JP2022062686A - Aminopolycarboxylic acid complex powder, additive and method for producing ceramic powder - Google Patents

Abstract

To provide a water-soluble compound which is dissolved with a wide range of pH and is less likely to be solidified in a powder state.SOLUTION: An additive of ceramic powder contains aminopolycarboxylic acid complex powder of a rare earth element having an average particle diameter of 1 μm or more and 1,000 μm or less, and aminopolycarboxylic acid complex powder of the rare earth element, and is used for mixed with ceramic powder. A method for producing ceramic powder containing a rare earth compound in which a particle surface of ceramic powder is coated with a rare earth compound includes mixing an aqueous solution prepared by dissolving aminopolycarboxylic acid complex powder of the rare earth element in water, with ceramic powder and then removing moisture.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing an aminopolycarboxylic acid complex powder, an additive and a ceramic powder.

Rare earth compounds are often used as additives. For example, in a multilayer ceramic capacitor, a highly reliable laminate that does not cause insulation resistance defects by uniformly dispersing rare earth oxides on the surface of ceramic particles such as barium titanate-based ceramic particles, which are the main raw materials for the dielectric layer. It is known that ceramic capacitors can be obtained. (For example, Patent Document 1)
In order to uniformly disperse the rare earth compound around the ceramic particles in this way, the rare earth compound and the ceramic particles are dispersed by a medium in the solvent.
Some rare earth compounds may be water-soluble. For example, Patent Document 2 uses a citric acid complex of dysprosium for the purpose of dispersing a rare earth compound on the surface of ceramic particles. In Patent Document 3, yttrium acetate tetrahydrate or the like is used for the same purpose.

Pamphlet of WO2015 / 040881 Japanese Unexamined Patent Publication No. 2007-20431 Japanese Unexamined Patent Publication No. 2013-163614

When a rare earth compound is used as an additive, it is required to dissolve at a pH at which the main raw material and other additives are easily dispersed. Therefore, it is required to dissolve in a wide range of pH.
Further, if a water-soluble compound of a rare earth element is provided as an aqueous solution, the volume increases and the transportation cost increases. On the other hand, if it is provided as a powder, it will solidify and cause clogging and handling troubles in the production processing line. Therefore, it is required to provide a water-soluble compound that is difficult to consolidate with the powder.

As a result of diligent studies by the present inventor, it was found that the aminopolycarboxylic acid complex powder of a rare earth element having a specific particle size is difficult to solidify and dissolves in a wide range of pH.

The present invention is based on the above findings, and provides an aminopolycarboxylic acid complex powder of a rare earth element having an average particle size of 1 μm or more and 1000 μm or less.

The present invention also provides an additive for a ceramic powder containing an aminopolycarboxylic acid complex powder of a rare earth element and used for mixing with the ceramic powder.

Further, the present invention is a method for producing a ceramic powder containing a rare earth compound, wherein the aminopolycarboxylic acid complex powder of the rare earth element is mixed with an aqueous solution dissolved in water and the ceramic powder, and then water is removed to remove the ceramic. It provides a method for producing a ceramic powder in which the surface of the powder particles is coated with a rare earth compound.

Since the powder of the present invention dissolves in a wide range of pH, the rare earth element can be dissolved in the main raw material slurry which is in a highly dispersed state at a specific pH, and the rare earth compound and the main raw material can be efficiently mixed. Can be done. Further, even if the rare earth element is provided in the form of powder, it is possible to reduce blockage and handling trouble in the production processing line without solidifying.
Further, according to the present invention, there are provided an additive capable of effectively improving the dispersibility of a rare earth compound in a ceramic powder and providing a ceramic powder suitable for a laminated ceramic capacitor, and a method for producing the ceramic powder.

6 is an SEM image showing the appearance of the mixed powder of barium titanate and dysprosium oxide obtained in Example 1. It is a Dy element mapping diagram of the SEM image obtained in FIG. 6 is a Ti element mapping diagram of the SEM image obtained in FIG. 1. 6 is a Ba element mapping diagram of the SEM image obtained in FIG. 1. 6 is an SEM image showing the appearance of the mixed powder of barium titanate and dysprosium oxide obtained in Comparative Example 1. It is a Dy element mapping diagram of the SEM image obtained in FIG. FIG. 5 is a Ti element mapping diagram of the SEM image obtained in FIG. 6 is a Ba element mapping diagram of the SEM image obtained in FIG.

Hereinafter, the present invention will be described in detail based on the preferred embodiment thereof.
The present invention relates to an aminopolycarboxylic acid complex powder of a rare earth element. Aminopolycarboxylic acid complex The aminopolycarboxylic acid complex in the powder refers to a complex in which aminopolycarboxylic acid or a salt thereof is coordinated as a ligand with respect to a central metal atom which is a rare earth element. Aminopolycarboxylic acid is a general term for chelating agents having an amino group and a plurality of carboxy groups in the molecule. Specific examples of the aminopolycarboxylic acid include EDTA (ethylenediaminetetraacetic acid), iminodiacetic acid (IDA), ethyleneglycoltetraacetic acid (EGTA), (HEDTA (hydroxyethylethylenediaminetriacetic acid), NTA (nitrillotriacetic acid), and DTPA. Aminopolyacetic acid such as (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraminehexacetic acid); aminopolysuccinic acid such as hydroxyiminodicosuccinic acid, and examples of the aminopolycarboxylic acid salt include a plurality of aminopolycarboxylic acid salts. A part of the carboxy group refers to a salt having a cation other than rare earth elements such as an ammonium salt, a sodium salt, and a potassium salt. As the aminopolycarboxylic acid, aminopolyacetic acid is preferable in terms of availability, and among them, aminopolyacetic acid is preferable. EDTA is most preferred because it is particularly commonly used. When the aminopolycarboxylic acid is EDTA, the EDTA ligand is usually coordinated to the central element of the rare earth element in a molar ratio of 1: 1. ..

Examples of the rare earth element include at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu, and Y, Dy, Gd, Tb, Ho, and Er are preferable in terms of corrosion resistance to the atmosphere and reactivity with the ceramic powder, and Dy is the most preferable.

The rare earth element aminopolycarboxylic acid complex powder used in the present invention preferably has an average particle size of 1 μm or more and 1000 μm or less. The average particle size of the aminopolycarboxylic acid complex powder of a rare earth element refers to the particle size ( _D50 ) at which the integrated volume from the small particle size side by the laser diffraction / scattering type particle size distribution measurement method becomes 50%.

The rare earth element aminopolycarboxylic acid complex powder has an average particle size (D ₅₀ ) of 1 μm or more, so that it is difficult to solidify even if the powder is left in the air. If the particle size is too small, it will be difficult to produce, so from the viewpoint of ease of production, the average particle size is preferably 10 μm or more. It is more preferable that the average particle size is 10 μm or more because a device such as a high-speed stirrer is not required for manufacturing, or processing for increasing the yield is not required, and the cost is not increased. Specific processing methods include bead mill crushing, jet mill crushing, and sieving. Further, from the viewpoint of the dispersibility of the rare earth compound in the ceramic powder, the average particle size is preferably 1000 μm or less, more preferably 500 μm or less. The average particle size (D ₅₀ ) is a particle size of 50% integrated from the small particle size side measured by the laser diffraction / scattering type particle size distribution measurement method, and specifically, the measurement described in Examples described later. It can be measured by the method.
The average particle size of the aminopolycarboxylic acid complex powder may be 1 μm or more and 1000 μm or less by means of processing means such as bead mill pulverization, jet mill pulverization, and sieving, in addition to the production method described in Examples.

The aminopolycarboxylic acid complex powder of the rare earth element of the present invention preferably has a bulk density in a specific range. Specifically, it is advantageous that the bulk density is 0.5 g / cm ³ or more in terms of measures against solidification. From this viewpoint, the bulk density is more preferably 0.6 g / cm ³ or more, and further preferably 0.7 g / cm ³ or more. Further, it is advantageous that the bulk density is 1.2 g / cm ³ or less in terms of measures against crushing during transportation and work. From this viewpoint, the bulk density is more preferably 1.1 g / cm ³ or less. The bulk density of the aminopolycarboxylic acid complex powder of a rare earth element can be specifically measured by the measuring method described in Examples described later.

The aminopolycarboxylic acid complex powder of the rare earth element of the present invention preferably has a specific surface area in a specific range. Specifically, it is advantageous in terms of solubility that the specific surface area is 0.5 m ² / g or more. Further, it is advantageous that the specific surface area is 5 m ² / g or less in terms of preventing consolidation. From this point of view, the rare earth element aminopolycarboxylic acid complex powder preferably has a specific surface area of 1 m ² / g or more and 4 m ² / g or less, and more preferably 2 m ² / g or more and 3.5 m ² / g or less. preferable. The specific surface area can be measured by the measuring method described in Examples described later.

The bulk density and specific surface area can be realized by, in addition to the production method described in Examples, bead mill crushing, jet mill crushing, processing such as sieving, and adjustment of production conditions (stirring conditions and precipitation temperature).

The aminopolycarboxylic acid complex powder of the rare earth element of the present invention is stable without forming a precipitate in a wide pH range when dissolved in water to form an aqueous solution. Specifically, when an aqueous solution that is soluble in water and has a concentration of 1 g / L is prepared, the aminopolycarboxylic acid complex is in the pH range of 1.0 or more and 13.0 or less at 25 ° C. It is preferable that the precipitate derived from the above does not occur in the aqueous solution. Specifically, 1 g of the rare earth element aminopolycarboxylic acid complex powder is dissolved when mixed with 1 L of a nitrate aqueous solution having a pH of 1 at 25 ° C., and 1 g of the rare earth aminopolycarboxylic acid complex powder is dissolved in 1 L of an aqueous ammonia solution having a pH of 13 at 25 ° C. It dissolves when mixed with. Then, when it is allowed to stand at 25 ° C. for 24 hours, no precipitation occurs visually. The fact that the water-soluble state is stable over such a wide range of pH means that when the aminopolycarboxylic acid complex of the rare earth element of the present invention is mixed with a ceramic powder as described later, the rare earth is uniformly on the surface of each ceramic particle. It is preferable because the compound can be attached. The rare earth compound referred to here refers to an aminopolycarboxylic acid complex of a rare earth element or an oxide of a rare earth element produced by firing the complex.

In the present invention, the term "soluble in water" preferably refers to the property of dissolving 1 g or more in 100 ml of water at 25 ° C.

Further, the present invention provides an additive for a ceramic powder used for mixing with a ceramic powder, which comprises an aminopolycarboxylic acid complex powder of a rare earth element. In the present specification, the meaning that the aminopolycarboxylic acid complex powder of the rare earth element is "used for mixing with the ceramic powder" means that the aminopolycarboxylic acid complex powder of the rare earth element is mixed with the ceramic powder in the powder state. This includes the case where the aminopolycarboxylic acid complex powder of a rare earth element is dissolved in a solvent such as water and mixed with the ceramic powder.

For example, in the technical field of multilayer ceramic capacitors, the oxide of rare earth elements is uniformly dispersed on the surface of ceramic particles such as barium titanate, which is the main raw material of the dielectric layer, so that insulation resistance failure does not occur. It is known that high monolithic ceramic capacitors can be obtained.
As described above, the aminopolycarboxylic acid complex powder of a rare earth element (particularly the aminopolycarboxylic acid complex powder of a rare earth element having a specific particle size) is difficult to solidify and coarse particles are unlikely to remain in the aqueous solution when dissolved in water. .. Further, the aminopolycarboxylic acid complex powder of the rare earth element is difficult to precipitate in a wide pH range and has high water solubility. Therefore, when an aqueous solution of a rare earth element aminopolycarboxylic acid complex powder dissolved in water and a ceramic powder are mixed, the rare earth element aminopolycarboxylic acid complex can be uniformly adhered to the surface of the ceramic particles. By firing the ceramic powder in which the aminopolycarboxylic acid complex of the rare earth element is uniformly attached to the surface of the particles, a rare earth oxide-containing ceramic powder in which the oxide of the rare earth element is uniformly attached to the surface of the ceramic particles can be obtained. By using the obtained rare earth oxide-containing ceramic powder as a laminated ceramic capacitor material, a highly reliable laminated ceramic capacitor with suppressed insulation resistance defects can be obtained. The term "uniformly adhered" as used herein means a state in which the difference in the adhesion thickness, the difference in the adhesion amount, and the uneven distribution of the adhesion position among the particles are suppressed.

On the other hand, the conventional rare earth components are not sufficient from the viewpoint of dispersing the rare earth compounds in the ceramic powder for the laminated ceramic capacitor with high dispersibility.
For example, in Patent Document 1 (Re-Table 2015-040881), an oxide of a rare earth element is dispersed in a ceramic powder in a solvent using a disperser using a dispersion medium such as a ball mill or a bead mill. However, in order to uniformly adhere the compound insoluble in a solvent such as an oxide of a rare earth element to the surface of the ceramic particles, when the ceramic particles are dispersed using a long-term dispersion medium, the ceramic particles are crushed. The original performance may deteriorate due to wear. On the other hand, even if a dispersion medium is used, if the dispersion is performed only for a short time, there is a concern that coarse particles of the rare earth compound remain (see Comparative Example 1 described later).
Further, for example, as a rare earth component to be mixed with a ceramic powder in a solvent, an organic acid complex such as a citric acid complex of a rare earth element is used instead of an oxide of the rare earth element. -204315 (Japanese Patent Laid-Open No. 2013-163614) and Patent Document 3 (Japanese Patent Laid-Open No. 2013-163614). However, although the organic acid complex of a rare earth element tends to adhere uniformly to the surface of ceramic particles, it is necessary to adjust the pH to prevent precipitation or to sufficiently control it so that it does not solidify (Comparative Example 2 described later). And 3).

When the aminopolycarboxylic acid complex of a rare earth element is used for mixing with a ceramic powder, the primary particle size of the ceramic powder is preferably 0.05 μm or more and 1 μm or less. When the primary particle size is 0.05 μm or more, the aggregation of the ceramic powder is suppressed, and there is an advantage that the aminopolycarboxylic acid complex can be easily dispersed in the ceramic powder. Further, since the primary particle size of the ceramic powder is 1.0 μm or less, there is an advantage that the technical significance of the present invention for improving the dispersibility of the rare earth compound in the ceramic powder is great. From this viewpoint, the primary particle size of the ceramic powder is more preferably 0.05 μm or more and 1 μm or less, and further preferably 0.1 μm or more and 0.5 μm or less. The primary particle size is a particle size obtained from the specific surface area s (m ² / g) measured by the BET method. The primary particle diameter d (μm) is d = 6 / (ρs) (ρ is the true density (cm ³ / g)). The method for measuring the BET specific surface area of the ceramic powder is the same as the method for measuring the specific surface area of a rare earth compound such as an aminocarboxylic acid complex powder described later in Examples.

Further, as described above, the ceramic powder is preferably a powder made of a dielectric for a ceramic capacitor from the viewpoint of obtaining the effect of improving the reliability of the ceramic capacitor. As the powder made of a dielectric for a ceramic capacitor, it is preferable to have a perovskite structure in that it has ferroelectricity. Examples of the powder made of a dielectric for a ceramic capacitor having a perovskite structure include barium titanate. In order to improve the reliability of the ceramic capacitor, a dielectric obtained by doping barium titanate with Sr, Ca or the like may be used.

Examples of the properties of the additive of the present invention include powder, flakes, and lumps. Taking advantage of the above-mentioned difficult-to-solidify property of the rare earth element aminocarboxylic acid powder, the additive is powdery from the viewpoint of flowability. Is preferable.
A component other than the aminopolycarboxylic acid complex powder of the rare earth element may be contained as long as the dispersibility of the rare earth compound in the above-mentioned ceramic powder can be improved. The ratio of the rare earth element aminopolycarboxylic acid complex powder to the solid content of the additive of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 30% by mass or more. Most preferably, it may be 50% by mass or more. The solid content refers to the total amount of components excluding the solvent.

Hereinafter, a method for producing a ceramic powder containing a rare earth compound will be described. In the method for producing a ceramic powder of the present invention, the particle surface of the ceramic powder is coated with a rare earth compound by mixing an aqueous solution of an aminopolycarboxylic acid complex powder of a rare earth element in water and the ceramic powder and then removing water. It is something to do.

When mixing an aqueous solution of a rare earth element aminopolycarboxylic acid complex powder in water and a ceramic powder, water, a rare earth element aminopolycarboxylic acid complex powder and a ceramic powder are simultaneously placed in a container and mixed. Alternatively, water and an aminopolycarboxylic acid complex powder of a rare earth element may be mixed to obtain an aqueous solution, and this aqueous solution may be mixed with a ceramic powder.

The reliability of the obtained ceramic capacitor is that the rare earth element aminopolycarboxylic acid complex powder is mixed with 100 mol of the ceramic powder so that the rare earth element in the rare earth element aminopolycarboxylic acid complex is 0.1 mol or more and 10 mol or less. It is preferable from the viewpoint of improving the property, and it is more preferable to mix the mixture so as to be 1 mol or more and 5 mol or less.

Further, the amount of water used is uniformly such that the concentration of the ceramic powder is 5% by mass or more and 70% by mass or less of the total amount of water, the ceramic powder and the aminopolycarboxylic acid complex powder of the rare earth element. The aminopolycarboxylic acid complex of No. 1 is preferable from the viewpoint of adhering to the ceramic powder and lowering the viscosity to improve operability, and more preferably 10% by mass or more and 50% by mass or less.

Moisture is removed from the mixture of the obtained aminopolycarboxylic acid complex, ceramic powder and water to obtain a powder. For the removal of water, it is convenient to perform drying and / or baking. As an example of firing, for example, it can be performed at 500 ° C to 1300 ° C. Examples of the firing atmosphere include an oxygen-containing atmosphere such as the atmosphere. Firing under these conditions makes it possible to coat the surface of the ceramic particles with a rare earth oxide.

Further, the mixing of the ceramic powder with the aminopolycarboxylic acid complex of the rare earth element and water can be performed by mechanical treatment with a homogenizer, a mill (bead mill, ball mill, etc.), a mixer, a grinder, a paint shaker, or the like. In particular, a crushing process using a dispersed medium is preferable. The dispersion time for the slurry is preferably 1 minute or more and 1 hour or less, and more preferably 2 minutes or more and 30 minutes or less.

When the dispersed media is used for mixing the ceramic powder with the aminopolycarboxylic acid complex of the rare earth element and water, the material of the dispersed media is not particularly limited, but from the viewpoint of suppressing the mixing of metal impurities, alumina, zirconia, and silicon carbide are used. Ceramic media such as silicon and silicon nitride are preferred. The zirconia referred to here includes stabilized zirconia such as YSZ and PSZ.

From the viewpoint of shortening the dispersion time and improving the dispersibility, the particle size of the dispersed medium is preferably 0.015 mm or more and 2 mm or less, and more preferably 0.08 mm or more and 1 mm or less. From the viewpoint of shortening the dispersion time and improving the dispersibility, the volume ratio of the slurry to the dispersed media is preferably 1: 0.1 or more and 5 or less, and more preferably 0.5 or more and 1 or less for the former: the latter. ..

Next, a suitable method for producing the aminopolycarboxylic acid complex powder of the present invention will be described.
The aminopolycarboxylic acid complex powder of the present invention can be produced by mixing a water-soluble salt of a rare earth element and an aminopolycarboxylic acid in the presence of water and an alkali. Examples of the water-soluble salt include nitrates and the like. The aminopolycarboxylic acid complex powder is preferably obtained by washing the precipitated powder with ethanol and then heating it at 30 to 80 ° C. for 5 hours to 24 hours in an air atmosphere having a relative humidity of 50% or less in the step. .. By going through such an ethanol washing / drying process, particles having an average particle diameter of 1000 μm or less can be successfully produced.

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the invention is not limited to such examples.

[Example 1] (Dy-EDTA complex powder)
0.44 mol of ethylenediaminetetraacetic acid was added to 200 ml of pure water, and 150 ml of caustic soda of 24% by mass was added and dissolved. An aqueous solution prepared by dissolving 0.44 mol of dysprosium nitrate n hydrate in 150 ml of pure water was added to this aqueous solution, and the mixture was stirred at room temperature for 2 hours with a stirrer at 100 rpm. After filtering the precipitated solid, it was repeatedly washed 3 times with 150 ml of ethanol and dried at 50 ° C. for 10 hours in an air atmosphere with a relative humidity of 50% to obtain 135 g of dysprosium-EDTA complex powder, which was used as one batch. , Samples were created for the number of batches required for the experiment.
When the specific surface area, bulk density, and average particle size of the obtained dysprosium-EDTA complex powder were measured by the following methods, the specific surface area was 3.2 m ² / g, the bulk density was 0.84 g / cm ³ , and the average particle size was It was 29.3 μm.
The obtained dysprosium-EDTA complex powder was dissolved when 1 g was mixed with 1 L of an aqueous solution of nitric acid having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous solution of ammonia having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
When 20 g of the obtained dysprosium-EDTA complex was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, the dysprosium-EDTA complex remained in powder form, and the sieving rate was increased with an ultrasonic sieve having a mesh size of 500 μm. It was able to sift at 100% and did not solidify. The average particle size did not change much after being left for 72 hours.

(Measuring method of specific surface area)
It was measured by the BET 1-point method using a fully automatic specific surface area meter Macsorb model-1201 manufactured by Mountech. The gas used was a nitrogen-helium mixed gas (nitrogen 30 vol%). As a pretreatment for measurement, powder was put into a glass cell and set in an apparatus, nitrogen gas was circulated through the set glass cell, and the mixture was dried at 150 ° C. for 60 minutes.

(Measuring method of bulk density)
Multi-functional powder physical property measuring instrument Multi-tester MT-1000 (manufactured by Seishin Corporation) was used, except that the powder was not supplied without passing through a sieve. The bulk density was measured according to the method for measuring the static bulk density (sparsest filling bulk density).

(Measuring method of average particle size)
The measurement was performed with a Microtrack MT3300EXII manufactured by Nikkiso Co., Ltd. At the time of measurement, ethanol was used as the dispersion medium, the sample was added to the chamber of the sample circulator of Microtrac MT3300EXII, and the dispersion treatment was performed with the ultrasonic waves installed in MT3300EXII at an output of 40 W and 300 seconds. D ₅₀ was measured after the device determined that it was a concentration.

(Dispersity test with barium titanate powder)
Barium titanate powder (primary particle diameter 0.1 μm, BTHP-100 manufactured by KCM Corporation) and pure water were mixed to obtain a barium titanate slurry of 10% by mass. The pH of this slurry was 10.0 at 25 ° C.
The volume ratio of 4 mol parts of the dysprosium-EDTA complex powder as Dy and YTZ beads (manufactured by Nikkato Co., Ltd.) having a diameter of 0.1 mm is the slurry with respect to 100 mol parts of barium titanate in the barium titanate slurry. : YTZ beads = 1: 2 were placed in a container and crushed with a paint shaker for 3 minutes. The obtained slurry was dried at 120 ° C. and then calcined at 1000 ° C. for 3 hours in an air atmosphere to obtain a mixed powder of barium titanate and dysprosium oxide.
The results of observing this powder with a scanning electron microscope are shown in FIGS. 1 to 4. In FIGS. 1 to 4, it can be seen that the Dy compound (dysprosium oxide) is uniformly dispersed around the barium titanate and there are no coarse particles.
In the mixing test with this barium titanate powder, not the dried dysprosium-EDTA complex powder, but the dysprosium-EDTA before ultrasonic sieving after leaving it in the air at 24 ° C and 78% relative humidity for 72 hours. Complex powder was used.

[Comparative Example 1] (Dysprosium oxide powder)
Dysprosium oxide powder (manufactured by Yttrium Japan Co., Ltd.) was prepared. The prepared dysprosium oxide powder had a specific surface area of 10 m ² / g, an average particle size of 0.5 μm, and a bulk density of 0.5 g / cm ³ .
The dispersibility test with the barium titanate powder was carried out in the same manner except that the dysprosium oxide powder was used instead of the dysprosium-EDTA complex powder to obtain a mixed powder of barium titanate and dysprosium oxide.
The results of observing this powder with a scanning electron microscope are shown in FIGS. 5 to 8. In FIG. 6, it can be seen that coarse particles of the Dy compound (dysprosium oxide) are particularly present in the arrow portion.

[Example 2] (Y-EDTA complex powder)
In Example 1, dysprosium nitrate was changed to yttrium nitrate. A Y-EDTA complex powder was obtained in the same manner as in Example 1 except for this point. The specific surface area of the obtained complex powder was 1.3 m ² / g, the bulk density was 0.88 g / cm ³ , and the average particle size was 32.3 μm.
The obtained yttrium-EDTA complex powder was dissolved when 1 g was mixed with 1 L of an aqueous solution of nitric acid having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous solution of ammonia having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
When the obtained complex powder was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, it remained in the form of powder and could be sieved with an ultrasonic sieve having a mesh size of 500 μm at a sieving rate of 100%. It did not solidify. The average particle size did not change much after being left for 72 hours.
Further, the dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the Y-EDTA complex powder was used instead of the dysprosium-EDTA complex powder and 4 mol part was used as Y. A mixed powder of barium titanate and yttrium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Y compound (yttrium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Example 3] (Ho-EDTA complex powder)
In Example 1, dysprosium nitrate was changed to holmium nitrate. A Ho-EDTA complex powder was obtained in the same manner as in Example 1 except for this point. The specific surface area of the obtained complex powder was 1.0 m ² / g, the bulk density was 0.93 g / cm ³ , and the average particle size was 27.5 μm.
The obtained holmium-EDTA complex powder was dissolved when 1 g was mixed with 1 L of an aqueous solution of nitric acid having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous solution of ammonia having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
When the obtained complex powder was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, it remained in the form of powder and could be sieved with an ultrasonic sieve having a mesh size of 500 μm at a sieving rate of 100%. It did not solidify. The average particle size did not change much after being left for 72 hours.
Further, the dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the Ho-EDTA complex powder was used instead of the dysprosium-EDTA complex powder and 4 mol part was used as Ho. A mixed powder of barium titanate and holmium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Ho compound (holmium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Example 4] (Production of Yb-EDTA complex powder)
In Example 1, dysprosium nitrate was changed to ytterbium nitrate. Aminopolycarboxylic acid complex powder was obtained in the same manner as in Example 1 except for this point. The specific surface area of the obtained complex powder was 2.6 m ² / g, the bulk density was 0.99 g / cm ³ , and the average particle size was 29.1 μm.
The obtained ytterbium-EDTA complex powder was dissolved when 1 g was mixed with 1 L of an aqueous solution of nitric acid having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous solution of ammonia having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
When the obtained complex was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, it remained in the form of powder, and could be sieved with an ultrasonic sieve having a mesh size of 500 μm at a sieving rate of 100% and solidified. I didn't connect. The average particle size did not change much after being left for 72 hours.
Further, the dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the Yb-EDTA complex powder was used instead of the dysprosium-EDTA complex powder and 4 mol part was used as Yb. A mixed powder of barium titanate and ytterbium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Yb compound (ytterbium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Comparative Example 2] (Dy citric acid complex)
After dissolving 0.2 mol of dysprosium nitrate and 0.6 mol of citric acid monohydrate in 550 g of ethanol, 150 ml of caustic soda was added and the mixture was stirred for 2 hours. The precipitate was filtered and washed repeatedly with 150 ml of ethanol three times, and then dried at 50 ° C. for 10 hours in an air atmosphere to obtain a dysprosium-citric acid complex. The specific surface area of the obtained complex powder was 0.4 m ² / g, the bulk density was 0.74 g / cm ³ , and the average particle size was 78.6 μm.
1 g of the obtained dysprosium-citric acid complex was dissolved when mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C., and 1 g was dissolved when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
Further, after the obtained dysprosium-citric acid complex was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, it solidified into a large mass, and even if it was sieved with a 500 μm sieve, only 2% was shaken. In other words, it consolidated into one big mass in the atmosphere.
Therefore, it was not possible to carry out a dispersibility test with the barium titanate powder.

[Comparative Example 3]
Dysprosium acetate powder was obtained by dissolving 0.3 mol of dysprosium oxide (0.6 mol as a Dy element) in 172.2 ml of an acetic acid aqueous solution having a concentration of 80% by mass heated to 90 ° C. and cooling and crystallizing. The specific surface area of the obtained dysprosium acetate powder was 5.0 m ² / g, the bulk density was 1.0 g / cm ³ , and the average particle size was 30.0 μm.
The obtained dysprosium acetate powder was dissolved when 1 g was mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C., but was not dissolved even when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. No precipitate was deposited even when the solution after being dissolved in 1 L of a nitric acid aqueous solution having a pH of 1 was allowed to stand at 25 ° C. for 24 hours. Further, the mixture mixed with the aqueous solution of pH 13 did not dissolve even when allowed to stand at 25 ° C. for 24 hours.
When the obtained dysprosium acetate powder was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours, it remained in the form of powder and could be sieved with an ultrasonic sieve having a mesh size of 500 μm at a sieving rate of 100%. , Did not solidify. The average particle size did not change much after being left for 72 hours.
Further, the dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the dysprosium acetate complex powder was used instead of the dysprosium-EDTA complex powder, and the barium titanate and dysprosium oxide were mixed. Obtained powder. When this powder was observed with a scanning electron microscope, coarse particles of Dy compound (dysprosium oxide) were present.

[Example 5]
In the method for producing the dysprosium-EDTA complex according to Example 1, the specific surface area is 4.1 m ² / g and the bulk density is 0.8 g / g by stirring at 1000 rpm with a high-speed stirrer instead of stirring at 100 rpm with a stirrer. A dysprosium-EDTA complex powder having a cm of ³ and an average particle size of 8.3 μm was obtained.
The obtained dysprosium-EDTA complex powder was dissolved when 1 g was mixed with 1 L of an aqueous solution of nitric acid having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous solution of ammonia having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
This dysprosium-EDTA complex having an average particle size of less than 10 μm was left in the air at 24 ° C. and a relative humidity of 78% for 72 hours in the same manner as in Example 1, but sieved with an ultrasonic sieve having an opening of 500 μm at a sieving rate of 100%. I was able to do it and it didn't solidify. The average particle size did not change much after being left for 72 hours.
The dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the obtained dysprosium-EDTA complex powder was used in place of the complex powder obtained in Example 1, and the barium titanate and barium titanate were subjected to a dispersibility test. A mixed powder of dysprosium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Dy compound (dysprosium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Example 6]
In the method for producing the dysprosium-EDTA complex according to Example 1, the specific surface area is 4.8 m ² / g and the bulk density is 0.7 g / g by stirring at 10000 rpm with a high-speed stirrer instead of stirring at 100 rpm with a stirrer. A dysprosium ^- EDTA complex having an average particle size of 1.0 μm was obtained.
The dysprosium-EDTA complex powder having an average particle size of 1.0 μm was dissolved when 1 g was mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C., and 1 g was dissolved when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
This dysprosium-EDTA complex having an average particle size of 1.0 μm was left in the air at 24 ° C. and a relative humidity of 78% in the same manner as in Example 1 for 72 hours, but with an ultrasonic sieve having an opening of 500 μm and a sieving rate of 100%. It was able to sift and did not solidify. The average particle size did not change much after being left for 72 hours.
The dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the obtained dysprosium-EDTA complex powder was used in place of the complex powder obtained in Example 1, and the barium titanate and barium titanate were subjected to a dispersibility test. A mixed powder of dysprosium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Dy compound (dysprosium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Example 7]
In the method for producing the dysprosium-EDTA complex according to Example 1, the amount of ethanol used for the ethanol washing carried out in Example 1 was changed from 150 ml to 20 ml and washed three times repeatedly, and the air atmosphere had a relative humidity of 50%. By drying under 50 ° C. for 10 hours, a dysprocium-EDTA complex powder having a specific surface area of 0.6 m ² / g, a bulk density of 1.1 g / cm ³ and an average particle size of 800 μm was obtained.
The dysprosium-EDTA complex powder having an average particle size of 800 μm was dissolved when 1 g was mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C., and 1 g was dissolved when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
This dysprosium-EDTA complex was left in the air for 72 hours in the same manner as in Example 1, but the average particle size did not change and it did not solidify. The average particle size did not change much after being left for 72 hours.
The dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the obtained dysprosium-EDTA complex powder was used in place of the complex powder obtained in Example 1, and the barium titanate and barium titanate were subjected to a dispersibility test. A mixed powder of dysprosium oxide was obtained.
When this powder was observed with a scanning electron microscope, the Dy compound (dysprosium oxide) was uniformly dispersed around barium titanate, and there were no coarse particles.

[Comparative Example 4]
In the method for producing a dysprosium-EDTA complex according to Example 1, the step of repeatedly washing with 150 ml of ethanol in Example 1 three times is not performed, and the temperature is 50 ° C. for 10 hours in an air atmosphere having a relative humidity of 50%. It was dry. Dysprosium-EDTA complex powder having an average particle diameter of 1800 μm, a specific surface area of 0.3 m ² / g, and a bulk density of 1.3 g / cm ³ was obtained by drying aggregation.
The dysprosium-EDTA complex powder having an average particle size of 1800 μm was dissolved when 1 g was mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C., and 1 g was dissolved when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
This dysprosium-EDTA complex was left in the air for 72 hours in the same manner as in Example 1, but the average particle size did not change and it did not solidify.
The dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the obtained dysprosium-EDTA complex powder was used in place of the complex powder obtained in Example 1, and the barium titanate and barium titanate were subjected to a dispersibility test. A mixed powder of dysprosium oxide was obtained.
When this powder was observed with a scanning electron microscope, coarse particles of Dy compound (dysprosium oxide) were present.

[Comparative Example 5]
In the method for producing the dysprosium-EDTA complex according to Example 1, the specific surface area is 5.3 m ² / g and the bulk density is 0.5 g / g by stirring at 20000 rpm with a high-speed stirrer instead of stirring at 100 rpm with a stirrer. A dysprosium ^- EDTA complex having an average particle size of 0.5 μm was obtained.
This dysprosium-EDTA complex powder having an average particle size of 0.5 μm was dissolved when 1 g was mixed with 1 L of a nitric acid aqueous solution having a pH of 1 at 25 ° C, and 1 g was dissolved when 1 g was mixed with an aqueous ammonia solution having a pH of 13 at 25 ° C. In either case, no precipitate was deposited even when the dissolved liquid was allowed to stand at 25 ° C. for 24 hours.
This dysprosium-EDTA complex having an average particle size of 0.5 μm is solidified after being left in the air at 24 ° C. and a relative humidity of 78% for 72 hours in the same manner as in Example 1, and only 30% is sieved by a sieve of 500 μm. I didn't shake.
The dispersibility test with the barium titanate powder was carried out in the same manner as in Example 1 except that the obtained dysprosium-EDTA complex powder was used in place of the complex powder obtained in Example 1, and the barium titanate and barium titanate were subjected to a dispersibility test. A mixed powder of dysprosium oxide was obtained. When this powder was observed with a scanning electron microscope, coarse particles of Dy compound (dysprosium oxide) were present.

The measurement / evaluation results of the above Examples and Comparative Examples are summarized in Table 1 below. The results of confirming the solubility of the complex powder obtained in each example and each powder obtained in the comparative example in pure water depending on whether or not 1 g or more is dissolved in 100 ml of pure water at 25 ° C are also shown. It is shown in Table 1.

As described above, the powder of the rare earth EDTA complex, which is a typical example of the rare earth aminopolycarboxylic acid complex, does not solidify when the D ₅₀ is 1 μm or more, and when the D ₅₀ is 1000 μm or less, it is a typical example of the ceramic powder. It was confirmed that the dispersibility in a certain barium titanate powder was good and that the aqueous solution did not form a precipitate in a wide pH range of 1 to 13.

Claims (9)

Aminopolycarboxylic acid complex powder of rare earth element having an average particle size of 1 μm or more and 1000 μm or less. A claim that 1 g of the aminopolycarboxylic acid complex powder is dissolved when mixed with 1 L of a nitrate aqueous solution having a pH of 1, and 1 g of the aminopolycarboxylic acid complex powder is dissolved when 1 g of an aqueous ammonia solution having a pH of 13 is mixed. The aminopolycarboxylic acid complex powder of the rare earth element according to 1. The aminopolycarboxylic acid complex powder of a rare earth element according to claim 1 or 2, which has a bulk density of 0.5 g / cm ³ or more and 1.2 g / cm ³ or less. The aminopolycarboxylic acid complex powder of a rare earth element according to any one of claims 1 to 3, wherein the aminopolycarboxylic acid complex powder of the rare earth element is EDTA (ethylenediaminetetraacetic acid) complex powder. An additive for a ceramic powder used for mixing with a ceramic powder, which comprises the aminopolycarboxylic acid complex powder of the rare earth element according to any one of claims 1 to 4. The additive according to claim 5, which is used for mixing with a powder made of a dielectric for a ceramic capacitor. The additive according to claim 6, which is used for mixing with a powder made of the dielectric having a perovskite structure. The additive according to any one of claims 5 to 7, which is used for mixing with barium titanate powder. A method for producing a ceramic powder containing a rare earth compound.
The particle surface of the ceramic powder is made of rare earth by mixing the aqueous solution of the aminopolycarboxylic acid complex powder of the rare earth element according to any one of claims 1 to 4 in water and the ceramic powder, and then removing the water. A method for producing a ceramic powder, which is coated with a compound.

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