JP7392015B2 - Calcium lithium niobate dielectric composition without dielectric dispersion and method for producing the same - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act March 8, 2021 Website https://doi. org/10.1016/j. ceramint. Published on 2021.03.046

The present specification relates to a calcium lithium niobate dielectric composition having high dielectric constant and low dielectric loss characteristics over a wide frequency range, and a method for manufacturing the same.

In recent years, electronic components such as duplexers for cordless telephones and mobile communication terminals, band pass filters, multilayer circuit boards, microwave band resonators and filters, and thin film transistors for computers, and multilayer ceramics. As capacitors (MLCCs, multilayer ceramic capacitors) become more integrated and ultra-miniaturized, the dielectric materials used therein are also required to be more compact, have higher performance, and be more stable. Furthermore, research is progressing to find new materials that can exhibit fine and stable properties in line with the trends toward integration, flexibility, and ultra-light weight reduction.

Recently, oxide nanosheets have attracted attention because they can be easily manufactured in various compositions and structures and exhibit useful properties suitable for electronic devices. In particular, attempts have been made to fabricate dielectric thin films using perovskite nanosheets having niobic acid octahedrons. The layered nanosheet exhibits properties unique to nanosheets by converting the various properties exhibited by the compounds of the parent composition into even better properties. Various perovskite materials such as KCaNbO, KTiNbO, KLaNbO, and KCaNaNbO have been reported as parent compositions of nanosheet materials suitable for next-generation devices.

Furthermore, in order to realize MLCC etc., it is essential to increase the area of the internal electrodes that determine the capacitance of the dielectric and to reduce the thickness of the electrodes and the dielectric. There is a big limit to reducing the thickness of. As a dielectric material for MLCCs, titanium oxides such as BaTiO ₃ , SrTiO ₃ , CaTiO ₃ , or combinations thereof, which have a high dielectric constant, are mainly used. However, in the case of such a titanium oxide dielectric material, since it is synthesized with spherical particles, according to the existing technology for forming a dielectric film, the substrate interface is The problems of deterioration of the composition, deviation of the composition, and having many grain boundaries cause non-linear electric property (ΔC/C ₀ ) and high dielectric loss. Furthermore, when the dielectric layer is thinned to about 1 to 3 μm, the insulation properties and durability under high-temperature loads deteriorate, leading to a decrease in reliability. It is difficult to apply this method to nano-thickness level MLCC, which aims at

In addition, thinner films and higher laminations can be achieved through the screen printing method (a process in which electrode paste is printed on a sheet, laminated in multiple layers, cut, and then sintered at high temperature), which synthesizes existing dielectric materials to create MLCC structural units. However, there are limits to achieving miniaturization. Therefore, in order to realize MLCCs that can be applied to next-generation devices, we need not only dielectric nanosheets that have stable properties even in nano-thickness level thin films, but also nanosheets that have various properties that can be used in a wide frequency range. There is an emerging need for research and development of host materials for perovskite layered structures that exhibit stable dielectric properties and have diverse compositions.

In order to solve these problems, embodiments of the present invention provide a dielectric composition having dielectric properties of high dielectric constant and low dielectric loss.

In addition, when producing layered starting particles in a non-spherical sheet form, not only can grain boundaries be reduced as much as possible, but also when using a crystalline sheet, a heat treatment process is no longer necessary, which reduces the problem of deterioration between the substrate and dielectric material. Its purpose is to solve the problem.

Furthermore, it is an object of the present invention to provide a novel material that can be used in various types of electronic devices such as multilayer ceramic capacitors, tunable elements, and gates for transistors, and can replace conventional materials.

In order to achieve the above object, an embodiment of the present invention provides a calcium lithium niobate dielectric composition including a calcium lithium niobate dielectric having a composition represented by Formula 1.

[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)
Further, a calcium lithium niobate dielectric comprising: a calcium lithium niobate dielectric having a composition represented by chemical formula 2, in which the K ⁺ ions of the calcium lithium niobate dielectric composition described above are cationically substituted with H ⁺ ions; Provides body composition.

[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)
In one embodiment, the calcium lithium niobate dielectric having the composition represented by Formula 2 may have a layered structure in which plate-shaped particles are stacked.

Further, there is provided a calcium lithium niobate dielectric composition comprising: a calcium lithium niobate dielectric having a composition represented by chemical formula 3, from which the H ⁺ ions of the above-described calcium lithium niobate dielectric composition have been removed. .

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)
In one embodiment, the calcium lithium niobate dielectric having the composition represented by Formula 3 may have a nanosheet shape.

In one embodiment, the nanosheets may have an average diameter of 50 nm to 50 μm and a thickness of 10 nm or less.

In one embodiment, the calcium lithium niobate dielectric composition may have a dielectric constant of 100 or less and a dielectric loss of 0.25 or less in the frequency range of 10-10 ⁴ Hz.

In one embodiment, the calcium lithium niobate dielectric composition may have a dielectric constant of 90 or less and a dielectric loss of 0.02 or less in a frequency range of 10 ⁴ to 10 ⁸ .

In one embodiment of the present invention, a nanosheet thin film is provided in which a calcium lithium niobate dielectric having a composition represented by the above-mentioned chemical formula 3 is laminated.

The present invention also provides a capacitor, a tunable element, and a gate for a transistor, including the nanosheet thin film described above.

In another embodiment of the present invention, mixing and calcining a potassium precursor, a calcium precursor, a lithium precursor, and a niobium oxide to form a dielectric having a composition represented by Formula 1; A method of manufacturing a calcium lithium niobate dielectric composition is provided.

[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
In one embodiment, stirring the dielectric represented by Formula 1 with an acidic solution to cationically replace K ⁺ ions with H ⁺ ions to form a dielectric having a composition represented by Formula 2; may further include.

[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
In one embodiment, the method may further include stirring the dielectric material represented by Chemical Formula 2 with a hydroxide solution to form a dielectric material having a composition represented by Chemical Formula 3.

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
In one embodiment, the dielectric having the composition represented by Chemical Formula 3 may have a nanosheet shape from which a bulk dielectric having the composition represented by Chemical Formula 2 has been peeled off.

In one embodiment, the calcination may be performed at a temperature range of 800 to 1200°C.

In one embodiment, the formed dielectric having the composition represented by Formula 1 may be sintered at 1100-1150° C. in an air atmosphere.

In one embodiment, the hydroxide solution includes tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide (TEAOH), and tetramethylammonium hydroxide (TMAOH). ) may be one or more solutions selected from the group consisting of:

In another embodiment of the present invention, there is provided a method for manufacturing a nanosheet thin film, which comprises forming a nanosheet thin film using an electrophoresis method or a Langmuir-Blodgett method using a nanosheet-like dielectric material having a composition represented by chemical formula 3. .

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)

The calcium lithium niobate dielectric composition according to the present invention has the characteristics of a high dielectric constant and low dielectric loss, and also has a linear and excellent dielectric constant even at nano-level thickness, and can realize insulation properties. It is possible to provide a nanosheet-like dielectric material that can be applied to the production of low-temperature devices. Further, by producing the starting particles in a non-spherical sheet shape, not only can grain boundaries be reduced as much as possible, but also there is an advantage that a heat treatment step is not required when using a crystalline sheet.

Furthermore, since the vacuum equipment and expensive vapor deposition equipment required in the conventional dielectric element manufacturing process are not required, it is possible to design an element manufacturing process that satisfies low cost and early manufacturing time.

Furthermore, the size of the nanosheets can be adjusted according to the synthesis conditions of the calcium lithium niobate dielectric, providing a technology that can synthesize nanosheets with a size that suits the application, and creating more uniform thin films when applied to devices. Provide a way to do so.

Therefore, it is possible to solve the problem of deterioration between the substrate and the dielectric material that occurred in the conventional device manufacturing process, and to solve the problem of deterioration between the substrate and the dielectric material that occurred in the conventional device manufacturing process. It can be applied to a wide range of fields of information equipment.

FIG. 3 is a diagram showing X-ray diffraction analysis characteristics of KCa ₂ LiNb ₄ O ₁₃ samples synthesized at various temperatures in Examples according to the present invention. Scanning electron microscopy (SEM) of KCa ₂ LiNb ₄ O ₁₃ samples produced at sintering temperatures of 1100 °C (Fig. 2a), 1125 °C (Fig. 2b), and 1150 °C (Fig. 2c), respectively, in an example according to the invention. It is a diagram showing a photograph. Scanning electron microscopy (SEM) of KCa ₂ LiNb ₄ O ₁₃ samples produced at sintering temperatures of 1100 °C (Fig. 2a), 1125 °C (Fig. 2b), and 1150 °C (Fig. 2c), respectively, in an example according to the invention. It is a diagram showing a photograph. Scanning electron microscopy (SEM) of KCa ₂ LiNb ₄ O ₁₃ samples produced at sintering temperatures of 1100 °C (Fig. 2a), 1125 °C (Fig. 2b), and 1150 °C (Fig. 2c), respectively, in an example according to the invention. It is a diagram showing a photograph. 1 is a diagram showing a transmission electron microscope (TEM) photograph of KCa ₂ LiNb ₄ O ₁₃ in an example according to the present invention. FIG. 3 is a diagram showing the dielectric constant value of KCa ₂ LiNb ₄ O ₁₃ in an example according to the present invention. FIG. 3 is a diagram showing the dielectric loss value of KCa ₂ LiNb ₄ O ₁₃ in an example according to the present invention. FIG. 3 is a diagram showing a comparison of the dielectric properties of KCa ₂ LiNb ₄ O ₁₃ due to Li insertion and stability according to frequency changes in an example according to the present invention. FIG. 3 is a diagram showing a comparison of the dielectric properties of KCa ₂ LiNb ₄ O ₁₃ due to Li insertion and stability according to frequency changes in an example according to the present invention. FIG. 3 is a diagram showing an AFM photograph of Ca ₂ LiNb ₄ O ₁₃ nanosheets in an example according to the present invention. FIG. 3 is a diagram showing an AFM photograph of Ca ₂ LiNb ₄ O ₁₃ nanosheets in an example according to the present invention.

[Specific details for carrying out the invention]
Hereinafter, embodiments of the present invention will be described in more detail.

The embodiments of the invention disclosed herein are merely illustrative for purposes of illustration, and embodiments of the invention may be implemented in a variety of forms and may be implemented in a variety of forms. It should not be construed as being limited to the examples.

The present invention may be subject to various changes and may take various forms; however, the examples are not intended to limit the present invention to a specific disclosed form, but rather include various modifications within the spirit and technical scope of the present invention. It should be understood that it includes all modifications, equivalents and substitutions.

A singular expression includes a plural expression unless the context clearly dictates otherwise. In this application, terms such as "comprising" or "having" are used to specify the presence of a feature, number, step, act, component, part, or combination thereof described in the specification. Items used to exclude in advance the existence or possibility of addition of one or more other features, numbers, steps, operations, components, parts, or combinations of these. It should be understood that this is not the case.

In the embodiment of the present invention, a double-layer perovskite is fabricated based on the fact that as the number of perovskite structure layers including a niobic acid layer increases, the dielectric property becomes higher and even a nano-level thin film can be applied as a dielectric nanomaterial. A material with dielectric properties represented by the general formula KCa ₂ LiNb ₄ O ₁₃ (KCLNO) can be efficiently produced by synthesizing a KCa ₂ Nb ₃ O ₁₀ ceramic composition with a single perovskite structure and LiNbO ₃ with a single perovskite structure. The compound was synthesized after conducting various studies regarding its production.

Calcium Lithium Niobate Dielectric Composition To achieve the above-mentioned objects, in one embodiment of the present invention, a calcium lithium niobate dielectric composition having a composition represented by Formula 1 (KCLNO); A calcium lithium dielectric composition is provided.

[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
Further, a calcium lithium niobate dielectric having a composition represented by chemical formula 2 (HCLNO) in which the K ⁺ ions of the calcium lithium niobate dielectric composition described above are cationically substituted with H ⁺ ions; A calcium lithium dielectric composition is provided.

[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
In one embodiment, the calcium lithium niobate dielectric having the composition represented by Formula 2 may have a layered structure in which plate-shaped particles are stacked. For example, it may have a stacked layered structure with four unit cells per layer. Specifically, the calcium lithium niobate dielectric may have four aggregate layers formed by additional synthesis using Li insertion. On the other hand, in the case of a niobic acid dielectric without Li inserted therein, for example, KCa ₂ Nb ₃ O ₁₀ , there are only three assembled layers of octahedral unit cells in a perovskite structure, and it may have other layered structures. Due to the difference in the layered structure, the dielectric constant increases, the dielectric loss decreases, and the dispersion of the dielectric constant depending on the frequency is small.

Further, a calcium lithium niobate dielectric composition comprising: a calcium lithium niobate dielectric having a composition represented by chemical formula 3 (CLNO) from which the H ⁺ ions of the above-described calcium lithium niobate dielectric composition have been removed; I will provide a.

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)
In one embodiment, the calcium lithium niobate dielectric having the composition represented by Formula 3 may have a nanosheet shape.

In one embodiment, the nanosheets may have an average diameter of 50 nm to 50 μm and a thickness of 10 nm or less. When the nanosheet has the above average diameter and thickness range, it may have high dielectric properties and excellent stability in response to frequency changes.

In one embodiment, the calcium lithium niobate dielectric composition may have a dielectric constant of 100 or less and a dielectric loss of 0.25 or less in the frequency range of 10-10 ⁸ Hz. For example, it may have a dielectric constant of 90 or less and a dielectric loss of 0.02 or less in the frequency range of 10 ⁴ to 10 ⁸ Hz. Meanwhile, the calcium lithium niobate dielectric may have a dielectric constant and a dielectric loss that change according to a change in frequency. That is, it may have a characteristic that the dispersion of these values depending on the frequency is small. For example, in the frequency range of 10 ³ to 10 ⁸ Hz, it may have a dielectric constant of 60 to 70 and a dielectric loss of 0.02 or less. Therefore, it can have high dielectric constant and low dielectric loss characteristics over a wide frequency range.

In one embodiment of the present invention, a nanosheet thin film is provided in which a calcium lithium niobate dielectric having a composition represented by the above-mentioned chemical formula 3 is laminated.

The present invention also provides a capacitor, a tunable element, and a gate for a transistor, including the nanosheet thin film described above. As described above, the KCLNO dielectric material exhibits dielectric properties over a wide range and can be used for nanosheet ceramic capacitors, tunable devices, and dielectric films of next-generation TFTs.

Therefore, embodiments of the present invention provide a composition represented by the general formula KCa ₂ LiNb ₄ O ₁₃ (KCLNO), replace K ⁺ ions with H ⁺ ions, and then calcined to form the composition represented by the general formula HCa A dielectric composition _{represented by 2LiNb4O13 (} HCLNO) is provided. In addition, for application to nano-level dielectric films, H ⁺ ions are replaced with TBA ⁺ ions and then peeled off to form a niobic acid-based dielectric represented by the general formula Ca ₂ LiNb ₄ O ₁₃ (CLNO). Provide nanosheets.

Method for Producing Calcium Lithium Niobate Dielectric Composition In another embodiment of the present invention, a potassium precursor, a calcium precursor, a lithium precursor, and a niobium oxide are mixed and calcined to form a dielectric composition represented by Formula 1. forming a dielectric having a composition of:

[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, and y is 0.80≦y≦1.20)
First, a potassium precursor, a calcium precursor, a lithium precursor, and a niobium oxide may be mixed and then calcined.

The types of the potassium precursor, calcium precursor, and lithium precursor are not limited as long as they are potassium compounds, calcium compounds, and lithium compounds, respectively. Specifically, they may be K ₂ CO ₃ , CaCO ₃ , and LiNbO ₃ , respectively, but are not limited thereto. The potassium precursor, calcium precursor, lithium precursor, and niobium oxide preferably have a purity of 99% or more.

For example, using K ₂ CO ₃ , CaCO ₃ , LiNbO ₃ , and Nb ₂ O ₅ , the general formula KCa _x Li _y Nb ₄ O ₁₃ (1.80≦x≦2.20, 0.80≦y≦1 After weighing at a composition ratio that satisfies .20), wet mixing with zirconia balls using ethanol as a solvent in a ball milling process, drying in an oven at 100°C, and then calcining at 1100°C. .

Specifically, K ₂ CO ₃ , CaCO ₃ , and Nb ₂ O ₅ with a purity of 99% or more are weighed at a composition ratio that satisfies the general formula KCa ₂ Nb ₃ O ₁₀ , and then zirconia is prepared using ethanol as a solvent. After wet mixing with balls in a ball mill process, drying in an oven at 100°C and calcining at 1200°C to obtain KCNO, another compound LiNbO ₃ was added to the composition with the general formula KCa ₂ LiNb ₄ It may be weighed according to the composition ratio of O ₁₃ , wet mixed with zirconia balls in a ball milling process, dried in an oven at 100°C, and calcined at 800 to 1200°C to obtain KCLNO.

Next, the dielectric material represented by Chemical Formula 1 may be stirred with an acidic solution to cationically replace K ⁺ ions with H ⁺ ions, thereby forming a dielectric material having a composition represented by Chemical Formula 2.

[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x2.20, y is 0.80≦y≦1.20, x+y=3)
The HCa _x Li _y Nb ₄ O ₁₃ niobic acid dielectric composition represented by the chemical formula 2 is prepared by stirring the dielectric composition represented by the chemical formula 1 with an acidic solution to form a layer between the Ca _x Li _y Nb 4 O ₁₃ layers. It may be produced by cationically replacing K ⁺ ions inserted in each layer with H ⁺ ions. When the dielectric composition represented by Chemical Formula 1 is stirred in an acidic solution, K ⁺ ions are replaced with H ⁺ ions, and a dielectric composition represented by Chemical Formula 2 can be obtained.

For example, the synthesized KCLNO compound can be stirred in a 1M to 7M acid solution such as HNO ₃ , HCl, H ₂ SO ₄ for 5 days to replace the K ⁺ ions intercalated between the CLNO layers with H ⁺ ions. It may be replaced. The replaced solution may be washed several times with DI Water using a centrifuge and then dried at 65° C. for 24 hours to obtain HCLNO. The synthesized KCLNO composition was formed into pellets with a diameter of 12 mm and a height of 0.5 to 1 mm at a pressure of 100 kgf/ ^cm2 , and then sintered in an air atmosphere at 1100 to 1200°C using an electric furnace. ) may be done.

The acidic solution is not particularly limited, and for example, _HNO3 , HCl, _{H2SO4 ,} etc. may be used.

For example, as an embodiment of the chemical formula 1, KCa ₂ LiNb ₄ O13 may be replaced with H ⁺ ions in order to solve the nonlinear dielectric properties, so that the synthesized HCa of the chemical formula 2 The niobic acid dielectric composition represented by _x Li _y Nb4O ₁₃ can have not only a high dielectric constant and low dielectric loss, but also linear dielectric properties in a wide frequency range. That is, the niobic acid dielectric composition represented by HCa _x Li _y Nb4O ₁₃ of chemical formula 2 according to the present invention shows almost no change in capacitance even in a wide range of frequency ranges, maintains a high dielectric constant, and has low dielectric loss. It is characterized by having extremely low properties.

Therefore, the dielectric material represented by HCa _x Li _y Nb ₄ O ₁₃ in the chemical formula 2 exhibits excellent dielectric properties over a wide range, and is therefore used in multilayer ceramic capacitors, microwave dielectrics, dielectric films for next-generation TFTs, etc. It can be used for Furthermore, since it has an excellent dielectric constant even in the bulk state before peeling, it can be applied as a bulk material to microwave dielectrics and the like.

In an exemplary embodiment, the precursor mixture may be formed by wet mixing, and specifically, the precursor mixture may be formed by wet mixing with zirconia balls in a ball milling process.

Next, the dielectric material represented by Chemical Formula 2 may be stirred in a hydroxide solution to form a dielectric material having a composition represented by Chemical Formula 3.

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)
The niobic acid dielectric composition represented by Formula 3 may be prepared by stirring the dielectric composition represented by Formula 2 with a hydroxide solution.

In one embodiment, a single crystal sheet may be peeled off from the prepared nanosheet-like dielectric composition. For example, the dielectric composition represented by the chemical formula 2 may be stirred in a tetrabutylammonium hydroxide (TBAOH) solution, and the H ⁺ ions of the chemical formula 2 may be separated into TBA ⁺ ions to produce a nanosheet thin film. .

In one embodiment, the dielectric having the composition represented by Chemical Formula 3 may have a nanosheet shape from which a bulk dielectric having the composition represented by Chemical Formula 2 has been peeled off.

Specifically, the HCa _x Li _y Nb ₄ O ₁₃ specimen of the present invention, which has a layered structure in which H ⁺ ions are inserted between the Ca _x Li _y Nb ₄ O ₁₃ layers, was mixed with tetrabutylammonium (TBAOH). ) When the solution is stirred for several days, the H ⁺ ions present between the Ca _x Li _y Nb ₄ O ₁₃ layers are stabilized by, for example, TBA ⁺ ions, and the bulk specimen becomes a colloid, forming HCa _x Li _y Nb ₄ O ₁₃ single crystal sheets are peeled off one by one.

The dielectric composition represented by the chemical formula 3 is a nanosheet-like dielectric composition that can be peeled off into a nano-thickness sheet, and even at such a nano-thickness level, it has a high dielectric constant and a low dielectric constant. Indicates dielectric loss. Further, the dielectric composition represented by Formula 3 has linear dielectric characteristics.

In one embodiment, the calcination may be performed at a temperature range of 800-1200°C. Preferably, the temperature may be 900 to 1100°C, more preferably 1000 to 1100°C. If the calcination temperature is less than 800°C, it may not be synthesized into a perovskite material, and if it exceeds 1200°C, melted portions may occur.

In one embodiment, the formed dielectric having the composition represented by Formula 1 may be sintered at 1100-1150° C. in an air atmosphere. If the sintering temperature is less than 1100°C, the size of the particles of the dielectric material may be too small, and if it exceeds 1150°C, melted portions may occur.

In one embodiment, the hydroxide solution includes, but is not limited to, tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide (TEAOH), and The solution may be one or more types selected from the group consisting of tetramethylammonium hydroxide (TMAOH).

In another embodiment of the present invention, there is provided a method for producing a nanosheet thin film, which comprises forming a nanosheet thin film using an electrophoresis method or a Langmuir-Blodgett method using a nanosheet-like dielectric material having a composition represented by chemical formula 3. Ru.

[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20 x+y=3)
Specifically, it has a nanosheet-like dielectric represented by chemical formula 3, and nano single-layer thin films or nanosheets are stacked by electrophoresis or Langmuir-Blodgett (hereinafter referred to as LB method). Multilayer thin films may be formed. A method for forming a thin film of nanosheets includes, for example, using a barrier to disperse exfoliated nanosheets on the water surface of a Langmuir-Blodgett trough to form a monolayer film with a regular nanostructure. The method may include a process of compressing and horizontally or vertically lowering a suitable substrate on which a metal or oxide electrode such as Au, Pt, ITO, or SRO is deposited to transfer a single layer film.

On the other hand, a single layer film or a multilayer film can also be produced by the electrophoresis method and the LB method. The CLNO nanosheet film produced in this way can be applied to future next generation devices at the nano level.

Examples Hereinafter, the structure and effects of the present invention will be explained in more detail with reference to Examples. It should be noted that these Examples are merely provided for illustrative purposes to aid understanding of the present invention, and the scope and scope of the present invention are not limited by the following Examples.

Example 1: Synthesis of KCa ₂ LiNb ₄ O ₁₃ material In order to synthesize a dielectric ceramic material satisfying the composition of the main components expressed as KCa ₂ LiNb ₄ O ₁₃ , K ₂ CO ₃ with a purity of 99% or more was used. , CaCO ₃ , Nb ₂ O ₅ , and LiNbO ₃ are prepared.

Next, each substance is weighed at a composition ratio that satisfies the general formula KCa ₂ Nb ₃ O ₁₀ , and then wet mixed with zirconia balls in a ball mill process for 24 hours using ethanol as a solvent. Thereafter, all the ethanol was dried in an oven at 100°C, and then dry pulverization was performed, and the pulverized material was calcined at 1200°C for 10 hours to obtain KCa ₂ Nb ₃ O ₁₀ .

The obtained KCa ₂ Nb ₃ O ₁₀ and LiNbO ₃ are weighed at a composition ratio that satisfies the general formula KCa ₂ LiNb ₄ O ₁₃ , and are wet mixed together with zirconia balls in a ball milling process for 24 hours using ethanol as a solvent. Calcinate at a temperature of 800-1200°C.

The obtained KCa ₂ LiNb ₄ O ₁₃ dielectric composition was formed into pellets with a diameter of 12 mm and a height of 0.5 to 1 mm under a pressure of 100 kgf/cm ² and sintered in an air atmosphere at 1100 to 1150°C. )did. In order to measure the sintered pellet-shaped ceramic dielectric, a conductive paste was applied to both end faces and heat treated at 600°C.

Test Example 1: KCa ₂ LiNb ₄ O ₁₃ dielectric properties The calcium lithium niobate dielectric specimen prepared in Example 1 was measured with an Impedance Analyzer from Agilent Technologies to confirm its properties. The results are shown in Figures 1 to 4.

FIG. 1 shows the X-ray diffraction analysis characteristics of KCa ₂ LiNb ₄ O ₁₃ according to Example 1, where the horizontal axis shows 2 theta (theta) and the vertical axis shows the intensity of the diffraction peak. It can be seen from this that the phase change does not change significantly even when the calcination temperature changes. However, the calcined X-ray diffraction analysis peaks at 900° C. and 1200° C. indicate that the four-layer octahedral structure and materials in different layers are mixed together.

FIG. 2 shows a scanning electron micrograph of the KCa ₂ LiNb ₄ O ₁₃ sintered body according to Example 1. It can be confirmed from FIG. 2 that the dielectric ceramic material has a layered structure, indicating that plate-shaped particles were formed. The measurement results obtained by such a scanning electron microscope agree well with the above-mentioned X-ray diffraction analysis.

FIG. 3 shows a transmission electron micrograph of the KCa ₂ LiNb ₄ O ₁₃ sintered body according to Example 1, which confirms that the sintered body has a unit cell of 4 layers per layer. be able to.

Next, FIGS. 4a and 4b show the results of measuring the dielectric properties of KCa ₂ LiNb ₄ O ₁₃ according to Example 1. Calcination was performed at 1000°C and sintering was performed at 1100 to 1150°C, and the dielectric constant and dielectric loss were measured. As a result of measuring the dielectric constant and dielectric loss, it can be seen that they exhibit stable values in response to changes in frequency.

Moreover, FIGS. 5a and 5b show the results of comparing the dielectric properties of KCa ₂ LiNb ₄ O ₁₃ (KCLNO) with Li insertion and the stability according to changes in frequency. Figure 5a shows the dielectric constant, and Figure 5b shows the dielectric loss value. The case where the perovskite layer with Li inserted and four assembled layers is present (KCLNO) and the case where the perovskite layer is composed of three layers (KCa) are shown. ₂ Nb ₃ O ₁₀ , KCNO) and the case where Na is inserted instead of Li (KCa ₂ NaNb ₄ O ₁₃ , KCNNO), it has been shown to exhibit high dielectric properties and excellent stability in response to changes in frequency. It can be confirmed.

Example 2: Synthesis of HCa ₂ LiNb ₄ O ₁₃ substance The KCa ₂ LiNb ₄ O ₁₃ powder synthesized in Example 1 was stirred with a 4M HCl solution using a magnetic stirrer for 7 days to convert K ⁺ ions into H Replace with ⁺ ions. The replaced solution is washed several times with DI Water using a centrifuge. During washing, use a PH meter to check whether the PH concentration of the solution approaches neutrality. Then, by drying at 65° C. for 24 hours, HCa ₂ LiNb ₄ O ₁₃ can be obtained.

Example 3: Synthesis of Ca ₂ LiNb ₄ O ₁₃ material and deposition of thin film using thin film LB Next, using the HCa ₂ LiNb ₄ O ₁₃ ceramic material obtained in Example 2, H ⁺ :TBA ⁺ =1 Tetrabutylammonium hydroxide was added at a ratio of :1, and the reaction was stirred at room temperature for 7 to 14 days to form an opaque colloidal solution in which perovskite nanosheets represented by the composition formula Ca ₂ LiNb ₄ O ₁₃ were dispersed. An AFM photograph of the produced colloid is shown in FIG.

Next, the obtained nanosheet colloid solution was dispersed in ultrapure water filled in the LB trough. After developing the dispersion solution, a stabilization time of 30 minutes was allowed for the purpose of stabilizing the water surface and keeping the temperature of the lower liquid constant, and then a prepared substrate such as Au, Pt, ITO, SRO, Nb-STO, etc. The barrier was compressed from both sides at a speed of 1 mm/min to maintain surface pressure, thereby transferring a monolayer film onto the surface of the substrate. This method was repeated several times to produce a perovskite nanosheet thin film having a desired number of layers, and the produced thin film was subjected to UV treatment to remove the organic polymer.

Figures 6a and 6b show AFM photographs of the produced Ca ₂ LiNb ₄ O ₁₃ nanosheets, and from Figure 5 it can be seen that the nanosheets have four monolayers, indicating that they exist as a monolayer. It can be confirmed.

The embodiments of the present invention described above should not be construed as limiting the technical idea of the present invention. The protection scope of the present invention is limited by the matters stated in the claims, and a person having ordinary knowledge in the technical field of the present invention can improve and change the technical idea of the present invention into various forms. It is possible. Therefore, it can be said that such improvements and changes fall within the protection scope of the present invention as long as they are obvious to a person with ordinary knowledge.

Claims (20)

A calcium lithium niobate dielectric composition comprising a calcium lithium niobate dielectric having a composition represented by Chemical Formula 1.
[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) A calcium lithium niobate dielectric comprising a calcium lithium niobate dielectric having a composition represented by chemical formula 2, in which the K ⁺ ions of the calcium lithium niobate dielectric composition according to claim 1 are cationically substituted with H ⁺ ions. Dielectric composition.
[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) The calcium lithium niobate dielectric composition according to claim 2, wherein the calcium lithium niobate dielectric having the composition represented by the chemical formula 2 has a layered structure in which plate-shaped particles are laminated. A calcium lithium niobate dielectric composition comprising a calcium lithium niobate dielectric having a composition represented by chemical formula 3, from which the H ⁺ ions of the calcium lithium niobate dielectric composition according to claim 2 have been removed.
[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) 5. The calcium lithium niobate dielectric composition according to claim 4, wherein the calcium lithium niobate dielectric having the composition represented by Chemical Formula 3 has a nanosheet shape. The calcium lithium niobate dielectric composition of claim 5 , wherein the nanosheets have an average diameter of 50 nm to 50 μm and a thickness of 10 nm or less. 7. The calcium lithium niobate dielectric composition according to any one of claims 1 to 6, wherein the dielectric composition has a dielectric constant of 100 or less and a dielectric loss of 0.25 or less in the frequency range of 10 to 10 ⁴ Hz. Calcium lithium niobate dielectric composition. 7. The calcium lithium niobate dielectric composition according to any one of claims 1 to 6, wherein the dielectric composition has a dielectric constant of 90 or less and a dielectric loss of 0.02 or less in the frequency range of ¹⁰⁴ to ¹⁰⁸ . Calcium lithium niobate dielectric composition. A nanosheet thin film in which a calcium lithium niobate dielectric having a composition represented by the chemical formula 3 according to claim 4 is laminated. A capacitor comprising the nanosheet thin film according to claim 9. A tunable device comprising the nanosheet thin film according to claim 9. A gate for a transistor, comprising the nanosheet thin film according to claim 9. A calcium lithium niobate dielectric composition comprising mixing and calcining a potassium precursor, a calcium precursor, a lithium precursor, and a niobium oxide to form a dielectric having a composition represented by Formula 1. How things are manufactured.
[Chemical formula 1]
KCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) The method further comprises the step of stirring the dielectric represented by Formula 1 with an acidic solution to cationically replace K ⁺ ions with H ⁺ ions to form a dielectric having a composition represented by Formula 2. Item 14. A method for producing a calcium lithium niobate dielectric composition according to item 13.
[Chemical formula 2]
HCa _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) The calcium lithium niobate dielectric of claim 14, further comprising stirring the dielectric represented by Formula 2 with a hydroxide solution to form a dielectric having a composition represented by Formula 3. Method for producing body composition.
[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3) The calcium lithium niobate dielectric composition according to claim 15, wherein the dielectric having a composition represented by Chemical Formula 3 has a nanosheet shape from which a bulk dielectric having a composition represented by Chemical Formula 2 has been peeled off. Production method. The method for producing a calcium lithium niobate dielectric composition according to claim 13, wherein the calcination is performed at a temperature range of 800 to 1200°C. The method for producing a calcium lithium niobate dielectric composition according to claim 13, wherein the formed dielectric having a composition represented by Chemical Formula 1 is sintered in an air atmosphere at 1100 to 1150°C. The hydroxide solution is composed of tetrabutylammonium hydroxide (TBAOH), tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide (TEAOH), and tetramethylammonium hydroxide (TMAOH). The method for producing a calcium lithium niobate dielectric composition according to claim 15, which is one or more solutions selected from the group. A method for producing a nanosheet thin film, which comprises forming a nanosheet thin film from a nanosheet dielectric having a composition represented by chemical formula 3 by an electrophoresis method or a Langmuir-Blodgett method.
[Chemical formula 3]
Ca _x Li _y Nb ₄ O ₁₃
(In the above formula, x is 1.80≦x≦2.20, y is 0.80≦y≦1.20, x+y=3)