WO2021054628A1 - Method for preparing layered cobalt arsenide, layered cobalt arsenide prepared thereby, and cobalt arsenide nanosheet exfoliated therefrom - Google Patents

Method for preparing layered cobalt arsenide, layered cobalt arsenide prepared thereby, and cobalt arsenide nanosheet exfoliated therefrom Download PDF

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WO2021054628A1
WO2021054628A1 PCT/KR2020/011187 KR2020011187W WO2021054628A1 WO 2021054628 A1 WO2021054628 A1 WO 2021054628A1 KR 2020011187 W KR2020011187 W KR 2020011187W WO 2021054628 A1 WO2021054628 A1 WO 2021054628A1
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layered
coas
compound
crystal structure
nanosheet
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French (fr)
Korean (ko)
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심우영
원종범
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연세대학교 산학협력단
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/047—Making non-ferrous alloys by powder metallurgy comprising intermetallic compounds
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/0433—Nickel- or cobalt-based alloys
    • C22C1/0441—Alloys based on intermetallic compounds of the type rare earth - Co, Ni
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/07—Alloys based on nickel or cobalt based on cobalt

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  • the present invention relates to a method of manufacturing a layered cobalt arsenide (CoAs), a layered cobalt arsenide prepared therefrom, a cobalt arsenide nanosheet peeled therefrom, a thermoelectric device including the layered cobalt arsenide or cobalt arsenide nanosheets, optoelectronic devices, and semiconductors.
  • a method for producing a CoAs compound having a 2D layered crystal structure unlike the conventionally known CoAs compound having a 3D crystal structure, a layered CoAs prepared therefrom, and It relates to CoAs nanosheets.
  • 2D materials Due to the limitations of these conventional research methods, 2D materials have been studied very limitedly for materials such as graphene or transition metal chalcogen compounds, and this is essentially the type of element to be used whether or not low-dimensional materials can be developed. It has limitations in that it is limited by the structure and is not suitable for the development of low-dimensional future materials for countless 3D bulk materials that are not layered.
  • CoAs Cobalt arsenide
  • CoAs is a solid crystal compound and is a material used for semiconductors or LEDs.
  • CoAs is also a compound having a 3D bulk crystal structure, and the conventional CoAs having a 3D bulk crystal structure does not have a large surface area compared to its mass, and it is difficult to adjust the band structure. There was a limit to use.
  • the electrical properties of devices required in the electronic field are becoming more and more difficult. Therefore, in order to discover new and excellent properties of CoAs, it is required to develop a technology for manufacturing a material having a layered crystal structure.
  • the present invention has been devised to solve the above-described problems, and the present invention has a 2D layered crystal structure different from CoAs having a conventional 3D bulk crystal structure, so that it is easy to be peeled into a nanosheet, and has excellent electrical conductivity,
  • An object of the present invention is to provide a method for producing a layered CoAs compound capable of adjusting a band structure, a layered CoAs compound prepared by this method, and a CoAs nanosheet exfoliated therefrom.
  • an object of the present invention is to provide a thermoelectric device, an optoelectronic device, and a semiconductor device including the above-described layered CoAs compound or CoAs nanosheet.
  • lithium (Li) powder; Cobalt (Co) powder and arsenic (As) powder are mixed and then heat treated and cooled to have a layered crystal structure in which the space groups are P4/nmm and the crystal system is tetragonal. Obtaining a layered compound represented by LiCoAs; And
  • the layered compound represented by the formula LiCoAs has a multilayer structure of CoAs, and a Li layer is interposed between each of the CoAs layers, and the adjacent CoAs layer and the Li layer are formed by ionic bonding to each other. It may be combined.
  • the solvent is water (H 2 O); And C 1 to C 4 linear or branched alcohols.
  • the heat treatment in step (1) may be performed at a temperature of 700°C to 1,000°C for 1 to 7 days.
  • the cooling in step (1) may be performed at a temperature reduction rate of 0.5°C/h to 3.0°C/h.
  • the solvent treatment in step (2) may be performed at a temperature of 20°C to 60°C.
  • the present invention provides a layered CoAs compound having a layered crystal structure in which the space group is P4/nmm and the crystal system is a tetragonal system.
  • the layered CoAs compound is 14.5 ⁇ 0.2, 27.8 ⁇ 0.2, 33.7 ⁇ 0.2, 36.9 ⁇ in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It can have peaks at 2 ⁇ values of 0.2, 37.9 ⁇ 0.2, 45.2 ⁇ 0.2, 48.4 ⁇ 0.2, 50.9 ⁇ 0.2, 56.9 ⁇ 0.2, and 60.1 ⁇ 0.1, and 42.9 ⁇ 0.2, 52.8 ⁇ 0.2, 53.6 ⁇ 0.2, 54.1 ⁇ 0.2 And may not have a peak at a 2 ⁇ value of 58.9 ⁇ 0.2.
  • the present invention provides a CoAs nanosheet that is peeled from the layered CoAs compound, has a space group of P4/nmm, and has a layered crystal structure of a tetragonal crystal system.
  • the CoAs nanosheet may have a thickness of 30 nm or less.
  • thermoelectric device an optoelectronic device
  • semiconductor device including the above-described layered CoAs compound or CoAs nanosheet.
  • a layered CoAs compound having a layered crystal structure different from the conventional 3D crystal structure of CoAs can be prepared, and the layered CoAs compound thus prepared is easily peeled off into a nanosheet.
  • the 3D crystal structure of the CoAs compound it can provide a wider surface area, and when used as a thermoelectric device or a semiconductor device, excellent electrical conductivity and electron mobility can be realized, and the band structure can be adjusted so that it can be used as an excellent optoelectronic device. have.
  • 1A is a diagram schematically showing a crystal structure of a layered LiCoAs, an intermediate manufactured by a method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
  • 1B is a diagram schematically showing a crystal structure of a layered CoAs according to an embodiment of the present invention.
  • FIG. 2 is a photograph of a layered LiCoAs powder as an intermediate manufactured by a method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
  • 3A is an SEM image of LiCoAs, an intermediate manufactured by the method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
  • 3B is an SEM image of a layered CoAs according to an embodiment of the present invention.
  • FIG. 4 is a TEM image of a layered CoAs according to an embodiment of the present invention.
  • FIG. 5 is a graph showing an XRD peak of a layered LiCoAs, a layered CoAs, and CoAs having a conventional 3D bulk crystal structure and a reference XRD peak of LiCoAs according to an embodiment of the present invention.
  • AFM Anamic Force Microscope
  • FIG. 7 is a STEM image of a layered CoAs according to a preferred embodiment of the present invention, taken from left to right in HAADF, DF, and ABF modes, respectively.
  • FIG. 8 is a superimposed view of a STEM image of a layered CoAs and a schematic diagram of a crystal structure thereof according to a preferred embodiment of the present invention.
  • the conventional CoAs compound has a 3D bulk-type crystal structure and has a property that is difficult to be peeled off into a nano sheet, etc., and accordingly, the surface area per mass is small, and the electrical properties such as electrical conductivity and electron mobility are low, and the band The structure could not be adjusted either.
  • the present invention (1) lithium (Li) powder; After mixing cobalt (Co) powder and arsenic (As) powder, it has a layered crystal structure in which the space groups are P4/nmm and the crystal system is tetragonal by sequentially heat treatment and cooling. , Obtaining a layered compound represented by the formula LiCoAs; And (2) treating a solvent capable of selectively removing Li ions contained in the layered compound to prepare a layered CoAs compound without changing the crystal structure of the layered LiCoAs compound. By providing a method for preparing a compound, a solution to this problem was sought.
  • a CoAs compound having a 2D layered crystal structure can be prepared using a layered LiCoAs as a matrix material.
  • the layered CoAs compound prepared according to the present invention has a 2D layered crystal structure completely different from CoAs having a conventional 3D bulk crystal structure, and has an excellent electrical conductivity, which is advantageous for thermoelectric devices and optoelectronic devices.
  • step (1) lithium (Li) powder, cobalt (Co) powder, and arsenic (As) powder are each mixed, followed by heat treatment and cooling to prepare a LiCoAs compound.
  • lithium, cobalt, and arsenic powder are added at a time, and the three elements react simultaneously to form LiCoAs.
  • lithium powder, cobalt powder and arsenic powder are provided to the reaction in an elemental state here. If the reactants are introduced into the reaction in the form of a compound with another element, reactivity and crystallinity may decrease due to reaction by-products, and a desired layered compound may not be obtained.
  • the powder mixture may be heat-treated after being sealed in a reaction vessel, and the inside of the reaction vessel may be maintained in an inert gas atmosphere or a vacuum atmosphere.
  • the inert gas may be preferably nitrogen (N 2 ) or argon (Ar) gas.
  • the heat treatment for sintering the mixture may be performed at a temperature of 700°C to 1,000°C for 1 to 7 days. If the heat treatment is performed at less than 700°C, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered compound prepared may be lowered. have. In addition, when the heat treatment is performed in excess of 1,000°C, the sintering reaction is intensified due to the vaporization of Li ions, so that it is difficult to constantly control the reaction conditions, and the yield of the layered compound to be produced may be decreased. .
  • the heat treatment when the heat treatment is performed for less than 1 day, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered compound prepared may be reduced. have.
  • the heat treatment when the heat treatment is performed for more than 10 days, since the manufacturing process time is unnecessarily increased and productivity is lowered, it is preferable to perform it within 10 days.
  • the material of the reaction vessel may be preferably alumina, molybdenum, tungsten, or quartz, but any material that does not react with the sample and does not break at a high temperature within the heat treatment temperature range may be used without limitation.
  • It includes a step of cooling at a predetermined temperature reduction rate after performing the heat treatment, and in the cooling step, it may be performed at a temperature reduction rate of 0.5°C/h to 3.0°C/h from the heat treatment temperature to room temperature.
  • a temperature reduction rate of 0.5°C/h to 3.0°C/h from the heat treatment temperature to room temperature.
  • the LiCoAs compound produced through the step (1) has a layered crystal structure, and more specifically, a layered layer in which the space group is P4/nmm and the crystal system is tetragonal. It has a crystal structure of
  • 1A is a diagram schematically showing a crystal structure of a layered LiCoAs, an intermediate manufactured according to the method of manufacturing a layered CoAs according to the present invention.
  • the crystal structure of the layered LiCoAs compound is a layered crystal structure, and the CoAs compound has a layered structure, and between each CoAs layer
  • the Li ion layer may be interposed. With such a structure, when only Li ions are selectively removed in a later step, a layered CoAs can be obtained.
  • the CoAs layer and the Li layer may be bonded to each other by an ionic bond. Since ionic bonds are formed, it is easy to selectively remove only Li ions due to the difference in attractive force between the solvent molecules and each layer during solvent treatment. In this case, it is possible to obtain a layered CoAs compound without changing the crystal structure of the CoAs layer. If a covalent bond is formed, it may be difficult to selectively remove Li ions only by solvent treatment.
  • step (2) a step of selectively removing Li ions contained in the layered LiCoAs compound prepared following step (1) is performed.
  • Li ions contained in the layered compound are selectively removed by treating a solvent having a high reactivity with Li ions, and such a solvent includes at least one selected from water (H2O) and a linear or branched alcohol of C1 to C4. It can be. More preferably, the solvent may include at least one selected from water, ethanol and isopropanol, more preferably water.
  • D.I. water deionized water
  • the solvent treatment in step (2) may be performed at a temperature at which the removal reaction of the alkali metal ions, that is, Li ions, can occur smoothly, and the temperature may vary depending on the composition of the mixed solution, but preferably 20 It can be carried out at a temperature of more than °C °C, more preferably at a temperature of 20 °C to 60 °C. If performed at less than 20°C, alkali metal ions may not be removed to the desired level or the layered structure of the prepared layered compound may collapse, and when performed at a temperature exceeding 60°C, the prepared layered compound The layered structure of can collapse. In addition, when performed at a temperature of 20°C to 60°C, the alkali metal ion removal rate may be excellent while maintaining the layered structure of the layered compound to be prepared.
  • the solvent treatment is preferably performed for about 2 to 4 days. If performed within 2 days, Li ions may not be sufficiently removed, and it is preferable not to exceed 4 days in order to improve productivity.
  • step (2) may be performed multiple times depending on the composition of the mixed solution and the removal rate of Li ions, but is preferably performed once to maintain the layered structure of the layered CoAs to be prepared.
  • the present invention provides a layered CoAs compound having a layered crystal structure in which a space group is P4/nmm and a crystal system is tetragonal, prepared according to the above-described manufacturing method.
  • FIG. 1B is a diagram schematically showing a crystal structure of a layered CoAs compound according to an embodiment of the present invention.
  • a layered crystal structure made of CoAs is shown, which is different from the 3D bulk crystal structure of the conventional CoAs.
  • the CoAs compound of the present invention can be easily peeled into a nanosheet compared to a CoAs compound having a conventional 3D bulk crystal structure, and the band structure can be adjusted, and the electrical conductivity and electron Movement is also effective.
  • the layered CoAs compound according to the present invention is 14.5 ⁇ 0.2, 27.8 ⁇ 0.2, 33.7 ⁇ 0.2, 36.9 ⁇ 0.2, 37.9 in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It can have peaks at 2 ⁇ values of ⁇ 0.2, 45.2 ⁇ 0.2, 48.4 ⁇ 0.2, 50.9 ⁇ 0.2, 56.9 ⁇ 0.2, and 60.1 ⁇ 0.1.
  • FIG. 5 is a view comparing XRD peaks of the layered CoAs compound according to the present invention, the reference XRD peaks of the layered LiCoAs compound and LiCoAs prepared in step (1), and the CoAs compound having a conventional 3D bulk crystal structure.
  • the XRD data of the layered CoAs according to the present invention 14.5 ⁇ 0.2, 27.8 ⁇ 0.2, 33.7 ⁇ 0.2, 36.9 ⁇ 0.2, 37.9 ⁇ 0.2, 45.2 ⁇ 0.2, 48.4 ⁇ 0.2, 50.9 ⁇ 0.2, 56.9 ⁇ 0.2 and 60.1 It can be seen that it has a peak at a 2 ⁇ value of ⁇ 0.1, and on the contrary, the XRD data of CoAs with a 3D bulk crystal structure peak at 2 ⁇ values of 42.9 ⁇ 0.2, 52.8 ⁇ 0.2, 53.6 ⁇ 0.2, 54.1 ⁇ 0.2, and 58.9 ⁇ 0.2. On the other hand, it can be seen that the layered CoAs according to the present invention does not have a peak at the 2 ⁇ value, and it can be seen that it has a crystal structure different from the conventional CoAs compound having a 3D bulk crystal structure.
  • the CoAs nanosheet according to the present invention can be obtained by peeling from the layered CoAs compound according to the present invention, and the space group is P4/nmm, and the crystal system is tetragonal.
  • the details of the effect of having a crystal structure are the same as those of the above-described layered CoAs, and thus will be omitted.
  • the CoAs nanosheet may be prepared by peeling from the layered CoAs compound described above, and the method for peeling may be selected from peeling methods for layered materials known in the art, for example, peeling by energy by ultrasonic waves. Any one of a method of performing, a peeling method by intrusion of a solvent, a peeling method using a tape, and a peeling method using a material having an adhesive surface may be used.
  • the CoAs nanosheet may have a thickness of 30 nm or less. By having such a thin thickness, it has a large surface area, the band structure can be adjusted by an additional process, and electron mobility and electrical conductivity are more excellent than that of the conventional 3D bulk CoAs compound.
  • thermoelectric device an optoelectronic device
  • semiconductor device including the layered CoAs or CoAs nanosheet.
  • thermoelectric device has a high Seebeck constant due to the excellent electrical conductivity of the layered CoAs or CoAs nanosheet.
  • LiCoA prepared in Preparation Example 1 was mixed with deionized water and reacted for 3 days to remove Li ions from the LiCoAs, through which a layered CoAs compound having a space group of P4/nmm and a crystal system of a tetragonal system was prepared.
  • the layered CoAs prepared in Example 1 was peeled off with a scotch tape (3M) to prepare a CoAs nanosheet.
  • Co powder and As powder were heat-treated at 950° C. for 120 hours and then cooled to prepare a 3D bulk CoAs compound.
  • XRD analysis was performed on the samples prepared according to Preparation Example 1 and Example 1, and the results are shown in FIG. 5.
  • FIG. 5 the XRD analysis results of LiCoAs prepared according to the prior art are shown together as a reference (LiCoAs reference), and the XRD peaks of 3D bulk CoAs prepared according to Comparative Example 1 are also shown.
  • the XRD diffraction pattern of the layered CoAs (1Q-CoAs) of Example 1 prepared according to the present invention is different from the conventional CoAs compound having a 3D bulk crystal structure. From this, it can be seen that the crystal structure is different.
  • the CoAs nanosheet according to Example 2 was peeled to a thickness of 30 nm or less.

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Abstract

The present invention relates to: a method for preparing layered cobalt arsenide (CoAs); layered cobalt arsenide prepared thereby; a cobalt arsenide nanosheet exfoliated therefrom; and a thermoelement, an optoelectronic device and a semiconductor device which comprise the layered cobalt arsenide or the cobalt arsenide nanosheet, and, more specifically, to: a method for preparing CoAs compound having a 2D layered crystal structure, unlike known CoAs compound having a 3D crystal structure; layered CoAs prepared thereby; and a CoAs nanosheet exfoliated therefrom.

Description

층상형 비화코발트의 제조방법, 그로부터 제조된 층상형 비화코발트, 그로부터 박리된 비화코발트 나노시트Method for producing layered cobalt arsenide, layered cobalt arsenide prepared therefrom, cobalt arsenide nanosheets peeled therefrom
본 발명은 층상형 비화코발트(CoAs)의 제조방법, 그로부터 제조된 층상형 비화코발트, 그로부터 박리된 비화코발트 나노시트, 상기 층상형 비화코발트 또는 비화코발트 나노시트를 포함하는 열전 소자, 광전자 소자 및 반도체 소자에 관한 것으로서, 좀 더 구체적으로는 종래에 알려져 있던 CoAs 화합물이 3D의 결정구조를 갖는 것과 달리 2D의 층상형의 결정 구조를 갖는 CoAs 화합물의 제조방법, 그로부터 제조된 층상형 CoAs 및 그로부터 박리된 CoAs 나노시트에 관한 것이다.The present invention relates to a method of manufacturing a layered cobalt arsenide (CoAs), a layered cobalt arsenide prepared therefrom, a cobalt arsenide nanosheet peeled therefrom, a thermoelectric device including the layered cobalt arsenide or cobalt arsenide nanosheets, optoelectronic devices, and semiconductors. Regarding the device, more specifically, a method for producing a CoAs compound having a 2D layered crystal structure, unlike the conventionally known CoAs compound having a 3D crystal structure, a layered CoAs prepared therefrom, and It relates to CoAs nanosheets.
그래핀을 비롯한 다양한 초박막 2차원(2D) 재료들은 새로운 물리적, 화학적, 기계적 및 광학적 특성을 바탕으로 다양한 분야에서 활발히 연구가 되고 있다. 이러한 저차원의 소재는 기존의 벌크 소재가 가지지 못하는 획기적인 신기능이 기대되고 기존 소재를 대체할 차세대 미래 소재로서 가능성이 매우 크다.Various ultra-thin two-dimensional (2D) materials including graphene are being actively studied in various fields based on new physical, chemical, mechanical, and optical properties. These low-dimensional materials are expected to have innovative new functions that existing bulk materials do not have, and have great potential as a next-generation future material that will replace existing materials.
기존 2D 소재에 대한 연구는 층간(interlayer)의 결합력이 약한 반 데르 발스 결합을 물리적 및 화학적 방법으로 분리하는 Top-down 법, 기상증착법에 기반한 대면적 박막을 성장시키는 Bottom-up 법을 기반으로 진행되고 있다. 특히, Top-down 법은 박리(exfoliation) 대상 물질의 모상(pristine)이 반드시 2차원적인 층상 결정 구조를 가져야 하므로 밴드갭이 없는 그래핀, 전하 이동도가 낮은 층상 금속 산화물/질화물, 전자이동도/전기전도도가 낮은 전이금속 칼코겐 화합물 등 연구 대상이 매우 제한적인 문제점이 있다.Research on existing 2D materials is based on a top-down method that separates van der Waals bonds with weak interlayer bonding by physical and chemical methods, and a bottom-up method that grows a large-area thin film based on a vapor deposition method. Has become. In particular, in the top-down method, since the pristine of the material to be exfoliated must have a two-dimensional layered crystal structure, graphene without a band gap, layered metal oxide/nitride with low charge mobility, and electron mobility. / There is a problem of very limited research targets such as transition metal chalcogen compounds with low electrical conductivity.
이러한 종래 연구 방법의 한계로 인하여 2D 소재는 그래핀이나 전이 금속 칼코겐 화합물 등의 물질을 대상으로 매우 제한적으로 연구가 진행되었으며, 이는 본질적으로 저차원 소재의 개발 가능 여부가 사용하고자 하는 원소의 종류에 따라 제한된다는 점에서 한계를 가지며 층상구조가 아닌 무수히 많은 3D 벌크 소재의 저차원 미래 소재 개발에는 적합하지 않은 방법이다.Due to the limitations of these conventional research methods, 2D materials have been studied very limitedly for materials such as graphene or transition metal chalcogen compounds, and this is essentially the type of element to be used whether or not low-dimensional materials can be developed. It has limitations in that it is limited by the structure and is not suitable for the development of low-dimensional future materials for countless 3D bulk materials that are not layered.
비화코발트(CoAs)는 고체 결정 화합물로, 반도체 또는 LED 등에 사용되는 물질이다. CoAs도 역시 3D 벌크형의 결정 구조를 가지는 화합물로서, 종래의 3D 벌크형 결정구조를 갖는 CoAs는 질량에 비해 표면적이 크지 않으며, 밴드 구조(band structure)의 조정이 어려운 문제점이 있어 열전소자, 광전소자 등에 사용하는 데 한계가 있었다. 그러나, 기술의 발전에 따라서 전자 분야에서 요구되는 소자들의 전기적 성질은 점점 더 까다로워지고 있다. 따라서 CoAs의 새롭고 우수한 성질을 발견하기 위하여 층상형의 결정 구조를 갖는 물질을 제조하기 위한 기술의 개발이 요구되고 있다.Cobalt arsenide (CoAs) is a solid crystal compound and is a material used for semiconductors or LEDs. CoAs is also a compound having a 3D bulk crystal structure, and the conventional CoAs having a 3D bulk crystal structure does not have a large surface area compared to its mass, and it is difficult to adjust the band structure. There was a limit to use. However, with the development of technology, the electrical properties of devices required in the electronic field are becoming more and more difficult. Therefore, in order to discover new and excellent properties of CoAs, it is required to develop a technology for manufacturing a material having a layered crystal structure.
본 발명은 상술한 과제를 해결하기 위하여 안출된 것으로서, 본 발명은 종래의 3D 벌크형 결정 구조를 갖는 CoAs와 상이하게 2D 층상형 결정 구조를 가져 나노시트로 박리되기 용이하고, 전기 전도성이 우수하고, 밴드 구조의 조정이 가능한 층상형 CoAs 화합물의 제조방법, 이러한 제조방법에 의하여 제조된 층상형 CoAs 화합물 및 이로부터 박리된 CoAs 나노시트를 제공하는 것을 목적으로 한다.The present invention has been devised to solve the above-described problems, and the present invention has a 2D layered crystal structure different from CoAs having a conventional 3D bulk crystal structure, so that it is easy to be peeled into a nanosheet, and has excellent electrical conductivity, An object of the present invention is to provide a method for producing a layered CoAs compound capable of adjusting a band structure, a layered CoAs compound prepared by this method, and a CoAs nanosheet exfoliated therefrom.
또한, 본 발명은 상술한 층상형 CoAs 화합물 또는 CoAs 나노시트를 포함하는 열전소자, 광전자 소자 및 반도체 소자를 제공하는 것을 목적으로 한다.In addition, an object of the present invention is to provide a thermoelectric device, an optoelectronic device, and a semiconductor device including the above-described layered CoAs compound or CoAs nanosheet.
상술한 과제를 해결하기 위하여, 본 발명은In order to solve the above problems, the present invention
(1) 리튬(Li) 분말; 코발트(Co) 분말 및 비소(As) 분말을 혼합한 후 열처리 및 냉각하여 공간군(space groups)이 P4/nmm이고 결정계(crystal system)가 정방정계(tetragonal)인 층상형 결정구조를 가지며, 화학식 LiCoAs로 표시되는 층상형 화합물을 수득하는 단계; 및(1) lithium (Li) powder; Cobalt (Co) powder and arsenic (As) powder are mixed and then heat treated and cooled to have a layered crystal structure in which the space groups are P4/nmm and the crystal system is tetragonal. Obtaining a layered compound represented by LiCoAs; And
(2) 상기 층상형 화합물에 포함된 Li 이온을 선택적으로 제거할 수 있는 용매를 처리하여 상기 층상형 LiCoAs 화합물의 결정구조의 변화 없이 층상형 CoAs 화합물을 제조하는 단계;를 포함하는 층상형 CoAs 화합물의 제조방법을 제공한다.(2) preparing a layered CoAs compound without changing the crystal structure of the layered LiCoAs compound by treating a solvent capable of selectively removing Li ions contained in the layered compound; It provides a method of manufacturing.
본 발명의 일 실시예에 있어서, 상기 화학식 LiCoAs로 표시되는 층상형 화합물은 CoAs의 다층 구조를 갖고 상기 각 CoAs 층 사이에 Li 층이 개재되어 있으며, 인접한 CoAs 층과 Li 층은 서로 이온 결합에 의하여 결합되어 있는 것일 수 있다.In an embodiment of the present invention, the layered compound represented by the formula LiCoAs has a multilayer structure of CoAs, and a Li layer is interposed between each of the CoAs layers, and the adjacent CoAs layer and the Li layer are formed by ionic bonding to each other. It may be combined.
본 발명의 일 실시예에 있어서, 상기 용매는 물(H2O); 및 C1~C4의 선형 또는 분지형 알코올 중에서 선택된 적어도 어느 하나를 포함하는 것일 수 있다.In one embodiment of the present invention, the solvent is water (H 2 O); And C 1 to C 4 linear or branched alcohols.
본 발명의 일 실시예에 있어서, 상기 (1) 단계의 열처리는 700℃ 내지 1,000℃의 온도에서 1일(days) 내지 7일 동안 수행되는 것일 수 있다.In an embodiment of the present invention, the heat treatment in step (1) may be performed at a temperature of 700°C to 1,000°C for 1 to 7 days.
본 발명의 일 실시예에 있어서, 상기 (1) 단계의 냉각은 0.5℃/h 내지 3.0℃/h의 감온 속도로 수행되는 것일 수 있다.In an embodiment of the present invention, the cooling in step (1) may be performed at a temperature reduction rate of 0.5°C/h to 3.0°C/h.
본 발명의 일 실시예에 있어서, 상기 (2) 단계의 용매 처리는 20℃ 내지 60℃의 온도에서 수행되는 것일 수 있다.In one embodiment of the present invention, the solvent treatment in step (2) may be performed at a temperature of 20°C to 60°C.
또한, 본 발명은 공간군이 P4/nmm이고 결정계가 정방정계인 층상형 결정구조를 가지는 층상형 CoAs 화합물을 제공한다.In addition, the present invention provides a layered CoAs compound having a layered crystal structure in which the space group is P4/nmm and the crystal system is a tetragonal system.
본 발명의 일 실시예에 있어서, 상기 층상형 CoAs 화합물은 Cu-Ka선을 이용한 분말 X선 회절법에 의하여 얻어지는 X선 회절도에 있어서, 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2 및 60.1±0.1의 2θ 값에서 피크를 가질 수 있으며, 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2 및 58.9±0.2의 2θ 값에서 피크를 갖지 않을 수 있다.In an embodiment of the present invention, the layered CoAs compound is 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9± in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It can have peaks at 2θ values of 0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2, and 60.1±0.1, and 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2 And may not have a peak at a 2θ value of 58.9±0.2.
또한, 본 발명은 상기 층상형 CoAs 화합물로부터 박리되고, 공간군이 P4/nmm이며, 정방정계 결정계의 층상형 결정구조를 갖는 CoAs 나노시트를 제공한다.In addition, the present invention provides a CoAs nanosheet that is peeled from the layered CoAs compound, has a space group of P4/nmm, and has a layered crystal structure of a tetragonal crystal system.
본 발명의 일 실시예에 있어서, 상기 CoAs 나노시트는 두께가 30nm 이하일 수 있다.In an embodiment of the present invention, the CoAs nanosheet may have a thickness of 30 nm or less.
또한, 본 발명은 상술한 층상형 CoAs 화합물 또는 CoAs 나노시트를 포함하는 열전소자, 광전자소자 및 반도체 소자를 제공한다.In addition, the present invention provides a thermoelectric device, an optoelectronic device, and a semiconductor device including the above-described layered CoAs compound or CoAs nanosheet.
본 발명에 따른 제조방법에 의하여 종래의 CoAs의 3D 결정 구조와 상이한 층상의 결정 구조를 갖는 층상형 CoAs 화합물을 제조할 수 있고, 이렇게 제조된 층상형 CoAs 화합물은 나노시트로 박리되기 용이하며, 종래의 3D 결정 구조의 CoAs 화합물에 비하여 넓은 표면적을 제공할 수 있으며, 열전소자 또는 반도체 소자 등으로 사용 시 우수한 전기 전도성 및 전자이동도를 구현할 수 있으며, 밴드 구조를 조절할 수 있어 우수한 광전자소자로 활용할 수 있다.By the production method according to the present invention, a layered CoAs compound having a layered crystal structure different from the conventional 3D crystal structure of CoAs can be prepared, and the layered CoAs compound thus prepared is easily peeled off into a nanosheet. Compared to the 3D crystal structure of the CoAs compound, it can provide a wider surface area, and when used as a thermoelectric device or a semiconductor device, excellent electrical conductivity and electron mobility can be realized, and the band structure can be adjusted so that it can be used as an excellent optoelectronic device. have.
도 1a는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 제조방법에 의하여 제조된 중간체인 층상형 LiCoAs의 결정 구조를 개략적으로 나타낸 도면이다.1A is a diagram schematically showing a crystal structure of a layered LiCoAs, an intermediate manufactured by a method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
도 1b는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 결정 구조를 개략적으로 나타낸 도면이다.1B is a diagram schematically showing a crystal structure of a layered CoAs according to an embodiment of the present invention.
도 2는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 제조방법에 의하여 제조된 중간체인 층상형 LiCoAs 파우더의 사진이다.2 is a photograph of a layered LiCoAs powder as an intermediate manufactured by a method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
도 3a는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 제조방법에 의하여 제조된 중간체인 LiCoAs의 SEM 이미지이다.3A is an SEM image of LiCoAs, an intermediate manufactured by the method of manufacturing a layered CoAs according to a preferred embodiment of the present invention.
도 3b는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 SEM 이미지이다.3B is an SEM image of a layered CoAs according to an embodiment of the present invention.
도 4는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 TEM 이미지이다.4 is a TEM image of a layered CoAs according to an embodiment of the present invention.
도 5는 본 발명의 일 실시예에 따른 층상형 LiCoAs, 층상형 CoAs, 종래의 3D 벌크형 결정구조를 가지는 CoAs의 XRD 피크와 LiCoAs의 레퍼런스 XRD 피크를 나타낸 그래프이다.5 is a graph showing an XRD peak of a layered LiCoAs, a layered CoAs, and CoAs having a conventional 3D bulk crystal structure and a reference XRD peak of LiCoAs according to an embodiment of the present invention.
도 6은 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 AFM(Atomic Force Microscope) 이미지(좌) 및 그 분석 그래프(우)이다.6 is an AFM (Atomic Force Microscope) image (left) and an analysis graph thereof (right) of a layered CoAs according to a preferred embodiment of the present invention.
도 7은 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 STEM 이미지로 좌측에서 우측 방향으로 각각 HAADF, DF 및 ABF 모드로 촬영한 것이다.7 is a STEM image of a layered CoAs according to a preferred embodiment of the present invention, taken from left to right in HAADF, DF, and ABF modes, respectively.
도 8은 본 발명의 바람직한 일실시예에 따른 층상형 CoAs의 STEM 이미지와 그 결정 구조의 개략도를 중첩 표시한 것이다.8 is a superimposed view of a STEM image of a layered CoAs and a schematic diagram of a crystal structure thereof according to a preferred embodiment of the present invention.
이하, 첨부한 도면을 참고로 하여 본 발명의 실시예에 대하여 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자가 용이하게 실시할 수 있도록 상세히 설명한다. 본 발명은 여러 가지 상이한 형태로 구현될 수 있으며, 여기에서 설명하는 실시예에 한정되지 않는다.Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms, and is not limited to the embodiments described herein.
상술한 바와 같이, 종래의 CoAs 화합물은 3D 벌크형의 결정 구조를 가져, 나노 시트 등으로 박리되기 어려운 성질을 가졌으며, 이에 따라 질량당 표면적이 작고 전기전도성, 전자이동도 등의 전기적 특성이 낮고 밴드 구조 또한 조정할 수 없었다.As described above, the conventional CoAs compound has a 3D bulk-type crystal structure and has a property that is difficult to be peeled off into a nano sheet, etc., and accordingly, the surface area per mass is small, and the electrical properties such as electrical conductivity and electron mobility are low, and the band The structure could not be adjusted either.
이에, 본 발명은 (1) 리튬(Li) 분말; 코발트(Co) 분말 및 비소(As) 분말을 혼합한 후 순차적으로 열처리 및 냉각하여 공간군(space groups)이 P4/nmm이고 결정계(crystal system)가 정방정계(tetragonal)인 층상형 결정구조를 가지며, 화학식 LiCoAs로 표시되는 층상형 화합물을 수득하는 단계; 및 (2) 상기 층상형 화합물에 포함된 Li 이온을 선택적으로 제거할 수 있는 용매를 처리하여 상기 층상형 LiCoAs 화합물의 결정구조에 변화 없이 층상형 CoAs 화합물을 제조하는 단계;를 포함하는 층상형 CoAs 화합물의 제조방법을 제공하여 이와 같은 문제점의 해결을 모색하였다.Thus, the present invention (1) lithium (Li) powder; After mixing cobalt (Co) powder and arsenic (As) powder, it has a layered crystal structure in which the space groups are P4/nmm and the crystal system is tetragonal by sequentially heat treatment and cooling. , Obtaining a layered compound represented by the formula LiCoAs; And (2) treating a solvent capable of selectively removing Li ions contained in the layered compound to prepare a layered CoAs compound without changing the crystal structure of the layered LiCoAs compound. By providing a method for preparing a compound, a solution to this problem was sought.
본 발명의 방법에 따르면 다원계 물질인 층상형의 LiCoAs를 모상으로 하여 2D 층상형의 결정구조를 갖는 CoAs 화합물을 제조할 수 있다.According to the method of the present invention, a CoAs compound having a 2D layered crystal structure can be prepared using a layered LiCoAs as a matrix material.
본 발명에 따라서 제조한 층상형 CoAs 화합물은 기존의 3D 벌크형 결정 구조를 갖는 CoAs와는 전혀 상이한 2D 층상의 결정 구조를 가지며, 전기전도성이 더 우수하여 열전소자 및 광전자소자 에 유리한 장점이 있다.The layered CoAs compound prepared according to the present invention has a 2D layered crystal structure completely different from CoAs having a conventional 3D bulk crystal structure, and has an excellent electrical conductivity, which is advantageous for thermoelectric devices and optoelectronic devices.
먼저, (1) 단계로서, 리튬(Li) 분말, 코발트(Co) 분말 및 비소(As) 분말을 각각 혼합한 후 순차적으로 열처리 및 냉각하여 LiCoAs 화합물을 제조한다.First, as step (1), lithium (Li) powder, cobalt (Co) powder, and arsenic (As) powder are each mixed, followed by heat treatment and cooling to prepare a LiCoAs compound.
이 때, 바람직하게는 리튬, 코발트 및 비소 분말을 한번에 투입하여 세 원소가 동시에 반응하여 LiCoAs를 형성하는 것이 좋다.At this time, preferably, lithium, cobalt, and arsenic powder are added at a time, and the three elements react simultaneously to form LiCoAs.
또한, 여기서 리튬 분말, 코발트 분말 및 비소 분말은 원소 상태로 반응에 제공되는 것이 바람직하다. 만일 상기 반응물들이 다른 원소와의 화합물 상태로 반응에 투입되는 경우, 반응 부산물로 인하여 반응성 및 결정성이 떨어지고 원하는 층상형 화합물을 얻지 못할 수 있다.Further, it is preferable that lithium powder, cobalt powder and arsenic powder are provided to the reaction in an elemental state here. If the reactants are introduced into the reaction in the form of a compound with another element, reactivity and crystallinity may decrease due to reaction by-products, and a desired layered compound may not be obtained.
상기 분말 혼합물은 반응 용기에 봉입된 후 열처리될 수 있으며, 상기 반응용기 내부는 불활성 기체 분위기 또는 진공 분위기로 유지될 수 있다. 이때, 상기 불활성 기체는 바람직하게는 질소(N2) 또는 아르곤(Ar) 기체일 수 있다.The powder mixture may be heat-treated after being sealed in a reaction vessel, and the inside of the reaction vessel may be maintained in an inert gas atmosphere or a vacuum atmosphere. In this case, the inert gas may be preferably nitrogen (N 2 ) or argon (Ar) gas.
그러나, 반드시 이에 제한되는 것은 아니다.However, it is not necessarily limited thereto.
상기 혼합물을 소결하기 위한 열처리는 700℃ 내지 1,000℃의 온도에서 1일(days) 내지 7일간 수행될 수 있다. 만일, 상기 열처리가 700℃ 미만으로 수행될 경우, 상기 혼합물의 소결 반응이 완료되지 않아 미반응된 원재료가 잔류할 수 있고, 이에 따라 제조되는 층상형 화합물의 수율이 저하되는 등의 문제가 있을 수 있다. 또한, 상기 열처리가 1,000℃를 초과하여 수행될 경우, Li 이온의 기화로 소결 반응이 격화되어 반응 조건을 일정하게 조절하기 어렵고, 제조되는 층상형 화합물의 수율이 저하되는 등의 문제가 있을 수 있다.The heat treatment for sintering the mixture may be performed at a temperature of 700°C to 1,000°C for 1 to 7 days. If the heat treatment is performed at less than 700°C, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered compound prepared may be lowered. have. In addition, when the heat treatment is performed in excess of 1,000°C, the sintering reaction is intensified due to the vaporization of Li ions, so that it is difficult to constantly control the reaction conditions, and the yield of the layered compound to be produced may be decreased. .
또한, 상기 열처리가 1일 미만으로 수행되는 경우, 상기 혼합물의 소결 반응이 완료되지 않아 미반응된 원재료가 잔류할 수 있고, 이에 따라 제조되는 층상형 화합물의 수율이 저하되는 등의 문제가 있을 수 있다. 또한, 상기 열처리가 10일을 초과하여 수행될 경우, 제조 공정 시간이 불필요하게 증가하여 생산성이 저하되므로, 10일 이내로 수행하는 것이 바람직하다.In addition, when the heat treatment is performed for less than 1 day, the sintering reaction of the mixture may not be completed, so that unreacted raw materials may remain, and thus the yield of the layered compound prepared may be reduced. have. In addition, when the heat treatment is performed for more than 10 days, since the manufacturing process time is unnecessarily increased and productivity is lowered, it is preferable to perform it within 10 days.
상기 반응용기의 소재는 바람직하게는 알루미나, 몰리브덴, 텅스텐 또는 석영일 수 있으나, 시료와 반응하지 않고, 상기 열처리 온도 범위의 고온에서 파손되지 않는 소재라면 소재에 제한 없이 사용할 수 있다.The material of the reaction vessel may be preferably alumina, molybdenum, tungsten, or quartz, but any material that does not react with the sample and does not break at a high temperature within the heat treatment temperature range may be used without limitation.
열처리를 수행한 후에 소정의 감온 속도로 냉각시키는 단계를 포함하게 되며, 냉각 단계에서는 열처리 온도로부터 상온까지 0.5℃/h 내지 3.0℃/h의 감온 속도로 수행할 수 있다. 이러한 감온 속도 조건을 만족하는 경우, 제조되는 층상형 화합물의 구조에 변형을 최소화할 수 있다.It includes a step of cooling at a predetermined temperature reduction rate after performing the heat treatment, and in the cooling step, it may be performed at a temperature reduction rate of 0.5°C/h to 3.0°C/h from the heat treatment temperature to room temperature. When the temperature reduction rate condition is satisfied, it is possible to minimize deformation in the structure of the layered compound to be prepared.
상기 (1) 단계를 통하여 생성된 LiCoAs 화합물은 층상형의 결정 구조를 가지고 있으며, 좀 더 구체적으로는 공간군(space group)이 P4/nmm이며 결정계(crystal system)가 정방정계(tetragonal)인 층상의 결정구조를 갖는다.The LiCoAs compound produced through the step (1) has a layered crystal structure, and more specifically, a layered layer in which the space group is P4/nmm and the crystal system is tetragonal. It has a crystal structure of
도 1a는 본 발명에 따른 층상형 CoAs의 제조방법에 따라 제조된 중간체인 층상형 LiCoAs의 결정 구조를 개략적으로 나타낸 도면이다.1A is a diagram schematically showing a crystal structure of a layered LiCoAs, an intermediate manufactured according to the method of manufacturing a layered CoAs according to the present invention.
도 1a를 참고하면, 상기 층상형 LiCoAs 화합물의 결정 구조는 층상형 결정구조로서, CoAs 화합물이 층상형 구조를 이루고 있고, 각 CoAs 층의 사이에Referring to FIG. 1A, the crystal structure of the layered LiCoAs compound is a layered crystal structure, and the CoAs compound has a layered structure, and between each CoAs layer
Li 이온층이 개재된 형태를 하고 있을 수 있다. 이와 같은 구조를 하고 있음으로써 이후 단계에서 Li 이온만을 선택적으로 제거하였을 경우 층상형 CoAs를 수득할 수 있다.The Li ion layer may be interposed. With such a structure, when only Li ions are selectively removed in a later step, a layered CoAs can be obtained.
만일 리튬, 코발트 및 비소 분말을 동시에 열처리하여 반응시키지 않고 코발트 및 비소만을 먼저 반응시키는 경우 벌크형 CoAs가 생성되고, 따라서 층상형 LiCoAs를 얻을 수 없으므로 본 발명에 따른 층상형 CoAs를 제조하고자 하는 목적을 제대로 달성할 수 없다.If lithium, cobalt, and arsenic powders are not reacted by heat treatment at the same time and only cobalt and arsenic are reacted first, bulk CoAs is produced, and thus layered LiCoAs cannot be obtained, so that the purpose of preparing the layered CoAs according to the present invention is properly achieved. Cannot be achieved.
본 발명의 바람직한 일 실시예에 따르면, 상기 CoAs 층과 Li 층은 서로 이온 결합에 의하여 결합되어 있는 것일 수 있다. 이온 결합을 이루고 있음으로써 용매 처리 시 용매 분자와 각 층간의 인력 차이로 인하여 Li 이온만을 선택적으로 제거하는 것이 용이하다. 이 경우 CoAs 층에는 결정 구조의 변화가 일어나지 않고 층상형 CoAs 화합물을 수득하는 것이 가능하다. 만일 공유결합을 이루고 있는 경우 용매 처리만으로 Li 이온을 선택적으로 제거하는 것이 어려울 수 있다.According to a preferred embodiment of the present invention, the CoAs layer and the Li layer may be bonded to each other by an ionic bond. Since ionic bonds are formed, it is easy to selectively remove only Li ions due to the difference in attractive force between the solvent molecules and each layer during solvent treatment. In this case, it is possible to obtain a layered CoAs compound without changing the crystal structure of the CoAs layer. If a covalent bond is formed, it may be difficult to selectively remove Li ions only by solvent treatment.
다음으로, (2) 단계에서는 상기 (1) 단계에 이어 제조된 층상형 LiCoAs 화합물에 포함된 Li 이온을 선택적으로 제거하는 단계를 수행한다. 상기 층상형 화합물에 포함된 Li 이온은 Li 이온과의 반응성이 큰 용매를 처리하여 선택적으로 제거되며, 이러한 용매는 물(H2O), C1~C4의 선형 또는 분지형의 알코올 중에서 선택된 적어도 하나를 포함하는 것일 수 있다. 좀 더 바람직하게는, 상기 용매는 물, 에탄올 및 이소프로판올 중에서 선택된 적어도 하나, 더욱 바람직하게는 물을 포함하는 것일 수 있다.Next, in step (2), a step of selectively removing Li ions contained in the layered LiCoAs compound prepared following step (1) is performed. Li ions contained in the layered compound are selectively removed by treating a solvent having a high reactivity with Li ions, and such a solvent includes at least one selected from water (H2O) and a linear or branched alcohol of C1 to C4. It can be. More preferably, the solvent may include at least one selected from water, ethanol and isopropanol, more preferably water.
이 때, 물은 탈이온수(D.I. water)를 사용하는 것이 보다 바람직하다.At this time, it is more preferable to use deionized water (D.I. water).
상기 (2) 단계의 용매 처리는 상기 알칼리 금속 이온 즉, Li 이온의 제거 반응이 원활하게 일어날 수 있는 온도에서 수행될 수 있으며, 상기 혼합용액의 조성에 따라 온도가 달라질 수 있으나, 바람직하게는 20℃ 이상의 온도, 더욱 바람직하게는 20℃ 내지 60℃의 온도에서 수행될 수 있다. 만일 20℃ 미만에서 수행될 경우, 알칼리 금속 이온이 목적하는 수준으로 제거되지 않거나 제조되는 층상형 화합물의 층상형 구조가 붕괴될 수 있고, 60℃를 초과하는 온도에서 수행될 경우 제조되는 층상형 화합물의 층상형 구조가 붕괴될 수 있다. 또한, 20℃ 내지 60℃의 온도에서 수행될 경우 제조되는 층상형 화합물의 층상형 구조를 유지하면서 알칼리 금속 이온 제거율이 우수할 수 있다.The solvent treatment in step (2) may be performed at a temperature at which the removal reaction of the alkali metal ions, that is, Li ions, can occur smoothly, and the temperature may vary depending on the composition of the mixed solution, but preferably 20 It can be carried out at a temperature of more than ℃ ℃, more preferably at a temperature of 20 ℃ to 60 ℃. If performed at less than 20°C, alkali metal ions may not be removed to the desired level or the layered structure of the prepared layered compound may collapse, and when performed at a temperature exceeding 60°C, the prepared layered compound The layered structure of can collapse. In addition, when performed at a temperature of 20°C to 60°C, the alkali metal ion removal rate may be excellent while maintaining the layered structure of the layered compound to be prepared.
또한, 상기 용매 처리는 약 2일 내지 4일간 수행하는 것이 바람직하다. 2일 이내로 수행하는 경우, Li 이온이 충분히 제거되지 않을 수 있고, 생산성 향상을 위하여서는 4일을 초과하지 않는 것이 바람직하다.In addition, the solvent treatment is preferably performed for about 2 to 4 days. If performed within 2 days, Li ions may not be sufficiently removed, and it is preferable not to exceed 4 days in order to improve productivity.
또한, 상기 (2) 단계는 상기 혼합용액의 조성, Li 이온의 제거율에 따라 복수 회 실시할 수 있으나, 제조되는 층상형 CoAs의 층상형 구조를 유지하기 위해 1회 실시하는 것이 바람직하다.In addition, step (2) may be performed multiple times depending on the composition of the mixed solution and the removal rate of Li ions, but is preferably performed once to maintain the layered structure of the layered CoAs to be prepared.
다음으로, 본 발명의 제조방법에 따라 제조된 층상형 CoAs 화합물에 대하여 설명한다.Next, a layered CoAs compound prepared according to the production method of the present invention will be described.
본 발명은 상술한 제조방법에 따라 제조된, 공간군(space group)이 P4/nmm이고 결정계(crystal system)가 정방정계(tetragonal)인 층상형 결정구조를 가지는 층상형 CoAs 화합물을 제공한다.The present invention provides a layered CoAs compound having a layered crystal structure in which a space group is P4/nmm and a crystal system is tetragonal, prepared according to the above-described manufacturing method.
도 1b는 본 발명의 바람직한 일실시예에 따른 층상형 CoAs 화합물의 결정 구조를 개략적으로 나타낸 도면이다. 도 1b를 참고하면, 도 1a에 나타난 LiCoAs의 결정 구조에서와 같이 CoAs로 이루어진 층상의 결정 구조가 나타나며, 이는 종래의 CoAs가 가지는 3D 벌크형의 결정 구조와는 상이함을 알 수 있다.1B is a diagram schematically showing a crystal structure of a layered CoAs compound according to an embodiment of the present invention. Referring to FIG. 1B, as in the LiCoAs crystal structure shown in FIG. 1A, a layered crystal structure made of CoAs is shown, which is different from the 3D bulk crystal structure of the conventional CoAs.
이와 같이 2D 층상형의 결정 구조를 가짐으로써 본 발명의 CoAs 화합물은 종전의 3D 벌크형 결정 구조를 갖는 CoAs 화합물에 비하여 나노 시트로 용이하게 박리될 수 있으며, 밴드 구조를 조정할 수 있고, 전기 전도도 및 전자 이동도한 효과가 있다.By having a 2D layered crystal structure as described above, the CoAs compound of the present invention can be easily peeled into a nanosheet compared to a CoAs compound having a conventional 3D bulk crystal structure, and the band structure can be adjusted, and the electrical conductivity and electron Movement is also effective.
구체적으로, 본 발명에 따른 층상형 CoAs 화합물은 Cu-Ka선을 이용한 분말 X선 회절법에 의하여 얻어지는 X선 회절도에 있어서, 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2 및 60.1±0.1의 2θ 값에서 피크를 가질 수 있다.Specifically, the layered CoAs compound according to the present invention is 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9 in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays. It can have peaks at 2θ values of ±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2, and 60.1±0.1.
또한, 본 발명의 일 실시상태에 따르면, 상기 층상형 CoAs 화합물의 Cu-Ka 선을 이용한 분말 X선 회절법에 의하여 얻어지는 X선 회절도에 있어서, 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2 및 58.9±0.2의 2θ 값에서 피크를 갖지 않을 수 있다.In addition, according to an exemplary embodiment of the present invention, in the X-ray diffraction diagram obtained by powder X-ray diffraction using Cu-Ka rays of the layered CoAs compound, 42.9±0.2, 52.8±0.2, 53.6±0.2, It may not have peaks at 2θ values of 54.1±0.2 and 58.9±0.2.
도 5는 본 발명에 따른 층상형 CoAs 화합물, 상기 (1) 단계에서 제조된 층상형 LiCoAs 화합물 및 LiCoAs의 레퍼런스 XRD 피크 및 종래 3D 벌크 결정 구조를 갖는 CoAs 화합물의 XRD 피크를 비교한 도면이다.5 is a view comparing XRD peaks of the layered CoAs compound according to the present invention, the reference XRD peaks of the layered LiCoAs compound and LiCoAs prepared in step (1), and the CoAs compound having a conventional 3D bulk crystal structure.
본 발명에 따른 층상형 CoAs의 XRD 데이터에 따르면, 14.5±0.2,27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2 및 60.1±0.1의 2θ 값에서 피크를 가짐을 확인할 수 있고, 반대로 3D 벌크 결정 구조를 갖는 CoAs의 XRD 데이터는 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2 및 58.9±0.2의 2θ 값에서 피크를 가짐에 반하여 본 발명에 따른 층상형 CoAs는 상기 2θ 값에서 피크를 가지지 않는 것을 확인할 수 있어, 종래 3D 벌크 결정 구조를 갖는 CoAs 화합물과 상이한 결정 구조를 갖는다는 것을 알 수 있다.According to the XRD data of the layered CoAs according to the present invention, 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2 and 60.1 It can be seen that it has a peak at a 2θ value of ±0.1, and on the contrary, the XRD data of CoAs with a 3D bulk crystal structure peak at 2θ values of 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2, and 58.9±0.2. On the other hand, it can be seen that the layered CoAs according to the present invention does not have a peak at the 2θ value, and it can be seen that it has a crystal structure different from the conventional CoAs compound having a 3D bulk crystal structure.
다음으로, 본 발명에 따른 CoAs 나노시트에 대하여 설명한다.Next, the CoAs nanosheet according to the present invention will be described.
본 발명에 따른 CoAs 나노시트는 본 발명에 따른 층상형 CoAs 화합물로부터 박리되어 수득할 수 있으며, 공간군(space group) 이 P4/nmm이며, 결정계(crystal system)가 정방정계(tetragonal)인 층상형 결정구조를 가짐으로써 갖는 효과에 대한 내용은 상술한 층상형 CoAs에 대한 내용과 동일하므로 생략한다.The CoAs nanosheet according to the present invention can be obtained by peeling from the layered CoAs compound according to the present invention, and the space group is P4/nmm, and the crystal system is tetragonal. The details of the effect of having a crystal structure are the same as those of the above-described layered CoAs, and thus will be omitted.
상기 CoAs 나노시트는 상술한 층상형 CoAs 화합물로부터 박리되어 제조될 수 있으며, 박리하는 방법은 당업계에서 공지된 층상형 물질의 박리 방법 중에서 선택될 수 있으며, 예를 들어, 초음파에 의한 에너지로 박리하는 방법, 용매의 침입에 의한 박리 방법, 테이프를 이용한 박리 방법 및 접착성 표면을 가진 물질을 이용한 박리 방법 중 어느 하나의 방법을 사용할 수 있다.The CoAs nanosheet may be prepared by peeling from the layered CoAs compound described above, and the method for peeling may be selected from peeling methods for layered materials known in the art, for example, peeling by energy by ultrasonic waves. Any one of a method of performing, a peeling method by intrusion of a solvent, a peeling method using a tape, and a peeling method using a material having an adhesive surface may be used.
본 발명의 일 실시예에 있어서, 상기 CoAs 나노시트는 두께가 30nm 이하일 수 있다. 상기와 같은 얇은 두께를 가짐으로써 넓은 표면적을 갖고, 추가적인 과정에 의하여 밴드 구조의 조절이 가능하고, 종래의 3D 벌크 CoAs 화합물에 비하여 더욱 전자이동도 및 전기전도도가 우수하다.In an embodiment of the present invention, the CoAs nanosheet may have a thickness of 30 nm or less. By having such a thin thickness, it has a large surface area, the band structure can be adjusted by an additional process, and electron mobility and electrical conductivity are more excellent than that of the conventional 3D bulk CoAs compound.
또한, 본 발명은 상기 층상형 CoAs 또는 CoAs 나노시트를 포함하는 열전소자, 광전자소자 및 반도체 소자를 제공한다.In addition, the present invention provides a thermoelectric device, an optoelectronic device, and a semiconductor device including the layered CoAs or CoAs nanosheet.
상기 열전소자는 상기 층상형 CoAs 또는 CoAs 나노시트의 우수한 전기전도도로 인하여 높은 Seebeck 상수를 갖는다.The thermoelectric device has a high Seebeck constant due to the excellent electrical conductivity of the layered CoAs or CoAs nanosheet.
이상에서 본 발명의 일 실시예에 대하여 설명하였으나, 본 발명의 사상은 본 명세서에 제시되는 실시예에 제한되지 아니하며, 본 발명의 사상을 이해하는 당업자는 동일한 사상의 범위 내에서, 구성요소의 부가, 변경, 삭제, 추가 등에 의해서 다른 실시예를 용이하게 제안할 수 있을 것이나, 이 또한 본 발명의 사상범위 내에 든다고 할 것이다.Although an embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments presented in the present specification, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same idea. Other embodiments may be easily proposed by changes, deletions, additions, etc., but it will be said that this is also within the scope of the present invention.
[실시예][Example]
준비예 1 - 층상형 LiCoAs의 제조Preparation Example 1-Preparation of layered LiCoAs
정량의 Li 분말, Co 분말 및 As 분말을 동시에 혼합한 후, 불활성 기체 분위기의 쿼츠 튜브에 봉입하였다. 시료가 담긴 쿼츠 튜브를 850℃에서 2일간 열처리하였다. 이후, LiCoAs의 재결정화를 위하여 1.5℃의 감온 속도로 냉각하여 공간군(space group)이 P4/nmm인 정방정계(tetragonal)인 결정구조를 포함하는 LiCoAs를 수득하였다.After mixing quantitative Li powder, Co powder and As powder at the same time, it was sealed in a quartz tube in an inert gas atmosphere. The quartz tube containing the sample was heat-treated at 850° C. for 2 days. Thereafter, for recrystallization of LiCoAs, it was cooled at a temperature reduction rate of 1.5° C. to obtain LiCoAs having a tetragonal crystal structure having a space group of P4/nmm.
실시예 1 - 층상형 CoAs 화합물의 제조Example 1-Preparation of a layered CoAs compound
준비예 1에서 제조된 LiCoA를 탈이온수와 혼합하여 3일간 반응시켜 상기 LiCoAs에서 Li 이온을 제거하였으며, 이를 통해 공간군이 P4/nmm이고 결정계가 정방정계인 층상형 CoAs 화합물을 제조하였다.LiCoA prepared in Preparation Example 1 was mixed with deionized water and reacted for 3 days to remove Li ions from the LiCoAs, through which a layered CoAs compound having a space group of P4/nmm and a crystal system of a tetragonal system was prepared.
실시예 2 - CoAs 나노시트의 제조Example 2-Preparation of CoAs nanosheets
실시예 1에서 제조된 층상형 CoAs를 스카치 테이프(3M)로 박리하여 CoAs 나노시트를 제조하였다.The layered CoAs prepared in Example 1 was peeled off with a scotch tape (3M) to prepare a CoAs nanosheet.
비교예 1 - 3D 벌크 결정구조를 갖는 CoAs 화합물의 제조Comparative Example 1-Preparation of a CoAs compound having a 3D bulk crystal structure
Co 분말과 As 분말을 950℃에서 120시간 동안 열처리한 후 냉각하여 3D 벌크형 CoAs 화합물을 제조하였다.Co powder and As powder were heat-treated at 950° C. for 120 hours and then cooled to prepare a 3D bulk CoAs compound.
[실험예][Experimental Example]
실험예 1 - XRD 분석Experimental Example 1-XRD analysis
준비예 1 및 실시예 1에 따라 제조된 시료들에 대하여 XRD 분석을실시하였으며, 그 결과를 도 5에 도시하였다. 도 5에는 종래 기술에 따라 제조된 LiCoAs의 XRD 분석 결과를 참고로서 함께 도시(LiCoAs reference)하였으며, 비교예 1에 따라 제조된 3D 벌크형 CoAs의 XRD 피크 또한 함께 도시하였다.XRD analysis was performed on the samples prepared according to Preparation Example 1 and Example 1, and the results are shown in FIG. 5. In FIG. 5, the XRD analysis results of LiCoAs prepared according to the prior art are shown together as a reference (LiCoAs reference), and the XRD peaks of 3D bulk CoAs prepared according to Comparative Example 1 are also shown.
도 5를 참조하면 본 발명에 따라 제조된 실시예 1의 층상형 CoAs(1Q-CoAs)의 XRD 회절 패턴은 종래의 3D 벌크 결정구조를 갖는 CoAs 화합물과는 상이하다는 것을 확인할 수 있다. 이로부터, 그 결정 구조가 상이하다는 것을 알 수 있다.Referring to FIG. 5, it can be seen that the XRD diffraction pattern of the layered CoAs (1Q-CoAs) of Example 1 prepared according to the present invention is different from the conventional CoAs compound having a 3D bulk crystal structure. From this, it can be seen that the crystal structure is different.
실험예 2 - SEM 분석Experimental Example 2-SEM analysis
준비예 1 및 실시예 1에 따라 제조한 시료들의 SEM 이미지를 촬영하였으며, 그 결과를 도 3a 및 도 3b에 도시하였다.SEM images of the samples prepared according to Preparation Example 1 and Example 1 were taken, and the results are shown in FIGS. 3A and 3B.
실험예 3 - STEM 분석Experimental Example 3-STEM analysis
실시예 2에 따라 제조된 시료에 대한 STEM 분석을 실시하여 그 결과를 도 7에 도시하였다.STEM analysis was performed on the sample prepared according to Example 2, and the results are shown in FIG. 7.
도 7을 참조하면, LiCoAs 화합물의 Li 이온이 제거된 후 CoAs 화합물에는 정방정계의 CoAs 층만이 남아 층상의 결정 구조를 갖는 것을 확인할 수 있었다.Referring to FIG. 7, it was confirmed that after the Li ions of the LiCoAs compound were removed, only the tetragonal CoAs layer remained in the CoAs compound to have a layered crystal structure.
실험예 4 - AFM 분석Experimental Example 4-AFM analysis
실시예 2에 따른 CoAs 나노시트에 대하여 AFM 분석을 실시하였으며, 그 결과를 도 6에 도시하였다.AFM analysis was performed on the CoAs nanosheets according to Example 2, and the results are shown in FIG. 6.
도 6을 참조하면, 실시예 2에 따른 CoAs 나노시트는 30nm 이하의 두께로 박리되었다는 것을 확인할 수 있다.Referring to FIG. 6, it can be seen that the CoAs nanosheet according to Example 2 was peeled to a thickness of 30 nm or less.

Claims (14)

  1. (1) 리튬(Li) 분말; 코발트(Co) 분말 및 비소(As) 분말을 혼합한 후 열처리 및 냉각하여 공간군(space groups)이 P4/nmm이고 결정계(crystal system)가 정방정계(tetragonal)인 층상형 결정구조를 가지며, 화학식 LiCoAs로 표시되는 층상형 화합물을 합성하는 단계; 및(1) lithium (Li) powder; Cobalt (Co) powder and arsenic (As) powder are mixed and then heat treated and cooled to have a layered crystal structure in which the space groups are P4/nmm and the crystal system is tetragonal. Synthesizing a layered compound represented by LiCoAs; And
    (2) 상기 층상형 화합물에 포함된 Li 이온을 선택적으로 제거할 수 있는 용매를 처리하여 상기 층상형 LiCoAs 화합물의 결정구조 변화 없이 층상형 CoAs 화합물을 제조하는 단계;를 포함하는 층상형 CoAs 화합물의 제조방법.(2) preparing a layered CoAs compound without changing the crystal structure of the layered LiCoAs compound by treating a solvent capable of selectively removing Li ions contained in the layered compound; Manufacturing method.
  2. 제1항에 있어서,The method of claim 1,
    상기 (1) 단계에서 합성된 층상형 화합물은 CoAs의 다층 구조를 갖고 상기 각 CoAs 층 사이에 Li 층이 개재되어 있으며, 인접한 CoAs 층과 Li 층은 서로 이온 결합에 의하여 결합되어 있는 것을 특징으로 하는 층상형 CoAs 화합물의 제조방법.The layered compound synthesized in step (1) has a multilayer structure of CoAs, and a Li layer is interposed between each of the CoAs layers, and the adjacent CoAs layer and the Li layer are bonded to each other by ionic bonds. Method for producing a layered CoAs compound.
  3. 제1항에 있어서,The method of claim 1,
    상기 용매는 물(H2O); 및 C1~C4의 선형 또는 분지형 알코올 중에서 선택된 적어도 하나를 포함하는 것을 특징으로 하는 층상형 CoAs 화합물의 제조방법.The solvent is water (H 2 O); And at least one selected from C 1 to C 4 linear or branched alcohols.
  4. 제1항에 있어서,The method of claim 1,
    상기 (1) 단계의 열처리는 700℃ 내지 1,000℃의 온도에서 2일(days) 내지 7일 동안 수행하는 것을 특징으로 하는 층상형 CoAs 화합물의 제조방법.The heat treatment in step (1) is a method for producing a layered CoAs compound, characterized in that it is performed for 2 to 7 days at a temperature of 700°C to 1,000°C.
  5. 제1항에 있어서,The method of claim 1,
    상기 (1) 단계의 냉각은 0.5℃/h 내지 3.0℃/h의 감온 속도로 수행되는 것을 특징으로 하는 층상형 CoAs 화합물의 제조방법.The cooling in step (1) is a method for producing a layered CoAs compound, characterized in that it is carried out at a temperature reduction rate of 0.5 ℃ / h to 3.0 ℃ / h.
  6. 제1항에 있어서,The method of claim 1,
    상기 (2) 단계의 용매 처리는 20℃ 내지 60℃의 온도에서 수행되는 것을 특징으로 하는 층상형 CoAs 화합물의 제조방법.The method for producing a layered CoAs compound, characterized in that the solvent treatment in step (2) is performed at a temperature of 20°C to 60°C.
  7. 공간군이 P4/nmm이고 결정계가 정방정계인 층상형 결정구조를 가지는 층상형 CoAs 화합물.A layered CoAs compound having a layered crystal structure in which the space group is P4/nmm and the crystal system is a tetragonal system.
  8. 제7항에 있어서,The method of claim 7,
    상기 층상형 CoAs 화합물은 Cu-Ka선을 이용한 분말 X선 회절법에 의하여 얻어지는 X선 회절도에 있어서, 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2, 48.4±0.2, 50.9±0.2, 56.9±0.2 및 60.1±0.2의 2θ 값에서 피크를 갖는 것을 특징으로 하는 층상형 CoAs 화합물.The layered CoAs compound is 14.5±0.2, 27.8±0.2, 33.7±0.2, 36.9±0.2, 37.9±0.2, 45.2±0.2 in X-ray diffraction diagrams obtained by powder X-ray diffraction using Cu-Ka rays. , 48.4±0.2, 50.9±0.2, 56.9±0.2, and 60.1±0.2. The layered CoAs compound, characterized in that it has peaks at 2θ values.
  9. 제7항에 있어서,The method of claim 7,
    상기 층상형 CoAs 화합물은 Cu-Ka선을 이용한 분말 X선 회절법에 의하여 얻어지는 X선 회절도에 있어서, 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2 및 58.9±0.2의 2θ 값에서 피크를 갖지 않는 것을 특징으로 하는 층상형 CoAs 화합물.In the X-ray diffraction diagram obtained by powder X-ray diffraction method using Cu-Ka ray, the layered CoAs compound at 2θ values of 42.9±0.2, 52.8±0.2, 53.6±0.2, 54.1±0.2, and 58.9±0.2. A layered CoAs compound, characterized in that it does not have a peak.
  10. 제7항에 따른 층상형 CoAs 화합물로부터 박리되고, 공간군이 P4/nmm이며, 정방정계 결정계의 층상형 결정구조를 갖는 CoAs 나노시트.Separated from the layered CoAs compound according to claim 7, the space group is P4/nmm, and the CoAs nanosheet has a layered crystal structure of a tetragonal crystal system.
  11. 제10항에 있어서,The method of claim 10,
    두께가 30nm 이하인 것을 특징으로 하는 CoAs 나노시트.CoAs nanosheet, characterized in that the thickness is less than 30nm.
  12. 제7항에 따른 층상형 CoAs 화합물 또는 청구항 10에 따른 CoAs 나노시트를The layered CoAs compound according to claim 7 or the CoAs nanosheet according to claim 10
    포함하는 열전소자.A thermoelectric element including.
  13. 제7항에 따른 층상형 CoAs 화합물 또는 청구항 10에 따른 CoAs 나노시트를 포함하는 광전자소자.An optoelectronic device comprising the layered CoAs compound according to claim 7 or the CoAs nanosheet according to claim 10.
  14. 제7항에 따른 층상형 CoAs 화합물 또는 청구항 10에 따른 CoAs 나노시트를 포함하는 반도체소자.A semiconductor device comprising the layered CoAs compound according to claim 7 or the CoAs nanosheet according to claim 10.
PCT/KR2020/011187 2019-09-16 2020-08-21 Method for preparing layered cobalt arsenide, layered cobalt arsenide prepared thereby, and cobalt arsenide nanosheet exfoliated therefrom WO2021054628A1 (en)

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