Manganese(III) oxide

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Manganese(III) oxide
Names
Other names
dimanganese trioxide, manganese sesquioxide, manganic oxide, manganous oxide
Identifiers
3D model (
JSmol
)
ChemSpider
ECHA InfoCard
100.013.878 Edit this at Wikidata
RTECS number
  • OP915000
UNII
  • InChI=1S/2Mn.3O ☒N
    Key: GEYXPJBPASPPLI-UHFFFAOYSA-N ☒N
  • InChI=1/2Mn.3O/rMn2O3/c3-1-5-2-4
    Key: GEYXPJBPASPPLI-YNHMASKPAU
  • O=[Mn]O[Mn]=O
Properties
Mn2O3
Molar mass 157.8743 g/mol
Appearance brown or black crystalline
Density 4.50 g/cm3
Melting point 888 °C (1,630 °F; 1,161 K) (alpha form)
940 °C, decomposes (beta form)
0.00504 g/100 mL (alpha form)
0.01065 g/100 mL (beta form)
Solubility insoluble in ethanol, acetone
soluble in acid, ammonium chloride
+14,100·10−6 cm3/mol
Structure[1]
Bixbyite, cI80
Ia3 (No. 206)
a = 942 pm
Thermochemistry
110 J·mol−1·K−1[2]
Std enthalpy of
formation
fH298)
−971 kJ·mol−1[2]
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Related compounds
Other anions
manganese trifluoride, manganese(III) acetate
Other cations
chromium(III) oxide, iron(III) oxide
Related compounds
manganese(II) oxide, manganese dioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Manganese(III) oxide is a chemical compound with the formula Mn2O3. It occurs in nature as the mineral bixbyite (recently changed to bixbyite-(Mn)[3][4]) and is used in the production of ferrites and thermistors.

Preparation and chemistry

Heating

MnO2 in air at below 800 °C produces α-Mn2O3 (higher temperatures produce Mn3O4).[5] γ-Mn2O3 can be produced by oxidation followed by dehydration of manganese(II) hydroxide.[5] Many preparations of nano-crystalline Mn2O3 have been reported, for example syntheses involving oxidation of MnII salts or reduction of MnO2.[6][7][8]

Manganese(III) oxide is formed by the redox reaction in an alkaline cell:

2 MnO2 + Zn → Mn2O3 + ZnO[citation needed]

Manganese(III) oxide Mn2O3 must not be confused with MnOOH manganese(III) oxyhydroxide. Contrary to Mn2O3, MnOOH is a compound that decomposes at about 300 °C to form MnO2.[9]

Structure

Mn2O3 is unlike many other transition metal oxides in that it does not adopt the corundum (Al2O3) structure.[5] Two forms are generally recognized, α-Mn2O3 and γ-Mn2O3,[10] although a high pressure form with the CaIrO3 structure has been reported too.[11]

α-Mn2O3 has the cubic bixbyite structure, which is an example of a C-type rare earth sesquioxide (Pearson symbol cI80, space group Ia3, #206). The bixbyite structure has been found to be stabilised by the presence of small amounts of Fe3+, pure Mn2O3 has an orthorhombic structure (Pearson symbol oP24, space group Pbca, #61).[12] α-Mn2O3 undergoes antiferromagnetic transition at 80 K. [13]

γ-Mn2O3 has a structure related to the spinel structure of

Néel temperature of 39 K.[14]

ε-Mn2O3 takes on a rhombohedral ilmenite structure (the first binary compound known to do so), wherein the manganese cations divided equally into oxidation states 2+ and 4+. ε-Mn2O3 is antiferromagnetic with a Néel temperature of 210 K.[15]

References

  1. S2CID 225561660
    .
  2. ^ .
  3. ^ "Bixbyite-(Mn)".
  4. ^ IMA 21-H: Redefinition of bixbyite and definition of bixbyite-(Fe) and bixbyite-(Mn). CNMNC Newsletter, 64, 2021; Mineralogical Magazine, 85, 2021).
  5. ^ .
  6. .
  7. .
  8. .
  9. .
  10. ^
  11. ^ High Pressure Phase transition in Mn2O3 to the CaIrO3-type Phase Santillan, J.; Shim, S. American Geophysical Union, Fall Meeting 2005, abstract #MR23B-0050
  12. .
  13. .
  14. ^ Kim S. H; Choi B. J; Lee G.H.; Oh S. J.; Kim B.; Choi H. C.; Park J; Chang Y. (2005). "Ferrimagnetism in γ-Manganese Sesquioxide (γ−Mn2O3) Nanoparticles". Journal of the Korean Physical Society. 46 (4): 941.
  15. S2CID 237242460
    .