JPH07136498A - Production of fullerene intercalation compound - Google Patents

Abstract

PURPOSE:To easily synthesize an intercalation compd. with fullerene and other element by separately introducing fullerene and other element intercalating fullerene into the area above a substrate or a reaction container stoichiometrically in a gas phase state to mix both of them and heating the resulting mixture. CONSTITUTION:Purified C60 is put in a heating resistor cell 16A and lanthanum is put in an electron beam vapor deposition cell 16B. After a vacuum chamber 10 is reduced to 10<-7>Torr, Co60 and lanthanum are introduced into a reaction container 12 held to 200 deg.C in such a state that cell temp. is about 400 deg.C, acceleration voltage is 4kV and an emission current is 100mA so that the ratio of Co60 and lanthanum becomes a stoichiometric ratio of 1:3. The obtained product is heat-treated at 50 deg.C under an argon atmosphere of 10 atm. for two days.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an intercalation compound of fullerene and another element.

[0002]

C ₆₀ is a new substance in which 60 carbon atoms are gathered in a soccer ball shape, and was discovered in 1985 by Kuroto et al. In addition, this substance was discovered in 1990 by Kletschmer and the like, and its practical application is expected. Further, as a similar new form of carbon, in addition to C ₆₀ in which 60 carbons are assembled, C ₇₀ in which ₇₀ carbon atoms are assembled and a series of C _n substances in which more carbon atoms are assembled have been found. These new substances are collectively called fullerenes.

The fullerene solid is generally a semiconductor, and among them, the C ₆₀ substance is expected to have various physical properties due to its symmetry. For example, applications to light-emitting devices that utilize the photoelectric effect of this material, to photoconductors for printers, and conductors or superconductors that use intercalation compounds with alkali metals or alkaline earth metals will be the next generation. Has shown many possibilities as a new material. In addition, fullerene has a size in the nm region, and is expected to be applied to new applications by utilizing phenomena such as optical confinement or electron confinement in the quantization region or the mesoscopic region as compared with conventional materials.

[0004]

Thus, fullerenes such as C ₆₀ have been attracting attention as attractive new materials, but fullerenes themselves are basically cluster molecules having a closed shell electronic structure. In order to exhibit electronic or magnetic properties, it is necessary to introduce electrons or holes as carriers into the fullerene by utilizing intercalation with other elements. For such a purpose, as a method of producing an intercalation compound, a method of mixing a fullerene and a material containing another element and then performing thermal diffusion has been used so far. However, in such a method, an intercalation compound with an alkali metal or an alkaline earth metal can be formed, but an intercalation compound with another element cannot be formed under the present circumstances. Further, even in the case of an intercalation compound with an alkali metal or an alkaline earth metal, many crystal phases are formed during the synthesis, so that it is difficult to form a desired crystal phase.

An object of the present invention is to provide a production method capable of easily synthesizing an intercalation compound of fullerene and another element.

[0006]

The method for producing a fullerene intercalation compound according to the first aspect of the present invention is characterized in that the fullerene (C _{60 or} C ₇₀ ) and the intercalation material are separately provided in a cell provided in a vacuum chamber. After evaporating while controlling the amount of flux in a vacuum, vaporize it on the reaction substrate provided facing the cell or introduce it into the reaction container and mix, and heat this reaction substrate or reaction container. It is characterized by doing.

The method for producing the fullerene intercalation compound of the second invention is such that fullerene (C ₆₀ or C ₇₀ ) and the intercalation material are separately put in a cell provided in a vacuum chamber, and then in a vacuum. Evaporate while controlling the amount of flux, vapor deposit on the reaction substrate provided facing the cell or introduce into the reaction container and mix, and heat this reaction substrate or reaction container in an inert gas atmosphere. It is characterized by that.

[0008]

FUNCTION The solid crystal of fullerene has a matrix crystal system determined by its shape. For example, C ₆₀ crystal exhibits a crystal system called face-centered cubic. The distance between the fullerene cluster molecules in the crystal, that is, the size of the lattice gap, is determined by each crystal system. Therefore, in principle, an intercalation compound with an element having an element radius larger than the lattice gap of the original crystal system cannot be produced. In fact, it is extremely difficult to make an intercalation compound of C ₆₀ with an element such as silicon or tin, and it is no exaggeration to say that it is almost impossible.
Furthermore, taking the 4a to 7a group elements of the 4th period or the 8th group elements of the 4th period as well, these metals have d-electrons, so they are very interesting candidates for intercalation compounds from the viewpoint of magnetic materials. However, the conventional method requires extremely high heat treatment, and since these elements often form a carbide compound with carbon, it has been impossible to produce a C ₆₀ intercalation compound so far. Also, in combination with the elements that make up the intercalation compound, some kinds of crystal phases having various compositions may coexist. For example, in the case of K ₃ C ₆₀ , which is an intercalation compound of potassium and C ₆₀ known as a metal, in the conventional production method, a body-centered tetragonal K ₄ C ₆₀ and a body phase which are crystal phases having different compositions at the same time are obtained. Due to the simultaneous coexistence of the cubic cubic K ₆ C ₆₀ , the synthesis had to take great care.

As a result of various investigations on such a problem, the inventors of the present invention have found that other elements for intercalating C ₆₀ or C ₇₀ fullerenes and the stoichiometry of each on the substrate or in the reaction vessel are different from each other. The inventors have found that intercalation compounds of fullerenes and various elements can be produced by introducing them in a vapor phase state, mixing them, and applying heat to produce intercalation compounds. For example, C ₆₀ and intercalation conventional method with silicon, i.e. C ₆₀ and in the method of the silicon mixed with heat-treated in an inert gas atmosphere or ^10-6
The intercalation compound could not be synthesized even by heat treatment at 1000 ° C. under reduced pressure of Torr, but it can be synthesized by the method of the present invention. In the conventional method, this is C
₆₀ silicon atomic radius to the grating gap _crystal (0.1
89 nm), it is difficult to form an intercalation compound, but according to the method of the present invention, C
It is considered successful because ₆₀ cluster molecules and the silicon element collide and react to form an intercalation compound in the solid state. The heat treatment temperature is 8
The low temperature of 00 ° C was good.

Further, according to the method of the present invention, even in the case of the element of the 4th period in which the production of the C ₆₀ intercalation compound is inhibited due to the formation of carbide, etc., since it is mixed in the gas phase, The heat treatment process is extremely low,
It can be lower than the carburite formation temperature For this reason, it was found that it is possible to form a metastable intercalation compound that can prevent thermal equilibrium from proceeding to the most stable compound, carbide. Also, potassium and C
_{Even in the case of 60} intercalation compounds, in order to synthesize them by controlling the stoichiometric ratio from different evaporation sources, the amount of potassium should be controlled to 3: 1 with respect to the amount of C _60. Only the cubic K ₃ C ₆₀ metal phase could be produced stably and at low temperature. It is considered that this is because the homogeneity was remarkably controlled as compared with the reaction between bulk C ₆₀ and bulk potassium.

Among the elements used to make the intercalation compound, alkali metals include lithium, sodium, potassium, rubidium and cesium. In this case, since the vapor pressures of these elements are extremely high, it is necessary to return the pressure to normal pressure in an inert gas atmosphere once after evaporative mixing, and then perform heat treatment at 100 to 400 ° C. The reaction does not proceed at 100 ° C or lower, and re-desorption occurs at 400 ° C or higher. As alkaline earth elements,
There are calcium, strontium, and barium. It has been found that in the case of these elements, the vapor pressure is not so high that the heat treatment needs to be set to a high temperature of 10 ^{-2 to} 300 Torr in an inert gas and a heat treatment temperature of 400 to 1000 ° C. As rare earth elements, lanthanum,
Examples include cerium, samarium, gadolinium, and ytterbium. When making intercalation with these elements, 700 ° C under the pressure of inert gas.
From the above, it was found that heat treatment was necessary. Examples of the 4b group element of the periodic table include silicon, germanium, tin and lead. Intercalation with these elements has been found to be very effective in treating the gas phase mixture from the evaporation source simultaneously in the reaction vessel.
In particular, it has been found that silicon can form C ₆₀ and intercalation with high purity by evaporative mixing. This seems to be correlated with the fact that C ₆₀ is in a hybrid bond state of sp ² and sp ³ and that the silicon element easily adopts these bond modes. Fourth cycle 4a, 5a, 6
As the elements of a and 7a or the elements of the 4th period 8 group,
There are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, etc. It was found that the heat treatment temperature for these elements needs to be sufficiently lower than the carbide formation temperature because these elements easily form carbide with carbon.

Further, it has been found that the C ₆₀ intercalation compound using any one of copper, zinc, cadmium, mercury, or a mixture thereof is suitable for the evaporative mixing method, and a high quality intercalation compound can be produced. . This is because these elements and fullerenes, especially C ₆₀
It is considered that this is because the transfer of charges between and occurs very smoothly. In addition, scandium, yttrium,
Alternatively, in the case of lanthanum, it has been found that it is very effective to supply vapor deposition raw materials in the form of these halides and evaporate and mix.

The temperature range of the heat treatment varies depending on the type of element used and the type of fullerene, but since it has already been mixed to some extent in the gas phase, it is generally 100 to 1000.
In the range of ° C, it is possible to use much lower temperature than before. In addition, the mixing speed also varies depending on the combination used, but generally 0.1 to
A deposition rate range of 100 nm / min is preferred. This is because if it is slower than this, it is not practical, and if it is too fast, the mixing becomes uneven. In addition, the heat treatment is preferable after mixing and during mixing, but during mixing is preferable because heat uniformity is maintained.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of a manufacturing apparatus used in an embodiment of the present invention.

In FIG. 1, a reaction chamber 12 or a reaction substrate 13 heated by a heater 11 connected to a heating power source 14 is provided in a vacuum chamber 10. In the vacuum chamber 10 facing the reaction container 12, a plurality of cells (heating resistance cells or electron beam vapor deposition cells) 16A to be heated by the vapor deposition power source 17 are provided.
16C is provided, and a flux monitor system 18 for controlling the amount of flux is provided between the cell and the reaction vessel. Reference numeral 15 is an exhaust system including a turbo pump, a rotary pump, and the like, and 19 is a pressure control system having a variable valve, an introduction pipe of an inert gas such as argon, and the like.

The fullerene used in the examples is 100 Tor.
It was prepared by using a carbon rod having a diameter of 10 mm as a negative electrode and a carbon rod having a diameter of 6 mm as a positive electrode in a helium atmosphere of r and discharging at 20 V DC. After the experiment, C ₆₀ and C ₇₀ contained in the soot were separated and purified by a column having alumina as a packing material using hexane / toluene as a developing solvent.

As Example 1, purified C ₆₀ was placed in the heating resistance cell 16A, and lanthanum was placed in the other cell 16B for electron beam evaporation. And the vacuum chamber 10
After reducing the pressure to 10 ^-7 Torr, add C ₆₀ to the cell temperature of about 40
Lanthanum was introduced into the reaction vessel 12 kept at 200 ° C. at an accelerating voltage of 4 kV and an emission current of 100 mA at 0 ° C. so that the ratio of C ₆₀ to lanthanum was 1: 3. The product was heated to 50 at 10 atm under an argon atmosphere.
Heat treatment was performed at 0 ° C. for 2 days. When the produced compound was measured by X-ray diffraction, a face-centered cubic intercalation compound having a lattice spacing of 1.46 nm was obtained.

The same experiment as Comparative Example 1 was carried out in the same manner as in Comparative Example 1, except that C ₆₀ and lanthanum element were mixed at a stoichiometric ratio of 1: 3, sealed, and heat treated at 1000 ° C. for 2 days. Take out X-
As a result of line analysis, C ₆₀ and the lanthanum element did not form intercalation and remained phase separated.

The same experiment as in Example 1 was conducted as Example 2.
The intercalation between C ₆₀ and silicon was performed. In this case, put silicon into the heating resistance cell and
At a temperature of 000 ° C, the ratio of C ₆₀ to silicon is 1: 3.
And mixed by evaporation. The temperature of the reaction vessel is 800
It was kept at 0 ° C throughout the experiment. When the resulting compound was measured by X-ray diffraction, an intercalation compound having a face-centered cubic crystal structure with a lattice radius of 1.45 nm was found.

As Comparative Example 2, the same experiment as in Example 2 was conducted by the conventional method. C ₆₀ and silicon were sealed in a quartz tube, mixed, and reacted at 900 ° C. for 1 week. When the produced product was examined by X-ray analysis, no intercalation compound was produced and phase separation occurred.

As Example 3, potassium, which is an alkali metal, and C ₆₀ were mixed at a ratio of 3: 1 and vapor-deposited from a heating resistance cell on a reaction substrate 13 made of MoS ₂ . The temperature of the substrate was 100 ° C. K ₃ C _{60 Lee} centers intercalation compound corresponding to the lattice constant face-centered cubic structure lattice constant 1.42nm Looking can compounds with reflection high-energy electron diffraction (RHEED) were able.

As Comparative Example 3, the same experiment as in Example 3 was carried out.
After depositing a C ₆₀ thin film to a thickness of 200 nm on the substrate 13 as in the prior art, potassium was deposited at a stoichiometric ratio of 3 with respect to the amount of C ₆₀ and thermally diffused. This is Rhee
When d was observed, it was found that several kinds of crystal phases were mixed.

[0023] The experiment of Example 3 Example 4 Karimuu and C ₆₀ 6 were mixed vapor Ensure a 1 stoichiometric ratio. As a result, it was found by Rheed that a single intercalation compound having a single crystal phase of K ₆ C ₆₀ having a body-centered cubic structure was formed.

In Example 5, barium was used as the alkaline earth metal, and barium and C ₆₀ were controlled from the heating resistance cell at a stoichiometric ratio of 3: 1 and mixed in the gas phase to form a reaction substrate 13.
It was vapor-deposited on. After that, heat treatment was performed at 300 ° C. with the pressure inside the vacuum chamber 10 set to 200 Torr in an argon atmosphere. as a result. The fact that an intercalation compound having an A15 structure of 1.13 nm is prepared is R
Confirmed from head measurements.

C ₆₀ purified as Example 6 was placed in a heating resistance cell, and trichloroyttrium was placed in the other cell for electron beam evaporation. And the vacuum chamber 10
After reducing the pressure to 10 ^-7 Torr, add C ₆₀ to the cell temperature of about 45
Reaction vessel 1 in which trichloroyttrium was kept at 200 ° C at 0 ° C with an acceleration voltage of 4 kV and an emission current of 20 mA.
2 was introduced so that the ratio of C ₆₀ and yttrium was 1: 3. When the produced compound was measured by X-ray diffraction, a face-centered cubic intercalation compound having a lattice spacing of 1.49 nm was obtained.

As Experimental Example 7, purified C60 and nickel, which is a transition metal of the fourth period, were supplied to different deposition cells at 10 _-6 T.
The mixture was evaporated by controlling the stoichiometric ratio of 1: 6 with orr.
The temperature of the reaction vessel 12 was kept at 200 ° C. during the mixing experiment. After that, set to 600 Torr in an argon atmosphere and set to 8
The heat treatment was continued at 00 ° C. for 24 hours. X-ray analysis of the purified compound confirmed that another intercalated crystal phase different from the crystal structure of C ₆₀ was formed.

As Example 8, the same operation as in Example 1 was performed.
Boron, which is a b-group element, was formed using an electron beam evaporation cell. The stoichiometric ratio of C ₆₀ and boron was kept at 1:12, and the reaction vessel 12 was mixed at a temperature of 250 ° C. Then, the reaction was carried out at 900 ° C. for 24 hours under atmospheric pressure under an argon atmosphere. X-ray analysis of the resulting compound confirmed that an intercalation compound having a face-centered cubic structure with a lattice constant of 1.43 nm was formed.

As Example 9, the same operation as in Example 1 was performed using a cell for electron beam evaporation of zinc. Keep the stoichiometric ratio of C ₆₀ and zinc at 1: 6 and keep the temperature of the reaction vessel 12 at 200 ° C.
Were mixed under the following conditions. Then, the reaction was carried out at 500 ° C. for 24 hours under atmospheric pressure under an argon atmosphere. X-ray analysis of the resulting compound confirmed that an intercalation compound having a face-centered cubic structure with a lattice constant of 1.41 nm was formed.

In the above embodiment, C ₆₀ was used as fullerene.
Although the case of using C ₇₀ is explained, even if C ₇₀ is used, C ₆₀
An intercalation compound could be prepared in the same manner as in. In addition to Ar, Ne or the like may be used as the inert gas.

[0030]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to produce intercalation compounds of various foreign elements and fullerenes which could not be obtained by the conventional method.
Such various intercalation compounds are expected to produce various new functional materials having a fullerene as a basic structure, and have extremely high industrial utility.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 10 Vacuum Chamber 11 Heater 12 Reaction Container 13 Reaction Substrate 14 Heating Power Supply 15 Exhaust System 16A-16C Cell 17 Vapor Deposition Power Supply 18 Flux Monitor System 19 Pressure Control System

Claims (9)

[Claims] 1. A fullerene (C _{60 or} C ₇₀ ) and an intercalation material are separately put in a cell provided in a vacuum chamber, and then evaporated in a vacuum while controlling the flux amount, A method for producing a fullerene intercalation compound, which comprises vapor-depositing on a reaction substrate provided facing each other, or introducing the reaction substrate into a reaction container and mixing them, and heating the reaction substrate or reaction container. 2. The method for producing a fullerene intercalation compound according to claim 1, wherein the intercalation material is a substance composed of one element of Group 3b or Group 4b of the periodic table. 3. The intercalation material is a metal consisting of an element of one of the 4th group 4a group, 5a group, 6a group, 7a group or 8 group of the periodic table, and the heating temperature is The method for producing a fullerene intercalation compound according to claim 1, wherein the temperature is not higher than the temperature at which carbon and carbide are formed. 4. The intercalation material is copper, zinc,
The method for producing a fullerene intercalation compound according to claim 1, which is one metal selected from cadmium and mercury or a mixture of these metals. 5. The method for producing a fullerene intercalation compound according to claim 1, wherein the intercalation material is a halide of scandium, yttrium or lanthanum. 6. A fullerene (C ₆₀ or C ₇₀ ) and an intercalation material are separately placed in a cell provided in a vacuum chamber and then evaporated in a vacuum while controlling a flux amount to face the cell. A method for producing a fullerene intercalation compound, characterized in that the reaction substrate or the reaction container is heated in an inert gas atmosphere by vapor deposition on the reaction substrate provided in the reaction container or by introducing it into the reaction container and mixing them. . 7. The fullerene intercalation according to claim 6, wherein the intercalation material is a substance consisting of one element of alkali metals and is heated at 100 to 400 ° C. in an inert gas atmosphere at normal pressure. Method for producing compound. 8. The intercalation material is a substance consisting of one element of alkaline earth, and 10 ^{−2 to} 3
400-100 in an inert gas atmosphere of 00 Torr
The method for producing a fullerene intercalation compound according to claim 6, which comprises heating at 0 ° C. 9. The intercalation material is a substance consisting of one element of rare earths, and is heated at least 700 ° C. in a pressurized inert gas atmosphere.
A method for producing the described fullerene intercalation compound.