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Samarium(III) oxide
IUPAC name
samarium(III) oxide
Other names
samarium sesquioxide, samaria
  • 12060-58-1 checkY
3D model (JSmol)
ECHA InfoCard 100.031.845 Edit this at Wikidata
EC Number
  • 235-043-6
  • InChI=1S/3O.2Sm/q3*-2;2*+3 checkY
  • O=[Sm]O[Sm]=O
  • [Sm+3].[Sm+3].[O-2].[O-2].[O-2]
Molar mass 348.72 g/mol
Appearance yellow-white crystals
Density 8.347 g/cm3
Melting point 2,335 °C (4,235 °F; 2,608 K)
Boiling point Not Stated
+1988.0·10−6 cm3/mol
not listed
Related compounds
Other anions
Samarium(III) chloride
Other cations
Promethium(III) oxide, Europium(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Samarium(III) oxide (Sm2O3) is a chemical compound. Samarium oxide readily forms on the surface of samarium metal under humid conditions or temperatures in excess of 150°C in dry air. Similar to the metal, iron, this oxide layer spalls off the surface of the metal, exposing more metal to continue the reaction. The oxide is commonly white to off yellow in color and is often encountered as a highly fine dust like powder.


Samarium(III) oxide is used in optical and infrared absorbing glass to absorb infrared radiation. Also, it is used as a neutron absorber in control rods for nuclear power reactors. The oxide catalyzes the dehydration and dehydrogenation of primary and secondary alcohols.[1] Another use involves preparation of other samarium salts. [2]


Samarium(III) oxide may be prepared by two methods:

1. thermal decomposition of samarium(III) carbonate, hydroxide, nitrate, oxalate or sulfate:

Sm2(CO3)3 → Sm2O3 + 3 CO2

2. by burning the metal in air or oxygen at a temperature above 150 °C:

4 Sm + 3 O2 → 2 Sm2O3


Samarium(III) oxide dissolves in mineral acids, forming salts upon evaporation and crystallization:

Sm2O3 + 6 HCl → 2 SmCl3 + 3 H2O

The oxide can be reduced to metallic samarium by heating with a reducing agent, such as hydrogen or carbon monoxide, at elevated temperatures.


  1. ^ Catalytic properties of samarium oxide with respect to the dehydrogenation and dehydration of alcohols and the dehydrogenation of tetralin. Bulletin of the Academy of Sciences of the USSR, Division of chemical science, January 1964, Volume 13, Issue 1, pp 6–9.
  2. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8