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Cadmium oxide
IUPAC name	Cadmium oxide
Other names	Cadmium(II) oxide,; Cadmium monoxide
Identifiers
CAS number	1306-19-0
EC number	215-146-2
UN number	2570
RTECS number	EV1925000
Properties
Molecular formula	CdO
Molar mass	128.41 g mol−1
Appearance	colorless powder (alpha form); red-brown crystal (beta form)
Density	8.150 g/cm3(crystalline),; 6.95 g/cm3 (amorphous) solid.
Melting point	900-1000 °C (decomposition of amorphous form)
Boiling point	1559 °C (sublimation)
Solubility in water	insoluble
Solubility in acid and alkaline	degrades
Electron mobility	531 cm2/V s
Magnetic susceptibility	-3 × 10−5 cm3/mol
Thermal conductivity	0.7 W/m-K
Structure
Crystal structure	cubic, cF8
Space group	Fm3m, No. 225
Lattice constant	a = 4.6958 Å
Hazards
MSDS	External MSDS
EU Index	048-002-00-0
EU classification	Carc. Cat. 2; Muta. Cat. 3; Repr. Cat. 3; Very toxic (T+); Dangerous for the environment (N)
R-phrases	R45, R26, R48/23/25, R62, R63, R68, R50/53
S-phrases	S53, S45, S60, S61
NFPA 704	0 4 0
Flash point	Non-flammable
Related compounds
Other anions	Cadmium sulfide; Cadmium selenide; Cadmium telluride
Other cations	Zinc oxide; Mercury oxide
	(what is this?) (verify); Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
	Infobox references

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.^[4] It rarely occurs naturally as the mineral monteponite. Cadmium oxide can found as a colorless amorphous powder or as brown or red crystals.^[5] Cadmium oxide is n-type semiconductor.^[6]

[edit] Production and structure

Since cadmium compounds are often found in association with zinc ores, cadmium oxide is a common by-product of zinc refining.^[7]. 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.^[8] Cadmium oxide is prepared commercially by oxidizing cadmium vapor in air.^[9]

[edit] Uses

CdO is used as a transparent conductive material,^[10] which was prepared as a transparent conducting film back in 1907.^[11] 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.^[12] CdO microparticles undergo bandgap excitation when exposed to UV-A light and is also selective in phenol photodegradation.^[13]

Cadmium oxide is used in cadmium plating baths, electrodes for storage batteries, cadmium salts, catalyst, ceramic glazes, phosphors, and nematocide.^[5] Major uses for cadmium oxide is as an ingredient for electroplating baths and in pigments.^[14] 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.^[15]

[edit] Reactivity

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)₄]^2- forms. A thin coat of cadmium oxide forms on the surface of cadmium in moist air at room temperature.[14] Cadmium will oxidize at room temperatures to form CdO.^[15] Cadmium vapor and steam will form CdO and hydrogen in a reversible reaction.^[15]

[edit] Health Risks

Cadmium oxide is a known carcinogen and inhaling fumes or vapors may be fatal.^[5] Cadmium compounds are considered carcinogenic.^[2] For further information, consult the MSDS.^[16]

[edit] References

^ Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC.
^ ^a ^b "NIOSH Pocket Guide to Chemical Hazards". http://www.cdc.gov/niosh/npg/npgd0088.html. Retrieved 2007-02-16.
^ ^a ^b "INCHEM: Chemical Safety Information from Intergovernmental Organizations". http://www.inchem.org/documents/icsc/icsc/eics0117.htm. Retrieved 2007-02-16.
^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
^ ^a ^b ^c 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.
^ "Cadmium and compounds fact sheet". http://www.npi.gov.au/database/substance-info/profiles/17.html. 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. p. 169.
^ Varkey, A (1994). "Transparent conducting cadmium oxide thin films prepared by a solution growth technique". Thin Solid Films 239: 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: 238. doi:10.1016/S0254-0584(03)00231-1.
^ Karunakaran, C; Dhanalakshmi, R (2009). "Selectivity in photocatalysis by particulate semiconductors" (free download pdf). Central European Journal of Chemistry 7 (1): 134. doi:10.2478/s11532-008-0083-7.
^ Clifford A. Hampel and Gessner G. Hawley, The encyclopedia of Chemistry, 3rd Ed., 1973, p. 169
^ ^a ^b ^c Clifford A. Hampel, Rare Metals Handbook, 1954, p. 87-103
^ "INDG391 - Cadmium and you - working with Cadmium - are you at risk ?" (PDF). UK Health and Safety Executive Leaflet. http://www.hse.gov.uk/pubns/indg391.pdf. Retrieved 2007-02-16.

[edit] External links

Cadmium(II) oxide information at Webelements.

[0] Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC.

[NIOSH_sheet-1] "NIOSH Pocket Guide to Chemical Hazards". http://www.cdc.gov/niosh/npg/npgd0088.html. Retrieved 2007-02-16.

[INCHEM_sheet-2] "INCHEM: Chemical Safety Information from Intergovernmental Organizations". http://www.inchem.org/documents/icsc/icsc/eics0117.htm. Retrieved 2007-02-16.

[3] Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.

[Lewis.2C_Richard_J._1997.2C_p._189-4] Lewis, Richard J., Sr., Hawley's condensed chemical dictionary, 13th ed., 1997, p. 189

[5] 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.

[6] "Cadmium and compounds fact sheet". http://www.npi.gov.au/database/substance-info/profiles/17.html. Retrieved 2007-02-16.

[7] Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

[8] Hampel, C. A. and Hawley, G. G. (1973). The encyclopedia of Chemistry. p. 169.

[9] Varkey, A (1994). "Transparent conducting cadmium oxide thin films prepared by a solution growth technique". Thin Solid Films 239: 211. doi:10.1016/0040-6090(94)90853-2.

[10] 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.

[11] Lokhande, B (2004). "Studies on cadmium oxide sprayed thin films deposited through non-aqueous medium". Materials Chemistry and Physics 84: 238. doi:10.1016/S0254-0584(03)00231-1.

[12] Karunakaran, C; Dhanalakshmi, R (2009). "Selectivity in photocatalysis by particulate semiconductors" (free download pdf). Central European Journal of Chemistry 7 (1): 134. doi:10.2478/s11532-008-0083-7.

[13] Clifford A. Hampel and Gessner G. Hawley, The encyclopedia of Chemistry, 3rd Ed., 1973, p. 169

[Clifford_A._Hampel_1954.2C_p._87-103-14] Clifford A. Hampel, Rare Metals Handbook, 1954, p. 87-103

[HES_UK-15] "INDG391 - Cadmium and you - working with Cadmium - are you at risk ?" (PDF). UK Health and Safety Executive Leaflet. http://www.hse.gov.uk/pubns/indg391.pdf. Retrieved 2007-02-16.

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