JP2004083350A - Method for manufacturing rare earth oxide fine powder having 100 nm or less primary particle size, and rare earth oxide fine powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing rare earth oxide fine powder having ≤100 nm primary particle size without using an organic solvent. <P>SOLUTION: The method for manufacturing rare earth oxide fine powder having ≤100 nm primary particle size includes sequential processes of adding an aqueous solution containing rare earth ions to an alkali carbonate or alkali hydrogen carbonate aqueous solution to react to obtain precipitates, drying and pyrolyzing the obtained precipitates. The reaction conditions in the above method are controlled in such a manner that: the amount of carbonate ions in the alkali carbonate or alkali hydrogen carbonate aqueous solution is twice or more by the molar ratio as the amount of rare earth ions in the aqueous solution containing rare earth ions; the concentration of rare earth ions in the total amount of the aqueous solution containing rare earth ions and the alkali carbonate or alkali hydrogen carbonate aqueous solution is ≤1 mol/L; and the alkali carbonate or alkali hydrogen carbonate aqueous solution is heated to ≥40°C. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a rare earth oxide fine powder, and particularly to a method for producing a rare earth oxide fine powder having a small primary particle diameter.
[0002]
[Prior art]
Rare earth oxides are used in many fields as additives for ceramic-based electronic materials such as piezoelectrics and dielectrics, sintering aids for ceramics, abrasives, functional ceramic materials, phosphor materials, and the like. The rare earth oxide powder used in such a field needs to have a high degree of mixing because it is used by being mixed with other ceramic powders. Further, when used as an abrasive, it is required that the particle diameter is small and uniform in order to increase the surface accuracy. As a method for producing fine rare earth oxide fine powder used in such applications, for example, means described in JP-B-63-5332 and JP-A-4-310516 are known.
[0003]
[Problems to be solved by the invention]
However, these methods all use an organic solvent, so there is a problem in safety, and ripening of the precipitate, filtration, washing with water require a long time, and it is not easy to produce industrially. Was. Further, the products produced by the above-mentioned means have not been considered in terms of the degree of crushing. An object of the present invention is to provide a method for producing a rare earth oxide fine powder having a small primary particle size without using an organic solvent.
[0004]
[Means for Solving the Problems]
In the present invention, a process of adding and reacting an aqueous solution containing rare earth ions to an aqueous alkali carbonate or alkali bicarbonate solution to obtain a precipitate, and sequentially drying and thermally decomposing the obtained precipitate is used to produce a rare earth oxide fine powder. The reaction conditions in the method are such that the amount of carbonate ions in the aqueous solution of alkali carbonate or alkali hydrogen carbonate is twice or more in molar ratio to the amount of rare earth ions contained in the aqueous solution containing rare earth ions, and the aqueous solution containing rare earth ions and the alkali carbonate Alternatively, the primary particle diameter is determined by assuming that the concentration of rare earth ions in the total amount of the aqueous alkali hydrogen carbonate solution is 1 mol / l or less and the temperature of the aqueous alkali carbonate or alkali hydrogen carbonate solution is heated to 40 ° C. or more. Produces a rare earth oxide fine powder of 100 nm or less. Among the products manufactured by the above method, the rare earth oxide fine powder having a primary particle diameter of 100 nm or less and a crushing degree of 70% or more has a good mixing degree with other ceramic powders and when used as an abrasive. Surface accuracy can be improved.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The rare-earth oxide fine powder produced in the present invention has a maximum primary particle diameter of 100 nm or less that can be identified when observed with a scanning electron microscope or a transmission electron microscope. Such fine powders are liable to agglomerate, and the lower limit of the particle size measurement range cannot be measured accurately because the lower limit of the particle size measurement range is close to the primary particle size with a commonly used laser light diffraction type particle sizer. It cannot be distinguished from the value of the particle size or the value of the aggregated particle size. Therefore, in the present invention, the primary particle diameter (so-called crystallite diameter) is measured using a scanning electron microscope or a transmission electron microscope.
[0006]
"Crushing degree" refers to the degree to which the aggregates are easily broken. For the measurement, a laser Doppler type particle size analyzer capable of measuring the particle diameter of aggregated particles to several nm in principle is used, and the number of aggregated particles observed in the observation visual field is 10 times or less of the average primary particle diameter. The degree of crushing was defined as the ratio (%) of the number of aggregated particles having an aggregated particle diameter.
[0007]
In the present invention, in order to produce the rare earth oxide fine powder, an aqueous solution containing rare earth ions is added and reacted in an aqueous alkali carbonate or alkali hydrogen carbonate solution to obtain a precipitate, and the obtained precipitate is dried and heated. A decomposition method is adopted, and the reaction conditions at that time are as shown below.
[0008]
First, when an aqueous solution containing a rare earth ion is added to an aqueous alkali carbonate solution or an aqueous alkali hydrogen carbonate solution (hereinafter simply referred to as an aqueous alkali solution) to cause a reaction, the amount of carbonate ions (converted as CO ₃ ) of the aqueous alkali solution is an aqueous solution containing the rare earth ion. In a molar ratio of at least 2 times, preferably 3 to 6 times, relative to the amount of rare earth ions contained in the above.
[0009]
Carbonate ions have the effect of suppressing the aggregation of primary particles by the CO ₂ foaming action during the reaction, but if the molar ratio is less than 2, the effect is not sufficient, and the resulting precipitate is dried and thermally decomposed, When crushed, the ratio of remaining aggregated particles (secondary particles) increases. On the other hand, even if the molar ratio is 6 times or more, the improvement of the above-mentioned suppression effect is not observed, but rather increases the cost.
[0010]
The concentration of alkali carbonate or alkali hydrogen carbonate is not particularly limited as long as it is equal to or lower than the solubility. As the alkali carbonate or alkali hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, ammonium carbonate, ammonium hydrogen carbonate, or the like can be used. Among them, the ammonium salt has an advantage that residual impurities when the generated precipitate is dried and thermally decomposed are easily removed when heated.
[0011]
As the rare earth element, yttrium or a lanthanoid having an atomic number of 57 to 71 can be used, and these can be used alone or in combination of two or more. As the rare earth aqueous solution, an aqueous solution of a nitrate, a hydrochloride, a sulfate or the like can be used, and the concentration thereof is not particularly limited as long as it is equal to or lower than the solubility.
[0012]
An aqueous solution containing rare earth ions is gradually added to the alkaline aqueous solution to cause a reaction, thereby forming a rare earth compound colloid. At this time, the amount of the rare earth ions is adjusted to a concentration of 1 mol / l or less, preferably 0.6 mol / l or less, based on the total amount of the above-mentioned alkaline aqueous solution and the aqueous solution containing the rare earth ions. When the concentration of the rare earth ion is 1 mol / l or more, a rare earth oxide powder having primary particles of 100 nm or less cannot be obtained. In addition, the rare earth compound colloid generated during the reaction is strongly agglomerated, and the degree of crushing is reduced.
[0013]
The reaction temperature is 40 ° C. or higher, preferably 50 to 90 ° C. Specifically, an aqueous solution containing rare earth ions is added to the alkaline aqueous solution heated to the above temperature. When the reaction temperature is lower than 40 ° C., the CO ₂ foaming action due to the decomposition of alkali carbonate and alkali hydrogencarbonate is not sufficient, and the effect of suppressing the aggregation of the primary particles decreases, and the degree of crushing decreases.
[0014]
The rate of addition of the aqueous solution containing rare earth ions is not particularly limited. The lower the speed, the smaller the particle size of the obtained colloid. However, if the speed is too low, productivity is impaired. Therefore, it is preferable to add while controlling the addition rate using a metering pump or the like according to the target particle diameter. For example, an aqueous solution containing rare earth ions is preferably added at a rate of 7 to 0.5% / min of the total amount.
[0015]
As a result of the above reaction, a precipitate having a primary particle diameter of at most 100 nm is obtained as a reaction product. This is dried and thermally decomposed into rare earth oxide fine powder.
[0016]
【Example】
[Example 1]
200 ml (solution A) of a neodymium chloride solution having a concentration of 1.0 mol / l and 800 ml (solution B) of an ammonium bicarbonate solution adjusted so that the carbonate ion concentration was four times the neodymium ion concentration in a molar ratio were prepared. The concentration of the rare earth ion (Nd ²⁺ ) in the total amount of both is 0.20 mol / l.
[0017]
The solution A was added to the solution B maintained at a temperature of 70 ° C. at a rate of 5% / min of the total amount thereof using a metering pump to obtain a precipitate. The obtained precipitate was filtered, washed and dried, and then heated at 800 ° C. for 1 hour to obtain neodymium oxide powder. After the powder was pulverized with a hammer mill, the particle diameter was observed with a scanning electron microscope. As a result, it was confirmed that the powder was neodymium oxide powder having a maximum primary particle diameter of about 80 nm and a degree of crushing of 90% or more.
[0018]
[Example 2]
Concentration 2. 800 ml of an ammonium carbonate solution (solution B) was prepared in which the concentration of carbonate ions was adjusted to be 6 times the holmium ion concentration at a molar ratio of 200 ml of an Omol / l holmium nitrate solution (solution A). The concentration of the rare earth ion (Ho ²⁺ ) in the total amount of both is 0.40 mol / l.
[0019]
Solution A was added to Solution B at a temperature adjusted to 85 ° C. at a rate of 0.7% / min of the total amount thereof using a metering pump to obtain a precipitate. The obtained precipitate was filtered, washed and dried, and then heated at 600 ° C. for 1 hour to produce holmium oxide powder. After the powder was pulverized with a hammer mill, the particle diameter was observed with a scanning electron microscope. As a result, it was confirmed that the powder was a holmium oxide powder having a maximum primary particle diameter of about 70 nm and a degree of crushing of 80%.
[0020]
[Example 3]
A 200 ml (solution A) cerium chloride solution having a concentration of 1.0 mol / l and an 800 ml (solution B) ammonium bicarbonate solution containing a carbonate ion concentration at a molar ratio four times that of the cerium ion concentration were prepared. The concentration of the rare earth ion (Ce ²⁺ ) in the total amount of both is 0.20 mol / l.
[0021]
The solution A was added to the solution B heated and maintained at 60 ° C. at a rate of 1% / min of the total amount thereof using a metering pump to obtain a precipitate. After filtering, washing and drying the obtained precipitate, it was heated at 200 ° C. for 1 hour to produce cerium oxide powder. After the powder was pulverized with a hammer mill, the particle diameter was observed with a transmission electron microscope. As a result, it was confirmed that the powder was a cerium oxide powder having a maximum primary particle diameter of about 70 nm and a degree of crushing of 70%.
[0022]
[Comparative Example 1]
Concentration 1. 200 ml of an Omol / l neodymium chloride solution (solution A) and 800 ml of an ammonium bicarbonate solution (solution B) adjusted to a molar ratio of 1.5 times the neodymium ion concentration were prepared. The concentration of the rare earth ion (Ce ²⁺ ) in the total amount of both is 0.20 mol / l.
[0023]
Solution A was added to Solution B heated and maintained at 70 ° C. at a rate of 5% / min of the total amount thereof using a metering pump to obtain a precipitate. The precipitate was filtered, washed and dried, and then heated at 800 ° C. for 1 hour to produce neodymium oxide powder. After the powder was pulverized with a hammer mill, the particle diameter was observed with a scanning electron microscope of 10,000 times or more. As a result, the powder was a neodymium oxide powder having a maximum primary particle diameter of about 80 nm and a degree of crushing of 50%.
[0024]
[Comparative Example 2]
Concentration 2. 200 ml of an Omol / l holmium nitrate solution (solution A) and 700 ml of an ammonium carbonate solution (solution B) adjusted to a molar ratio of 6 times the holmium ion concentration were prepared. The concentration of the rare earth ion (Ho ²⁺ ) in the total amount of both is 0.44 mol / l.
[0025]
Solution A was added to Solution B heated and maintained at 30 ° C. at a rate of 0.7% / min of the total amount thereof using a metering pump to obtain a precipitate. This precipitate was filtered, washed and dried, and then heated at 600 ° C. for 1 hour to produce holmium oxide powder. After the powder was pulverized with a hammer mill, the particle diameter was observed with a scanning electron microscope. As a result, it was confirmed that the powder was a holmium oxide powder having a maximum primary particle diameter of about 70 nm and a degree of crushing of about 20%. .
[0026]
[Comparative Example 3]
A holmium nitrate solution having a concentration of 1.5 mol / l (1000 ml, solution A) and an ammonium bicarbonate solution (400 ml, solution B) adjusted to a molar ratio of three times the holmium ion concentration were prepared. The concentration of the rare earth ion (Ho ²⁺ ) in the total amount of both is 1.07 mol / l.
[0027]
Solution A was added to Solution B heated and maintained at 70 ° C. at a rate of 5% / min of the total amount thereof using a metering pump to obtain a precipitate. This precipitate was filtered, washed and dried, and then heated at 600 ° C. for 1 hour to produce holmium oxide powder. After the powder was pulverized by a hammer mill, the particle diameter was observed with a scanning electron microscope. As a result, it was confirmed that the powder was a holmium oxide powder having a maximum primary particle diameter of about 300 nm and a degree of crushing of 90% or more. .
[0028]
【The invention's effect】
The rare earth oxide fine powder obtained by the production method of the present invention has a primary particle diameter of 100 μm or less and is excellent in dispersibility, so that additives for ceramic-based electronic materials such as piezoelectrics and dielectrics, When used as a binding aid, a functional ceramics material, or a phosphor material, it is useful because it has effects such as a very good degree of mixing.

Claims (2)

Reaction conditions in a method for producing a rare-earth oxide fine powder in which a precipitate is obtained by adding and reacting an aqueous solution containing a rare-earth ion into an aqueous solution of an alkali carbonate or an alkali hydrogen carbonate, and sequentially drying and thermally decomposing the obtained precipitate. To
The amount of carbonate ions in the aqueous alkali carbonate or alkali hydrogen carbonate solution is twice or more in molar ratio to the amount of rare earth ions contained in the aqueous solution containing rare earth ions,
The concentration of rare earth ions in the total amount of the aqueous solution containing rare earth ions and the aqueous alkali carbonate or alkali hydrogen carbonate solution is 1 mol / l or less;
And a method of producing a rare earth oxide fine powder having a primary particle diameter of 100 nm or less, wherein the temperature of the alkali carbonate or alkali hydrogen carbonate aqueous solution is heated to 40 ° C. or higher. Rare earth oxide fine powder having a primary particle diameter of 100 nm or less and a degree of crushing of 70% or more.