Manganese(III) oxide

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Manganese(III) oxide
CAS number 1317-34-6 YesY
PubChem 14824
RTECS number OP915000
Jmol-3D images Image 1
Molecular formula Mn2O3
Molar mass 157.8743 g/mol
Appearance brown or black crystalline
Density 9.53 g/cm3 (alpha form)
9.6 g/cm3 (beta form)
Melting point 888 °C (alpha form)
940 °C , decomp (beta form)
Solubility in water 0.00504 g/100 mL (alpha form)
0.01065 g/100 mL (beta form)
Solubility insoluble in alcohol, acetone
soluble in acid, ammonium chloride
Crystal structure Cubic, cI80[1]
Space group Ia-3, No. 206
Related compounds
Other anions manganese trifluoride, manganese(III) acetate
Other cations chromium(III) oxide, iron(III) oxide
Related compounds manganese(II) oxide, manganese dioxide
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Manganese(III) oxide is the chemical compound of formula Mn2O3.

Preparation and chemistry[edit]

Heating MnO2 in air at below 800 °C α-Mn2O3 is produced (higher temperatures produce Mn3O4).[2] γ-Mn2O3 can be produced by oxidation followed by dehydration of manganese(II) hydroxide.[2] Many preparations of nano-crystalline Mn2O3 have been reported, for example syntheses involving oxidation of MnII salts or reduction of MnO2.[3][4][5]

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

2 MnO2 + Zn → Mn2O3 + ZnO

Manganese (III) oxide Mn2O3 must not be confused with MnOOH manganese (III) oxohydroxide. Contrary to Mn2O3, MnOOH is a compound that decomposes at about 300 °C to form MnO2.[6]


Mn2O3 is unlike many other transition metal oxides in that it does not adopt the corundum (Al2O3) structure.[2] Two forms are generally recognized, α-Mn2O3 and γ-Mn2O3,[7] although a high pressure form with the CaIrO3 structure has been reported too.[8]

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).[9]

γ-Mn2O3 has a structure related to the spinel structure of Mn3O4 where the oxide ions are cubic close packed. This is similar to the relationship between γ-Fe2O3 and Fe3O4.[7] γ-Mn2O3 is ferrimagnetic with a Neel temperature of 39 K.[10]


  1. ^ Otto H.H., Baltrasch R., Brandt H.J. (1993). "Further evidence for Tl3+ in Tl-based superconductors from improved bond strength parameters involving new structural data of cubic Tl2O3". Physica C 215: 205. doi:10.1016/0921-4534(93)90382-Z. 
  2. ^ a b c Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419. 
  3. ^ Shuijin Lei, Kaibin Tang, Zhen Fang, Qiangchun Liu, Huagui Zheng (2006). "Preparation of α-Mn2O3 and MnO from thermal decomposition of MnCO3 and control of morphology". Materials Letters 60: 53. doi:10.1016/j.matlet.2005.07.0. 
  4. ^ Zhong-Yong Yuan, Tie-Zhen Ren, Gaohui Du, Bao-Lian Su (2004). "A facile preparation of single-crystalline α-Mn2O3 nanorods by ammonia-hydrothermal treatment of MnO2". Chemical Physics Letters 389: 83. doi:10.1016/j.cplett.2004.03.064. 
  5. ^ Navin Chandra, Sanjeev Bhasin, Meenakshi Sharma and Deepti Pal (2007). "A room temperature process for making Mn2O3 nano-particles and γ-MnOOH nano-rods". Materials Letters 61 (17): 3728. doi:10.1016/j.matlet.2006.12.024. 
  6. ^ Thomas Kohler, Thomas Armbruster, Eugen Libowitzky (1997). "Hydrogen Bonding and Jahn-Teller Distortion in Groutite,α-MnOOH, and Manganite,γ-MnOOH, and Their Relations to the Manganese Dioxides Ramsdellite and Pyrolusite". Journal of Solid State Chemistry 133 (2): 486–500. doi:10.1006/jssc.1997.7516. 
  7. ^ a b Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  8. ^ High Pressure Phase transition in Mn2O3 to the CaIrO3-type Phase Santillan, J.; Shim, S. American Geophysical Union, Fall Meeting 2005, abstract #MR23B-0050
  9. ^ Geller S. (1971). "Structure of α-Mn2O3, (Mn0.983Fe0.017)2O3 and (Mn0.37Fe0.63)2O3 and relation to magnetic ordering". Acta Cryst B27 (4): 821. doi:10.1107/S0567740871002966. 
  10. ^ 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.