JP4593124B2 - Method for producing perovskite-type nanoparticles - Google Patents

Description

The present invention relates to a method for producing perovskite-type nanoparticles , and in particular, perovskite-type nanoparticles usable for various devices such as optical waveguides, optical switches, modulation elements, optical deflection elements, capacitors, ferroelectric memories, and piezoelectric elements . It relates to a manufacturing method .

A double oxide having a perovskite structure represented by the chemical formula of ABO ₃ typified by lithium niobate and lithium tantalate has electrical characteristics such as ferroelectricity, piezoelectricity, pyroelectricity, electrooptic effects, acoustic It is known as an excellent functional material with optical characteristics such as optical effects and nonlinear optical effects, and includes non-volatile memories using ferroelectric thin films, surface acoustic wave (SAW) elements, infrared pyroelectrics. Element, acousto-optic element, electro-optic element, optical waveguide, optical switch, modulation element, optical deflection element, capacitor, surface acoustic wave (SAW) substrate, piezoelectric ultrasonic transducer, low frequency bulk wave composite piezoelectric vibrator, reflection Various products, such as prevention products, have been proposed and put into practical use in the fields of electronics and optoelectronics.
A double oxide having such a perovskite structure needs to be thinned when applied to optical and electronic devices.

As a method for thinning such a complex oxide, a high-frequency magnetron sputtering apparatus, a plasma sputtering apparatus, an ion beam sputtering apparatus, a reactive sputtering apparatus, an organic metal CVD (MOCVD) apparatus, a plasma CVD apparatus, a laser CVD apparatus, etc. Various film forming apparatuses are used depending on the composition and thickness.
Further, there is a sol-gel method as a method capable of forming a film at a relatively low temperature of about 300 ° C. to 600 ° C. For example, in a ferroelectric memory (FeRAM), a ferroelectric thin film is formed by using this sol-gel method. Have been proposed and put to practical use (see, for example, Patent Document 1).
In this ferroelectric memory, a ferroelectric thin film is formed on an amorphous silicon oxide film (a-SiO ₂ film) by a sol-gel method. When the ferroelectric thin film is formed, the solution is dried and organic substances are removed. Therefore, after pretreatment is performed at a temperature of about 50 ° C. to 150 ° C., heat treatment is performed at a temperature of 550 ° C. or higher in order to further crystallize the ferroelectric thin film.

On the other hand, with the advancement of nanotechnology in recent years, functionalization techniques such as a thin film in which nanoparticles are applied and dried and a composite film in which nanoparticles are dispersed in an organic polymer are also being advanced. Various methods have been proposed as a method for producing the nanoparticles, and examples of the method for forming the double oxide into particles include a solid phase method, a precipitation method, and a sol-gel method.
In the solid phase method, raw powders such as oxides and carbonates containing each component element are mixed using a ball mill, and then filtered, dried, and pulverized to obtain a powdery mixture, which is fired at a high temperature. This is a method for obtaining a double oxide powder.
In the precipitation method, a precipitant is added to a metal salt aqueous solution that is a raw material of a double oxide to form a precipitate such as a hydroxide or a hydrate, and this precipitate is filtered, washed, dried, and calcined. Thus, a double oxide powder is obtained.
Further, the sol-gel method is a method of hydrolyzing a metal alkoxide as a raw material of a double oxide to form an amorphous precursor, and firing the amorphous precursor to obtain an oxide crystal powder.
In these methods, double oxide particles having a size of about 1 μm can be obtained.
JP 2002-324895 A

By the way, in the conventional method for forming a ferroelectric thin film using the sol-gel method, the difference in the coefficient of thermal expansion between the silicon oxide film and the ferroelectric thin film is so large that it is formed on the conventional lower electrode. There is a problem that crystallization is insufficient as compared with the ferroelectric thin film.
Further, the ferroelectric thin film and the silicon oxide film may react during crystallization by heat treatment. In this case, there is a problem in that a crack occurs in the ferroelectric thin film, and the capacitance as a capacitor cannot be maintained.

On the other hand, the method for forming a double oxide into particles also has the following problems.
In the solid phase method, since the heat treatment is performed at a high temperature, the particles tend to be coarse. The coarse particles can be made into fine particles by pulverization, but impurities cannot be avoided during the pulverization process, and fine particles suitable for a thin film cannot be obtained.
In addition, in the precipitation method, it is necessary to calcinate the precipitate at a high temperature of 500 ° C. or higher, but the particles are coarsened by this calcination, and the particles are very strongly agglomerated and cannot be dispersed. It is not possible to obtain fine particles that are very suitable for thin films.
Furthermore, the sol-gel method requires high-temperature firing for crystallization, as in the precipitation method, and the obtained particles are coarse and strongly aggregated, and are not suitable for thin films.

The present invention has been made to solve the above-described problems, and can be crystallized at a lower temperature, has high crystallinity even with a small particle size of 50 nm or less, and further has dispersibility. An object of the present invention is to provide a method for producing perovskite-type nanoparticles excellent in.

As a result of intensive studies, the present inventor has found that A _x B _y O _z (where A is one or two selected from the group of group IA elements, group IB elements, group IIA elements, group IIB elements) In producing a nanoparticle having a perovskite structure composed of an element, B is one or more elements selected from transition metal elements), the compound containing A and the compound containing B are mixed in the presence of a supercritical fluid. By reacting and then removing the supercritical fluid without condensing it, in the presence of the supercritical fluid, the crystallization temperature of the compound having a perovskite structure is conventionally 500 ° C. or higher. The inventors have found that perovskite-type nanoparticles having high crystallinity and excellent dispersibility can be obtained even if the particles can be crystallized at 300 ° C. or lower, and even if the particles are 50 nm or less, the present invention is completed. This has led to the.

That is, the manufacturing method of the perovskite type nanoparticles of the present invention is A _x B _y O _z (where A is one or two selected from the group of group IA elements, group IB elements, group IIA elements, group IIB elements) A method for producing nanoparticles having a perovskite structure composed of a seed element, wherein B is one or more elements selected from transition metal elements, wherein the compound containing A and the compound containing B are supercritical fluids. And then removing the supercritical fluid without condensing.

The supercritical fluid is preferably alcohol.
The A is preferably one or two selected from lithium, sodium, potassium, calcium, strontium, and barium, and the B is preferably niobium, tantalum, or niobium and tantalum .
The compound containing A and the compound containing B are preferably hydroxides.

According to the method for producing perovskite-type nanoparticles of the present invention, a compound containing one or two elements A selected from the group of Group IA elements, Group IB elements, Group IIA elements, and Group IIB elements, and a transition metal A compound containing at least one element B selected from elements is reacted in the presence of a supercritical fluid, and then the supercritical fluid is removed without condensation. By performing supercritical drying at a low temperature, perovskite-type nanoparticles having high crystallinity and dispersibility and having a particle size of 50 nm or less can be produced without heat treatment.
In addition, since an apparatus that generates a supercritical state is relatively inexpensive as compared with a CVD apparatus or the like, an expensive apparatus is unnecessary, and the reaction temperature does not require a high temperature of 500 ° C. or higher. Manufacturing cost can be reduced.

According to the film of the present invention, since the perovskite nanoparticle of the present invention is contained, the highly crystalline perovskite nanoparticle can be uniformly dispersed in the film, and thus the characteristics of the film are greatly improved. Therefore, it is possible to provide a highly functional thin film element.
Further, by selecting the composition of the perovskite type nanoparticles, it is possible to provide a highly functional thin film element having desired characteristics.

The best mode of the method for producing perovskite nanoparticles of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention and does not limit the present invention unless otherwise specified.

The perovskite type nanoparticles obtained by the method for producing perovskite type nanoparticles of the present invention are selected from the group consisting of A _x B _y O _z (where A is a group of IA group element, IB group element, IIA group element, IIB group element) 1 or 2 elements, and B is a nanoparticle having a perovskite structure composed of a transition metal element and having a primary particle diameter of 10 nm or more and 50 nm or less.
The nanoparticles of the present invention have such a small nano-size particle diameter, but each particle has a perovskite structure, and its crystallinity is very high.

Here, A is one or two elements selected from the group of Group IA elements, Group IB elements, Group IIA elements, and Group IIB elements, and Li, Na, K, Rb, Cs, Fr, Be , Mg, Ca, Sr, Ba, Ra, Cu, Ag, Au, Bk, Zn, Cd, Hg, Cf, or a combination of two.
B is one or more elements selected from transition metal elements.
In practice, A is preferably one or two selected from the group consisting of Li, Na, K, Ca, Sr, and Ba. B is preferably at least one selected from the group consisting of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and more preferably Nb and / or Ta.

Examples of the perovskite structure composed of A _x B _y O _z include lithium niobate, potassium niobate, sodium niobate, calcium niobate, lithium tantalate, calcium tantalate, calcium titanate, barium titanate, titanate Strontium etc. are mentioned.

The method for producing perovskite-type nanoparticles of the present invention comprises A _x B _y O _z (where A is one or two selected from the group of group IA elements, group IB elements, group IIA elements, group IIB elements) Element, B is a method for producing nanoparticles having a perovskite structure consisting of one or more elements selected from transition metal elements, wherein the compound containing A and the compound containing B are combined in the presence of a supercritical fluid. And then removing the supercritical fluid without condensing it.

Here, A is one or two elements selected from the group of Group IA elements, Group IB elements, Group IIA elements, and Group IIB elements, and Li, Na, K, Rb, Cs, Fr, Be , Mg, Ca, Sr, Ba, Ra, Cu, Ag, Au, Bk, Zn, Cd, Hg, Cf, or a combination of two.
B is one or more elements selected from transition metal elements.
In practice, A is preferably one or two selected from the group consisting of Li, Na, K, Ca, Sr, and Ba. B is preferably at least one selected from the group consisting of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and more preferably Nb and / or Ta.

Examples of the perovskite structure composed of A _x B _y O _z include lithium niobate, potassium niobate, sodium niobate, calcium niobate, lithium tantalate, calcium tantalate, calcium titanate, barium titanate, titanate Examples thereof include strontium, and can be applied to all compounds having a perovskite structure (perovskite type compounds).

Although it does not restrict | limit especially as a compound containing A, For example, the hydroxide, nitrate, acetate, alkoxide, etc. which contain A element can be used, The hydroxide containing A element is especially preferable.
Examples of the hydroxide containing A element include crystalline hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide.

Although the compound containing B is not particularly limited, for example, a hydroxide, nitrate, acetate, chloride, alkoxide or the like containing B element can be used, and a hydroxide containing B element is particularly preferable.
Examples of the hydroxide containing B element include crystalline hydroxides such as niobium hydroxide and tantalum hydroxide.

In addition, as the hydroxide containing the A element and the hydroxide containing the B element, an amorphous hydroxide can be used.
As an amorphous hydroxide containing A element and an amorphous hydroxide containing B element, metal salt aqueous solution such as chloride, nitrate, sulfate, acetate containing A element or B element, It can be obtained by the action of an alkali (basic substance).

Examples of the alkali that can be used include ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, strontium hydroxide, and amine.
At this time, when an A element hydroxide, which is a composition component of the target perovskite nanoparticles, is used as an alkali, an amorphous hydroxide containing the A element and the B element can be obtained without adding an alkali separately. It is preferable because it can be obtained.
For example, when it is intended to obtain LiNbO ₃ , it is preferable to use lithium hydroxide when preparing an amorphous hydroxide precipitate. Ammonia and amine can be used in any composition.

Moreover, as an amorphous hydroxide containing an A element, a hydrolyzate of an alkoxide containing an A element, and as an amorphous hydroxide containing an B element, a hydrolyzate of an alkoxide containing an B element. Can be used respectively.
In this case, it is preferable to use an amorphous hydroxide obtained from a hydrolyzate of alkoxide for both the amorphous hydroxide containing the A element and the amorphous hydroxide containing the B element. Furthermore, it is more preferable to use a mixed amorphous hydroxide prepared by previously mixing an alkoxide containing an A element and an alkoxide containing a B element thoroughly and cohydrolyzing.

The alkoxide is not particularly limited. For example, when the target crystal is lithium niobate, a lithium alkoxide such as lithium methoxide or lithium ethoxide can be used as the lithium source, and the niobium source can be pentaethoxyniobium, Pentamethoxy niobium or the like can be used.
These can be used after being separately hydrolyzed and then mixed, but more preferably, they are refluxed in anhydrous alcohol to form a composite alkoxide, and the composite alkoxide is preferably co-hydrolyzed for use.

  The hydroxide containing the A element and the hydroxide containing the B element used as the reaction raw material may be crystalline or amorphous, but when the purpose is to produce a perovskite nanoparticle having a smaller particle size, The hydroxide containing B element is preferably an amorphous hydroxide having a small particle size.

In the production method of the present invention, a compound containing A as a raw material and a compound containing B are reacted in the presence of a supercritical fluid.
First, the raw material is dispersed (or dissolved) in a dispersion medium (or solvent), filled in a pressure vessel, and heated and pressurized at a temperature and pressure exceeding the critical point of the solvent.

The dispersion medium or solvent is not particularly limited as long as it does not react with the raw material, and for example, alcohol and / or water can be used. The critical temperature and critical pressure are preferably small, and the critical temperature is preferably 500 ° C. or lower. Alcohol is particularly preferred as a dispersion medium or solvent because it satisfies these conditions.
The alcohol that can be used as the dispersion medium or solvent is not particularly limited, but is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol. (Isobutyl alcohol), 2-methyl-2-propanol (t-butyl alcohol), 2-propenol (allyl alcohol) and the like are preferably used. Two or more kinds of alcohols may be mixed and used.

  For example, when methanol is used, the critical temperature is 240 ° C. and the critical pressure is 8.09 MPa. When ethanol is used, the critical temperature is 241 ° C. and the critical pressure is 6.14 MPa, and 1-propanol is used. In this case, the critical temperature is 264 ° C. and the critical pressure is 5.17 MPa. When 1-butanol is used, the critical temperature is 290 ° C. and the critical pressure is 4.42 MPa.

A material in which the raw material is dispersed (or dissolved) in the dispersion medium (or solvent) is operated so that the temperature and pressure exceed the critical temperature and critical pressure of the dispersion medium (or solvent), and a supercritical state is generated. Let
For example, when ethanol is used as the dispersion medium, the critical temperature of ethanol is 241 ° C., and the critical pressure is 6.14 MPa. Therefore, the operation is performed so that the temperature and pressure are higher. As preferable values of these temperatures and pressures, the temperature is 260 ° C. or more and the pressure is 8 MPa or more. Moreover, when using alcohol, about 5-10 wt% of water may be included.

In order to uniformly disperse the hydroxide raw material in the container in the dispersion medium (or in the solvent) during the temperature rise and pressurization, the hydroxide raw material and the dispersion medium (or solvent) are dispersed using a stirring blade or the like. It is preferable to stir.
After producing the supercritical state, the dispersion medium (or solvent) is discharged outward from the pressure vessel and removed. Here, stirring the hydroxide raw material and the dispersion medium (or solvent) in the container at the time of release is not preferable because the perovskite type nanoparticles synthesized together with the dispersion medium (or solvent) may also be released. Further, after the supercritical state is generated, the reaction time is not particularly limited, and the dispersion medium (or solvent) may be immediately released and removed. In addition, the holding time can be adjusted for the purpose of improving crystallinity.

When the dispersion medium (or solvent) is released and removed, it is necessary to carry out the conditions so that the dispersion medium (or solvent) in the pressurized container does not condense. In this case, as the dispersion medium (or solvent) is released, the pressure and temperature in the pressurized container decrease. Therefore, when the pressure in the pressurized container falls below the critical pressure, the dispersion medium (or It is necessary to heat so as to keep the temperature above the boiling point of the solvent.
After confirming that the pressure in the pressurized container has dropped to atmospheric pressure and all the dispersion medium (or solvent) has been released and removed, the pressure is returned to room temperature.
What is important here is that, as shown in FIG. 1, the supercritical state (point A in the figure) is passed through the gas phase without passing through the liquid phase (arrow in the figure) and returned to room temperature and normal pressure (point B in the figure). )That's what it means.

According to this production method, A _x B _y O _z having a primary particle size of 10 nm or more and 50 nm or less, such as lithium niobate or lithium tantalate having a particle size of 50 nm or less (where A is a group IA element, Producing perovskite-type nanoparticles composed of one or two elements selected from the group of group IB elements, group IIA elements and group IIB elements, and B is one or more elements selected from transition metal elements) Can do.

  In the conventional method, in order to obtain perovskite-type nanoparticles such as lithium niobate and lithium tantalate, heating at 500 ° C. or higher is required. However, in the production method of the present invention, a compound containing A as a raw material and B Is reacted in the presence of a supercritical fluid, the reaction is accelerated under high temperature and high pressure, and perovskite nanoparticles can be obtained at a low temperature of 500 ° C. or lower.

Conventionally, particles synthesized in the liquid phase have a gas-liquid interface in the particle gap during the drying process when the particles are taken out, and have been agglomerated tightly due to the adhesion due to capillary action. Since the gas phase and the liquid phase are indistinguishable, and there is no gas-liquid interface, the dispersion medium is put into a supercritical state, and the dispersion medium is removed without passing through the liquid phase, thereby aggregating the particles. Therefore, nanoparticles of 50 nm or less can be obtained.
As described above, perovskite nanoparticles having a primary particle size of 10 nm or more and 50 nm or less, high crystallinity, and almost no amorphous portion can be obtained.

A film having a perovskite structure can be produced using the above-described perovskite-type nanoparticles.
For example, a thin film having a perovskite structure can be produced by applying a dispersion obtained by uniformly dispersing the perovskite nanoparticles in a dispersion medium onto a substrate.
In order to obtain a thin film with few defects, a dispersing agent is added to disperse perovskite-type nanoparticles to prevent aggregation of the nanoparticles, and the nanoparticles are dispersed using a disperser such as a dissolver or a dispersion mill. Disperse uniformly in the medium.

  As the dispersion medium, for example, ketones such as methyl ethyl ketone and diethyl ketone, alcohols such as methanol, ethanol, 2-propanol and 1-butanol, ethyl acetate and the like can be appropriately selected and used. You may use, and may mix and use 2 or more types.

You may add a binder and an additive with respect to this dispersion liquid as needed. As the binder, for example, an epoxy resin, an acrylic resin, a fluororesin, or the like is preferably used.
When applying the dispersion, various coating methods can be used, such as spin coating, bar coating, dip coating, spray coating, gravure coating, slit coating, roll coating, etc. It can be selected appropriately.

In this way, a thin film having a perovskite structure having high crystallinity and excellent dispersibility can be obtained by applying the above dispersion onto a substrate.
In this thin film, since the dispersed nanoparticles have high crystallinity, heat treatment at a high temperature is not required after film formation.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-3 and a comparative example, this invention is not limited by these Examples.

Example 1
Lithium methoxide (LiOCH ₃ ) and pentaethoxyniobium (Nb (OC ₂ H ₅ ) ₅ ) are mixed in anhydrous ethanol (C ₂ H ₅ OH) in a nitrogen atmosphere to obtain a mixed alkoxide solution, and this mixed alkoxide solution Was refluxed at about 75 ° C. for 3 hours to prepare a lithium-niobium composite alkoxide.
Next, 7.5 mol times ammonia water (NH ₄ OH) was added to the composite alkoxide for hydrolysis to obtain an ethanol solution containing a lithium / niobium hydroxide precipitate. Thereafter, the ethanol solution containing the precipitate was filled in a pressurized container, and the inside of the pressurized container was heated and pressurized to make the inside of the pressurized container a supercritical state of 300 ° C. and about 14 MPa. Thereafter, only ethanol was discharged out of the pressurized container while maintaining the temperature in the pressurized container at 300 ° C. to obtain a white powder.

The phase of this white powder was identified by a powder X-ray diffraction method. Using CuKα rays as characteristic X-rays, this white powder was identified by the Hanawait method, and the phase of this white powder was examined. The result is shown in FIG.
As a result of this identification, it was found that a lithium niobate (LiNbO ₃ ) single phase was obtained.

Moreover, the average particle diameter of this white powder was measured with a scanning electron microscope (SEM). This SEM image is shown in FIG.
As a result of the measurement, it was found that the particle size of the white powder was in the range of 20 to 30 nm.
From the above, it was found that the white powder was a single-phase nanoparticle of lithium niobate (LiNbO ₃ ) having a particle size of 20 to ₃₀ nm.

(Example 2)
Niobium chloride was dissolved in pure water, and an aqueous solution containing niobium hydroxide (Nb (OH) ₅ ) precipitate was obtained by adding and stirring an equimolar amount or more of lithium hydroxide aqueous solution to the niobium chloride aqueous solution. .
Subsequently, this aqueous solution was centrifuged, and water, lithium hydroxide (LiOH), and excess chlorine (Cl) as solvents were removed from the precipitate. Next, the precipitate was dispersed in ethanol, and then lithium hydroxide (LiOH) was added to the dispersion so that Li / Nb = 1, followed by stirring to sufficiently disperse the precipitate.

  Next, the dispersion was filled into a pressurized container, and the inside of the pressurized container was heated and pressurized to make the inside of the pressurized container a supercritical state of 300 ° C. and about 14 MPa. Thereafter, only ethanol was discharged out of the pressurized container while maintaining the temperature in the pressurized container at 300 ° C., to obtain a white powder.

The phase of this white powder was identified by the powder X-ray diffraction method as in Example 1.
FIG. 4 is a diagram showing an X-ray diffraction pattern of the white powder of Example 2. The diffraction line intensity of lithium niobate (LiNbO ₃ ) of the JCPDS card in which each peak of the diffraction line of this white powder is shown in the lower part of the figure. Consistent with the data, this white powder was found to be single phase lithium niobate (LiNbO ₃ ).
Thus, it has been found that high crystallinity can be obtained by performing supercritical drying without performing heat treatment at 500 ° C. or higher.

Moreover, the average particle diameter of this white powder was measured with a scanning electron microscope (SEM). This SEM image is shown in FIG.
As a result of the measurement, it was found that the particle size of this white powder was about 30 nm.
From the above, it was found that this white powder was a single phase nanoparticle of lithium niobate (LiNbO ₃ ) having a particle size of about 30 nm.

(Example 3)
An aqueous solution containing niobium chloride (Nb (OH) ₅ ) precipitate obtained by dissolving niobium chloride in pure water, adding and stirring to this niobium chloride aqueous solution sufficient ammonia water to neutralize niobium chloride. Got.
Next, the aqueous solution was centrifuged to remove water as a solvent from the precipitate. Thereafter, the precipitate was washed four times with pure water, and chlorine (Cl) was removed from the precipitate.

Next, the precipitate was dispersed in ethanol, and then lithium hydroxide (LiOH) was added to the dispersion so that Li / Nb = 1, followed by stirring to sufficiently disperse the precipitate.
This dispersion was reacted in the supercritical fluid region of alcohol in the same manner as in Example 1 to obtain a white powder.

The phase of this white powder was identified by the powder X-ray diffraction method as in Example 1.
FIG. 6 is a view showing an X-ray diffraction pattern of the white powder of Example 3, and the diffraction line intensity of lithium niobate (LiNbO ₃ ) of the JCPDS card in which each peak of the diffraction line of this white powder is shown in the lower part of the figure. Consistent with the data, this white powder was found to be single phase lithium niobate (LiNbO ₃ ).
Thus, it has been found that high crystallinity can be obtained by performing supercritical drying without performing heat treatment at 500 ° C. or higher.

Moreover, the average particle diameter of this white powder was measured with a scanning electron microscope (SEM). This SEM image is shown in FIG.
As a result of the measurement, it was found that the particle size of this white powder was about 30 nm.
From the above, it was found that this white powder was a single phase nanoparticle of lithium niobate (LiNbO ₃ ) having a particle size of about 30 nm.

(Comparative example)
An equimolar amount of lithium methoxide (LiOCH ₃ ) and pentaethoxyniobium (Nb (OC ₂ H ₅ ) ₅ ) are mixed in anhydrous ethanol (C ₂ H ₅ OH) in a nitrogen atmosphere to obtain a mixed alkoxide solution, The mixed alkoxide solution was refluxed at about 75 ° C. for 3 hours to prepare a lithium / niobium composite alkoxide.
Subsequently, 7.5 mol times ammonia water (NH ₄ OH) was added to the composite alkoxide for hydrolysis, and then reflux and filtration were performed, and the resulting lithium niobium hydroxide precipitate was recovered. The precipitate was dried in the atmosphere at 60 ° C. for 12 hours, and the obtained dried product was heat-treated in the atmosphere at 650 ° C. for 1 hour to obtain a white powder.

This white powder was observed with a scanning electron microscope (SEM). This SEM image is shown in FIG. According to this figure, due to the progress of sintering, a plurality of abnormally grown particles were observed and the shape was irregular.
Further, the crystallinity when the heat treatment conditions of the dried product were changed was examined.
FIG. 9 is a view showing an X-ray diffraction pattern when the heat treatment conditions of the white powder are changed. The heat treatment temperatures are three points of 250 ° C., 400 ° C., and 650 ° C., and the heat treatment time is 1 hour.
According to this figure, when the heat treatment temperature was 650 ° C., a clear peak of lithium niobate (LiNbO ₃ ) was observed in the diffraction line, and crystallization was evident, whereas when the heat treatment temperature was 400 ° C. or less, No peak was observed in the diffraction line, and it was found to be amorphous.

  Since the perovskite nanoparticles of the present invention are perovskite nanoparticles having a particle size of 50 nm or less and high crystallinity and dispersibility, they are optical waveguides, optical switches, modulation elements, light deflection elements, capacitors, When applied to various devices such as a dielectric memory and a piezoelectric element, high functionality is expected, and its industrial effect is extremely large.

It is a state diagram which shows the two-dimensional state containing the supercritical state of alcohol. It is a figure which shows the powder X-ray-diffraction figure of the white powder of Example 1 of this invention. It is a figure which shows the SEM image of the white powder of Example 1 of this invention. It is a figure which shows the powder X-ray-diffraction figure of the white powder of Example 2 of this invention. It is a figure which shows the SEM image of the white powder of Example 2 of this invention. It is a figure which shows the powder X-ray-diffraction figure of the white powder of Example 3 of this invention. It is a figure which shows the SEM image of the white powder of Example 3 of this invention. It is a figure which shows the SEM image of the white powder of a comparative example. It is a figure which shows the X-ray-diffraction figure at the time of changing the heat processing conditions of the white powder of a comparative example.

Claims (4)

A _x B _y O _z (where A is one or two elements selected from the group of group IA elements, group IB elements, group IIA elements, group IIB elements, and B is selected from transition metal elements 1 A method of producing nanoparticles having a perovskite structure composed of more than one element),
A method for producing perovskite-type nanoparticles, wherein the compound containing A and the compound containing B are reacted in the presence of a supercritical fluid, and then the supercritical fluid is removed without condensation.   The method for producing perovskite nanoparticles according to claim 1, wherein the supercritical fluid is alcohol.   The A is one or two selected from lithium, sodium, potassium, calcium, strontium, and barium, and the B is niobium, tantalum, or niobium and tantalum. Or the manufacturing method of the perovskite type nanoparticle of 2.   The method for producing perovskite nanoparticles according to claim 1, 2 or 3, wherein the compound containing A and the compound containing B are hydroxides.

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