JPS61127623A - Synthesizing method of transition metal chalcogen compound - Google Patents

Abstract

PURPOSE:To produce the transition metal chalcogen compds. having an optional composition easily and surely by incorporating the raw material of the transition metal and the raw material of chalcogen in a reaction vessel and allowing the mixture to react while controlling the reaction temp. in the prescribed temp. range in the high pressure. CONSTITUTION:The simple substance of transition metal M and the simple substance of chalcogen X are incorporated nin a reaction vessel and the inside of the vessel is regulated to >=100atm. When the quantity of heat is supplied to the vessel from the outside, the transition metal M and the chalcogen X are started to be allowed to react with each other and the temp. starts to descend, it is reheated to elevate the temp. till the point (b). In this case, when the transition metal chalcogen compd. MX2 is aimed, the temp. of the point (b) is regulated to >=500 deg.C and when the compd. MX3 is aimed, it is regulated to 450-1,000 deg.C. The time (b-c) holding it in this temp. is optionally preset by the aimed particle size.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for synthesizing a transition metal chalcogen compound from a transition metal raw material and a chalcogen raw material under high pressure.

[Prior Art] A transition metal chalcogen compound is a transition metal chalcogen compound containing a transition metal (for example, group II T
1, Zr, Ht, V group V, Nl+, TO1■ group Cr
, Mo, W, etc.), chalcogen (S, se, T
If a) is X, compounds with various compositions such as Ruto, MX4, MX, MX, MX, etc. can be taken, and the formation region of these compounds is the chalcogen during the reaction between transition metal M and chalcogen X. is known to strongly depend on the vapor pressure of When synthesizing a transition metal chalcogen compound from transition metal M and chalcogen X, the composition of the resulting compound changes depending on the reaction temperature and pressure. is likely to be generated.

By the way, the conventional method for synthesizing this type of compound, for example, a transition metal chalcogen compound with a layered structure represented by MX2, which is attracting attention for its use as a battery positive electrode active material, is to synthesize transition metal and chalcogen raw materials. A method of vacuum sealing in a quartz tube etc. and heating synthesis (M + 2
M
2H,X-MX;) Nato is common. but,
In these methods of synthesis at pressures near normal pressure or higher, MX3 is produced when the synthesis temperature is low, and MX3 is produced when the temperature is high.
Chalcogen vapor pressure and temperature must be strictly controlled in order to easily generate a non-stoichiometric compound represented by 1 opX (O < α × 1) and to synthesize a single-phase compound MX with an electric ratio composition. There are unavoidable difficulties.

Furthermore, the above-mentioned method of heat synthesis in vacuum sealing may require a very long reaction time of 1 day to 1 week, and the above-mentioned method of synthesis from chloride and hydrogen sulfide There are also problems such as the need for a step to separate HCI and HCI as they are generated at the same time.

On the other hand, in the method of synthesizing transition metal chalcogen compounds under high pressure, it is possible to seal the reaction system and high pressure acts inside the reaction system from the outside, so changes in composition due to chalcogen vapor pressure are taken into account. This is not necessary, and the reaction temperature range can be selected quite freely by matching the composition of the starting materials to the composition of the target compound. Further, since the raw materials are brought into sufficient contact with each other due to the external pressure, the reaction is completed in a short time of several minutes to several hours, followed by grain growth of crystals. Therefore,
In the method of synthesizing under high pressure, the composition and particle size of the transition metal chalcogen compound can be more easily controlled by appropriately combining the pressure, reaction temperature, and reaction time.

However, in the method of synthesis by reacting transition metal raw materials and chalcogen raw materials under high pressure, a large amount of heat is generated during the reaction, and once the reaction starts, the raw materials are heated by the heat generated by the reaction, further increasing the reaction rate. There is an inconvenient problem in that the temperature rises abnormally during this process, making it difficult to properly set the reaction humidity in the region where the desired compound is produced.

[Problems to be Solved by the Invention] The present invention has been made based on the above technical background, and overcomes and eliminates the problems of the method for synthesizing transition metal chalcodogen compounds under high pressure. However, it is an object of the present invention to provide a synthetic method that allows transition metal chalcogen compounds having arbitrary compositions to be produced easily and reliably.

[Means for Solving the Problems] In order to achieve the above object, the present invention accommodates a transition metal raw material and a chalcogen raw material in a reaction vessel, and
The present invention provides a method characterized in that a transition metal chalcogen compound is synthesized while controlling the reaction temperature within a predetermined temperature range.

The present invention will be explained in detail below. First, in order to synthesize a transition metal chalcogen compound, any of the following combinations of transition metal raw materials and chalcogen raw materials used in the present invention are possible. Firstly, a transition metal chalcogen compound can be synthesized by using a simple transition metal M and a simple chalcogen X as raw materials and reacting a mixture of these powders. Second, ready-made transition metal chalcogen compounds can be utilized as one or both of the raw materials used. That is, for example, when the purpose is to synthesize transition metal dichalcogen MX, which is difficult to synthesize with electric ratio from a mixture of transition metal M alone and chalcogen X alone, transition metal M is used as the transition metal raw material. On the other hand, transition metal chalcogen compound MX3 is used as a raw material for chalcogen.
The combination using (2M Xs + M 3 M
2) L J: This can be achieved by a reverse combination (MX+X-→MXY) of using a transition metal chalcogen compound MX as a transition metal raw material and using chalcogen X as a chalcogen raw material. In addition, a combination in which a transition metal chalcogen compound MX with a low chalcogen content is used as a transition metal raw material and a transition metal chalcogen compound MX3 with a high chalcogen content is used as a transition metal raw material (MX + MX, →2
M X2) can also be used. These utilize the fact that transition metal chalcokene compounds can take various Ml configurations, and use a transition metal raw material that supplies the transition metal as a transition metal raw material that has a lower chalcogen content than the target compound to be synthesized. Chalcogen materials with a high content of chalcogen are used as chalcogen raw materials that supply chalcogen. When this transition metal chalcogen compound is used as a raw material for synthesis, the amount of heat generated by the reaction to form the compound is smaller than when synthesizing a simple transition metal and a simple chalcogen, making it easier to adjust the reaction temperature. It has the advantage of being relatively easy to do.

In any combination, the transition metal raw material and chalcogen raw material are mixed at a predetermined molar ratio determined according to the composition of the target compound, placed in a reaction vessel, and subjected to reaction under high pressure. Ru.

In the present invention, 1. The above-mentioned mixed raw materials contained in a reaction vessel are set in a high-pressure device equipped with heating means, and a synthesis reaction is carried out under high pressure. The main reason for using high pressure here is to confine chalcogen vapor in the reaction system during synthesis, and for this purpose a pressure of 100 atmospheres or more is required. In the present invention, under this high pressure, the mixed raw materials in the reaction vessel are heated and heated by an appropriate heating means. Then, the mixed raw materials will start reacting before reaching a predetermined humidity range (temperature range in which the target compound is produced). However, since the heat of formation of transition metal chalcogen compounds is generally large and the reaction proceeds rapidly, if the heating is continued at the original temperature increase rate after the reaction has started, the temperature of the reaction system will increase instantaneously, and the desired reaction will not be achieved. It becomes impossible to carry out the reaction in the desired formation temperature range. In other words, the production reaction proceeds at a temperature higher than the target temperature, resulting in the inconvenience that a compound having the desired composition cannot be obtained. Therefore, in the present invention,
At the same time as the reaction starts, the amount of heat supplied from the outside to the reaction vessel is adjusted to decrease, or if necessary, the supply of heat is stopped, and the temperature of the system, including the amount of heat released after the reaction starts, reaches the desired production level. The temperature is controlled to be maintained within the range. In order to carry out this temperature control, the temperature of the system may be constantly measured to sequentially detect the start of the reaction and temperature changes, and the amount of heat to be supplied may be adjusted in response to the detection results. In order to quickly and accurately detect the temperature of the system, it is most effective to embed a temperature sensor such as a thermocouple directly into the raw material, but this would complicate the structure of the reaction vessel and There are disadvantageous problems such as the possibility of chalcogen gas leaking from the thermocouple introduction path, and furthermore, the thermocouple being corroded by chalcogen. As a measure to solve this problem, it is possible to use a reaction vessel made of metal with good thermal conductivity and to arrange a thermocouple near the vessel. In other words, by doing this, it is possible to detect temperature changes in the system in a timely manner, albeit indirectly, without suffering from the above-mentioned problems, and at the same time, it is possible to quickly respond to temperature control by adjusting the amount of heat supplied in the container. It also has the advantage of increasing sex.

Once the reaction conditions are determined by the method described above, by programming a temperature increase pattern in advance for the same sample, it becomes possible to automatically perform optimal temperature control thereafter.

In addition, in cases where the amount of heat generated by the production reaction of transition metal chalcogen compounds is extremely large and the reaction is still accelerated even if the supply of external thermal energy is stopped immediately after the start of the reaction, the mixed raw material may be It is preferable to house them in a dispersed manner within the reaction vessel. In this way, heat radiation from the raw material to the surrounding pressure medium is promoted, and heat accumulation inside the raw material can be effectively prevented.

An example of a specific adjustment pattern for controlling the reaction temperature by reducing the amount of heat supplied to the reaction container from the outside is shown in FIG. 1. FIG. 1 shows an outline of a heating schedule during a high-pressure reaction, with the vertical axis representing supplied heat energy (electric power) and the horizontal axis representing time. That is, according to this schedule, the system is first heated up, and when it reaches point a, where the transition metal M and chalcogen X begin to react and rapidly generate heat, the heating is stopped once (usually for several minutes), and then When the temperature of the system begins to drop, it is heated again to raise the temperature to point b, and then heated and maintained at a constant temperature from point b to point 0, and then allowed to cool. Here, the temperature at point a is 300 to 500°C regardless of the type and composition of the raw materials.
On the other hand, the temperature at point b (synthesis temperature) depends on the target composition, that is, M
℃, 450-1000℃ for MX3, 500℃ for MX2
℃ or above, each is set separately. Further, the temperature between b and c varies depending on the synthesis temperature and the intended particle size of the composite, and is set to a long culm time, for example, when it is desired to obtain a large particle size at a low synthesis temperature. However, even in that case, the maximum
It is sufficient to take a holding time of about 1 hour.

[Function] By the various means described above, the present invention synthesizes a transition metal raw material and a chalcogen raw material under high pressure while controlling the reaction temperature within a predetermined temperature range. As long as the composition of the raw materials is matched to the composition of the target compound, only transition metal chalcogen compounds having a specific composition determined by the reaction temperature will be synthesized. In this method, the reaction system is sealed under high pressure. Therefore, in the conventional method, chalcogen is insufficient during synthesis, as in the transition metal dichalcogen MX2, resulting in an indefinite amount expressed as M++1tX (α〉0). MX, MX
MX due to contamination with compounds containing a large amount of chalcogen such as 4,
This solves the problem that it is difficult to obtain a single phase. Also,
It has the characteristic that single-phase products can be easily synthesized even for products with a large chalcogen content.

[Example] Examples of the present invention will be described below.

<Example 1> Transition metals (group ■ T1, Z, group V Nb, Ta) c
7) Each powder (200 mesh) is mixed with sulfur and 1=
The raw material is a mixture with a molar ratio of 2:2 and 2:2, which is packed into a gold reaction vessel (sample capsule) and surrounded by boron nitride (
BN) powder, and a platinum-platinum rhodium thermocouple was set. Then, a carbon heater is attached to the outside and placed in a high pressure container, and a regular hexahedral high pressure generator is used to generate 3
It was pressurized to 10,000 atmospheres. In addition, in Fig. 2 (a) and (b),
The outline of the sample chamber of the high-pressure reaction device used in Examples is shown. In the figure, 1 is a reaction vessel, 2 is a carbon heater, and 3 is a BN
4 is mica, 5 is a thermocouple, and 6.7 is pyrophyllite and a copper plate that surround these and constitute a high-pressure cell. Then, this high pressure cell 8 is set in a high pressure generator 10 that is pressurized from six directions by a WC anvil 9 (at this time, a pair of anvils 9.9 are attached to the copper plate 7.
7 is held between them to energize the carbon heater 2, and the thermocouple 5 is held between another pair of anvils 9 and 9 to measure the thermoelectromotive force).

Then, electricity was applied to the carbon heater, and the temperature was raised while measuring the temperature with a thermocouple. The heating rate was initially 5 per minute.
The heating rate was 0°C from 450°C for the T7-3, Z, -S system, and 500°C per minute for the Nb-3, T (1-S system). As soon as the reaction started and the temperature started to rise rapidly, the electricity was turned off.Then, as soon as the temperature started to fall, the electricity was turned on again, and the temperature was raised at a heating rate of 50 to 100°C per minute until the desired synthesis temperature was reached. The heated 0 synthesis temperature is 500℃, 600℃, 800℃
The holding time was varied from 15 minutes to 6 hours. Thereafter, the temperature and pressure were lowered, and the sample was taken out from the container. When these samples were identified by powder X-ray diffraction and optical microscopy, it was found that under all conditions, the electrical composition was MX (T, S, zrS2, NbS2, T(13
It was confirmed that 2) was synthesized in a single phase.

<Example 2> A mixture of each powder (200 mesh) of transition metals (group ■ T+, Zl-1V group Nb, Th) and sulfur at a molar ratio of 1=3 was used as the raw material, and this was used as the raw material for Example 1. It was set in the high pressure generator using the same procedure as above. and,
After pressurizing to 20,000 atm, the temperature of each system was raised at a rate of 50°C per minute up to 400°C, and thereafter the temperature was raised at a rate of 10°C per minute to the desired synthesis temperature. Synthesis temperature is 400℃, 5
The temperature was 00°C and 700°C, and the holding time was varied from 15 minutes to 2 hours. After lowering the temperature and pressure, remove the sample from the container.

Identification using powder X-ray diffraction and optical microscopy revealed that M
, , Nl>33, TaS,) was found to be synthesized in a single phase.

<Example 3> A mixture of niobium metal powder and selenium at a molar ratio of 1:4 was used as a raw material, and this was set in a high pressure generator using the same procedure as in Example 1. After pressurizing to 30,000 atm, the temperature was raised at a rate of 50°C per minute until 300'O, and thereafter the temperature was raised at a rate of 5°C per minute to the desired synthesis temperature. ℃, 450℃, holding time 1 to 4
It was time. After lowering the temperature and pressure, remove the sample from the container.
Identification using powder X-ray diffraction and optical microscopy revealed that the product was synthesized as a single phase of NbSe4 under all synthesis conditions.

<Example 4> Using the same raw materials and equipment as in Example 1, in this case, without setting a thermocouple, the relationship between the amount of 0 current applied and the reaction system temperature was synthesized by monitoring the amount of current applied to the heater. , the correlation is investigated using Example 1. However, T+
-5, Zr-3, N'D-S, T, -3 reaction systems were pressurized to 30,000 atmospheres, and the current was increased by 20 watts per minute to 190 watts, and then the current was immediately turned off. Stop,
One minute later, the amount of current was increased again by 40 watts per minute to 410 watts. After maintaining this state for 4 hours, the current supply was stopped for one time, the temperature and pressure were lowered, and then the sample was taken out from the container. When these were identified by powder X-ray diffraction, it was found that they all had electrical compositions of MX2 (T+ 52, ZrS,
, NbS2, TaS,) were single-phase.

<Example 5> MX of metallic titanium powder or metallic niobium powder to transition metal trichalcogen compound T, S, NbS3: M=2
: The mixture was added and pulverized to a molar ratio of 1 and set in a high pressure generator using the same procedure as in Example 1.
It was pressurized to 10,000 atmospheres. The temperature was raised at a constant rate of 100°C per minute to a reaction temperature of 100°C. And 4
After holding for a period of time, lower the temperature and pressure, take out the sample, and powder
Identification by line diffraction revealed that the electrical ratio of TiS2
, was a single phase of NbS2.

<Example 6> Sulfur was added to the transition metal dichalcogen compounds TiS2 and NbS at a molar ratio of MX:x=l:l, and the mixture was pressurized to 30,000 atmospheres in the same manner as in Example 1.

The temperature was raised continuously at a constant rate of 50°C per minute to a reaction temperature of 700°C. After holding the sample for 4 hours, the electricity was turned off, the sample was taken out, and the samples were identified by powder X-ray diffraction. As a result, single phases of T+ 33 and Nb5j were synthesized, respectively.

<Example 7> IG Se and NbSe were pulverized and mixed at a molar ratio of 1:1, and the mixture was pressurized to 20,000 atmospheres in the same manner as in Example 1. The reaction temperature was 700°C at a constant rate of 100°C per minute.
The temperature was raised continuously to ℃. After holding the sample for 4 hours, the temperature and pressure were lowered, and a sample was taken out and identified by powder X-ray diffraction. As a result, a single Nb5I2 phase was formed.

<Example 8> The same amount of each mixed raw material used in Example 1 was equally divided into four parts, each of which was placed in a sample capsule, separated from each other by boron nitride powder, and housed in a high-pressure cell. Thermocouples were then set in the centers of the four sample capsules, and the capsules were pressurized at 30,000 atmospheres. However, unlike in Example 1, the temperature was raised continuously to 1000°C at a heating rate of 50°C per minute without interrupting heating midway. After that, it was held for 4 hours, the temperature and pressure were lowered, and then the sample was taken out.
When identified by powder X-ray diffraction, they all had electrical specific compositions of M X2 (T+ S, zrs2, NbS2
, Ta S2) Single-phase force is generated and TELz'.

[Effects of the Invention] As described above, in the present invention, a transition metal raw material and a chalcogen raw material are synthesized under high pressure while particularly controlling the reaction temperature within a predetermined temperature range. It is now possible to easily and reliably synthesize transition metal lucogen compounds having various composition ratios, which have been difficult to control.

[Brief explanation of the drawing]

FIG. 1 is a diagram of a heating schedule showing an example of reaction temperature control according to the present invention. FIG. 2 shows an overview of the high-pressure reactor used in the examples of the present invention, FIG. 2(a) is a longitudinal cross-sectional view of the high-pressure cell, and FIG. 2(b) is a sample chamber of the high-pressure generator. FIG. Rito Satoshi Patent Attorney Hirobi Akazawa

Claims (8)

[Claims] (1) Synthesis of a transition metal chalcogen compound, characterized in that a transition metal raw material and a chalcogen raw material are housed in a reaction vessel, and the transition metal chalcogen compound is synthesized while controlling the reaction temperature within a predetermined temperature range under high pressure. Method. (2) The method for synthesizing a transition metal chalcogen compound according to claim 1, wherein the transition metal raw material consists of a simple transition metal, and the chalcogen raw material consists of a simple chalcogen. (3) The method for synthesizing a transition metal chalcogen compound according to claim 1, wherein the transition metal raw material consists of a simple transition metal, and the chalcogen raw material consists of a transition metal chalcogen compound. (4) The method for synthesizing a transition metal chalcogen compound according to claim 1, wherein the transition metal raw material is composed of a transition metal chalcogen compound, and the chalcogen raw material is composed of a simple substance of chalcogen. (5) The transition metal chalcogen according to claim 1, wherein the transition metal raw material is composed of a transition metal chalcogen compound with a low chalcogen content, and the chalcogen raw material is composed of a transition metal chalcogen compound with a high chalcogen content. Methods for synthesizing compounds. (6) In order to control the reaction temperature within a predetermined temperature range, the amount of heat supplied from the outside to the reaction vessel is adjusted to decrease after the reaction between the transition metal raw material and the chalcogen raw material starts. A method for synthesizing a transition metal chalcogen compound according to scope 1, 2, 3, 4, or 5. (7) The transition metal chalcogen compound according to claim 1, 2, 3, 4, 5, or 6, wherein a metal container is used as the reaction container. synthesis method. (8) In order to control the reaction temperature within a predetermined temperature range, a mixed raw material of a transition metal raw material and a chalcogen raw material is dispersed and stored in a reaction vessel.
Paragraph 2, Paragraph 3, Paragraph 4, Paragraph 5, Paragraph 6 or Paragraph 7
A method for synthesizing a transition metal chalcogen compound as described in .