KR20100090326A - Multiferroic structure and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A multiferroic structure and a method for manufacturing the same are provided to combine a ferromagnetic composition and a ferroelectric composition by inserting a buffer between the compositions. CONSTITUTION: A first layer is composed of ferroelectric composition(2). A second layer is composed of ferromagnetic composition(3). One or more first layers and one or more second layers are alternately stacked to form a multiferroic structure. A buffer layer(4) is inserted between the first layers and the second layers. The ferromagnetic composition and the ferroelectric composition are mixed to form the buffer layer.

Description

MULTIFERROIC STRUCTURE AND MANUFACTURING METHOD THEREOF

The present invention relates to a multi-rigid structure and a method of manufacturing the same, in particular, the multi-rigid structure according to the present invention is laminated at least one ferroelectric layer consisting of a ferroelectric composition and at least one ferromagnetic layer consisting of a ferromagnetic composition, each of these ferroelectric A buffer layer, which is a mixture of the ferroelectric composition and the ferromagnetic composition, is inserted between the layers and the ferromagnetic layers, respectively.

Recently, multiferroic materials, which have been studied, have both ferroelectric and ferromagnetic properties, so they can be used as new electronic devices that could not be predicted by the prior art, which realized the device with only one property. It is estimated to be able.

In more detail, these multi-rigid materials simultaneously exhibit at least two or more of the following properties: ferroelectric, antiferroelectric, ferromagnetic, antiferromagnetic, ferroelastic, etc. Therefore, they interact with magnetic, electrical or structural order parameters. For example, a multi-rigid material having both ferroelectric and ferromagnetic properties can control charge and spin with an electric field and a magnetic field, so that when implemented as a memory device, it is possible to read and write simultaneously with magnetism and electricity, and to increase the degree of integration. Can be.

However, research on multi-rigid materials is still in its infancy and is being approached from an academic point of view, and is not yet developed in terms of use or product implementation. Thin film rigid materials have applications in magnetoelectric devices, spintronics, information storage, and multiple-state memories. Multi-rigid materials (including composites) include actuators, magnetic sensors (ac / dc magnetic field sensors, current sensors), transformers, gyrators, microwave devices: Applications for tunable devices, resonators, and filters are being explored.

Accordingly, an object of the present invention is to provide a multi-rigid structure having a ferroelectric and ferromagnetic properties by including at least one ferroelectric layer and a ferromagnetic layer and a method of manufacturing the same.

In order to achieve the above object, in the multi-rigid structure according to an aspect of the present invention, at least one or more first layers made of ferroelectrics and at least one or more second layers made of ferromagnetic materials are alternately laminated, and these first layers and second A buffer layer having a composition in which the ferroelectric material and the ferromagnetic material are mixed may be inserted between the layers. At this time, the ferroelectric is (Ba _x Sr _{1 -x} ) TiO ₃ (At this time 0 <x≤1) ceramics, (Pb _x Sr _{1 -x} ) (Zr _y Ti _{1 -y} ) O ₃ (where 0 <x≤1 and 0 <y <1) ceramics, (Pb _x RE _{1 -x} ) TiO ₃ Where RE is rare earth and 0 <x≤1) ceramics, Pb (Mg _x Nb _{1- x} ) O ₃ (where 0 <x <1) ceramics and ANbO _{3 where} A is Na, K, Li It may include one or more selected from the group consisting of alkaline element) ceramics. In addition, the ferromagnetic material may include one or more selected from the group consisting of Ni ferrite, NiZn ferrite and Co ferrite. In addition, the ferroelectric in the composition of the buffer layer may be mixed at 50-70wt% relative to the total composition.

In addition, the method of manufacturing a multi-rigid structure according to another aspect of the present invention synthesizes a ferroelectric powder, a ferromagnetic powder and a buffer powder, respectively, wherein the buffer powder is formed by mixing the ferroelectric powder and ferromagnetic powder, and Preparing a ferroelectric paste, a ferromagnetic paste, and a buffer paste by mixing ferroelectric powder, ferromagnetic powder, and buffer powder with at least one selected from the group consisting of a polymer, a dispersant, and a plasticizer, respectively, and the ferroelectric paste, the buffer paste, and the ferromagnetic material. Alternately stacking the ferroelectric film, the buffer film, and the ferromagnetic film, each of which is formed by tape-casting the pastes in turn, and repeating at least one or more times to form a laminated structure, and forming and firing the laminated structure. Can be configured. At this time, in order to control the shrinkage during firing, etc., only the composition of the ferroelectric film is SiO ₂ , LiF, Li ₂ CO ₃ And one or more sintering aids selected from the group consisting of BN, and the sintering aids may be added in an amount greater than 0 wt% and less than or equal to 1 wt% based on the total composition of the ferroelectric. As a result, the firing temperature may be 930-1400 ° C. In addition, the calcination may be a reducing atmosphere such as a nitrogen atmosphere to which 10% hydrogen gas is added.

According to the present invention as described above, in a multi-rigid structure having both ferroelectric and ferromagnetic properties, the ferroelectric composition and the ferromagnetic composition are heterojunction therebetween, and a buffer, which is a mixture of the ferroelectric composition and the ferromagnetic composition, is inserted therebetween. Since materials diffuse at high temperatures, the bonding of the two compositions becomes easier and more robust, and other materials other than the two materials are not added, thereby achieving excellent characteristics without obstacles.

Hereinafter, the present invention will be described in detail.

The multi-rigid structure according to the present invention is based on a structure in which the ferroelectric composition and the ferromagnetic composition are heterojunction as magnetoelectric composites, between which a buffer which is a mixture of the ferroelectric composition and the ferromagnetic composition is inserted. Such a multi-rigid structure has both ferroelectric and ferromagnetic properties.

1A is a schematic structural diagram of a multi-rigid structure according to the present invention, and FIG. 1B is an enlarged view of portion “A” of FIG. 1A.

Referring to FIGS. 1A and 1B, a multi-rigid structure 1 according to the present invention includes at least one ferroelectric layer 2 made of a ferroelectric composition and at least one ferromagnetic layer 3 made of a ferromagnetic composition. A buffer layer 4, which is a mixture of the ferroelectric composition and the ferromagnetic composition, is inserted between each layer and the ferromagnetic layer. In addition, as an input / output terminal for driving the multi-rigid structure 1 element, an electrode 6 such as Ag is coated on the top and back surfaces thereof.

At this time, the ferroelectric layer (2) is a ferroelectric ceramic composition, the composition is (Ba _x Sr _1-x ) TiO ₃ (where 0 <x≤1) ceramics, (Pb _x Sr _{1 -x} ) (Zr _y Ti _{1 -y} ) O ₃ (where 0 <x≤1 and 0 <y <1) ceramics, (Pb _x RE _{1 -x} ) TiO ₃ (Where RE denotes rare earth, 0 <x≤1) ceramics, Pb (Mg _x Nb _{1- x} ) O ₃ (where 0 <x <1) ceramics, ANbO ₃ (where A is Na, K, Alkali element containing Li) and at least one selected from the group consisting of ceramics.

In addition, the ferromagnetic layer 3 is a ferromagnetic ceramic composition, the composition is Ni ferrite containing NiFe ₂ O ₄ , Ni _{1 - x} Zn _x Fe ₂ O ₄ (At this time, at least one selected from the group consisting of NiZn ferrite containing 0 <x≤1) and Co ferrite containing CoFe ₂ O ₄ .

In addition, the buffer layer 4 is a mixture of the ferroelectric ceramic composition of the ferroelectric layer 2 and the ferromagnetic ceramic composition of the ferromagnetic layer 3, thereby enabling simultaneous firing of two kinds of materials having different thermal expansion rates. . Without such a buffer layer, due to the difference in shrinkage between the ferroelectric ceramic composition and the ferromagnetic ceramic composition, bending behavior is severely caused or peeling occurs easily without bonding at the interface portion of the two materials. According to the present invention, when the buffer layer 4 is inserted between the ferroelectric layer 2 and the ferromagnetic layer 3, the materials of the buffer layer 4 diffuse at a high temperature, thereby making the bonding of the two materials easier and more robust. Since no substances other than the two substances are added, the characteristics are not hindered. In addition, in general, since the sintering temperature of the ferromagnetic ceramic composition is lower than that of the ferroelectric ceramic composition, the shrinkage rate during sintering is greater, and in consideration of this, the ferroelectric ceramic composition is preferably 50-70 wt%, and 50-55 wt%. More preferably. In addition, the thickness of the buffer layer 4 is preferably less than half of each thickness of the ferroelectric layer 2 or the ferromagnetic layer (3).

In general, the ferroelectric ceramic composition of the ferroelectric layer 2 and the ferromagnetic ceramic composition of the ferromagnetic layer 3 have a large difference in sintering temperature. For example, the sintering temperature of BaTiO ₃ , a ferroelectric ceramic, is 1400 ° C. or higher, and the sintering temperature of NiFe ₂ O ₄ , a ferromagnetic ceramic, is 1000 ° C. or higher. Therefore, in order to heterogeneously join these two materials, the shrinkage rate should be controlled by judging the flexural behavior and the sintering behavior. For this purpose, the shrinkage ratio of the X-axis and Y-axis is similarly controlled by lowering the sintering temperature of ferroelectric ceramics and controlling grain growth during sintering. It is important to keep. To this end, according to one embodiment of the present invention, a sintering aid may be added to the ferroelectric ceramic composition of the ferroelectric layer (2). The sintering aid may be one or more of SiO ₂ , LiF, Li ₂ CO ₃ , BN, and the like, and when Li or B is contained, the resistance may rapidly decrease even when a small amount is added, thereby making it difficult to control the polarization. Therefore, SiO ₂ is preferable, and the addition amount of the sintering aid is preferably 1% or less of the total. According to one embodiment, the sintering temperature of the heterojunction multi-rigid structure 1 according to the addition of this sintering aid is 930-1400 ℃, preferably 1200-1300 ℃. Further, according to another embodiment, the sintering process may be performed in a reducing atmosphere such as a nitrogen atmosphere in which hydrogen is added in order to control the shrinkage rate by suppressing coarsening of particles generated during sintering.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the examples described below are provided to help the overall understanding of the present invention, and the present invention is not limited only to the following examples.

Example

First, barium carbonate (BaCO ₃ ) and titanium oxide (TiO ₂ ) were mixed in a 1: 1 molar ratio, and then synthesized as BaTiO ₃ through a calcination process at 1200 ° C. for 2 hours. The calcined BaTiO ₃ is mixed again by adding 1 wt% of SiO ₂ , and mixed with nickel oxide (NiO) and iron oxide (Fe ₂ O ₃ ) in a 1: 1 molar ratio, followed by calcination at 900 ° C. to NiFe ₂ O Synthesized as ₄ ;

In order to prepare the paste, 60 wt% of 100 wt% of the powder paste prepared by the above process (BTiO ₃ and NiFe ₂ O ₄ were mixed in a 1: 1 weight ratio for the buffer layer), and toluene and ethanol were 6: 4 weight ratio. The ball mixture was mixed with 33 wt% of solvent, 5 wt% of PVB as a polymer material for imparting viscosity of the paste, 0.5 wt% of SN as powder dispersant, and 1.5 wt% of DBP as a plasticizer for imparting plasticity. Mix. The prepared slurry was filtered using a 200mesh to remove bubbles to prepare a paste that can be applied to tape casting. In this way, a total of three kinds of pastes including the buffer layer were prepared.

The paste thus prepared was made into a film at a rate of 2 meters per minute through a continuously controlled tape caster up to 35-80 ° C., wherein the thickness of the film was a ferroelectric layer (2) and a ferromagnetic layer (3). For each case was prepared to 50㎛ and the buffer layer 4 was prepared to be 25㎛. At this time, the thickness of the ferroelectric layer (2) and the ferromagnetic material layer (3) may be 40-100㎛ considering the plasticity of the film, 50-60㎛ is preferred.

The prepared film was cut as much as desired and subjected to hydrostatic molding in the lamination order shown in FIG. 1A. The laminated sheet thus prepared was sintered at a temperature of 1200 ° C. for 2 hours in a nitrogen atmosphere to which 10% hydrogen gas was added to control the shrinkage rate by preventing coarsening of particles generated during sintering. Here, as a comparative specimen, it was produced by sintering at a temperature of 1200 ° C. in an oxygen atmosphere. The specimens after sintering were coated with silver electrodes on both sides, and then finished by electrode firing at a firing temperature of 600 ° C.

2 is an electron micrograph of a cross section of a multi-rigid structure manufactured according to an embodiment of the present invention. That is, it is NiFe ₂ O ₄ A buffer layer composed of a mixture of two components is inserted between the ferromagnetic layer and the BaTiO ₃ ferroelectric layer to have a multilayer chip structure manufactured through a simultaneous firing process.

3 shows the magnetoelectric voltage coefficient (α _E ) characteristics of the multi-rigid structure manufactured according to the embodiment of the present invention. Here, α ₃₃ represents the self-electric voltage coefficient α _{E in} the case where an electric field and a magnetic field are applied in a direction perpendicular to the structure specimen.

In the above-described embodiments and examples of the present invention, the powder characteristics such as the average particle size, distribution and specific surface area of the composition powder, and the purity of the raw material, the amount of impurity addition, and the sintering conditions vary slightly within the usual error range. It can be quite natural for one of ordinary skill in the art to be there.

In addition, preferred embodiments and embodiments of the present invention are disclosed for the purpose of illustration, anyone of ordinary skill in the art will be possible to various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications Changes, additions, and the like should be considered to be within the scope of the claims.

1A is a schematic structural diagram of a multi-rigid structure according to the present invention.

FIG. 1B is an enlarged view of portion “A” of FIG. 1A;

2 is an electron micrograph of a cross section of a multi-rigid structure manufactured according to an embodiment of the present invention.

3 is a graph showing the magnetoelectric voltage coefficient (α _E ) characteristics of the multi-rigid structure manufactured according to the embodiment of the present invention.

* Code descriptions for the main parts of the drawings

1: multi-rigid structure 2: ferroelectric layer

3: ferromagnetic layer (3) 4: buffer layer

6: electrode

Claims (15)

At least one or more first layers made of ferroelectrics and at least one or more second layers made of ferromagnetic materials are alternately stacked, and a buffer layer of a composition in which the ferroelectric and the ferromagnetic materials are mixed is inserted between the first and second layers. A multi-rigid structure, characterized in that. The method of claim 1, The ferroelectric is (Ba _x Sr _{1 -x} ) TiO ₃ (At this time 0 <x≤1) ceramics, (Pb _x Sr _{1 -x} ) (Zr _y Ti _{1 -y} ) O ₃ (where 0 <x≤1 and 0 <y <1) ceramics, (Pb _x RE _{1 -x} ) TiO ₃ (In this case, RE is a rare earth, and 0 <x≤1) ceramic, Pb (Mg _x Nb _{1 -x)} O ₃ (where, 0 <x <1) and the ceramic ANbO ₃ (where, A is an Na, K, Li Alkali element comprising) a multi-rigid structure comprising at least one selected from the group consisting of ceramics. The method of claim 1, The ferromagnetic material is a multi-rigid structure, characterized in that it comprises one or more selected from the group consisting of Ni ferrite, NiZn ferrite and Co ferrite. The method of claim 1, The ferroelectric in the composition of the buffer layer is a multi-rigid structure, characterized in that 50 to 70wt% of the total composition. The method of claim 1, Wherein the buffer layer has a thickness greater than zero and less than or equal to half the thickness of the first layer or the second layer. 6. The method according to claim 1 or 5, The thickness of the first layer or the second layer is a multi-rigid structure, characterized in that 40-100㎛. Synthesizing a ferroelectric powder, a ferromagnetic powder, and a buffer powder, respectively, wherein the buffer powder is formed by mixing the ferroelectric powder and the ferromagnetic powder; Preparing a ferroelectric paste, a ferromagnetic paste, and a buffer paste by mixing at least one selected from the group consisting of a polymer, a dispersant, and a plasticizer to the ferroelectric powder, the ferromagnetic powder, and the buffer powder, respectively; Alternately stacking the ferroelectric film, the buffer film, and the ferromagnetic film, each of which is formed by tape casting the ferroelectric paste, the buffer paste, and the ferromagnetic paste, respectively, and repeating at least one or more times to form a stacked structure; Forming and firing the laminated structure comprising the method of manufacturing a multi-rigid structure. The method of claim 7, wherein The ferroelectric powder is (Ba _x Sr _{1 -x} ) TiO ₃ (At this time 0 <x≤1) ceramics, (Pb _x Sr _{1- x} ) (Zr _y Ti _1-y ) O ₃ (where 0 <x≤1 and 0 <y <1) ceramics, (Pb _x RE _{1 -x} ) TiO ₃ Where RE is rare earth and 0 <x≤1) ceramics, Pb (Mg _x Nb _{1- x} ) O ₃ (where 0 <x <1) ceramics and ANbO _{3 where} A is Na, K, Li Alkali element comprising) a method for producing a multi-rigid structure, characterized in that the composition comprising at least one selected from the group consisting of ceramics. The method of claim 7, wherein The ferromagnetic powder is a method of producing a multi-rigid structure, characterized in that the composition containing one or more selected from the group consisting of Ni ferrite, NiZn ferrite and Co ferrite. The method of claim 7, wherein The ferroelectric powder in the composition of the buffer powder is a method for producing a multi-rigid structure, characterized in that the mixture of 50-70wt% relative to the total composition. The method of claim 7, wherein SiO ₂ , LiF, Li ₂ CO ₃ only in the composition of the ferroelectric film And at least one sintering aid selected from the group consisting of BN. The method of claim 11, The sintering aid is a method for producing a multi-rigid structure, characterized in that the addition of greater than 0wt% and less than 1wt% relative to the total composition of the ferroelectric. The method of claim 7, wherein The firing temperature is 930-1400 ℃ manufacturing method of a multi-rigid structure. The method of claim 7, wherein The firing is a method for producing a multi-rigid structure, characterized in that the reducing atmosphere. The method of claim 14, The reducing atmosphere is a method for producing a multi-rigid structure, characterized in that the nitrogen atmosphere is added to the hydrogen gas of 10%.

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