Indium(III) oxide

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Indium(III) oxide
Kristallstruktur Lanthanoid-C-Typ.png
Other names
indium trioxide, indium sesquioxide
3D model (JSmol)
ECHA InfoCard 100.013.813
Molar mass 277.64 g/mol
Appearance yellowish green odorless crystals
Density 7.179 g/cm3
Melting point 1,910 °C (3,470 °F; 2,180 K)
Band gap ~3 eV (300 K)
−56.0·10−6 cm3/mol
Cubic, space group Ia3 No. 206, cI80, a = 1.0117(1) nm, Z = 16[1]
not listed
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
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

Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium.

Physical properties[edit]

Crystal structure[edit]

Amorphous indium oxide is insoluble in water but soluble in acids, whereas crystalline indium oxide is insoluble in both water and acids. The crystalline form exist in two phases, the cubic (bixbyite type)[1] and rhombohedral (corundum type). Both phases have a band gap of about 3 eV.[2][3] The parameters of the cubic phase are listed in the infobox. The rhombohedral phase is produced at high temperatures and pressures or when using non-equilibrium growth methods.[4] It has a space group R3c No. 167, Pearson symbol hR30, a = 0.5487 nm, b = 0.5487 nm, c = 0.57818 nm, Z = 6 and calculated density 7.31 g/cm3.[5]

Conductivity and magnetism[edit]

Thin films of chromium-doped indium oxide (In2−xCrxO3) are a magnetic semiconductor displaying high-temperature ferromagnetism, single-phase crystal structure, and semiconductor behavior with high concentration of charge carriers. It has possible applications in spintronics as a material for spin injectors.[6]

Thin polycrystalline films of indium oxide doped with Zn are highly conductive (conductivity ~105 S/m) and even superconductive at helium temperatures. The superconducting transition temperature Tc depends on the doping and film structure and is below 3.3 K.[7]


Bulk samples can be prepared by heating indium(III) hydroxide or the nitrate, carbonate or sulfate.[8] Thin films of indium oxide can be prepared by sputtering of indium target in argon/oxygen atmosphere. They can be used as diffusion barriers ("barrier metals") in semiconductors, e.g. to inhibit diffusion between aluminium and silicon.[9]

Monocrystalline nanowires were synthetized from indium oxide by laser ablation, allowing precise diameter control down to 10 nm. Field effect transistors were fabricated from those.[10] Indium oxide nanowires can serve as sensitive and specific redox protein sensors.[11] Sol-gel method is another way to prepare the nanowires.

Indium oxide can serve as a semiconductor material, forming heterojunctions with p-InP, n-GaAs, n-Si, and other materials. A layer of indium oxide on a silicon substrate can be deposited from an indium trichloride solution, a method useful for manufacture of solar cells.[12]


When heated to 700 °C Indium(III) oxide forms In2O, (called indium(I) oxide or indium suboxide), at 2000 °C it decomposes.[8] It is soluble in acids but not in alkali.[8] With ammonia at high temperature indium nitride is formed [13]

In2O3 + 2 NH3 → 2 InN + 3 H2O

With K2O and indium metal the compound K5InO4 containing tetrahedral InO45− ions was prepared.[14] Reacting with a range of metal trioxides produced perovskites[15] for example:

In2O3 + Cr2O3 → 2 InCrO3


Indium oxide is used in some types of batteries, thin film infrared reflectors transparent for visible light (hot mirrors), some optical coatings, and some antistatic coatings. In combination with tin dioxide, indium oxide forms indium tin oxide (also called tin doped indium oxide or ITO), a material used for transparent conductive coatings.

In semiconductors, indium oxide can be used as an n-type semiconductor used as a resistive element in integrated circuits.[16]

In histology, indium oxide is used as a part of some stain formulations.

See also[edit]


  1. ^ a b Marezio, M. (1966). "Refinement of the crystal structure of In2O3 at two wavelengths". Acta Crystallographica. 20 (6): 723–728. doi:10.1107/S0365110X66001749.
  2. ^ Walsh, A; et al. (2008). "Nature of the Band Gap of In2O3 Revealed by First-Principles Calculations and X-Ray Spectroscopy" (PDF). Physical Review Letters. 100 (16): 167402. doi:10.1103/PhysRevLett.100.167402. PMID 18518246.
  3. ^ King, P. D. C.; Fuchs, F.; et al. (2009). "Band gap, electronic structure, and surface electron accumulation of cubic and rhombohedral In2O3". Physical Review B. 79 (20). doi:10.1103/PhysRevB.79.205211.
  4. ^ The Minerals Metals & Materials Society (Tms); The Minerals, Metals & Materials Society (TMS) (6 April 2011). TMS 2011 140th Annual Meeting and Exhibition, General Paper Selections. John Wiley and Sons. pp. 51–. ISBN 978-1-118-06215-9. Retrieved 23 September 2011.
  5. ^ Prewitt, Charles T.; Shannon, Robert D.; Rogers, Donald Burl; Sleight, Arthur W. (1969). "C rare earth oxide-corundum transition and crystal chemistry of oxides having the corundum structure". Inorganic Chemistry. 8 (9): 1985–1993. doi:10.1021/ic50079a033.
  6. ^ "New Material Puts Its Own Spin on Electronics". Biomedical Instrumentation & Technology. 40 (4): 267. 2006. doi:10.2345/i0899-8205-40-4-267.1.
  7. ^ Makise, Kazumasa; Kokubo, Nobuhito; Takada, Satoshi; Yamaguti, Takashi; Ogura, Syunsuke; Yamada, Kazumasa; Shinozaki, Bunjyu; Yano, Koki; et al. (2008). "Superconductivity in transparent zinc-doped In2O3 films having low carrier density". Science and Technology of Advanced Materials. 9 (4): 044208. doi:10.1088/1468-6996/9/4/044208. PMC 5099639. PMID 27878025.
  8. ^ a b c Downs, Anthony John (1993). Chemistry of aluminium, gallium, indium, and thallium. Springer. ISBN 0-7514-0103-X.
  9. ^ Kolawa, E. and Garland, C. and Tran, L. and Nieh, C. W. and Molarius, J. M. and Flick, W. and Nicolet, M.-A. and Wei, J. (1988). "Indium oxide diffusion barriers for Al/Si metallizations". Applied Physics Letters. 53 (26): 2644–2646. doi:10.1063/1.100541.CS1 maint: multiple names: authors list (link)
  10. ^ Li, C; Zhang, D; Han, S; Liu, X; Tang, T; Lei, B; Liu, Z; Zhou, C (2003). "Synthesis, Electronic Properties, and Applications of Indium Oxide Nanowires". Annals of the New York Academy of Sciences. 1006: 104–21. doi:10.1196/annals.1292.007. PMID 14976013.
  11. ^ "Applying Indium Oxide Nanowires as Sensitive and Specific Redox Protein Sensors". Foresight Nanotech Institute. Retrieved 2008-10-29.
  12. ^ Feng, Tom and Ghosh, Amal K. (1984) "Method for forming indium oxide/n-silicon heterojunction solar cells" U.S. Patent 4,436,765
  13. ^ Wiberg, Egon and Holleman, Arnold Frederick (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  14. ^ Lulei, M.; Hoppe, R. (1994). "Über "Orthoindate" der Alkalimetalle: Zur Kenntnis von K5[InO4]". Zeitschrift für anorganische und allgemeine Chemie. 620 (2): 210–224. doi:10.1002/zaac.19946200205.
  15. ^ Shannon, Robert D. (1967). "Synthesis of some new perovskites containing indium and thallium". Inorganic Chemistry. 6 (8): 1474–1478. doi:10.1021/ic50054a009. ISSN 0020-1669.
  16. ^ "In2O3 (Indium Oxide)". Archived from the original on 2008-06-30. Retrieved 2008-10-29.