JP7156576B1 - Powder containing barium titanate nanocrystals and method of making same - Google Patents

Abstract

An object of the present invention is to enhance the dispersibility of a powder containing fine barium titanate nanocrystals in a dispersion medium. The powder of the present invention contains barium titanate nanocrystals, and has an average equivalent circle diameter Ld of 12 nm or less, which is determined using a transmission electron microscope image of the powder. Crystallites of barium titanate nanocrystals obtained by Scherrer's formula using the full width at half maximum of the diffraction peak corresponding to the (111) plane of the barium titanate nanocrystals in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the powder. The diameter Lc is 12 nm or less. An organic carboxylic acid is adhered to the surface of the barium titanate nanocrystals, and the average particle size Lp of the powder obtained by dispersing the powder in a nonpolar dispersion medium and determining by a dynamic light scattering method is 18 nm or less. is.

Description

The present invention relates to powders containing barium titanate nanocrystals and methods of making the same.

Fine particles (nanocrystals) of barium titanate (BT) are widely used in electronic devices such as multilayer ceramic capacitors (MLCCs). For example, BT fine particles are added to internal electrodes used in MLCCs for the purpose of increasing the bonding strength between internal electrode layers (metal) and dielectric layers (ceramics) (for example, Non-Patent Document 1). Further, in the sintering of MLCC, since ceramics and metal are sintered at the same time, BT fine particles are added for the purpose of matching the sintering shrinkage curve. With the miniaturization of electronic devices such as MLCCs, it is required to further reduce the size of BT fine particles.

In addition, BT fine particles may be included in the resin for the purpose of improving the refractive index and dielectric constant of the resin. A resin in which fine particles are uniformly dispersed suppresses attenuation of transmitted light due to Rayleigh scattering and improves transparency. Therefore, BT particles that are finer and have excellent dispersibility are desired.

Ryusuke Ueyama et al., ``Influence of Ni powder manufacturing method and amount of BaTiO3 co-material fine particles added on Ni electrode paste sintering characteristics'', Journal of the Ceramic Society of Japan, 110, 676-680 ( 2002)

It is advantageous to store the BT fine particles in powder form rather than to store them dispersed in a dispersion medium in terms of space saving, ease of handling during management and transportation, and the like. However, once the BT fine particles are dried and powdered, they are difficult to redisperse in the dispersion medium due to their strong cohesive force, and it takes an enormous amount of time and labor to obtain a dispersion of the BT fine particles. The finer the BT fine particles, the higher the aggregability. In particular, the single-nano-sized BT fine particles are difficult to disperse uniformly in the dispersion medium.

For example, when an electrode slurry is prepared by blending a powder containing BT fine particles, an electrode material, and a dispersion medium during the production of an internal electrode, the BT fine particles aggregate in the electrode slurry, making it difficult to obtain a homogeneous electrode slurry. The performance of the internal electrode cannot be stably obtained.

Even when a powder containing BT fine particles, a resin, and a dispersion medium are blended to obtain a slurry, and the slurry is used to obtain a resin containing BT fine particles, the BT fine particles agglomerate in the slurry, resulting in a homogeneous slurry. Therefore, sufficient reliability cannot be obtained for the dielectric properties of the resin containing the BT fine particles.

The dispersibility in the dispersion medium of powders containing fine BT microparticles is still insufficient.

In view of the above, one aspect of the present invention provides a powder containing barium titanate nanocrystals, wherein the average equivalent circle diameter Ld of the powder obtained using a transmission electron microscope image of the powder is 12 nm or less. The crystallite diameter Lc of the crystal obtained by Scherrer's equation using the full width at half maximum of the diffraction peak corresponding to the (111) plane of the crystal in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the powder is The average particle size Lp of the powder is 12 nm or less, the surface of the crystal is coated with an organic carboxylic acid, and the powder is dispersed in a nonpolar dispersion medium and determined by a dynamic light scattering method. It relates to powders comprising barium titanate nanocrystals, which are 18 nm or less.

Another aspect of the present invention is a preparation step of obtaining a raw material mixture containing a water-soluble compound containing barium, a compound containing titanium, an organic carboxylic acid, an alkaline component, and water; and a heating step of obtaining barium titanate nanocrystals, wherein the compound containing titanium includes at least one selected from the group consisting of titanium tetrachloride and amorphous titanium hydroxide, and the raw material In the mixture, the molar ratio of the organic carboxylic acid to barium ions is 0.5 or more and 2.0 or less, and the molar ratio of hydroxide ions to barium ions is more than 3.4 and 6.0 or less. relates to a method for producing a powder containing barium titanate nanocrystals.

According to the present invention, the dispersibility of powder containing fine barium titanate nanocrystals in a dispersion medium can be enhanced.
While the novel features of the present invention are set forth in the appended claims, the present invention, both as to construction and content, together with other objects and features of the present invention, will be further developed by the following detailed description in conjunction with the drawings. will be well understood.

FIG. 1 shows an example of XRD patterns of amorphous titanium hydroxide and crystalline titanium hydroxide. a1 in FIG. 1 shows the XRD pattern of the amorphous titanium hydroxide used for producing the powder of Example 2, and b1 in FIG. 1 shows the XRD pattern of the crystalline titanium hydroxide used for producing the powder of Comparative Example 7. indicates 1 is a TEM image of a powder sample of Example 1; 4 is a TEM image of a powder sample of Example 2. FIG. 4 is a TEM image of a powder sample of Example 3. FIG. 4 is a TEM image of a powder sample of Comparative Example 1. FIG. 4 is a TEM image of a powder sample of Comparative Example 2. FIG. 4 is a TEM image of a powder sample of Comparative Example 3. FIG. 4 is a TEM image of a powder sample of Comparative Example 4. FIG. 4 is a TEM image of a powder sample of Comparative Example 5. FIG. 4 is a TEM image of a powder sample of Comparative Example 6. FIG. 4 is a TEM image of a powder sample of Comparative Example 7. FIG.

[Powder containing barium titanate nanocrystals]
A powder according to one embodiment of the present invention comprises fine particles (nanocrystals) of barium titanate (BT). The powder has an average equivalent circle diameter Ld of 12 nm or less, which is obtained using a transmission electron microscope (TEM) image of the powder. The crystallite diameter Lc of the BT nanocrystals is 12 nm or less. The crystallite size Lc is determined by Scherrer's formula using the full width at half maximum of the diffraction peak corresponding to the (111) plane of the crystal in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the powder. An organic carboxylic acid adheres to the surface of the BT nanocrystals contained in the powder. The powder has an average particle size Lp of 18 nm or less, which is obtained by a dynamic light scattering (DLS) method by dispersing the powder in a nonpolar dispersion medium. The average equivalent circle diameter Ld refers to the average value (arithmetic mean) of the equivalent circle diameters of the nanocrystals contained in the powder. The equivalent circle diameter refers to the diameter of a circle having a size corresponding to the area of one side of the BT nanocrystal. The average particle size Lp refers to the particle size (median size) at an integrated value of 50% in the number-based particle size distribution.

Dispersed in a dispersion medium containing fine BT nanocrystals having an average equivalent circle diameter Ld of 12 nm or less and a crystallite diameter Lc of 12 nm or less and having an average particle diameter Lp of 18 nm or less by the production method of the embodiment described later. A powder with excellent properties is obtained. The fact that organic carboxylic acid adheres to the crystal surface is considered to be one of the factors for improving the dispersibility of the powder.

By the production method of the embodiment described later, fine BT nanocrystals having an average equivalent circle diameter Ld of 10 nm or less (or 9 nm or less) and a crystallite diameter Lc of 10 nm or less (or 9 nm or less) are included, and the average particle diameter Lp It is also possible to obtain a powder having a particle size of 10 nm or less and excellent dispersibility in a dispersion medium.

When the average equivalent circle diameter Ld is 12 nm or less and the crystallite diameter Lc is 12 nm or less, it is advantageous in miniaturizing the electronic device and improving the transparency of the resin containing the BT nanocrystals. Moreover, in the above case, sintering at a low temperature (for example, firing at a low temperature in the process of manufacturing the MLCC) becomes possible.

When the average particle size Lp is 18 nm or less, the electrode paste containing the BT nanocrystals, the electrode material, and the dispersion medium can be easily homogenized, and the performance of the internal electrodes produced using the electrode paste can be stably obtained. In addition, the BT nanocrystals are easily dispersed uniformly in the resin, and the reliability of the dielectric constant and refractive index of the resin containing the BT nanocrystals is improved.

The Lp value may vary depending on the crystal size distribution (the range and variation of the equivalent circle diameter of crystals) and the state of adhesion of the organic carboxylic acid. Even when no agglomeration of crystals is observed in the TEM image of the powder, the crystals may agglomerate strongly in the dispersion medium, and Lp/Ld may become 2 or more. The state of aggregation of crystals observed in the TEM image does not suggest the dispersibility of the powder in the dispersion medium.

In the powder containing BT nanocrystals of the present invention, the ratio of the average particle diameter Lp to the average equivalent circle diameter Ld (hereinafter also referred to as the degree of aggregation): Lp/Ld is, for example, greater than 1 due to the improved dispersibility. , less than 2, or in the range of 1.1 to 1.75.

It is preferable that the coefficient of variation of the equivalent circle diameter of nanocrystals measured in the process of determining the average equivalent circle diameter Ld using a TEM image of the powder is 20% or less. In this case, the variation in crystal size is reduced, the electrode paste containing the BT nanocrystals, the electrode material, and the dispersion medium can be easily homogenized, and the performance of the internal electrodes produced using the electrode paste can be stably obtained.

In the BT nanocrystals, the molar ratio of barium to titanium: Ba/Ti is preferably 0.95 or more and 1.1 or less, and the BT nanocrystals are preferably composed of a single phase of barium titanate. In this case, the BT nanocrystals have high crystallinity, and the crystallite diameter Lc is likely to be close to the average circle equivalent diameter Ld. In this case, the ratio of the crystallite diameter Lc to the average equivalent circle diameter Ld (hereinafter also referred to as crystallinity): Lc/Ld is obtained, for example, in the range of 0.9 or more and less than 1.1. In this case, it is advantageous in terms of improving the dielectric constant and refractive index of the resin containing the BT nanocrystals. In addition, when the Ba/Ti molar ratio in the powder containing BT nanocrystals is 0.95 or more, the barium defect on the surface of the BT nanocrystals becomes very small, which is advantageous in improving the dielectric constant. When the Ba/Ti molar ratio in the powder containing BT nanocrystals is 1.1 or less, the amount of compounds containing barium other than barium titanate (barium carbonate, etc.) contained in the powder becomes very small, and the dielectric device This is advantageous in terms of thinning the film and improving reliability.

The organic carboxylic acid deposited on the surface of the BT nanocrystals may include oleic acid. In the powder, the amount of the organic carboxylic acid deposited may be 15% by mass or more and 25% by mass or less with respect to the entire powder. Even after performing the washing step and/or the classification step described below, the organic carboxylic acid in the above range may remain on the surface of the BT nanocrystals contained in the obtained powder. When the amount of the organic carboxylic acid to be adhered is within the above range, the dispersibility of the powder in the dispersion medium is likely to be improved.

A powder according to an embodiment of the present invention (a powder containing BT nanocrystals) may satisfy at least one of the following (1) to (9).
(1) The average equivalent circle diameter Ld may be 4.0 nm or more, or 7.0 nm or more. The average equivalent circle diameter Ld may be 12.0 nm or less, or 11.3 nm or less. The average equivalent circle diameter Ld may be 4.0 nm or more and 12.0 nm or less, or may be 7.0 nm or more and 11.3 nm or less.
(2) The crystallite size Lc may be 4.0 nm or more, or 7.5 nm or more. The crystallite size Lc may be 12.0 nm or less, or 11.1 nm or less. The crystallite size Lc may be 4.0 nm or more and 12.0 nm or less, or may be 7.5 nm or more and 11.1 nm or less.
(3) The average particle size Lp may be 4.0 nm or more, or 9.4 nm or more. The average particle size Lp may be 18.0 nm or less. The average particle size Lp may be 4.0 nm or more and 18.0 nm or less, or may be 9.4 nm or more and 18.0 nm or less. (4) The molar ratio of barium to titanium in the BT nanocrystals: Ba/Ti may be 0.95 or greater, or 0.99 or greater. The molar ratio Ba/Ti may be 1.10 or less, or 1.09 or less. The molar ratio Ba/Ti may be 0.95 or more and 1.10 or less, or may be 0.99 or more and 1.09 or less.
(5) The ratio of the amount of organic carboxylic acid adhered to the entire powder may be 15% by mass or more, or 19% by mass or more. The proportion may be 25% by mass or less, or 21% by mass or less. The proportion may be 15% by mass or more and 25% by mass or less, or 19% by mass or more and 21% by mass or less.
(6) The above ratio Lc/Ld may be 0.90 or more, or 0.94 or more. The ratio Lc/Ld may be less than 1.10 and may be 1.08 or less. The ratio Lc/Ld may be 0.90 or more and less than 1.10, or may be 0.94 or more and 1.08 or less.
(7) The aforementioned ratio Lp/Ld may be greater than 1.0 or greater than or equal to 1.1. The ratio Lp/Ld may be less than 2.0 or less than or equal to 1.6. The ratio Lp/Ld may be greater than 1.0 and less than 2.0, or may be greater than or equal to 1.1 and less than or equal to 1.6.
(8) The coefficient of variation may be 0.0% or more, or 7.0% or more. The coefficient of variation may be 20.0% or less, or 19.1% or less. The coefficient of variation may be 0.0% or more and 20.0% or less, or may be 7.0% or more and w19.1% or less.
(9) The proportion of the BT nanocrystalline particles (BT nanocrystalline particles having surfaces coated with organic carboxylic acid) in the powder is 90% by mass or more, 95% by mass or more, or 99% by mass or more. good too. The powder may consist essentially of the BT nanocrystalline particles, or may consist solely of the BT nanocrystalline particles.

The measurement method will be described below.
(Average circle equivalent diameter Ld)
The average equivalent circle diameter Ld is determined using a transmission electron microscope (TEM) image of the powder. Specifically, it is obtained by the following method.

(i) Preparation of sample for TEM observation of BT nanocrystals 0.1 g of BT nanocrystal powder was added to 10 mL of toluene and irradiated with ultrasonic waves for 1 minute using an ultrasonic cleaner (manufactured by SND, US-106). to obtain a dispersion of BT nanocrystals. A dispersion of BT nanocrystals is dropped onto a support film of a TEM grid and air-dried to obtain a sample for TEM observation.

(ii) Photographing of TEM image The above sample for TEM observation is provided to a TEM (JEM-2100F manufactured by JEOL Ltd.) to obtain an image of BT nanocrystals. The magnification of the TEM image is appropriately adjusted within a range in which about 300 to 600 crystal grains are included. By measuring about 300 or more crystal grains, proper evaluation with small variation is possible.

(iii) Image processing The TEM image of the aggregate is processed using image analysis software (WinROOF2015 manufactured by Mitani Shoji Co., Ltd.). Specifically, the contrast of the TEM image is appropriately adjusted, binarization processing is performed, and the region occupied by crystals and the region other than the region occupied by crystals are distinguished. Note that the organic carboxylic acid adhered to the crystal surface is contained in a region other than the region occupied by the crystal. The contrast value is set to 20 or more, for example. In the binarization process, processing is performed by specifying a luminance range based on the luminance histogram. The lower limit of the threshold is set to 0, and the upper limit of the threshold is appropriately set within a range larger than 0 and equal to or lower than the peak top of the histogram.

(iv) Measurement of equivalent circle diameter and calculation of average equivalent circle diameter Ld After binarization, select "equivalent circle diameter" from the "shape feature" function, Equivalent circle diameters are determined for each, and the arithmetic mean of these values is determined as the average equivalent circle diameter Ld. Note that the equivalent circle diameter refers to the diameter of a circle having a size corresponding to the area of one side surface of the BT nanocrystal.

(Variation coefficient of equivalent circle diameter)
The coefficient of variation of the equivalent circle diameter is calculated using the equivalent circle diameter of each nanocrystal measured in the process of determining the average equivalent circle diameter Ld of the powder. Specifically, the variation coefficient of the equivalent circle diameter is calculated using the equivalent circle diameter obtained for each of about 300 to 600 BT nanocrystals in (iv) above. The coefficient of variation is the relative standard deviation, which is the value obtained by dividing the standard deviation by the arithmetic mean.

(Ba/Ti molar ratio of BT nanocrystals)
The Ba/Ti molar ratio of BT nanocrystals can be obtained by performing a composition analysis on the BT nanocrystal powders by X-ray fluorescence spectroscopy (XRF). A fluorescent X-ray spectrometer (ZSX PrimusII) manufactured by Rigaku Corporation can be used for the XRF analysis. A calibration curve method is used for quantitative analysis.

(Average particle size Lp)
The average particle size Lp is obtained by dispersing the powder in a non-polar dispersion medium and using the DLS method. A non-polar dispersion medium includes a low-polarity organic dispersion medium. As the dispersion medium, a nonpolar (low polarity) aromatic hydrocarbon dispersion medium (eg, toluene, benzene) or an aliphatic hydrocarbon dispersion medium (eg, hexane) can be used. Specifically, it is obtained by the following method.

0.1 g of BT nanocrystal powder is added to 10 mL of toluene, and ultrasonic waves are applied for 1 minute using an ultrasonic cleaner (manufactured by SND, US-106) to obtain a dispersion. The dispersion is transferred to a quartz cell, and the average particle size Lp is measured using a dynamic light scattering particle size distribution analyzer (Nanopartica SZ-100-HZ, manufactured by Horiba, Ltd.). The solvent refractive index is 1.496 and the solvent viscosity is 0.567 mPa·s. The distribution form is "standard" and the degree of dispersion is "monodisperse". The average particle size Lp means the particle size (median size) when the integrated value is 50% in the number-based particle size distribution. Although toluene is used as the dispersion medium in the above description, a non-polar dispersion medium other than toluene may be used. However, toluene may be used as a dispersion medium for the measurement unless a particular problem arises.

The surface of the BT nanocrystals contained in the powder is coated with an organic carboxylic acid derived from the material added to the raw material mixture described below. When the powder is put into the dispersion medium, the BT nanocrystals with the organic carboxylic acid coated on the surface are dispersed in the dispersion medium. The average particle size of BT nanocrystals with organic carboxylic acid deposited on the surface is determined by the DLS method.

(Deposition amount of organic carboxylic acid on BT nanocrystal surface)
5 g of BT nanocrystal powder is placed in an alumina crucible, heated in a constant temperature bath at 130° C. for 30 minutes, and the mass W1 (g) of the solid content after drying is measured. Next, the dried solid content is calcined at 800° C. for 2 hours, and the mass W2 (g) of the calcined solid content is measured. The organic carboxylic acid adhered to the crystal surface is decomposed and volatilized during the firing. Using the obtained W1 and W2, the deposition amount (% by mass) of the organic carboxylic acid is determined from the following formula.
Amount of organic carboxylic acid deposited = (1-W2/W1) x 100

[Method for producing barium titanate nanocrystals]
A production method according to an embodiment of the present invention (a method for producing a powder containing BT nanocrystals) comprises a water-soluble compound containing barium, a compound containing titanium, an organic carboxylic acid, an alkaline component, water, and a heating step of heating the raw material mixture to obtain BT nanocrystals. BT nanocrystals can have a cubic or near-cubic shape.

The compound containing titanium includes at least one selected from the group consisting of titanium tetrachloride and amorphous titanium hydroxide. In the raw material mixture, the molar ratio of the organic carboxylic acid to barium ions is 0.5 or more and 2.0 or less, and the molar ratio of hydroxide ions to barium ions is more than 3.4 and 6.0 or less. is.

The molar ratio of the organic carboxylic acid to barium ions is the ratio of the molar amount of the organic carboxylic acid to the molar amount of Ba ions, and is hereinafter also referred to as the (organic carboxylic acid/Ba ion) molar ratio. The molar ratio of hydroxide ions to barium ions is the ratio of the molar amount of hydroxide ions to the molar amount of Ba ions, and is hereinafter also referred to as the (hydroxide ion/Ba ion) molar ratio. The molar amount of Ba ions mentioned above refers to the molar amount of Ba ions when all Ba derived from a water-soluble compound containing barium is present as ions in the raw material mixture.

The molar amount of the organic carboxylic acid mentioned above refers to the molar amount of the organic carboxylic acid added to the raw material mixture, and the organic carboxylic acid may or may not be ionized. However, when two or more carboxy groups are contained in one molecule of the organic carboxylic acid (when the organic carboxylic acid is, for example, a dicarboxylic acid or a carboxylic acid anhydride (the hydrolyzate thereof in the raw material mixture)), the organic The molar amount of carboxylic acid is converted to the molar amount of carboxy groups contained in the organic carboxylic acid.

The molar amount of hydroxide ions mentioned above refers to the molar amount of hydroxide ions present in the raw material mixture. The hydroxide ions present in the raw material mixture refer to hydroxide ions remaining in the raw material mixture after the neutralization reaction of the alkaline component and the acid component contained in the raw material. The molar amount of hydroxide ions can be calculated from the charged amount of raw materials.

By using a specific compound as the titanium source and adjusting the molar ratio of (organic carboxylic acid/Ba ion) and (hydroxide ion/Ba ion) to a specific range, single nano-sized fine BT nano It is possible to obtain a powder that contains crystals and is excellent in dispersibility. The reason why the dispersibility of the powder containing fine BT nanocrystals is improved is not clear, but the compound used as the titanium source and the molar ratio of the above two contribute to the refinement of the BT nanocrystals and the improvement of the dispersibility of the powder. It is considered that

As a method for enhancing the dispersibility of the powder, a method of adding a dispersant to the powder and applying a strong shear by a bead mill is conceivable. However, in this method, impurities derived from the beads are mixed, and the quality of the powder tends to deteriorate. Poor quality powders, for example, degrade the performance of electronic devices. Moreover, it takes time and effort, and is disadvantageous in terms of cost and productivity.

On the other hand, the method for producing BT nanocrystals according to the embodiment of the present invention can efficiently improve the dispersibility of the powder by using the organic carboxylic acid used as the raw material, unlike the above-described method using a bead mill. It is advantageous in terms of productivity. In addition, since beads are not used in the production method of the present embodiment, deterioration of the quality of the powder due to contamination of impurities derived from the beads is suppressed, and deterioration of the performance of the electronic device due to deterioration of the quality of the powder is suppressed.

In the production method of the present embodiment, a powder having a coefficient of variation of equivalent circle diameter of BT nanocrystals of 20% or less can be obtained. On the other hand, in the above method using a bead mill, the crystal size tends to become non-uniform as the powder becomes finer due to the strong impact of the beads, and it is difficult to obtain a powder with a coefficient of variation of 20% or less.

In the production method of the present embodiment, a powder containing highly crystalline BT nanocrystals with Lc/Ld of 0.9 or more and less than 1.1 can be obtained. On the other hand, in the above-described method using a bead mill, the crystallinity of the powder tends to decrease due to the strong impact of the beads, and it is difficult to obtain a powder containing highly crystalline BT nanocrystals with Lc/Ld within the above range.

When the molar ratio of (organic carboxylic acid/Ba ion) is less than 0.5, the amount of organic carboxylic acid attached to the crystal surface becomes small, BT nanocrystals grow unevenly, and the average circle equivalent diameter Ld can be larger than 12 nm. Also, the dispersibility of the powder is reduced. The organic carboxylic acid adhering to the crystal surface is considered to be one of the factors for improving the dispersibility of the powder. When the (organic carboxylic acid/Ba ion) molar ratio exceeds 2, the viscosity of the raw material mixture increases, the size of the resulting BT nanocrystals becomes non-uniform, and the average equivalent circle diameter Ld becomes larger than 12 nm. be. In addition, the reactivity is lowered, and sufficient BT nanocrystals cannot be obtained.

The smaller the (hydroxide ion/Ba ion) molar ratio, the larger the average equivalent circle diameter Ld and the crystallite diameter Lc. When the (hydroxide ion/Ba ion) molar ratio is 3.4 or less, the average equivalent circle diameter Ld and the crystallite diameter Lc may be larger than 12 nm. Also, the dispersibility of the powder may deteriorate. If the (hydroxide ion/Ba ion) molar ratio exceeds 6, the crystal growth becomes non-uniform, and the size variation increases due to the presence of coarse crystals and the like.

The molar ratio of (hydroxide ion/Ba ion) may be 3.6 or more and 6.0 or less, may be 3.8 or more and 5.5 or less, 3.8 or more and 5 .0 or less.

The concentration of hydroxide ions in the raw material mixture may be, for example, 0.5 mol/L or more and 3.0 mol/L or less, or may be 0.8 mol/L or more and 2.0 mol/L or less. good. The concentration of hydroxide ions in the raw material mixture is the molar amount of hydroxide ions present in the raw material mixture. Refers to the value obtained by dividing by the total volume (liters).

[Preparation step of raw material mixture]
In this step, a raw material mixture containing barium ions (Ba ²⁺ ) and titanium is obtained. Titanium in the raw material mixture may be present in the form of titanium ions (Ti ⁴⁺ ) and/or compounds (eg, precipitates). In the preparation of the raw material mixture, a barium source (a water-soluble compound containing barium) and a titanium source (a compound containing titanium) are used, for example, at a molar ratio of barium to titanium: Ba/Ti of 0.95 or more. 5 or less (preferably 0.97 or more and 1.2 or less). In this case, highly crystalline BT nanocrystals are easily obtained. In the preparation step, a water-soluble compound containing barium, a compound containing titanium, and water are added to obtain an aqueous solution (or mixture) containing barium ions and titanium, and then an organic compound is added to the aqueous solution (or mixture). A carboxylic acid and an alkaline component may be added. The water-soluble compound containing barium and the compound containing titanium may each be used as an aqueous solution.

The water-soluble compound containing barium is, for example, a water-soluble barium salt, which may be dissolved in water in the preparation process described above. It may be dissolved by heating in the process (for example, barium salts of higher fatty acids such as barium oleate). Water-soluble barium salts include barium chloride, barium hydroxide, barium salts of fatty acids, barium nitrate, and the like. Among them, the water-soluble barium salt is preferably barium hydroxide. Barium hydroxide does not contain other elements than barium titanate and constituent elements of water. Therefore, when barium hydroxide is used as the barium source, contamination of impurities derived from other elements is suppressed in the synthesis of BT nanocrystals, and high-quality BT nanocrystals are easily obtained stably. The water-soluble compound containing barium may be used singly or in combination of two or more.

The concentration of Ba ions in the raw material mixture may be 0.2 mol/L or more and 2.0 mol/L or less, or may be 0.2 mol/L or more and 1.0 mol/L or less. In this case, it is easy to efficiently obtain high-quality barium titanate nanocrystals. In addition, the concentration of Ba ions in the raw material mixture is the molar amount of Ba ions when all the Ba derived from the water-soluble barium salt is present as ions in the raw material mixture, and each raw material used for preparing the raw material mixture (water It refers to the value obtained by dividing the total amount (liters) of water contained in

(compound containing titanium)
The compound containing titanium includes at least one selected from the group consisting of titanium tetrachloride and amorphous titanium hydroxide. When using these compounds, the uniformity of the crystal size can be improved while miniaturizing the BT nanocrystals.

The fact that titanium hydroxide is amorphous can be confirmed based on the XRD pattern of titanium hydroxide obtained by X-ray diffraction (XRD) measurement of CuKα rays. Specifically, in the XRD pattern of titanium hydroxide, the average value B and the standard deviation σ of the reflection intensity in the range of 2θ from 20 ° to 22 °, and the reflection intensity in the range of 24 ° to 26 ° Titanium hydroxide is considered to be amorphous when the maximum intensity value P satisfies the relationship (P−B)<20×σ.

Here, FIG. 1 shows an example of XRD patterns of amorphous titanium hydroxide and crystalline titanium hydroxide. a1 in FIG. 1 shows the XRD pattern of the amorphous titanium hydroxide used for producing the powder of Example 2, which will be described later. b1 in FIG. 1 shows the XRD pattern of the crystalline titanium hydroxide used for producing the powder of Comparative Example 7, which will be described later. The XRD pattern of a1 has (P−B)=71.7 and 20×σ=152.6, satisfying the above relationship. The XRD pattern of b1 has (P−B)=258.1 and 20×σ=169.0, which does not satisfy the above relationship.

Amorphous titanium hydroxide can be obtained, for example, by hydrolyzing an aqueous solution of titanium tetrachloride at 5° C. to 40° C. while adding an alkaline solution containing sodium hydroxide or the like to produce colloidal amorphous titanium hydroxide. Obtained by precipitation.

(organic carboxylic acid)
Organic carboxylic acids play a role in controlling crystal size. The organic carboxylic acid is coordinated to the crystal surface of barium titanate, which controls crystal growth and can regulate crystal size.

The organic carboxylic acid preferably contains a fatty acid having a main chain of 6 or more carbon atoms. The number of carbon atoms in the main chain of the fatty acid is preferably 10 or more, more preferably 15 or more. Fatty acids may be saturated or unsaturated. Saturated fatty acids having a main chain of 15 or more carbon atoms include, for example, palmitic acid and stearic acid. Examples of unsaturated fatty acids having a main chain of 15 or more carbon atoms include oleic acid, linoleic acid, linolenic acid, eleostearic acid, and arachidonic acid. Among them, oleic acid is preferable from the viewpoint of easy formation of hexahedral nanocrystals. One type of organic carboxylic acid may be used alone, or two or more types may be used in combination.

In the raw material mixture, the (organic carboxylic acid/Ba ion) molar ratio may be 0.7 or more and 1.65 or less, or may be 0.7 or more and 1.5 or less. In this case, the (100) plane and the (111) plane of the barium titanate crystal can be easily grown in a well-balanced manner, and variations in crystal shape and size can be reduced.

The concentration of the organic carboxylic acid (eg, oleic acid) in the raw material mixture may be, for example, 0.15 mol/L or more and 0.5 mol/L or less. In addition, the concentration of the organic carboxylic acid in the raw material mixture is the molar amount of the organic carboxylic acid put into the raw material mixture, and the total amount (liter) of water contained in each raw material (including water) used to prepare the raw material mixture. refers to the value obtained by dividing by

(Alkaline component)
By including an alkali component in the raw material mixture, it is possible to promote crystal growth and reduce variations in crystal shape. From the viewpoint of cost reduction, reduction of environmental load, etc., the alkali component preferably contains an alkali metal hydroxide. Alkali metal hydroxides include, for example, sodium hydroxide and potassium hydroxide. Among them, the alkali metal hydroxide is preferably sodium hydroxide.

The concentration of sodium hydroxide in the raw material mixture may be, for example, 0.5 mol/L or more and 3.0 mol/L or less. In addition, the concentration of sodium hydroxide in the raw material mixture is the molar amount of sodium hydroxide put into the raw material mixture, and the total amount (liter) of water contained in each raw material (including water) used to prepare the raw material mixture. refers to the value obtained by dividing by

The alkali component may contain an amine compound for the purpose of reducing variations in crystal shape. Amine compounds include, for example, primary amine compounds such as tert-butylamine, secondary amine compounds such as dimethylamine, and tertiary amine compounds such as trimethylamine. Amine compounds are highly ecotoxic and expensive, so the alkaline component preferably does not contain an amine compound. By adjusting the hydroxide ion concentration using an alkali metal hydroxide without using an amine compound, the variation in crystal shape can be reduced.

[Heating process of raw material mixture]
In this step, the raw material mixture is heated to synthesize barium titanate. That is, BT nanocrystals are obtained. Barium titanate can be obtained using a hydrothermal reaction, and the raw material mixture may be heated while being stirred. The heating temperature is preferably 150° C. or higher and 240° C. or lower from the viewpoint of easily obtaining high-quality BT nanocrystals efficiently. When the heating temperature is 150° C. or higher, the synthesis reaction of barium titanate tends to proceed smoothly. When the heating temperature is 240° C. or lower, decomposition of the organic carboxylic acid is suppressed, and the effect of crystal shape control by the organic carboxylic acid can be obtained more reliably. The heating time may be, for example, 1 hour or more and 80 hours or less, or 12 hours or more and 48 hours or less, from the viewpoint of allowing the reaction to proceed sufficiently and improving productivity.

[BT nanocrystal washing process]
Furthermore, after the heating step, a washing step may be performed in which the BT nanocrystals are dispersed in alcohol and washed. As alcohol, for example, ethanol, methanol, 2-propanol, etc. are used. In the washing step, the BT nanocrystals obtained in the heating step are separated from water (including residual components such as organic carboxylic acids dissolved in water). Even after the washing process, organic carboxylic acid is still attached to the crystal surface to some extent.

The washing step includes, for example, a step (a) of adding alcohol to the reaction solution (water containing BT nanocrystals) after the heating step and then centrifuging to obtain a precipitate; and (b) obtaining a precipitate by centrifugation. Step (b) may be repeated multiple times. In step (a), it is preferable to sufficiently mix the reaction solution and the alcohol before centrifugation.

[BT nanocrystal classification step]
Furthermore, after the heating step, a classification step of dispersing the BT nanocrystals in a non-polar dispersion medium and classifying them by centrifugation may be performed. The classification step is preferably performed after the washing step. Dispersion methods include, for example, ultrasonic treatment and stirring with a stirring blade. A non-polar dispersion medium includes a low-polarity organic dispersion medium. As the dispersion medium, a nonpolar (low polarity) aromatic hydrocarbon dispersion medium (eg, toluene, benzene) or an aliphatic hydrocarbon dispersion medium (eg, hexane) can be used. In the classification step, coarse crystals are removed from the barium titanate crystals, and BT nanocrystals of appropriate size are recovered.

[Step of obtaining powder containing BT nanocrystals]
After the above washing step and/or classification step, the dispersion medium in the supernatant may be removed by air drying or the like to obtain BT nanocrystal powder. At this time, the residual organic carboxylic acid adheres to the surface of the BT nanocrystals contained in the powder to some extent. Storing BT nanocrystals in powder form is more advantageous than storing them dispersed in a dispersion medium in terms of space saving, ease of handling (easiness of management), cost, and the like.

A manufacturing method according to an embodiment of the present invention (a method for manufacturing a powder containing BT nanocrystals) may satisfy at least one of the following (1) and (2).
(1) In the raw material mixture, the molar ratio of organic carboxylic acid to barium ions is 0.5 or more, and may be 0.8 or more. The molar ratio is 2.0 or less, and may be 1.6 or less. The molar ratio may be 0.5 or more and 1.6 or less, 0.8 or more and 2.0 or less, or 0.8 or more and 1.6 or less.
(2) In the raw material mixture, the molar ratio of hydroxide ions to barium ions is greater than 3.4 and may be 3.8 or more. The molar ratio is 6.0 or less, and may be 5.3 or less. The molar ratio may be greater than 3.4 and no greater than 5.3, may be no less than 3.8 and no greater than 6.0, or may be no less than 3.8 and no greater than 5.3.

[Example]
Examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.
<<Example 1>>
(Preparation step of raw material mixture)
7 g of titanium tetrachloride aqueous solution, 50 g of ion-exchanged water, and 6 g of barium hydroxide octahydrate were put into a 300 mL polytetrafluoroethylene beaker and stirred for 3 minutes. Thus, an aqueous solution containing titanium tetrachloride as a titanium source and barium hydroxide as a barium source was obtained. A titanium tetrachloride aqueous solution (concentration: 3.9 mol/L in terms of TiO ₂ ) manufactured by Osaka Titanium Technologies Co., Ltd. was used as the titanium tetrachloride aqueous solution. As barium hydroxide octahydrate, product code 020-00242 (reagent special grade) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used.

While stirring the aqueous solution containing the titanium source and the barium source, 15.8 mL of a 7.5 M sodium hydroxide aqueous solution and 5.9 mL of oleic acid were added in this order to the aqueous solution and stirred for 5 minutes. As sodium hydroxide, product code 198-13765 (reagent special grade) manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. was used. As oleic acid, PM500 (trade name) manufactured by Miyoshi Oil Co., Ltd. was used. Thus, a raw material mixture was prepared. The molar ratio of Ba and Ti contained in the raw material mixture was 1:1.

The concentrations of Ba ions and titanium in the raw material mixture were each 0.25 mol/L. The concentration of sodium hydroxide in the raw material mixture was 1.63 mol/L. The concentration of oleic acid in the raw material mixture was 0.20 mol/L. The hydroxide ion concentration in the raw material mixture was 1.01 mol/L. In the raw material mixture, the (oleic acid/Ba ion) molar ratio was 0.80. In the raw material mixture, the molar ratio of (hydroxide ions/Ba ions) was 4.04.

(Heating process of raw material mixture)
The raw material mixture prepared above is transferred to a 100 mL PTFE container (manufactured by Sanai Kagaku, HUT-100), and a hot stirrer reaction decomposition device (manufactured by Sanai Kagaku, aluminum block: RDV-TMS-100 and hot stirrer: HHE-19G-U) and heated with stirring. Stirring was performed at a rotation speed of 536 rpm, the heating temperature was 230° C., and the heating time was 24 hours. Thus, barium titanate was synthesized in water. That is, BT nanocrystals were obtained.

(BT nanocrystal washing process)
The BT nanocrystals obtained in the heating step were dispersed in ethanol and washed.
Specifically, 20 mL of ethanol was added to the reaction solution (water containing BT nanocrystals) after the hydrothermal reaction, which was transferred to a centrifuge tube, and the centrifuge tube was placed in a hot bath whose temperature was controlled at 50°C to 70°C. After heating by standing still for 1 minute, the reaction liquid was dispersed in ethanol by shaking the centrifuge tube. The centrifuge tube was set in a tabletop laboratory centrifuge (manufactured by Sigma, 3-16L), centrifuged at a centrifugal acceleration of 2500 G for 10 seconds, and the entire supernatant was removed to obtain a precipitate (step (a)). .

Next, after adding 40 mL of ethanol to the sediment in the centrifuge tube, the mixture was heated and stirred in the same manner as above to disperse the sediment in ethanol. Thereafter, centrifugation was performed in the same manner as described above, and the entire amount of the supernatant was removed to obtain a precipitate (step (b)). Step (b) was performed twice.

(Step of obtaining powder containing BT nanocrystals)
After the washing step, the dispersion of BT nanocrystals was transferred to an evaporating dish and air-dried overnight in a fume hood to obtain a powder containing BT nanocrystals.

<<Example 2 and Comparative Example 4>>
Amorphous titanium hydroxide was produced by the following method.
After adding 74 mL of water to 7.4 mL of titanium tetrachloride aqueous solution (manufactured by Osaka Titanium Technologies, concentration: 3.9 mol / L in terms of TiO ₂ ), stirring at a temperature of 36 ° C., 7.5 M sodium hydroxide aqueous solution 9 0.5 mL was added and stirred for an additional 5 minutes. Thus, titanium tetrachloride was hydrolyzed to obtain a precipitate. As sodium hydroxide, product code 198-13765 (reagent special grade) manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. was used. The obtained precipitate was filtered and washed with pure water until the conductivity of the filtrate became 5 mS/m or less. Amorphous titanium hydroxide was thus obtained. The XRD pattern of the obtained amorphous titanium hydroxide is shown in a1 in FIG.

Amorphous titanium hydroxide was dispersed in water to obtain a slurry containing amorphous titanium hydroxide (concentration: 0.52 mol/L in terms of Ti). In the raw material mixture preparation step, a slurry containing amorphous titanium hydroxide was used instead of the titanium tetrachloride aqueous solution.

In addition, in the raw material mixture preparation step, the amount of sodium hydroxide added to the aqueous solution containing the titanium source and the barium source was varied to set the concentrations of sodium hydroxide in the raw material mixture to the values shown in Table 1, respectively. Table 1 shows the concentration of hydroxide ions and the molar ratio of (hydroxide ions/Ba ions) in the raw material mixture.
A powder containing BT nanocrystals was produced in the same manner as in Example 1 except for the above.

<<Example 3 and Comparative Examples 2, 3 and 5>>
In the preparation process of the raw material mixture, the amounts of sodium hydroxide and oleic acid added were varied to set the concentrations of sodium hydroxide and oleic acid in the raw material mixture to the values shown in Table 1, respectively. Table 1 shows the concentration of hydroxide ions in the raw material mixture, and the molar ratios of (oleic acid/Ba ions) and (hydroxide ions/Ba ions).
A powder containing BT nanocrystals was produced in the same manner as in Example 1 except for the above.

<<Comparative example 1>>
In the raw material mixture preparation step, a titanium bis(ammonium lactate) dihydroxide (TALH) aqueous solution was used instead of the titanium tetrachloride aqueous solution.

Further, the concentration of sodium hydroxide in the raw material mixture was adjusted to the values shown in Table 1 by changing the amount of sodium hydroxide added. Table 1 shows the concentration of hydroxide ions and the molar ratio of (hydroxide ions/Ba ions) in the raw material mixture.
A powder containing BT nanocrystals was produced in the same manner as in Example 1 except for the above.

<<Comparative Example 6>>
In the raw material mixture preparation step, the amounts of the slurry containing barium hydroxide octahydrate (barium source) and amorphous titanium hydroxide (titanium source) are varied to adjust the concentrations of Ba ions and titanium in the raw material mixture. , and the values shown in Table 1, respectively.

Also, in the raw material mixture preparation process, the amounts of sodium hydroxide and oleic acid added were varied to set the concentrations of sodium hydroxide and oleic acid in the raw material mixture to the values shown in Table 1, respectively. Table 1 shows the concentration of hydroxide ions in the raw material mixture, and the molar ratios of (oleic acid/Ba ions) and (hydroxide ions/Ba ions).
A powder containing BT nanocrystals was produced in the same manner as in Comparative Example 4 except for the above.

<<Comparative Example 7>>
Crystalline titanium hydroxide was prepared by the following method.
After adding 74.4 mL of water to 6.8 mL of an aqueous titanium tetrachloride solution (manufactured by Osaka Titanium Technologies Co., Ltd., 3.9 mol/L in terms of TiO ₂ ), a 7.5 M sodium hydroxide aqueous solution was added while stirring at a temperature of 60 ° C. 8.8 mL was added and stirred for an additional 5 minutes. Thus, titanium tetrachloride was hydrolyzed to obtain a precipitate. As sodium hydroxide, product code 198-13765 (reagent special grade) manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. was used. The obtained precipitate was filtered and washed with pure water until the conductivity of the filtrate became 5 mS/m or less. Crystalline titanium hydroxide was thus obtained. The XRD pattern of the obtained crystalline titanium hydroxide is shown in b1 in FIG.

Crystalline titanium hydroxide was dispersed in water to obtain a slurry containing crystalline titanium hydroxide (concentration: 0.52 mol/L in terms of Ti). In the step of preparing the raw material mixture, a slurry containing crystalline titanium hydroxide was used instead of the titanium tetrachloride aqueous solution.

Also, in the raw material mixture preparation process, the amounts of sodium hydroxide and oleic acid added were varied to set the concentrations of sodium hydroxide and oleic acid in the raw material mixture to the values shown in Table 1, respectively. Table 1 shows the concentration of hydroxide ions in the raw material mixture, and the molar ratios of (oleic acid/Ba ions) and (hydroxide ions/Ba ions).
A powder containing BT nanocrystals was produced in the same manner as in Example 1 except for the above.

[evaluation]
XRD measurement was performed on each powder of the examples obtained above, and it was confirmed that the barium titanate single phase was present. In addition, the following evaluations were performed for each of the powders of Examples and Comparative Examples obtained above. The average equivalent circle diameter Ld and the coefficient of variation of the equivalent circle diameter were determined by the method described above (procedures (i) to (iv) above).

For the image processing (iii) above, image analysis software (WinROOF2015, manufactured by Mitani Shoji Co., Ltd.) was used to process the TEM image of the powder sample according to the following procedure.
A TEM image of the powder sample was read with the above image analysis software, and scale calibration was performed. Specifically, using the "manual calibration" function, the length of the scale bar described in the analysis conditions column of the TEM image was measured and matched with the actual size value. Next, the rectangular ROI was used to select the entire area except for the analysis condition column displayed below the TEM image, and the selected area was clipped to extract the image area related to the crystal grains. Next, in order to emphasize the contrast of the TEM image, the "brightness/contrast" function was used and the contrast value was set to 60. Next, median processing was performed to average the brightness. For median processing, the "filter" function was used with a filter size of 9x9 pixels. Next, sharpening processing was performed in order to emphasize the boundary between the crystal grains and the background in the TEM image. The sharpening process used the "edge" function with a filter size of 7x7 pixels. Furthermore, the image after the above processing was binarized by specifying a luminance range based on the luminance histogram. The lower threshold was set to 0 and the upper threshold was set to the peak top of the histogram. After setting the threshold value, some corrections were made using the pen tool for areas where the binarization process was insufficient.

TEM images of powder samples used in the process of determining the average equivalent circle diameter Ld are shown in FIGS. Figures 2-4 show TEM images of the powder samples of Examples 1-3. 5-11 show TEM images of the powder samples of Comparative Examples 1-7.

Also, the crystallite size Lc, the average particle size Lp, the Ba/Ti molar ratio of the BT nanocrystals, and the deposition amount of the organic carboxylic acid (oleic acid) on the BT nanocrystal surfaces were determined by the methods described above.

The evaluation results of the powders containing BT nanocrystals of Examples 1-3 and Comparative Examples 1-7 are shown in Table 2. Regarding the dispersibility of the powder in Table 2, ◯ indicates that the dispersibility is excellent, and x indicates that the dispersibility is low.

In Examples 1 to 3, the average equivalent circle diameter Ld and the crystallite diameter Lc were 12 nm or less, and the average particle diameter Lp was 18 nm or less. In addition, the degree of aggregation (Lp/Ld) was less than 2, and the degree of crystallinity (Lc/Ld) was 0.9 or more. As described above, in Examples 1 to 3, powders of BT nanocrystals that were fine, highly crystalline, and had excellent dispersibility were obtained. When such a powder is used as a common material for an MLCC, it is possible to uniformly coat the fine electrode material, which is advantageous for downsizing and improving the reliability of the MLCC. Moreover, when such a powder is added to a resin, a film having high transparency and excellent refractive index and dielectric constant can be obtained.

In all of Comparative Examples 1 to 7, the average particle size Lp was very large, the degree of aggregation greatly exceeded 2, and powders with low dispersibility were obtained. In Comparative Example 1 using TALH as the titanium source, the average equivalent circle diameter Ld and the crystallite diameter Lc were comparable to those in Example 3, but the coefficient of variation of the equivalent circle diameter exceeded 20%, and the crystal size A powder with a large variation in . Also, the average particle size Lp was as large as 234.9 nm, and the dispersibility of the powder was low.

In Comparative Examples 2 and 6, BT particles with a crystallinity of less than 0.9 and low crystallinity were obtained. This is because the molar ratio of (hydroxide ion/Ba ion) is less than 3.4 in Comparative Example 2, and the molar ratio of (oleic acid/Ba ion) is greater than 2 in Comparative Example 6. This is thought to be due to the deterioration of the

In Comparative Examples 4 and 5, the degree of crystallinity exceeded 0.9, and the average equivalent circle diameter Ld was about the same as in Comparative Example 1, but the coefficient of variation of the equivalent circle diameter was further increased. This is because the molar ratio of (hydroxide ion/Ba ion) exceeds 6 in Comparative Example 4, and the molar ratio of (oleic acid/Ba ion) in Comparative Example 5 is less than 0.5. This is thought to be due to the formation of coarse crystal grains with high toughness.

In Comparative Example 3, both the average equivalent circle diameter Ld and the crystallite diameter Lc exceeded 30 nm. Moreover, since the Ba/Ti molar ratio of the crystal is much lower than 0.95, it is considered that the crystal contains compounds other than barium titanate.

In Comparative Example 3, the (hydroxide ion/Ba ion) molar ratio was much lower than 3.4, and the reactivity was remarkably lowered. In addition, the (oleic acid/Ba ion) molar ratio was less than 0.5, and most of the Ba ions could not contribute to the reaction with oleic acid during the hydrothermal reaction. Therefore, many unreacted Ba ions remained and were removed in the washing process. For this reason, it is considered that the Ba/Ti molar ratio of the crystal became very small.

In Comparative Example 7, the (hydroxide ion/Ba ion) molar ratio is more than 3.4 and 6.0 or less, and the (oleic acid/Ba ion) molar ratio is in the range of 0.5 or more and 2.0 or less. However, since crystalline titanium hydroxide was used as the titanium source, the average equivalent circle diameter Ld and the crystallite diameter Lc were larger than 20 nm, and the dispersibility was also lowered.

The barium titanate nanocrystals according to the present invention are useful for electronic devices such as multilayer capacitors.
While the invention has been described in terms of presently preferred embodiments, such disclosure is not to be construed in a limiting sense. Various alterations and modifications will no doubt become apparent to those skilled in the art to which the invention pertains after reading the above disclosure. Therefore, the appended claims are to be interpreted as covering all variations and modifications without departing from the true spirit and scope of the invention.

Claims (9)

A powder comprising barium titanate nanocrystals,
The average equivalent circle diameter Ld of the powder obtained using a transmission electron microscope image of the powder is 12 nm or less,
The crystallite diameter Lc of the nanocrystal obtained by Scherrer's equation using the full width at half maximum of the diffraction peak corresponding to the (111) plane of the nanocrystal in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the powder is 12 nm or less,
The surface of the nanocrystal is coated with an organic carboxylic acid,
The powder has an average particle size Lp of 18 nm or less, which is obtained by a dynamic light scattering method by dispersing the powder in a nonpolar dispersion medium.the law of nature,
The dispersion medium is toluene with a viscosity of 0.567 mPa s. A powder containing barium titanate nanocrystals. 2. The powder containing barium titanate nanocrystals according to claim 1, wherein the variation coefficient of the equivalent circle diameter of the nanocrystals measured in the process of obtaining the average equivalent circle diameter Ld is 20% or less. In the nanocrystal, the molar ratio of barium to titanium: Ba/Ti is 0.95 or more and 1.1 or less,
Powder comprising barium titanate nanocrystals according to claim 1 or 2, wherein said nanocrystals consist of a single phase of barium titanate. A powder comprising barium titanate nanocrystals according to any one of claims 1 to 3, wherein the organic carboxylic acid comprises oleic acid. The barium titanate according to any one of claims 1 to 4, wherein the powder has a coating amount of the organic carboxylic acid of 15% by mass or more and 25% by mass or less with respect to the entire powder. Powder containing nanocrystals. a preparation step of obtaining a raw material mixture containing a water-soluble compound containing barium, a compound containing titanium, an organic carboxylic acid, an alkaline component, and water;
a heating step of heating the raw material mixture to obtain barium titanate nanocrystals;
including
The compound containing titanium includes at least one selected from the group consisting of titanium tetrachloride and amorphous titanium hydroxide,
6. In the raw material mixture, the molar ratio of the organic carboxylic acid to barium ions is 0.5 or more and 2.0 or less, and the molar ratio of hydroxide ions to barium ions is more than 3.4. A method for producing a powder containing barium titanate nanocrystals that is 0 or less. 7. The method for producing a powder containing barium titanate nanocrystals according to claim 6, wherein the water-soluble compound containing barium comprises at least one selected from the group consisting of barium hydroxide and barium chloride. The method for producing a powder containing barium titanate nanocrystals according to claim 6 or 7, wherein the organic carboxylic acid contains oleic acid. The method for producing a powder containing barium titanate nanocrystals according to any one of claims 6 to 8, further comprising a washing step of dispersing and washing the nanocrystals in alcohol after the heating step.

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