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

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

[0001] 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.

Background Art

[0002] Barium titanate-based compounds are known as materials having extremely high relative dielectric constants and are widely used as fillers in various electronic component materials (such as sealing materials, etc.) that require high dielectric properties. In recent years, as materials corresponding to millimeter waves used in the fifth-generation (5G) mobile communication system (for example, fillers for sealing materials used in technologies such as antenna-in-package), particles containing barium titanate-based compounds and powders containing the particles (hereinafter, also referred to as "barium titanate-based powders") have attracted attention.

[0003] Although barium titanate-based compounds themselves have high relative dielectric constants, the effect of improving the relative dielectric constant as a filler varies depending on the method for producing the filler (barium titanate-based powder). Therefore, various methods for producing barium titanate-based powders have been studied.

[0004] For example, Patent Document 1 discloses a method for producing a barium titanate-based powder by melting and spheroidizing a barium titanate-based raw material by spraying the barium titanate-based raw material into a high-temperature flame. According to the barium titanate-based powder obtained by this method, a sealing material having a high relative dielectric constant can be obtained.

[0005] On the other hand, when using a barium titanate-based powder 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 the production process. In contrast, Patent Document 2 discloses a method for reducing the residual amount of ionic impurities and the amount of eluted impurities by subjecting the barium titanate-based powder to ultrasonic treatment in ion-exchanged water.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The main object of the present invention is to provide a barium titanate-based powder with a low elution amount of ionic impurities, and to provide a simple manufacturing method for a barium titanate-based powder with a low elution amount of ionic impurities.

Means for Solving the Problems

[0008] The present invention provides at least the following [1] to

[16] .

[0009] [1] A method for producing a powder containing spherical barium titanate-based composite particles, comprising a step a of forming spherical barium titanate-based composite particles by injecting a raw material composition containing barium titanate-based raw material particles and metal oxide particles containing at least one selected from the group consisting of SiO2 and Al2O3 into a high-temperature field heated to a temperature equal to or higher than the melting start temperature of the barium titanate-based raw material particles and the metal oxide particles.

[0010] [2] The method for producing a powder according to [1], further comprising a step b of firing the powder containing the barium titanate-based composite particles formed in the step a.

[0011] [3] Before the step b, further comprising a step c of classifying the powder containing the barium titanate-based composite particles formed in the step a to obtain a plurality of powders having different average particle diameters, and in the step b, among the plurality of powders obtained in the step c, the average particle diameter is 3.0 to 12.0 μm, and the true specific gravity is 5.40 to 5.90 g / cm 3The method for producing a powder according to [2], which involves firing the powder

[0012] [4] The method for producing a powder according to any one of [1] to [3], wherein the temperature of the high-temperature field is 1625 to 2500 °C.

[0013] [5] The method for producing a powder according to any one of [1] to [4], wherein the raw material composition further contains water.

[0014] [6] The method for producing a powder according to any one of [1] to [5], wherein the content of the barium titanate-based 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.

[0015] [7] The method for producing a powder according to any one 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.

[0016] [8] The method for producing a powder according to any one of [1] to [7], wherein the average particle diameter of the metal oxide particles is smaller than the average particle diameter of the barium titanate-based raw material particles.

[0017] [9] A powder containing spherical barium titanate-based composite particles, wherein 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 a constituent element, and a plurality of island regions and a sea region surrounding the island region are present in the cross-section of the barium titanate-based composite particles, the island region contains Ba, Ti, and O as constituent elements, and the sea region contains at least one metal element selected from the group consisting of Si and Al as a constituent element.

[0018]

[10] The powder according to [9], wherein 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% by mass.

[0019]

[11] The barium titanate-based composite particles-containing powder according to [9] or

[10] , wherein the barium titanate-based composite particles contain Ba2TiSi2O8.

[0020]

[12] The powder according to

[11] , wherein the content of Ba2TiSi2O8 determined by Rietveld analysis of the powder X-ray diffraction pattern is 0.1 to 25.0% by mass.

[0021]

[13] The powder according to any one of [9] to

[12] , having an average particle diameter of 3.0 to 12.0 μm.

[0022]

[14] The powder according to any one of [9] to

[13] , having an average sphericity of 0.80 or more.

[0023]

[15] When 30 g of the powder, 142.5 mL of ion-exchanged water having an electric conductivity of 1 μS / cm or less, and 7.5 mL of ethanol having a purity of 99.5% or more are mixed and shaken for 10 minutes and then allowed to stand for 30 minutes to prepare extracted water, the electric conductivity of the extracted water is 600 μS / cm or less. The powder according to any one of [9] to

[14] .

[0024]

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

[15] .

Advantages of the Invention

[0025] According to the present invention, it is possible to provide a barium titanate-based powder with a small elution amount of ionic impurities. Further, according to the present invention, it is possible to provide a simple production method for a barium titanate-based powder with a small elution amount of ionic impurities.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0027] In this specification, the numerical range indicated using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a certain stepwise numerical range may be replaced with the upper limit value or the lower limit value of another stepwise numerical range. Also, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the experimental examples. Further, the individually described upper limit value and lower limit value can be arbitrarily combined.

[0028] Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments at all.

[0029] <Barium Titanate-Based Powder> The barium titanate-based powder of one embodiment is a powder containing spherical barium titanate-based composite particles. In this specification, "spherical" is not limited to a perfect sphere, but refers to those having an average sphericity of 0.80 or more measured by the method described later.

[0030] 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 a constituent element (hereinafter, also referred to as "Si / Al-based compound").

[0031] Figure 1 is a schematic cross-sectional view of the barium titanate-based composite particles. As shown in the figure, in the cross-section of the barium titanate-based composite particles 1, there are a plurality of island-like regions 2 and a sea-like region 3 surrounding the island-like regions 2. The island-like region 2 is a region containing Ba, Ti, and O as constituent elements, and for example, is a region containing a barium titanate-based compound. The sea-like region 3 is a region containing at least one metal element selected from the group consisting of Si and Al as constituent elements, and for example, is a region containing a Si / Al-based compound. The island-like region 2 and the sea-like region 3 can be observed using an SEM (Scanning Electron Microscope).

[0032] The barium titanate-based powder having the above characteristics has a property of being less likely to cause elution of ionic impurities. Therefore, when the barium titanate-based powder is used as a filler for a sealing material, the occurrence of problems caused by ionic impurities is suppressed, and it is expected that the long-term reliability of the sealing material will be improved. The reason is speculated as follows.

[0033] Ionic impurities mixed during the production of the barium titanate-based powder are, for example, impurities derived from barium titanate-based compounds such as BaCO3 and are present in a phase containing Ba, Ti, and O (for example, a phase containing a barium titanate-based compound). On the other hand, in the barium titanate-based powder, a phase containing Ba, Ti, and O (island-like region in cross-sectional observation) exists surrounded by a phase containing Si and / or Al (sea-like region 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, it is speculated that the elution of ionic impurities from the barium titanate-based powder is less likely to occur.

[0034] (Barium titanate-based compound) Barium titanate-based compounds are perovskite-type oxides containing Ti and Ba as constituent elements. Generally, perovskite-type oxides such as barium titanate have a crystal structure of ABO3. Both the A-site and the B-site are easily substituted by other elements, and it is possible to substitute different elements such as Nd, La, Ca, Sr, Zr, etc. into the crystal structure. In this specification, in addition to barium titanate, compounds in which different elements are substituted at the above A-site and / or B-site of barium titanate are collectively referred to as barium titanate-based compounds. Examples of barium titanate-based compounds include the compound represented by the following formula (1) and the compound represented by the following formula (2). (Ba (1-x) Ca x )(Ti (1-y) Zr y )O3…(1) [In formula (1), x and y satisfy 0 ≦ x + y ≦ 0.4.] La x Ba (1-x) Ti (1-x / 4) O3…(2) [In formula (2), x satisfies 0 < x < 0.14.]

[0035] 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.

[0036] The content of the barium titanate-based compound having a tetragonal crystal structure can be determined by Rietveld analysis of the powder X-ray diffraction (XRD) pattern. From the viewpoint of improving the relative permittivity, 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, and may be 80.0% 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. From the viewpoint of enhancing the effect of suppressing the elution of ionic impurities by the Si / Al-based compound, 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 99.9% by mass or less, and may be 99.7% by mass or less or 99.5% by mass or less. From these viewpoints, the above content may be 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, 93.0 to 99.7% by mass, or 95.0 to 99.5% by mass. The measurement of the powder X-ray diffraction pattern and the Rietveld analysis can be performed using D8 advance (manufactured by BRUKER, detector: LynxEye). In this method, the crystal phases in the powder sample are quantified. Therefore, the above content is the content in the barium titanate-based powder based on the total amount of crystal phases.

[0037] The barium titanate-based composite particles may contain a barium titanate-based compound having a crystal structure other than the tetragonal crystal structure (for example, hexagonal crystal). However, from the viewpoint of improving the relative permittivity, the content of the barium titanate-based compound having a crystal structure other than the tetragonal crystal structure determined by Rietveld analysis of the powder X-ray diffraction pattern is preferably 2.0% by mass or less.

[0038] The barium titanate-based compound may be contained in regions other than the island region 2, but is preferably mainly contained in the island region 2. That is, it is preferable that more than half of the total mass of the barium titanate-based compound contained in the barium titanate-based composite particles is contained in the island region. Therefore, in one example, the island region can also be rephrased as a region containing more than half of the total mass of the barium titanate-based compound contained in the barium titanate-based composite particles.

[0039] In the barium titanate-based composite particles and the barium titanate-based powder, the content of the barium titanate-based compound may be 90.0 to 99.9% by mass, and may also be 93.0 to 99.7% by mass or 95.0 to 99.5% by mass. The above content is the content based on the total mass of the barium titanate-based composite particles or the barium titanate-based powder.

[0040] (Si / Al-based compound) The Si / Al-based compound is, for example, an oxide containing Si and / or Al. The Si / Al-based compound may further have Ti and / or Ba as constituent elements. Examples of the Si / Al-based compound include fresnoite-type oxides represented by Ba2TiSi2O8, AlTiO3, SiO2, Al2O3, etc. When the barium titanate-based composite particles contain Ba2TiSi2O8, the effect of suppressing the elution of ionic impurities tends to increase.

[0041] The content of Ba2TiSi2O8 can be determined by Rietveld analysis of the powder X-ray diffraction pattern. From the viewpoint of more easily suppressing the elution of ionic impurities, the content of Ba2TiSi2O8 determined by Rietveld analysis of the powder X-ray diffraction pattern may be 0.1% by mass or more, and may be 0.3% by mass or more, or 0.5% by mass or more. From the viewpoint of improving the relative permittivity, the content of Ba2TiSi2O8 determined by Rietveld analysis of the powder X-ray diffraction pattern may be 25.0% by mass or less, and may be 20.0% by mass or less, 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 above content may be 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, 0.3 to 7.0% by mass, or 0.5 to 5.0% by mass.

[0042] The Si / Al-based compound may be contained in regions other than region 3 of the sponge-like region, but is preferably mainly contained in region 3 of the sponge-like region. That is, it is preferable that more than half of the total mass of the Si / Al-based compound contained in the barium titanate-based composite particles is contained in region 3 of the sponge-like region. Therefore, in one example, the sponge-like region can also be rephrased as a region containing more than half of the total mass of the Si / Al-based compound contained in the barium titanate-based composite particles.

[0043] The content of the Si / Al-based compound in the barium titanate-based composite particles and in the barium titanate-based powder may be 0.1 to 25.0% by mass, and may be 0.1 to 20.0% by mass, 0.1 to 15.0% by mass, 0.1 to 10.0% by mass, 0.3 to 7.0% by mass, or 0.5 to 5.0% by mass. The above content is the content based on the total mass of the barium titanate-based composite particles or the barium titanate-based powder.

[0044] The barium titanate-based composite particles may contain components other than barium titanate-based compounds and Si / Al-based compounds (impurities, etc.). However, it is preferable that the barium titanate-based composite particles mainly contain barium titanate-based compounds and Si / Al-based compounds. That is, it is preferable that the total content of the barium titanate-based compounds and Si / Al-based compounds in the barium titanate-based composite particles occupies more than half of the total mass of the barium titanate-based composite particles. The total content of the barium titanate-based compounds and Si / Al-based compounds may be 98 to 100% by mass or 99 to 100% by mass based on the total mass of the barium titanate-based composite particles.

[0045] Similarly, the barium titanate-based powder may contain components other than the barium titanate-based composite particles (impurities, etc.). However, it is preferable that the barium titanate-based powder mainly contains the barium titanate-based composite particles. That is, it is preferable that the content of the barium titanate-based composite particles in the barium titanate-based powder occupies more than half of the total mass of the barium titanate-based powder. The content of the barium titanate-based composite particles in the barium titanate-based powder may be 98 to 100% by mass or 99 to 100% by mass based on the total mass of the barium titanate-based powder.

[0046] (Cross-sectional structure of the composite particles) The island region 2 may be composed only of a barium titanate-based compound or may contain components other than the barium titanate-based compound. However, when the island region 2 is analyzed by energy-dispersive X-ray spectroscopy (EDS), it is preferably free of Si and / or Al. From the viewpoint of obtaining a higher relative dielectric constant, it is preferable that the island region 2 is mainly composed of a barium titanate-based compound. That is, it is preferable that more than half of the total area of the island region 2 is composed of a barium titanate-based compound.

[0047] The barium titanate-based compound contained in the island region 2 may form a crystal phase (e.g., tetragonal phase). The island region 2 may be composed of only a crystal phase or may contain an amorphous phase. From the viewpoint of obtaining a higher relative permittivity, the island region 2 is preferably mainly composed of a crystal phase. That is, it is preferable that more than half of the total area of the island region 2 is composed of a crystal phase.

[0048] The area ratio of the island region 2 in the cross-section of the barium titanate-based composite particles may be 70 to 98 area%, may be 80 to 96 area% or 90 to 95 area% from the viewpoint of achieving a better balance between improvement of the relative permittivity and reduction of the elution amount of ionic impurities. The area ratio of the island region 2 can be calculated, for example, by importing a cross-sectional SEM image into image analysis software "ImagePRO", manually selecting the island region 2, and obtaining the area of the island region 2 and the area of the entire particle.

[0049] The sea-like region 3 may be composed of only an 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, the sea-like region 3 is preferably mainly composed of an Si / Al-based compound. That is, it is preferable that more than half of the total area of the sea-like region 3 is composed of an Si / Al-based compound.

[0050] The Si / Al-based compound contained in the sea-like region 3 may form a crystal phase (e.g., fresnoite phase). The sea-like region 3 may be composed of only a crystal phase or may contain an amorphous phase. From the viewpoint of further reducing the elution amount of ionic impurities, the sea-like region 3 is preferably mainly composed of a crystal phase. That is, it is preferable that more than half of the total area of the sea-like region 3 is composed of a crystal phase.

[0051] The area ratio of the sea-like region 3 in the cross-section of the barium titanate-based composite particles may be 12 to 30 area%, 14 to 20 area% or 5 to 10 area% from the viewpoint of more highly achieving both the improvement of the relative permittivity and the reduction of the elution amount of ionic impurities. The area ratio of the sea-like region 3 can be calculated, for example, by importing the cross-sectional SEM image into the image analysis software "ImagePRO", manually selecting the sea-like region 3, and obtaining the area of the sea-like region 3 and the area of the entire particle.

[0052] (Powder physical properties) The extracted water conductivity of the barium titanate-based powder is, for example, 600 μS / cm or less, and may 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. Here, the extracted water conductivity of the barium titanate-based powder means the conductivity of a sample solution (extracted water) prepared by mixing 30 g of the barium titanate-based powder, 142.5 mL of ion-exchanged water with a conductivity of 1 μS / cm or less, and 7.5 mL of ethanol with a purity of 99.5% or more, shaking for 10 minutes, and then standing for 30 minutes. A lower extracted water conductivity of the barium titanate-based powder means a smaller amount of ionic impurities contained in the barium titanate-based powder. Therefore, the lower the extracted water conductivity of the barium titanate-based powder, the more preferable. The extracted water conductivity is the value read 1 minute after immersing the conductivity cell in the sample solution after standing, and the conductivity of the ion-exchanged water is the value read 1 minute after immersing the conductivity cell in 150 mL of ion-exchanged water. The measurement of the above conductivity can be carried out using a conductivity meter "CM-30R" and a conductivity cell "CT-57101C" manufactured by Toa DKK Corporation. Also, the shaking in the above extraction operation can be carried out using a "Double Action Lab Shaker SRR-2" manufactured by AS ONE Corporation. In this embodiment, the extracted water conductivity of the barium titanate-based composite particles may also be within the above range.

[0053] The average particle diameter of the barium titanate-based powder may be set according to the application. From the viewpoint of being suitably used for various electronic component materials, particularly for fillers for encapsulants that require a high relative permittivity, the average particle diameter of the barium titanate-based powder may be 3.0 to 12.0 μm. The average particle diameter of the barium titanate-based powder may be, for example, 3.0 to 5.0 μm, may be 6.0 to 8.0 μm, or may be 9.0 to 12.0 μm. The average particle diameter of the barium titanate-based powder may be 3.2 μm or more or 3.5 μm or more, and may be 6.5 μm or less or 6.0 μm or less. The average particle diameter of the barium titanate-based powder 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. Here, the average particle diameter means the particle diameter (D50) at which the cumulative mass is 50% in the particle size distribution obtained by mass-based particle size measurement by the laser diffraction light scattering method. The average particle diameter can be measured using the "Master Sizer 3000, wet dispersion unit: equipped with Hydro MV" manufactured by Malvern. In addition, in this embodiment, the average particle diameter of the barium titanate-based composite particles may be within the above range.

[0054] The average sphericity of the barium titanate-based powder is 0.80 or more, and may be 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 higher the average sphericity, the more likely the fluidity and moldability of the sealing material will improve, and it becomes easier to increase the filling amount (high filling), so it becomes easier to obtain a sealing material with a higher relative permittivity. 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 may be, 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. Here, the average sphericity means a value measured by the following method. First, the sample powder and ethanol are mixed to adjust a slurry with a sample powder concentration of 1% by mass, and using "SONIFIER450 (crushing horn 3 / 4” solid type)" manufactured by BRANSON, dispersion treatment is performed at an output level of 8 for 2 minutes. The obtained dispersed slurry is dropped onto a sample stage coated with carbon paste using a dropper. On the sample stage, after leaving the dropped slurry to stand in the air until it dries, osmium coating is performed, and this is photographed with a scanning electron microscope "JSM-6301F type" manufactured by JEOL Ltd. The photographing is performed at a magnification of 3000 times to obtain an image with a resolution of 2048×1536 pixels. The obtained image is imported into a photographing personal computer, and using an image analysis device "MacView Ver.4" manufactured by Mount Tech Co., Ltd., particles are recognized using a simple import tool, and sphericity is measured from the projected area (A) and perimeter (PM) of the particles. Assuming the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle is A / B, but assuming a perfect circle (radius r) with the same perimeter as the perimeter (PM) of the sample, PM = 2πr, B = πr 2 Therefore, B = π×(PM / 2π) 2 and the sphericity (A / B) of each particle is A×4π / (PM) 2It becomes like this. The sphericity of 200 particles with an equivalent diameter of a projected area circle of 2 μm or more obtained in this way is determined, and the arithmetic mean value thereof is defined as the average sphericity. In the present embodiment, the average sphericity of the barium titanate-based composite particles may be within the above range.

[0055] From the viewpoint of obtaining a higher relative dielectric constant, the true specific gravity of the barium titanate-based powder is preferably 5.30 to 6.02 g / cm 3 It is. The true specific gravity of the barium titanate-based powder is 5.35 g / cm 3 or more, 5.40 g / cm 3 or more, or 5.42 g / cm 3 or more may be sufficient, and 6.00 g / cm 3 or less, 5.95 g / cm 3 or less, or 5.90 g / cm 3 or less may be sufficient. The true specific gravity can be measured by an Auto True Denser MAT-7000 type manufactured by Seishin Enterprise Co., Ltd. In the present embodiment, the true specific gravity of the barium titanate-based composite particles may be within the above range.

[0056] By the way, in the method of spraying barium titanate-based raw material particles into a high-temperature flame, a space (hollow part) is likely to be formed inside the obtained barium titanate-based particles. Therefore, the barium titanate-based particles tend to have a large number of hollow parts and tend to have a high BET specific surface area. On the other hand, the barium titanate-based composite particles contained in the barium titanate-based powder of the present embodiment have a structure in which a region containing an Si / Al-based compound exists around a region containing a barium titanate-based compound and has few hollow parts, and thus tends to have a relatively small BET specific surface area.

[0057] The barium titanate-based powder described above can be used as various electronic component materials, and in particular, it is preferably used as a filler for a sealing material that requires a high relative dielectric constant. In other words, another embodiment of the present invention is a filler for an electronic component material (preferably for a sealing material) containing the above barium titanate-based powder. Examples of the sealing material include a sealing material used for an antenna-in-package. When the barium titanate-based powder is used as a filler for a sealing material, it can also be used by mixing with other filler components.

[0058] <Method for manufacturing barium titanate-based powder> The manufacturing method of one embodiment is a method for manufacturing a powder (barium titanate-based powder) containing spherical barium titanate-based composite particles. This manufacturing method includes a step a of forming spherical barium titanate-based composite particles by injecting a raw material composition containing barium titanate-based raw material particles and metal oxide particles containing at least one selected from the group consisting of SiO2 and Al2O3 into a high-temperature field heated to a temperature equal to or higher than the melting start temperature of the barium titanate-based raw material particles and the metal oxide particles.

[0059] In the conventional method, in order to reduce the elution amount of ionic impurities, after forming spherical barium titanate-based particles, cleaning operations such as water washing and ultrasonic treatment were required. In contrast, according to the above method, a barium titanate-based powder with a small elution amount of ionic impurities can be obtained without performing a cleaning operation. In addition, the barium titanate-based powder obtained by the above method not only has a small elution amount of ionic impurities but also tends to have a high relative dielectric constant. The reasons for these are speculated as follows.

[0060] In the above method, when the barium titanate-based raw material particles are melted and spheroidized, at least one metal oxide particle selected from the group consisting of SiO2 and Al2O3 is used together with the barium titanate-based raw material particles. Therefore, not only the melting of the barium titanate-based raw material particles but also the melting of the metal oxide particles consumes heat. Therefore, in the above method, it is presumed that overmelting of the barium titanate-based raw material particles is suppressed, and the generation of impurities due to overmelting and the decomposition of the crystal phase into the amorphous phase are suppressed.

[0061] In addition, since the relative permittivity of the barium titanate-based particles themselves tends to decrease by washing, it can also be said that the fact that washing is not necessary in the method of the present embodiment contributes to the improvement of the relative permittivity.

[0062] In addition, the fact that SiO2 and Al2O3 have melting points close to those of barium titanate-based compounds is also considered to be one of the reasons for suppressing the elution of ionic impurities. That is, since SiO2 and Al2O3 have melting points close to those of barium titanate-based compounds, the melting of the metal oxide particles starts before the barium titanate-based raw material particles are completely melted, and a crystal phase derived from the metal oxide particles (for example, the fresnoite phase) is formed around the crystal phase derived from the barium titanate-based raw material particles (for example, the tetragonal phase of the barium titanate-based compound). As a result, it is presumed that the elution of impurities from the crystal phase derived from the barium titanate-based raw material particles is hindered by the crystal phase derived from the metal oxide particles, and the elution of ionic impurities from the barium titanate-based powder is suppressed.

[0063] The barium titanate-based composite particles formed by the above method do not necessarily have a cross-section including an island region and a sea region. However, by making the melting start temperature of the metal oxide particles lower than the melting start temperature of the barium titanate-based raw material particles, the barium titanate-based composite particles contained in the barium titanate-based powder of the above embodiment can be formed. In this case, a barium titanate-based powder with a lower 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. For example, a method of making the particle size of the metal oxide particles smaller than the particle size of the barium titanate-based raw material particles, a method of making the BET specific surface area of the metal oxide particles smaller than the BET specific surface area of the barium titanate-based raw material particles, etc. can be mentioned.

[0064] The above method may further include a step b of firing the powder containing the barium titanate-based composite particles formed in the above step a. By carrying out step b, the relative permittivity tends to be further improved, and the elution amount of ionic impurities also tends to be further reduced.

[0065] The above method may further include a step c of classifying the powder containing the barium titanate-based composite particles formed in the above step a to obtain a plurality of powders with different average particle diameters. This step c may be carried out after step a or may be carried out simultaneously with step a. When the above method further includes step b and step c, step c may be carried out 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-based composite particles formed in step a, and the powder is fired. The powder used in step b preferably has 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 and is a powder.

[0066] Hereinafter, each step (step a, step b, and step c) in the method for producing the barium titanate-based powder will be described.

[0067] (Step a: Melting and Spheroidization) In Process a, by injecting the raw material composition into a high-temperature field, the components in the raw material composition (such as barium titanate-based raw material particles, metal oxide particles, etc.) are melted and solidified to form spherical barium titanate-based composite particles.

[0068] 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 unavoidably contained impurities). However, it is preferable that the barium titanate-based raw material particles contain the barium titanate-based compound as the main component (for example, as the component with the highest mass fraction). The content of the barium titanate-based compound in the barium titanate-based raw material particles may be 98 to 100% by mass, or may be 99 to 100% by mass based on the total mass of the barium titanate-based raw material particles.

[0069] The shape of the barium titanate-based raw material particles is not particularly limited and may be regular or irregular.

[0070] The average particle diameter of the barium titanate-based raw material particles may be 0.5 to 3.0 μm, or may be 1.0 to 2.5 μm or 1.5 to 2.0 μm. The larger the average particle diameter of the barium titanate-based raw material particles, the larger the average particle diameter of the barium titanate-based composite particles obtained in Process a, and the smaller the average particle diameter of the barium titanate-based raw material, the smaller the average particle diameter of the barium titanate-based composite particles obtained in Process a. When the average particle diameter of the barium titanate-based raw material particles is within the above range, in Process a, it is easier to obtain barium titanate-based composite particles with an average particle diameter of 3.0 to 12.0 μm.

[0071] The BET specific surface area of the barium titanate-based raw material particles may be 1.0 to 3.0 m 2 / g, or may be 1.5 to 2.8 m 2 / g or 1.8 to 2.5 m 2 / g.

[0072] The content of the barium titanate-based raw material particles in the raw material composition is preferably 95.0% by mass or more, more preferably 97.0% by mass or more, or even more preferably 98.0% by mass or more, based on the total solid content of the raw material composition, from the viewpoint that a cross-section having the above-described sea-island structure is likely to be formed, and barium titanate-based composite particles that more highly achieve both an improvement in relative permittivity and a reduction in the elution amount of ionic impurities are likely to be obtained. From the same viewpoint, the content of the barium titanate-based raw material particles in the raw material composition is preferably 99.5% by mass or less, more preferably 99.3% by mass or less, or even more preferably 99.0% by mass or less, based on the total solid content of the raw material composition. From these viewpoints, the content of the barium titanate-based raw material particles in the raw material composition is preferably 95.0 to 99.5% by mass, more preferably 97.0 to 99.3% by mass, or even more preferably 98.0 to 99.0% by mass, based on the total solid content of the raw material composition.

[0073] The metal oxide particles are particles containing at least one selected from the group consisting of SiO2 and Al2O3. The metal oxide particles may contain components other than SiO2 and Al2O3 (for example, components such as unavoidably contained impurities). However, the metal oxide particles preferably contain SiO2 and / or Al2O3 as a main component (for example, as the component having the highest mass fraction). The content of SiO2 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 Al2O3 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.

[0074] The shape of the metal oxide particles is not particularly limited and may be regular or irregular. The average particle diameter of the metal oxide particles is preferably smaller than the average particle diameter of the barium titanate-based raw material particles. In this case, the melting start temperature of the metal oxide particles is likely to be lower than the melting start temperature of the barium titanate-based raw material particles, and a cross-section having the above-described sea-island structure is likely to be formed. From the same viewpoint, the BET specific surface area of the metal oxide particles is preferably larger than the BET specific surface area of the barium titanate-based raw material particles.

[0075] The average particle diameter of the metal oxide particles may be 0.01 to 1.50 μm, or may be 0.03 to 1.30 μm or 0.05 to 1.10 μm.

[0076] The BET specific surface area of the metal oxide particles may be 5 to 50 m 2 / g, or may be 20 to 40 m 2 / g or 25 to 35 m 2 / g.

[0077] From the viewpoint of facilitating the formation of a cross-section having the above-described sea-island structure and more easily obtaining barium titanate-based composite particles that achieve a higher degree of both an improvement in relative permittivity and a reduction in the elution amount of ionic impurities, the content of the metal oxide particles in the raw material composition is preferably 0.5% by mass or more, and may be 0.7% by mass or more or 1.0% by mass or more, based on the total solid content of the raw material composition. From the same viewpoint, the content of the metal oxide particles in the raw material composition is preferably 5.0% by mass or less, and may be 3.0% by mass or less or 2.0% by mass or less, based on the total solid content of the raw material composition. From these viewpoints, the content of the metal oxide particles in the raw material composition is preferably 0.5 to 5.0% by mass, and may be 0.7 to 3.0% by mass or 1.0 to 2.0% by mass, based on the total solid content of the raw material composition.

[0078] The ratio of the content of the barium titanate-based raw material particles to the content of the metal oxide particles (barium titanate-based raw material particles: metal oxide particles) may be 99.5:0.5 to 95.0:5.0 by mass, or may be 99.3:0.7 to 97.0:3.0 or 99.0:1.0 to 98.0:2.0, from the viewpoint of facilitating the formation of a cross-section having the above-described sea-island structure and more easily obtaining barium titanate-based composite particles that achieve a higher degree of both an improvement in relative permittivity and a reduction in the elution amount of ionic impurities.

[0079] The raw material composition may further contain water. In this case, the raw material composition may be in the form of a slurry. When the raw material composition containing water (for example, a slurry-like raw material composition) is injected into a high-temperature field in step a, the surface tension of water makes it easier to improve the sphericity of the barium titanate-based composite particles.

[0080] In addition to water, the raw material composition may further contain organic solvents such as methanol and ethanol for the purpose of adjusting the calorific value. These may be used alone or in combination.

[0081] When the raw material composition contains a liquid medium such as water and an organic solvent, the concentration (content) of the solid content may be 1 to 50% by mass, 20 to 47% by mass or 40 to 45% by mass based on the total mass of the raw material composition from the viewpoint of making it easy to increase the sphericity of the barium titanate-based composite particles.

[0082] The high-temperature field may be, for example, a high-temperature flame formed in a combustion furnace or the like. The high-temperature flame can be formed by a combustible gas and an oxidizing gas. The temperature of the high-temperature field (for example, the 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 to 2500 °C, 1625 to 2200 °C, 1625 to 2000 °C, etc.

[0083] As the combustible gas, for example, one or more of propane, butane, propylene, acetylene, hydrogen, etc. can be used. As the oxidizing gas, for example, an oxygen-containing gas such as oxygen gas can be used. However, the combustible gas and the oxidizing gas are not limited to these.

[0084] The injection (spraying) of the raw material composition can be carried out, for example, using a two-fluid nozzle. The injection rate (supply rate) of the raw material composition may be 0.3 to 32 kg / h, or may be 9 to 29 kg / h or 22 to 27 kg / h. When the injection rate of the raw material composition is within the above range, the sphericity of the barium titanate-based composite particles is likely to be improved. When using a slurry-like raw material composition, the injection rates of the barium titanate-based raw material particles and the metal oxide particles in the raw material composition may be within the above range.

[0085] A dispersion gas may be used during the injection of the raw material composition. That is, the raw material composition may be injected while being dispersed in the dispersion gas. Thereby, the sphericity of the barium titanate-based composite particles is likely to be improved. As the dispersion gas, combustion-supporting gases such as air and oxygen, inert gases such as nitrogen and argon, etc. can be used, and combustible gas can also be mixed and used for the purpose of adjusting the calorific value of the gas. The supply rate of the dispersion gas may be 20 to 50 m 3 / h, or may be 30 to 47 m 3 / h or 40 to 45 m 3 / h.

[0086] In the above step a, a powder substantially composed of barium titanate-based composite particles can be obtained. The obtained powder contains, for example, 98 to 100% by mass or 99 to 100% by mass of barium titanate-based composite particles.

[0087] The sphericity of the barium titanate-based composite particles formed in the above step a (the average sphericity of the powder containing the barium titanate-based composite particles) is, for example, greater than 0.70. In the above step a, the sphericity of the barium titanate-based composite particles (the average sphericity of the powder containing the barium titanate-based composite particles) can be made 0.80 or more or 0.85 or more by the injection rate of the raw material composition, the blending amount of the liquid medium, and the use of the dispersion gas, etc. Also, when performing step c described later, it is possible to further increase the sphericity by classification. The maximum value of the sphericity of the barium titanate-based composite particles (the average sphericity of the powder containing the barium titanate-based composite particles) is 1.

[0088] (Process c: Classification) In Process c, the powder containing the barium titanate-based composite particles formed in Process a is classified. The classification method is not particularly limited and may be either screen classification or air classification. From the viewpoint of performing classification efficiently, it is preferable to directly connect a collection system line to the lower part of the combustion furnace in which Process a is carried out, and to suck the barium titanate-based composite particles in the combustion furnace through the collection system line by a blower installed behind the collection system line (on the side opposite to the combustion furnace). The collection system line may have, in addition to a heat exchanger connected to the combustion furnace, a cyclone and a bag filter. The heat exchanger, cyclone, and bag filter may be connected in series in this order. In this case, the powder containing the barium titanate-based composite particles is collected in each of the combustion furnace, heat exchanger, cyclone, and bag filter. The particle size of each collected powder can be adjusted, for example, by the suction amount of the blower or the like.

[0089] When the above collection system line is used in Process c, the powder collected on the upstream side (the side closer to the combustion furnace) tends to have a true specific gravity closer to the specific gravity of the barium titanate-based compound. Among the above collection system lines, 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 closest to the specific gravity of the barium titanate-based compound. For example, it is 5.40 to 5.90 g / cm 3 . The true specific gravity of this powder is 5.40 to 5.80 g / cm 3 , 5.45 to 5.78 g / cm 3 or 5.50 to 5.75 g / cm 3 can also be used. It is presumed that the reason for obtaining such a true specific gravity is that impurities (such as barium carbonate) with a smaller specific gravity are more likely to be mixed in the powder collected on the downstream side (the 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 relative permittivity by firing in Process b described later. When the above collection system line is used in Process c, the sphericity of the powder collected by the cyclone tends to be the highest.

[0090] In step c, classification may be performed such that the average particle diameter of at least one of the obtained powders (powders containing barium titanate-based composite particles) is 5.0 μm or less. By using the powder having the above average particle diameter in step b, the effect of improving the relative permittivity by firing can be easily obtained. Powders having such an average particle diameter can be collected by a cyclone. The average particle diameter of the powder collected by the cyclone is, for example, 3.0 to 5.0 μm, and can also be 3.2 to 4.8 μm or 3.5 to 4.5 μm.

[0091] In step c, classification may be performed such that the average particle diameter of at least one of the obtained powders (powders containing barium titanate-based composite particles) is 9.0 to 12.0 μm. Powders having such an average particle diameter can be collected by a heat exchanger. The average particle diameter of the powder collected by the heat exchanger can also be 9.5 to 11.8 μm or 10.0 to 11.5 μm.

[0092] (Step b: Firing) Step b is a step of firing the powder containing the barium titanate-based composite particles formed in step a.

[0093] As the powder containing the barium titanate-based composite particles formed in step a, one of the plurality of powders obtained by classifying the powder containing the barium titanate-based composite particles formed in step a may be used. That is, in step b, one of the powders obtained in step c may be used. When the above collection system line is used in step c, when the powder collected by the cyclone is used, the relative permittivity of the barium titanate-based powder tends to improve. Also, from the viewpoint of obtaining a higher purity barium titanate-based powder that contains as little other powder such as barium carbonate as possible, it is preferable to use the powder collected by the heat exchanger.

[0094] The average particle diameter of the powder used in step b may be 5.0 μm or less, may be 4.8 μm or less, or may be 4.5 μm or less, from the viewpoint that the relative permittivity of the barium titanate-based powder is likely to be improved. The average particle diameter of the powder used in step b may be 3.0 μm or more, may be 3.2 μm or more, or may be 3.5 μm or more, from the viewpoint of preventing aggregation and sintering of particles during firing. From these viewpoints, the average particle diameter of the powder used in step b may be 3.0 to 5.0 μm, 3.2 to 4.8 μm, or 3.5 to 4.5 μm.

[0095] The average particle diameter of the powder used in step b may be 9.0 to 12.0 μm, from the viewpoint that a higher purity barium titanate-based powder is likely to be obtained. From the same viewpoint, the average particle diameter of the powder used in step b may be 9.5 μm or more, or may be 10.0 μm or more, may be 11.8 μm or less, or may be 11.5 μm or less, and may be 9.5 to 11.8 μm or 10.0 to 11.5.

[0096] The true specific gravity of the powder used in step b may be 5.40 to 5.90 g / cm 3 and may be 5.40 to 5.80 g / cm 3 , 5.45 to 5.78 g / cm 3 or 5.50 to 5.75 g / cm 3 and may also be.

[0097] From the above viewpoints, in one preferred embodiment, the powder containing barium titanate-based composite particles used in step b is a powder having an average particle diameter of 3.0 to 5.0 μm and a true specific gravity of 5.40 to 5.90 g / cm 3 . When the above collection system line is used in step c, a powder having such an average particle diameter and true specific gravity can be easily obtained by collection in a cyclone (cyclone collection).

[0098] From the above viewpoints, in one preferred embodiment, the powder containing barium titanate-based composite particles used in step b is a 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 / cm3 It is a powder. When the above collection system line is used in step c, a powder having such an average particle diameter and true specific gravity can be easily obtained by collection in a heat exchanger (heat exchanger collection).

[0099] The average sphericity of the powder used in step b may be 0.80 or more, and may be 0.82 or more, or 0.85 or more. The maximum value of the average sphericity is 1.

[0100] For the firing (heating) of the powder, a firing furnace may be used. The firing temperature of the powder (for example, the temperature in the firing furnace) may be, for example, 700°C or more, and may be 800°C or more, 900°C or more, 1000°C or more, or 1100°C or more. The firing temperature of the powder may be, for example, 1300°C or less, and from the viewpoint of improving the sphericity, it may be 1200°C or less, 1100°C or less, or 1000°C or less. The firing temperature of the powder may be 800 to 1200°C or 900 to 1100°C from the viewpoint of facilitating the improvement of the relative permittivity of the barium titanate-based powder. The heating rate is not particularly limited, but may be 2 to 5°C / min, and may be 2.5 to 4.5°C / min or 3 to 4°C / min.

[0101] From the viewpoint of facilitating the improvement of the relative permittivity of the barium titanate-based powder, the firing time of the powder may be 2 hours or more, and may be 4 hours or more, or 6 hours or more. When the firing time of the powder is 6 hours or more, the tendency of the above-mentioned improvement in relative permittivity becomes small, so from the viewpoint of production efficiency, the firing time of the powder may be 8 hours or less. Note that the above firing time does not include the heating-up time.

[0102] The cooling conditions after firing are not particularly limited. The cooling after firing may be natural cooling in the furnace.

[0103] According to the method for producing a barium titanate-based powder described above, a barium titanate-based powder having higher purity and a higher relative permittivity can be obtained.

[0104] Specifically, the extracted water electrical conductivity of the barium titanate-based powder produced by the above method is, for example, 600 μS / cm or less. The extracted water electrical conductivity of the barium titanate-based powder can be further reduced by changing the type (shape, etc.) of metal oxide particles, adjusting the blending amount of metal oxide particles, performing classification and firing, etc., and can 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.

[0105] The barium titanate-based powder obtained by the above method tends to have a high sphericity. The average sphericity of the barium titanate-based powder obtained by the above method is, for example, 0.80 or more, and can also be 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, a barium titanate-based powder with an average sphericity close to 1 (for example, 0.80 - 0.99, 0.83 - 0.97, 0.85 - 0.95, 0.86 - 0.93, 0.86 - 0.92, 0.87 - 0.92, 0.88 - 0.92, 0.89 - 0.92, 0.90 - 0.92, etc.) can be obtained.

[0106] The barium titanate-based powder obtained by the above method tends to have a true specific gravity close to the specific gravity of the barium titanate-based compound. The true specific gravity of the barium titanate-based powder obtained by the above method is, for example, 5.64 - 5.91 g / cm 3 and can also be 5.66 - 5.89 g / cm 3 、5.68 - 5.87 g / cm 3 or 5.70 - 5.85 g / cm 3

[0107] ​The average particle size of the barium titanate-based powder obtained by the above method is, for example, 3.0 to 12.0 μm. In step b, when using the powder with an average particle size of 3.0 to 5.0 μm (for example, the powder collected by a cyclone) among the plurality of powders obtained in step c, a barium titanate-based powder with an average particle size of 3.0 to 5.0 μm can be obtained. Also, in step b, when using the powder with an average particle size of 9.0 to 12.0 μm (for example, the powder collected by a heat exchanger) among the plurality of powders obtained in step c, a barium titanate-based powder with an average particle size of 9.0 to 12.0 μm can be obtained. The average particle size of the barium titanate-based powder can be 3.2 μm or more or 3.5 μm or more, and can also be 6.5 μm or less or 6.0 μm or less. Also, the average particle size of the barium titanate-based 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.

[0108] It is also possible to adjust the average particle size by combining a plurality of the barium titanate-based powders obtained by the above method. For example, in step b, a barium titanate-based powder obtained using the powder with an average particle size of 3.0 to 5.0 μm (for example, the powder collected by a cyclone) and a barium titanate-based powder obtained using the powder with an average particle size of 9.0 to 12.0 μm (for example, the powder collected by a heat exchanger) may be combined to obtain a barium titanate-based powder. The average particle size of the barium titanate-based powder thus obtained is, for example, 6.0 to 8.0 μm.

[0109] When step b is carried out in the above method, since the particles become a dense structure by firing, the BET specific surface area of the obtained barium titanate-based powder tends to be smaller compared to the case where step b is not carried out. Specifically, for example, under the condition that the average particle size is 3.0 to 5.0 μm, a barium titanate-based powder with a BET specific surface area of 0.60 to 0.70 m 2 / g can be obtained. Also, for example, under the condition that the average particle size is 9.0 to 12.0 μm, the BET specific surface area is 0.25 to 0.30 m 2Barium titanate-based powder with a BET specific surface area of 0.40 to 0.50 m² / g can be obtained. Also, as described above, when combining a plurality of barium titanate-based powders to have an average particle diameter of 6.0 to 8.0 μm, the BET specific surface area is 0.40 to 0.50 m² / g 2 Barium titanate-based powder with a BET specific surface area of 0.40 to 0.50 m² / g can be obtained.

Example

[0110] Hereinafter, the content of the present invention will be described in more detail using examples, but the present invention is not limited to the following examples.

[0111] <Examples 1 to 4> (Production of barium titanate-based powder) [Preparation of raw material composition] As barium titanate-based raw material particles, "BT-SA" manufactured by Kyoritsu Materials Co., Ltd. (barium titanate particles (BaTiO3), average particle diameter D50: 1.6 μm, BET specific surface area: 2.28 m² / g) was prepared. Also, as metal oxide particles, "UFP-30" manufactured by Denka Co., Ltd. (silica fine powder (SiO2), average particle diameter D50: 100 nm, BET specific surface area: 30.9 m² / g) was prepared. These were mixed with water to prepare a slurry-like raw material composition. The concentration of the solid content (barium titanate-based raw material particles and metal oxide particles) of the raw material composition was 40% by mass, and the mixing ratio of the barium titanate-based raw material particles and the metal oxide particles (BaTiO3:SiO2) was 99.5:0.5 to 95.0:5.0 by mass ratio. 2 / g) was prepared. Also, as metal oxide particles, "UFP-30" manufactured by Denka Co., Ltd. (silica fine powder (SiO2), average particle diameter D50: 100 nm, BET specific surface area: 30.9 m² / g) was prepared. These were mixed with water to prepare a slurry-like raw material composition. The concentration of the solid content (barium titanate-based raw material particles and metal oxide particles) of the raw material composition was 40% by mass, and the mixing ratio of the barium titanate-based raw material particles and the metal oxide particles (BaTiO3:SiO2) was 99.5:0.5 to 95.0:5.0 by mass ratio. 2 / g) was prepared. These were mixed with water to prepare a slurry-like raw material composition. The concentration of the solid content (barium titanate-based raw material particles and metal oxide particles) of the raw material composition was 40% by mass, and the mixing ratio of the barium titanate-based raw material particles and the metal oxide particles (BaTiO3:SiO2) was 99.5:0.5 to 95.0:5.0 by mass ratio.

[0112] [Step a: Melting and spheroidization] An apparatus was prepared comprising a combustion furnace with a double-tube structure LPG-oxygen mixed burner capable of forming an inner flame and an outer flame installed at the top, a collection system line directly connected to the lower part of the combustion furnace, and a blower connected to the collection system line. 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.

[0113] A high-temperature flame (temperature: approximately 2000 °C) was formed in the combustion furnace of the above device, and from the central part of the burner, the above raw material composition was supplied at a supply rate of 37 L / Hr (25 kg / h in terms of solid content), and was injected while entrained in carrier air (supply rate: 40 - 45 m 3 / h). The formation of the flame was achieved by providing dozens of pores at the outlet of the burner with a double-tube structure, and injecting a mixed gas of LPG (supply rate 17 m 3 / h) and oxygen (supply rate 90 m 3 / h) from the pores. Thereby, spherical barium titanate-based composite particles were formed.

[0114] [Step c: Classification] The barium titanate-based composite particles formed in the combustion furnace were sucked by a blower, and powders containing the barium titanate-based composite particles were collected in each of the combustion furnace, heat exchanger, cyclone and bag filter. Among the collected powders, the powders collected by the cyclone (CY products) were used as the barium titanate-based powders of Examples 1 - 4.

[0115] (Physical Property Evaluation) [Measurement of True Specific Gravity] The true specific gravity of the barium titanate-based powders of Examples 1 - 4 was measured using an Auto True Denser MAT-7000 type manufactured by Seishin Enterprise Co., Ltd. The results are shown in Table 1.

[0116] [Measurement of Average Sphericity] The average sphericity of the barium titanate-based powders of Examples 1 to 4 was measured by the following method. First, the barium titanate-based powder and ethanol were mixed to prepare a slurry with a barium titanate-based powder concentration of 1% by mass. Using a "SONIFIER450 (crushing horn 3 / 4" solid type) manufactured by BRANSON, dispersion treatment was performed at an output level of 8 for 2 minutes. The obtained dispersion slurry was dropped onto a sample stage coated with carbon paste using a dropper. On the sample stage, after allowing the dropped slurry to stand in the air until it dried, osmium coating was performed to obtain a powder for evaluation. The obtained powder for evaluation was photographed using a scanning electron microscope "JSM-6301F type" manufactured by JEOL Ltd. The 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 using an image analysis device "MacView Ver.4" manufactured by Mounttech Co., Ltd., particles were recognized using a simple import tool. From the projected area (A) and perimeter (PM) of the particles, the sphericity of 200 particles with an equivalent diameter of 2 μm or more corresponding to an arbitrary projected area circle obtained was determined, and the average value thereof was defined as the average sphericity. The results are shown in Table 1.

[0117] [Measurement of average particle size] The average particle size (D50) of the barium titanate-based powders of Examples 1 to 4 was determined by mass-based particle size measurement by the laser diffraction light scattering method using a "Mastersizer 3000, wet dispersion unit: Hydro MV attached" manufactured by Malvern. In the measurement, the barium titanate-based powder was mixed with water, and as a pretreatment, using an "ultrasonic generator UD-200 (micro tip TP-040 attached) manufactured by Tommy Seiko Co., Ltd.", a dispersion treatment was performed on the mixed solution by applying an output of 200 W for 2 minutes. Then, the mixed solution after the dispersion treatment was dropped into the dispersion unit so that the laser scattering intensity became 10 to 15%. The stirring speed of the stirrer of the dispersion unit was 1750 rpm, and the ultrasonic mode was off. The analysis of the particle size distribution was performed by dividing the range of particle diameter from 0.01 to 3500 μm into 100 parts. A refractive index of 1.33 was used for water, and a refractive index of 2.40 was used for the barium titanate-based material. The results are shown in Table 1.

[0118] [Measurement of BET specific surface area] The BET specific surface areas of the barium titanate-based powders of Examples 1 to 4 were measured by the following method. First, an empty cell was filled with 4 g of the barium titanate-based powder, and degassing treatment was performed in an environment of 300°C. After the degassing treatment, the cell filled with the barium titanate-based powder was set in a fully automatic specific surface area measuring device "Macsorb Model 1208" manufactured by Mounttech Co., Ltd., and the specific surface area was measured. A He-N2 mixed gas was used as the measurement gas, and the measurement was carried out by the multi-point method at a main body flow rate value of 25 mL / min. The results are shown in Table 1.

[0119] [Measurement of the electrical conductivity of the extracted water] The electrical conductivities of the extracted waters of the barium titanate-based powders of Examples 1 to 4 were measured by the following method. First, 30 g of the barium titanate-based 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 a "Double Action Lab Shaker SRR-2" manufactured by AS ONE Corporation, the obtained mixed solution was shaken reciprocally for 10 minutes, and then left standing for 30 minutes to prepare a sample solution (extracted water). An electrical conductivity cell was immersed in the sample solution after standing, and the value was read after 1 minute, and this was taken as the electrical conductivity of the extracted water. For the electrical conductivity of the ion-exchanged water, the value read after immersing an electrical conductivity cell in 150 mL of ion-exchanged water for 1 minute was used. Also, for the measurement of the electrical conductivity, an electrical conductivity meter "CM-30R" and an electrical conductivity cell "CT-57101C" manufactured by Toa DKK Corporation were used. The results are shown in Table 1.

[0120] [Evaluation of relative permittivity] The relative permittivities of the barium titanate-based 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. The results are shown in Table 1.

[0121] [Comparative Example 1] As a raw material composition, except that a slurry (solid content concentration: 40% by mass) which is a mixture of "BT-SA" manufactured by Kyoritsu Materials Co., Ltd. and water was used, steps a (molten spheroidization) and c (classification) were carried out in the same manner as in Examples 1 to 4. Among the powders collected in step c, the powder collected by the cyclone (CY product) was used as the barium titanate-based powder of Comparative Example 1. Next, in the same manner as in Examples 1 to 4, "physical property evaluation" of the barium titanate-based powder of Comparative Example 1 was carried out. The results are shown in Table 1.

[0122]

Table 1

[0123] <Examples 5 to 8> In the same manner as in Examples 1 to 4, steps a (molten spheroidization) and c (classification) were carried out. Among the powders collected in step c, the powders collected by the cyclone (CY products) were each used to carry out step b (firing) described below. That is, in Examples 5 to 8, in step b, powders 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 were used.

[0124] [Step b: Firing] 8 kg of the powder collected by the cyclone was filled into a mullite sagger, heated to 1000 °C at a heating rate of 3.3 °C / min, and then fired at 1000 °C for 6 hours to obtain a fired product. Cooling after firing was carried out by natural cooling in the furnace.

[0125] The fired product obtained in step b was used as the barium titanate-based powder of Examples 5 to 8. Next, in the same manner as in Examples 1 to 4, "physical property evaluation" of the barium titanate-based powders of Examples 5 to 8 was carried out. The results are shown in Table 2.

[0126]

Table 2

[0127] [Analysis and Evaluation] [Observation of Cross-Sectional State] The cross-section of the barium titanate-based composite particles contained in the barium titanate-based powder obtained in the examples was observed. Specifically, first, 0.1 g of the barium titanate-based powder was embedded in 0.3 g of the epoxy resin "G2" manufactured by Gatan. Next, after performing a degassing treatment at 90 °C for 90 minutes, the epoxy resin was cured by heating at 130 °C for 30 minutes to obtain a resin molded body containing the barium titanate-based powder. At this time, the size of the resin molded body was set to approximately 5 mm × 10 mm × 3 mm. After curing, surface finishing was performed by polishing the resin surface using SiC paper, and milling was performed using an ion milling apparatus (trade name "IM4000Plus") manufactured by Hitachi High-Tech Corporation. Then, osmium coating treatment was performed using an osmium coater (trade name "HPC-20") manufactured by Vacuum Devices Co., Ltd. Next, 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 and 3. FIG. 2 is a cross-sectional SEM image of the barium titanate-based composite particles of Example 4, and FIG. 3 is a cross-sectional SEM image of the barium titanate-based composite particles of Example 8. 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 exist in the cross-section of the barium titanate-based composite particles. Although not shown, it was similarly confirmed that a plurality of island-like regions and a sea-like region surrounding the island-like regions also exist in the cross-sections of the barium titanate-based composite particles of Examples 1 to 3 and 5 to 7.

[0128] Using an EDS (Energy Dispersive X-ray Spectroscopy) device attached to the SEM, elemental analysis of the island-like region and the sea-like region in the cross-section observed above was performed, and it was confirmed that Ba, Ti, and O are contained in the island-like region, and Ba, Ti, Si, and O are contained in the sea-like region.

[0129] [XRD Crystal Structure Analysis] The powder XRD patterns of the barium titanate-based powders obtained in the examples and comparative examples were measured using a D8 advance (manufactured by BRUKER, detector: LynxEye). Subsequently, by the Rietveld method, it was confirmed that BaTiO3 and Ba2TiSi2O8 were contained in the barium titanate-based powders. Also, by the same method, the crystal phases were quantified, and the contents of BaTiO3 (tetragonal phase) and Ba2TiSi2O8 (fresnoite phase) were determined based on the total mass of the crystal phases. The results are shown in Table 3.

[0130]

Table 3

Claims

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

2. The method for producing a powder according to claim 1, further comprising a step b of firing the powder containing the barium titanate-based composite particles formed in the step a.

3. Before the step b, the method further includes a step c of classifying the powder containing the barium titanate-based composite particles formed in the step a to obtain a plurality of powders having different average particle diameters. In the step b, among the plurality of powders obtained in the step c, the 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 The method for producing a powder according to claim 2, wherein the powder is fired.

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

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

6. The method for producing a powder according to any one of claims 1 to 5, wherein the content of the barium titanate-based 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.

7. The method for producing a powder according to any one of claims 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.

8. The manufacturing method of the powder according to any one of claims 1 to 7, wherein the average particle diameter of the metal oxide particles is smaller than the average particle diameter of the barium titanate-based raw material particles.

9. A powder containing spherical barium titanate-based composite particles, wherein 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, in the cross section of the barium titanate-based composite particles, there are a plurality of island-like regions and a sea-like region surrounding the island-like regions, the island-like regions contain Ba, Ti, and O as constituent elements, the sea-like region contains at least one metal element selected from the group consisting of Si and Al as a constituent element, the barium titanate-based composite particles contain Ba₂TiSi₂O₈, the powder, wherein the sea-like region contains an oxide containing Si and / or Al.

10. The powder according to claim 9, wherein 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% by mass.

11. The content of Ba ２ TiSi ２ O ８ determined by Rietveld analysis of the powder X-ray diffraction pattern is 0.1 to 25.0% by mass, and the powder according to claim 9 or 10.

12. The powder according to any one of claims 9 to 11, wherein the average particle diameter is 3.0 to 12.0 μm.

13. The powder according to any one of claims 9 to 12, wherein the average sphericity is 0.80 or more.

14. When preparing the extracted water by mixing 30 g of the powder, 142.5 mL of ion-exchanged water with an electric conductivity of 1 μS / cm or less, and 7.5 mL of ethanol with a purity of 99.5% or more, shaking for 10 minutes, and then allowing to stand for 30 minutes, the powder according to any one of claims 9 to 13, wherein the electric conductivity of the extracted water is 600 μS / cm or less.

15. A filler for a sealing material, comprising the powder according to any one of claims 9 to 14.

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