1 High Purity Rare Earth Metals Preparation 2011Materials Preparation Center A US Department of Energy Specialized Research CenterHigh Purity Rare Earth Metals PreparationTrevor M. RiedemannManager, MPC Rare Earth Materials Section122 Metals Development BuildingAmes LaboratoryAmes, IAPhone:Fax:
2 AcknowledgementsThe 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. LograssoDivision DirectorDivision of Materials Science & Engineering124 Metals Development BuildingAmes, IAPhone:Fax:Lawrence L. JonesDirector, MPC121 Metals Development BuildingAmes LaboratoryAmes, IAPhone:Fax:
3 AcknowledgementsThe 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 EarthsRare Earth Information Center IS-RIC 10Institute for Physical Research and TechnologyIowa State UniversityK.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 EarthsRare Earth Information Center IS-RIC 10Institute for Physical Research and TechnologyIowa State UniversityK.A. Gschneidner Jr & J. Capellen, ed.
6 The Rare Earths - Abundance US Geological Survey Fact SheetRare Earth Elements – Critical Resources for High TechnologyGordon B. Haxel, James B. Hedrick, and Greta J. Orris
7 High Purity Oxide Prices La2O3CeO2Pr6O11Nd2O3Sm2O3Eu2O3Gd2O3Tb4O7Dy2O3Ho2O3Er2O3Tm2O3Yb2O3Lu2O3III / IVDy 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 increasedsignificantly and some hoarding and speculating took place in the secondhalf of that year. Demand grew faster than actual output, reaching a virtualbalance in 2000 but diverged again in Dy prices went through theroof in 2000 only to come crushing down in the second half of 2001, asshown in Figure 2. At the end of 2003, the supply/demand spread startedto close again, which was reflected in prices rising sharply in the thirdquarter of 2003 and continuing strong. As indicated in Figure 5, with thelimited availability of Dy, it does not take much of an increase in demandto trigger an imbalance, particularly since Dy is used in magnetic alloysand electronic ceramic chips, both of which are growing strongly again.We expect the Dy tightness to continue.(d) TerbiumTb has a similar functionality as Dy in magnetic alloys and certainproducers favour Tb over Dy. Still, not a lot of Tb is used in magneticalloys and for good reasons. Two things should be apparent when oneexamines Figure 6. First, the availability of Tb is about two orders ofmagnitude lower than Nd and, second, Tb consumption has traditionallybeen 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 SymposiumGlobal Markets and Business OpportunitiesMay 17-21, 2004, Xi’an, ChinaConstantine E. Karayannopoulos
8 High Purity Oxide Prices La2O3CeO2Pr6O11Nd2O3Sm2O3Eu2O3Gd2O3Tb4O7Dy2O3Ho2O3Er2O3Tm2O3Yb2O3Lu2O3III / IV/2010La 99% US$/kgCe 99% US$/kgPr 99% US$/kgNd 99% US$/kgEu 99% US$/kgTb 99% US$/kgDy 99% US$/kgDy 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 increasedsignificantly and some hoarding and speculating took place in the secondhalf of that year. Demand grew faster than actual output, reaching a virtualbalance in 2000 but diverged again in Dy prices went through theroof in 2000 only to come crushing down in the second half of 2001, asshown in Figure 2. At the end of 2003, the supply/demand spread startedto close again, which was reflected in prices rising sharply in the thirdquarter of 2003 and continuing strong. As indicated in Figure 5, with thelimited availability of Dy, it does not take much of an increase in demandto trigger an imbalance, particularly since Dy is used in magnetic alloysand electronic ceramic chips, both of which are growing strongly again.We expect the Dy tightness to continue.(d) TerbiumTb has a similar functionality as Dy in magnetic alloys and certainproducers favour Tb over Dy. Still, not a lot of Tb is used in magneticalloys and for good reasons. Two things should be apparent when oneexamines Figure 6. First, the availability of Tb is about two orders ofmagnitude lower than Nd and, second, Tb consumption has traditionallybeen in much closer balance with output than most rare earths.Source: Metal Pages
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 metalR2O3 + 6HF 2RF3 + 3H2O3Ca + 2RF3 2R + 3CaF2R2O3 + 2La La2O3 + 2R
11 ? Ames Process = High purity Impurity Sources: Oxygen: Incomplete oxide conversionCalcium reductantAtmosphere (handling and processing)N, C, & H: Adsorbed on oxide/fluorideTantalum CrucibleAtmosphereCa & F: Reductant and incomplete reduction (10% excess Ca is used in Rx)Insufficient vacuum castingFe, Co, Ni & Cu: Tantalum CrucibleImpurities in oxide & HFContamination of oxide during handlingCross Contaminationin Processing LineFoundry vs Chip Fab
13 Anlaysis of three commercial Tb samples and MPC Tb (ppm at). Source A Source D MPCImpurity Ingot Distilled Distilled DistilledHC n.a. n.a. n.aNOFeLaTaTotal mag. REat% pure <97.5 <95.6 <94.2 <99.81Semiquantitative 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 PurificationTechnology and New Functional Materials Creation of Rare Earth Metals,Society of Non-Traditional Technology, Tokyo, Japan (1989) pp 13-29K.A. Gschneidner, Jr.
14 Why do we need High Purity Metals? Impurities affect the basic properties of pure metals (and alloys)Lattice parametersCrystal structureMelting pointHardnessStrengthResistivitySusceptibilityGrain growthMagnetic domain wall motionStoichiometry of alloy is shiftedSecond phase can form and change the properties.Crystal GrowthOxygen as impurity in crystal growth of intermetallics, D. Souptel, W. Lo¨ ser, W. Gruner, G. Behr, Journal of Crystal Growth 307 (2007) 410–420Impurities may mask theINTRINSIC behavior of thepure metal or alloy material
15 Why do we need High Purity Metals? V. K. Pecharsky and K. A. Gschneidner, Jr.Giant Magnetocaloric Effect in Gd5Si2Ge2Physical Review Letters 78 (1997) No. 23T. Zhang , et. Al (Sichuan University)The structure and magnetocaloric effect of rapidly quenched Gd5Si2Ge2 alloy with low-purity gadoliniumMaterials Letters 61 (2007) 440–443K. A. Gschneidner, Jr., et al.Method of Making Active Magentic Refrigerant, Colossal Magnetostriction and Giant Magentoresistive Materials Based on Gd-Si-Ge AlloysUS Patent: 6,589,366 B1 (2003)-ΔSm (J/kg K)Impurities are suppressing a structural transition from orthorhombic to monoclinicGd5Si2Ge2 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 TTemperature (K)
16 Why do we need High Purity Metals? Y. Matsumoto, et al.Quantum Criticality Without Tuning in the Mixed ValenceCompound -YbAlB4.Science, 2011; 331 (6015)S. Nakatsuji, et al.Superconductivity and quantum criticality in the heavy-fermionsystem –YbAlB4Nature Physics 4, (2008)Robin T. Macaluso, et. alCrystal Structure and Physical Properties of Polymorphs of LnAlB4(Ln = Yb, Lu)Chem. Mater., 2007, 19 (8), pp 1918–1922An exotic new superconductor based on the elementytterbium displays unusual properties that could changehow scientists understand and create materials forsuperconductors and electronics. Beta-YbAlB4, canreach a quantum critical, without being subject tomassive changes in pressure, magnetic fields,or chemical impurities.
17 High Purity Oxides Inputs: Oxides GARBAGE IN = GARBAGE OUT Y2O3 La2O3 CeO2Pr6O11Nd2O3Sm2O3Eu2O3Gd2O3Tb4O7Dy2O3Ho2O3Er2O3Tm2O3Yb2O3Lu2O3III / IVGARBAGE IN = GARBAGE OUTPraseodymium OxidePr6O1199.999% 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 Days900 g/runCe 1900g CaLu g CaOxygen content is lowered <10 ppmGlove box protectedCa readily picks up O from H2O>1000 ppm from air in 5 minutesThe 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 MagnesiaQuartzZirconiaGraphiteIronXXXXX
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 bothASTM B708 – 05 R05400, unalloyed tantalum, powder-metallurgy consolidationElement R R05400CONHFeMoNbNiSiTiWCleanest Ta: PickledAnnealed2000ºC degassed
22 Nasty Stuff Inputs: Hydrofluoric Acid (HF) Purity range from 99% to 99.99%Parameter Level †HF wt%H2SO wt ppmSO wt ppmH2O wt ppmAs wt ppmHydrofluosilicic mol %*†Honeywell Specifications*Handbook of Compressed Gasses, 4th ed. (1999) H2SiF6IDLH = 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)OSHAPermissible Exposure Limit (PEL) = 3 ppm 8 hoursShort 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 StuffNot a lot of impurities to worry about…but…..
23 1 2 3 4 The Rare Earths - Physical Properties Vapor Pressure at Melting PointTm mm HgCe 3.6(10)-12 mm Hg
25 Ames Process – Flow Diagram Sm, Eu, Tm and YbLow Boiling PointsReduction by Lanthanum from OxideEasily purified by SublimationSm, Eu, Tm and Yb can be melted in Ta crucibles without Ta contaminationTm is very difficult to arc melt due to ~74mm vapor pressure at its melting point
26 Ames Process – Procedure Sm, Eu, Tm and YbDry Oxide Removes H2O and CO2Machine lanthanum chipsMix oxide and La chips (in dry box)Pack in crucible (in dry box)Load into induction furnaceHeat under vacuum.Hold for 8 hoursPerform a low temp sublimation.Strip Ta from sublimate massEuropium is extruded.
29 Ames Process – Flow Diagram La, Ce, Nd and PrLow Melting but high Boiling PointsVolatile impurities (Ca & F) can be quantitatively removed by vacuum casting without loss of metalTa 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 PrDry OxideLT/HT Fluorination of oxideHeat mixture of Ca & REF3Cool, remove slagTotal of three reductions in same crucibleVacuum cast at high temperatureCool to just above melting point.Hold to precipitate tantalumDecant or “pour” RE into thin wall crucibleMachine off crucibleArc cast into ingots
36 Ames Process – Flow Diagram Sc, Dy, Ho and ErHigh Melting and low to intermediate Boiling Points.To remove F impurity thru vacuum casting, must loose up to 30% of metalEasily purified with respect to O, N, C, Ta and other non-volatile impurities by sublimation.
37 Ames Process – Procedure Sc, Dy, Ho and ErDry oxideLT Fluorination of oxideHeat mixture of Ca & REF3Cool, remove slagTotal of three reductions in same crucibleExcluding ScVacuum cast Metal loss occursSublimate to purifyMachine off crucibleArc cast into ingots
42 Ames Process – Flow Diagram Y, Gd, Tb and LuHigh Melting and High Boiling Points.Volatile impurities (Ca & F) can be removed by vacuum casting without significant loss of metalTa 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.
47 High Purity Fluorides R2O3 + 6NH4HF2 2RF3 + 3NH3 + 3H2O Commercial:R2O3 + 6NH4HF2 2RF3 + 3NH3 + 3H2O450ºC1000 to 5000 ppm residual OAlso a source of N impurityAmes LT:R2O3 + 6HF(anhydrous) + Ar 2RF3 + 3H2O + Ar650ºC10 to 1000 ppm residual OPt lined furnace eliminated source of transition metal impurities.RF3 + HF(anhydrous) RF3 + H2OAmes HT “Topped”:<10 ppm residual OSome reduction of transition metalsLa – Nd, Gd, Tb, LuM.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 CuLaYesCe Yes 0.5 <TbYes 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 boxBeaudry, B.J. & P.E. Palmer
51 Ames Process = High Purity Start with pure inputsKeep them pureSemper Fidelis