JP2006193821A - High purity iron, high purity iron target, high purity cobalt, high purity cobalt target and method for producing high purity metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high purity metal capable of reducing the concentration of aluminum, silicon or the like being impurities. <P>SOLUTION: An impurity-containing metal is melted by plasma under an atmosphere comprising active oxygen. Alternatively, to an impurity-containing metal, the oxide of the metal is added, so as to be melted by plasma, and the melted impurity-containing metal and the melted oxide of the metal are made to coexist. The active oxygen or melted oxide oxidizes at least one impurity selected from aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium. Successively, it is melted by plasma under an active hydrogen-containing atmosphere. The active hydrogen reduces at least one impurity selected from the group consisting of oxygen, carbon and nitrogen. Thus, the impurities are easily removed from the metal, and the high purity metal can be produced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-purity metal and a high-purity metal target with a reduced impurity content, and a method for producing a high-purity metal.

  A semiconductor device such as a VLSI (Very Large Scale Integrated circuit) or ULSI (ultra LSI) has a structure in which various metal thin films are provided on a silicon (Si) wafer, for example. In recent years, studies using iron (Fe) as a material for magnetic random access memory (MRAM) and studies using cobalt (Co) as a wiring material have been made. However, if these metals contain harmful impurities, it may cause malfunction or deterioration of the semiconductor device, which is not preferable. For example, copper (Cu) has a high diffusion rate in silicon and causes a short circuit. Further, radioactive elements such as uranium (U) or thorium (Th) are likely to cause malfunction. Furthermore, alkali metals or alkaline earth metals cause characteristic deterioration. Therefore, the metal used for these semiconductor devices is required to have high purity.

In addition, there is beta-type iron silicide (β-FeSi ₂ ) using iron as an environmental semiconductor material that has been proposed with the aim of constructing new engineering to cope with future environmental problems or resource depletion problems. The content of impurities allowed for iron silicide as an environmental semiconductor is the same as that of a compound semiconductor typified by gallium arsenide (GaAs) or cadmium tellurium (CdTe), which is generally used at present. Very few compared to semiconductor devices called. This is because if unnecessary impurity levels are formed by a small amount of impurities, the semiconductor characteristics are deteriorated immediately. For this reason, metals used for environmental semiconductors are required to have higher purity.

  However, the grade of crude iron or crude cobalt currently being traded worldwide is about 98% to 99.8%. For example, the crude iron contains impurities such as nickel (Ni), cobalt, and chromium (Cr). However, crude cobalt contains impurities such as nickel, iron or chromium. Further, impurities of non-metallic elements such as oxygen (O), carbon (C), nitrogen (N) or sulfur (S) are also included. Therefore, in order to use a metal as a material for a semiconductor device or an environmental semiconductor, it is necessary to separate these impurities from crude iron, crude cobalt, etc. and to purify them. In addition to semiconductor devices, metals such as iron and cobalt are very promising as materials for magnetic recording media or magnetic recording heads by taking advantage of their properties as ferromagnetic metals. Therefore, high purity of these transition metals is indispensable for the purpose of using them.

Various methods for removing impurities from metals have been studied so far, for example, separation of metal elements by wet processing such as solvent extraction, ion exchange or electrolytic purification, and oxygen by dry hydrogen gas (H ₂ ) processing. Alternatively, there is removal of non-metallic elements such as nitrogen, vacuum melting, or floating zone melting purification.

  However, solvent extraction has a problem that it is difficult to control extraction and back-extraction, and it is difficult to purify metals stably industrially. In the electrolytic purification, there is a problem that it is necessary to control in the pH range of the electrolytic solution, and it is difficult to remove nickel or copper. In vacuum melting, it is easy to evaporate and separate alkali metal impurities and alkaline earth metal impurities with high vapor pressure, but evaporate and separate refractory metal impurities with low vapor pressure and metal impurities with low vapor pressure. There is a problem that evaporation loss of the metal to be purified is increased. In the floating zone melt refining, reports have been made on the fact that it is applied to a metal that has been purified to some extent to further increase its purity and actually have a large refining effect (see Non-Patent Document 1). There is a problem that it is difficult to manufacture a large amount of high-purity metal at low cost because it is difficult and is not a method that can be stably produced.

On the other hand, according to ion exchange, almost all impurity metals can be separated relatively stably industrially (see, for example, Patent Documents 1 and 2).
JP 2002-105633 A JP 2002-105598 A Yukio Ishikawa, Kouji Mimura, Minoru Isshiki, Floating Zone Refining of Iron Under Reduce Pressure with Dynamic Hydrogen Flow, “Materials Transactions, JIM (Materials Transactions JIM), The Japan Institute of Metals, 2000, Vol. 41, No. 3, pp. 420-424

  However, in ion exchange, since the metal is dissolved in, for example, an aqueous hydrochloric acid solution and brought into contact with the ion exchange resin, impurities must be separated and then reduced from chloride to metal. Therefore, there is a problem that impurities such as aluminum (Al) and silicon are mixed into the metal again from the heat-resistant glass, porcelain crucible or quartz boat used in the heat treatment at that time.

  By the way, recently, when a metal contains a nonmetallic element such as oxygen, carbon or nitrogen, especially oxygen, particles are generated during film formation by sputtering, which deteriorates the characteristics of the semiconductor device. Has become clear. Therefore, it has become a problem to separate these nonmetallic elements, particularly oxygen, from the metal.

  The present invention has been made in view of such problems, and a first object thereof is to provide a high-purity iron and a high-purity iron target, a high-purity cobalt and a high-purity cobalt target in which the concentration of oxygen as an impurity is reduced. There is to do.

A second object of the present invention is to provide a method for producing a high-purity metal capable of reducing the concentration of impurities such as aluminum and silicon.

  The high-purity iron according to the present invention has an impurity oxygen concentration of 1 mass ppm or less.

  The high-purity iron target according to the present invention has a concentration of oxygen as an impurity of 1 mass ppm or less.

  The high-purity cobalt according to the present invention has a concentration of oxygen as an impurity of 1 mass ppm or less.

  The high-purity cobalt target according to the present invention has a concentration of oxygen as an impurity of 1 mass ppm or less.

  The method for producing a high-purity metal according to the present invention melts a metal containing impurities, dissolves oxygen, or coexists with a molten oxide of this metal, and produces aluminum, calcium (Ca), chromium, iron, niobium (Nb ), Silicon, titanium (Ti), and zirconium (Zr), at least one impurity is oxidized to reduce the concentration of these impurities.

  According to the high-purity iron, high-purity iron target, high-purity cobalt, or high-purity cobalt target of the present invention, the concentration of oxygen as an impurity is set to 1 mass ppm or less. Can be suppressed, and characteristics of a semiconductor device and the like can be improved.

  According to the method for producing a high-purity metal of the present invention, a metal containing impurities is melted, oxygen is dissolved in the metal, or a metal and a molten oxide of the metal are allowed to coexist, and aluminum, calcium, chromium, iron At least one impurity of the group consisting of niobium, silicon, titanium and zirconium can be oxidized to easily separate the impurity from the metal. Therefore, the metal can be highly purified.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
The high-purity iron and the high-purity iron target according to one embodiment of the present invention preferably have an oxygen concentration of impurities of 1 mass ppm or less and 0.5 mass ppm or less.

  The total concentration of aluminum, calcium, chromium, niobium, silicon, titanium and zirconium is preferably 50 mass ppm or less, more preferably 1 mass ppm or less.

  In addition, the total concentration of cobalt, nickel and copper is preferably 3 mass ppm or less, and more preferably 1 mass ppm or less.

  Further, the total concentration of oxygen, nitrogen and carbon is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less.

  In particular, the total concentration of titanium, chromium, manganese (Mn), cobalt, nickel, copper and zinc is preferably 20 ppm by mass or less, more preferably 1 ppm by mass or less.

  Here, the concentration of impurities can be quantified by using, for example, glow discharge mass spectrometry with an analytical instrument. For non-metallic elements such as oxygen, nitrogen or hydrogen, for example, non-dispersive infrared absorption method, thermal conductivity method, or separation in a column after melting in an inert gas and measuring the thermal conductivity. It can be quantified.

The high-purity iron and the high-purity iron target are used as materials for semiconductor devices, magnetic recording media, magnetic recording heads, or devices using environmental semiconductors, for example. The environmental semiconductor is a semiconductor substance that is abundant on the earth and composed of environmentally friendly materials, and examples thereof include iron silicide and calcium silicide (Ca ₂ Si) (environmental semiconductor). Study group website (http://kan.engjm.saitama-u.ac.jp/SKS/index2.html).

  Such high-purity iron and high-purity iron target can be manufactured as follows, for example.

  FIG. 1 shows a manufacturing process of high purity iron and a high purity iron target. First, as shown in FIG. 2, a plasma arc melting furnace is prepared, iron containing impurities is placed in a crucible 3 in the melting chamber 1, and a plasma generation gas is supplied from a plasma gas supply source 5 to a plasma torch 2. Is supplied, a DC voltage is applied between the plasma torch 2 and the crucible 3 by the power source 4 to generate plasma and melt iron containing impurities (step S101).

  At that time, oxygen is dissolved in the melted iron (step S101). Specifically, when oxygen is mixed into the plasma generation gas and active oxygen is generated in the melting chamber 1, the active oxygen easily dissolves in the molten metal, and the metal elements and metalloid elements contained as impurities To produce an oxide. This oxide floats on the surface of the molten iron and concentrates to form a slag layer and separate from the iron. Note that oxygen may be mixed in the atmosphere in the melting chamber 1 without being mixed with the plasma generation gas.

  Active oxygen also oxidizes nonmetallic elements such as carbon, nitrogen, sulfur, and phosphorus (P) contained as impurities to generate an oxide gas. These oxide gases are released from the molten iron as carbon monoxide, nitrogen oxide, sulfur dioxide, phosphorus oxide, etc., and are separated from the iron.

  The specific impurity can be separated from iron in this way because the affinity for oxygen differs depending on the type of element. This will be specifically described with reference to FIG.

FIG. 3 shows the oxygen potential of oxides of main metal elements. In the figure, the vertical axis represents the oxygen partial pressure, and the horizontal axis represents the metal temperature. Each oxide shown in the drawing represents an oxide that is first generated when each metal element is oxidized, for example, FeO that is first generated in the case of iron. If the oxygen potential is further increased, Fe ₃ O ₄ and Fe ₂ O ₃ are generated in this order. Also, the positive direction of the vertical axis from each curve, that is, the region where the oxygen partial pressure is large represents the oxygen potential region where the oxide is generated. Represents an oxygen potential region where the metal is stabilized. Therefore, each curve represents a boundary between an oxygen potential region where an oxide is generated and an oxygen potential region where a metal is stabilized.

  In FIG. 3, for example, by setting the temperature and the oxygen partial pressure in the oxygen potential region where iron is stabilized and the oxide of other metal is generated, for example, the temperature is set to 2000 ° C., oxygen By setting the partial pressure to 0.1 Pa, a metal such as aluminum, calcium, chromium, niobium, silicon, titanium, and zirconium can be oxidized without oxidizing iron. Thereby, the oxidized impurity metal becomes a slag layer and is separated from iron, so that the concentration of these impurities can be reduced. Although not shown in FIG. 3, it is assumed that metals such as copper, magnesium (Mg), manganese, molybdenum (Mo), sodium (Na), lead (Pb), tantalum (Ta), and zinc are also oxides. And the concentration of these impurities can be reduced.

  In the present embodiment, the partial pressure of oxygen in the plasma generation gas is preferably 0.1 Pa or more and 10 kPa or less at 1536 ° C. or higher, which is the melting point of iron. In this case, an oxygen potential region in which iron oxide is generated is also included. This is because the iron oxide generated in this region is mixed with the impurity metal oxide on the surface of iron and mixed slag layer. This is because the activity of the oxide of the impurity metal can be reduced by further forming the metal, and the oxidation of the unoxidized impurity metal can be further promoted, and the iron can be further purified.

  The crucible 3 is preferably a copper crucible having high conductivity in order to generate plasma with the plasma torch 2. The crucible 3 is preferably cooled with water or the like when melting iron. This is because, by cooling, melting of the crucible 3 is avoided and a temperature gradient is provided inside the melted iron to cause convection. As a result, oxidation of the impurities is also promoted. Note that convection is also promoted by the active oxygen being dissolved and moved into the melted iron.

  The plasma generation gas described above may contain an inert gas. Examples of the inert gas include argon (Ar), helium (He), neon (Ne), and krypton (Kr).

  Moreover, it is preferable to make the pressure in the melting chamber 1 into the range of 1.33 kPa or more and 310 kPa or less, for example in 1536 degreeC or more which is melting | fusing point of iron. This is because metals other than iron can be easily oxidized within this range.

  Next, after iron containing impurities is melted by plasma containing active oxygen, the slag layer formed on the surface of the iron is removed by, for example, a mechanical method or a chemical method (step S102). Examples of the mechanical method include polishing by a polishing machine, cutting, or file. Examples of the chemical method include a method of immersing and dissolving in an acid such as dilute nitric acid solution or dilute hydrochloric acid until a metallic luster is generated on the surface.

  The total concentration of aluminum, calcium, chromium, niobium, silicon, titanium, and zirconium can be preferably 50 ppm by mass or less, more preferably 1 ppm by mass, by melting with plasma in an atmosphere containing the above active oxygen. It can be:

  Further, instead of dissolving active oxygen into molten iron, impurities may be removed as follows. First, iron oxide is mixed in advance with iron containing impurities, and this mixture is melted by, for example, plasma. As a result, the molten iron and the molten iron oxide coexist. This molten mixture separates into a molten iron layer and a molten iron oxide layer. At that time, metals such as aluminum, calcium, chromium, niobium, silicon, titanium, and zirconium having a higher affinity for oxygen than iron are oxidized and taken into the iron oxide layer to form a mixed slag layer. Note that the metal having a large affinity for oxygen referred to here is one having an oxygen potential generated by an oxide lower than that of the metal to be purified. Thereafter, the mixed slag layer is removed by, for example, a mechanical method or a chemical method as described above (step S102), and the total concentration of aluminum, calcium, chromium, niobium, silicon, titanium, and zirconium is calculated. Preferably it can be 50 mass ppm or less, More preferably, it can be 1 mass ppm or less.

  The plasma generation gas may not be mixed with oxygen, and oxygen may not be mixed into the atmosphere in the melting chamber 1. The mixture may be melted by plasma, but other methods may be used as long as the mixture can be melted.

  Furthermore, without mixing iron oxide with iron containing impurities in advance, by heating the iron containing impurities under an atmosphere containing oxygen, the surface is oxidized to form iron oxide and then melted. Also good. Thereby, as described above, the total concentration of aluminum, calcium, chromium, niobium, silicon, titanium and zirconium can be preferably 50 ppm by mass or less, more preferably 1 ppm by mass or less. It is.

  Subsequently, the iron from which the slag layer has been removed is placed in the crucible 3 of the plasma arc melting furnace shown in FIG. 2, and hydrogen is mixed into the plasma generation gas to generate active hydrogen in the melting chamber 1.

  In addition, iron is melted by plasma (step S103), and alkali metals such as sodium contained as impurities, alkaline earth metals such as calcium and magnesium, radioactive elements such as uranium and thorium, silicon, phosphorus, chromium, manganese , Zirconium, lead, titanium, aluminum, zinc, etc. are generated and react with active hydrogen as shown in chemical formula 1 or in the interior of molten iron chemical compound with active hydrogen dissolved in molten iron. It reacts as shown in.

（式中、Ｍ１はナトリウムなどのアルカリ金属、カルシウム、マグネシウムなどのアルカリ土類金属、ウラン、トリウムなどの放射性元素、ケイ素、リン、クロム、マンガン、ジルコニウム、鉛、チタン、アルミニウム、亜鉛などを示し、ｘおよびｙは正の数を表す。）

(In the formula, M1 represents an alkali metal such as sodium, an alkaline earth metal such as calcium or magnesium, a radioactive element such as uranium or thorium, silicon, phosphorus, chromium, manganese, zirconium, lead, titanium, aluminum or zinc. , X and y represent positive numbers.)

  Since these impurity metals have a higher vapor pressure than iron, evaporation of these impurity metals is promoted by forming a temporary loose bond between the impurity metal and active hydrogen. Thereby, the concentration of these impurity metals is further reduced.

  Nonmetallic elements such as oxygen, nitrogen, carbon, and sulfur contained in iron react with active hydrogen as shown in Chemical Formula 2.

（式中、ｚは正の数を表す。）

(In the formula, z represents a positive number.)

That is, oxygen combines with active hydrogen to form water (H ₂ O), nitrogen combines with active hydrogen to form nitrogen hydride (NH _z ), and carbon combines with active hydrogen to form hydrocarbons such as methane or ethane. gas (C _b H _{c; b} and c represents a positive number) and a. Since the bond here is stronger than the bond between the active hydrogen and the impurity metal described above, the generated water (H ₂ O) or the like is released from the inside of the molten iron to the outside of the iron. Thereby, the concentration of oxygen mixed in the purification step with oxygen in step S101 is reduced, and the concentrations of other gaseous impurities such as nitrogen and carbon are also reduced.

  The total concentration of oxygen, nitrogen, and carbon can be preferably 50 ppm by mass or less, and more preferably 10 ppm by mass or less by melting with plasma in an atmosphere containing the above active hydrogen.

  Moreover, as shown in FIG. 4, you may make it perform the refinement | purification process (step S200) using an anion exchange resin before the refinement | purification process by oxygen. This is preferable because the impurity concentration can be further reduced and the time required for the purification step using oxygen or the like can be shortened.

FIG. 5 shows a purification process using an anion exchange resin. First, iron containing impurities is dissolved in a hydrochloric acid solution to prepare an iron chloride (FeCl ₂ or FeCl ₃ ) aqueous solution M2 (step S211). At that time, the hydrochloric acid concentration is adjusted within the range of 0.1 kmol / m ³ or more and 6 kmol / m ³ or less.

Next, as shown in FIG. 6, this aqueous iron chloride solution M2 is put into a container 12 together with a metal 11 such as iron, and an inert gas 13 such as nitrogen gas (N ₂ ) or argon gas is blown in, and the aqueous iron chloride solution M2 is blown. The metal 11 is agitated by, for example, the stirrer 14 and sufficiently brought into contact (step S212). Thereby, copper contained as an impurity in the iron chloride aqueous solution M2 reacts as shown in Chemical Formula 3, for example, and changes from divalent ions to monovalent ions or metallic copper. Further, iron contained in the iron chloride aqueous solution M2 reacts as shown in Chemical Formula 4, for example, and changes from trivalent ions to divalent ions. The reaction formula shown in Chemical Formula 3 does not proceed completely to the right, and a little monovalent copper ion remains in the aqueous iron chloride solution.

  Here, the inert gas 13 is blown into the iron chloride aqueous solution M2 in order to expel oxygen dissolved in the iron chloride aqueous solution M2, and in the reactions shown in Chemical Formula 3 and Chemical Formula 4, oxygen is added to the iron chloride aqueous solution M2. Does not progress if dissolved. The blowing of the inert gas 13 may be performed simultaneously with stirring the aqueous iron chloride solution M2 and the metal 11, or may be performed before putting the metal 11 into the aqueous iron chloride solution M2.

  The metal 11 preferably has a large surface area such as powder. This is because copper and iron can be sufficiently reacted by increasing the contact area with the aqueous iron chloride solution M2. Although metals other than iron can be used as the metal 11, iron is preferred. This is to prevent other impurities from entering the iron chloride aqueous solution M2 as much as possible.

  Here, after adjusting the hydrochloric acid concentration of the aqueous iron chloride solution M2, the aqueous iron chloride solution M2 and the metal 11 are brought into contact with each other so that iron becomes a divalent ion and copper becomes a monovalent ion. After bringing the aqueous solution M2 into contact with the metal 11 to make iron a divalent ion and copper to a monovalent ion, the hydrochloric acid concentration of the iron chloride aqueous solution M2 may be adjusted.

  Subsequently, as shown in FIG. 7, a column 22 filled with an anion exchange resin 21 is prepared, and an aqueous iron chloride solution M2 is poured into the column 22 from the storage tank 23 and is sufficiently brought into contact with the anion exchange resin 21 ( Step S213). The flow rate of the aqueous iron chloride solution M2 is such that the resin volume is allowed to flow for 1 hour (1 bed volume (s) / hour) or more so that the aqueous iron chloride solution M2 is in sufficient contact with the anion exchange resin 21. It is preferable that the liquid is slowly poured over. Here, since iron is a divalent ion and copper is a monovalent ion, monovalent copper is adsorbed on the anion exchange resin 21 and divalent iron is adsorbed on the anion exchange resin 21 at all. Elute from column 22 instead. FIG. 8 shows the change (elution curve) of the metal ion concentration in the eluate at this time. In FIG. 8, the horizontal axis represents the elution volume, and the vertical axis represents the concentration normalized by the maximum concentration of metal ions. Thus, it can be seen that the peaks of the elution curves of divalent iron and monovalent copper do not overlap at all, and copper can be completely separated from the aqueous iron chloride solution. That is, the recovery tank 24 recovers the iron chloride aqueous solution M2 from which copper is separated.

  In addition, zinc, gallium (Ga), niobium, technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd), indium (In) are added to the iron chloride aqueous solution M2. , Tin (Sn), antimony (Sb), tellurium (Te), tantalum, tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury ( When at least one impurity of the group consisting of Hg), thallium (Tl), lead and bismuth (Bi) is contained, these impurities are obtained in step S213 as shown by zinc in FIG. Is adsorbed on the anion exchange resin 21 together with copper and separated from the iron chloride aqueous solution M2.

  After separating copper, the aqueous solution of iron chloride M2 is added to lithium (Li), beryllium (Be), sodium, magnesium, aluminum, silicon, phosphorus, potassium (K), calcium, scandium (Sc), titanium, vanadium (V), Chromium, manganese, cobalt, nickel, rubidium (Rb), strontium (Sr), yttrium (Y), zirconium, cesium (Cs), barium (Ba), lanthanoids, hafnium (Hf), francium (Fr), radium ( When at least one impurity selected from the group consisting of Ra) and actinoids is contained, for example, hydrogen peroxide solution is added to the aqueous iron chloride solution M2 to oxidize it to convert iron from divalent ions to trivalent ions. (Step S214). In addition, since this oxidation occurs naturally even if it is left as it is, it is not necessary to actively perform the oxidation step.

After that, the hydrochloric acid concentration of the aqueous iron chloride solution M2 is adjusted within the range of 2 kmol / m ³ or more and 11 kmol / m ³ or less, and the aqueous iron chloride solution M2 is in sufficient contact with the anion exchange resin 21 as shown in FIG. (Step S215). As a result, trivalent iron is adsorbed on the anion exchange resin 21, and lithium, beryllium, sodium, magnesium, aluminum, silicon, phosphorus, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, Rubidium, strontium, yttrium, zirconium, cesium, barium, lanthanoids, hafnium, francium, radium and actinoids are eluted without adsorbing to the anion exchange resin 21.

  FIG. 9 shows the change (elution curve) of the metal ion concentration in the eluate at this time. FIG. 9 represents aluminum, silicon, phosphorus, titanium, manganese, cobalt, and chromium as a representative of the above-described impurities, and the horizontal axis and the vertical axis are the same as those in FIG. Thus, it can be seen that the peaks of the elution curves of these impurities and trivalent iron do not substantially overlap, and that these impurities and iron can be substantially separated.

  Moreover, zinc, gallium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury In the case where at least one impurity selected from the group consisting of thallium, lead, bismuth and polonium (Po) is contained, these impurities are also adsorbed to the anion exchange resin 21 together with iron in step S215.

In this case, after the iron is adsorbed on the anion exchange resin 21, a hydrochloric acid solution having a concentration of 0.1 kmol / m ³ or more and 2 kmol / m ³ or less is flowed to elute the iron from the anion exchange resin 21. Zinc, gallium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold Then, mercury, thallium, lead, bismuth, polonium and iron are separated (step S216). The change (elution curve) of the metal ion concentration in the eluate at this time is also shown in FIG. FIG. 9 is a comparison of tin with iron on behalf of the impurities described above. Thus, it can be seen that the peaks of the elution curves of these impurities and trivalent iron do not substantially overlap, and that these impurities and iron can be substantially separated.

  However, here, already in step S213, zinc, gallium, niobium, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury Since thallium, lead and bismuth are separated from the iron chloride aqueous solution M2 together with copper, molybdenum and polonium are mainly separated from iron in step S216.

  After elution of iron, the obtained iron chloride aqueous solution M2 is evaporated to dryness on, for example, heat-resistant glass and oxidized in a porcelain crucible coated with glaze to obtain iron oxide (step S217). After that, for example, iron oxide is heated in a hydrogen atmosphere at a temperature of 500 K or higher and lower than 1800 K on a quartz boat or an alumina boat (step S218). However, it is preferable to heat at a temperature of 1000 K or higher in order to perform the reduction quickly. Thereby, iron oxide reacts as shown in Chemical Formula 5, and iron is obtained.

  By the purification process using the above anion exchange resin, the total concentration of cobalt, nickel and copper can be preferably 3 ppm by mass or less, more preferably 1 ppm by mass or less.

  The total concentration of titanium, chromium, manganese, cobalt, nickel, copper and zinc can be preferably 20 ppm by mass or less, more preferably 1 ppm by mass or less.

  Note that impurities such as silicon or aluminum may be mixed in by this step, but these impurities are reduced by the above-described purification step using oxygen.

  As described above, according to the high-purity iron and the high-purity iron target of the first embodiment, since the oxygen concentration is 1 mass ppm or less, generation of particles can be suppressed during film formation by sputtering. For example, the characteristics of the semiconductor device can be improved. In addition, since the total concentration of aluminum, calcium, chromium, niobium, silicon, titanium and zirconium is 50 ppm by mass or less, the characteristics of the semiconductor device can be further improved. Furthermore, since the total concentration of cobalt, copper and nickel is 1 mass ppm or less, for example, even when used in a semiconductor device, a short circuit does not occur, and the characteristics can be further improved. It can also be used for devices such as magnetic recording media and magnetic recording heads, and the characteristics thereof can be improved. In particular, when used as a material for a compound semiconductor such as iron silicide, unnecessary impurity levels due to trace impurities such as characteristic deterioration are not formed, and excellent characteristics can be obtained.

[Second Embodiment]
The high-purity cobalt and the high-purity cobalt target according to an embodiment of the present invention have a concentration of oxygen as an impurity of 1 mass ppm or less, and more preferably 0.5 mass ppm or less.

  The total concentration of aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium is preferably 50 ppm by mass or less, more preferably 1 ppm by mass or less.

  In addition, the total concentration of nickel and copper is preferably 50 ppm by mass or less, more preferably 1 ppm by mass or less.

  Further, the total concentration of oxygen, nitrogen and carbon is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less.

  In particular, the concentration of titanium, chromium, manganese, iron, nickel, copper and zinc is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and even more preferably 5 mass ppm or less.

  Such high-purity cobalt and high-purity cobalt target, for example, as shown in FIG. 1 in the same manner as in the first embodiment, melts cobalt containing impurities and dissolves oxygen or cobalt. And molten cobalt oxide can coexist.

  In addition, when melting cobalt containing impurities under an active oxygen atmosphere, iron is also removed. This is because, as shown in FIG. 3, the potential region in which the cobalt oxide is generated is in a region having a higher oxygen partial pressure than the oxygen potential region in which the iron oxide is generated.

  Moreover, what is necessary is just to use a cobalt oxide, when adding and melt | dissolving an oxide.

  By dissolving cobalt containing the above impurities and dissolving oxygen, or by coexisting cobalt and molten cobalt oxide, the total concentration of aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium can be calculated. Preferably it can be 50 mass ppm or less, More preferably, it can be 1 mass ppm or less.

  Moreover, the total of the concentration of oxygen, nitrogen, and carbon can be preferably 50 ppm by mass or less, and more preferably 10 ppm by mass or less by melting with plasma in an atmosphere containing active hydrogen.

  In this embodiment, when cobalt containing impurities is melted in an active oxygen atmosphere, the partial pressure of oxygen in the plasma generation gas is 1495 ° C. or higher, which is the melting point of cobalt, as in the first embodiment. In this case, the pressure is preferably 0.1 Pa or more and 102 Pa or less.

  Moreover, it is preferable to make the pressure in the melting chamber 1 into the range of 1.33 or more and 310 kPa or less, for example in 1495 degreeC or more which is melting | fusing point of cobalt. This is because a metal other than cobalt can be easily oxidized within this range.

  Moreover, as shown in FIG. 4, you may make it perform the refinement | purification process (step S200) using an anion exchange resin before the refinement | purification process by oxygen. This is preferable because the impurity concentration can be further reduced and the time required for the purification step using oxygen or the like can be shortened.

FIG. 10 shows a purification process using an anion exchange resin. First, cobalt containing impurities is dissolved in a hydrochloric acid solution to prepare a cobalt chloride (CoCl ₂ ) aqueous solution M3 (step S221). At that time, the hydrochloric acid concentration is adjusted within the range of 0.1 kmol / m ³ or more and ³ kmol / m ³ or less.

  Next, as shown in FIG. 6, the cobalt chloride aqueous solution M3 is put in a container 12 together with a metal 11 such as cobalt, and an inert gas 13 such as nitrogen gas or argon gas is blown in, and the cobalt chloride aqueous solution M3 and the metal 11 Is agitated by, for example, the stirrer 14 and sufficiently brought into contact (step S222). Thereby, the copper contained as an impurity in the cobalt chloride aqueous solution M3 reacts as shown in Chemical Formula 6, for example, and changes from a divalent ion to a monovalent ion.

  Here, the inert gas 13 is blown into the cobalt chloride aqueous solution M3 in order to expel oxygen dissolved in the cobalt chloride aqueous solution M3, and the reaction shown in Chemical Formula 6 is performed when oxygen is dissolved in the cobalt chloride aqueous solution M3. If it is, it will not progress. The blowing of the inert gas 13 may be performed simultaneously with stirring the cobalt chloride aqueous solution M3 and the metal 11, or may be performed before putting the metal 11 into the cobalt chloride aqueous solution M3.

  The metal 11 preferably has a large surface area such as powder. This is because copper can be sufficiently reacted by increasing the contact area with the cobalt chloride aqueous solution M3. Although metals other than cobalt can be used as metal 11, cobalt is preferred. This is to prevent other impurities from entering the cobalt chloride aqueous solution M3 as much as possible.

  Here, after adjusting the hydrochloric acid concentration of the cobalt chloride aqueous solution M3, the cobalt chloride aqueous solution M3 and the metal 11 are brought into contact with each other so that copper becomes a monovalent ion. However, the cobalt chloride aqueous solution M3 is brought into contact with the metal 11. After making copper into monovalent ions, the hydrochloric acid concentration of the cobalt chloride aqueous solution M3 may be adjusted.

  Subsequently, as shown in FIG. 7, a column 22 filled with the anion exchange resin 21 is prepared, and the cobalt chloride aqueous solution M3 is poured from the storage tank 23 into the column 22 and is sufficiently brought into contact with the anion exchange resin 21 ( Step S223). The flow rate of the cobalt chloride aqueous solution M3 is such that the resin volume is allowed to flow over 1 hour (1 bed volume (s) / hour) or more so that the cobalt chloride aqueous solution M3 is in sufficient contact with the anion exchange resin 21. It is preferable to flow slowly. Here, since copper is a monovalent ion, the monovalent copper is adsorbed on the anion exchange resin 21, and cobalt is eluted from the column 22 without being adsorbed on the anion exchange resin 21 at all. FIG. 11 shows the change (elution curve) of the metal ion concentration in the eluate at this time. In FIG. 11, the horizontal axis and the vertical axis are the same as those in FIG. Thus, it can be seen that the peaks of the elution curves of cobalt of monovalent ions and copper of monovalent ions do not overlap at all, and copper can be completely separated from the cobalt chloride aqueous solution. That is, in the recovery tank 24, the cobalt chloride aqueous solution M3 from which copper has been separated is recovered.

  When impurities such as zinc are contained in the cobalt chloride aqueous solution M3, as shown in FIG. 11, zinc is also adsorbed on the anion exchange resin 21 together with copper in step S223 and separated from the cobalt chloride aqueous solution M3. Is done. Examples of elements separated in the same manner as zinc include technetium, ruthenium, palladium, silver, cadmium, indium, tin, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth and polonium. That is, when the cobalt chloride aqueous solution M3 contains at least one of these impurities, it is separated together with copper.

After separating copper, cobalt chloride aqueous solution M3 contains cobalt chloride if it contains at least one impurity selected from the group consisting of titanium, chromium, manganese, nickel, aluminum, alkali metals and alkaline earth metals The hydrochloric acid concentration of the aqueous solution M3 is adjusted within the range of 7 kmol / m ³ or more and 11 kmol / m ³ or less, and as shown in FIG. 7, the cobalt chloride aqueous solution M3 is sufficiently brought into contact with the anion exchange resin 21 (step S224). . Thereby, cobalt is adsorbed on the anion exchange resin 21 and separated from titanium, chromium, manganese, nickel, aluminum, alkali metal or alkaline earth metal that is not adsorbed on the anion exchange resin 21. Changes in the metal ion concentration (elution curve) in the eluate at this time are shown in FIG. In FIG. 12, the horizontal axis and the vertical axis are the same as those in FIG.

The cobalt chloride aqueous solution M3 is made of iron, zinc, molybdenum, technetium, ruthenium, palladium, silver, cadmium, indium, tin, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth and polonium. If at least one impurity in the group is contained, these impurities are also adsorbed to the anion exchange resin 21 together with cobalt in step S224. In this case, after the cobalt is adsorbed on the anion exchange resin 21, a hydrochloric acid solution having a concentration of 2.5 kmol / m ³ or more and 5 kmol / m ³ or less is flowed to elute the cobalt from the anion exchange resin 21, Iron, zinc, molybdenum, technetium, ruthenium, palladium, silver, cadmium, indium, tin, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth or polonium And cobalt are separated (step S225).

  However, here, in step S223, zinc, technetium, ruthenium, palladium, silver, cadmium, indium, tin, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, and polonium together with copper are in an aqueous cobalt chloride solution. Since it is separated from M3, mainly iron, molybdenum and tungsten are separated from cobalt in step S225.

  After elution of cobalt, the obtained cobalt chloride aqueous solution M3 is evaporated to dryness on, for example, heat-resistant glass to obtain cobalt chloride or a hydrate thereof (step S226). Thereafter, cobalt chloride or a hydrate thereof is heated at a temperature of 623 K or more and less than 873 K (350 ° C. or more and less than 600 ° C.) in a hydrogen atmosphere using an apparatus as shown in FIG. 13 (step S227). Thereby, cobalt chloride or a hydrate thereof reacts as shown in Chemical Formula 7 to obtain cobalt. In the apparatus shown in FIG. 13, a reaction tube 32 is installed in a heating furnace 31, hydrogen gas 33 is supplied from one end to the reaction tube 32, and hydrogen chloride gas generated by the reaction from the other end. Is discharged, and the discharged hydrogen chloride gas is absorbed by the processing unit 34.

  In this case, the heating temperature is set to 623 K or more because cobalt chloride cannot be sufficiently reacted at a temperature lower than this, and the heating temperature is set to less than 873 K, even if the temperature is less than 873 K. This is because the temperature can be reduced as much as possible, and the manufacturing apparatus can be simplified because the reaction can be performed. FIG. 14 shows the relationship between the heating temperature and the reaction rate (reduction rate). In FIG. 14, the horizontal axis represents time, the vertical axis represents the reduction rate, and the reaction rate was determined based on the fact that 2 mol of hydrogen chloride is produced when 1 mol of cobalt is reduced as shown in Chemical formula 7. It is obtained from the change in hydrogen concentration. FIG. 14 also shows that cobalt can be sufficiently reduced at 623 K or more and less than 873 K.

  Note that impurities such as silicon or aluminum may be mixed in by this step, but these impurities are reduced by the above-described purification step using oxygen.

  Moreover, you may make it manufacture by isolate | separating an impurity from cobalt chloride aqueous solution M3 in the following procedures.

First, an inert gas is blown into the cobalt chloride aqueous solution M3, and the cobalt chloride aqueous solution M is brought into contact with the metal 11 to make copper a monovalent ion (step S222). Next, the hydrochloric acid concentration of the cobalt chloride aqueous solution M is adjusted to 7 kmol / m ³ or more and 11 kmol / m ³ or less, cobalt is adsorbed on the anion exchange resin 21 and separated from impurities such as titanium (step S224). Subsequently, the cobalt adsorbed on the anion exchange resin 21 is eluted with a hydrochloric acid solution having a concentration of 2.5 kmol / m ³ or more and 5 kmol / m ³ or less, and impurities such as molybdenum adsorbed on the anion exchange resin 21 together with cobalt. (Step S225). After that, the hydrochloric acid concentration of the cobalt chloride aqueous solution M3 is adjusted to 0.1 kmol / m ³ or more and ³ kmol / m ³ or less (step S221), and copper is adsorbed on the anion exchange resin 21 to be separated from the cobalt chloride aqueous solution M3 ( Step S223).

After making copper a monovalent ion (step S222), the hydrochloric acid concentration of the cobalt chloride aqueous solution M3 is adjusted to adsorb cobalt to the anion exchange resin 21 to separate it from impurities such as titanium (step S224). The cobalt adsorbed on the anion exchange resin 21 is eluted with a hydrochloric acid solution having a concentration of 0.1 to ³ kmol / m ³ and separated from impurities such as copper adsorbed on the anion exchange resin 21 together with cobalt. After that, the hydrochloric acid concentration of the cobalt chloride aqueous solution M3 is adjusted to 2.5 kmol / m ³ or more and 5 kmol / m ³ or less, and impurities such as iron, molybdenum or tungsten are adsorbed on the anion exchange resin 21 to thereby adjust the cobalt chloride aqueous solution. You may make it isolate | separate from M3.

In these cases, the concentration of the hydrochloric acid solution that elutes the cobalt adsorbed on the anion exchange resin 21 is adjusted to 2.5 kmol / m ³ or more and ³ kmol / m ³ or less, and impurities such as iron, molybdenum, or tungsten are cobalt together with copper. And may be separated.

  Further, the hydrochloric acid concentration of the aqueous cobalt chloride solution M3 is adjusted to adsorb cobalt to the anion exchange resin 21 to separate it from impurities such as titanium (step S224), and adsorbed to the anion exchange resin 21 with the hydrochloric acid solution having the adjusted concentration. After eluting the separated cobalt and separating it from impurities such as molybdenum (step S225), copper is converted to a monovalent ion (step S222), and the hydrochloric acid concentration of the cobalt chloride aqueous solution M3 is adjusted to add copper to the anion exchange resin 21. You may make it adsorb | suck and isolate | separate (step S223). However, in this case, since impurities may be mixed in the step of using copper as a monovalent ion, it is preferable to carry out by any of the procedures described above.

  By the purification step using the above anion exchange resin, the total concentration of nickel and copper can be preferably 50 ppm by mass or less, and more preferably 1 ppm by mass or less.

  The concentration of titanium, chromium, manganese, iron, nickel, copper, and zinc can be preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, and still more preferably 5 ppm by mass or less.

  As described above, according to the high purity cobalt and the high purity cobalt target of the second embodiment, since the oxygen concentration is 1 mass ppm or less, generation of particles can be suppressed during film formation by sputtering. For example, the characteristics of the semiconductor device can be improved. In addition, since the total concentration of aluminum, calcium, chromium, iron, niobium, silicon, titanium, and zirconium is 50 ppm by mass or less, the characteristics of the semiconductor device can be further improved. Furthermore, since the total concentration of copper and nickel is 50 ppm by mass or less, for example, even when used in a semiconductor device, a short circuit does not occur, and the characteristics can be further improved. It can also be used for devices such as magnetic recording media and magnetic recording heads, and the characteristics thereof can be improved.

[Third Embodiment]
The method for producing a high-purity metal according to an embodiment of the present invention involves melting a metal containing impurities as described in the first or second embodiment and dissolving oxygen or purifying the metal. By coexisting with the target metal molten oxide, at least one impurity of the group consisting of aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium is oxidized and removed.

  In the case where a metal containing impurities is melted by plasma in an atmosphere containing active oxygen, the oxygen partial pressure is set according to the metal to be purified with reference to FIG. 3, for example. Specifically, the oxygen partial pressure is set lower than, for example, an oxygen potential region where a metal oxide to be purified is generated, and an impurity that is more easily oxidized than that metal is oxidized. Alternatively, the oxygen partial pressure may be slightly higher than that, and the metal to be purified and the impurity metal may be oxidized together. These oxides form a slag layer on the surface of the metal, thereby reducing the concentration of impurities. This method is not limited to refining iron or cobalt, but can be widely used for refining metals with high oxygen potential generated by oxides. For example, in addition to iron or cobalt, gold, silver, platinum, It is particularly preferred when purifying noble metals such as rhodium or palladium.

  In addition, when an oxide is added and melted, a metal oxide to be purified may be used.

  Furthermore, after the slag layer formed on the surface of the metal is removed by a mechanical method or a chemical method, similarly to the first or second embodiment, the slag layer is melted by plasma in an atmosphere further containing active hydrogen. You may make it do. As a result, alkali metals such as sodium, alkaline earth metals such as calcium and magnesium, light elements such as oxygen, nitrogen, carbon and sulfur, radioactive elements such as uranium and thorium, silicon, phosphorus, chromium, manganese, zirconium and lead This is because at least one impurity in the group consisting of titanium, aluminum, and zinc can be removed and the purity can be further increased. In particular, when purification with oxygen is performed as described above, a large amount of oxygen remains in the metal, so that this oxygen can be effectively removed.

  Note that a method for melting metal by plasma in an atmosphere containing active hydrogen may be the same as in the first or second embodiment described above.

  Moreover, you may make it perform the refinement | purification process using an anion resin before the refinement | purification process by oxygen. This is preferable because the concentration of impurities can be further reduced and the time required for the purification step using active oxygen or the like can be shortened.

  Note that impurities such as silicon or aluminum are mixed in by this step, but these impurities are reduced by the above-described purification step using oxygen.

  As described above, according to the present embodiment, the metal containing impurities is melted, and oxygen is dissolved in the metal or coexists with the molten oxide of the metal intended for purification. An impurity metal having a higher affinity for oxygen than a metal can be easily separated from the metal and the concentration thereof can be reduced. Therefore, the metal can be easily highly purified.

  In particular, if melting is performed by plasma in an atmosphere containing active hydrogen, the concentration of at least one of the group consisting of oxygen, nitrogen, and carbon can be reduced, and the metal can be further purified. it can.

  In addition, the metal containing impurities is dissolved, and before the oxygen is dissolved in the metal or coexisted with the molten oxide of the metal to be purified, the metal is dissolved in an aqueous hydrochloric acid solution to adjust the concentration of hydrochloric acid. If the contact is made with the anion exchange resin, at least one impurity in the group consisting of cobalt, nickel and copper can be separated, and the concentration of other impurities can be further reduced.

  Therefore, for example, it can be used as a material for a semiconductor device, a magnetic recording medium, a magnetic recording head, or a device using an environmental semiconductor.

  Further, embodiments of the present invention will be specifically described with reference to the drawings.

(Example 1-1)
A small plasma arc furnace with a maximum output of 20 kW as shown in FIG. 2 was prepared, and 50 g of electrolytic iron having a purity as shown in Table 1 was placed in a copper crucible as the crucible 3. Next, the inside of the melting chamber 1 was evacuated and then replaced with an argon atmosphere. Subsequently, while the copper crucible is cooled with water, a plasma torch is supplied from the gas supply source 5 with an oxygen gas having a partial pressure of 100 Pa (oxygen capacity is 0.1% by volume) as a plasma generation gas at a flow rate of 5 liters per minute. While supplying to 2, a DC voltage was applied by the power source 4 to generate plasma, and the electrolytic iron in the copper crucible was melted. In addition, the melting temperature at this time was 2000 degreeC.

  Several minutes after the start of melting, it was observed that an island-like thin slag layer moved to the surface of the molten electrolytic iron. This slag layer increased in area over time and occupied about two thirds of the surface of the molten electrolytic iron after 10 minutes. After this, no increase in the area of the slag layer was observed, but the melting was continued for another 10 minutes in order to more reliably oxidize the impurities. Thereafter, the molten iron was cooled, and an iron lump was taken out from the melting chamber 1.

  The slag layer formed on the surface of the iron lump taken out is removed by mechanical polishing with a polishing machine, and further immersed in a 2 mol / l nitric acid solution to chemically polish the surface slag layer, The slag layer was completely removed to obtain about 45 g of iron lump.

(Example 1-2)
The iron lump obtained in Example 1-1 was used for the plasma generation gas from the gas supply source 5 using the small plasma arc furnace used in Example 1-1, and the hydrogen partial pressure was 20 kPa (hydrogen capacity was 20% by volume). The argon gas was melted by plasma. In addition, the melting temperature at this time was 2000 degreeC. Thereafter, the molten iron was cooled to obtain an iron lump.

(Example 1-3)
The electrolytic iron shown in Table 1 as the raw material, which was dissolved so that the iron concentration in the hydrochloric acid solution of concentration 2kmol / m ³ becomes ^{0.179kmol / m 3 (10g / dm} 3), iron chloride (FeCl ₃₎ An aqueous solution M2 was prepared. Next, as shown in FIG. 6, powdered iron 11 was put into this iron chloride aqueous solution M2, and stirred while blowing an inert gas to make copper a monovalent ion, and iron was made a divalent ion. Subsequently, as shown in FIG. 7, the aqueous iron chloride solution M2 was brought into contact with the anion exchange resin 21 to adsorb copper and separated from the aqueous iron chloride solution M2.

After separating copper, hydrogen peroxide solution was added to the aqueous iron chloride solution M2 to convert iron into trivalent ions. Thereafter, the concentration of hydrochloric acid in the aqueous iron chloride solution M2 was set to 5 kmol / m ^3, and the aqueous iron chloride solution M2 was brought into contact with the anion exchange resin 21 to adsorb iron and separated from impurities such as lithium. Next, iron was eluted from the anion exchange resin 21 with a hydrochloric acid solution having a concentration of 1 kmol / m ³ and separated from impurities such as molybdenum.

  After elution of iron from the anion exchange resin 21, the obtained iron chloride aqueous solution M2 was evaporated to dryness on heat-resistant glass and oxidized in a porcelain crucible coated with glaze to obtain iron oxide. After that, the obtained iron oxide was placed in a quartz boat and heated at 1073 K (800 ° C.) in a hydrogen atmosphere to obtain iron.

  The obtained iron was melted by plasma while supplying oxygen in the same manner as in Example 1-1, and the slag layer was removed to obtain an iron lump.

  The obtained iron lump was melted by plasma while supplying hydrogen in the same manner as in Example 1-2, and cooled to obtain an iron lump.

[Analysis of impurity concentration]
The iron obtained in Examples 1-1 to 1-3 was analyzed for impurity concentration by glow discharge mass spectrometry. The obtained results are shown in Table 1. The concentration is the sum of the impurity concentrations in the table subtracted from 1 (Mitsuyoshi Ishiki, Koji Mimura, “Purification of Metals”, Journal of the Japan Institute of Metals, 1992, Vol. 31, p.880. -887) (hereinafter the same in this example).

  As can be seen from Table 1, the concentration of aluminum, calcium, chromium, niobium, silicon, titanium, and zirconium could be reduced by melting with plasma in an atmosphere containing active oxygen. In addition, the oxygen concentration could be reduced by melting with plasma in an atmosphere containing active hydrogen.

(Examples 2-1 to 2-3)
40 g of a mixture of high-purity iron oxide (Fe ₂ O ₃ ) mixed with electrolytic iron was melted with plasma by supplying only argon gas without supplying oxygen gas. At that time, in Example 2-1, 39 g of electrolytic iron and 1 g of high-purity iron oxide were mixed. In Example 2-2, 38 g of electrolytic iron and 2 g of high-purity iron oxide were mixed. In Example 2-3, 37 g of electrolytic iron and 3 g of high-purity iron oxide were mixed. Other melting conditions were the same as in Example 1-1.

  After starting the melting, it was observed that the mixed slag layer of iron oxide and impurity oxide moved to the surface of the molten electrolytic iron. This slag layer maintained a constant area over time and did not increase or decrease. This melting was carried out for a total of 10 minutes in order to more reliably oxidize the impurities. Thereafter, the molten electrolytic iron was cooled, and an iron lump was taken out from the melting chamber 1.

By immersing the mass of the extracted iron 2kmol / m ³ or more 5kmol / m ³ or less of hydrochloric acid solution, grinding the slag layer on the surface chemically to obtain a complete removal and mass iron slag layer.

(Examples 2-4 to 2-6)
The iron lump obtained in Examples 2-1 to 2-3 was melted by plasma while supplying hydrogen in the same manner as in Example 1-2, and cooled to obtain an iron lump.

(Example 2-7)
The electrolytic iron used in Examples 2-1 to 2-6 was dissolved in a hydrochloric acid solution and brought into contact with an anion exchange resin in the same manner as in Example 1-3, and then heated to obtain iron.

  In the same manner as in Example 2-2, high-purity iron oxide was added to the obtained iron and melted by plasma, and the slag layer was removed to obtain an iron lump.

  The obtained iron lump was melted by plasma while supplying hydrogen in the same manner as in Example 2-5, and cooled to obtain an iron lump.

(Comparative Example 2-1)
Except that the melting by plasma was not performed, the others were dissolved in a hydrochloric acid solution and brought into contact with an anion exchange resin in the same manner as in Example 1-3, and then heated to obtain iron. At that time, the electrolytic iron used as the raw material was the electrolytic iron used in Examples 2-1 to 2-6.

[Analysis of impurity concentration]
For the iron obtained in Examples 2-1 to 2-7 and Comparative Example 2-1, the concentration of impurities was analyzed by glow discharge mass spectrometry in the same manner as in Examples 1-1 to 1-3. . The obtained results are shown in Tables 2 and 3.

  As can be seen from Table 2, according to Examples 2-1 to 2-6, the same results as in Examples 1-1 and 1-2 were obtained. That is, even if a mixture of iron containing impurities and iron oxide is melted, the concentration of aluminum, calcium, chromium, niobium, silicon, titanium, zirconium can be reduced, and an atmosphere containing active hydrogen It was possible to reduce the oxygen concentration by melting with plasma below. Further, as can be seen from Table 3, by bringing the aqueous chloride solution into contact with the anion exchange resin, the concentrations of cobalt, copper and nickel could be reduced. Furthermore, the concentration of aluminum and silicon could be reduced by melting a mixture of iron obtained by bringing an aqueous chloride solution into contact with an anion exchange resin and heating it and iron oxide.

(Example 3-1)
The surface of the electrolytic iron lump was heated in an oxygen atmosphere to oxidize the surface to obtain iron on which an iron oxide layer was formed. At that time, the flow rate of oxygen gas was 0.5 liters per minute, and heating was performed at 500 ° C. for 8 hours. In the obtained iron, the oxygen content was about 1% by mass. Only iron gas was supplied without supplying oxygen gas, and this iron was melted by plasma, and the slag layer was removed to obtain an iron lump. Other melting conditions using plasma were the same as in Example 1-1.

(Example 3-2)
The iron lump obtained in Example 3-1 was melted by plasma while supplying hydrogen gas in the same manner as in Example 1-2, and cooled to obtain an iron lump.

(Example 3-3)
The electrolytic iron used in Examples 3-1 and 3-2 was dissolved in a hydrochloric acid solution and brought into contact with an anion exchange resin in the same manner as in Example 1-3, and then heated to obtain iron.

  The obtained iron was oxidized in the same manner as in Example 3-1, and then melted by plasma, and the slag layer was removed to obtain an iron lump.

  The obtained iron lump was melted by plasma while supplying hydrogen in the same manner as in Example 3-2 and cooled to obtain an iron lump.

[Analysis of impurity concentration]
The iron obtained in Examples 3-1 to 3-3 was analyzed for impurity concentration by glow discharge mass spectrometry in the same manner as in Examples 1-1 to 1-3. The obtained results are shown in Table 4 together with the results of Comparative Example 2-1.

  As can be seen from Table 4, according to Examples 3-1 to 3-3, the same results as in Examples 1-1 to 1-3 were obtained. That is, even if the surface of iron containing impurities is oxidized and then melted, the concentration of aluminum, calcium, chromium, niobium, silicon, titanium, zirconium can be reduced, and an atmosphere containing active hydrogen It was possible to reduce the oxygen concentration by melting with plasma below. Moreover, the concentration of cobalt, copper and nickel could be reduced by bringing the aqueous chloride solution into contact with the anion exchange resin. Furthermore, the concentration of aluminum and silicon could be reduced by oxidizing the surface of the iron obtained by bringing the aqueous chloride solution into contact with the anion exchange resin and heating it, followed by melting.

(Example 4-1)
In Example 1-1, the electrolytic iron shown in Table 1 was replaced with the electrolytic cobalt shown in Table 2, and in the same manner as in Example 1-1, melting was performed by plasma while supplying oxygen, and a lump of cobalt was obtained. Got.

(Example 4-2)
The cobalt lump obtained in Example 4-1 was melted by plasma while supplying hydrogen in the same manner as in Example 1-2 to obtain a cobalt lump. A hydrogen partial pressure of 20 kPa (hydrogen capacity is 20% by volume) was used as the plasma generation gas.

(Example 4-3)
The electrolytic cobalt as shown in Table 5 as a raw material, which cobalt concentration is dissolved at a ^{0.34kmol / m 3 (20g / dm} 3) in hydrochloric acid solution of concentration 1.5kmol / m ^3, aqueous solution of cobalt chloride M3 Was made. Next, as shown in FIG. 6, powdered cobalt 11 was put into this cobalt chloride aqueous solution M3 and stirred while blowing an inert gas to make copper a monovalent ion. Subsequently, as shown in FIG. 7, the cobalt chloride aqueous solution M3 was brought into contact with the anion exchange resin 21 to adsorb copper and separated from the cobalt chloride aqueous solution M3.

After separating the copper, the hydrochloric acid concentration in the cobalt chloride aqueous solution M3 was set to 9 kmol / m ³ , the cobalt chloride aqueous solution M3 was brought into contact with the anion exchange resin 21 to adsorb cobalt, and separated from impurities such as titanium. Thereafter, cobalt was eluted from the anion exchange resin 21 with a hydrochloric acid solution having a concentration of 4 kmol / m ³ and separated from impurities such as molybdenum.

  After the cobalt was eluted from the anion exchange resin 21, the obtained aqueous solution of cobalt chloride M3 was evaporated to dryness on heat-resistant glass to obtain cobalt chloride or a hydrate thereof (step S226). After that, as shown in FIG. 13, the obtained cobalt chloride or hydrate thereof was placed in a quartz boat and heated at 743 K in a hydrogen atmosphere to obtain cobalt.

  The obtained cobalt was melted by plasma while supplying oxygen in the same manner as in Example 4-1, and the slag layer was removed to obtain a cobalt lump.

  The obtained iron lump was melted by plasma while supplying hydrogen in the same manner as in Example 4-2, and cooled to obtain an iron lump.

[Analysis of impurity concentration]
The iron obtained in Examples 4-1 to 4-3 was analyzed for impurity concentration by glow discharge mass spectrometry in the same manner as in Examples 1-1 to 1-3. The results obtained are shown in Table 5.

  As can be seen from Table 5, the concentration of aluminum, calcium, iron, chromium, niobium, silicon, titanium, and zirconium could be reduced by melting with plasma in an atmosphere containing active oxygen. In addition, the oxygen concentration could be reduced by melting with plasma in an atmosphere containing active hydrogen. In addition, the concentration of copper and nickel could be reduced by bringing the aqueous chloride solution into contact with the anion exchange resin. Furthermore, the aluminum and silicon concentrations could be reduced by bringing the aqueous chloride solution into contact with the anion exchange resin and then melting it with plasma in an atmosphere containing active oxygen.

(Example 5-1)
A mixture obtained by mixing 54 g of electrolytic cobalt and 1 g of high-purity cobalt oxide (CoO) was melted by plasma by supplying only argon gas without supplying oxygen gas.

  After starting the melting, it was observed that the mixed slag layer of cobalt oxide and impurity oxide moved to the surface of the molten electrolytic cobalt. This slag layer maintained a constant area over time and did not increase or decrease. This melting was carried out for a total of 10 minutes in order to more reliably oxidize the impurities. Then, the melted electrolytic cobalt was cooled, and a lump of cobalt was taken out from the melting chamber 1.

By immersing the mass of the extracted cobalt 2kmol / m ³ or more 5kmol / m ³ or less of hydrochloric acid solution, grinding the slag layer on the surface chemically to give a mass of cobalt to completely remove the slag layer.

(Example 5-2)
The cobalt lump obtained in Example 5-1 was melted by plasma while supplying hydrogen in the same manner as in Example 1-2, and cooled to obtain a cobalt lump. A hydrogen partial pressure of 20 kPa (hydrogen capacity is 20% by volume) was used as the plasma generation gas.

(Example 5-3)
The electrolytic cobalt used in Example 5-1 was dissolved in a hydrochloric acid solution and brought into contact with an anion exchange resin in the same manner as in Example 4-3, and then heated to obtain cobalt.

  In the same manner as in Example 5-1, the obtained cobalt was added with high-purity cobalt oxide and melted by plasma, and the slag layer was removed to obtain a cobalt lump.

  The obtained cobalt lump was melted by plasma while supplying hydrogen in the same manner as in Example 5-2, and cooled to obtain a cobalt lump.

[Analysis of impurity concentration]
The cobalt obtained in Examples 5-1 to 5-3 was analyzed for impurity concentration by glow discharge mass spectrometry in the same manner as in Examples 1-1 to 1-3. The results obtained are shown in Table 6.

  As can be seen from Table 6, according to Examples 5-1 to 5-3, the same results as in Examples 4-1 to 4-3 were obtained. That is, even when a mixture of cobalt containing impurities and cobalt oxide is melted, the concentration of aluminum, calcium, iron, chromium, niobium, silicon, titanium, zirconium can be reduced, and active hydrogen can be reduced. It was possible to reduce the concentration of oxygen by melting with plasma in a contained atmosphere. Moreover, the concentration of copper and nickel could be reduced by bringing the aqueous chloride solution into contact with the anion exchange resin. Furthermore, the concentration of aluminum and silicon could be reduced by melting a mixture of cobalt obtained by contacting a chloride aqueous solution with an anion exchange resin and heating it and cobalt oxide.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, although the plasma arc melting furnace is used in the above embodiment, an arc melting furnace may be used.

  The high-purity iron and high-purity iron target and the high-purity cobalt and high-purity cobalt target of the present invention can be used as materials for a conductor device, a magnetic recording medium, a magnetic recording head, or a device using an environmental semiconductor.

It is a figure for demonstrating the manufacturing process of the high purity iron which concerns on one embodiment of this invention, a high purity iron target, high purity cobalt, and a high purity cobalt target. It is a figure showing an example of a plasma arc melting furnace. It is a figure showing the oxygen potential of the oxide of the main metal element. It is a figure for demonstrating the other manufacturing process of the high purity iron which concerns on one embodiment of this invention, and a high purity iron target. It is a flowchart showing the manufacturing process of step S200 of FIG. It is a figure for demonstrating one manufacturing process shown in FIG. It is a figure for demonstrating another one manufacturing process shown in FIG. It is a 1st characteristic view showing the change of the metal ion concentration in the elution liquid of an anion exchange resin. It is a 2nd characteristic view showing the change of metal ion concentration in the eluate of an anion exchange resin. It is a figure for demonstrating the other manufacturing process of the high purity cobalt which concerns on one embodiment of this invention, and a high purity cobalt target. It is a 3rd characteristic view showing the change of the metal ion concentration in the eluate of an anion exchange resin. It is a 4th characteristic view showing the change of metal ion concentration in the eluate of an anion exchange resin. It is a figure for demonstrating one manufacturing process shown in FIG. It is a specific figure showing the relationship between the heating temperature of cobalt chloride, and the reaction rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Melting chamber, 2 ... Plasma torch, 3 ... Crucible, 4 ... Power supply, 5 ... Gas supply source, 11 ... Metal, 12 ... Container, 13 ... Inert gas, 14 ... Stirrer, 21 ... Anion exchange resin, 22 ... Column, 23 ... Storage tank, 24 ... Recovery tank, 31 ... Heating furnace, 32 ... Reaction tube, 33 ... Hydrogen gas, 34 ... Processing section.

Claims (20)

  High-purity iron characterized in that the concentration of oxygen as an impurity is 1 mass ppm or less.   The high-purity iron according to claim 1, wherein the total concentration of impurities such as aluminum, calcium, chromium, niobium, silicon, titanium and zirconium is 50 mass ppm or less.   Furthermore, the total of the density | concentration of cobalt, copper, and nickel which are impurities is 1 mass ppm or less, The high purity iron of Claim 1 characterized by the above-mentioned.   A high-purity iron target characterized in that the concentration of oxygen as an impurity is 1 mass ppm or less.   The high-purity iron target according to claim 4, wherein the total concentration of impurities aluminum, calcium, chromium, niobium, silicon, titanium and zirconium is 50 ppm by mass or less.   Furthermore, the total of the density | concentration of cobalt, copper, and nickel which are impurities is 1 mass ppm or less, The high purity iron target of Claim 4 characterized by the above-mentioned.   High-purity cobalt, characterized in that the concentration of oxygen as an impurity is 1 mass ppm or less.   The high-purity cobalt according to claim 7, wherein the total concentration of impurities such as aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium is 50 mass ppm or less.   Furthermore, the high concentration cobalt of Claim 7 whose sum total of the density | concentration of copper and nickel which are impurities is 1 mass ppm or less.   A high-purity cobalt target, wherein the concentration of oxygen as an impurity is 1 mass ppm or less.   The high-purity cobalt target according to claim 10, wherein the total concentration of impurities aluminum, calcium, chromium, iron, niobium, silicon, titanium and zirconium is 50 ppm by mass or less.   The high-purity cobalt target according to claim 10, wherein the total concentration of copper and nickel as impurities is 1 mass ppm or less. At least one impurity selected from the group consisting of aluminum, calcium, chromium, iron, niobium, silicon, titanium, and zirconium, in which a metal containing impurities is melted and oxygen is dissolved or coexists with a molten oxide of the metal. A method for producing a high-purity metal, comprising the step of oxidizing the metal to reduce the concentration of these impurities.   The method for producing a high purity metal according to claim 13, wherein the metal containing impurities is melted by plasma in an atmosphere containing active oxygen.   The method for producing a high-purity metal according to claim 14, wherein the metal containing impurities is melted while supplying a plasma generating gas containing oxygen at a partial pressure of 0.1 Pa or more and 10 kPa or less.   The method for producing a high-purity metal according to claim 14, wherein the metal containing the impurities is melted under a pressure of 1.33 kPa to 310 kPa.   14. The method for producing a high-purity metal according to claim 13, wherein an oxide of the metal is added to the metal containing impurities and melted.   14. The method for producing a high-purity metal according to claim 13, wherein a part of the metal containing impurities is oxidized and then melted. Further, a metal containing impurities is melted by plasma in an atmosphere containing active hydrogen, and the active hydrogen is reacted with at least one impurity selected from the group consisting of oxygen, nitrogen and carbon, and the concentration of these impurities is increased. The method for producing a high-purity metal according to claim 13, further comprising: Further, a metal containing an impurity is dissolved in a hydrochloric acid aqueous solution to prepare a metal chloride aqueous solution. After adjusting the concentration of hydrochloric acid in the aqueous chloride solution, the metal is brought into contact with an anion exchange resin to reduce the impurity concentration. The method for producing a high-purity metal according to claim 13, comprising a step.

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