JPH0233654B2 - TA2O5 * NH2ORYUSHINOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing so-called monodisperse Ta ₂ O ₅ .nH ₂ O particles having a uniform particle size distribution and good dispersibility. Ta ₂ O ₅ is used as a wear-resistant, heat-resistant, and corrosion-resistant thin film, as well as LiTaO ₃ single crystal, Ba (Zn Ta)
It is used as a raw material for O ₃ ceramics, and LiTaO ₃ single crystals are used for optical memories, surface wave filters, high-frequency oscillation devices, etc., and Ba (Zn Ta) O ₃ ceramics are used for piezoelectric ignition elements, ultrasonic vibrators, ceramic filter elements, etc. used. When making a Ta ₂ O ₅ thin film, film uniformity, film thickness,
In terms of filling and adhesion properties, tantalum single crystals have high purity and easy melting properties, ceramics have high purity and easy sintering properties, and optical glasses have high melting properties. Uniformity of particle size distribution is required respectively. The physical properties commonly required of Ta ₂ O ₅ particles for these uses are uniform particle size, fine particles, good dispersibility, high purity, and spherical shape in order to obtain high filling properties. Conventional technology Conventional methods for producing Ta ₂ O ₅ particles include (1) metal
How to burn Ta in air. (2) A method of producing tantalic acid by thermal dehydration is known.
Although the Ta ₂ O ₅ particles obtained by these methods have relatively high purity, they are agglomerated particles with non-uniform particle shapes;
It is hard to say that it is optimal for the above-mentioned uses. In particular, method (2) above only yields a gelatinous precipitate. Purpose of the Invention The present invention was made to overcome the drawbacks of the conventional method, and its purpose is to provide a raw material for spherical Ta ₂ O ₅ particles with uniform particle size, fine particles, good dispersibility, and high purity.
The present invention provides a method for producing Ta ₂ O ₅ .nH ₂ O particles. Structure of the Invention As a result of research to achieve the above object, the present inventor has
When tantalum alkoxide such as Ta(OC ₂ H ₅ ) ₅ is dissolved in a non-aqueous solvent such as ethanol, a predetermined amount of water and a compound that releases a hydroxyl group in the presence of water, so-called Brostedt's base, are mixed and heated to hydrolyze it. High purity Ta ₂ O ₅ .
It has been found that nH ₂ O particles can be easily produced and obtained. The present invention was completed based on this knowledge. The gist of the present invention is to provide a compound that releases a hydroxyl group in the presence of water to a non-aqueous solution of tantalum alkoxide,
The present invention provides a method for producing Ta ₂ O ₅ .nH ₂ O particles, which comprises mixing and hydrolyzing a so-called Brosted base catalyst and water. The tantalum alkoxides used in the method of _the present invention include Ta( _OCH3 ) ₅ , Ta( _OC2H5 ) ₅ ,
Examples include Ta(n-OCH ₃ H ₇ ) ₅ and Ta(n-OC ₄ O ₉ ). Catalysts include NaOH, KOH, Ca(OH) ₂ , _NH3 , which are compounds that release hydroxyl groups in the presence of water.
Examples include (NH ₂ ) ₂ CO, C ₂ H ₅ NH ₂ , (C ₂ H ₅ ) ₂ NH, and the like. Although the hydrolysis reaction proceeds without a catalyst, the rate is extremely slow, and since the pH of the reaction system cannot be adjusted, the particle size cannot be adjusted arbitrarily, so a catalyst is necessary. Among the above catalysts, when a strong base such as NaOH, KOH, Ca(OH) ₂ or the like is used, the appropriate range of the amount added to obtain an appropriate PH range and an appropriate reaction rate is narrow. This point = a weak base with NH group or _-NH2 group, e.g.
_{C2H5NH2 , ( NH2} ) _{2CO , C3H7NH2 ,}
When (C ₂ H ₅ ) ₂ NH or the like is used, the above adjustment is relatively easy. However, =NH group or -NH ₂
Some compounds with groups adsorb onto the particle surface and require cleaning after reaction. In this respect, if NH ₃ is used, cleaning is not necessary,
It is preferable because it is easy to handle. The lower limit of the amount of catalyst added is determined by the pH of the reaction solution. For example, when ethanol is used as a solvent, the pH is maintained at 5.5 or higher, preferably 7 or higher. When the pH is lower than 5.5, the generated particles tend to coagulate. This is thought to be because the pH of the reaction system approaches the equipotential point of Ta ₂ O ₅ .nH ₂ O. The upper limit of the amount of catalyst added is determined by the reaction rate. If the amount is too large, the reaction will be extremely rapid, and there will be a strong tendency for hydrolysis and particle formation to proceed in parallel, making it easier for particles to coagulate. PH is used as a measure to prevent such coagulation. PH of reaction system
changes with the progress of hydrolysis, but it is desirable to allow particle formation to occur after the pH has stopped changing. For example, when Ta(OC ₂ H ₅ ) ₅ is hydrolyzed using ammonia as a catalyst, the mixing amount of NH ₃ is NH ₃ /Ta.
The (OC ₂ H ₅ ) ₅ molar ratio is preferably in the range of 0.01 to 1. When this ratio is less than 0.01, the pH is too low and particles tend to aggregate. If it exceeds 1, the reaction becomes extremely fast and particles tend to aggregate, making it difficult to obtain so-called particles. If the amount of water added is too small, the yield will be poor; if it is too large, a three-dimensional network structure will develop, making it difficult to obtain so-called particles. For example, the amount of water added in the hydrolysis of Ta(OC ₂ H ₅ ) ₅ using ammonia as a catalyst is preferably 3 to 50 in molar ratio to tantalum alkoxide. When the molar ratio is less than 3, the reaction rate is extremely slow and the yield of the product is poor, and when the molar ratio exceeds 50, a three-dimensional structure tends to develop, which is not preferable. Note that when preparing the reaction solution, it is preferable to make the solution a homogeneous solution, since if the solution becomes non-uniform, aggregated particles are likely to be produced and monodisperse particles are difficult to obtain. To this end, it is desirable to prepare and mix a tantalum alkoxide solution, a solution containing water, and a catalyst in advance, rather than adding each component to the solvent one after another. The reaction temperature is tantalum alkoxide, H ₂ O,
It must be selected according to each concentration of catalyst,
The temperature is desirably 30° C. or higher in order to ensure that particles grow in a short time after particle formation and do not aggregate. However, extremely high temperatures are not required. Moreover, no processing operation is required. The particle size of the obtained Ta ₂ O ₅ .nH ₂ O can be arbitrarily adjusted by adjusting the amount of catalyst and water added. for example
Ta (OC ₂ H ₅ ) ₅ ethanol solution 0.015 mol/Kg
In a system consisting of NH ₃ 0.0018 mol/Kg, the amount of H ₂ O is
By changing the amount from 0.059 to 0.48 mol/Kg, the particle size can be changed from 0.05 to 0.4 μm. In addition, in a system consisting of Ta(OC ₂ H ₅ ) ₅ ethanol solution 0.015 mol/Kg and H ₂ O 0.09 mol/Kg,
By changing the amount of NH ₃ from 0.00041 to 0.0063 mol/Kg, the particle size can be changed from 0.1 to 0.75 μm. The concentration of tantalum alkoxide has a certain upper limit in order to prevent particle agglomeration; for example,
For Ta(OC ₂ H ₅ ) ₅ , it is preferably 0.1 mol/Kg or less. The produced particles were found to be amorphous Ta ₂ O ₅ .nH ₂ O by X-ray diffraction analysis and thermal analysis. Even when these particles were crystallized at about 800°C, the shrinkage was extremely small. Example 1 Ta (OC ₂ H ₅ ) ₅ ethanol solution and NH ₃ , H ₂ O mixed ethanol solution were mixed, and the concentration after mixing was [Ta
(OC ₂ H ₅ ) ₅ ]=0.015mol/Kg, [ _H2O ]=0.09mol/
Adjusted to be Kg. NH ₃ concentration is NH ₃ /
Ta(OC ₂ H ₅ ) ₅ molar ratio is 0.027, 0.055, 0.098, 0.20,
Adjusted to be 0.42. Hydrolysis at 50℃
As a result of carrying out the test for a certain period of time, spherical monodisperse particles having the particle diameters shown in Table 1 were obtained.

[Table] Example 2 Ta (OC ₂ H ₅ ) ₅ ethanol solution and NH ₃ , H ₂ O mixed ethanol solution were mixed, and the concentration after mixing was [Ta
(OC ₂ H ₅ ) ₅ ]=0.015mol/Kg, [NH ₃ ]=
It was adjusted to 0.0018 mol/Kg. The H ₂ O concentration is H ₂ O/Ta (OC ₂ H ₅ ) ₅ molar ratio of 3.9, 7.8, 15.2,
Adjusted to be 32.2. Hydrolysis at 50℃
Time (1 day only when H ₂ O/Ta (OC ₂ H ₅ ) ₅ = 3.9)
As a result, spherical monodisperse particles having the particle diameters shown in Table 2 were obtained. A scanning electron micrograph of the particles obtained under the condition of H ₂ O/Ta(OC ₂ H ₅ ) ₅ =3.9 is shown in FIG. 1.

[Table] Example 3 Ta (OC ₂ H ₅ ) ₅ ethanol solution and NH ₃ , H ₂ O mixed ethanol solution were mixed, and the concentration after mixing was [Ta
(OC ₂ H ₅ ) ₅ ]=0.015mol/Kg, [NH ₃ ]=
It was adjusted to 0.0008 mol/Kg. The H ₂ O concentration was adjusted so that the H ₂ O/Ta (OC ₂ H ₅ ) ₅ molar ratio was 7.2 and 14.5. As a result of hydrolysis at 0.5° C. for 1 hour, spherical monodisperse particles having the particle sizes shown in Table 3 were obtained. Table 3 H ₂ O/Ta (OC ₂ H ₅ ) ₅ molar ratio 7.2 14.5 Particle size (μm) 0.75 0.35 Example 4 Mixing Ta (OC ₂ H ₅ ) ₅ ethanol solution and NH ₃ and H ₂ O mixed ethanol solution H ₂ O/Ta after mixing
(OC ₂ H ₅ ) ₅ molar ratio was adjusted to 5. As a result of photolysis at 50° C. for 1 hour, spherical monodisperse particles having the particle sizes shown in Table 3 were obtained. Table 4 [Ta (OC ₂ H ₅ ) ₅ ] 0.015 0.03 0.045 Particle size (μm) 0.2 0.3 0.35 Example 5 Ta (OC ₂ H ₅ ) ₅ ethanol solution and C ₂ H ₅ NH ₂ ,
Mix the H ₂ O mixed ethanol solution, and after mixing [Ta(OC ₂ H ₅ ) ₅ ] = 0.45 mol/Kg, [C ₂ H ₅ NH ₂ ] =
0.045mol/Kg, [H ₂ O] = 0.36mol/Kg, 20℃
As a result of hydrolysis for 1 hour, the particle size was 0.32 μm.
spherical monodisperse particles were obtained. Example 6 Ta(OC ₂ H ₅ ) ₅ ethanol solution and (NH ₂ ) ₂ CO,
Mix the H ₂ O mixed ethanol solution, and after mixing [Ta(OC ₂ H ₅ ) ₅ ] = 0.015 mol/Kg, [(NH ₂ ) ₂ CO] =
0.048mol/Kg, [H ₂ O] = 0.13mol/Kg, 50℃
As a result of hydrolysis for 2 hours, 0.26 μm spherical monodisperse particles were obtained. Effects of the Invention According to the method of the present invention, Ta ₂ O ₅ .
nH ₂ O can be obtained, and the particle size can also be arbitrarily adjusted within a wide range to achieve excellent effects.

[Brief explanation of drawings]

FIG. 1 is a scanning electron micrograph of particles obtained by the method of the present invention.

Claims (1)

[Claims] 1. Ta ₂ O _{5 .nH} , which is characterized in that a non-aqueous solution of tantalum alkoxide is hydrolyzed by mixing a compound that releases a hydroxyl group in the presence of water, a so-called Brosted base catalyst, and water. ₂ Method for producing O particles. 2. The method for producing Ta ₂ O ₅ .nH ₂ O particles according to claim 1, wherein the catalyst is NH ₃ and its concentration is in the range of 0.01 to 1 in molar ratio of NH ₃ /tantalum alkoxide. 3 H ₂ O/tantalum alkoxide has a molar ratio of 3
~50% according to claim 1
Method for producing Ta ₂ O ₅ nH ₂ O particles. 4 Ta ₂ O ₅ according to claim 1, wherein the catalyst is a compound having an =NH group or -NH ₂ group.
Method for producing _nH2O particles.