. Formation of the piezoelectric layer. 'Concentration of piezoelectric solution' means the concentration of piezoelectric materials in the piezoelectric solution prepared in 3. Formation of the piezoelectric layer, and 'temperature of heat treatment of the piezoelectric solution' is the temperature at which the piezoelectric solution applied in 3. Formation of the piezoelectric layer is heat treated. It means.

<Test Example 1>

In Test Example 1, a magnetic hysteresis curve measuring device (model name: Model 7407-S, manufacturer: Lake Shore) was used to analyze the magnetic properties of the semi-finished products obtained from (3) heat treatment of the semi-finished products of Examples 1 and 5 and Comparative Examples 4 and 5. A magnetic hysteresis loop was measured using Cryotronics Inc.).

More specifically, in Test Example 1, the magnetization of the semi-finished product was measured while the intensity of the DC magnetic field applied from the outside was changed from -15000 to 15000 Oe, and this was shown as a magnetic hysteresis curve.

At this time, the magnetic hysteresis curve of nickel, which is the magnetostrictive layer 100 prepared in 1. Preparation of the magnetostrictive layer, which is not a semi-finished product obtained from (3) heat treatment of the semi-finished product, was also measured.

3a and 3b show the magnetic hysteresis curve measurement results according to Test Example 1.

3A and 3B are diagrams showing magnetic hysteresis curve measurement results according to Test Example 1 of nickel as the magnetostrictive layer 100 and semi-finished products obtained from manufacturing methods according to Examples 1 and 5 and Comparative Examples 4 and 5.

In more detail, FIG. 3A shows the magnetization measurement result 510 of the semi-finished product obtained in the manufacturing method according to Example 1 in a coordinate system in which the x-axis is the strength of the DC magnetic field and the y-axis is the magnetization, and in the manufacturing method according to Example 5 The result of measuring the magnetization degree of the semi-finished product (520), the result of measuring the magnetization degree of the semi-finished product obtained from the manufacturing method according to Comparative Example 4 (530), and the result of measuring the magnetization degree of the semi-finished product obtained from the manufacturing method according to Comparative Example 5 (540) and a magnetization measurement result 550 of nickel, which is the magnetostrictive layer 100.

FIG. 3B is an enlarged view of the measurement result corresponding to the case where the intensity of the DC magnetic field is -150 to 150 Oe in the magnetic hysteresis curve measurement result shown in FIG. 3A.

Referring to FIG. 3a, it can be seen that the saturation magnetization of nickel is the highest, and the saturation magnetization of the semi-finished products obtained from the manufacturing methods according to Examples 1 and 5 and Comparative Examples 4 and 5 is slightly higher than that of pure nickel. It can be confirmed that it falls, but it can be confirmed that the degree of falling is not so great.

However, it can be confirmed that the saturation magnetization of the semi-finished product obtained by the manufacturing method according to Comparative Example 5 is much lower than the saturation magnetization degree of the semi-finished product obtained by the manufacturing method according to Examples 1 and 5 and Comparative Example 4. This may be because the oxide layer 400 is excessively formed, so that the ratio of the oxide layer 400 to the magnetostrictive layer 100 is too large.

Referring to FIG. 3B, compared to the semi-finished products obtained from the heat treatment of nickel and the semi-finished products (3) of Comparative Example 4, the semi-finished products obtained from the heat treatment of Examples 1 and 5 and the semi-finished products of Comparative Example 5 (3) have higher permeability and magnetic coercive force. It can be confirmed that the coercive force is small, which means that the magnetization of the semi-finished product obtained from the manufacturing method according to Examples 1 and 5 and Comparative Example 5 can be performed more smoothly than the nickel and the semi-finished product obtained from the manufacturing method according to Comparative Example 4. This is a verifiable result.

That is, the magnetic properties of the semi-finished products obtained from the heat treatment of the (3) semi-finished products of Examples 1 and 5 and Comparative Example 5 are superior to those of the semi-finished products obtained from the heat treatment of nickel, which is the magnetostrictive layer 100, and the semi-finished products of Comparative Example 4 (3). This is a result that can be verified.

<Test Example 2>

In Test Example 2, the semi-finished products obtained from (3) heat treatment of Examples 1 and 5 and Comparative Examples 4 and 5 were analyzed by X-ray diffraction (X- Ray Diffraction) analysis.

At this time, X-ray diffraction analysis of nickel, which is the magnetostrictive layer 100 prepared in 1. Preparation of the magnetostrictive layer, not the semi-finished product obtained from (3) heat treatment of the semi-finished product, was also performed.

The analysis results are shown in FIG. 4 .

4 is a view showing the results of X-ray diffraction analysis according to Test Example 2 of nickel and semi-finished products obtained from the manufacturing methods according to Examples 1 and 5 and Comparative Examples 4 and 5.

In more detail, FIG. 4 shows the X-ray diffraction analysis result 610 according to Test Example 2 of the semi-finished product obtained from the manufacturing method according to Example 1 with nickel, and X according to Test Example 2 of the semi-finished product obtained from the manufacturing method according to Example 5. Ray diffraction analysis result (620), X-ray diffraction analysis result (630) according to Test Example 2 of the semi-finished product obtained from the manufacturing method according to Comparative Example 4, X according to Test Example 2 of the semi-finished product obtained from the manufacturing method according to Comparative Example 5 It is a diagram showing the ray diffraction analysis result 640 and the X-ray diffraction analysis result 650 according to Test Example 2 of nickel.

Referring to FIG. 4, it can be seen that as the heat treatment temperature of the semi-finished product increases, the intensity of the peak corresponding to nickel oxide increases. This is a verifiable result.

In addition, in the results of X-ray diffraction analysis of the semi-finished products obtained from the heat treatment of (3) semi-finished products of Examples 1, 5, and Comparative Example 5, a peak corresponding to cobalt ferrite can be confirmed, whereas a peak corresponding to (3) semi-finished products of Comparative Example 4 Referring to the result of X-ray diffraction analysis of the semi-finished product obtained from the heat treatment (630), it is difficult to identify a peak corresponding to cobalt ferrite. This is a verifiable result.

<Test Example 3>

In Test Example 3, the contact angle of the coating layer 200 of the semi-finished product obtained from (3) heat treatment of the semi-finished product of Examples 1 and 5 and Comparative Examples 4 and 5 was measured, and the surface was examined using a scanning electron microscope (Scanning Electron Microscopy, model name: JSM- 6700F, manufacturer: JEOL Ltd.).

In Test Example 3, the contact angle was measured using a contact angle measuring device (model name: FM-40, manufacturer: KRUSS Ltd.).

The contact angle measurement results are graphed in FIG. 5 , and the contact angle measurement results and scanning electron microscope measurement results are shown in FIGS. 6A to 6D .

The contact angle measurement results are summarized in Table 2 below with reference to FIG. 5 .

Example 1 Example 5 Comparative Example 4 Comparative Example 5 Contact angle (°) 7 27 35 11

Figure 6a is a view showing the scanning electron microscopic analysis of the coating layer 200 of the semi-finished product obtained in (3) heat treatment of the semi-product of Example 1, Figure 6b is a coating layer of the semi-finished product obtained in (3) heat treatment of the semi-finished product of Example 5 (200) is a view showing the scanning electron microscopic analysis result, and FIG. 6c is a view showing the scanning electron microscopic analysis result of the coating layer 200 of the semi-finished product obtained in (3) heat treatment of the semi-finished product of Comparative Example 4, and FIG. It is a diagram showing the results of scanning electron microscopic analysis of the coating layer 200 of the semi-finished product obtained in (3) heat treatment of the semi-finished product of Example 5.

First, referring to FIG. 5 and Table 2, it can be seen that the contact angle of the coating layer 200 of the semi-finished product obtained from the manufacturing method according to Examples 1 and 5 is smaller than that of the coating layer 200 according to Comparative Example 4, which is The improvement in crystallinity of the coating layer 200 of the semi-finished product obtained from the manufacturing method according to Examples 1 and 5 is more effective than that of the coating layer 200 according to Comparative Example 4, so that the coating layer 200 of the semi-finished product obtained from the manufacturing method according to Examples 1 and 5 It is a result that can confirm that the surface charge and specific surface area are larger.

In addition, it can be confirmed that the contact angle of the coating layer 200 of the semi-finished product obtained in the manufacturing method according to Example 1 is smaller than that of the coating layer 200 according to Comparative Example 5. This result confirms that the specific surface area is reduced.

6a to 6d, the surface of the coating layer 200 of the semi-finished product obtained by the manufacturing method according to Comparative Example 5 is relatively higher than that of the coating layer 200 of the semi-finished product obtained by the manufacturing method according to Examples 1 and 5 and Comparative Example 4. It can be confirmed that the semi-finished product is smooth, which means that when the heat treatment temperature of the semi-finished product is too high, the specific surface area of the coating layer 200 is reduced because the pores of the coating layer 200 are filled by the crystal grain growth of the ferritic magnetostrictive material included in the coating layer 200. This is a verifiable result.

<Test Example 4>

In Test Example 4, the semi-finished product obtained from (3) heat treatment of the semi-finished product of the manufacturing method according to Example 1 was analyzed using a focused ion beam electron microscope/energy dispersive spectrometer (FIB-SEM/EDS, model name: Scios2, manufacturer: Thermo Fisher Scientific). and analyzed.

Fig. 7 shows the results of analyzing the semi-finished product obtained in (3) heat treatment of the semi-finished product of the manufacturing method according to Example 1 using a focused ion beam electron microscope/energy dispersive spectrometer.

Referring to FIG. 7 , it can be seen that the semi-finished product has a three-layer structure. Considering both the focused ion beam electron microscope analysis result and the energy dispersive spectrometer measurement result, the aforementioned three-layer structure is the magnetostrictive layer 100 and the oxide layer 400. ) and the coating layer 200.

This is a result confirming that an oxide layer 400 is formed between the magnetostrictive layer 100 and the coating layer 200 when the semi-finished product is heat-treated.

<Test Example 5>

In Test Example 5, infrared spectroscopic analysis, X-ray diffraction analysis, differential scanning calorimetry, and thermogravimetric analysis were performed on the magnetoelectric composite 10 prepared according to Example 1, Example 6, and Comparative Example 6, and the analysis results were The beta phase fraction and crystallinity of the piezoelectric layer 300 included in the magnetoelectric composite 10 manufactured according to Examples 1 and 6 and Comparative Example 6 were calculated using the graph.

In Test Example 5, an infrared spectrometer (model name: Nicolet-380, manufacturer: Thermo Scientific Ltd) was used for infrared spectroscopic analysis, and an X-ray diffraction analyzer (model name: MiniFlex600, manufacturer: Rigaku) was used for X-ray diffraction analysis. did

In addition, in Test Example 5, differential scanning calorimetry was performed using a differential scanning calorimetry analyzer (model name: Q 10, manufacturer: TA Instrument Inc.), and thermogravimetric analysis was performed using a thermogravimetric analyzer (model name: SETSYS Evolution TGA-DTA, manufactured by TA Instrument Inc.). Company: SETARAM Instrumentation) was used.

When performing X-ray diffraction analysis in Test Example 5, X-ray diffraction analysis of magnetoelectric composites 10 prepared according to Examples 1, 6, and Comparative Example 6, as well as heat treatment of (3) semi-finished products of Example 1 X-ray diffraction analysis of the semi-finished product obtained from was also performed.

8 is a view showing the results of infrared spectroscopy analysis according to Test Example 5;

In more detail, FIG. 8 shows an infrared spectroscopic analysis result 710 of the magnetoelectric composite 10 manufactured according to Example 1 according to Test Example 5 and an infrared ray of the magnetoelectric composite 10 manufactured according to Example 6. It is a diagram showing the spectroscopic analysis result 720 and the infrared spectroscopic analysis result 730 of the magnetoelectric composite 10 prepared according to Comparative Example 6.

9 is a view showing the results of X-ray diffraction analysis according to Test Example 5.

9 shows the X-ray diffraction analysis result 810 of the magnetoelectric composite 10 prepared according to Example 1 and the X-ray diffraction analysis result 820 of the magnetoelectric composite 10 prepared according to Example 6. , X-ray diffraction analysis result 830 according to Test Example 5 of the magnetoelectric composite 10 prepared according to Comparative Example 6 and X-ray according to Test Example 5 of the semi-finished product obtained in (3) heat treatment of the semi-finished product of Example 1 It is a diagram showing the diffraction analysis result 840.

On the other hand, the piezoelectric layer 300 prepared according to Examples 1 and 6 and Comparative Example 6 contains polyvinylidene fluoride as a piezoelectric material, so that the measurement results of infrared spectroscopy and X-ray diffraction analysis according to Test Example 5 Peaks corresponding to the alpha phase and the beta phase, which are crystal phases of polyvinylidene fluoride, may appear. Peak positions corresponding to the alpha and beta phases are shown in FIGS. 8 and 9 .

Referring to FIGS. 8 and 9 , it can be confirmed that all of the piezoelectric layers 300 of the magnetoelectric composite 10 prepared according to Examples 1 and 6 and Comparative Example 6 include a beta phase.

The fraction of the beta phase, F(β), was calculated by referring to the infrared spectroscopic analysis result according to Test Example 5 and Equation 1 below.

Here, κ _α is the absorption coefficient of the α phase, κ _β is the absorption coefficient of the β phase, A _α is the absorbance of the α phase, and A _β is the absorbance of the β phase.

The enthalpy of fusion measured by differential scanning calorimetry according to Test Example 5, the mass fraction of the piezoelectric layer 300 included in the magnetoelectric composite 10 measured by thermogravimetric analysis, and the degree of crystallization using Equation 2 below x _c Calculated.

Here, x _c is crystallinity, ΔH _f is the fusion enthalpy measured by differential scanning calorimetry of polyvinylidene fluoride, which is a piezoelectric material included in the piezoelectric layer 300, and f _p is thermogravimetric analysis. It is the mass fraction of the piezoelectric layer 300 included in the magnetoelectric composite 10 to be measured.

In addition, ΔH ⁰ _f is the enthalpy of polyvinylidene fluoride having a crystallinity of 100%, and it is known that the enthalpy of polyvinylidene fluoride having a crystallinity of 100% is 104.6 J/g.

In Table 3, the enthalpy of fusion measured by differential scanning calorimetry according to Test Example 5, the mass fraction of the piezoelectric layer 300 measured by thermogravimetric analysis, the beta phase fraction calculated by Equation 1, and Equation 2 The crystallinity calculated by

Example 1 Example 5 Comparative Example 6 Beta phase fraction (%) 91.7 75.8 50.5 Mass fraction of the piezoelectric layer 0.053 0.030 0.016 Enthalpy of fusion (J/g) 3.230 1.208 0.6303 Crystallinity (%) 58.32 38.53 37.70

Referring to Table 3, it can be seen that the beta phase fraction and crystallinity of the piezoelectric layer 300 of the magnetoelectric composite 10 prepared according to Comparative Example 6 are the lowest, indicating that the concentration of the piezoelectric material in the piezoelectric solution is too low. If the piezoelectric solution heating step (S430), when the piezoelectric solution is heated, the evaporation of the second solvent occurs too quickly, confirming that the aligned polarization induction of the piezoelectric material does not occur sufficiently.

<Test Example 6>

In Test Example 6, infrared spectroscopic analysis, differential scanning calorimetry, and thermogravimetric analysis were performed on the magnetoelectric composite 10 prepared according to Examples 1 to 4 and Comparative Examples 1 to 3, and using the analysis results, Example 1 The beta phase fraction and crystallinity of the piezoelectric layer 300 included in the magnetoelectric composite 10 prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were calculated.

The beta phase fraction of the piezoelectric layer 300 included in the magnetoelectric composite 10 prepared according to Examples 1 to 4 and Comparative Examples 1 to 3 was obtained by using the infrared spectroscopic analysis result according to Test Example 6 and Equation 1 Calculated.

In Test Example 6, an infrared spectrometer (model name: Nicolet-380, manufacturer: Thermo Scientific Ltd) was used for infrared spectroscopic analysis, and differential scanning calorimetry was performed using a differential scanning calorimetry analyzer (model name: Q 10, manufacturer: TA Instrument Inc.) .) was used, and for thermogravimetric analysis, a thermogravimetric analyzer (model name: SETSYS Evolution TGA-DTA, manufacturer: SETARAM Instrumentation) was used.

The crystallinity of the piezoelectric layer 300 included in the magnetoelectric composite 10 prepared according to Examples 1 to 4 and Comparative Examples 1 to 3 is measured by differential scanning calorimetry according to Test Example 6, enthalpy of fusion, thermogravimetric The mass fraction of the piezoelectric layer 300 included in the magnetoelectric composite 10 measured by analysis and was calculated using Equation 2.

Melting enthalpy measured by differential scanning calorimetry according to Test Example 6, the mass fraction of the piezoelectric layer 300 measured by thermogravimetric analysis, the beta phase fraction calculated by Equation 1, and the calculated by Equation 2 Crystallinity is summarized in Table 4 below.

Beta phase fraction (%) Enthalpy of fusion (J/g) Mass fraction of the piezoelectric layer Crystallinity (%) Example 1 91.7 3.230 0.053 58.32 Example 2 88.4 6.585 0.111 56.77 Example 3 91.3 3.238 0.042 73.78 Example 4 80.3 5.898 0.123 45.96 Comparative Example 1 70.9 5.720 0.141 38.82 Comparative Example 2 83.0 1.910 0.049 37.30 Comparative Example 3 63.0 2.413 0.132 17.49

Referring to Table 4, the beta phase fraction and crystallinity of the piezoelectric layer 300 of the magnetoelectric composite 10 according to Examples 1 and 2 are the piezoelectric layer of the magnetoelectric composite 10 according to Comparative Example 1 ( 300), it can be seen that when the coating layer 200 is coated with a piezoelectric solution, if the thickness is too thick, the induction of aligned polarization of the piezoelectric layer 300 by the coating layer 200 is not smoothly performed. is a possible result.

In addition, the beta phase fraction and crystallinity of the piezoelectric layer 300 of the magnetoelectric composite 10 according to Examples 1 and 3 are higher than those of the piezoelectric layer 300 of the magnetoelectric composite 10 according to Comparative Example 2. It can be seen that if the heat treatment temperature of the piezoelectric solution is too high, the evaporation rate of the second solvent included in the piezoelectric solution is too fast, so that the evaporation of the second solvent is completed before the aligned polarization state of the piezoelectric material is sufficiently induced, resulting in the formation of a piezoelectric material. This result confirms that the aligned polarization state is not sufficiently induced.

<Test Example 7>

In Test Example 7, the thickness of the piezoelectric layer 300 of the magnetoelectric composite 10 manufactured according to Examples 1 to 4 and Comparative Examples 1 to 3 was measured.

The thickness measurement results are summarized in Table 4 below.

Piezoelectric layer thickness (㎛) Example 1 26 Example 2 31 Example 3 22 Example 4 33 Comparative Example 1 54 Comparative Example 2 20 Comparative Example 3 32

Referring to Table 5, it can be seen that the thickness of the piezoelectric solution applied on the coating layer 200 and the thickness of the formed piezoelectric layer 300 are almost proportional.

<Test Example 8>

In Test Example 8, a magnetoelectric output voltage generated by applying a magnetic field to the magnetoelectric composite 10 manufactured according to Examples 1 and 2 and Comparative Example 1 was measured.

In Test Example 8, the magnetic field application method applies a bias magnetic field to the magnetoelectric composite 10 according to Examples 1 and 2 and Comparative Example 1, but the DC magnetic field is fixed in a state where the AC magnetic field and the non-resonant frequency are fixed at 1 Oe and 1 kHz, respectively. The intensity of was varied from -1000 to 1000 Oe.

10A, 10B, and 10C are graphs illustrating magnetoelectric output voltages generated when a bias magnetic field is applied to the magnetoelectric composites according to Examples 1 to 2 and Comparative Example 1;

Referring to FIGS. 10A to 10C , the maximum value of the intensity of the magnetoelectric output voltage of the magnetoelectric composite 10 according to Examples 1 to 2 and Comparative Example 1 is summarized in Table 6 below.

Example 1 Example 2 Comparative Example 1 Output voltage (㎶/cm·Oe) 1230.6 467.9 375.3

Referring to FIGS. 10A to 10C and Table 6, it can be confirmed that the output voltage of the magnetoelectric composite 10 according to Examples 1 and 2 is higher than the output voltage of the magnetoelectric composite 10 according to Comparative Example 1. can

This is because when the piezoelectric solution is applied on the coating layer 200 of the semi-finished product, if the thickness of the piezoelectric solution applied is too thick, it is relatively far from the surface of the coating layer 200 in the applied piezoelectric solution, resulting in an electrostatic interaction with the coating layer 200. This part may occur, and the piezoelectric material included in the part where the electrostatic interaction with the coating layer 200 does not effectively occur in the applied piezoelectric solution does not effectively induce an ordered polarization state, so that the piezoelectric layer 300 This result confirms that the piezoelectricity of

That is, when the magnetoelectric composite 10 is manufactured, if the thickness of the piezoelectric solution applied on the coating layer 200 is thick, the piezoelectricity of the piezoelectric layer 300 deteriorates, and thus the magnetoelectric properties of the magnetoelectric composite 10 manufactured. It is the result that can confirm this fall.

10A to 10C, the slope of the magnetoelectric output voltage curve of the magnetoelectric composite 10 according to Examples 1 and 2 and Comparative Example 1 is in the vicinity of a direct current magnetic field of 0Oe, more specifically in the range of -90 to 90Oe. It can be confirmed that it increases in , and it can be seen that the maximum value of the magnetoelectric output voltage appears in the vicinity of the DC magnetic field 0Oe, more specifically in the range of -30 to 30Oe.

This is a result confirming that the magnetoelectric composite 10 according to Examples 1 and 2 and Comparative Example 1 has a self-bias characteristic capable of obtaining a magnetoelectric output voltage even when a DC magnetic field is not applied.

Those skilled in the art to which the present invention pertains will understand that the present invention can be embodied in other specific forms without changing its technical spirit or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. The scope of the present invention is indicated by the claims to be described later rather than the detailed description above, and all changes or modifications derived from the scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention.

10: magnetoelectric complex,
100: magnetostrictive layer, 200: coating layer, 300: piezoelectric layer, 400: oxide layer,
S100: magnetostrictive layer preparation step,
S200: Semi-finished product manufacturing step,
S210: preparing a magnetostrictive solution, S220: applying a magnetostrictive solution,
S300: heat treatment step,
S400: piezoelectric layer forming step,
S410: piezoelectric solution preparation step,
S420: piezoelectric solution application step,
S430: piezoelectric solution heating step.

Claims (12)

preparing a magnetostrictive layer;
manufacturing a semi-finished product by applying a magnetostrictive solution containing a ferrite magnetostrictive material and a first solvent on the magnetostrictive layer to form a coating layer;
heat-treating the semi-finished product to increase the surface charge and specific surface area of the coating layer; and
Forming a piezoelectric layer while inducing aligned polarization of the piezoelectric material by applying a piezoelectric solution containing a piezoelectric material on the coating layer and heat-treating the applied piezoelectric solution
A method for preparing a phosphorus magnetoelectric composite. The method of claim 1 , wherein forming the piezoelectric layer comprises
preparing the piezoelectric solution having a concentration of the piezoelectric material greater than 5 and less than 10wt% by mixing the piezoelectric material and the second solvent;
applying the piezoelectric solution to a thickness of 200 or more and less than 400 μm on the coating layer; and
Forming the piezoelectric layer having a thickness of 15 or more and less than 60 μm by heat-treating the piezoelectric solution applied on the coating layer and the coating layer at 50 or more and less than 110 ° C.
A method for preparing a phosphorus magnetoelectric composite. The method of claim 1, wherein the step of heat-treating the semi-finished product
heat-treating the semi-finished product at more than 400 and less than 700 ° C so that the contact angle of the coating layer is 1 to 40 °;
A method for preparing a phosphorus magnetoelectric composite. The method of claim 1, wherein the step of heat-treating the semi-finished product,
Heat-treating the semi-finished product at more than 400 and less than 700 ° C to oxidize the magnetostrictive layer to form an oxide layer having antiferromagnetism between the magnetostrictive layer and the coating layer;
A method for preparing a phosphorus magnetoelectric composite. According to claim 1,
Manufacturing a magnetoelectric composite having a maximum magnetoelectric output voltage of 350 to 1250 ㎶/cm Oe measured under the conditions of AC magnetic field 1Oe, DC magnetic field -1000 to 1000Oe, and frequency 1kHz
A method for preparing a phosphorus magnetoelectric composite. 3. The method of claim 2, wherein preparing the piezoelectric solution comprises
The piezoelectric material including at least one selected from polyvinylidene fluoride, polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene and triglycine sulfate and dimethylformamide, acetone, dimethyl Preparing a piezoelectric solution by mixing the second solvent containing at least one selected from sulfoxide, N-methylpyrrolidone, methylethylketone, dimethylacetamide, tetrahydrofuran, hexamethylphosphoramide and triethylphosphate step to do
A method for preparing a phosphorus magnetoelectric composite. According to claim 1,
The ferritic magnetostrictive material has a form of AFe ₂ O ₄ ,
Wherein A is at least one selected from Co, Fe, Mn, Ni and Zn
A method for preparing a phosphorus magnetoelectric composite. According to claim 1,
The first solvent includes at least one selected from water and alcohol
A method for preparing a phosphorus magnetoelectric composite. The method of claim 1 , wherein forming the magnetostrictive layer comprises
Preparing the magnetostrictive layer containing at least one selected from ferromagnetic metals, ferritic ceramics, magnetostrictive alloys and magnetic shape memory alloys
A method for preparing a phosphorus magnetoelectric composite. magnetostrictive layer;
a coating layer formed on the magnetostrictive layer, including a ferrite magnetostrictive material, and having a contact angle of 1 to 40°; and
A piezoelectric layer formed on the coating layer and including a piezoelectric material in which aligned polarization is induced by the surface charge of the coating layer;
phosphorus magnetoelectric complex. According to claim 10,
The maximum value of the magnetoelectric output voltage measured under the conditions of AC magnetic field 1Oe, DC magnetic field -1000 to 1000Oe, and frequency 1kHz is 350 to 1250 ㎶/cm Oe
phosphorus magnetoelectric complex. According to claim 10,
Further comprising an oxide layer formed between the magnetostrictive layer and the coating layer as the magnetostrictive layer is oxidized.
phosphorus magnetoelectric complex.

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