U.S. patent application number 10/446427 was filed with the patent office on 2003-11-06 for high purity iron, method of manufacturing thereof, and high purity iron targets.
Invention is credited to Isshiki, Minoru, Kekesi, Tamas, Uchikoshi, Masahito, Yokoyama, Norio.
Application Number | 20030206822 10/446427 |
Document ID | / |
Family ID | 18782856 |
Filed Date | 2003-11-06 |
United States Patent
Application |
20030206822 |
Kind Code |
A1 |
Uchikoshi, Masahito ; et
al. |
November 6, 2003 |
High purity iron, method of manufacturing thereof, and high purity
iron targets
Abstract
High purity iron with a very few content of impurities such as
copper, a method of manufacturing thereof, and high purity iron
targets are provided. The iron containing impurities such as copper
is dissolved in a hydrochloric acid solution, and the concentration
of the hydrochloric acid of the aqueous solution of iron chloride
is adjusted to 0.1 kmol/m.sup.3 to 6 kmol/m.sup.3. Then, iron is
added in the aqueous solution of iron chloride, and an inert gas is
injected into the solution with agitating, in order to convert the
trivalent iron ions and divalent copper ions contained in the
aqueous solution of iron chloride respectively to divalent iron
ions and monovalent copper ions. Then, the aqueous solution of iron
chloride is fed into a column filled up with the anion exchange
resins. The divalent iron ions are not absorbed on the anion
exchange resins although the monovalent copper ions are absorbed on
the anion exchange resins. Therefore, copper can be separated from
the aqueous solution of iron chloride. And then, the aqueous
solution of iron chloride is evaporated to dryness, oxidized and
heated in a hydrogen atmosphere to generate iron.
Inventors: |
Uchikoshi, Masahito;
(Miyagi, JP) ; Yokoyama, Norio; (Miyagi, JP)
; Kekesi, Tamas; (Miyagi, JP) ; Isshiki,
Minoru; (Miyagi, JP) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL LLP
P.O. BOX 061080
WACKER DRIVE STATION, SEARS TOWER
CHICAGO
IL
60606-1080
US
|
Family ID: |
18782856 |
Appl. No.: |
10/446427 |
Filed: |
May 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10446427 |
May 28, 2003 |
|
|
|
09966425 |
Sep 28, 2001 |
|
|
|
Current U.S.
Class: |
420/8 ; 75/10.22;
75/739 |
Current CPC
Class: |
C22C 38/00 20130101;
Y02P 10/20 20151101; C22B 9/226 20130101; C22B 3/44 20130101; C23C
14/3414 20130101 |
Class at
Publication: |
420/8 ; 75/10.22;
75/739 |
International
Class: |
C21B 013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2000 |
JP |
P2000-301295 |
Claims
What is claimed is:
1. High purity iron with 99.99 mass % or more in purity wherein a
copper impurity content is 50 mass ppb or less.
2. High purity iron wherein a residual resistivity ratio thereof is
3000 or more, and a copper impurity content is 50 mass ppb or
less.
3. A method of manufacturing high purity iron comprising the steps
of; converting trivalent iron ions and impurity divalent copper
ions contained in an aqueous solution of iron chloride respectively
to divalent iron ions and monovalent copper ions; adjusting a
concentration of hydrochloric acid in a range of 0.1 kmol/m.sup.3
to 6 kmol/m.sup.3; and separating the monovalent copper ions from
the aqueous solution of iron chloride by using ion exchange
resins.
4. A method of manufacturing high purity iron according to claim 3,
comprising the steps of; converting trivalent iron ions and
impurity divalent copper ions contained in an aqueous solution of
iron chloride respectively to divalent iron ions and monovalent
copper ions; adjusting a concentration of hydrochloric acid in the
aqueous solution of iron chloride in a range of 0.1 kmol/m.sup.3 to
6 kmol/m.sup.3; and contacting the aqueous solution of iron
chloride with anion exchange resins to separate the monovalent
copper ions from the aqueous solution of iron chloride after the
steps of converting the trivalent iron ions and the divalent copper
ions respectively to the divalent iron ions and the monovalent
copper ions and adjusting the concentration of hydrochloric
acid.
5. A method of manufacturing high purity iron according to claim 3,
wherein the converting step comprises the steps of; injecting an
inert gas into the aqueous solution of iron chloride; and
converting trivalent iron ions and divalent copper ions contained
in an aqueous solution of iron chloride respectively to divalent
iron ions and monovalent copper ions by contacting the aqueous
solution of iron chloride with iron.
6. A method of manufacturing high purity iron according to claim 3,
wherein at least one of impurities selected from the group
consisting of zinc, gallium, niobium, technetium, ruthenium,
rhodium, palladium, silver, cadmium, indium, tin, antimony,
tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum,
gold, mercury, thallium, lead, and bismuth is separated from the
aqueous solution of iron chloride in the step of separating the
copper.
7. A method of manufacturing high purity iron according to claim 3,
further comprising the steps of; adjusting the concentration of
hydrochloric acid in the aqueous solution of iron chloride in a
range of 2 kmol/m.sup.3 to 11 kmol/m.sup.3; contacting the aqueous
solution of iron chloride with the anion exchange resins to absorb
the iron of trivalent ions thereon and separate at least one of
impurities selected from the group consisting of 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 contained in the aqueous solution of iron chloride, from
the aqueous solution of iron chloride; and eluting the iron from
the anion exchange resins with a hydrochloric acid solution.
8. A method of manufacturing high purity iron according to claim 7,
wherein a hydrochloric acid solution having a concentration of 0.1
kmol/m.sup.3 to 2 kmol/m.sup.3 is used for eluting the iron from
the anion exchange resins in order to separate the iron from at
least one of impurities selected from the group consisting of zinc,
gallium, niobium, molybdenum, technetium, ruthenium, rhodium,
palladium, silver, cadmium, indium, tin, antimony, tellurium,
tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,
mercury, thallium, lead, bismuth and polonium absorbed on the anion
exchange resins.
9. A method of manufacturing high purity iron according to claim 3,
further comprising the steps of; obtaining iron oxide from the
aqueous solution of iron chloride which the impurity copper are
separated therefrom; and heating the iron oxide in a hydrogen
atmosphere to obtain iron.
10. A method of manufacturing high purity iron according to claim
9, further comprising the step of melting the iron obtained in the
heating step with plasma arc using a plasma generation gas
containing active hydrogen in order to remove at least one of
impurities selected from the group consisting of oxygen, nitrogen,
carbon, sulfur, halogen, alkaline metals, and alkaline-earth
metals.
11. A method of manufacturing high purity iron comprising the steps
of; converting trivalent iron ions in an aqueous solution of iron
chloride to divalent iron ions; adjusting a concentration of
hydrochloric acid in a range of 0.1 kmol/m.sup.3 to 6 kmol/m.sup.3;
and separating at least one of impurities selected from the group
consisting of zinc, gallium, niobium, technetium, ruthenium,
rhodium, palladium, silver, cadmium, indium, tin, antimony,
tellurium, tantalum, tungsten, rhenium, osmium, iridium, platinum,
gold, mercury, thallium, lead, and bismuth from the aqueous
solution of iron chloride by using the anion exchange resins.
12. High purity iron targets with 99.99 mass % or more in purity
wherein a copper impurity content is 50 mass ppb or less.
13. High purity iron targets wherein a residual resistivity ratio
is 3000 or more, and a copper impurity content is 50 mass ppb or
less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to high purity iron in which
contents of impurities such as copper are reduced, a method of
manufacturing thereof, and high purity iron targets.
[0003] 2. Description of the Related Art
[0004] Semiconductor devices such as VLSI (very large scale
integrated circuit) and ULSI (ultra LSI) have a structure where
various thin metal films are deposited on, for example, a silicon
(Si) wafer. Although the idea of using iron (Fe) as a material of
magnetic random access memory (MRAM) has been considered in recent
years, the accompanying injurious impurities in the iron may result
in malfunction or deterioration of the semiconductor device, which
is undesirable. For example, copper (Cu) may cause a short circuit
because of high diffusion rate inside silicon, and radioactive
elements such as uranium (U) and thorium (Th) will cause incorrect
operations, and alkaline metals and alkaline-earth metals may cause
degradation of the device properties.
[0005] Furthermore, environmental semiconductor materials such as
iron silicide (FeSi.sub.2) have been proposed in order to build new
technologies dealing with future problems in environment and
depletion of resources. Iron suicide as an environmental
semiconductor material requires as few impurities as typical
compound semiconductors such as gallium arsenide (GaAs), cadmium
telluride (CdTe) and so on. The upper limit of impurity content in
iron silicide is less than in substances of semiconductor devices
of VLSI and ULSI. Small amounts of impurities form impurity level
that causes degradation of the semiconductor properties. Thus, iron
as a semiconductor material needs high purity.
[0006] While levels in purity of the crude iron traded globally and
presently are about 98% to 99.8%, such crude iron contains various
impurities, for example, transition metals such as nickel (Ni),
cobalt (Co), and chromium (Cr), gas elements such as oxygen (O),
nitrogen (N), and sulfur (S). Therefore, in order to use iron as
materials of semiconductor devices and environment semiconductors,
it is necessary to remove these impurities from the crude iron and
achieve higher purification. Moreover, iron appears favorable as
materials of devices such as magnetic recording mediums and
magnetic recording heads, as well as semiconductor devices, because
of bearing properties typical of ferromagnetic metals. A higher
purification of iron is indispensable to the use of iron as
materials of these devices.
[0007] Various methods of removing impurities from crude iron, for
example, wet processing such as solvent extraction, ion exchange,
and electrolytic refining for separation of metallic elements, and
dryness hydrogen gas (H.sub.2) processing for removal of gas
elements such as oxygen and nitrogen, and floating zone melting
refining method, have been studied.
SUMMARY OF THE INVENTION
[0008] However, there is a problem with the solvent extraction. It
is difficult to control extraction and reverse extraction and to
refine iron surely in industrial processes. And, although nearly
all of metal impurities can be separated by the ion exchange,
copper contents before and after refining by the ion exchange may
not change, that is, it is difficult to remove copper, which is a
problem with the ion exchange. In addition, there are problems with
the electrolytic refining that pH control of electrolytic solutions
is required, and it is difficult to remove nickel and copper. The
floating zone melting refining method is intended to further raise
the purity levels of metals purified to some extent, and in
practice, it is reported that the floating zone melting refining
method has large effects on purification (Yukio Ishikawa, Koji
Mimura, Minoru Isshiki, Bulletin of the Institute for Advanced
Materials Processing Tohoku University 51 (1995), pp.10-18).
However, it is difficult to apply the floating zone melting
refining method to large scale and the method may not always
produce high purity metals surely, that is, it is difficult to
produce a large amount of high purity iron at a low price with the
floating zone melting refining method. Therefore, a need exists for
methods of purifying iron easily, surely, and highly, and
particularly for the development of methods of removing copper.
[0009] The present invention has been achieved in view of the above
problems. It is an object of the invention to provide high purity
iron and high purity iron targets in which contents of impurities
such as copper are reduced.
[0010] It is another object of the invention to provide a method of
easily and surely manufacturing high purity iron.
[0011] The invention provides high purity iron with 99.99 mass % or
more in purity wherein a copper impurity content is 50 mass ppb or
less.
[0012] In another aspect, the invention provides high purity iron
wherein a residual resistivity ratio thereof is 3000 or more, and a
copper impurity content is 50 mass ppb or less.
[0013] A method of manufacturing high purity iron according to the
invention comprises the steps of; converting trivalent iron ions
and impurity divalent copper ions contained in an aqueous solution
of iron chloride respectively to divalent iron ions and monovalent
copper ions; adjusting a concentration of hydrochloric acid in a
range of 0.1 kmol/m.sup.3 to 6 kmol/m.sup.3; and separating the
monovalent copper ions from the aqueous solution of iron chloride
by using the ion exchange resins.
[0014] In another aspect, a method of manufacturing high purity
iron according to the invention comprises: converting trivalent
iron ions in an aqueous solution of iron chloride to divalent iron
ions; adjusting a concentration of hydrochloric acid in a range of
0.1 kmol/m.sup.3 to 6 kmol/m.sup.3; and separating impurities of at
least one selected from the group consisting of zinc, gallium,
niobium, technetium, ruthenium, rhodium, palladium, silver,
cadmium, indium, tin, antimony, tellurium, tantalum, tungsten,
rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead,
and bismuth from the aqueous solution of iron chloride by using the
anion exchange resins.
[0015] The invention provides high purity iron targets with 99.99
mass % or more in purity wherein a copper impurity content is 50
mass ppb or less.
[0016] In another aspect, the invention provides high purity iron
targets wherein a residual resistivity ratio is 3000 or more, and a
copper impurity content is 50 mass ppb or less.
[0017] In the high purity iron and the high purity iron targets
according to the invention, a concentration of copper is reduced to
50 mass ppb or less to achieve high purification.
[0018] The method of manufacturing the high purity iron according
to the invention includes the steps of converting trivalent iron
ions and divalent copper ions respectively to divalent iron ions
and monovalent copper ions, and adjusting a concentration of
hydrochloric acid. These steps allow monovalent copper ions to be
absorbed on the anion exchange resins, and divalent iron ions not
to be absorbed thereon. Thus the copper can be separated easily and
surely from the aqueous solution of iron chloride.
[0019] Another method of manufacturing high purity iron according
to the invention includes the steps of converting trivalent iron
ions in an aqueous solution of iron chloride to divalent iron ions
and adjusting a concentration of hydrochloric acid. These steps
allow at least one of impurities selected from the group consisting
of zinc, gallium, niobium, technetium, ruthenium, rhodium,
palladium, silver, cadmium, indium, tin, antimony, tellurium,
tantalum, tungsten, rhenium, osmium, iridium, platinum, gold,
mercury, thallium, lead, and bismuth to be absorbed on the anion
exchange resins, and divalent iron ions not to be absorbed thereon.
Thus the impurities can be separated easily and surely from the
aqueous solution of iron chloride.
[0020] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a flow chart illustrating a manufacturing process
of high purity iron and high purity iron targets according to one
embodiment of the invention.
[0022] FIG. 2 is a flow chart illustrating the manufacturing
process following FIG. 1.
[0023] FIG. 3 is a diagram explaining one step of the manufacturing
process shown in FIG. 1.
[0024] FIG. 4 is a diagram explaining another step of the
manufacturing processes shown in FIG. 1.
[0025] FIG. 5 is a graph illustrating changes of the concentrations
of metal ions in the effluent of the anion exchange resins.
[0026] FIG. 6 is another graph illustrating changes of the
concentrations of metal ions in the effluent of the anion exchange
resins.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] An embodiment of the present invention will be described in
detail below with reference to the accompanying drawings.
[0028] In accordance with one embodiment of the invention, high
purity iron and high purity iron targets have 99.99 mass % or more
in purity, preferably 99.999 mass % or more, or the residual
resistivity ratios thereof are 3000 or more and copper impurity
content thereof is 50 mass ppb or less.
[0029] The term "purity" (namely, chemical purity) used herein
means values obtained by one minus all concentrations of impurities
possible to be determined by using present analysis apparatus and
methods (Minoru Isshiki, Koji Mimura, Bulletin of the Japan
Institute of Metals, 31 (1992), 880-887). For example, the values
can be obtained by one minus the concentrations of impurities of 70
or more elements determined by Glow Discharge Mass Spectroscopy.
The concentrations of gas elements such as oxygen, nitrogen, and
hydrogen, if required, can be determined by appropriate methods
such as a non-dispersive infrared absorption method, a thermal
conductivity method, and a heat conduction measurement of such gas
elements separated with a column after being fused in an inert
gas.
[0030] And, residual resistivity ratios provide one index showing
purities of highly purified metals, and as shown in the formula I,
the residual resistivity ratio is the ratio of resistivity at 298 K
to resistivity at 4.2 K. The formula II shows a relationship
between resitivity and resistance (electric resistance). Therefore,
the formula I expressing the residual resistivity ratio can be
transformed into the formula III, and if volume changes by
temperature are negligible, the formula I can be approximated by
the ratio of the resistance at 298 K to the resistance at 4.2 K. It
should be noted that iron is a ferromagnetic metal and factors such
as geomagnetism, demagnetization conditions, and magnetic fields by
measurement currents can affect the resistance measurements. Thus,
it is necessary to apply vertical magnetic field that is preferably
about 60 kA/m in measuring the resistance in order to suppress
these influences (Seiichi Takagi, Materia Japan, 33 (1994),
6-10).
RRR=.rho..sub.298 K/.rho..sub.4.2K (I)
[0031] RRR; residual resistivity ratio
[0032] .rho..sub.298 K; resistivity at 298 K (.OMEGA.m)
[0033] .rho..sub.4.2K; resistivity at 4.2 K (.OMEGA.m)
.rho.=R.times.(S/L) (II)
[0034] .rho.; resistivity (.OMEGA.m)
[0035] R; resistance (.OMEGA.)
[0036] S; cross-section area perpendicular to the direction of
current (m.sup.2)
[0037] L; length (m) 1 RRR = R 298 K .times. S 298 K L 298 K R 4.2
K .times. S 4.2 K L 4.2 K R 298 K R 4.2 K ( III )
[0038] RRR; residual resistivity ratio
[0039] R.sub.298 K, S.sub.298 K, and L.sub.298 K; respectively,
resistance, cross-section area, length at 298 K
[0040] R.sub.4.2 K, S.sub.4.2 K, and L.sub.4.2 K; respectively
resistance, cross-section area, length at 4.2 K
[0041] The high purity iron and the high purity iron targets may be
used as materials of devices, for example, semiconductor devices,
magnetic recording mediums, magnetic recording heads, and devices
with environmental semiconductors. The term "environmental
semiconductor" used herein means a semiconductor substance that
exists abundantly on the earth and consists of an eco-friendly
material, for example, iron silicide (FeSi.sub.2) and calcium
silicide (Ca.sub.2Si) (See the website of Society of Kankyo
Semiconductors (http://kan.engjm.saitama-u.ac.jp/SKS-
/index2.html)).
[0042] Such high purity iron and such high purity iron targets can
be manufactured as follows.
[0043] FIGS. 1 and 2 show the manufacturing process of the high
purity iron according to the embodiment. First, the iron containing
impurities such as copper is dissolved in a hydrochloric acid
solution in order to prepare an aqueous solution of iron chloride
(FeCl.sub.2 or FeCl.sub.3) (Step S101). The concentration of the
hydrochloric acid is adjusted in a range of 0.1 kmol/m.sup.3 to 6
kmol/m.sup.3.
[0044] And, as shown in FIG. 3, the aqueous solution of iron
chloride M is poured into a container 12 with a metal 11 such as
iron. Then, the aqueous solution of iron chloride M is sufficiently
contacted with the metal 11 by agitating with a device such as a
stirrer 14, while injecting an inert gas 13 such as nitrogen gas
(N.sub.2) or argon gas (Ar) into the aqueous solution of iron
chloride M (Step S102). Thus, the copper contained in the aqueous
solution of iron chloride M will react with the metal 11, for
example, as shown in the following chemical formula 1, converting
the divalent copper ions to monovalent copper ions or metallic
copper. In addition, the iron contained in the aqueous solution of
iron chloride M will react with the metal 11, for example, as shown
in the following chemical formula 2, converting the trivalent iron
ions to divalent iron ions. It should be noted that the reaction of
the chemical formula 1 may not completely proceed to the right-hand
side and a small amount of the monovalent copper ions may remain in
the aqueous solution of iron chloride.
[CuCl.sub.2].sup.0+Fe(solid).fwdarw.[FeCl.sub.2].sup.0+Cu(solid)
(1)
2[FeCl.sub.6].sup.3-+Fe(solid).fwdarw.3[FeCl.sub.4].sup.2- (2)
[0045] Dissolved oxygen can prevent reactions such as the above
chemical formulas 1 and 2. Therefore, injecting the inert gas 13
into the aqueous solution of iron chloride M intends to remove
oxygen dissolved in the aqueous solution of iron chloride M, in
order to carry out the reactions. The inert gas 13 may be injected
with agitating the aqueous solution of iron chloride M containing
the metal 11, or before the metal 11 is added into the aqueous
solution of iron chloride M.
[0046] Preferably, the metal 11 has large surface area such as
powder, which can contact more effectively with the aqueous
solution of iron chloride M and react sufficiently with the copper
ions and iron ions. Substances other than iron can also be used for
the metal 11. It is preferred to use iron for the metal 11 in order
to avoid other impurities from contaminating the aqueous solution
of iron chloride M as much as possible.
[0047] The trivalent iron ions and divalent copper ions in the
aqueous solution of iron chloride M may be converted respectively
to the divalent iron ions and the monovalent copper ions by
contacting with the metal 11 after adjusting the concentration of
hydrochloric acid in the aqueous solution of iron chloride M as
described above, or before adjusting the concentration of
hydrochloric acid in the aqueous solution of iron chloride.
[0048] Then, as shown in FIG. 4, a column 22 is filled up with the
anion exchange resins 21, the aqueous solution of iron chloride M
is fed into the column 22 from a storage tank 23, and is contacted
with the anion exchange resins 21 sufficiently (Step S103). The
flow rate of the aqueous solution of iron chloride M is determined
effectively to contact the aqueous solution of iron chloride M with
the anion exchange resins 21 sufficiently, and is preferably 1 bed
volume(s)/hour. The divalent copper ions converted to the
monovalent copper ions will be absorbed on the anion exchange
resins 21, and the trivalent iron ions converted to divalent iron
ions will be eluted from the column 22 without being absorbed on
the anion exchange resins 21. FIG. 5 shows changes of the
concentrations of metal ions in the effluent (elution curve). In
FIG. 5, the abscissa represents the effluent volumes and the
ordinate represents the concentrations standardized by the maximum
concentrations of the metal ions. As shown in FIG. 5, there is no
range to which the peaks of the elution curves of the divalent iron
ions and the monovalent copper ions overlap, which shows that the
copper can be completely separated from the aqueous solution of
iron chloride. That is, the aqueous solution of iron chloride M
from which copper is separated is collected into a recovery tank
24.
[0049] In addition, when at least one of impurities selected from
the group consisting of zinc (Zn), gallium (Ga), niobium (Nb),
technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd),
silver (Ag), cadmium (Cd), indium (In), tin (Sn), antimony (Sb),
tellurium (Te), tantalum (Ta), tungsten (W), rhenium (Re), osmium
(Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg),
thallium (Ti), lead (Pb), and bismuth (Bi) is contained in the
aqueous solution of iron chloride M, as well as zinc and tin as
shown in FIG. 5, in the Step S103, these impurities can be absorbed
on the anion exchange resins 21 with monovalent copper ions and can
be also separated from the aqueous solution of iron chloride M.
[0050] When at least one of impurities selected from the group
consisting of lithium (Li), beryllium (Be), sodium (Na), magnesium
(Mg), aluminum (Al), silicon (Si), phosphorus (P), potassium (K),
calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium
(Cr), manganese (Mn), cobalt (Co), nickel (Ni), rubidium (Rb),
strontium (Sr), yttrium (Y), zirconium (Zr), cesium (Cs), barium
(Ba), lanthanoids, hafnium (Hf), francium (Fr), radium (Ra), and
actinoids, is contained in the aqueous solution of iron chloride M
after separating the copper, an oxidizing agent such as a hydrogen
peroxide solution as may be added to the aqueous solution of iron
chloride M to convert the divalent iron ions to trivalent iron ions
(Step S104). Or without such oxidation reaction the iron may be
oxidized if the aqueous solution of iron chloride M is allowed to
stand.
[0051] Then, the concentration of hydrochloric acid of aqueous
solution of iron chloride M is adjusted in a range of 2
kmol/m.sup.3 to 11 kmol/m.sup.3 and, as shown in FIG. 4, the
aqueous solution of iron chloride M is sufficiently contacted with
the anion exchange resins 21 (Step S105). Thus, the trivalent iron
ions will be absorbed on the anion exchange resins 21, and the
impurities such as 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 will not be absorbed on the anion exchange
resins 21 and be eluted.
[0052] FIG. 6 shows changes of the concentrations of metal ions in
the effluent (elution curve). The changes of the concentrations of
some typical impurities, that is, aluminum, silicon, phosphorus,
titanium, manganese, cobalt, and chromium, are shown in the FIG. 6
for comparison with the iron. In FIG. 6, the abscissa and the
ordinate represent respectively the equivalents in the FIG. 5. As
shown in FIG. 6, there is no range to which the peaks of the
elution curves of the trivalent iron ions and these impurities
overlap, which shows that these impurities can be completely
separated from the aqueous solution of iron chloride.
[0053] Moreover, when at least one of impurities selected from the
group consisting of zinc, gallium, niobium, molybdenum (Mo),
technetium, ruthenium, rhodium, palladium, silver, cadmium, indium,
tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium,
iridium, platinum, gold, mercury, thallium, lead, bismuth and
polonium (Po) is contained in the aqueous solution of iron chloride
M, these impurities can be absorbed on the anion exchange resins 21
as well as the iron in the Step S105.
[0054] In such a case, after absorbing the iron on the anion
exchange resins 21, 0.1 kmol/m.sup.3 to 2 kmol/m.sup.3 of
hydrochloric acid solution is passed through the column 22 to elute
the iron from the column filled up with the anion exchange resins
21 and separate the iron from the impurities absorbed on the anion
exchange resins 21 such as zinc, gallium, niobium, molybdenum,
technetium, ruthenium, rhodium, palladium, silver, cadmium, indium,
tin, antimony, tellurium, tantalum, tungsten, rhenium, osmium,
iridium, platinum, gold, mercury, thallium, lead, bismuth and
polonium (Step S106). Changes of the concentrations of metal ions
in the effluent in the Step S106 are also shown in the FIG. 6.
Especially, in the FIG. 6, the changes of the concentrations of
some typical impurities, that is, molybdenum and zinc are shown for
comparison with the iron. As shown in FIG. 6, there is no range to
which the peaks of the elution curves of the trivalent iron ions
and these impurities overlap, which shows that these impurities can
be completely separated from the iron.
[0055] It should be noted that molybdenum and polonium will be
mainly separated from the iron in the Step S106, because zinc,
gallium, niobium, technetium, ruthenium, rhodium, palladium,
silver, cadmium, indium, tin, antimony, tellurium, tantalum,
tungsten, rhenium, osmium, iridium, platinum, gold, mercury,
thallium, lead, and bismuth have already been separated from the
aqueous solution of iron chloride M with the copper in the Step
S103.
[0056] After eluting the iron, the obtained aqueous solution of
iron chloride M is evaporated to dryness and is oxidized in order
to obtain iron oxide (Step S107). Then, the obtained iron oxide is
heated from 500 K to less than 1800 K in a hydrogen atmosphere
(Step S108). It is preferred to heat to 1000 k or above for rapid
reduction. Thus, the iron oxide will react as shown in the
following chemical formula 3 to obtain iron.
3Fe.sub.2O.sub.3+H.sub.2=2Fe.sub.3O.sub.4+H.sub.2O
Fe.sub.3O.sub.4+H.sub.2=3FeO+H.sub.2O
Fe.sub.3O.sub.4+4H.sub.2=3Fe+4H.sub.2O
FeO+H.sub.2=F+H.sub.2O (3)
[0057] After reacting of the iron oxide, the obtained iron is
molten with plasma arc using a plasma generation gas containing
active hydrogen, in order to remove at least one of impurities
selected from the group consisting of oxygen, nitrogen, carbon (C),
sulfur, halogen, alkaline metals, and alkaline-earth metals (Step
S109). Thus, the steps described above can provide the high purity
iron and the high purity iron targets according to the
embodiment.
[0058] As described above, in the high purity iron and the high
purity iron targets according to the invention, the contents of
copper may be reduced to 50 mass ppb or less. Therefore, the high
purity iron or the iron targets according to the invention may not
be responsible for short circuit of devices such as semiconductor
devices and can be applied to the semiconductor devices for the
enhancement of properties. Moreover, the high purity iron and the
high purity iron targets can be used for devices such as magnetic
recording mediums and magnetic recording heads for the enhancement
of properties. In addition, the high purity iron and the high
purity iron targets used as materials of compound semiconductors
such as iron silicide may not cause unwanted impurity level formed
by small amounts of impurities responsible for property degradation
and will provide good semiconductor properties.
[0059] Moreover, according to the method of manufacturing the high
purity iron, the trivalent iron ions and the divalent copper ions
are converted respectively to the divalent iron ions and the
monovalent copper ions, the concentration of the hydrochloric acid
is adjusted from 0.1 kmol/m.sup.3 to 6 kmol/m.sup.3, and the
aqueous solution of iron chloride is contacted with the anion
exchange resins. Therefore, the copper may be separated from the
aqueous solution of iron chloride easily and the high purity iron
and the high purity iron targets with low concentrations of copper
can be obtained easily and surely.
[0060] Furthermore, converting the trivalent iron ions to the
divalent iron ions allows at least one of impurities selected from
the group consisting of zinc, gallium, niobium, technetium,
ruthenium, rhodium, palladium, silver, cadmium, indium, tin,
antimony, tellurium, tantalum, tungsten, rhenium, osmium, iridium,
platinum, gold, mercury, thallium, lead, and bismuth to be
separated easily from the aqueous solution of iron chloride M as
well as the copper. Thus, the high purity iron and the high purity
iron targets can be obtained easily and surely.
[0061] The invention will be further described in detail by
reference to FIGS. 1 to 6. In the following examples, the same
reference numbers and signs will be used for equivalents of the
substances in the above embodiments.
EXAMPLE
[0062] First, in order to prepare an aqueous solution of iron
chloride (FeCl.sub.3) M, scrap iron used as a material was
dissolved into 2 kmol/m.sup.3 of hydrochloric acid solution until
the concentration of the iron reached 0.179 kmol/m.sup.3 (10
g/dm.sup.3) (Step S101). Then, as shown in FIG. 3, powdered iron 11
was added to the aqueous solution of iron chloride M, and inert gas
was injected into the solution M with agitating to convert divalent
copper ions and trivalent iron ions respectively to monovalent
copper ions and divalent iron ions (Step S102). Then, as shown in
FIG. 4, the aqueous solution of iron chloride M was contacted with
the anion exchange resins 21 to absorb the monovalent copper ions
and separate the copper ions from the aqueous solution of iron
chloride M (Step S103).
[0063] After separating the copper, a hydrogen peroxide solution
was added to the aqueous solution of iron chloride M to convert the
divalent iron ions to trivalent iron ions (Step S104). Then, the
concentration of hydrochloric acid of the aqueous solution of iron
chloride M was adjusted to 5 kmol/m.sup.3, and the aqueous solution
of iron chloride M was contacted with the anion exchange resins 21
to absorb the trivalent iron ions and separate impurities such as
lithium (Step S105). Then, the iron was eluted from the column
filled up with the anion exchange resins 21 with 1 kmol/m.sup.3 of
hydrochloric acid solution to separate impurities such as
molybdenum (Step S106).
[0064] After eluting the iron from the column filled up with the
anion exchange resins 21, the obtained aqueous solution of iron
chloride M was evaporated to dryness and oxidized to obtain iron
oxide (Step S107). And, the obtained iron oxide was heated to 1073
K (800.degree. C.) in a hydrogen atmosphere to obtain iron (Step
S108). The iron obtained in the Step S108 was molten with plasma
arc containing active hydrogen to remove impurities such as oxygen
(Step S109) to obtain high purity iron.
[0065] Quantities of purities contained in the obtained high purity
iron were determined by Glow Discharge Mass Spectroscopy, and a
value of purity and residual resistivity ratio was calculated.
Table 1 shows the results. As shown in Table 1, the copper
concentration was as very low as 50 mass ppb or less, and the value
of purity was as very high as 99.9997%, and the residual
resistivity ratio was as very high as 5500.
1 TABLE 1 Concentration Concentration Concentration Element (mass
ppm) Element (mass ppm) Element (mass ppm) Concentration Al 0.380
Co 0.035 Rh <0.010 of impurities As <0.050 Ga 0.050 Ru
<0.010 B <0.010 Hf <0.010 Sb <0.020 Ba <0.010 In
<0.020 Si 0.060 Be <0.010 K 0.015 Sn 0.270 Bi 0.012 Li
<0.010 Th 0.001 Ca 0.110 Mg <0.010 Ti 0.150 Cd 0.120 Mn
<0.050 U 0.002 Cl <0.050 Mo <0.050 V 1.000 Cr <0.020 Na
<0.010 Zn 0.050 Cu <0.020 Ni <0.020 Zr 0.016 F <0.050 P
0.740 Pb 0.014 Purity 99.9997% Residual 5500 resistivity ratio
[0066] It is found that due to converting trivalent iron ions and
divalent copper ions respectively to divalent iron ions and
monovalent copper ions and adjusting the concentration of
hydrochloric acid from 0.1 kmol/m.sup.3 to 6 kmol/m.sup.3, copper
could be easily separated from the aqueous solution of iron
chloride, and the high purity iron having the concentration of
copper-reduced to 50 mass ppb or less could be obtained easily.
[0067] As described above, the invention is explained by the
embodiments and examples. These embodiments and examples are not
meant to limit the scope of the invention and variations within the
concepts of the invention are apparent. For example, as described
in the embodiments and examples, after converting the trivalent
iron ions and the divalent copper ions respectively to the divalent
iron ions and the monovalent copper ions, adjusting the
concentrations of hydrochloric acid and the aqueous solution of
iron chloride, and contacting the aqueous solution of iron chloride
with the anion exchange resins, the copper may be absorbed on the
anion exchange resins and be separated from the iron. After
adjusting the valencies of iron and copper and absorbing iron and
copper on the anion exchange resins, iron may be eluted with 0.1
kmol/m.sup.3 to 6 kmol/m.sup.3 of hydrochloric acid solution in
order to separate the copper from the aqueous solution of iron
chloride.
[0068] Moreover, impurities other than copper may be removed by the
methods as described in the above embodiments and examples, or by
other conventional methods. Furthermore, the copper may be
separated as well as the impurities such as zinc from the aqueous
solution of iron chloride after converting the trivalent iron ions
to divalent iron ions as described above, or may be separated by
other methods.
[0069] As described above, in the high purity iron and the high
purity iron targets according to the invention, the contents of
copper which causes influences such as a short circuit may be
reduced to 50 mass ppb or less. Therefore, the high purity iron or
the high purity iron targets according to the invention applied to
semiconductor devices may not be responsible for short circuit of
devices such as semiconductor devices and can provide the
enhancement of properties of the semiconductor devices. Moreover,
the high purity iron and the high purity iron targets can use for
devices such as magnetic recording mediums and magnetic recording
heads for the enhancement of properties. In addition, the high
purity iron and the high purity iron targets used as materials of
compound semiconductors such as iron silicide may not cause
unwanted impurity level formed by small amounts of impurities
responsible for property degradation and will provide good
semiconductor properties.
[0070] Moreover, according to the method of manufacturing the high
purity iron of the invention, the trivalent iron ions and the
divalent copper ions are converted respectively to the divalent
iron ions and the monovalent copper ions and the concentration of
the hydrochloric acid is adjusted from 0.1 kmol/m.sup.3 to 6
kmol/m.sup.3. Therefore, the copper may be absorbed on the anion
exchange resins and be separated from the aqueous solution of iron
chloride easily. In addition, the high purity iron and the high
purity iron targets with low concentration of copper can be
obtained easily and surely.
[0071] Furthermore, in another aspect, according to the method of
manufacturing the high purity iron of the invention, the trivalent
iron ions are converted to the divalent iron ions and the
concentration of the hydrochloric acid is adjusted from 0.1
kmol/m.sup.3 to 6 kmol/m.sup.3. Therefore, the impurities such as
zinc may be absorbed on the anion exchange resins and be separated
from the aqueous solution of iron chloride easily. In addition, the
high purity iron and the high purity iron targets can be obtained
easily and surely.
[0072] Obviously many modifications and variation of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *
References