1. High Purity Rare Earth Metals Preparation
2011
Materials Preparation Center A US Department of Energy Specialized Research Center
High Purity Rare Earth Metals Preparation
Trevor M. Riedemann
Manager, MPC Rare Earth Materials Section
122 Metals Development Building
Ames Laboratory
Ames, IA
Phone:
Fax:

2. Acknowledgements
The Materials Preparation Center (MPC) is a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences & Engineering specialized research center located at the Ames Laboratory. MPC operations are primarily funded by the Materials Discovery, Design, & Synthesis team's Synthesis & Processing Science core research activity.
Thomas A. Lograsso
Division Director
Division of Materials Science & Engineering
124 Metals Development Building
Ames, IA
Phone:
Fax:
Lawrence L. Jones
Director, MPC
121 Metals Development Building
Ames Laboratory
Ames, IA
Phone:
Fax:

3. Acknowledgements
The Rare Earths, F.H Spedding & A.H. Daane, eds. (1961) John Wiley & Sons. Chapter 6 – Preparation of the Rare Earth Fluorides, O.N. Carlson & F.A. Schmidt Chapter 8 – Metallothermic Preparation of Rare Earth Metals, A.H. Daane Beaudry, B.J. & P.E. Palmer, (1974) “The use of inert atmospheres in the preparation and handling of high purity rare earth metals” Haschke, J.M, and H.A. Eich, eds. Proceedings of the 11th Rare Earth Research Conference (CONF , Part 2, NTIS, Springfield, Virginia 22151) pp Handbook on the Physics and Chemistry of Rare Earths, Vol 1 – Metals, (1978) K.A.Gschneidner, Jr. & L.R. Eyring, eds. Chapter 2 – Preparation and Basic Properties of the Rare Earth metals, B.J. Beaudry & K.A. Gschneidner A Lanthanide Lanthology, Part I & II, B.T. Kilbourn (1993) Molycorp. Inc.

4. The Rare Earths - A very Brief History
1794 J. Gadolin first reports their existence 1804 M.H. Klaproth isolated ceria 1827 Preparation of first REM (Ce) … 1931 Preparation of “reasonably pure” metal by electrolysis 1937 Pure enough to determine crystal structures 1947 Separation adjacent RE by ion exchange. 1950’s Spedding and Daane – developed “Ames Process”
1787 – 1987 Two Hundred Years of Rare Earths
Rare Earth Information Center IS-RIC 10
Institute for Physical Research and Technology
Iowa State University
K.A. Gschneidner Jr & J. Capellen, ed.

5. The Rare Earths - Etymology
Z Symbol Name Etymology 21 Sc Scandium Latin Scandia (Scandinavia)
Y Yttrium Ytterby, Sweden, where the first ore was discovered.
57 La Lanthanum Greek "lanthanein", meaning to be hidden.
58 Ce Cerium For the dwarf planet Ceres Pr Praseodymium Greek "prasios” leek-green, &"didymos", meaning twin Nd Neodymium Greek "neos” new, and "didymos", meaning twin.
61 Pm Promethium Titan Prometheus, who brought fire to mortals. 62 Sm Samarium Vasili Samarsky-Bykhovets, who discovered samarskite.
63 Eu Europium For the continent of Europe Gd Gadolinium Johan Gadolin (1760–1852), to honor his study of REE Tb Terbium Ytterby, Sweden.
66 Dy Dysprosium Greek "dysprositos", meaning hard to get Ho Holmium Stockholm (in Latin, "Holmia”)
68 Er Erbium Ytterby, Sweden.
69 Tm Thulium For the mythological northern land of Thule.
70 Yb Ytterbium Ytterby, Sweden.
71 Lu Lutetium Lutetia, the city which later became Paris.
1787 – 1987 Two Hundred Years of Rare Earths
Rare Earth Information Center IS-RIC 10
Institute for Physical Research and Technology
Iowa State University
K.A. Gschneidner Jr & J. Capellen, ed.

6. The Rare Earths - Abundance
US Geological Survey Fact Sheet
Rare Earth Elements – Critical Resources for High Technology
Gordon B. Haxel, James B. Hedrick, and Greta J. Orris

7. High Purity Oxide Prices
La2O3
CeO2
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
Tb4O7
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
III / IV
Dy output and consumption are approximately an order of magnitude lower than Nd.
In 2000, Dy was in great demand, as its use in NdFeB alloys increased
significantly and some hoarding and speculating took place in the second
half of that year. Demand grew faster than actual output, reaching a virtual
balance in 2000 but diverged again in Dy prices went through the
roof in 2000 only to come crushing down in the second half of 2001, as
shown in Figure 2. At the end of 2003, the supply/demand spread started
to close again, which was reflected in prices rising sharply in the third
quarter of 2003 and continuing strong. As indicated in Figure 5, with the
limited availability of Dy, it does not take much of an increase in demand
to trigger an imbalance, particularly since Dy is used in magnetic alloys
and electronic ceramic chips, both of which are growing strongly again.
We expect the Dy tightness to continue.
(d) Terbium
Tb has a similar functionality as Dy in magnetic alloys and certain
producers favour Tb over Dy. Still, not a lot of Tb is used in magnetic
alloys and for good reasons. Two things should be apparent when one
examines Figure 6. First, the availability of Tb is about two orders of
magnitude lower than Nd and, second, Tb consumption has traditionally
been in much closer balance with output than most rare earths.
UPDATE ON THE GLOBAL RARE EARTH INDUSTRY:
Prospect for Magnetic Rare Earth Materials 2004 China Magnet Symposium
Global Markets and Business Opportunities
May 17-21, 2004, Xi’an, China
Constantine E. Karayannopoulos

8. High Purity Oxide Prices
La2O3
CeO2
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
Tb4O7
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
III / IV
/2010
La 99% US$/kg
Ce 99% US$/kg
Pr 99% US$/kg
Nd 99% US$/kg
Eu 99% US$/kg
Tb 99% US$/kg
Dy 99% US$/kg
Dy output and consumption are approximately an order of magnitude lower than Nd.
In 2000, Dy was in great demand, as its use in NdFeB alloys increased
significantly and some hoarding and speculating took place in the second
half of that year. Demand grew faster than actual output, reaching a virtual
balance in 2000 but diverged again in Dy prices went through the
roof in 2000 only to come crushing down in the second half of 2001, as
shown in Figure 2. At the end of 2003, the supply/demand spread started
to close again, which was reflected in prices rising sharply in the third
quarter of 2003 and continuing strong. As indicated in Figure 5, with the
limited availability of Dy, it does not take much of an increase in demand
to trigger an imbalance, particularly since Dy is used in magnetic alloys
and electronic ceramic chips, both of which are growing strongly again.
We expect the Dy tightness to continue.
(d) Terbium
Tb has a similar functionality as Dy in magnetic alloys and certain
producers favour Tb over Dy. Still, not a lot of Tb is used in magnetic
alloys and for good reasons. Two things should be apparent when one
examines Figure 6. First, the availability of Tb is about two orders of
magnitude lower than Nd and, second, Tb consumption has traditionally
been in much closer balance with output than most rare earths.
Source: Metal Pages

9. The Rare Earths - Physical Properties

10. The Rare Earths - Ames Process
High purity oxides from Ion-Exchange
(2) Preparation of anhydrous RE-fluorides
(3) Metallothermic reduction by Ca metal
(4) Metallothermic reduction by La metal
R2O3 + 6HF  2RF3 + 3H2O
3Ca + 2RF3  2R + 3CaF2
R2O3 + 2La  La2O3 + 2R

11. ? Ames Process = High purity Impurity Sources:
Oxygen: Incomplete oxide conversion
Calcium reductant
Atmosphere (handling and processing)
N, C, & H: Adsorbed on oxide/fluoride
Tantalum Crucible
Atmosphere
Ca & F: Reductant and incomplete reduction (10% excess Ca is used in Rx)
Insufficient vacuum casting
Fe, Co, Ni & Cu: Tantalum Crucible
Impurities in oxide & HF
Contamination of oxide during handling
Cross Contamination
in Processing Line
Foundry vs Chip Fab

12. How Pure? Ames Commercial 99.996 99.99 99.99 99.96 99.9 99.2
N/T

13. Anlaysis of three commercial Tb samples and MPC Tb (ppm at).
Source A Source D MPC
Impurity Ingot Distilled Distilled Distilled H
C n.a. n.a. n.a N O Fe La Ta
Total mag. RE
at% pure <97.5 <95.6 <94.2 <99.81
Semiquantitative MS for 25 elements (H,N and O by vacuum fusion)
High purity Rare Earth Metals – Do We Need Them?
Proc. of the first Symposium Rare Metals Forum, Extra-High Purification
Technology and New Functional Materials Creation of Rare Earth Metals,
Society of Non-Traditional Technology, Tokyo, Japan (1989) pp 13-29
K.A. Gschneidner, Jr.

14. Why do we need High Purity Metals?
Impurities affect the basic properties of pure metals (and alloys)
Lattice parameters
Crystal structure
Melting point
Hardness
Strength
Resistivity
Susceptibility
Grain growth
Magnetic domain wall motion
Stoichiometry of alloy is shifted
Second phase can form and change the properties.
Crystal Growth
Oxygen as impurity in crystal growth of intermetallics, D. Souptel, W. Lo¨ ser, W. Gruner, G. Behr, Journal of Crystal Growth 307 (2007) 410–420
Impurities may mask the
INTRINSIC behavior of the
pure metal or alloy material

15. Why do we need High Purity Metals?
V. K. Pecharsky and K. A. Gschneidner, Jr.
Giant Magnetocaloric Effect in Gd5Si2Ge2
Physical Review Letters 78 (1997) No. 23
T. Zhang , et. Al (Sichuan University)
The structure and magnetocaloric effect of rapidly quenched Gd5Si2Ge2 alloy with low-purity gadolinium
Materials Letters 61 (2007) 440–443
K. A. Gschneidner, Jr., et al.
Method of Making Active Magentic Refrigerant, Colossal Magnetostriction and Giant Magentoresistive Materials Based on Gd-Si-Ge Alloys
US Patent: 6,589,366 B1 (2003)
-ΔSm (J/kg K)
Impurities are suppressing a structural transition from orthorhombic to monoclinic
Gd5Si2Ge2 alloy was prepared by arc-melt method in an argon atmosphere with low-purity commercial Gd (99 wt.%), high-purity Si and Ge (purities both better than wt.%). The typical impurities of the commercial grade Gd are (wt.%):O: 1500 ppm,C: 200 ppm, Fe: 300 ppm, Ca: 300 ppm, Mg: 300 ppm, Si: 100 ppm, Al: 100 ppm.
Gd5Si2Ge2: 0 – 5 T
Temperature (K)

16. Why do we need High Purity Metals?
Y. Matsumoto, et al.
Quantum Criticality Without Tuning in the Mixed Valence
Compound  -YbAlB4.
Science, 2011; 331 (6015)
S. Nakatsuji, et al.
Superconductivity and quantum criticality in the heavy-fermion
system –YbAlB4
Nature Physics 4, (2008)
Robin T. Macaluso, et. al
Crystal Structure and Physical Properties of Polymorphs of LnAlB4
(Ln = Yb, Lu)
Chem. Mater., 2007, 19 (8), pp 1918–1922
An exotic new superconductor based on the element
ytterbium displays unusual properties that could change
how scientists understand and create materials for
superconductors and electronics. Beta-YbAlB4, can
reach a quantum critical, without being subject to
massive changes in pressure, magnetic fields,
or chemical impurities.

17. High Purity Oxides Inputs: Oxides GARBAGE IN = GARBAGE OUT Y2O3 La2O3
CeO2
Pr6O11
Nd2O3
Sm2O3
Eu2O3
Gd2O3
Tb4O7
Dy2O3
Ho2O3
Er2O3
Tm2O3
Yb2O3
Lu2O3
III / IV
GARBAGE IN = GARBAGE OUT
Praseodymium Oxide
Pr6O11
99.999% pure
<10 ppm REM

18. Inputs: Calcium Reductant
Triple Distilled commercial Ca has ~2000 – 5000 ppm oxygen

19. Distilled under He pp to remove oxygen
6 Days
900 g/run
Ce 1900g Ca
Lu g Ca
Oxygen content is lowered <10 ppm
Glove box protected
Ca readily picks up O from H2O
>1000 ppm from air in 5 minutes
The effect of handing the Ca in air results in a 30-fold increase in O content in Cerium metal (BJB)

20. X X X X X X Inputs: Tantalum 10” x 14” x 0.030” = $1081.00 Alumina
Magnesia
Quartz
Zirconia
Graphite
Iron X X X X X

21. Inputs: Tantalum Element R05200 R05400 C 0.010 0.010 O 0.015 0.03
ASTM B708 – 05 R05200, unalloyed tantalum, electron-beam furnace or vacuum-arc melt, or both
ASTM B708 – 05 R05400, unalloyed tantalum, powder-metallurgy consolidation
Element R R05400 C O N H Fe Mo Nb Ni Si Ti W
Cleanest Ta: Pickled
Annealed
2000ºC degassed

22. Nasty Stuff Inputs: Hydrofluoric Acid (HF)
Purity range from 99% to 99.99%
Parameter Level †
HF wt%
H2SO wt ppm
SO wt ppm
H2O wt ppm
As wt ppm
Hydrofluosilicic mol %*
†Honeywell Specifications
*Handbook of Compressed Gasses, 4th ed. (1999) H2SiF6
IDLH = 30 ppm, (Immediately Dangerous to Life and heath, for comparison Cyanide Gas has an IDLH of 50 ppm)
LC50 = 1,276 ppm (Lethal Concentration 50, half of exposed group dies, tests conducted on rats, dogs, and monkeys)
OSHA
Permissible Exposure Limit (PEL) = 3 ppm 8 hours
Short Term Exposure Limit (STEL) = 6 ppm 15 min.
Deaths have been reported from as little as 2.5% body surface area (BSA) burns from concentrated acid.
The palm of your hand is approximately 1% BSA.
Nasty Stuff
Not a lot of impurities to worry about…but…..

23. 1 2 3 4 The Rare Earths - Physical Properties
Vapor Pressure at Melting Point
Tm mm Hg
Ce 3.6(10)-12 mm Hg

24. Ames Process – Flow Diagram1 4 2 3

25. Ames Process – Flow Diagram
Sm, Eu, Tm and Yb
Low Boiling Points
Reduction by Lanthanum from Oxide
Easily purified by Sublimation
Sm, Eu, Tm and Yb can be melted in Ta crucibles without Ta contamination
Tm is very difficult to arc melt due to ~74mm vapor pressure at its melting point

26. Ames Process – Procedure
Sm, Eu, Tm and Yb
Dry Oxide Removes H2O and CO2
Machine lanthanum chips
Mix oxide and La chips (in dry box)
Pack in crucible (in dry box)
Load into induction furnace
Heat under vacuum.
Hold for 8 hours
Perform a low temp sublimation.
Strip Ta from sublimate mass
Europium is extruded.

27. Ames Process

28. Sublimed Ytterbium Metal

29. Ames Process – Flow Diagram
La, Ce, Nd and Pr
Low Melting but high Boiling Points
Volatile impurities (Ca & F) can be quantitatively removed by vacuum casting without loss of metal
Ta solubility at M.P. is low therefore Ta dissolved during vacuum casting can be removed by precipitation.

30. Ames Process – Procedure
La, Ce, Nd and Pr
Dry Oxide
LT/HT Fluorination of oxide
Heat mixture of Ca & REF3
Cool, remove slag
Total of three reductions in same crucible
Vacuum cast at high temperature
Cool to just above melting point.
Hold to precipitate tantalum
Decant or “pour” RE into thin wall crucible
Machine off crucible
Arc cast into ingots

31. Ames Process: Low Temp Fluorination

32. Ames Process
Reduction Step

33. Ames Process
Post Reduction

34. Ames Process
Pour/Decant Step

36. Ames Process – Flow Diagram
Sc, Dy, Ho and Er
High Melting and low to intermediate Boiling Points.
To remove F impurity thru vacuum casting, must loose up to 30% of metal
Easily purified with respect to O, N, C, Ta and other non-volatile impurities by sublimation.

37. Ames Process – Procedure
Sc, Dy, Ho and Er
Dry oxide
LT Fluorination of oxide
Heat mixture of Ca & REF3
Cool, remove slag
Total of three reductions in same crucible
Excluding Sc
Vacuum cast Metal loss occurs
Sublimate to purify
Machine off crucible
Arc cast into ingots

38. Ames Process
Reduction Step

39. Dysprosium metal (as Reduced)

40. Ames Process
Sublimation Step

42. Ames Process – Flow Diagram
Y, Gd, Tb and Lu
High Melting and High Boiling Points.
Volatile impurities (Ca & F) can be removed by vacuum casting without significant loss of metal
Ta solubility at MP is high, but can be removed by distillation.
Slow distillations will reduce O, N, C slightly

44. Erosion of Ta by Refluxing During Distillation
Scandium At MP ~ 3.2 at.% Ta (11.8 wt%)
Cerium, At MP ~ 0.10 at% Ta

45. Ames Process – Flow Diagram
Hey! What about me!
So why don’t we “top” Sc, Dy, Ho, and Er?
The common interstitial impurities O, N, and C that form stable compounds are left behind during sublimation.
This not is the case for Y, Gd, Tb, & Lu distillation.
ScF3 powder will absorb sufficient moisture in approximately 2 days to cause a violent reaction with the Ca reductant when heated.

46. High Purity Fluorides YF3 Praseodymium Fluoride PrF3 “Topped” LaF3
CeF3
PrF3
NdF3
SmF3
EuF3
GdF3
TbF3
DyF3
HoF3
ErF3
TmF3
YbF3
LuF3
Praseodymium Fluoride PrF3 “Topped”

47. High Purity Fluorides R2O3 + 6NH4HF2  2RF3 + 3NH3 + 3H2O
Commercial:
R2O3 + 6NH4HF2  2RF3 + 3NH3 + 3H2O
450ºC
1000 to 5000 ppm residual O
Also a source of N impurity
Ames LT:
R2O3 + 6HF(anhydrous) + Ar  2RF3 + 3H2O + Ar
650ºC
10 to 1000 ppm residual O
Pt lined furnace eliminated source of transition metal impurities.
RF3 + HF(anhydrous)  RF3 + H2O
Ames HT “Topped”:
<10 ppm residual O
Some reduction of transition metals
La – Nd, Gd, Tb, Lu
M.P.

48. High Purity Fluorides RF3 + HF(anhydrous)  RF3 + (H2O, other trace)
M.P.
RF3 + HF(anhydrous)  RF3 + (H2O, other trace)
Metal T Al Si Cr Fe Ni Cu La
Yes
Ce Yes 0.5 < Tb
Yes 0.5 <
Beaudry, B.J. & P.E. Palmer

50. Oxygen content in AT PPM of selected REM prepared from
various grades of fluorides and calcium.
La Ce Pr Nd Gd Tb Lu Y
(1)
(2)
(3)
(4)
(5)
(1) Typical commercial purity
(2) Fluoride prepared by NH4HF2 and reduced with purified calcium
(3) Topped fluoride, purified calcium, handled in air
(4) Low-temp fluoride, purified calcium, handled in glove box
(5) Topped fluoride, purified calcium, handled in glove box
Beaudry, B.J. & P.E. Palmer

51. Ames Process = High Purity
Start with pure inputs
Keep them pure
Semper Fidelis