JP4916203B2 - Purification method of gallium - Google Patents

Description

  The present invention relates to a method for purifying gallium, and more particularly to a method for purifying gallium containing a metal element such as iron, nickel, potassium, calcium, or silicon as an impurity.

  Gallium (Ga) is a metal element used as a raw material for compound semiconductors such as GaAs and GaP. In order to use it as a raw material for such compound semiconductors, the purity of Ga is 99.9999% (6N). It is necessary to do more. Since Ga does not exist as a single ore, it is recovered as a by-product such as zinc smelting and aluminum smelting, or scraps containing Ga are recovered.

  As a method for purifying the recovered Ga to improve purity, Ga is acid-washed, heated and melted in contact with the metal oxide molded body or powder, and then the metal oxide molded body or powder. There has been proposed a method for obtaining high-purity Ga by separating (see, for example, Patent Document 1). In addition, a method for obtaining high-purity Ga by adding a mineral acid having a pH of 1 to 3 or a mixed solution thereof to Ga metal and stirring to remove impurities (see, for example, Patent Document 2) has also been proposed. Furthermore, a method for obtaining a high-purity metal by electrolytic collection has also been proposed (see, for example, Patent Document 3).

JP-A-11-269469 (paragraph number 0016) JP 63-183138 A (2nd page) JP 2002-285371 A (paragraph number 0005)

  However, when Ga contains metal elements such as iron (Fe), nickel (Ni), potassium (K), calcium (Ca), silicon (Si) as impurities, it is proposed in Patent Document 1 and Patent Document 2. In the method using acid cleaning as described above, it is difficult to remove a metal that is hardly soluble in Ga as described above. In addition, it is difficult to obtain high purity Ga of 6N or more by the method by electrolytic purification as proposed in Patent Document 3, and particularly when Ga contains Fe or Ni as an impurity, it is 6N or more. It is difficult to obtain high purity Ga. Furthermore, when purifying Ga by a crystal purification method, the Ga before purification must be high-purity Ga of 6N or more, and particularly Fe, Ni, K, Ca, Si, etc., which are hardly soluble in Ga metal. Is difficult to remove by the coagulation purification method of Ga.

  In addition, since Ga is used as a semiconductor material for electronic devices and light-emitting elements, it is necessary to obtain high-purity Ga of 6N or more with a very low impurity content.

  Therefore, in view of such a conventional problem, the present invention purifies gallium containing metal elements such as iron, nickel, potassium, calcium, and silicon as impurities, and the content of these impurities is very low. An object of the present invention is to provide a simple and inexpensive method for purifying gallium from which gallium can be obtained.

  As a result of earnest research to solve the above problems, the present inventors put gallium and water containing at least one metal selected from the group consisting of iron, nickel, potassium, calcium and silicon as impurities into a container. In addition to maintaining the temperature at which the gallium is melted, and maintaining the interface between the gallium and water at a temperature at which the gallium solidifies, the metal as the impurity and the compound of gallium or the metal as the impurity are The inventors have found that it can be deposited at the interface between gallium and water, and have completed the present invention.

  That is, the method for purifying gallium according to the present invention is a method in which gallium containing at least one metal selected from the group consisting of iron, nickel, potassium, calcium and silicon as impurities and water are placed in a container, and the gallium is melted. And maintaining at least part of the interface between the gallium and water at a temperature at which the gallium solidifies, thereby precipitating a precipitate on at least part of the interface between the gallium and water. And separating precipitates. In this gallium purification method, the gallium in the container is preferably stirred. In addition, the temperature at which gallium is melted is preferably not lower than the melting point of gallium and not higher than 31 ° C. (304.15 K), and the temperature at which gallium solidifies is not lower than 29 ° C. (302.15 K) and lower than the melting point of gallium. Preferably, the temperature is Further, the gallium metal according to the present invention has a purity of 99.9999% or more, the contents of iron, potassium, calcium and silicon as impurities are each 0.05 ppm or less, and the content of nickel is 0.1 ppm or less. It is characterized by being.

  According to the present invention, gallium containing metal elements such as iron, nickel, potassium, calcium, and silicon as impurities can be purified to obtain gallium with a very low content of these impurities, simple and inexpensive. A method for purifying gallium can be provided.

  In the embodiment of the method for purifying gallium according to the present invention, as shown in FIG. 1, a container 10 in which a hot water jacket 12 for adjusting the internal temperature by flowing warm water is arranged is placed on a stirring stirrer 14. The gallium 16 and the pure water 18 are put in the container 10. The amount of pure water 18 to be placed in the container 10 is preferably such that the height of the water surface is within 100 mm above the molten gallium 16 liquid surface, and the gallium 16 and pure water 18 to be purified. In order to promote the reaction at the interface, it is more preferable that the height of the water surface is an amount within 50 mm above the molten gallium 16 liquid surface. The stirrer 14 is not essential, but is preferably used to accelerate the reaction. The rotational speed of the stirrer 14 is such that when unevenness is formed on the surface of gallium 16, the thickness of the layer of pure water 18 is not uniform and temperature control becomes difficult, so that unevenness is not formed on the surface of gallium 16. It is preferable that the number of rotations is.

  When the temperature at which the gallium 16 in the container 10 is melted (29.8 to 31 ° C.) is maintained, impurities such as Fe, Ni, K, Ca, and Si in the gallium 16 float due to the difference in specific gravity. Thus, if the temperature of gallium 16 in the container 10 is maintained at 29.8 to 31 ° C., the temperature of the pure water 18 in the container 10 becomes 29 to 30 ° C. (this temperature is the thickness of the layer of the pure water 18). Therefore, it is preferable to adjust the thickness of the layer of pure water 18 so that the temperature is within this range.) A low temperature portion is generated at the interface between gallium 16 and pure water 18, and the temperature at this interface is gallium. 16 and a temperature at which the reaction product of pure water 18 solidifies. Therefore, it is possible to suppress the floating impurities from being trapped in the gallium solidified at the interface and returning to the molten gallium. That is, a spongy precipitate containing an impurity metal or a compound of the metal and gallium is generated from the molten gallium at the interface at a low temperature. After that, the metal as an impurity can be removed by removing water and removing sponge-like precipitates.

  In the gallium purification method of the present embodiment, a water layer having a thickness of 100 mm or less is formed on the molten gallium while maintaining the temperature at which the gallium in the container is melted. If the water layer on the molten gallium has a predetermined thickness, the temperature of the water drops due to the volatilization of the water, the heat is transferred, and the temperature at the interface between the gallium and water is precipitated. Temperature (29 ° C. to 30 ° C.). Moreover, when the thickness of the water layer is 50 mm or less, precipitation at the interface can be promoted. Note that, in addition to gallium metal, a sponge-like gallium-water compound precipitates at the interface between gallium and water, and the element as a floating impurity and the compound of the element are confined in this compound.

  Distilled water or ion-exchanged water may be used as water to be put in the container, but in order to obtain high-purity gallium, pure water that can prevent mixing of other impurities is used. Is preferred. Moreover, it is preferable that the stirring speed is below the speed at which the surface of the molten gallium maintains a flat state. When the stirring speed is increased and a dent is formed in the center, the thickness of the water layer changes, and it becomes difficult to control the temperature of the interface.

  Hereinafter, examples of the method for purifying gallium according to the present invention will be described in detail.

  First, as shown in Table 1, 4N Ga (pre-treatment Ga) containing 0.2 ppm or more of Fe, Ni, Si, K, and Ca was prepared. The Ga and pure water are put in a container 10 as shown in FIG. 1, the temperature of Ga in the container 10 is maintained at 29.8 to 31 ° C., and the stirrer 14 stirs the Ga at a stirring speed of 150 rpm to react. It was. After this reaction, pure water was removed from the container 10, sponge-like precipitates were removed, and Ga in the container 10 was recovered. Then, when the crystal | crystallization refinement | purification of collect | recovered Ga was performed, as shown in Table 1, all of content of Fe, Si, K, and Ca in this refined Ga (after-treatment Ga) are 0.05 ppm or less. Yes, the Ni content was reduced to 0.1 ppm. The Fe, Ni, Si, K, and Ca in the sponge-like precipitate are as shown in Table 1.

  As a comparative example, when the same crystal purification was performed on the same Ga (untreated Ga) as in the example, as shown in Table 2, Fe, Ni, K, and Ca in the purified Ga (treated Ga) were obtained. The content of each was 0.1 ppm or more, and the content of Si was 0.08 ppm.

It is a figure which shows typically the apparatus used for embodiment of the refinement | purification method of the gallium by this invention.

Explanation of symbols

10 containers 12 warm water jacket 14 stirrer 16 gallium 18 pure water

Claims (4)

Put gallium and water containing at least one metal selected from the group consisting of iron, nickel, potassium, calcium and silicon as impurities into a container and maintain the temperature at which the gallium is melted. Purifying gallium, wherein the precipitate is deposited on at least a part of the interface by maintaining at least a part of the interface at a temperature at which the gallium solidifies, and then the water and the precipitate are separated. Method. 2. The method for purifying gallium according to claim 1, wherein the gallium in the container is stirred. The method for purifying gallium according to claim 1 or 2, wherein a temperature at which the gallium is melted is a temperature not lower than the melting point of gallium and not higher than 31 ° C. The method for purifying gallium according to claim 3, wherein the temperature at which the gallium solidifies is a temperature of 29 ° C or higher and lower than the melting point of gallium.

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