A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics
A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics A LANTHANIDE LANTHOLOGY (.pdf) - Davidson Physics
OXYSULFIDESAll the elements of the Lanthanide series, along with Yttrium, can form compounds with thecomposition Ln 2 O 2 S [1]. (The name usually used is oxysulfide but alternative names are thio-oxide,sulfoxide, or oxide sulfide; strict nomenclature would require the last term.) The oxysulfides can beconsidered as intermediates between the oxides and the sulfides of the corresponding elements;many features of their properties and structure reflect this. The oxysulfides, with melting pointsapproaching 2000°C, have a greater thermal stability than the sulfides to oxidation but are lessresistant than the oxides. In general the polycrystalline Ln 2 O 2 S compounds, apart from Ce 2 O 2 S, arestable in air up to 500°C.These Ln 2 O 2 S materials, perhaps unexpectedly, account indirectly for a significant fraction ofthe world's use of the Lanthanide elements. The stable compounds resulting from the Mischmetaltreatment of iron and steel are oxysulfides as is the red phosphor on almost all color TV screensand computer monitors. As a consequence, for this type of compound, much of the know-howregarding synthesis derives from the need to produce Y 2 O 2 S for TV phosphors and otheroxysulfides for X- ray screens. In contrast thermodynamic data comes from understanding the roleof Ce 2 O 2 S in steel treatment.The oxide sulfides can be prepared [1], in principle, by either :• introducing sulfur into an oxygen-containing compound e.g. with sulfur, CS 2 , H 2 S,NH 4 SCN etc., or• reducing a sulfur-containing Lanthanide compound, e.g. reduction of sulfates or oxidesulfates with H 2 or CO.The commercial production, for example, of Y 2 O 2 S and Gd 2 O 2 S involves the solid-statereaction, at 1100 - 1200 °C, of the Ln oxide with a flux of sulfur and sodium carbonate [2], e.g. :• Na 2 CO 3 + xS => Na 2 S x + CO 2 +O 2Y 2 O 3 + Na 2 S x => Y 2 O 2 S + SO 2 + Na 2 S x-2Polysulfides formed in the flux act as the sulfiding agent and, after reaction, the unwanted fluxresidue is removed by acid leaving a pure oxysulfide. Ln salts that decompose to oxide can also beused as precursors.[1] Lanthanide Oxide Sulphides, Yu.L.Suponitskii et al., Russ.Chem.Rev., 1988, 57(3), 209[2] M.R.Royce et al., U.S.Patent 3,502,590,1970: Formation process of Y 2O 2S:Eu in a Preparation with Flux,O.Kanehisa et al., J.Electrochem.Soc., 1985, 132(8), 202325
OXYSULFIDESThe alternative approach is the reduction of a sulfate, e.g. [3]:=> Ln 2 O 3 (in air)• Ln 2 (SO 4 ) 3 .nH 2 O => Ln 2 (SO 4 ) 3 => Ln 2 O 2 SO 4=> Ln 2 O 2 S (in H 2 /H 2 S)The hydrated sulfate dehydrates on heating at 600 ° C; an intermediate oxysulfate is thenseen for some Ln's before conversion to the oxysulfide occurs at ≈1000 °C. Direct oxidation of thesulfide is also a preparative route but is difficult to control.Ln compounds with a general formula (LnO) n X often have as, a general structural feature,layers of the planar poly- (LnO) n n+ ion separated by layer(s) of the component X. This structure,found in the A- and B-type light lanthanide Ln 2 O 3 oxides, is also to be seen in all the oxysulfideswhatever the Ln. Sheets of (LnO) are separated by layers of S atoms with the Ln coordinated tofour-O's from the polycation and three-S's.The thermochernical properties of several of the light Ln oxysulfides have been studied [4] asa consequence of the compounds' importance in the mischmetal treatment of steel and iron. Phasestability diagrams at 1100 K have been determined [5] for La, Ce and Y in support of research intothe high temperature desulfurization by lanthanide oxides of gaseous fuels and stack gases.The gettering or trapping of sulfur contaminants during steel production is essential tocontrol the steel's properties. The high affinity of the Ln elements for O and S ensures that "tramp"sulfur can be captured as an Ln oxysulfide. Furthermore the resulting oxysulfide remains solid evenat molten steel temperatures and is present as innocuous inclusions. (In contrast manganese sulfide,for example, is liquid under those conditions and "strings" out, as steel is rolled, producing planesof weakness within the final product.)[3] Preparation and Luminescence of Selected Eu 3+ -Activated Rare-Earth-Oxygen-Sulfur Compounds,J.W.Haynes and J.J.Brown, J.Electrochem.Soc., 1968, 115(10), 1060[4] Determination of the Standard Free Energies of Formation of Ce 2O 2S and Y 2O 2S at High Temperatures,R.ICDwivedi and D.A-R.Kay, J.Less-Comm.Met., 1984, 102, 1: Thermodynamics of the Oxidation of RareEarth Oxysulfides at High temperatures, R.ICDwivedi and D.A.R.Kay, Met.Trans.B, 1984, 15B, 523:Electrochemical Determination of Standard Gibbs Free Energies of Formation of Rare Earth Oxysulfides andOxysulfates, N.Fukatsu et al., J.Electrochem.Soc., 1985, 132(9), 2258[5] The Use of Re-O-S Phase Stability Diagrams in Gaseous Desulfurization and Iron and Steel Production,D.A-R.Kay et al., ???26
- Page 2 and 3: ALANTHANIDELANTHOLOGYPart II, M - Z
- Page 6 and 7: Compounds of the perovskite, ABO 3
- Page 8 and 9: METALSThe lanthanides, when prepare
- Page 10: METALSMetallo-thermic oxide-reducti
- Page 13 and 14: MONAZITEMonazite, a light-lanthanid
- Page 15 and 16: NEODYMIUMNeodymium is the third mos
- Page 18 and 19: [2] Preparation, Phase Equilibria,
- Page 20 and 21: NOMENCLATURE58 - 71; the term is in
- Page 22 and 23: OXALATESAddition of oxalic acid, or
- Page 24 and 25: OXIDESCalcination in air for the th
- Page 26 and 27: OXIDESFurthermore oxides with Ln IV
- Page 28 and 29: OXYCHLORIDESThermal decomposition o
- Page 32 and 33: PEROVSKITESA very wide range of mat
- Page 34 and 35: PHOSPHATESThe LnPO 4 compounds can
- Page 36 and 37: PRASEODYMIUMtransport of Pr happens
- Page 38 and 39: RESOURCESFor significant resources
- Page 40 and 41: RESOURCESSignificant new resources
- Page 42 and 43: SAMARIUMSamarium metal is made dire
- Page 44 and 45: SILICATESWithin the binary Ln 2 O 3
- Page 46 and 47: SOLVENT EXTRACTIONSome text books s
- Page 48 and 49: SULFATESLanthanide sulfates can be
- Page 50 and 51: SULFIDESThe thermochernistry of CeS
- Page 52 and 53: THULIUMThulium, the rarest of the "
- Page 54 and 55: TITANATES, TITANIUM DIOXIDELanthani
- Page 56 and 57: YTTERBIUMIn broad chemical behavior
- Page 58 and 59: YTTRIUMCompoundIdealFormulaFormula
- Page 60 and 61: YTTRIUM OXIDEThe very stable oxide,
- Page 62 and 63: YTTRIUM OXIDEThe widespread introdu
OXYSULFIDESThe alternative approach is the reduction of a sulfate, e.g. [3]:=> Ln 2 O 3 (in air)• Ln 2 (SO 4 ) 3 .nH 2 O => Ln 2 (SO 4 ) 3 => Ln 2 O 2 SO 4=> Ln 2 O 2 S (in H 2 /H 2 S)The hydrated sulfate dehydrates on heating at 600 ° C; an intermediate oxysulfate is thenseen for some Ln's before conversion to the oxysulfide occurs at ≈1000 °C. Direct oxidation of thesulfide is also a preparative route but is difficult to control.Ln compounds with a general formula (LnO) n X often have as, a general structural feature,layers of the planar poly- (LnO) n n+ ion separated by layer(s) of the component X. This structure,found in the A- and B-type light lanthanide Ln 2 O 3 oxides, is also to be seen in all the oxysulfideswhatever the Ln. Sheets of (LnO) are separated by layers of S atoms with the Ln coordinated tofour-O's from the polycation and three-S's.The thermochernical properties of several of the light Ln oxysulfides have been studied [4] asa consequence of the compounds' importance in the mischmetal treatment of steel and iron. Phasestability diagrams at 1100 K have been determined [5] for La, Ce and Y in support of research intothe high temperature desulfurization by lanthanide oxides of gaseous fuels and stack gases.The gettering or trapping of sulfur contaminants during steel production is essential tocontrol the steel's properties. The high affinity of the Ln elements for O and S ensures that "tramp"sulfur can be captured as an Ln oxysulfide. Furthermore the resulting oxysulfide remains solid evenat molten steel temperatures and is present as innocuous inclusions. (In contrast manganese sulfide,for example, is liquid under those conditions and "strings" out, as steel is rolled, producing planesof weakness within the final product.)[3] Preparation and Luminescence of Selected Eu 3+ -Activated Rare-Earth-Oxygen-Sulfur Compounds,J.W.Haynes and J.J.Brown, J.Electrochem.Soc., 1968, 115(10), 1060[4] Determination of the Standard Free Energies of Formation of Ce 2O 2S and Y 2O 2S at High Temperatures,R.ICDwivedi and D.A-R.Kay, J.Less-Comm.Met., 1984, 102, 1: Thermodynamics of the Oxidation of RareEarth Oxysulfides at High temperatures, R.ICDwivedi and D.A.R.Kay, Met.Trans.B, 1984, 15B, 523:Electrochemical Determination of Standard Gibbs Free Energies of Formation of Rare Earth Oxysulfides andOxysulfates, N.Fukatsu et al., J.Electrochem.Soc., 1985, 132(9), 2258[5] The Use of Re-O-S Phase Stability Diagrams in Gaseous Desulfurization and Iron and Steel Production,D.A-R.Kay et al., ???26
Change language