JP3280689B2 - Method for producing round rare earth oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a non-cohesive round crystalline rare earth oxide.

[0002]

2. Description of the Related Art Rare earth oxides are widely used as phosphor materials for color televisions, lighting lamps, etc., materials for functional ceramics, electronic materials, and the like. It is required to have a good particle size distribution, a high bulk density, and good filling properties, fluidity, reaction operability, and the like.

[0003] Conventional rare earth oxides have an irregular grain shape, and have a needle-like or rod-like shape with a low bulk density.
Since the particle size is also uneven and has a non-uniform and wide particle size distribution, when used for the above-mentioned applications, it is necessary to make the particle size uniform by a process such as classification and crushing. There is a problem such as mixing.

[0004] Further, as a conventional method for producing a rare earth oxide, a hydroxide obtained by reacting a mineral acid aqueous solution with caustic soda, aqueous ammonia, or the like, a mineral acid aqueous solution and oxalic acid, ammonium oxalate, or the like are reacted. A method is known in which rare earth oxalate particles obtained by reacting an aqueous solution of mineral acid or a mineral acid solution with ammonium carbonate, ammonium hydrogen carbonate, etc. are filtered, washed, dried, calcined, etc. to obtain a rare earth oxide. ing. However, there is a problem in that the grain shape of the rare earth oxide obtained by the method is non-uniform and the particle size distribution is not uniform.

[0005]

OBJECTS OF THE INVENTION It is an object of the present invention is to provide a method of <br/> manufacturing non-cohesive round crystalline rare earth oxide having a uniform particle size distribution.

[0006]

[Means for Solving the Problems]

According to the present invention, a rare earth oxalate compound obtained by reacting a rare earth ion with an oxalate ion is mixed with a rare earth carbonate compound obtained by reacting a rare earth ion with a carbonate ion. And a method for producing a non-aggregated crystalline rare earth oxide, characterized by calcining rare earth particles obtained by reacting and ripening.

Hereinafter, the present invention will be described in detail.

The non-agglomerated round crystalline rare earth oxide (hereinafter abbreviated as round rare earth oxide) obtained by the production method of the present invention has an average particle diameter of 0.1 to 10 μm, And those having a round shape.

[0010] In the present invention, non-aggregating means that individual particles are present independently and have substantially no aggregated portion. In addition, the round shape, the fluidity, there is a roundness to the extent that the bulk density is not impaired, elliptical shape, donut shape having a void portion in the center, a flat sphere, a disk shape, etc. It need not be strictly spherical. It is also desirable to use a mixture of the above shapes,
In particular, the elliptical shape desirably has a ratio of the major axis to the minor axis of preferably 2.0, particularly preferably more than 1.5.

The round rare earth oxide is yttrium,
The oxide is not particularly limited as long as it is an oxide of a lanthanoid having an atomic number of 57 to 71.

The average particle size of the round rare earth oxide is 0.1 to 10 μm, particularly preferably 0.5 to 5 μm on a volume basis (D50). The average particle size is 0.1 μm
If it is less than 10, the handling becomes difficult and the fluidity is poor. Also 10
If it exceeds μm, industrial production becomes difficult.

[0013] In the production method of the present invention , a rare earth oxalate compound obtained by reacting a rare earth ion with an oxalate ion is mixed with a rare earth carbonate compound obtained by reacting a rare earth ion with a carbonate ion. -It is characterized by aging and firing.

In the production method of the present invention, the rare earth ions used in preparing the rare earth oxalate compound and the rare earth carbonate compound are usually water-soluble rare earth salts such as chlorides, nitrates and sulfates of rare earth elements. It can be used as an aqueous solution, and specific examples thereof include preferably yttrium nitrate, europium nitrate, cerium nitrate, lanthanum nitrate, yttrium chloride, europium chloride, cerium chloride, and lanthanum chloride. You may mix and use. The concentration of the rare earth ion when reacting with oxalate ion and carbonate ion is not particularly limited. However, if the concentration is too low, the amount of the processing solution increases and the concentration is not suitable for industrial production.
It is desirable to use at a concentration of l / l or more, particularly preferably 0.1 to 1.0 mol / l.

The oxalate ion can be reacted as an aqueous oxalic acid solution, or an aqueous oxalate solution such as ammonium oxalate, sodium oxalate or potassium oxalate, and particularly preferably an aqueous oxalic acid solution or an aqueous ammonium oxalate solution. Etc. can be used. The concentration when reacting the oxalate ion with the rare earth ion is preferably 1.5 to
It is good to make it 3.0 times.

Further, the carbonate ion can be used as an aqueous solution of a carbonate such as ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like. The concentration at which the carbonate ions are reacted with the rare earth ions is preferably 3.0 to 6.0 times the molar ratio of the rare earth ions.

In the production method of the present invention, the rare earth oxalate compound and the rare earth carbonate compound are mixed and reacted and matured, for example, by preparing a rare earth salt aqueous solution as the rare earth ion and dividing the aqueous solution into two. Thereafter, an oxalic acid (salt) aqueous solution as the oxalate ion is added to one side to generate a rare earth oxalate compound, and preferably, the compound is filtered to form a cake. On the other hand, a carbonate aqueous solution as the carbonate ion is added to generate a rare earth carbonate compound in a slurry state, and then the obtained rare earth oxalate compound cake is added to the slurry, mixed and reacted.
It can be performed by a method of aging or the like. At this time, each time of adding oxalate ion and carbonate ion to the rare earth salt aqueous solution is preferably 1 to 120 minutes, particularly 2 to 60 minutes in order to make the particle size of the obtained rare earth oxide uniform. . If the addition time exceeds 120 minutes, ripening becomes difficult, which is not preferable. Further, to the prepared rare earth salt aqueous solution, a carbonate aqueous solution as a carbonate ion and an oxalate aqueous solution as an oxalate ion are added as a mixture or separately, and the rare earth oxalate compound and the rare earth carbonate compound are simultaneously added to the same system. , Followed by mixing, reaction and aging. At this time, the order of mixing the aqueous solution of oxalate as oxalate ion and the aqueous solution of carbonate as carbonate ion may be any order, but the aqueous solution of oxalate as oxalate ion is added to the aqueous solution of carbonate as carbonate ion. If added, the acid released during the formation of oxalate must be removed beforehand by neutralization or washing.

The mixing ratio of the rare earth carbonate compound and the rare earth oxalate compound is preferably from 1: 0.1 to 1: 2, more preferably from 1: 0.2 to 1, based on the molar ratio of each rare earth ion. It is desirable that the ratio be 1: 1. Outside the range of the mixing ratio, the salt with the higher mixing ratio remains unreacted, that is, unreacted rare earth carbonate compound when there are many rare earth carbonate compounds, and unreacted when there are many rare earth oxalate compounds. Is not preferable because the rare earth oxalate compound remains in each of the obtained rare earth oxides.

In order to mix the rare earth oxalate compound with the rare earth carbonate compound, it is desirable to stir by a stirrer or the like for preferably 30 minutes to 24 hours, particularly preferably 1 to 10 hours. The stirring time affects the particle size of the obtained rare earth oxide, and the longer the time, the smaller the particles are obtained.

The reaction and ripening can be carried out after completion of the stirring, preferably for 2 to 24 hours, particularly preferably for 5 to 15 hours, by allowing the particles to stand until they settle and become uniform. At this time, the rare earth oxalate compound and the rare earth carbonate compound are in a slurry state or the like, and the concentration of the mixed compound in the slurry is preferably 0.05 to 1 mol / l, particularly preferably 0.1 to 0 mol / l. 0.8 mol / l is desirable. If the concentration is less than 0.05 mol / l, a long time is required for the reaction, and if it exceeds 1 mol / l, uniform particles cannot be obtained.

In the production method of the present invention, after the reaction and aging, the sedimented particles are separated from the mother liquor and calcined to produce a high-purity, large-bulk-density, non-agglomerated rare earth oxide having a small average particle diameter. Obtainable. For the separation, known methods such as filtration, decantation, and centrifugation can be used, and further, washing and dehydration can be performed.
The calcination may be performed by heating the calcination temperature to a temperature equal to or higher than the decomposition temperature of the separated rare earth salt powder,
1200 ° C., particularly preferably 700 to 1100 ° C., and if the rate of temperature rise is too fast, rare earth particles may crack during the temperature rise, so it is preferably 300 ° C./hour or less, particularly preferably 100 to 200 ° C./hour; Further, the firing time is desirably 30 minutes to 2 hours. At this time, the average particle size and the particle size distribution of the obtained rare earth oxide can be controlled by changing the firing conditions.

[0022]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0023]

Example 1 300 ml of an aqueous solution of yttrium nitrate having a concentration of 0.3 mol / l and a pH of 2 was placed in a 1-liter tall beaker and stirred at room temperature with a stirrer to obtain a uniform aqueous solution of yttrium nitrate. Then, the concentration 0.8 mol
/ L oxalic acid aqueous solution (350 ml) using a metering pump,
It was added to the above yttrium nitrate aqueous solution over 30 minutes. The mixture was stirred for 20 minutes after completion of the addition to obtain an yttrium oxalate slurry. The slurry was filtered under reduced pressure using a Nutsche, and then acid-washed with ion-exchanged water to obtain an yttrium oxalate cake. .

On the other hand, 500 ml of an aqueous solution of yttrium nitrate having a concentration of 0.3 mol / l and a pH of 2 was placed in a glass beaker having a capacity of 2 liters and stirred at room temperature with a stirrer to obtain a uniform aqueous solution of yttrium nitrate. Concentration 1.25mol
540 ml of an aqueous solution of ammonium bicarbonate / l was added to the aqueous solution of yttrium nitrate over 20 minutes using a metering pump to obtain a yttrium carbonate slurry.

Next, the yttrium oxalate cake was added to the yttrium carbonate slurry and stirred for 2 hours. After stirring, the mixture was aged for 15 hours. After confirming that uniform particles had settled, the mixture was filtered under reduced pressure using a Nutsche and washed with ion-exchanged water to obtain a powder. Next, the obtained powder was placed in a magnetic crucible, heated to 900 ° C. at a heating rate of 200 ° C./hour, and calcined by holding for 1 hour to obtain a non-agglomerated yttrium oxide powder having an average particle size of 2.4 μm. 27 g were obtained. The obtained yttrium oxide powder is a non-agglomerated single particle, a round elliptical or disk-shaped particle having a uniform particle size, and the particle size distribution of the powder was measured by a microtrack method. Is shown in FIG.

[0026]

Example 2 A mixture of yttrium nitrate and europium nitrate having a concentration of 0.2 mol / l and a pH of 2 (Eu / Y molar ratio:
0.02) 500 ml was placed in a 1 liter tall beaker. On the other hand, 9.5 g of ammonium oxalate monohydrate and 32 g of ammonium bicarbonate were dissolved in ion-exchanged water to obtain a mixed solution of 400 ml. The mixed solution was added to the mixed solution of yttrium nitrate and europium nitrate for 20 minutes. To obtain a slurry.

The obtained slurry was treated in the same manner as in Example 1 to obtain 10 g of europium-containing yttrium oxide powder having an average particle size of 1.2 μm. The powder is a disk-shaped round particle, has no cohesion, is a single round rare earth oxide, and the particle size distribution measured by the microtrack method is shown in FIG.

[0028]

The non-agglomerated round rare earth oxide obtained by the production method of the present invention has a high purity and a uniform particle size, and has excellent fluidity. It is useful as a material for conductive ceramics.

Further, according to the production method of the present invention, a non-agglomerated rare earth oxide having a high purity, a uniform particle size and a particle size distribution, and an appropriate bulk density can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the particle size distribution of yttrium oxide obtained in Example 1.

FIG. 2 is a graph showing the particle size distribution of europium-containing yttrium oxide obtained in Example 2.

Continuation of the front page (56) References JP-A-3-1271118 (JP, A) JP-A-59-207839 (JP, A) JP-A-63-310706 (JP, A) JP-A-60-239323 (JP) JP-A-62-132708 (JP, A) JP-A-62-70204 (JP, A) JP-A-61-122121 (JP, A) European Patent Application Publication No. 462388 (EP, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C01F 17/00 C09K 11/77 CPB

Claims (1)

(57) [Claims] 1. A rare earth oxalate compound obtained by reacting a rare earth ion with an oxalate ion and a rare earth carbonate compound obtained by reacting a rare earth ion with a carbonate ion are mixed, and the mixture is reacted and matured. A method for producing a non-aggregated crystalline rare earth oxide, characterized in that the resulting rare earth particles are calcined.