JP2023071271A - Powder containing spherical barium titanate composite particles, method for producing the same, and filler for sealing material - Google Patents

Abstract

To provide a simple method for producing a barium titanate powder with a small amount of dissolved ionic impurities.SOLUTION: A method for producing a powder containing spherical barium titanate composite particles includes a step a of forming spherical barium titanate composite particles by injecting a raw material composition containing barium titanate raw material particles and metal oxide particles containing at least one kind selected from the group consisting of SiO2 and Al2O3 into a high temperature field heated above a melting start temperature of the barium titanate raw material particles and the metal oxide particles.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a powder containing spherical barium titanate composite particles, a method for producing the same, and a filler for a sealing material.

A barium titanate-based compound is known as a material having an extremely high dielectric constant, and is widely used as a filler in various electronic component materials (for example, encapsulants, etc.) that require a high dielectric constant. In recent years, barium titanate-based Particles containing a compound and powder containing the particles (hereinafter also referred to as "barium titanate powder") have attracted attention.

Although the barium titanate-based compound itself has a high relative dielectric constant, the effect of improving the relative dielectric constant as a filler varies depending on the production method of the filler (barium titanate powder). Therefore, various methods for producing barium titanate powder have been investigated.

For example, Patent Literature 1 discloses a method of producing barium titanate powder by spraying a barium titanate raw material into a high-temperature flame to melt and spheroidize the barium titanate raw material. A sealing material having a high dielectric constant can be obtained from the barium titanate powder obtained by this method.

On the other hand, when the barium titanate powder is used as a filler for a sealing material that requires long-term reliability, it is required to reduce the elution amount of ionic impurities mixed in during the manufacturing process. In contrast, Patent Document 2 discloses a method for reducing the residual amount of ionic impurities and reducing the amount of eluted impurities by subjecting barium titanate powder to ultrasonic treatment in ion-exchanged water. .

JP 2017-24925 A WO2017/217235

A main object of the present invention is to provide a barium titanate powder from which the amount of ionic impurities eluted is small, and to provide a simple method for producing barium titanate powder from which the amount of ionic impurities eluted is small. That's what it is.

The present invention provides at least the following [1] to [16].

[1] A method for producing a powder containing spherical barium titanate composite particles, wherein the barium titanate raw material particles and a metal oxide containing at least one selected from the group consisting of SiO ₂ and Al ₂ O ₃ and a raw material composition containing the barium titanate raw material particles and the metal oxide particles is injected into a high-temperature field heated to a melting start temperature or higher of the barium titanate raw material particles and the metal oxide particles, thereby producing spherical barium titanate composite particles. A method for producing powder, comprising the step a of forming

[2] The method for producing a powder according to [1], which includes the step b of firing the powder containing the barium titanate composite particles formed in the step a.

[3] Before the step b, further comprising a step c of classifying the powder containing the barium titanate composite particles formed in the step a to obtain a plurality of powders having different average particle sizes, In b, among the plurality of powders obtained in the step c, powder having an average particle diameter of 3.0 to 12.0 μm and a true specific gravity of 5.40 to 5.90 g/cm ³ is selected. The method for producing powder according to [2], wherein the method is sintered.

[4] The method for producing powder according to any one of [1] to [3], wherein the temperature of the high temperature field is 1625 to 2500°C.

[5] The method for producing powder according to any one of [1] to [4], wherein the raw material composition further contains water.

[6] The content of the barium titanate raw material particles in the raw material composition is 95.0 to 99.5% by mass based on the total solid content of the raw material composition, [1] to [5] ] The manufacturing method of the powder as described in any one of ].

[7] of [1] to [6], wherein the content of the metal oxide particles in the raw material composition is 0.5 to 5.0% by mass based on the total solid content of the raw material composition; A method for producing powder according to any one of the above.

[8] The method for producing powder according to any one of [1] to [7], wherein the average particle size of the metal oxide particles is smaller than the average particle size of the barium titanate raw material particles.

[9] A powder containing spherical barium titanate composite particles, wherein the barium titanate composite particles are a barium titanate compound and at least one metal element selected from the group consisting of Si and Al. as a constituent element, and a plurality of island-shaped regions and a sea-shaped region surrounding the island-shaped regions are present in the cross section of the barium titanate composite particles, and the island-shaped regions are composed of A powder containing Ba, Ti and O as constituent elements, wherein the sea region contains at least one metal element selected from the group consisting of Si and Al as constituent elements.

[10] The content of the barium titanate-based compound having a tetragonal crystal structure, determined by Rietveld analysis of the powder X-ray diffraction pattern, is 75.0 to 99.9 mass%, the powder according to [9]. body.

[11] The powder according to [9] or [10], wherein the barium titanate composite particles contain Ba ₂ TiSi ₂ O ₈ .

[12] The powder according to [11], which has a Ba ₂ TiSi ₂ O ₈ content of 0.1 to 25.0% by mass, as determined by Rietveld analysis of a powder X-ray diffraction pattern.

[13] The powder according to any one of [9] to [12], which has an average particle size of 3.0 to 12.0 μm.

[14] The powder according to any one of [9] to [13], which has an average sphericity of 0.80 or more.

[15] 30 g of the powder, 142.5 mL of ion-exchanged water with an electrical conductivity of 1 μS/cm or less, and 7.5 mL of ethanol with a purity of 99.5% or more are mixed, shaken for 10 minutes, and then shaken for 30 minutes. The powder according to any one of [9] to [14], wherein the extracted water has an electric conductivity of 600 μS/cm or less when the extracted water is prepared by standing still for a minute.

[16] A filler for a sealing material, containing the powder according to any one of [9] to [15].

According to the present invention, it is possible to provide a barium titanate powder from which the elution amount of ionic impurities is small. Further, according to the present invention, it is possible to provide a simple method for producing barium titanate powder with a small elution amount of ionic impurities.

FIG. 1 is a schematic cross-sectional view of barium titanate composite particles. 2 is an SEM image showing a cross section of the barium titanate composite particles of Example 4. FIG. 3 is an SEM image showing a cross section of barium titanate composite particles of Example 8. FIG.

In this specification, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or lower limit value of the numerical range at one step may be replaced with the upper limit value or lower limit value of the numerical range at another step. Moreover, in the numerical ranges described in this specification, the upper and lower limits of the numerical ranges may be replaced with the values shown in Experimental Examples. Moreover, the upper limit value and the lower limit value described individually can be combined arbitrarily.

Preferred embodiments of the present invention are described below. However, the present invention is by no means limited to the following embodiments.

<Barium titanate powder>
The barium titanate powder of one embodiment is powder containing spherical barium titanate composite particles. In the present specification, the term "spherical" is not limited to true spheres, and refers to those having an average sphericity of 0.80 or more as measured by the method described later.

The barium titanate-based composite particles are compounds containing, as constituent elements, a barium titanate-based compound and at least one metal element selected from the group consisting of Si and Al (hereinafter also referred to as "Si/Al-based compound"). and

FIG. 1 is a schematic cross-sectional view of barium titanate composite particles. As shown in the figure, the cross section of the barium titanate composite particles 1 includes a plurality of island-like regions 2 and a sea-like region 3 surrounding the island-like regions 2 . The island region 2 is a region containing Ba, Ti and O as constituent elements, for example, a region containing a barium titanate-based compound. The sea region 3 is a region containing at least one metal element selected from the group consisting of Si and Al as constituent elements, for example, a region containing a Si/Al compound. The island regions 2 and the sea regions 3 can be observed using a SEM (Scanning Electron Microscope).

The barium titanate powder having the above characteristics has a property that ionic impurities are hardly eluted. Therefore, when the barium titanate powder is used as a filler for a sealing material, it is expected that the occurrence of defects caused by ionic impurities will be suppressed and the long-term reliability of the sealing material will be improved. be. The reason for this is presumed as follows.

Ionic impurities mixed in during the production of barium titanate powder are, for example, impurities derived from barium titanate compounds such as BaCO ₃ , and phases containing Ba, Ti and O (for example, barium titanate compounds containing phase). On the other hand, in the barium titanate powder, the phases containing Ba, Ti and O (island regions in cross-sectional observation) are surrounded by the phases containing Si and/or Al (sea regions in cross-sectional observation). Therefore, the elution of ionic impurities from the phase containing Ba, Ti and O is hindered by the phase containing Si and/or Al, and as a result, the elution of ionic impurities from the barium titanate powder is inhibited. It is presumed that this is becoming less likely to occur.

(barium titanate compound)
A barium titanate-based compound is a perovskite-type oxide containing Ti and Ba as constituent elements. Generally, perovskite-type oxides such as barium titanate have the crystal structure of _ABO3 . Both the A site and the B site are easily substituted with other elements, and different elements such as Nd, La, Ca, Sr, and Zr can be substituted into the crystal structure. In the present specification, besides barium titanate, compounds obtained by substituting a dissimilar element at the above-mentioned A site and/or B site of barium titanate are collectively referred to as barium titanate compounds. Examples of the barium titanate-based compound include compounds represented by the following formula (1) and compounds represented by the following formula (2).
(Ba _(1-x) Ca _x ) (Ti _(1-y) Zr _y ) O ₃ (1)
[In formula (1), x and y satisfy 0≦x+y≦0.4. ]
La _x Ba _(1-x) Ti _(1-x/4) O ₃ (2)
[In formula (2), x satisfies 0<x<0.14. ]

The barium titanate-based compound may have a tetragonal crystal structure. In other words, the barium titanate-based composite particles may contain a barium titanate-based compound having a tetragonal crystal structure.

The content of the barium titanate-based compound having a tetragonal structure can be determined by Rietveld analysis of a powder X-ray diffraction (XRD: X-ray Diffraction) pattern. The content of the barium titanate-based compound having a tetragonal crystal structure determined by Rietveld analysis of the powder X-ray diffraction pattern may be 75.0% by mass or more from the viewpoint of improving the dielectric constant. It may be 0% by mass or more, 85.0% by mass or more, 90.0% by mass or more, 93.0% by mass or more, or 95.0% by mass or more. The content of the barium titanate-based compound having a tetragonal structure, determined by Rietveld analysis of the powder X-ray diffraction pattern, is 99.9% from the viewpoint of enhancing the effect of suppressing the elution of ionic impurities by the Si/Al-based compound. It may be 9% by mass or less, 99.7% by mass or less, or 99.5% by mass or less. From these viewpoints, the content is 75.0 to 99.9% by mass, 80.0 to 99.9% by mass, 85.0 to 99.9% by mass, 90.0 to 99.9% by mass, It may be from 93.0 to 99.7% by weight or from 95.0 to 99.5% by weight. The measurement of the powder X-ray diffraction pattern and the Rietveld analysis can be performed using D8 advance (manufactured by BRUKER, detector: LynxEye). This technique quantifies the crystalline phases in a powder sample. Therefore, the above content is the content in the barium titanate powder based on the total amount of crystal phase.

The barium titanate-based composite particles may contain a barium titanate-based compound having a crystal structure other than a tetragonal structure (for example, a hexagonal structure). However, the content of the barium titanate-based compound having a crystal structure other than the tetragonal structure, which is obtained by Rietveld analysis of the powder X-ray diffraction pattern, is preferably 2.0 mass from the viewpoint of improving the dielectric constant. % or less.

Although the barium titanate-based compound may be contained in regions other than the island-shaped regions 2, it is preferably contained mainly in the island-shaped regions 2. That is, it is preferable that the majority of the total mass of the barium titanate-based compound contained in the barium titanate-based composite particles is contained in the island-shaped regions. Therefore, in one example, the island-shaped region can also be said to be a region containing the majority of the total mass of the barium titanate-based compound contained in the barium titanate-based composite particles.

The content of the barium titanate-based compound in the barium titanate composite particles and the barium titanate powder may be 90.0 to 99.9% by mass, and 93.0 to 99.7% by mass. % or 95.0 to 99.5% by mass. The above content is based on the total mass of the barium titanate composite particles or barium titanate powder.

(Si/Al compound)
A Si/Al-based compound is, for example, an oxide containing Si and/or Al. The Si/Al-based compound may further contain Ti and/or Ba as constituent elements. Examples of Si/Al-based compounds include fresnoite-type oxides represented by Ba ₂ TiSi ₂ O ₈ , AlTiO ₃ , SiO ₂ , Al ₂ O ₃ and the like. When the barium titanate composite particles contain Ba ₂ TiSi ₂ O ₈ , the effect of suppressing elution of ionic impurities tends to increase.

The content of Ba ₂ TiSi ₂ O ₈ can be determined by Rietveld analysis of the powder X-ray diffraction pattern. The content of Ba ₂ TiSi ₂ O ₈ , which is determined by Rietveld analysis of the powder X-ray diffraction pattern, may be 0.1% by mass or more from the viewpoint of making it easier to suppress the elution of ionic impurities. .3% by mass or more, or 0.5% by mass or more. The content of Ba ₂ TiSi ₂ O ₈ determined by Rietveld analysis of the powder X-ray diffraction pattern may be 25.0% by mass or less, and 20.0% by mass or less, from the viewpoint of improving the dielectric constant. , 15.0% by mass or less, 10.0% by mass or less, 7.0% by mass or less, or 5.0% by mass or less. From these viewpoints, the content is 0.1 to 25.0% by mass, 0.1 to 20.0% by mass, 0.1 to 15.0% by mass, 0.1 to 10.0% by mass, It may be from 0.3 to 7.0% by weight or from 0.5 to 5.0% by weight.

Although the Si/Al-based compound may be contained in a region other than the sea-like region 3, it is preferably contained mainly in the sea-like region 3. That is, it is preferable that the ocean-like region 3 contains the majority of the total mass of the Si/Al-based compound contained in the barium titanate-based composite particles. Therefore, in one example, the sea-like region can also be said to be a region containing the majority of the total mass of the Si/Al-based compound contained in the barium titanate-based composite particles.

The content of the Si/Al compound in the barium titanate composite particles and the barium titanate powder may be 0.1 to 25.0% by mass, and may be 0.1 to 20.0% by mass. %, 0.1-15.0% by weight, 0.1-10.0% by weight, 0.3-7.0% by weight or 0.5-5.0% by weight. The above content is based on the total mass of the barium titanate composite particles or barium titanate powder.

The barium titanate-based composite particles may contain components (such as impurities) other than the barium titanate-based compound and the Si/Al-based compound. However, it is preferable that the barium titanate-based composite particles mainly contain a barium titanate-based compound and a Si/Al-based compound. That is, the total content of the barium titanate-based compound and the Si/Al-based compound in the barium titanate-based composite particles preferably accounts for the majority of the total mass of the barium titanate-based composite particles. The total content of the barium titanate-based compound and the Si/Al-based compound may be 98-100% by mass or 99-100% by mass based on the total mass of the barium titanate-based composite particles.

Similarly, the barium titanate powder may contain components (such as impurities) other than the barium titanate composite particles. However, the barium titanate powder preferably contains mainly barium titanate composite particles. That is, the content of the barium titanate composite particles in the barium titanate powder preferably accounts for the majority of the total mass of the barium titanate powder. The content of the barium titanate composite particles in the barium titanate powder may be 98 to 100% by mass, preferably 99 to 100% by mass, based on the total mass of the barium titanate powder. good too.

(Cross-sectional structure of composite particles)
The island-shaped region 2 may be composed only of the barium titanate-based compound, or may contain a component other than the barium titanate-based compound. However, when the island region 2 is analyzed by energy dispersive X-ray spectroscopy (EDS), it preferably does not contain Si and/or Al. From the viewpoint of obtaining a higher dielectric constant, it is preferable that the island regions 2 are mainly composed of a barium titanate-based compound. That is, it is preferable that more than half of the total area of the island-shaped region 2 is composed of the barium titanate-based compound.

The barium titanate-based compound contained in the island regions 2 may form a crystal phase (eg, a tetragonal phase). The island regions 2 may consist of only a crystalline phase, or may contain an amorphous phase. From the viewpoint of obtaining a higher dielectric constant, it is preferable that the island regions 2 are mainly composed of a crystalline phase. That is, it is preferable that the majority of the total area of the island-shaped region 2 is composed of the crystalline phase.

The area ratio of the island-shaped regions 2 to the cross section of the barium titanate composite particles is 70 to 98 area % from the viewpoint of achieving both the improvement of the dielectric constant and the reduction of the elution amount of ionic impurities. 80-96 area % or 90-95 area %. The area ratio of the island-shaped regions 2 can be obtained, for example, by importing a cross-sectional SEM image into the image analysis software "ImagePRO", manually selecting the island-shaped regions 2, and determining the area of the island-shaped regions 2 and the area of the entire particle. can be calculated.

The sea region 3 may be composed only of the Si/Al-based compound, or may contain components other than the Si/Al-based compound. From the viewpoint of further reducing the elution amount of ionic impurities, it is preferable that the sea-like region 3 is mainly composed of a Si/Al-based compound. That is, it is preferable that the majority of the total area of the sea region 3 is composed of the Si/Al-based compound.

The Si/Al-based compound contained in the sea region 3 may constitute a crystal phase (for example, fresnoite phase). The sea region 3 may consist of only a crystalline phase, or may contain an amorphous phase. From the viewpoint of further reducing the amount of elution of ionic impurities, the sea-like region 3 is preferably mainly composed of a crystalline phase. That is, it is preferable that the majority of the total area of the sea region 3 is composed of the crystal phase.

The area ratio of the sea region 3 in the cross section of the barium titanate composite particles is 12 to 30 area % from the viewpoint of achieving both the improvement of the dielectric constant and the reduction of the elution amount of ionic impurities. may be from 14 to 20 area % or from 5 to 10 area %. The area ratio of the sea-like region 3 can be obtained, for example, by importing the cross-sectional SEM image into the image analysis software "ImagePRO", manually selecting the sea-like region 3, and determining the area of the sea-like region 3 and the area of the entire particle. can be calculated.

(Powder physical properties)
The extracted water electrical conductivity of the barium titanate powder is, for example, 600 μS/cm or less, 500 μS/cm or less, 400 μS/cm or less, 300 μS/cm or less, 200 μS/cm or less, 100 μS/cm or less, or 70 μS/cm or less. cm or less. Here, the electrical conductivity of the extraction water of the barium titanate powder is as follows: 30 g of barium titanate powder, 142.5 mL of ion-exchanged water with electrical conductivity of 1 μS/cm or less, and purity of 99.5% or more. It means the electrical conductivity of the sample liquid (extracted water) prepared by mixing with 7.5 mL of ethanol, shaking for 10 minutes, and then standing still for 30 minutes. Low conductivity means that the amount of ionic impurities contained in the barium titanate powder is small. Therefore, the lower the electrical conductivity of the extracted water of the barium titanate powder, the better. The electric conductivity of the extracted water was obtained by immersing the electric conductivity cell in the sample solution after standing still and reading it after 1 minute. , is the value read after 1 minute. The measurement of the electrical conductivity can be carried out using an electrical conductivity meter "CM-30R" and an electrical conductivity cell "CT-57101C" manufactured by DKK Toa Co., Ltd. In addition, shaking in the above extraction operation can be performed using “Double Action Lab Shaker SRR-2” manufactured by AS ONE Corporation. In addition, in the present embodiment, the extracted water electrical conductivity of the barium titanate composite particles may be within the above range.

The average particle size of the barium titanate powder may be set according to the application. The average particle size of the barium titanate powder is 3.0 to 12.0 μm from the viewpoint of being suitably used for various electronic component materials, particularly fillers for sealing materials that require a high dielectric constant. good. The average particle size of the barium titanate powder may be, for example, 3.0 to 5.0 μm, 6.0 to 8.0 μm, or 9.0 to 12.0 μm. good. The average particle size of the barium titanate powder may be 3.2 μm or more or 3.5 μm or more, or may be 6.5 μm or less or 6.0 μm or less. The average particle size of the barium titanate powder may be 9.5 μm or more or 10.0 μm or more, or may be 11.8 μm or less or 11.5 μm or less. Here, the average particle size means the particle size (D50) at which the cumulative mass becomes 50% in the particle size distribution obtained by the mass-based particle size measurement by the laser diffraction light scattering method. The average particle size can be measured using Malvern's "Mastersizer 3000, wet dispersion unit: equipped with Hydro MV". In addition, in the present embodiment, the average particle size of the barium titanate composite particles may be within the above range.

The barium titanate powder has an average sphericity of 0.80 or more, 0.83 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more, 0.89 or more, or 0.89 or more. It may be 90 or more. The higher the average sphericity, the higher the fluidity and moldability of the encapsulating material, and the easier it is to increase the filling amount (higher filling), so the encapsulating material has a higher relative dielectric constant. becomes easier to obtain. The maximum value of the average sphericity is 1, and may be 0.99 or less, 0.97 or less, 0.95 or less, 0.93 or less, or 0.92 or less. The average sphericity is, for example, 0.80 to 0.99, 0.83 to 0.97, 0.85 to 0.95, 0.86 to 0.93, 0.86 to 0.92, 0.87 ~0.92, 0.88-0.92, 0.89-0.92, 0.90-0.92, etc. Here, the average sphericity means a value measured by the following method. First, the sample powder and ethanol were mixed to prepare a slurry having a sample powder concentration of 1% by mass. Disperse for 2 minutes. The dispersion slurry thus obtained is dropped onto a sample stage coated with carbon paste using a dropper. After the dropped slurry is allowed to stand still in the atmosphere until it dries on the sample table, it is coated with osmium and photographed with a scanning electron microscope "JSM-6301F type" manufactured by JEOL Ltd. Photographing is performed at a magnification of 3000 times to obtain an image with a resolution of 2048×1536 pixels. Capture the obtained image to a personal computer, use an image analysis device "MacView Ver. PM) to measure sphericity. If the area of the perfect circle corresponding to the perimeter (PM) is (B), then the sphericity of the particle is A/B. r), PM=2πr, B=πr ² , so B=π×(PM/2π) ² and the sphericity (A/B) of each particle is A×4π/(PM) ² becomes. The sphericity of 200 particles thus obtained having a projected area equivalent circle diameter of 2 μm or more is determined, and the arithmetic mean value thereof is taken as the average sphericity. In addition, in the present embodiment, the average sphericity of the barium titanate composite particles may be within the above range.

The true specific gravity of the barium titanate powder is preferably 5.30 to 6.02 g/cm ³ from the viewpoint of obtaining a higher dielectric constant. 5. The true specific gravity of the barium titanate powder may be 5.35 g/cm ³ or more, 5.40 g/cm ³ or more, or 5.42 g/cm ³ or more, and 6.00 g/cm ³ or less. It may be 95 g/cm ³ or less or 5.90 g/cm ³ or less. The true specific gravity can be measured by Auto True Denser MAT-7000 manufactured by Seishin Enterprise Co., Ltd. In addition, in the present embodiment, the true specific gravity of the barium titanate composite particles may be within the above range.

By the way, in the method of spraying barium titanate-based raw material particles into a high-temperature flame, a space (hollow portion) is likely to be formed inside the obtained barium titanate-based particles. Therefore, the barium titanate particles tend to have many hollow portions and tend to have a high BET specific surface area. On the other hand, in the barium titanate composite particles contained in the barium titanate powder of the present embodiment, a region containing a Si/Al-based compound exists around a region containing a barium titanate-based compound. It tends to have a relatively small BET specific surface area because it has a structure with less

The barium titanate powder described above can be used for various electronic component materials, and is particularly suitable as a filler for encapsulants that require a high dielectric constant. In other words, another embodiment of the present invention is a filler for electronic component materials (preferably for sealing materials) containing the barium titanate powder. Examples of the sealing material include sealing materials used for antenna-in-package. When barium titanate powder is used as a filler for a sealing material, it can be used by mixing with other filler components.

<Method for producing barium titanate powder>
A production method of one embodiment is a method for producing powder (barium titanate powder) containing spherical barium titanate composite particles. In this production method, a raw material composition containing barium titanate raw material particles and metal oxide particles containing at least one selected from the group consisting of SiO ₂ and Al ₂ O ₃ is prepared as a barium titanate raw material. It includes a step a of forming spherical barium titanate composite particles by injecting into a high temperature field heated to a melting start temperature or higher of the particles and metal oxide particles.

In order to reduce the amount of elution of ionic impurities in the conventional method, after forming the spherical barium titanate particles, it was necessary to perform washing operations such as washing with water and ultrasonic treatment. According to this, it is possible to obtain barium titanate powder in which the amount of eluted ionic impurities is small without performing a washing operation. Moreover, the barium titanate powder obtained by the above method tends to have a high dielectric constant as well as a small amount of ionic impurities eluted. These reasons are inferred as follows.

In the above method, metal oxide particles containing at least one selected from the group consisting of SiO ₂ and Al ₂ O ₃ are added together with the barium titanate-based raw material particles when the barium titanate-based raw material particles are molten and spheroidized. Due to the use, heat is consumed not only for melting the barium titanate-based raw material particles but also for melting the metal oxide particles. Therefore, it is presumed that, in the above method, overmelting of the barium titanate-based raw material particles is suppressed, and generation of impurities due to overmelting and decomposition of the crystalline phase into the amorphous phase are suppressed.

In addition, since the dielectric constant of the barium titanate particles themselves tends to be lowered by washing, it can be said that the fact that there is no need to wash in the method of the present embodiment also contributes to the improvement of the dielectric constant. .

In addition, the fact that SiO ₂ and Al ₂ O ₃ have melting points close to those of the barium titanate-based compound is also considered to be one of the reasons why the elution of ionic impurities is suppressed. That is, since SiO ₂ and Al ₂ O ₃ have melting points close to those of the barium titanate-based compound, the metal oxide particles start melting before the barium titanate-based raw material particles are completely melted. A crystal phase (eg, fresnoite phase) derived from metal oxide particles is formed around a crystal phase derived from barium titanate-based raw material particles (eg, tetragonal phase of barium titanate-based compound). As a result, the elution of impurities from the crystalline phase derived from the barium titanate raw material particles is prevented by the crystalline phase derived from the metal oxide particles, and the elution of ionic impurities from the barium titanate powder is suppressed. guessed.

The barium titanate composite particles formed by the above method do not necessarily have a cross section that includes the island-like region and the sea-like region. By lowering the melting start temperature of the raw material particles, the barium titanate composite particles contained in the barium titanate powder of the above embodiment can be formed. In this case, a barium titanate powder with a smaller elution amount of ionic impurities can be obtained. The method for lowering the melting start temperature of the metal oxide particles is not particularly limited. A method of making the specific surface area smaller than the BET specific surface area of the barium titanate-based raw material particles, and the like can be mentioned.

The method may further include a step b of firing the powder containing the barium titanate composite particles formed in the step a. By performing the step b, the dielectric constant tends to be further improved, and the elution amount of ionic impurities tends to be further reduced.

The method may further include a step c of classifying the powder containing the barium titanate composite particles formed in the step a to obtain a plurality of powders having different average particle sizes. This step c may be performed after step a, or may be performed simultaneously with step a. If the method further comprises step b and step c, step c may be performed before step b. In this case, in step b, one of the plurality of powders obtained in step c is used as the powder containing the barium titanate composite particles formed in step a, and the powder is fired. The powder used in step b preferably has an average particle size of 3.0 to 12.0 μm and a true specific gravity of 5.40 to 5.90 g/cm ³ .

Each step (step a, step b, and step c) in the method for producing barium titanate powder will be described below.

(Step a: Melting spheroidization)
In step a, by injecting the raw material composition into a high temperature field, the components (barium titanate raw material particles, metal oxide particles, etc.) in the raw material composition are melted and solidified to form spherical barium titanate composite particles. to form

The barium titanate-based raw material particles are particles containing a barium titanate-based compound. The barium titanate-based raw material particles may contain components other than the barium titanate-based compound (for example, components such as impurities that are unavoidably contained). However, the barium titanate-based raw material particles preferably contain a barium titanate-based compound as a main component (for example, as a component with the highest mass fraction). The content of the barium titanate-based compound in the barium titanate raw material particles may be 98 to 100% by mass, or even 99 to 100% by mass, based on the total mass of the barium titanate raw material particles. good.

The shape of the barium titanate-based raw material particles is not particularly limited, and may be fixed or irregular.

The barium titanate raw material particles may have an average particle size of 0.5 to 3.0 μm, 1.0 to 2.5 μm, or 1.5 to 2.0 μm. The larger the average particle size of the barium titanate raw material particles, the larger the average particle size of the barium titanate composite particles obtained in step a. The average particle size of the barium titanate composite particles obtained is reduced. When the average particle diameter of the barium titanate raw material particles is within the above range, barium titanate composite particles having an average particle diameter of 3.0 to 12.0 μm are easily obtained in step a.

The BET specific surface area of the barium titanate raw material particles may be 1.0 to 3.0 m ² /g, 1.5 to 2.8 m ² /g or 1.8 to 2.5 m ² /g. may

The content of the barium titanate raw material particles in the raw material composition is such that a cross section having the above-described sea-island structure is likely to be formed, and titanium that achieves both an improvement in the relative dielectric constant and a reduction in the amount of elution of ionic impurities to a higher degree. From the viewpoint of facilitating the production of barium acid composite particles, it is preferably 95.0% by mass or more, 97.0% by mass or more, or 98.0% by mass or more based on the total solid content of the raw material composition. may From the same point of view, the content of the barium titanate raw material particles in the raw material composition is preferably 99.5% by mass or less, preferably 99.3% by mass or less, or 99.3% by mass or less, based on the total solid content of the raw material composition. 0% by mass or less. From these viewpoints, the content of the barium titanate raw material particles in the raw material composition is preferably 95.0 to 99.5% by mass, based on the total solid content of the raw material composition, and preferably 97.0 to 99% by mass. .3% by weight or 98.0 to 99.0% by weight.

Metal oxide particles are particles containing at least one selected from the group consisting of SiO ₂ and Al ₂ O ₃ . The metal oxide particles may contain components other than SiO ₂ and Al ₂ O ₃ (for example, components such as impurities that are unavoidably contained). However, the metal oxide particles preferably contain SiO ₂ and/or Al ₂ O ₃ as main components (for example, as components with the highest mass fraction). The content of SiO ₂ in the metal oxide particles may be 98 to 100% by mass, or may be 99 to 100% by mass, based on the total mass of the raw material particles. Similarly, the content of Al ₂ O ₃ in the metal oxide particles may be 98 to 100 mass %, or may be 99 to 100 mass %, based on the total mass of the raw material particles.

The shape of the metal oxide particles is not particularly limited, and may be fixed or amorphous. The average particle size of the metal oxide particles is preferably smaller than the average particle size of the barium titanate-based raw material particles. In this case, the melting start temperature of the metal oxide particles tends to be lower than the melting start temperature of the barium titanate raw material particles, and the cross section having the sea-island structure described above is likely to be formed. From the same point of view, the BET specific surface area of the metal oxide particles is preferably larger than the BET specific surface area of the barium titanate raw material particles.

The average particle size of the metal oxide particles may be 0.01-1.50 μm, 0.03-1.30 μm or 0.05-1.10 μm.

The BET specific surface area of the metal oxide particles may be 5-50 m ² /g, 20-40 m ² /g or 25-35 m ² /g.

The content of the metal oxide particles in the raw material composition is such that the cross section having the above-described sea-island structure is likely to be formed, and barium titanate achieves a higher degree of compatibility between an improvement in the dielectric constant and a reduction in the amount of elution of ionic impurities. From the viewpoint of easily obtaining quality composite particles, it is preferably 0.5% by mass or more, and even if it is 0.7% by mass or more or 1.0% by mass or more, based on the total solid content of the raw material composition. good. From the same point of view, the content of the metal oxide particles in the raw material composition is preferably 5.0% by mass or less, and 3.0% by mass or less or 2.0% by mass, based on the total solid content of the raw material composition. % by mass or less. From these viewpoints, the content of the metal oxide particles in the raw material composition is preferably 0.5 to 5.0% by mass, based on the total solid content of the raw material composition, and 0.7 to 3.0 % by mass or 1.0 to 2.0% by mass.

The ratio of the content of the barium titanate raw material particles to the content of the metal oxide particles (barium titanate raw material particles: metal oxide particles) facilitates the formation of a cross section having the above-described sea-island structure, and the relative dielectric constant From the viewpoint of making it easier to obtain barium titanate composite particles that achieve both an improvement in the ionic impurities and a reduction in the eluted amount of ionic impurities, the mass ratio is 99.5:0.5 to 95.0:5. 0, 99.3:0.7 to 97.0:3.0 or 99.0:1.0 to 98.0:2.0.

The raw material composition may further contain water. In this case, the raw material composition may be in the form of slurry. In step a, when a raw material composition containing water (for example, a slurry raw material composition) is sprayed into a high-temperature field, the surface tension of water facilitates improving the sphericity of the barium titanate-based composite particles.

In addition to water, the raw material composition may further contain an organic solvent such as methanol or ethanol for the purpose of adjusting the calorific value. These may be used alone or in combination.

When the raw material composition contains a liquid medium such as water or an organic solvent, the concentration (content) of the solid content is adjusted to facilitate increasing the sphericity of the barium titanate composite particles. It may be 1 to 50% by weight, 20 to 47% by weight, or 40 to 45% by weight, based on the total weight.

The hot field may be, for example, a hot flame formed in a combustion furnace or the like. A high temperature flame can be formed by combustible gas and supporting gas. The temperature of the high-temperature field (for example, high-temperature flame) is a temperature equal to or higher than the melting start temperature of the barium titanate-based raw material particles and the metal oxide particles, for example, 1625° C. or higher. The high temperature field may be 1625-2500°C, 1625-2200°C, 1625-2000°C, and the like.

As the combustible gas, for example, one or more of propane, butane, propylene, acetylene, hydrogen and the like can be used. As the auxiliary combustion gas, for example, an oxygen-containing gas such as oxygen gas can be used. However, the combustible gas and the combustion support gas are not limited to these.

Injection (spraying) of the raw material composition can be performed using, for example, a two-fluid nozzle. The injection speed (supply speed) of the raw material composition may be 0.3 to 32 kg/h, 9 to 29 kg/h or 22 to 27 kg/h. When the injection speed of the raw material composition is within the above range, the sphericity of the barium titanate composite particles is likely to be improved. When a slurry-like raw material composition is used, the injection speed of the barium titanate-based raw material particles and the injection speed of the metal oxide particles in the raw material composition may be within the above ranges.

A dispersing gas may be used when injecting the raw material composition. That is, the raw material composition may be injected while being dispersed in the dispersion gas. This makes it easier to improve the sphericity of the barium titanate composite particles. Combustion-supporting gases such as air and oxygen, inert gases such as nitrogen and argon, etc., can be used as dispersion gases, and combustible gases can also be mixed and used for the purpose of adjusting the calorific value of the gas. can. The supply rate of the dispersion gas may be 20 to 50 m ³ /h, 30 to 47 m ³ /h, or 40 to 45 m ³ /h from the viewpoint of facilitating an increase in the sphericity of the barium titanate composite particles. may be

In the above step a, a powder substantially composed of barium titanate composite particles can be obtained. The resulting powder contains, for example, 98 to 100% by mass or 99 to 100% by mass of barium titanate composite particles.

The sphericity of the barium titanate composite particles formed in the step a (average sphericity of the powder containing the barium titanate composite particles) is, for example, more than 0.70. In the above step a, the sphericity of the barium titanate composite particles (the average sphericity of the powder containing the barium titanate composite particles ) can be 0.80 or more or 0.85 or more. Moreover, when carrying out the process c mentioned later, it is possible to further increase the sphericity by classification. The maximum value of the sphericity of the barium titanate composite particles (the average sphericity of the powder containing the barium titanate composite particles) is 1.

(Step c: classification)
In step c, the powder containing barium titanate composite particles formed in step a is classified. The classification method is not particularly limited, and may be screen classification or wind classification. From the viewpoint of efficient classification, a collection system line is directly connected to the lower part of the combustion furnace where step a is performed, and collection is performed by a blower installed behind the collection system line (opposite side to the combustion furnace). A preferred method is to suck the barium titanate composite particles in the combustion furnace through a system line. The collection system line may have a cyclone and bag filter as well as a heat exchanger connected to the combustion furnace. The heat exchanger, cyclone and bag filter may be connected in series in that order. In this case, the powder containing the barium titanate composite particles is collected in each of the combustion furnace, heat exchanger, cyclone and bag filter. The particle diameter of each powder to be collected can be adjusted by, for example, the suction amount of the blower.

When the above collection system line is used in step c, the powder collected on the upstream side (closer to the combustion furnace) tends to have a true specific gravity closer to the specific gravity of the barium titanate-based compound. In the collection system line, the true specific gravity of the powder collected by the heat exchanger and the true specific gravity of the powder collected by the cyclone are the closest to the specific gravity of the barium titanate compound, for example, 5 .40 to 5.90 g/cm ³ . The true specific gravity of this powder can also be 5.40-5.80 g/cm ³ , 5.45-5.78 g/cm ³ or 5.50-5.75 g/cm ³ . It is speculated that the reason why such a true specific gravity is obtained is that impurities (such as barium carbonate) having a small specific gravity are more likely to be mixed with the powder that is collected on the downstream side (closer to the blower). The closer the true specific gravity of the powder is to the specific gravity of the barium titanate-based compound, the easier it is to obtain the effect of improving the dielectric constant by firing in step b described later. When the above collection system line is used in step c, the sphericity of the powder collected by the cyclone tends to be the highest.

In step c, classification may be carried out so that at least one of the obtained powders (powder containing barium titanate composite particles) has an average particle size of 5.0 μm or less. By using the powder having the above average particle size in the step b, it becomes easier to obtain the effect of improving the dielectric constant by sintering. A powder having such an average particle size can be collected by a cyclone. The average particle size of the powder collected by the cyclone is, for example, 3.0-5.0 μm, and may be 3.2-4.8 μm or 3.5-4.5 μm.

In step c, classification may be carried out so that at least one of the obtained powders (powder containing barium titanate composite particles) has an average particle size of 9.0 to 12.0 μm. A powder having such an average particle size can be collected by a heat exchanger. The average particle size of the powder collected by the heat exchanger can also be 9.5-11.8 μm or 10.0-11.5 μm.

(Step b: Firing)
Step b is a step of firing the powder containing the barium titanate composite particles formed in step a.

As the powder containing the barium titanate composite particles formed in step a, one of a plurality of powders obtained by classifying the powder containing the barium titanate composite particles formed in step a. You can use one. That is, in step b, one of the powders obtained in step c may be used. In the case of using the collection system line in step c, the use of the powder collected by the cyclone tends to improve the dielectric constant of the barium titanate powder. From the viewpoint of obtaining barium titanate powder of higher purity that does not contain other powders such as barium carbonate as much as possible, it is preferable to use powder that is collected by a heat exchanger.

The average particle size of the powder used in the step b may be 5.0 μm or less, 4.8 μm or less, or 4.5 μm or less from the viewpoint of easily improving the dielectric constant of the barium titanate powder. There may be. The average particle size of the powder used in step b may be 3.0 μm or more, 3.2 μm or more, or 3.5 μm or more from the viewpoint of preventing aggregation and coalescence of particles during firing. good too. From these points of view, the powder used in step b may have an average particle size of 3.0 to 5.0 μm, 3.2 to 4.8 μm or 3.5 to 4.5 μm.

The average particle size of the powder used in step b may be 9.0 to 12.0 μm from the viewpoint of facilitating the production of barium titanate powder of higher purity. From the same point of view, the average particle size of the powder used in step b may be 9.5 μm or more or 10.0 μm or more, and may be 11.8 μm or less or 11.5 μm or less. It may be 5-11.8 μm or 10.0-11.5 μm.

The true specific gravity of the powder used in the step b may be 5.40 to 5.90 g/cm ³ from the viewpoint of easily improving the dielectric constant of the obtained barium titanate powder, and may be 5.40. It may be ~5.80 g/cm ³ , 5.45-5.78 g/cm ³ or 5.50-5.75 g/cm ³ .

From the above viewpoint, in one preferred embodiment, the powder containing barium titanate composite particles used in step b has an average particle diameter of 3.0 to 5.0 μm and a true specific gravity of 5.40 to 5.0 μm. It is a powder of 90 g/cm ³ . When using the collection system line in step c, powder having such an average particle size and true specific gravity can be easily obtained by collection with a cyclone (cyclone collection).

From the above viewpoint, in one preferred embodiment, the powder containing the barium titanate composite particles used in the step b has an average particle size of 9.0 to 12.0 μm and a true specific gravity of 5.40 to 5.0 μm. It is a powder of 90 g/cm ³ . When using the collection system line in step c, a powder having such an average particle size and true specific gravity can be easily obtained by collection with a heat exchanger (heat exchanger collection).

The average sphericity of the powder used in step b may be 0.80 or higher, 0.82 or higher, or 0.85 or higher. The maximum average sphericity is 1.

A firing furnace may be used for firing (heating) the powder. The firing temperature of the powder (for example, the temperature in the firing furnace) is, for example, 700° C. or higher, and may be 800° C. or higher, 900° C. or higher, 1000° C. or higher, or 1100° C. or higher. The firing temperature of the powder is, for example, 1300° C. or lower, and may be 1200° C. or lower, 1100° C. or lower, or 1000° C. or lower from the viewpoint of improving the sphericity. The firing temperature of the powder may be 800 to 1200° C. or 900 to 1100° C. from the viewpoint that the dielectric constant of the barium titanate powder is easily improved. The heating rate is not particularly limited, but may be 2 to 5°C/min, 2.5 to 4.5°C/min, or 3 to 4°C/min.

The firing time of the powder may be 2 hours or longer, 4 hours or longer, or 6 hours or longer, from the viewpoint that the dielectric constant of the barium titanate powder is easily improved. If the firing time of the powder is 6 hours or longer, the improvement of the relative permittivity decreases. Therefore, from the viewpoint of production efficiency, the firing time of the powder may be 8 hours or shorter. The firing time does not include the heating time.

Cooling conditions after firing are not particularly limited. Cooling after firing may be natural cooling in the furnace.

According to the method for producing barium titanate powder described above, it is possible to obtain barium titanate powder having a higher purity and a higher dielectric constant.

Specifically, the extracted water electrical conductivity of the barium titanate powder produced by the above method is, for example, 600 μS/cm or less. The extracted water electrical conductivity of the barium titanate powder can be further reduced by changing the type (shape, etc.) of the metal oxide particles, adjusting the amount of the metal oxide particles, and performing classification and firing. It can also be 500 μS/cm or less, 400 μS/cm or less, 300 μS/cm or less, 200 μS/cm or less, 100 μS/cm or less, or 70 μS/cm or less.

The barium titanate powder obtained by the above method tends to have a high degree of sphericity. The average sphericity of the barium titanate powder obtained by the above method is, for example, 0.80 or more, 0.83 or more, 0.85 or more, 0.86 or more, 0.87 or more, 0.88 or more. , 0.89 or more, or 0.90 or more. The maximum value of the average sphericity is 1, but in the above method, the average sphericity is close to 1 (for example, 0.80 to 0.99, 0.83 to 0.97, 0.85 to 0.95, 0.86 to 0.93, 0.86 to 0.92, 0.87 to 0.92, 0.88 to 0.92, 0.89 to 0.92, 0.90 to 0.92, etc. ) Barium titanate powder is obtained.

The barium titanate powder obtained by the above method tends to have a true specific gravity close to the specific gravity of the barium titanate compound. The true specific gravity of the barium titanate powder obtained by the above method is, for example, 5.64 to 5.91 g/cm ³ , 5.66 to 5.89 g/cm ³ , 5.68 to 5.87 g/cm 3 . It can also be cm ³ or 5.70-5.85 g/cm ³ .

The average particle size of the barium titanate powder obtained by the above method is, for example, 3.0 to 12.0 μm. In step b, among the plurality of powders obtained in step c, when powder having an average particle size of 3.0 to 5.0 μm (for example, powder collected by a cyclone) is used, the average particle size A barium titanate powder having a diameter of 3.0 to 5.0 μm can be obtained. Further, in step b, among the plurality of powders obtained in step c, when powder having an average particle size of 9.0 to 12.0 μm (for example, powder collected by a heat exchanger) is used , a barium titanate powder having an average particle size of 9.0 to 12.0 μm can be obtained. The barium titanate powder may have an average particle size of 3.2 μm or more or 3.5 μm or more, or 6.5 μm or less or 6.0 μm or less. Moreover, the average particle size of the barium titanate powder can be 9.5 μm or more or 10.0 μm or more, and can also be 11.8 μm or less or 11.5 μm or less.

The average particle size can also be adjusted by combining a plurality of barium titanate powders obtained by the above method. For example, barium titanate powder obtained by using powder having an average particle size of 3.0 to 5.0 μm (for example, powder collected by a cyclone) in step b, and average particle size in step b Barium titanate powder is obtained by combining with barium titanate powder obtained using powder (for example, powder collected by a heat exchanger) having a diameter of 9.0 to 12.0 μm. good too. The barium titanate powder thus obtained has an average particle size of, for example, 6.0 to 8.0 μm.

When step b is performed in the above method, the particles have a dense structure due to firing, so the BET specific surface area of the resulting barium titanate powder tends to be smaller than when step b is not performed. . Specifically, for example, barium titanate powder having a BET specific surface area of 0.60 to 0.70 m ² /g can be obtained under the condition that the average particle diameter is 3.0 to 5.0 μm. . Further, for example, under the condition that the average particle size is 9.0 to 12.0 μm, a barium titanate powder having a BET specific surface area of 0.25 to 0.30 m ² /g can be obtained. Further, as described above, when the average particle size is 6.0 to 8.0 μm by combining a plurality of barium titanate powders, titanium having a BET specific surface area of 0.40 to 0.50 m ² /g A barium acid powder can be obtained.

EXAMPLES The content of the present invention will be described in more detail below using examples, but the present invention is not limited to the following examples.

<Examples 1 to 4>
(Production of barium titanate powder)
[Preparation of raw material composition]
As barium titanate raw material particles, “BT-SA” manufactured by Kyoritsu Materials Co., Ltd. (barium titanate particles (BaTiO ₃ ), average particle size D50: 1.6 μm, BET specific surface area: 2.28 m ² /g) was used. prepared. As metal oxide particles, “UFP-30” (silica fine powder (SiO ₂ ), average particle diameter D50: 100 nm, BET specific surface area: 30.9 m ² /g) manufactured by Denka Co., Ltd. was prepared. These were mixed with water to prepare a slurry-like raw material composition. The solid content (barium titanate raw material particles and metal oxide particles) of the raw material composition has a concentration of 40% by mass, and the mixing ratio (BaTiO ₃ :SiO ₂ ) of the barium titanate raw material particles and the metal oxide particles is The mass ratio was 99.5:0.5-95.0-5.0.

[Step a: Melting spheroidization]
A combustion furnace with a double-tube structure LPG-oxygen mixed burner capable of forming inner and outer flames installed at the top, a collection system line directly connected to the bottom of the combustion furnace, and connected to the collection system line. An apparatus was provided comprising a blown blower and a. The collection system line has a heat exchanger connected to the combustion furnace, a cyclone connected to the upper part of the heat exchanger, and a bag filter connected to the upper part of the cyclone, and the bag filter is connected to the blower. It is connected.

A high-temperature flame (temperature: about 2000° C.) is formed in the combustion furnace of the above apparatus, and the raw material composition is supplied from the center of the burner at a rate of 37 L/Hr (25 kg/h in terms of solid content) and carrier air. (supply rate: 40 to 45 m ³ /h). A flame is formed by providing dozens of pores at the exit of a burner with a double-tube structure, and through the pores, a mixed gas of LPG (supply rate 17 m ³ /h) and oxygen (supply rate 90 m ³ /h). It was done by spraying. As a result, spherical barium titanate composite particles were formed.

[Step c: Classification]
The barium titanate composite particles formed in the combustion furnace are sucked by a blower, and the powder containing the barium titanate composite particles is collected in each of the combustion furnace, heat exchanger, cyclone and bag filter. Among the plurality of powders, the powder (CY product) collected by the cyclone was used as the barium titanate powder of Examples 1-4.

(Evaluation of the physical properties)
[Measurement of true specific gravity]
The true specific gravities of the barium titanate powders of Examples 1 to 4 were measured with an Auto True Dense MAT-7000 manufactured by Seishin Enterprise Co., Ltd. Table 1 shows the results.

[Measurement of average sphericity]
The average sphericity of the barium titanate powders of Examples 1 to 4 was measured by the following method. First, a barium titanate powder and ethanol were mixed to prepare a slurry having a barium titanate powder concentration of 1% by mass. Dispersion processing was performed at power level 8 for 2 minutes. The resulting dispersion slurry was dropped onto a sample stage coated with carbon paste using a dropper. After standing in the air on the sample stage until the dropped slurry was dried, osmium coating was performed to obtain a powder for evaluation. The obtained powder for evaluation was photographed with a scanning electron microscope "JSM-6301F type" manufactured by JEOL Ltd. Photographing was performed at a magnification of 3000 times to obtain an image with a resolution of 2048×1536 pixels. The obtained image was imported into a photographing personal computer, and particles were recognized using an image analysis device "MacView Ver. From the projected area (A) and perimeter (PM) of the particles, the sphericity of 200 particles having an arbitrary projected area equivalent circle diameter of 2 μm or more was obtained, and the average value was taken as the average sphericity. Table 1 shows the results.

[Measurement of average particle size]
The average particle size (D50) of the barium titanate powders of Examples 1 to 4 was measured by mass-based particle size by laser diffraction light scattering method using Malvern's "Mastersizer 3000, wet dispersion unit: Hydro MV installed". Obtained by measurement. At the time of measurement, barium titanate powder was mixed with water, and pretreatment was performed for 2 minutes using an "ultrasonic generator UD-200 (equipped with a micro chip TP-040)" manufactured by Tomy Seiko Co., Ltd. with an output of 200 W. After performing dispersion treatment on the mixed solution by applying a heat treatment, the mixed solution after the dispersion treatment was added dropwise to the dispersion unit so that the laser scattering intensity was 10 to 15%. The stirring speed of the stirrer of the dispersing unit was 1750 rpm, and the ultrasonic mode was not used. The particle size distribution was analyzed by dividing the particle size range of 0.01 to 3500 μm into 100 parts. The refractive index of water was 1.33, and the refractive index of barium titanate was 2.40. Table 1 shows the results.

[Measurement of BET specific surface area]
The BET specific surface areas of the barium titanate powders of Examples 1 to 4 were measured by the following method. First, an empty cell was filled with 4 g of barium titanate powder, and degassing was performed in an environment of 300°C. After the degassing treatment, the cell filled with the barium titanate powder was set in a fully automatic specific surface area measuring device "Macsorb Model 1208" manufactured by Mountec Co., Ltd. to measure the specific surface area. A mixed gas of He—N ₂ was used as the measuring gas, and the measurement was carried out by the multi-point method at a main body flow rate of 25 mL/min. Table 1 shows the results.

[Measurement of electrical conductivity of extracted water]
The electrical conductivities of extracted water of the barium titanate powders of Examples 1 to 4 were measured by the following method. First, 30 g of barium titanate powder was put into a 300 mL polyethylene container, and then 142.5 mL of ion-exchanged water with an electrical conductivity of 1 μS/cm or less and 7.5 mL of ethanol with a purity of 99.5% or more were added. . Next, using "Double Action Lab Shaker SRR-2" manufactured by AS ONE Co., Ltd., the obtained mixed solution was shaken by a reciprocating shaking method for 10 minutes, and then left to stand for 30 minutes. ) was prepared. The electrical conductivity cell was immersed in the sample solution after standing, and after 1 minute, the value was read and taken as the extracted water electrical conductivity. As the electrical conductivity of the ion-exchanged water, the electrical conductivity cell was immersed in 150 mL of the ion-exchanged water, and the value read after 1 minute was used. For the measurement of electrical conductivity, an electrical conductivity meter "CM-30R" and an electrical conductivity cell "CT-57101C" manufactured by DKK Toa Co., Ltd. were used. Table 1 shows the results.

[Evaluation of dielectric constant]
The relative dielectric constants of the barium titanate powders of Examples 1 to 4 were measured using a powder dielectric constant measuring device "TM Cavity Resonator" (cylindrical cavity resonance method) manufactured by Keycom Co., Ltd. Table 1 shows the results.

<Comparative Example 1>
In the same manner as in Examples 1 to 4, except that a slurry (solid content concentration: 40% by mass), which is a mixture of "BT-SA" manufactured by Kyoritsu Material Co., Ltd. and water, was used as the raw material composition. Step a (melting spheroidization) and step c (classification) were carried out. Of the powder collected in step c, the powder collected by the cyclone (CY product) was used as the barium titanate powder of Comparative Example 1. Next, in the same manner as in Examples 1 to 4, the "physical property evaluation" of the barium titanate powder of Comparative Example 1 was performed. Table 1 shows the results.

<Examples 5 to 8>
Step a (melting spheroidization) and step c (classification) were carried out in the same manner as in Examples 1-4. Among the powders collected in the step c, the powders (CY products) collected by the cyclone were each used to perform the step b (firing) described below. That is, in Examples 5 to 8, powder having an average particle diameter of 9.0 to 12.0 μm and a true specific gravity of 5.40 to 5.90 g/cm ³ was used in step b.

[Step b: Firing]
A mullite sheath was filled with 8 kg of the powder collected by the cyclone, heated to 1000° C. at a rate of 3.3° C./min, and fired at 1000° C. for 6 hours to obtain a fired product. Cooling after firing was performed by natural cooling in the furnace.

The fired product obtained in step b was used as the barium titanate powder of Examples 5-8. Next, in the same manner as in Examples 1-4, the "physical property evaluation" of the barium titanate powders of Examples 5-8 was carried out. Table 2 shows the results.

<Analysis/Evaluation>
[Observation of cross-section]
The cross section of the barium titanate composite particles contained in the barium titanate powder obtained in the example was observed. Specifically, first, 0.1 g of barium titanate powder was embedded in 0.3 g of epoxy resin "G2" manufactured by Gatan. Next, after performing deaeration treatment at 90° C. for 90 minutes, the epoxy resin was cured by heating at 130° C. for 30 minutes to obtain a resin molding containing barium titanate powder. At this time, the size of the resin molding was about 5 mm×10 mm×3 mm. After curing, SiC paper was used to polish the surface of the resin to planarize it, and milling was performed using an ion milling device (trade name: “IM4000Plus”) manufactured by Hitachi High-Tech Co., Ltd. After that, an osmium coating treatment was performed using an osmium coater (trade name “HPC-20”) manufactured by Vacuum Device Co., Ltd. Then, the coated surface was observed with an SEM (scanning electron microscope) to obtain a cross-sectional SEM image. The obtained cross-sectional SEM images are shown in FIGS. 2 is a cross-sectional SEM image of the barium titanate composite particles of Example 4, and FIG. 3 is a cross-sectional SEM image of the barium titanate composite particles of Example 8. FIG. As shown in FIGS. 2 and 3, it was confirmed that a plurality of island-like regions 2A and a sea-like region 3A surrounding the island-like regions 2A were present in the cross section of the barium titanate-based composite particles. rice field. Although not shown, the cross-sections of the barium titanate composite particles of Examples 1 to 3 and 5 to 7 also had a plurality of island regions and sea regions surrounding the island regions. It was confirmed that

Using an EDS (Energy Dispersive X-ray Spectroscopy) device attached to the SEM, elemental analysis was performed on the island-shaped regions and sea-shaped regions in the cross section observed above, and Ba, It was confirmed that Ti and O were contained, and that Ba, Ti, Si and O were contained in the ocean-like region.

[XRD crystal structure analysis]
The powder XRD patterns of the barium titanate powders obtained in Examples and Comparative Examples were measured using D8 advance (manufactured by BRUKER, detector: LynxEye). Next, it was confirmed by the Rietveld method that the barium titanate powder contained BaTiO ₃ and Ba ₂ TiSi ₂ O ₈ . Further, by the same method, the crystal phase was quantified, and the content of BaTiO ₃ (tetragonal phase) and the content of Ba ₂ TiSi ₂ O ₈ (fresnoite phase) were determined based on the total mass of the crystal phase. rice field. Table 3 shows the results.

Claims (16)

A method for producing a powder containing spherical barium titanate composite particles,
A raw material composition containing barium titanate raw material particles and metal oxide particles containing at least one selected from the group consisting of SiO ₂ and Al ₂ O ₃ is prepared by mixing the barium titanate raw material particles and the metal A method for producing powder, comprising the step a of forming spherical barium titanate composite particles by injecting into a high temperature field heated to a melting start temperature or higher of oxide particles. 2. The method for producing a powder according to claim 1, comprising a step b of firing the powder containing the barium titanate composite particles formed in the step a. Before the step b, further comprising a step c of classifying the powder containing the barium titanate composite particles formed in the step a to obtain a plurality of powders having different average particle sizes,
In the step b, among the plurality of powders obtained in the step c, powder having an average particle diameter of 3.0 to 12.0 μm and a true specific gravity of 5.40 to 5.90 g/cm ³ 3. The method for producing powder according to claim 2, wherein the body is fired. The method for producing powder according to any one of claims 1 to 3, wherein the temperature of the high temperature field is 1625 to 2500°C. The method for producing powder according to any one of claims 1 to 4, wherein the raw material composition further contains water. Any one of claims 1 to 5, wherein the content of the barium titanate raw material particles in the raw material composition is 95.0 to 99.5% by mass based on the total solid content of the raw material composition. A method for producing the powder according to the above item. The content of the metal oxide particles in the raw material composition is 0.5 to 5.0% by mass based on the total solid content of the raw material composition, according to any one of claims 1 to 6 A method for producing the described powder. The method for producing powder according to any one of claims 1 to 7, wherein the average particle size of the metal oxide particles is smaller than the average particle size of the barium titanate raw material particles. A powder containing spherical barium titanate composite particles,
The barium titanate-based composite particles contain a barium titanate-based compound and a compound having at least one metal element selected from the group consisting of Si and Al as constituent elements,
A plurality of island-shaped regions and a sea-shaped region surrounding the island-shaped regions are present in the cross section of the barium titanate composite particles,
the island regions contain Ba, Ti and O as constituent elements,
The powder, wherein the sea region contains at least one metal element selected from the group consisting of Si and Al as a constituent element. The powder according to claim 9, wherein the content of the barium titanate-based compound having a tetragonal structure determined by Rietveld analysis of the powder X-ray diffraction pattern is 75.0 to 99.9% by mass. _The powder according to claim 9 or ₁₀ , wherein the barium titanate composite particles contain _Ba2TiSi2O8 . 12. The powder according to claim 11, wherein the content of Ba ₂ TiSi ₂ O ₈ determined by Rietveld analysis of a powder X-ray diffraction pattern is 0.1 to 25.0% by mass. The powder according to any one of claims 9 to 12, having an average particle size of 3.0 to 12.0 µm. The powder according to any one of claims 9 to 13, having an average sphericity of 0.80 or more. 30 g of the powder, 142.5 mL of ion-exchanged water with an electrical conductivity of 1 μS/cm or less, and 7.5 mL of ethanol with a purity of 99.5% or more are mixed, shaken for 10 minutes, and then left to stand for 30 minutes. The powder according to any one of claims 9 to 14, wherein the extraction water has an electric conductivity of 600 µS/cm or less when the extraction water is prepared by A filler for a sealing material, comprising the powder according to any one of claims 9 to 15.

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