JP3877922B2 - Method for producing rare earth compound - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing rare earth compound fine particles useful as a raw material for sintered rare earth elements, a sintering aid for ceramics, and a phosphor raw material.
[0002]
[Prior art]
As a method for producing rare earth compound fine particles, conventionally, an aqueous solution containing rare earth element ions and urea is heated to obtain a spherical basic carbonate, which is fired to have an average particle size of 0.2 to 1 μm. It is known that spherical rare earth element oxides can be obtained (see JP-A-10-139426).
Japanese Patent Application Laid-Open No. 10-139427 discloses a method for producing smaller particles having an average particle size of 0.1 to 0.3 μm.
[0003]
[Problems to be solved by the invention]
However, in order to produce particles having a small average particle diameter by the method described in the above publication, a container for diluting the reaction aqueous solution is required in addition to the precipitation reaction container, and the process is complicated.
The present invention provides a simple method for producing spherical fine particles of rare earth element basic carbonates and oxides useful as rare earth element sintered bodies, ceramic sintering aids, and phosphor materials. is there.
[0004]
[Means for Solving the Problems]
According to the present invention, a spherical solution composed of a rare earth element basic carbonate having a particle size of less than 0.3 μm is observed by an electron microscope by heating a mixed solution of a rare earth element mineral salt, hydrogen peroxide and urea. It was found that fine particles were obtained and fired to obtain spherical fine particles composed of oxides of rare earth elements, and the present invention was completed.
The method for producing a rare earth compound of the present invention includes one or more rare earth element ions, hydrogen peroxide and urea in the group consisting of Y, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc. It is characterized in that an aqueous solution containing a rare earth element is obtained by heating an aqueous solution containing 80 to the boiling point of the aqueous solution.
[0005]
Further, in addition to the rare earth element ions, one or more rare earth element ions of the group consisting of Ce, Pr, Sm, and Eu can be added to obtain a rare earth element basic carbonate. In this case, the amount of rare earth element ions added is preferably 20 mol% or less with respect to the total rare earth.
The rare earth element oxide is obtained by firing this basic carbonate.
[0006]
The hydrogen peroxide may be added to the aqueous solution at any time before the reaction between ammonia and carbonic acid produced by hydrolysis of urea occurs, but in particular, part of the hydrogen peroxide is decomposed during heating. For example, it is preferable to add the aqueous solution after heating it to some extent.
The timing of adding urea may be added when preparing an aqueous solution containing rare earth element ions or adding hydrogen peroxide. Alternatively, it may be added in two portions at the time of preparing an aqueous solution containing rare earth element ions and at the time of adding hydrogen peroxide.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
An aqueous solution containing a rare earth element mineral acid salt is heated to 80 ° C. to the boiling point of the aqueous solution for 0.5 to 5 hours, added with hydrogen peroxide and urea, and further heated to form a rare earth element basic carbonate. Spherical particles are deposited. Subsequently, the precipitated rare earth element basic carbonate is subjected to solid-liquid separation to obtain spherical particles of the rare earth element basic carbonate. Spherical fine particles of rare earth element oxide can be obtained by further firing the spherical particles of the basic carbonate in air or in an oxidizing atmosphere.
[0008]
Observation of the rare earth element oxide fine particles thus obtained with an electron microscope reveals that spherical fine particles of less than about 0.3 μm are observed, and that fine particles are precipitated by the addition of hydrogen peroxide.
Further, when a rare earth element such as Ce, Pr, Sm and Eu is used as a main component, a spherical basic carbonate cannot be obtained, but Y, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb When a rare earth element such as, Lu, or Sc is used as a main component and Ce, Pr, Sm, or Eu is added as an additive element, a spherical basic carbonate can be obtained.
[0009]
The precipitation reaction conditions for the rare earth element basic carbonate will be described in more detail.
As the water-soluble rare earth element mineral salt, chloride salt, nitrate salt, sulfate salt and the like are used, but nitrate salt or chloride salt is preferable in order not to leave an impurity root in the final product.
The concentration of the mineral acid salt is preferably 0.01 to 0.08 mol / liter (mol / L). If it is less than 0.01 mol / liter, the productivity is remarkably inferior. Aggregation of salts occurs, making it difficult to obtain monodispersed spherical particles.
[0010]
It is preferable to add hydrogen peroxide at a molar ratio of 1/100 to 30/100 with respect to the rare earth element ion concentration. If the amount of hydrogen peroxide (H ₂ O ₂ ) added is [H ₂ O ₂ ] / [RE] ≧ 1/100 in terms of molar concentration relative to the number of moles of all rare earth elements (RE), the particle size is reduced. There is an effect, and in particular [H ₂ O ₂ ] / [RE] ≧ 5/100, a rare earth element basic carbonate having a diameter of less than 0.3 μm as observed with an electron microscope can be obtained. The larger the amount of hydrogen peroxide added, the smaller the rare earth element basic carbonate particles obtained. However, when the amount added is too large, the particles become too small and agglomeration occurs, resulting in monodispersity. Therefore, the molar ratio of the rare earth element ions is preferably 30/100 or less.
[0011]
The amount of urea added is preferably about 3 to 50 times the molar concentration of the rare earth element.
The precipitate obtained by heating is a basic carbonate of a rare earth element, and when observed with an electron microscope, fine spherical particles are observed.
When the obtained rare earth element basic carbonate is fired in air or in an oxidizing atmosphere at a temperature not lower than 600 ° C. and not higher than the melting point of the carbonate, preferably for 1 to 10 hours, an oxide of the rare earth element is obtained, such as an electron microscope When observed, the spherical fine particles of rare earth elements maintaining the basic carbonate shape are observed.
[0012]
【Example】
Hereinafter, embodiments of the present invention will be specifically described with reference to examples and comparative examples.
Example 1
Ten liters of an yttrium nitrate aqueous solution having an yttrium ion concentration of 0.05 mol / liter was heated to 95 ° C. Hydrogen peroxide is added to this aqueous solution so that the hydrogen peroxide concentration becomes 0.01 mol / liter, and urea is further added so that this concentration becomes 0.6 mol / liter, and the mixture is heated at 95 ° C. for 60 minutes. Upon heating, basic yttrium carbonate was obtained. The precipitated solid was solid-liquid separated with a Buchner funnel and calcined at 700 ° C. for 2 hours. As shown in FIG. 1, the average particle size was about 0.1 μm, and the yttrium oxide had a very small particle size. Of spherical particles were obtained.
[0013]
(Example 2)
Ten liters of an aqueous solution having an yttrium ion concentration of 0.05 mol / liter and a cerium ion concentration of 0.005 mol / liter as an additive element was heated to 95 ° C. Hydrogen peroxide was added to this aqueous solution so that the hydrogen peroxide concentration was 0.005 mol / liter, and urea was further added so that the urea concentration was 0.6 mol / liter. Heated.
The precipitated solid was solid-liquid separated with a Buchner funnel and dried at 130 ° C. for 1 hour. As shown in FIG. 2, the basicity of the rare earth element with a very small yttrium / cerium coprecipitation with a particle size of about 0.1 μm was obtained. Carbonate spherical particles were obtained.
[0014]
(Example 3)
In Example 1, except that an ytterbium nitrate aqueous solution was used in place of the yttrium nitrate aqueous solution, the same treatment was performed. As in Example 1, a spherical ytterbium having an average particle size of about 0.1 μm and a uniform particle size was obtained. An oxide was obtained.
[0015]
(Comparative Example 1)
Ten liters of an yttrium nitrate aqueous solution having an yttrium ion concentration of 0.05 mol / liter was heated to 95 ° C. Urea was added to this aqueous solution so that the urea concentration was 0.6 mol / liter, and the solution was heated at 95 ° C. for 60 minutes. The precipitated solid was subjected to solid-liquid separation with a Buchner funnel and calcined at 700 ° C. for 2 hours. As a result, spherical particles of yttrium oxide having a particle size of 0.3 μm or more as shown in FIG. 3 were obtained.
[0016]
【The invention's effect】
Rare earth element basic carbonate particles and oxide spherical fine particles useful as raw materials for the production of sintered rare earth element oxides, ceramic sintering aids, and phosphor raw materials can be produced in a simple process. Moreover, it can be manufactured economically.
[Brief description of the drawings]
FIG. 1 is a view of rare earth element oxide spherical fine particles obtained by Example 1 of the present invention, observed with an electron microscope.
FIG. 2 is a view of spherical particles of a rare earth element basic carbonate obtained by Example 2 of the present invention, observed with an electron microscope.
3 is a view obtained by observing spherical particles of a rare earth element oxide obtained in Comparative Example 1 with an electron microscope. FIG.

Claims (3)

  An aqueous solution containing one or more rare earth ions, hydrogen peroxide, and urea from the group consisting of Y, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc A method for producing a rare earth compound, which is heated to a boiling point to obtain a basic carbonate of a rare earth element. In addition to the rare earth element ion, Ce, Pr, Sm, one or more rare earth element ion selected from the group consisting of Eu, with the following added pressure 20 mol% based on the total rare earth, basic carbonates of rare earth elements The method for producing a rare earth compound according to claim 1, wherein a salt is obtained.   The method for producing a rare earth compound according to claim 1 or 2, wherein the basic carbonate is fired to obtain a rare earth element oxide.

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