|Molar mass||128.41 g·mol−1|
|Appearance||colorless powder (alpha form)
red-brown crystal (beta form) 
6.95 g/cm3 (amorphous) solid.
|Melting point||900–1,000 °C (1,650–1,830 °F; 1,170–1,270 K)
decomposition of amorphous form
|Boiling point||1,559 °C (2,838 °F; 1,832 K) sublimation|
|4.8 mg/L (18 °C)|
|Solubility||soluble in dilute acid
slowly soluble in ammonium salts
insoluble in alkalies
|Vapor pressure||0.13 kPa (1000 °C)
2.62 kPa (1200 °C)
61.4 kPa (1500 °C)
|Band gap||2.18 eV|
|Electron mobility||531 cm2/V·s|
|Thermal conductivity||0.7 W/m·K|
Refractive index (nD)
|Crystal structure||cubic, cF8|
|Space group||Fm3m, No. 225|
|Lattice constant||a = 4.6958 Å|
Std enthalpy of
Gibbs free energy (ΔfG˚)
|GHS signal word||Danger|
|H330, H341, H350, H361, H372, H410|
|P201, P260, P273, P281, P284, P310|
|EU classification|| T+ N
Carc. Cat. 2
Muta. Cat. 3
Repr. Cat. 3
|R-phrases||R45, R26, R48/23/25, R62, R63, R68, R50/53|
|S-phrases||S53, S45, S60, S61|
LD50 (Median lethal dose)
|72 mg/kg (oral, rat)|
|US health exposure limits (NIOSH):|
|TWA 0.005 mg/m3|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
|what is: / ?)(|
Cadmium oxide is an inorganic compound with the formula CdO. It is one of the main precursors to other cadmium compounds. It crystallizes in a cubic rocksalt lattice like sodium chloride, with octahedral cation and anion centers. It occurs naturally as the rare mineral monteponite. Cadmium oxide can be found as a colorless amorphous powder or as brown or red crystals. Cadmium oxide is an n-type semiconductor with a band gap of 2.18 eV (2.31 eV) at room temperature (0 K).
Production and structure
Since cadmium compounds are often found in association with zinc ores, cadmium oxide is a common by-product of zinc refining. It is produced by burning elemental cadmium in air. Pyrolysis of other cadmium compounds, such as the nitrate or the carbonate, also affords this oxide. When pure, it is red but CdO is unusual in being available in many differing colours due to its tendency to form defect structures resulting from anion vacancies. Cadmium oxide is prepared commercially by oxidizing cadmium vapor in air.
Cadmium oxide is used in cadmium plating baths, electrodes for storage batteries, cadmium salts, catalyst, ceramic glazes, phosphors, and nematocide. Major uses for cadmium oxide are as an ingredient for electroplating baths, and in pigments.
CdO is used as a transparent conductive material, which was prepared as a transparent conducting film back in 1907. Cadmium oxide in the form of thin films has been used in applications such as photodiodes, phototransistors, photovoltaic cells, transparent electrodes, liquid crystal displays, IR detectors, and anti reflection coatings. CdO microparticles undergo bandgap excitation when exposed to UV-A light and is also selective in phenol photodegradation.
Most commercial electroplating of cadmium is done by electrodeposition from cyanide baths. These cyanide baths consist of cadmium oxide and sodium cyanide in water, which likely form cadmium cyanide and sodium hydroxide. A typical formula is 32 g/L cadmium oxide and 75 g/L sodium cyanide. The cadmium concentration may vary by as much as 50%. Brighteners are usually added to the bath and the plating is done at room temperature with high purity cadmium anodes.
CdO is a basic oxide and is thus attacked by aqueous acids to give solutions of [Cd(H2O)6]2+. Upon treatment with strong alkaline solutions, [Cd(OH)
forms. A thin coat of cadmium oxide forms on the surface of cadmium in moist air at room temperature. Cadmium will oxidize at room temperatures to form CdO. Cadmium vapor and steam will form CdO and hydrogen in a reversible reaction.
- Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. ISBN 0-07-049439-8.
- "NIOSH Pocket Guide to Chemical Hazards". Retrieved 2007-02-16.
- Cadmium oxide in Linstrom, P.J.; Mallard, W.G. (eds.) NIST Chemistry WebBook, NIST Standard Reference Database Number 69. National Institute of Standards and Technology, Gaithersburg MD. http://webbook.nist.gov (retrieved 2014-05-23)
- "INCHEM: Chemical Safety Information from Intergovernmental Organizations". Retrieved 2007-02-16.
- Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 0-618-94690-X.
- Sigma-Aldrich Co., Cadmium oxide. Retrieved on 2014-05-23.
- "NIOSH Pocket Guide to Chemical Hazards #0088". National Institute for Occupational Safety and Health (NIOSH).
- Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
- Lewis, Richard J., Sr., Hawley's condensed chemical dictionary, 13th ed., 1997, p. 189
- T. L. Chu and Shirley S. Chu (1990). "Degenerate cadmium oxide films for electronic devices". Journal of Electronic Materials 19 (9): 1003–1005. doi:10.1007/BF02652928.
- S. K. Vasheghani Farahani et al. (2013). "Temperature dependence of the direct bandgap and transport properties of CdO". Applied Physics Letters 102 (2): 022102. doi:10.1063/1.4775691.
- "Cadmium and compounds fact sheet". Archived from the original on 2006-12-10. Retrieved 2007-02-16.
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- Hampel, C. A. and Hawley, G. G. (1973). The encyclopedia of Chemistry (3rd ed.). p. 169.
- Clifford A. Hampel and Gessner G. Hawley, The encyclopedia of Chemistry, 3rd Ed., 1973, p. 169
- Varkey, A (1994). "Transparent conducting cadmium oxide thin films prepared by a solution growth technique". Thin Solid Films 239 (2): 211. doi:10.1016/0040-6090(94)90853-2.
- Dou, Y (1998). "N-type doping in CdO ceramics: a study by EELS and photoemission spectroscopy". Surface Science 398: 241. doi:10.1016/S0039-6028(98)80028-9.
- Lokhande, B (2004). "Studies on cadmium oxide sprayed thin films deposited through non-aqueous medium". Materials Chemistry and Physics 84 (2–3): 238. doi:10.1016/S0254-0584(03)00231-1.
- Karunakaran, C; Dhanalakshmi, R (2009). "Selectivity in photocatalysis by particulate semiconductors". Central European Journal of Chemistry (free download pdf)doi:10.2478/s11532-008-0083-7. 7 (1): 134.
- Clifford A. Hampel, Rare Metals Handbook, 1954, p. 87-103
|Wikimedia Commons has media related to Cadmium oxide.|
- Cadmium(II) oxide information at Webelements.