WO2015045754A1 - 高純度In及びその製造方法 - Google Patents
高純度In及びその製造方法 Download PDFInfo
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- WO2015045754A1 WO2015045754A1 PCT/JP2014/073027 JP2014073027W WO2015045754A1 WO 2015045754 A1 WO2015045754 A1 WO 2015045754A1 JP 2014073027 W JP2014073027 W JP 2014073027W WO 2015045754 A1 WO2015045754 A1 WO 2015045754A1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
- C25C1/22—Electrolytic production, recovery or refining of metals by electrolysis of solutions of metals not provided for in groups C25C1/02 - C25C1/20
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B58/00—Obtaining gallium or indium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
- C25C7/04—Diaphragms; Spacing elements
Definitions
- the present invention provides a high-purity indium (In) having a purity of 7N or more that is particularly useful as a raw material for indium phosphide (InP), and a method for producing the same, and is manufactured at a lower cost than the prior art.
- the present invention relates to a method for producing high-purity In by electrolytic purification, which has a feature that it can be performed.
- high-purity raw materials are used for the production of a compound semiconductor single crystal such as InP, which is one of Group 3-5 compound semiconductors.
- Distillation and zone purification are used for the production of high-purity In. It is refine
- Patent Document 1 it is distilled at 1250 ° C.
- Patent Document 2 it is zone-melted after baking
- Patent Document 3 it is distilled by reacting with chlorine gas, and In chloride is distilled with distilled water.
- Patent Document 4 describes a method of continuously casting In distilled.
- Patent Document 5 describes a method for purifying In.
- the unit notation of “ppm” used in the present invention means “wtppm” hereinafter.
- Crude In containing less than 10 ppm of Cd and less than 1 ppm of Tl is used as a raw material, and this is used as an anode in a hydrochloric acid bath. In concentration: 100 to 300 g / L, pH: 0.5 to 2, Current density: 0.5 to 2 A Electrolytic purification is performed at / dm 2 .
- the anode chamber and the cathode chamber are separated by a diaphragm and subjected to electrolytic purification.
- the electrolyte solution in the anode chamber is extracted, filtered, and then contacted with an anion exchange resin for purification. Further, noble impurities are removed from In in the electrolytic solution by electrolysis at a current density of 0.3 to 2.5 A / dm 2 , and this is supplied to the cathode chamber for electrolytic purification.
- Examples of the material of the diaphragm include natural fibers such as cotton, and woven and non-woven fabrics of synthetic fibers such as polyethylene, polypropylene, and polyester, and those having sufficiently small holes are preferred. Cloth is used. Regarding the filter, a cartridge filter is used in the embodiment as long as it can be filtered. However, this Patent Document 5 has a problem that it is necessary to use an expensive anion exchange resin and a problem that it is necessary to perform electrolysis to remove impurities for the purification of the electrolytic solution.
- Patent Document 6 describes a method for purifying In. This is considered an improved version of the above-mentioned Patent Document 5.
- the purity is 4 to 5N, but crude In, which has more impurities than Patent Document 5, is used as a raw material, and this is used as an anode, with an In concentration of 100 to 200 g / L, pH: 1.5 to 2.5.
- Electrolytic purification is performed at a current density of 0.5 to 2 A / dm 2 .
- the anode chamber and the cathode chamber are separated by a diaphragm and subjected to electrolytic purification.
- electrolytic purification After the electrolysis, the electrolyte solution in the anode chamber is extracted and brought into contact with an anion exchange resin for purification. Further, by removing the current density from 0.3 to 2.5 A / dm 2 and contacting the metal In with the electrolytic solution, impurities more precious than In in the electrolytic solution are removed, and this is supplied to the cathode chamber.
- Electrolytic purification is performed.
- a method of supplying In ions to the electrolytic solution by diaphragm electrolysis using a ceramic filter or the like is also described.
- Examples of the material of the diaphragm include natural fibers such as cotton, and woven fabrics and nonwoven fabrics of synthetic fibers such as polyethylene, polypropylene, and polyester, and those having sufficiently small through holes are preferable.
- Tetron filter cloth is used.
- a cartridge filter is used so that the filtration can be performed as necessary.
- this Patent Document 6 has a problem that an expensive anion exchange resin must be used and a problem that it is necessary to perform electrolysis to remove impurities for cleaning the electrolytic solution. is there.
- Patent Document 7 describes high-purity metal In, a method for producing the same, and uses.
- the specific contents are as follows. Purification is performed by removing residual volatiles by blowing an inert gas when casting the electrodeposited In obtained by the second stage of electrolytic purification. The achieved purity of Patent Document 7 is assumed to be “6N level”.
- Electrolysis may be a hydrochloric acid bath or a sulfuric acid bath, and an In concentration of 20 to 80 g / L and a pH of 1.0 to 2.5 are preferable, and no diaphragm is used.
- the total current density of the first electrolysis and the second electrolysis is 100 to 500 A / m 2 (1 to 5 A / dm 2 ), and the current density of the second electrolysis is lower than that of the first electrolysis.
- Na hydroxide or a mixture of Na hydroxide and nitrate is added as a flux so that Cl is 0.03 ppm or less and S is 0.01 ppm or less.
- Example 1 is a result of no inert gas blowing
- Example 2 is a result of blowing an inert gas
- Examples 3 to 5 are a result of blowing an inert gas using a flux.
- This patent document 7 has a problem of high cost due to electrolysis in two stages, and it is necessary to perform casting for producing an anode between the first stage and the second stage, and the process becomes complicated. There is a problem.
- Patent Document 8 in the purification method of In, an electrolytic solution is extracted from the anode chamber, and after filtration, the electrolytic solution is contacted with an anion exchange resin, and the electrolyte is separated into an anode chamber and a cathode chamber by a diaphragm.
- a purification method comprising a step of supplying an electrolytic solution to the cathode chamber of the liquid tank is described. Also in this case, there is a problem that an expensive anion exchange resin must be used and a problem that it is necessary to perform electrolysis to remove impurities for the purification of the electrolytic solution. And the purity achieved is only 6N level.
- Patent Document 9 an In-containing material is dissolved with hydrochloric acid, and an alkali is added to the solution to neutralize the solution to a predetermined value within the range of 0.5 to 4. Then, the metal ions are precipitated and removed as hydroxides, and then hydrogen sulfide gas is blown into the metal ions, and the metal ions harmful to the electrolysis in the next step are precipitated and removed as sulfides. In metal is electrolytically purified.
- Patent Document 10 discloses a method for producing high-purity strontium carbonate used in the present invention, which will be described later, and is posted for reference.
- JP 2002-212647 A Japanese Patent Laid-Open No. 04-026728 Japanese Patent Laid-Open No. 01-156437 JP-A-10-121163 Japanese Patent Laid-Open No. 01-031988 JP-A-01-219186 JP 2005-179778 A JP-A 64-31988 JP 2007-131953 A JP-A-9-77516
- An object of the present invention is to provide a high-purity In having a purity of 7N or more that is particularly useful as a raw material for InP and a method for producing the same, and further by electrolytic purification that can be produced at a lower cost than the prior art. It is an object to provide a manufacturing method. There is a possibility that In demand for LEDs such as InGaN and AlInGaP will increase, and it will be required to manufacture in large quantities at low cost in the future. The present invention provides a technology that can cope with this.
- the present application provides the following inventions.
- the analytical values of each element concentration are values analyzed by a GDMS (Glow Discharge Mass Spectrometry) method.
- Pb 0.05 ppm or less
- Zn 0.005 ppm or less
- S 0.02 ppm or less
- high-purity having a purity of 7N (99.99999%) or more.
- High purity In as described in 1) above, wherein Fe: 0.001 ppm or less, Sn: less than 0.01 ppm, and Si: less than 0.005 ppm.
- the present application also provides the following invention.
- a method for producing high purity In in which 5N (99.999%) In is used as a raw material, and when electrolytic purification is performed using this raw material, SrCO 3 is added to the electrolytic solution for electrolysis. The content of Pb in the liquid is reduced, and the electrodeposited In is peeled off from the cathode plate and cast in the air or in an oxygen-containing gas atmosphere to have a purity of 7N (99.99999%) or more.
- the anolyte (anolyte) and catholyte (catholyte) are partitioned by a breathable membrane of 5 cm 3 / cm 2 sec or less, and the electrolyte in contact with the cathode is filtered through a filter having pores of 0.5 ⁇ m or less in advance.
- a method for producing high-purity In by electrolytic purification in which an anolyte (anolyte) and a catholyte (catholyte) are partitioned by a breathable diaphragm of 5 cm 3 / cm 2 sec or less, The part was taken out into a catholyte tank different from the electrolytic cell, and Pb in the catholite was removed by adding SrCO 3 to the catholite in the catholite tank, and the catholite from which the Pb had been removed had a pore size of 0.5 ⁇ m or less.
- a method for producing high-purity In characterized in that, after passing through a filter and filtering, electrolytic purification is performed while circulating supply so as to return to the cathode box in the electrolytic cell again.
- the present application also provides the following invention.
- (7) The method for producing high-purity In according to any one of (3) to (6) above, wherein electrolysis is performed at a current density of 1 to 5 A / dm 2 .
- Electrolysis is performed at an In concentration of 65 to 120 g / L in an electrolytic solution and a Cl concentration of 6 to 10 g / L.
- (9) The method for producing high-purity In according to any one of (3) to (8) above, wherein SrCO 3 is purified by adding 0.1 to 2.0 g / L.
- the present invention has an excellent effect capable of providing a high purity In having a purity of 7N or more which is particularly useful as a raw material for InP and a method for producing the same.
- the production method by electrolytic purification of the present invention is characterized in that it can be produced at a lower cost than the prior art.
- the demand for In for LEDs such as InGaN and AlInGaP is growing rapidly, and it will be required to manufacture in large quantities at low cost in the future.
- the present invention can provide a technology that can cope with this demand.
- In which is a raw material for InP compound semiconductors
- In has been purified by a dry method in which, for example, 4N of In is baked (1000 ° C.) and distilled (1050 ° C.) to 6N.
- the dry method requires equipment costs and manufacturing costs, and in order to increase the production of high purity In of 7N or more, it is necessary to repeat the baking step and the distillation step a plurality of times, which requires a large amount of equipment investment. Therefore, it was examined whether high-purity In that could be used for InP was obtained by wet purification.
- the target purity was set to 7N or more, and the test was conducted by electrolytic purification in a sulfuric acid bath.
- a titanium (Ti) metal plate serving as a cathode plate is disposed in an electrolytic cell (battery cell), and an In ingot of purity 5N is disposed on the anode.
- a cathode box having a filter cloth serving as a partition is disposed between the cathode and the anode, and both electrode plates are partitioned.
- JIS L 1096 which is air permeability
- a filter cloth having an air permeability of 5 cm 3 / cm 2 sec or less is used at 124.5 Pa.
- a catholyte tank is disposed outside the electrolytic cell, and a part of the electrolyte solution in the cathode box is introduced into the catholyte tank, and SrCO 3 is added thereto.
- lead (Pb) contained in the catholite is precipitated as PbCO 2 —O—CO 2 Sr at the bottom of the catholyte tank, and the catholite from which Pb has been removed is placed in the cathode box in the battery case. By returning, the Pb-removed catholyte is circulated and used.
- the catholite from which Pb has been removed in the catholyte tank is filtered through a filter having pores of 0.5 ⁇ m or less and purified, thereby preventing Pb from being mixed into the cathode box.
- the pores of the filter are more preferably 0.2 ⁇ m.
- As the raw material In 5N (99.999%) In is used as the anode. 5N level In can be easily produced by using the distillation method alone, and commercially available materials can be used.
- the main impurities of 5N In produced by using the distillation method alone are Pb (lead), Zn (zinc), and Sn (tin), and in particular, Pb contains about 1 ppm. Impurities such as Sn, Fe (iron), and Ni (nickel) can be reduced by the electrolytic purification method, but the most problematic is the removal of Pb, and the simple removal of Pb is a major issue. .
- a sulfuric acid solution is used in the electrolytic purification process, and S (sulfur) in the 5N In raw material produced by the distillation method is 0.005 ppm. In order to produce 7N In, it is necessary to reduce the S content after electrolytic purification.
- Zn was also contained in the 5N In raw material produced by the above-described distillation method in an amount of 0.1 ppm Zn, which could be reduced to 0.05 ppm after electrolytic purification, but in order to produce 7N In. It must be further reduced.
- Electrolytic purification is carried out in a sulfuric acid solution, and the cathode box is arranged so as to surround the cathode, and the cathode box is coated with a filter cloth on the surface facing the anode plate to prevent confusion of impurities in anolyte and catholyte. I did it.
- the filter cloth used had a breathability of 5 cm 3 / cm 2 sec or less, more preferably 1 cm 3 / cm 2 sec or less.
- 5N In is arranged outside the cathode box.
- a catholyte tank is disposed outside the electrolytic cell, and a part of the catholyte in the cathode box is introduced into the catholyte tank, and SrCO 3 is added thereto.
- the electrolytic solution is sulfuric acid and electrolysis is performed at a pH of 0.5 to 1.5. If the pH is less than 0.5, the current efficiency decreases due to hydrogen generation, and if the pH exceeds 1.5, the electrolysis voltage increases. Furthermore, electrolysis is performed at a current density of 1 to 5 A / dm 2 . This poor productivity is less than 1A / dm 2, is because the the electrolysis voltage exceeds 5A / dm 2 becomes high. In addition, dendrites are easily generated, and impurities more precious than In are easily deposited on the cathode in electrolytic purification.
- Electrolysis is performed at an In concentration of 65 to 120 g / L and a Cl concentration of 6 to 10 g / L in the electrolyte solution (catholyte) in contact with the cathode.
- the In concentration is less than 65 g / L
- current efficiency decreases due to hydrogen generation particularly in electrolytic refining, and when it exceeds 120 g / L, the in-process inventory of expensive In increases.
- the Cl concentration is less than 6 g / L, the electrodeposition of In is deposited on the dendrite and the diaphragm is damaged.
- it is not a big problem even if it exceeds 10 g / L since it will affect the corrosion of a peripheral device and the lifetime of an apparatus will become short, it is not preferable.
- 0.1-2.0 g / L is added to the catholyte in the catholite tank to precipitate Pb as PbCO 2 —O—CO 2 Sr at the bottom of the catholite tank.
- the catholyte in the catholyte tank in which Pb is precipitated is returned to the electrolyte in the cathode box through a filter having a pore size of 0.5 ⁇ m or less so as not to contain PbCO 2 —O—CO 2 Sr. Is used cyclically.
- the raw material In used as the anode is dissolved in the electrolytic solution (anolyte).
- the electrolytic solution anolyte
- impurities more precious than In do not electrodeposit on the cathode and remain on the anode surface or are mixed as fine floating substances in the electrolyte, but if they become floating substances, they are electrodeposited on the cathode.
- a partition wall having sufficiently small pores between the anode and the cathode.
- the cathode reaction is as follows. In 3+ + 3e ⁇ In Filter cloth membrane (anode chamber) In 3+ ⁇ In 3+ (cathode chamber)
- the anodic reaction is as follows. In ⁇ In 3+ + 3e (Trace) Pb ⁇ Pb 2+ + 2e (Catholite room (tank)) Pb 2+ + SrCO 2 —O—CO 2 Sr ⁇ PbCO 2 —O—CO 2 Sr + Sr 2+
- Pb 2+ precipitates as PbCO 2 —O—CO 2 Sr by the addition of SrCO 3 , and thus can be removed.
- the catholyte is further introduced into the catholyte tank, and the In eluted in the anolyte is deposited on the Ti electrode, so that In having a purity of 6N or more can be obtained.
- Impurities of SrCO 3 introduced into the catholyte tank are Si: 0.51 ppm, S: 4.9 ppm, Ca: 50 ppm, Fe ⁇ 0.5 ppm, Ni ⁇ 05 ppm, Pb ⁇ 0.1 ppm. Since it is diluted, the amount actually mixed into In is reduced as shown in the examples described later. Since the technology for increasing the purity of SrCO 3 is disclosed in Patent Document 10 (Japanese Patent Laid-Open No. 9-77516), the purification can be easily achieved.
- Pb 0.05 ppm or less
- Zn 0.05 ppm or less
- S 0.05 ppm or less
- high purity In having a purity of 6N (99.9999%) or more can be obtained. It becomes possible. Furthermore, in the above, high purity In which is Fe: 0.001 ppm or less, Sn: less than 0.01 ppm, and Si: less than 0.005 ppm can be obtained.
- FIG. 1 shows an example in which sulfuric acid is used.
- Japanese Patent Laid-Open No. 08-060264 Japanese Patent No. 3089595
- the electrodeposited In is peeled off from the cathode, and melted and cast at 170 to 190 ° C. to produce an ingot.
- this melting and casting is performed in the atmosphere or in an oxygen-containing gas atmosphere, Zn and S oxides are formed and separated and removed from In in a solid or gas state.
- Zn in In can be made 0.005 ppm or less
- S in In can be made 0.01 ppm or less.
- the oxygen-containing gas a mixed gas of high purity argon and high purity oxygen, oxygen-enriched air, or the like can be used.
- Example 1 As Example 1, electrolytic purification using a sulfuric acid bath (using the apparatus shown in FIG. 1) will be described. Between the anolyte and catholyte partitioned by the cathode box, a filter cloth with air permeability of 5 cm 3 / cm 2 sec or less is arranged to prevent impurities such as suspended solids existing in the anolyte from entering the catholyte side. .
- the content of impurities of SrCO 3 added to the catholyte tank was Si: 0.51 ppm, S: 4.9 ppm, Ca: 50 ppm, Fe ⁇ 0.5 ppm, Ni ⁇ 05 ppm, Pb ⁇ 0.1 ppm.
- SrCO 3 was added SrCO 3 into the catholyte during catholyte tank at a concentration of 0.5 g / L, the catholyte was removed Pb, through the following filter pores 0.5 [mu] m, again Electrolytic purification was performed while circulatingly feeding back to the cathode box.
- Table 1 shows the results of separating the electrodeposited In after electrolytic purification from the cathode Ti electrode plate and analyzing impurities.
- the impurities in In after electrolytic purification could be reduced to Pb: 0.02 ppm, Sn: less than 0.01 ppm (below the detection limit), Ni: 0.006 ppm, and Fe: 0.001 ppm.
- Zn could also be reduced to 0.05 ppm, but with this content, 7N purity could not be achieved, and S was 0.005 ppm in the 5N In raw material produced by the distillation method. After the electrolytic purification, it increases to 0.05 ppm and must be reduced in order to produce 7N In.
- impurities in In after casting were Na: 0.001 ppm, Si: less than 0.005 ppm (less than detection limit), Ca: 0.005 ppm, Fe: less than 0.001 ppm ( Less than the detection limit), Ni: 0.002 ppm, Sn: less than 0.01 ppm (less than the detection limit), and Pb: 0.02 ppm, which are maintained at the content after electrolytic purification.
- Zn and S react with atmospheric oxygen during casting to form an oxide, and in particular, Zn forms an oxide (slag) to form a solid (floating matter) and is dissolved in In It was separated and removed from, or S became a sulfur oxide gas, and was separated and removed from dissolved In, thereby reducing Zn to 0.005 ppm and S to 0.01 ppm.
- Example 1 as impurities other than the above, Li, Be, B, F, Mg, Al, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Sb, Te, I, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Bi, Th, and U are contained in GDMS. These elements are excluded because they are below the detection limit. The same applies to the following embodiments.
- both impurities were reduced by electrolytic purification and casting treatment.
- 5N In produced by using the distillation method alone was used as the anode raw material.
- Impurities such as Pb, Zn, Sn, Fe, Ni which are main impurities and S mixed from the sulfuric acid solution used in the electrolytic purification process can be reduced, and 7N purity In can be produced. Also, the yield was 98% or more in all cases.
- Comparative Example 1 electrolytic purification of In was performed under the same conditions as in Example 1 except that the step of adding SrCO 3 into the electrolyte solution in the catholyte tank in Example 1 was eliminated. And cast at a molten metal temperature of 170 ° C. The results are shown in Table 2.
- Pb contained 0.5 ppm, S: 0.03 ppm, and Zn: 0.02 ppm, and a purity of 7N could not be achieved. About other impurities, it was able to be reduced to content equivalent to Example 1.
- FIG. 1 Comparative Example 1
- Example 2 In Example 2, the concentration of SrCO 3 added to the catholyte tank was set to 0.1 g / L, the In concentration in the catholyte: 65 g / L, pH: 0.5, the current density: 1 A / dm 2 , Cl in the catholyte. The concentration was 6 g / L. The major difference from Example 1 is that the additive concentration of SrCO 3 in the catholyte was made lower than that of Example 1.
- Impurities of SrCO 3 introduced into the catholyte tank were Si: 0.51 ppm, S: 4.9 ppm, Ca: 50 ppm, Fe ⁇ 0.5 ppm, Ni ⁇ 05 ppm, Pb ⁇ 0.1 ppm.
- Table 3 shows the results of impurity concentration in In after electrolytic refining under the above-mentioned conditions and then casting electrodeposited In at 170 ° C.
- Example 3 As Example 3, the concentration of SrCO 3 added to the catholyte tank was 2.0 g / L, the In concentration in the catholyte: 120 g / L, pH: 1.5, the current density: 5 A / dm 2 , Cl in the catholyte. The concentration was 10 g / L. The major difference from Examples 1 and 2 is that the additive concentration of SrCO 3 in the catholyte was made higher than that in Example 1.
- Impurities of SrCO 3 introduced into the catholyte tank were Si: 0.51 ppm, S: 4.9 ppm, Ca: 50 ppm, Fe ⁇ 0.5 ppm, Ni ⁇ 05 ppm, Pb ⁇ 0.1 ppm.
- Table 4 shows the result of impurity concentration in In after electrolytic refining under the above conditions and then casting the electrodeposited In at 190 ° C.
- Pb 0.05 ppm or less
- Zn 0.005 ppm or less
- S 0.02 ppm or less
- SrCO 3 is added to the electrolytic solution to reduce Pb, and a purity of 7N (99.99999%) or higher is produced.
- a method is provided.
- In demand for LEDs such as InGaN and AlInGaP will increase, and it will be required to manufacture in large quantities at low cost in the future.
- the present invention provides a technology that can cope with this. Furthermore, compared with the dry refining method, an effective equipment cost is not required, and the running cost can be reduced, so that the cost can be reduced.
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Abstract
Description
下記特許文献1には、1250℃で蒸留することが、特許文献2には、ベーキング後にゾーンメルトすることが、特許文献3には、塩素ガスと反応させて蒸留し、塩化Inを蒸留水と不均化反応させることが、特殊な例として特許文献4に蒸留したInを連続して鋳造する方法が記載されている。
尚、本発明で使用する「ppm」の単位表記は、以下、「wtppm」を意味する。
Cdを10ppm未満、かつTlを1ppm未満含有する粗Inを原料として、これをアノードとして塩酸浴でIn濃度:100~300g/L、pH:0.5~2、電流密度:0.5~2A/dm2で電解精製を行っている。
隔膜によって陽極室と陰極室を分けて電解精製を行い、電解後は陽極室の電解液を抜き取って濾過後、陰イオン交換樹脂と接触させることにより浄液を行っている。更に電流密度 0.3~2.5A/dm2での電解により電解液中のInより貴な不純物を除去し、これを陰極室に供給して電解精製を行っている。
フィルターについては、濾過ができれば良いという程度で、実施例ではカートリッジフィルターを使用している。
しかし、この特許文献5は、高価な陰イオン交換樹脂を使用しなければならないという問題及び電解液の浄液のため、不純物を除去する電解を行う必要があるという問題がある。
濾過については必要に応じて行うこともできるという程度で、実施例ではカートリッジフィルターを使用している。
しかし、この特許文献6は、特許文献5と同様に、高価な陰イオン交換樹脂を使用しなければならないという問題及び電解液の浄液のため不純物を除去する電解を行う必要があるという問題がある。
2段階の電解精製を行い、2段目の電解精製で得られた電析Inを鋳造する際に不活性ガスを吹き込むことで残留揮発分を除去することにより精製を行っている。この特許文献7の達成純度は「6N水準」であるとしている。
尚、本発明において、ガス成分元素であるC(炭素)、N(窒素)、O(酸素)を除き、各元素濃度の分析値は、GDMS(Glow Discharge Mass Spectrometry)法によって分析した値である。
(1)Pb:0.05ppm以下、Zn:0.005ppm以下、S:0.02ppm以下であり、7N(99.99999%)以上の純度を有する高純度In。
(2)Fe:0.001ppm以下、Sn:0.01ppm未満、Si:0.005ppm未満である上記1)に記載の高純度In。
(3)電解により高純度Inを製造する方法であって、5N(99.999%)のInを原料とし、この原料を用いて電解精製する際に、電解液にSrCO3を添加して電解液中のPbの含有量を低減させ、さらに、電着Inを陰極板から剥離し、大気中もしくは酸素含有ガス雰囲気下で鋳造し、7N(99.99999%)以上の純度とすることを特徴とする高純度Inの製造方法。
(4)アノード液(アノライト)とカソード液(カソライト)を5cm3/cm2sec以下の通気性をもつ隔膜で仕切り、カソードに接する電解液を予め0.5μm以下の細孔を持つフィルターで濾過し、精製することを特徴とする上記3)に記載の高純度Inの製造方法。
(5)電解精製による高純度Inの製造方法であって、アノード液(アノライト)とカソード液(カソライト)を、5cm3/cm2sec以下の通気性を持つ隔膜で仕切り、さらに、カソライトの一部を電解槽とは異なるカソライトタンクに取り出し、カソライトタンク中のカソライトにSrCO3を添加することにより、カソライト中のPbを除去し、該Pbを除去したカソライトを細孔0.5μm以下のフィルターに通液して濾過した後、電解槽中のカソードボックスに再び戻すように循環供給しながら電解精製することを特徴とする高純度Inの製造方法。
(6)電解液を硫酸とし、pH:0.5~1.5で電解することを特徴とする上記3)~5)のいずれか一項に記載の高純度Inの製造方法。
(7)電流密度:1~5A/dm2で電解することを特徴とする上記3)~6)のいずれか一項に記載の高純度Inの製造方法。
(8)電解液中のIn濃度:65~120g/L、Cl濃度:6~10g/Lとして電解することを特徴とする上記3)~7)のいずれか一項に記載の高純度Inの製造方法。
(9)SrCO3を0.1~2.0g/Lを添加して精製することを特徴とする上記3)~8)のいずれか一項に記載の高純度Inの製造方法。
(10)上記3)~9)のいずれか一項に記載の高純度Inの電解精製方法で製造された高純度Inを陰極板から剥離し、大気中もしくは酸素含有ガス雰囲気下で鋳造する際、170~190℃で鋳造することを特徴とする高純度Inの製造方法。
(11)上記3)~10)のいずれか一項に記載の高純度Inの製造方法により、Pb:0.05ppm以下、Zn:0.005ppm以下、S:0.02ppm以下とし、7N(99.99999%)以上の純度とすることを特徴とする高純度Inの製造方法。
これまで、InP化合物半導体の原料であるInは、例えば4NのInをベーキング(1000℃)及び蒸留(1050℃)で6Nとする乾式法により精製されていた。しかし、乾式法は設備コスト及び製造コストがかかり、7N以上の高純度Inを増産するには、ベーキング工程と蒸留工程を複数回繰り返す必要もあり、多額の設備投資が必要である。そこで、湿式精製でInPに使用可能な高純度Inが得られるかを検討した。
また、従来技術では、6N以上という記載はあっても、実際は6NレベルのInしか達成しておらず、さらに高純度化が必要であった。本願発明は、目標純度は7N以上とし、硫酸浴での電解精製による試験を行った。
ここで、該濾布の細孔の規格は通気性というJIS L 1096で規格化されており、本発明では、124.5Paにおいて、5cm3/cm2sec以下の通気性を有する濾布を使用して、アノライト中の浮遊物等の不純物がカソライト中に混入されることを防いでいる。
この処理を行うことによって、カソライト中に含有される鉛(Pb)をPbCO2-O-CO2Srとしてカソライトタンクの底部に沈殿させ、Pbを除去したカソライトを電槽内のカソードボックス内に戻すことで、Pb除去されたカソライトが循環して使用される。
ここで、カソライトタンク内でPb除去されたカソライトは、0.5μm以下の細孔を持つフィルターで濾過され、精製されることで、カソードボックス内へのPbの混入を防いでいる。フィルターの細孔は、0.2μmであることが、より好ましい。
原料となるInは、5N(99.999%)のInをアノードとして使用する。5NレベルのInは蒸留法を単独で用いることにより容易に製造でき、市販品の材料を使用できる。
また、本願発明では、電解精製工程において硫酸溶液を使用しており、前記蒸留法によって製造された5NのIn原料中のS(硫黄)は、0.005ppmであるが、電解精製後に0.05ppmに増加し、7NのInを製造するためには、電解精製後のS分の低減が必要となる。
さらに、Znについても、前記蒸留法で製造された5NのIn原料中にはZnが0.1ppm含有されており、電解精製後0.05ppmに低減できているが、7NのInを製造するためには、さらに低減しなければならない。
この濾布は、上記の通り、通気性5cm3/cm2sec以下、さらに好ましくは1cm3/cm2sec以下のものを使用した。電解槽内にあり、カソードボックスの外側に、5NのInを配置する。電解槽の外側には、カソライトタンクを配置し、カソードボックス内のカソライトの一部をカソライトタンクに導入し、この中にSrCO3を添加する。
さらに、電流密度:1~5A/dm2で電解する。これは、1A/dm2未満では生産性が悪く、5A/dm2を超えると電解電圧が高くなるためである。またデンドライトが発生しやすく、電解精製においてはInよりも貴な不純物がカソードに析出しやすいためである。
カソード反応は、次の通りである。
In3++3e → In
濾布膜
(アノード室)
In3+ → In3+(カソード室)
アノード反応は、次の通りである。
In → In3++3e
(微量)Pb → Pb2++2e
(カソライト室(タンク))
Pb2++SrCO2-O-CO2Sr→PbCO2-O-CO2Sr+Sr2+
さらには、上記において、Fe:0.001ppm以下、Sn:0.01ppm未満、Si:0.005ppm未満である高純度Inを得ることができる。
(実施例1)
実施例1として硫酸浴を用いた電解精製(図1に示す装置を使用)について説明する。カソードボックスで仕切られたアノライトとカソライトの間には、通気性5cm3/cm2sec以下の濾布が配置され、アノライト中に存在する浮遊物等の不純物がカソライト側へ混入することを防止した。なお、電解精製の条件については、カソライト中In濃度:80g/L、pH:1.2、SrCO3:0.5g/L、電流密度:3A/dm2、カソライト中Cl濃度を8g/Lした。
このSrCO3を使用して、カソライトタンク中のカソライトへSrCO3を0.5g/Lの濃度となるように添加し、Pbを除去したカソライトを、細孔0.5μm以下のフィルターを通して、再びカソードボックスへ戻すように循環供給しながら、電解精製を実施した。電解精製後の電析したInをカソードのTi電極板から剥離し、不純物を分析した結果を表1に示す。
次に、比較例1として、上記実施例1において、カソライトタンク内の電解液中へSrCO3を添加する工程を無くしたこと以外は、全て実施例1と同様の条件でInの電解精製を行い、さらに170℃の溶湯温度で鋳造した。
その結果を表2に示す。比較例2の条件で精製されたIn中には、Pbが0.5ppm、S:0.03ppm、Zn:0.02ppm含有しており、7Nの純度を達成することはできなかった。その他の不純物については、実施例1と同等の含有量に低減できていた。(Na:0.001ppm、Si:0.005ppm未満(検出限界未満)、Ca:0.004ppm、Fe:0.001ppm、Ni:0.001ppm、Sn:0.01ppm未満(検出限界未満))。
実施例2として、カソライトタンク中へのSrCO3の添加濃度を0.1g/Lとし、カソライト中In濃度:65g/L、pH:0.5、電流密度:1A/dm2、カソライト中Cl濃度を6g/Lした。実施例1との大きな相違点は、カソライト中のSrCO3の添加濃度を実施例1よりも低濃度にしたことである。
上記の条件で電解精製を行い、その後、電析したInを170℃で鋳造した後のIn中の不純物濃度の結果を表3に示す。
実施例3として、カソライトタンク中へのSrCO3の添加濃度を2.0g/Lとし、カソライト中In濃度:120g/L、pH:1.5、電流密度:5A/dm2、カソライト中Cl濃度を10g/Lした。実施例1、2との大きな相違点は、カソライト中のSrCO3の添加濃度を実施例1よりも高い濃度にしたことである。
上記の条件で電解精製を行い、その後、電析したInを190℃で鋳造した後のIn中の不純物濃度の結果を表4に示す。その結果、Pb:0.01ppmであり、また、Zn:0.005ppm、S:0.01ppmとなり、さらに、その他の不純物も、Na:0.001ppm、Si:0.005ppm未満(検出限界未満)、Ca:0.005ppm、Fe0.001ppm未満(検出限界未満)、Ni:0.002ppm、Sn:0.01ppm未満(検出限界未満)となり、また、上記以外の不純物についてもGDMSで分析したが、実施例1、2と同様に検出下限値未満であり、定量評価できなかった。以上により、7Nの純度を有するInが製造できた。
さらに、乾式精製法に比べて、効果な設備費を必要とせず、またランニングコストも低減できるので、コスト低減を図ることができるという効果を有する。
Claims (11)
- Pb:0.05ppm以下、Zn:0.005ppm以下、S:0.02ppm以下であり、7N(99.99999%)以上の純度を有する高純度In。
- Fe:0.001ppm以下、Sn:0.01ppm未満、Si:0.005ppm未満である請求項1に記載の高純度In。
- 電解により高純度Inを製造する方法であって、5N(99.999%)のInを原料とし、この原料を用いて電解精製する際に、電解液にSrCO3を添加して電解液中のPbの含有量を低減させ、さらに、電着Inを陰極板から剥離し、大気中もしくは酸素含有ガス雰囲気下で鋳造し、7N(99.99999%)以上の純度とすることを特徴とする高純度Inの製造方法。
- アノード液(アノライト)とカソード液(カソライト)を5cm3/cm2sec以下の通気性をもつ隔膜で仕切り、カソードに接する電解液を予め0.5μm以下の細孔を持つフィルターで濾過し、精製することを特徴とする請求項3に記載の高純度Inの製造方法。
- 電解精製による高純度Inの製造方法であって、アノード液(アノライト)とカソード液(カソライト)を、5cm3/cm2sec以下の通気性を持つ隔膜で仕切り、さらに、カソライトの一部を電解槽とは異なるカソライトタンクに取り出し、カソライトタンク中のカソライトにSrCO3を添加することにより、カソライト中のPbを除去し、該Pbを除去したカソライトを細孔0.5μm以下のフィルターに通液して濾過した後、電解槽中のカソードボックスに再び戻すように循環供給しながら電解精製することを特徴とする高純度Inの製造方法。
- 電解液を硫酸とし、pH:0.5~1.5で電解することを特徴とする請求項3~5のいずれか一項に記載の高純度Inの製造方法。
- 電流密度:1~5A/dm2で電解することを特徴とする請求項3~6のいずれか一項に記載の高純度Inの製造方法。
- 電解液中のIn濃度:65~120g/L、Cl濃度:6~10g/Lとして電解することを特徴とする請求項3~7のいずれか一項に記載の高純度Inの製造方法。
- SrCO3を0.1~2.0g/Lを添加して精製することを特徴とする上記請求項3~8のいずれか一項に記載の高純度Inの製造方法。
- 上記請求項3~9のいずれか一項に記載の高純度Inの電解精製方法で製造された高純度Inを陰極板から剥離し、大気中もしくは酸素含有ガス雰囲気下で鋳造する際、170~190℃で鋳造することを特徴とする高純度Inの製造方法。
- 上記請求項3~10のいずれか一項に記載の高純度Inの製造方法により、Pb:0.05ppm以下、Zn:0.005ppm以下、S:0.02ppm以下とし、7N(99.99999%)以上の純度とすることを特徴とする高純度Inの製造方法。
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