JPH075305B2 - Method for producing low oxygen rare earth halide - Google Patents

Description

The present invention relates to a method for producing a low-oxygen halogenated rare earth. More particularly, it relates to a method for producing a halogenated rare earth having a low oxygen content, which is suitable for producing a low oxygen rare earth metal.

[Prior art and its problems]

Although rare earth metals have recently begun to be used as a storage film for magneto-optical disks, the oxygen concentration in the rare earth metal has a great influence on the performance as a storage film, and therefore a low oxygen concentration is strongly desired.

The rare earth metal is produced by thermally reducing the rare earth halide with a reducing agent such as calcium. As the method for producing the rare earth metal, (1) hydrogen halide is added to an aqueous solution of the rare earth. A method of acting (2) a method of mixing and heating a rare earth oxide and an acidic ammonium hydrogen halide is known (3) a method of firing the rare earth oxide in a hydrogen halide stream. Among these, the oxygen concentration in the rare earth fluoride obtained by the method (2) is the lowest, but it is still usually 1000 ppm or more. According to the present inventors, in the subsequent reduction process, the starting halogenated rare earth is rare. It has been found that it is not possible to reduce the oxygen in the soil and the produced rare earth metals, and to obtain low oxygen rare earth metals it is necessary to use low oxygen halogenated rare earths as a raw material.

[Means for solving problems]

As a result of intensive studies to obtain a low-oxygen halogenated rare earth, the present inventors have found that when the halogenated rare earth is treated by a specific means, its oxygen content can be significantly reduced. The present invention has also been completed.

That is, the present invention is intended to produce a low oxygen halogenated rare earth of great industrial value, the object is to melt the halogenated rare earth in a vacuum or in an inert gas atmosphere. To be achieved.

In the present invention, rare earth is yttrium and atomic number 57.
Shows a group consisting of ~ 71 elements.

As the rare earth halide to be used, rare earth fluoride, rare earth chloride or the like can be used. However, since rare earth chloride has a high deliquescent property, it absorbs moisture in the air to increase the oxygen content. It is preferable to use rare earth fluoride because it is inconvenient.
The method for producing the same is not limited, but a method in which a halogenated rare earth having a low oxygen content is obtained is preferable, and the rare earth oxide (2) of the method exemplified above is mixed with an ammonium acid halide. A method of heating by heating is preferable.

In the present invention, the rare earth halide is more preferably treated in vacuum or in an inert gas atmosphere.

Since the atmosphere of this treatment is preferably as low as oxygen, it is better that the degree of vacuum is lower in the case of treatment in a vacuum, but in view of equipment and operation, it is generally 10 ^-2 to 10 ^-8 Torr, preferably 10 ^-3. Selected from ~ 10 ^-6 Torr.

In the case of processing in an inert gas atmosphere, it is desirable that the inside of the system is once reduced to the above vacuum degree and then the inert gas is introduced. It is not impossible to replace the atmosphere with an inert gas without creating a high vacuum, but it is not possible to reduce the oxygen concentration to a desired value, or it takes an extremely long time and is not a good idea.

The pressure in the case of treatment in an inert gas atmosphere can be carried out in a wide range from the high vacuum to a pressure exceeding normal pressure, but is usually normal pressure to several mmHg, preferably normal pressure to several tens mmHg. Selected by range.

Examples of the inert gas include nitrogen, argon, and helium. However, since nitrogen forms a nitride with tantalum and the like, the material of the crucible may be limited, and helium is expensive, so argon is used. Is most preferred.

The temperature of the treatment is not less than the melting point of the rare earth halide, preferably not less than 20 ° C higher than the melting point, and there is no upper limit, but it is not a good idea that it is too high in terms of equipment material, operation, heat source cost, etc. , 200 ° C above melting point, preferably 1
A temperature up to 50 ° C. is preferable.

For heating, various conventional methods may be adopted, for example, tantalum,
Using a crucible such as molybdenum or graphite, it is carried out by electric heating, induction heating or the like, and the heating time is not particularly limited, but may be several tens of minutes or less after heating, usually 2 to 30 minutes, preferably 3 to It is sufficient to choose from the range of 20 minutes.

After the treatment in this way, it may be cooled at an arbitrary rate in the same atmosphere. The rare earth halide taken out after cooling is preferably handled in an inert gas atmosphere, but even if it is exposed to air for a short time, the oxygen content is not significantly affected.

〔Example〕

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 Terbium fluoride with an oxygen content of 1500 ppm (melting point 1172 ° C.) 2
The tantalum crucible was filled with kg, placed in a high-frequency vacuum heating furnace, heated to 1200 ° C. while maintaining the internal pressure at 2 × 10 ⁻⁴ Torr, melted, held for 5 minutes and then cooled in the same atmosphere. The oxygen content of the obtained terbium fluoride was 30 ppm.

Example 2 Gadolinium fluoride having an oxygen content of 1200 ppm (melting point 1231
3 kg) was filled in a graphite crucible, placed in a high-frequency vacuum furnace, the internal pressure was evacuated to 8 × 10 ^-5 Torr, and the pressure was restored to 710 mmHg with argon. Under this atmosphere, the temperature was increased to 1300 ° C., melting was performed, and the mixture was held for 15 minutes and then cooled in the same atmosphere. The obtained gadolinium fluoride has an oxygen content of 60 ppm.
Met.

〔The invention's effect〕

According to the present invention, a halogenated rare earth having an extremely low oxygen content can be obtained by an easy operation, so that the industrial value is great.

Claims (5)

[Claims] 1. A method for producing a low-oxygen halogenated rare earth, which comprises melting the halogenated rare earth in a vacuum or in an inert gas atmosphere. 2. The method for producing a low oxygen halogenated rare earth according to claim 1, wherein the degree of vacuum in the vacuum is 10 ^-2 to 10 ^-8 Torr. 3. The low-temperature atmosphere according to claim 1, wherein the inert gas atmosphere is an inert gas atmosphere prepared by introducing an inert gas after applying a vacuum of 10 ^-2 to 10 ^-8 Torr. Oxygen halide rare earth manufacturing method. 4. The melting temperature of the halogenated rare earth or a temperature 200 ° C. higher than the melting point of the rare earth halide.
The method for producing a low-oxygen halogenated rare earth according to any one of (3). 5. The method for producing a low oxygen halogenated rare earth according to any one of claims (1), (3) and (4), wherein the inert gas is argon, helium or nitrogen.