rmw3 08 morita h
TRANSCRIPT
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Thermodynamics on SOG-Si
Refining Processes
Institute of Industrial Science,The University of Tokyo
Kazuki Morita
The 3rd Workshop on
Reactive Metal Processing
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Recent Research Fields
Physical Chemistry of High TemperatureProcessing (Steelmaking and Waste Management)
Microwave Processing for Recycling and WasteTreatment
Thermodynamics and Processing on Solar GradeSilicon (SOG-Si) Production
Materials Production and Recycling
Engineering Lab.(Formerly Ferrous Metallurgy Lab.)
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Contents
1. Introduction
2. Metallurgical refining for SOG-Si
- Thermodynamic properties of impurities in molten Si alloys -
- Optimized Process Combined with Leaching Treatment -
3. Solidification refining of Si with Si-Al metls
- Segregation ratios of impurities between solid Si and Si-Al melt -
4. Conclusions and Future Work
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Requirement for metallurgical refining process for SOG-Si
Depending on off-grade Si for semiconductor
Increase in solar cell production
90 91 92 93 94 95 96 97 98 99 1001011021031040
100
200300
400
500
600700
800
900
10001100
1200
Amountofproduction(MW)
YearFig. Amount of solar cell production by various processes.
Total
Poly Crystalline
Single Crystalline
AmorphousRibbon
00 01 02 03 04
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Possibility of Low Cost SOG-Si Production
Can we remove impurities from MG-silicon
by metallurgical refining processes ?
MG-Si SOG-Si
New Refining Process?
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Ti
Fe
P
Al
Fig. Solar-cell efficiency versus impurity concentration for
4-cm p-base devices.
Fe, Ti, Al, P, B
Impurtiry Content(ppma)
Fe 1300
Ti 220
Al 3300
P 30B 30
Table 1 Impurity
contents in MG-Si.
Impurities and solar cell efficiency
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-1600
-1200
-800
-400
0
0 500 1000 1500 2000 2500
4Cu+O2
=2Cu2O
2Fe+O2
=2FeO
2C+O2=2CO
C+O2=CO
2
3/2Fe+O2
=1/2Fe3
O4
2Mn+
O2=2MnO
Si+O2
=SiO2
4/3Ti+
O2=2/
3Ti2O3
4/3Al+
O2=2/
3Al2O3
2Mg+
O2=2Mg
O
2Ca+
O2=2
CaO
Temperature(K)
G ib
b s
e ne
rg y
o f
fo
rma t i
o n
fo r
o x i
d e s(k
J/ m
o l O
2)
-1600
-1200
-800
-400
0
0 500 1000 1500 2000 2500
4Cu+O2
=2Cu2O
2Fe+O2
=2FeO
2C+O2=2CO
C+O2=CO
2
3/2Fe+O2
=1/2Fe3
O4
2Mn+
O2=2MnO
Si+O2
=SiO2
4/3Ti+
O2=2/
3Ti2O3
4/3Al+
O2=2/
3Al2O3
2Mg+
O2=2Mg
O
2Ca+
O2=2
CaO
Temperature(K)
G ib
b s
e ne
rg y
o f
fo
rma t i
o n
fo r
o x i
d e s(k
J/ m
o l O
2)
Fe-FeO
Al-Al2O3
Mg-MgO
Ca-CaO
Si-SiO2
Fig. Ellingham diagram for some
representative elements.
Strong Affinity ofSilicon for Oxygen
=
Difficulty in
Oxidation Treatment
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Si Standard : solid Si standard : solid
GM solid
0 - 0- liquid
liquid solid
Component X Si
L
L T1
S+L
S+L S
Si Si
(a) Small segregation coefficient
Component XComponent X
Component X
T=T1
Si
GM
(b) Large segregation coefficient
T1
T=T1
Fig. Relationship between Gibbs free energy and phase diagram below
melting point of silicon.
P, B, C, etc.Most metallic
impurities
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10-6 10-5 10-4 10-3 10-2 10-1 10010-1110-1010-910-810-710-610-510
-410-310-210-1100101102103104
segregation coefficient
i
mpurityco
ntent(ppm
w) after first
solidification
after secondsolidification
Impurity content of MG-Si
Required impurity content for SOG-Si
Al
NiCr
Fe
V
Ti BP
Fig. Removal of impurity in silicon by solidification refining.
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Thermodynamic properties of
impurities in molten silicon alloys
PhosphorousEquilibrated in a controlled phosphorous partial pressure
Titanium and IronEquilibrated with lead
Aluminum, Calcium and MagnesiumEquilibrated with Oxides
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Thermodynamics of P in Molten Silicon
Gas Inlet Tube
Porous Alumina Block
Molten Si-P Alloy
Graphite or Alumina Crucible
Graphite Holder
Mullite Tube
Fig. Schematic Cross Section of Experimental Apparatus.
Ar+P4(P2+P)
To Ribbon Heater
Temperature Controller
Ar+P4
Thermocouple
SiliconePlug
Red Phosphorus Ribbon Heater
Ar
Red Phosphorus Temperature 398-461K
Argon Flow Rate 190cc/min
Fig. Schematic cross section of the phosphorus vapor generator.
To Ribbon Heater
Temperature Controller
Ar+P4
Thermocouple
SiliconePlug
Red Phosphorus Ribbon Heater
Ar
Red Phosphorus Temperature 398-461K
Argon Flow Rate 190cc/min
Fig. Schematic cross section of the phosphorus vapor generator.
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0.05 0.1
0.001
0.002
0[mass%P]
PP
1/2(atm1/2)
2
1750 1800 1850-80
-70
-60
-50
T(K)
Freeenergychange(kJ/mol)
1/2 P2(g)=P(mass%, in Si)G= -139,000+43.4T(J/mol)
Fig. Relationship between equilibrium
phosphorous partial pressure and
phosphorous concentration of silicon at
1823K.
Fig. Temperature dependence of
free energy change of phosphorous
dissolution into silicon.
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10-6 10-5 10-4 10-3 10-2 10-110-1610
-1510-1410-1310-1210-1110-1010
-910-810-710-610-510-4
[mass%P]
P
(atm)
P
P
P
P2P,
P
P2
1 2 3 4
0.01
0.02
0.03
0Time (ks)(V
/A)log([mass%P]0/[mass%P]t)(m
) Suzuki et al.estimated
Yuge et al.
1823K 1867K
Ikeda et al.
estimated
Fig. Relationship between equilibrium
partial pressure of P, P2 and phosphorouscontent of silicon at 1823K.
Fig. Relationship between time
for vacuum treatment and(V/A)
log([mass%P]0/[mass%P]t).
Hertz-Knudsen equation
iii
i
XpRT
M
dt
dy
=
0
2
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Fig. Schematic Cross Section of Experimental Apparatus.
Gas Inlet Tube
Porous AluminaBlock
Graphite Crucible
Graphite Holder
Mullite Tube
Graphite Lid
Molten Si-M
(M:Fe,Ti)
Molten Lead
Fig. Phase diagram of Si-Pb system.
Thermodynamics of Ti and Fe in Molten Silicon
Si Pb
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0 0.02 0.04 0.06-6
-5
-4-3
-2
-1
XFe in Si
lnXFeinPb-lnXFein
Si-14.1
XPbinS
i
-23.8
XSiinPb+4.91
lnXFe in Pb-lnXFe in Si-14.1XPb in Si-23.8XSi in Pb+4.91
=-3.56(0.40)+3.17(5.46)XFe in Si
Fe(l) in Si=2.8510-2
FeFe
in Si=3.17
0 0.025 0.05 0.075 0.1-9
-8
-7
-6
XTi in Si
lnXTiinPb-lnXTiinSi-13.2
XPbin
Si
-10
.8XSiinPb-1.7
4
lnXTi in Pb-lnXTi in Si-13.2XPb in Si
= -7.71+3.97X
Ti in Si
Ti(l) in Si=4.4810-4
TiTi
in Si=3.97
-10.8XSi in Pb-1.74
Fig. Relationsip betweenXTi in Si andlnXPb in Pb lnXPb in Si at 1723K.Fig. Relationsip betweenXFe in Si andlnXPb in Pb lnXPb in Si at 1723K.
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Ti and Fe are stable in molten silicon.
Removal of Ti and Fe by chemical
reaction (i.e. oxidation, chlorination) is
considered to be impossible.
Double solidification process is required.
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Fig. Schematic Cross Section of Experimental Apparatus.
Graphite
Holder
Al2O3-Al6Si2O13 Crucible
Molten Si-Al Alloy
SiO2 Crucible
Molten Si-Ca Alloy
Molten SiO2 satd.
CaO-SiO2 Slag
SiO2 Crucible
Molten Si-Mg Alloy
Molten MgSiO3, SiO2satd.MgO-SiO2-Al2O3 Slag
MgSiO3, SiO2pellet
Thermodynamics of Al, Ca and Mg in Molten Silicon
Al
Ca
Mg
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5.4 5.6 5.8
-1
-0.8
-0.6
-0.4
-0.2
0
-3.6
-3.4
-3.2
-3
-2.8
-2.6
104/T(K-1)
logAl(l),
logMg(l)
logCa(l)
Ca
Mg
Al
172317731823
T(K)
Fig. Temperature dependence of the activity coefficient of aluminum,
calcium, and magnesium in molten silicon relative to pure liquid.
51.411300ln
55.114300
ln
452.03610ln
Ca
Al
+=
+=
+=
T
T
T
Mg
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1 2 3 4 5 6
10
20
30
0
1000
2000
3000
0
P
Ca
Al
Fig. Relationship between vacuum time and impurity content of silicon at 1823K.
Time(ks)
massppmP
mass
ppmAl,massppmCa
0.739m2
40.3m2
mass of Si : 1000kg
surface area
P, Al, Ca and Mg can be
removed by vacuum melting.
Mg
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Vacuum melting by electron beam
Vacuum
Plasma melting with water vapor
Directional solidification
MG-Si
ArgonSOG-Si
Removal of P, (Al, Ca) Removal of B, C
Removal of Fe,Ti,Al
First step purification Second step purification
Directional solidification
Removal of Fe,Ti,Al
Lower cost refining process is desired to be developed
NEDO SOG-Si Manufacturing Process
(Operated in JFE Steel Co.)
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Is there any way to reduce the timesof solidification refining?
If the treatment of MG-Si can
remove 90% of Ti and Fe,
Possibility of Acid Leaching
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Si-Ca-Fe or Ti
dissolved at 1723K
Cooling to 1300K
(CaSi2 formation)
Acid leaching with
aqua regia
Chemical analysis
Acid Leaching Test with Ca Addition
Porous Alumina
Block
Graphite Crucible
Graphite HolderAr
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Removal Fraction of Fe
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Fig. Phase Diagram of the Si rich corner for theCa-Fe-Si System [calculated by Thermo-Calc]
Eutectic Point
XCa/XFe6.4
Secondary Phase
CaSi2 or FeSi2 ?
Consideration of Removal Behavior of
Fe with the Ca-Fe-Si Phase Diagram
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Fig.
(a) SEM micrograph of Si-Ca-Fe alloy.
(b) Microstructure of Si-Ca-Fe alloy.
(c) Concentration profile by EPMA line analysis.
Si-3.26%Ca-0.424%Fe, 4.4K/min
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Fig.
(a) SEM micrograph of Si-Ca-Fe alloy.
(b) Microstructure of Si-Ca-Fe alloy.
(c) Concentration profile by EPMA line analysis.
Si-2.41%Ca-0.685%Fe, 4.4K/min
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Vacuum melting by electron beam
Vacuum
Plasma melting with water vapor
Directional solidification
MG-Si
Argon
SOG-Si
Removal of P, (Al, Ca) Removal of B, C, (Al, Ca)
Removal of Fe,Ti,Al
First step purification Second step purification
Directional solidification
Removal of Fe,Ti,Al
NEDO SOG-Si Manufacturing Process
(Operated in JFE Steel Co.)
P : 30 < 0.1ppmw B : 5-10 0.1-0.3 ppmw
Acid leaching treatment with Ca addition
Removal of Fe and Ti
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Vacuum melting by electron beam
Vacuum
Plasma melting with water vapor
Directional solidification
MG-Si
Argon
SOG-Si
Removal of P, (Al, Ca) Removal of B, C, (Al, Ca)
Removal of Fe,Ti,Al
First step purification Second step purification
Directional solidification
Removal of Fe,Ti,Al
NEDO SOG-Si Manufacturing Process
(Operated in JFE Steel Co.)
P : 30 < 0.1ppmw B : 5-10 0.1-0.3 ppmw
Acid leaching treatment with Ca addition
Removal of Fe, Ti, P and B
Reduction of
processing time
Phase diagrams for the Si-Al system
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Solidification refining of Si with Si-Almelt at low temperature.
Low eutectictemperature
Fig. Phase diagram of Si-Al system.
Removal of impurities byuse of enhanced segregationat low temperature
Phase diagrams for the Si Al system
MG-Si
(98-99%)Pure Al
Segregation ratiomeltAlSiini
Sisolidini
iX
Xk
=
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Segregation ratios of impurities
between solid Si and Si-Al melt
Thermodynamics of impurity elements in solid Si
Evaluation of low temperature Si refining process
Segregation ratios of impurities between Si-Al melt and solid Si
Al, B, P
Fe,Ti, etc.
Experimentally determined
Theoretically determined
Determination for segregation ratios of P and B
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Fig. Diffusion coefficient of impurity elements in solid silicon.
Al, P, B Considerably smalldiffusion coefficient in solid Si
Solidification method to
attain the equilibrium
Diffusion coefficient of impurity elements in solid Si
Determination for segregation ratios of P and B
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1 2
Solid Si
Si-Al melt
Solid Si
T2
T1
Tm,A
C1sC1
l C2l C2
s A
Component B
Distance
a) b)
T
emp.
LS
L+S
Fig. Schematic diagrams of the temperature gradient zone melting.
(a) Portion of phase diagram. (b) Temperature gradient in system.(c) Physical system comprising (A+B)molten zone traveling through solid A.
c)
Temperature Gradient Zone Melting(TGZM) method
Precipitated Si
Determination for segregation ratios of P and B
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Temperature Gradient Zone Melting MethodAl and P contents in solid silicon -
EPMA analysisAr atmosphere 24-72h
Temperature Gradient 10-40K/cm
1
2
3
4
5 6 8
10
11
97
12
Fig. 1. Schematic diagram of an experimental apparatus: 1-SiC heating element; 2-thermocouple
connected to PID controller; 3-gas outlet tube; 4-stainless steel holder; 5-single crystalline silicon; 6-aluminum foil; 7-mullite tube; 8-thermocouple for measuring temperature of molten zone; 9-porous
alumina boat 10-gas inlet tube; 11-alumina plate; 12-Sponge titanium
Distribution of P (and Al) between
solid Si and Si-Al-P alloy
- Red phosphorus stuck Al foil
Distribution of B (and Al) between
solid Si and Si-Al-B alloy
- Prepared Al-B foil
Experimental method
Determination for segregation ratios of P and B
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Fig. Photo of a TGZM specimen after
the experiment.
10mm
B A
Fig. Intensity profiles of Ka radiation of aluminum and
phosphorus of the sample (accelerating voltage of 15kV,sample current of 200nA, sampling step of 10m).
100 200 300 400 500 600
100
200
300
400
0
Distance (m)
IntensitiesofK
radiationof
alu
minumandphosphorus
PAl
(a) Single crystalline Si (d) Single crystalline Si(c) Si-Al zone
(b) Migrated region
Segregation ratio
Sample after TGZM experiment
Segregation ratios of P and B
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Segregation ratios of P and B
1200 1400 16000.01
0.05
0.1
0.5
1
5
Temperature (K)
Se
gregationratio
P
B
Segregation ratios are smaller at low temperature.
Low temperature refining is effective.
Segregation ratio between
solid Si and Si-Al melt
Segregation coefficient
between solid/liquid Si.
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s
i
s
i
l
i
l
i aRTGaRTG lnln00+=+
0
0
lnlnlns
i
l
i
fus
i
l
i
s
i
iRT
G
X
Xk
+
==
Equality in chemical potential of impurity between solid Si
and Si-Al melt
1)
2)
Activity coefficients in solid Si and Si-Al melt
Based on the reported thermodynamic data
Derivation of segregation ratio of impurity
elements between solid Si and Si-Al melt
Segregation ratios between solid Si and Si-Al melt
< S ti ffi i t b t lid/li id Si
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< Segregation coefficients between solid/liquid SiSegregation ratio between Si-Al me lt
and solid SiElement
1073K 1273K 1473K
Segregation coefficient
between solid/liquid Si at
m.p. of Si(6-3)
Fe 1.710 -11 5.910 -9 3.010 -7 6.410 -6
Ti 3.810 -9 1.610 -7 9.610 -7 2.010 -6
Cr 4.910 -10 2.510 -8 2.510 -7 1.110 -5
Mn 3.410 -10 4.510 -8 9.910 -7 1.310 -5
Ni 1.310 -9 1.610 -7 4.510 -6 1.310 -4
Cu 9.210 -8 4.410 -6 2.510 -5 4.010 -4
Zn 2.210 -9 1.210 -7 2.110 -6 1.010 -5
Ag 1.910 -8 1.710 -6 6.610 -6 5.010 -5
Au 1.510 -11 6.110 -9 3.610 -7 2.510 -5
Ga 2.110 -4 8.910 -4 2.410 -3 8.010 -3
In 1.110 -5 4.910 -5 1.510 -4 4.010 -4
Sb 3.410 -3 3.710 -3 8.210 -3 2.310 -2
Pb 9.710 -5 2.910 -4 1.010 -3 2.010 -3
Bi 1.310 -6 2.110 -5 1.710 -4 7.010 -4
P 4.010 -2 8.510 -2 1.610 -1 3.510 -1
B 7.610 -2 2.210 -1 4.910 -1 8.010 -1
Al 1.410 -4 4.910 -4 1.210 -3 2.810 -3
Impurity contents of Si after low temperature
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10-6
10-5
10-4
10-3
10-210
-1
100
101
102
103
Contents of MG-Si Allowable contents for SOG-SContents after solidification refining with Si-Al meltContents after ordinary solidification refining
Impurityco
ntent(ppmw
)
Fe Ti P B
Impurity contents of Si after low temperature
solidification refining with Si-Al melt at 1273K and
ordinary Si solidification refining of MG-Si.
Contents after purification; Ci =ki Ciini Initial content
(MG-Si)at 1273K
Si
Viewing the development of the solidification
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refining of Si with Si-Al melt at low temperature
Fig. Phase diagram of Si-Al system.
Si bathAl bath
Si-Al melt
Poly or Single Crystalline ?
Discussion of the Si solidification method
from Si-Al melt
Refining test
Discussion for separating of solid Si from Si-Al
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melt by flotation
Holding Si-55.3at%Al alloy (liquidus temp. 1273K) at 1173K for 12h
Si saturated, solid fraction = 0.168
Needle like Si grains
Preparation Melting in the
induction furnace and rapid cooling
(solid Si < 2.33g/cm3, Al-25.8%Si 2.45g/cm3)
Separation of solidified Si from Si-Al
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p
melt using electromagnetic force Induction furnace1
3
7
12
11
54 6
8
109
2
Si-55.3at%Al alloy (liquidus,1273K) was melted and held at
1323K in the induction furnace
Measuring the surfacetemp. of the melt by
the infrared pyrometer
Cooling and Solidifying the
sample by lowering from the
position of induction coil
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Solidified Si-Al alloy using
induction furnace
Agglomeration of solidified Si by electromagnetic stirring
Bottom
1cm
Agglomeration mechanism of Si under
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Si-Al melt Solidified Si
Inductioncoil
J
B
J
BInduced flow
F
Difference in inducedswirl current to the
perpendicular direction
Solidification of Si at lower
position
Downward bulk flowAgglomeration of Si grainsto the bottom of the sample
gg
the fixed alternative magnetic field
Solidification refining test
Experimental method Synthesized MG-Si was alloyed to Si-
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Fig. Schematic cross section ofexperimental apparatus.
Alumina block
Gas inlet tube
Induction coil
Graphite crucible
Quartz tube
Prism
Molten alloy
Melting and holding at 1323K
or 1223K
Cooling and solidifying the sampleby lowering from the coil
Measuring the surface temp.
by infrared pyrometer
p
Crashing the Si agglomerated part
(> 840m), then acid cleaningSample No. Fe Ti Al B P
PrSi-1 4500 691 1280 56 36
PrSi-2 2160 248 1560 36 19
Synthesized MG-Si was alloyed to Si-
55.3at%Al(liquidus, 1273K) or Si-64.6
at%Al(liquidus, 1173K) with pure Al
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Sample No Source Fe Ti B P Al
SR-1 PrSi-1 13 (99.7%) 5.2 (99.2%) 0.81 (98.6%) 0.93 (97.4%) 599 (53.1%)
SR-2 PrSi-1 13 (99.7%) 2.7 (99.6%) 0.88 (98.4%) 1.2 (96.7%) 534 (58.1%)
SR-3 PrSi-2 20 (99.1%) 2.8 (98.9%) 0.71 (98.1%) 0.72 (96.3%) 575 (63.1%)
SR-4 PrSi-2 27 (98.8%) 4.5 (98.2%) 1.90 (94.8%) 1.0 (95.1%) 602 (61.3%)
SR-5 PrSi-1 47 (99.0%) 7.7 (98.9%) 0.98 (98.3%) 0.42 (98.8%) 538 (57.8%)
SR-6 PrSi-1 36 (99.2%) 5.6 (99.2%) 0.99 (98.2%) 0.66 (98.2%) 453 (64.5%)
Fe, TiWell reduced but not as well as predicted valuesB, P Effectively removed
Impurity contents of refined Si in the test run (ppmw)
High ability for purification was confirmed.
Proposal of refining process for SOG-Si
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Vacuum melting by electron beam
Reduction of SiO2 in arc furnace
Removal of P, (Al, Ca)
Removal of Fe,Ti,Al
Directional solidification
Alloying of silicon with Al
SOG-Si
Solidification refining with Si-Al melts
Pre-refined Si (5N except Al)
Proposal of refining process for SOG Si
Acid cleaning
C l i d F t W k
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Conclusions and Future Work
The optimum metallurgical refining
process for SOG-Si was thermodynamicallyassessed.
Possibility of solidification refining of Si
with Si-Al melt was clarified. Solidification
and separation of Si from the melt is the
major problem to solve for the practical
process.
A k l d t
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Acknowledgments
Present data are based on two Doctoral
Dissertations by Takahiro Miki (1999),now a research associate of Tohoku
University, and Takeshi Yoshikawa(2005), now an assistant professor of
Osaka University.
Periodical Journal Publication List 1
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Metallurgical Refining
T.Miki, K.Morita and N.Sano :Metallurgical and Materials Transactions B, 27B(1996),937-942, Thermodynamics of Phosphorus in Molten SiliconT.Miki, K.Morita and N.Sano :Metallurgical and Materials Transactions B, 28B(1997),861-867, Thermodynamic Properties of Titanium and Iron in Molten SiliconT.Miki, K.Morita and N.Sano :Metallurgical and Materials Transactions B, 28B(1997),861-867, Thermodynamic Properties of Titanium and Iron in Molten SiliconT.Miki, K.Morita and M.Yamawaki :Journal of the Mass Spectrometry Society ofJapan47(1999), 72-75, Measurements of Thermodynamic Properties of Iron in MoltenSilicon by Knudsen Effusion MethodT.Miki, K.Morita and N.Sano :Materials Transactions, JIM, 40 (1999), 1108-1116,Thermodynamic Properties of Si-Al, -Ca, -Mg Binary and Si-Ca-Al, -Ti, -Fe TernaryAlloys 66(2002), 459-465, K.Morita and T.Miki :Intermetallics, 11(2003), 1111-1117, Thermodynamics on Solar-Grade-Silicon RefiningG.Inoue, T.Yoshikawa and K.Morita :High Temperature Materials and Processes,22(2003), 221-226, Effect of Calcium on Thermodynamic Properties of Boron in MoltenSiliconT.Shinpo, T.Yoshikawa and K.Morita :Metallurgical and Materials Transactions B,35B(2004), 277-284, Thermodynamic Study of the Effect of Calcium on Removal ofPhosphorus from Silicon by Acid Leaching Treatment
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Solidification Refining
T.Yoshikawa and K.Morita :J.Electrochem. Soc., 150(2003), G465-G468, SolidSolubilities and Thermodynamic Properties of Aluminum in Solid Silicon
T.Yoshikawa and K.Morita :Science and Technology of Advanced Materials, 4(2003), 531-537, Removal of Phosphorus by the Solidification Refining with SiAl Melts
T.Yoshikawa and K.Morita :Journal of Physics and Chemistry of Solids, 66(2005), 261-265,Thermodynamics of Solid Silicon Equilibrated with Si-Al-Cu Liquid AlloysT.Yoshikawa and K.Morita :Materials Transaction, 46(2005), 1335-1340,Thermodynamic Property of B in Molten Si and Phase Relations for the Si-Al-B SystemT.Yoshikawa and K.Morita :ISIJ International, 45(2005), 967-971, Refining of Si by theSolidification of Si-Al Melt with Electromagnetic ForceT.Yoshikawa and K.Morita :Metallurgical and Materirals Transactions B, 36B(2005), 731-736, Removal of B from Si by the Solidification Refining with SiAl MeltsT.Yoshikawa, K.Arimura and K.Morita :Metallurgical and Materirals Transactions B,36B(2005), 837-842, B Removal by Ti Addition in the Solidification Refining of Si with SiAl MeltsT.Yoshikawa and K.Morita :Journal of Alloys and Compounds, 420(2006), 136-144Activity Measurements of Al and Cu in Si-Al-Cu Melt at 1273 and 1373 K by theEquilibration with Molten Pb