Lanthanum(III) oxide, also known as lanthana, chemical formula La2O3, is an inorganic compound containing the rare earth elementlanthanum and oxygen. It is used in some ferroelectric materials, as a component of optical materials, and is a feedstock for certain catalysts, among other uses.
Lanthanum oxide is a white solid that is insoluble in water, but dissolves in acidic solutions. La2O3 absorbs moisture from air, converts to lanthanum hydroxide.[2] Lanthanum oxide has p-type semiconducting properties and a band gap of approximately 5.8 eV.[3] Its average room temperature resistivity is 10 kΩ·cm, which decreases with an increase in temperature. La2O3 has the lowest lattice energy of the rare earth oxides, with very high dielectric constant, ε = 27.
Structureedit
At low temperatures, La2O3 has an A-M2O3 hexagonal crystal structure. The La3+ metal atoms are surrounded by a 7 coordinate group of O2− atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above one of the octahedral faces.[4] On the other hand, at high temperatures lanthanum oxide converts to a C-M2O3 cubic crystal structure. The La3+ ion is surrounded by six O2− ions in a hexagonal configuration.[5][6]
Synthesisedit
Lanthanum oxide can crystallize in at least three polymorphs.[2]
Hexagonal La2O3 has been produced by spray pyrolysis of lanthanum chloride.[7]
2 LaCl3 + 3 H2O → La(OH)3 + 3 HCl
2 La(OH)3 → La2O3 + 3 H2O
An alternative route to obtaining hexagonal La2O3 involves precipitation of nominal La(OH)3 from aqueous solution using a combination of 2.5% NH3 and the surfactant sodium dodecyl sulfate followed by heating and stirring for 24 hours at 80 °C:
2 LaCl3 + 3 H2O + 3 NH3 → La(OH)3 + 3 [NH4]Cl
Other routes include:
2 La2S3 + 3 CO2 → 2 La2O3 + 3 CS2
Reactionsedit
Lanthanum oxide is used as an additive to develop certain ferroelectric materials, such as La-doped bismuth titanate (Bi4Ti3O12 - BLT). Lanthanum oxide is used in optical materials; often the optical glasses are doped with La2O3 to improve the glass' refractive index, chemical durability, and mechanical strength.[8]
The addition of the La2O3 to the glass melt leads to a higher glass transition temperature from 658 °C to 679 °C. The addition also leads to a higher density, microhardness, and refractive index of the glass.
Potential applicationsedit
Lanthanum oxide is most useful as a precursor to other lanthanum compounds.[9] Neither the oxide nor any of the derived materials enjoys substantial commercial value, unlike some of the other lanthanides. Many reports describe efforts toward practical applications of La2O3, as described below.
La2O3 forms glasses of high density, refractive index, and hardness. Together with oxides of tungsten, tantalum, and thorium, La2O3 improves the resistance of the glass to attack by alkali. La2O3 is an ingredient in some piezoelectric and thermoelectric materials.
^Shang, G.; Peacock, P. W.; Robertson, J. (2004). "Stability and band offsets of nitrogenated high-dielectric-constant gate oxides". Applied Physics Letters. 84 (1): 106–108. Bibcode:2004ApPhL..84..106S. doi:10.1063/1.1638896.
^Vinogradova, N. N.; Dmitruk, L. N.; Petrova, O. B. (2004). "Glass Transition and Crystallization of Glasses Based on Rare-Earth Borates". Glass Physics and Chemistry. 30: 1–5. doi:10.1023/B:GPAC.0000016391.83527.44. S2CID 94177915.
^Manoilova, O.V.; et al. (2004). "Surface acidity and basicity of La2O3, LaOCl, and LaCl3 characterized by IR spectroscopy, TPD, and DFT calculations". J. Phys. Chem. B. 108 (40): 15770–15781. doi:10.1021/jp040311m.
April 11, 2024
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Lanthanum III oxide also known as lanthana chemical formula La2O3 is an inorganic compound containing the rare earth element lanthanum and oxygen It is used in some ferroelectric materials as a component of optical materials and is a feedstock for certain catalysts among other uses Lanthanum III oxide NamesIUPAC name Lanthanum III oxideOther names Lanthanum sesquioxideLanthanaIdentifiersCAS Number 1312 81 8 Y3D model JSmol Interactive imageChemSpider 2529886 Y133008 YECHA InfoCard 100 013 819EC Number 215 200 5PubChem CID 150906RTECS number OE5330000UNII 4QI5EL790WCompTox Dashboard EPA DTXSID7051478InChI InChI 1S 2La 3O q2 3 3 2 YKey MRELNEQAGSRDBK UHFFFAOYSA N YSMILES O 2 O 2 O 2 La 3 La 3 PropertiesChemical formula La 2O 3Molar mass 325 808 g mol 1Appearance White powder hygroscopicDensity 6 51 g cm3 solidMelting point 2 315 C 4 199 F 2 588 K Boiling point 4 200 C 7 590 F 4 470 K Solubility in water InsolubleBand gap 4 3 eVMagnetic susceptibility x 78 0 10 6 cm3 molStructureCrystal structure Hexagonal hP5Space group P 3m1 No 164HazardsOccupational safety and health OHS OSH Main hazards IrritantGHS labelling Pictograms 1 Signal word Warning 1 Hazard statements H315 H319 H335 1 Precautionary statements P261 P280 P301 P310 P304 P340 P305 P351 P338 P405 P501 1 NFPA 704 fire diamond 1WFlash point Non flammableSafety data sheet SDS External SDSRelated compoundsOther anions Lanthanum III chlorideOther cations Cerium III oxideActinium III oxideRelated compounds Lanthanum aluminium oxide LaSrCoO4Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa N verify what is Y N Infobox references Contents 1 Properties 2 Structure 3 Synthesis 4 Reactions 5 Potential applications 6 ReferencesProperties edit nbsp La2O3 powderLanthanum oxide is a white solid that is insoluble in water but dissolves in acidic solutions La2O3 absorbs moisture from air converts to lanthanum hydroxide 2 Lanthanum oxide has p type semiconducting properties and a band gap of approximately 5 8 eV 3 Its average room temperature resistivity is 10 kW cm which decreases with an increase in temperature La2O3 has the lowest lattice energy of the rare earth oxides with very high dielectric constant e 27 Structure editAt low temperatures La2O3 has an A M2O3 hexagonal crystal structure The La3 metal atoms are surrounded by a 7 coordinate group of O2 atoms the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above one of the octahedral faces 4 On the other hand at high temperatures lanthanum oxide converts to a C M2O3 cubic crystal structure The La3 ion is surrounded by six O2 ions in a hexagonal configuration 5 6 Synthesis editLanthanum oxide can crystallize in at least three polymorphs 2 Hexagonal La2O3 has been produced by spray pyrolysis of lanthanum chloride 7 2 LaCl3 3 H2O La OH 3 3 HCl 2 La OH 3 La2O3 3 H2OAn alternative route to obtaining hexagonal La2O3 involves precipitation of nominal La OH 3 from aqueous solution using a combination of 2 5 NH3 and the surfactant sodium dodecyl sulfate followed by heating and stirring for 24 hours at 80 C 2 LaCl3 3 H2O 3 NH3 La OH 3 3 NH4 ClOther routes include 2 La2S3 3 CO2 2 La2O3 3 CS2Reactions editLanthanum oxide is used as an additive to develop certain ferroelectric materials such as La doped bismuth titanate Bi4Ti3O12 BLT Lanthanum oxide is used in optical materials often the optical glasses are doped with La2O3 to improve the glass refractive index chemical durability and mechanical strength 8 3 B2O3 La2O3 2 La BO2 3 clarification needed The addition of the La2O3 to the glass melt leads to a higher glass transition temperature from 658 C to 679 C The addition also leads to a higher density microhardness and refractive index of the glass Potential applications editLanthanum oxide is most useful as a precursor to other lanthanum compounds 9 Neither the oxide nor any of the derived materials enjoys substantial commercial value unlike some of the other lanthanides Many reports describe efforts toward practical applications of La2O3 as described below La2O3 forms glasses of high density refractive index and hardness Together with oxides of tungsten tantalum and thorium La2O3 improves the resistance of the glass to attack by alkali La2O3 is an ingredient in some piezoelectric and thermoelectric materials La2O3 has been examined for the oxidative coupling of methane 10 References edit a b c d Lanthanum Oxide American Elements Retrieved October 26 2018 a b Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 Shang G Peacock P W Robertson J 2004 Stability and band offsets of nitrogenated high dielectric constant gate oxides Applied Physics Letters 84 1 106 108 Bibcode 2004ApPhL 84 106S doi 10 1063 1 1638896 Wells A F 1984 Structural Inorganic Chemistry Oxford Clarendon Press p 546 Wyckoff R W G 1963 Crystal Structures Inorganic Compounds RXn RnMX2 RnMX3 New York Interscience Publishers Adachi Gin ya Imanaka Nobuhito 1998 The Binary Rare Earth Oxides Chemical Reviews 98 4 1479 1514 doi 10 1021 cr940055h PMID 11848940 Kale S S Jadhav K R Patil P S Gujar T P Lokhande C D 2005 Characterizations of spray deposited lanthanum oxide La2O3 thin films Materials Letters 59 24 25 3007 3009 doi 10 1016 j matlet 2005 02 091 Vinogradova N N Dmitruk L N Petrova O B 2004 Glass Transition and Crystallization of Glasses Based on Rare Earth Borates Glass Physics and Chemistry 30 1 5 doi 10 1023 B GPAC 0000016391 83527 44 S2CID 94177915 Lanthanum has also found modest uses Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann p 946 ISBN 978 0 08 037941 8 Manoilova O V et al 2004 Surface acidity and basicity of La2O3 LaOCl and LaCl3 characterized by IR spectroscopy TPD and DFT calculations J Phys Chem B 108 40 15770 15781 doi 10 1021 jp040311m Retrieved from https en wikipedia org w index php title Lanthanum oxide amp oldid 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