Lanthanum oxide

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Lanthanum(III) oxide
Lanthanum(III) oxide
Names
IUPAC name
Lanthanum(III) oxide
Other names
Lanthanum sesquioxide
Lanthana
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
 100.013.819 Edit this at Wikidata
EC Number
  • 215-200-5
RTECS number
  • OE5330000
UNII
  • InChI=1S/2La.3O/q2*+3;3*-2 checkY
    Key: MRELNEQAGSRDBK-UHFFFAOYSA-N checkY
  • [O-2].[O-2].[O-2].[La+3].[La+3]
Properties
La2O3
Molar mass 325.808 g·mol−1
Appearance White powder,
hygroscopic
Density 6.51 g/cm3, solid
Melting point 2,315 °C (4,199 °F; 2,588 K)
Boiling point 4,200 °C (7,590 °F; 4,470 K)
Insoluble
Band gap 4.3 eV
−78.0·10−6 cm3/mol
Structure
Hexagonal, hP5
P-3m1, No. 164
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Irritant
GHS labelling:
GHS07: Exclamation mark[1]
Warning[1]
H315, H319, H335[1]
P261, P280, P301+P310, P304+P340, P305+P351+P338, P405, P501[1]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability (red): no hazard codeInstability (yellow): no hazard codeSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
1
W
Flash point Non-flammable
Safety data sheet (SDS) External SDS
Related compounds
Other anions
 Lanthanum(III) chloride
Other cations
 Cerium(III) oxide
Actinium(III) oxide
Related compounds
 Lanthanum aluminium oxide,
LaSrCoO4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Lanthanum(III) oxide, also known as lanthana, chemical formula La2O3, is an

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.

Properties

La2O3 powder

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.

dielectric constant
, ε = 27.

Structure

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]

Synthesis

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

Reactions

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]

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

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

piezoelectric
and thermoelectric materials.

La2O3 has been examined for the oxidative coupling of methane.[10]

References

  1. ^ a b c d "Lanthanum Oxide". American Elements. Retrieved October 26, 2018.
  2. ^
    ISBN 978-0-08-037941-8
    .
  3. doi:10.1063/1.1638896
    .
  4. ^ Wells, A.F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press. p. 546.
  5. ^ Wyckoff, R. W.G. (1963). Crystal Structures: Inorganic Compounds RXn, RnMX2, RnMX3. New York: Interscience Publishers.
  6. PMID 11848940
    .
  7. doi:10.1016/j.matlet.2005.02.091
    .
  8. S2CID 94177915
    .
  9. ISBN 978-0-08-037941-8
    .
  10. doi:10.1021/jp040311m
    .
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