Tin dioxide
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| Tin dioxide | |
|---|---|
| IUPAC name | Tin(IV) oxide |
| Other names | stannic oxide |
| Identifiers | |
| CAS number | [18282-10-5] |
| EINECS number | |
| Properties | |
| Molar mass | 150.708 g/mol |
| Appearance | white powder |
| Melting point |
1127 °C |
| Structure | |
| Crystal structure | P42mnm |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Tin dioxide, SnO2, also tin(IV) oxide, stannic oxide, tin peroxide, stannic anhydride, and flowers of tin, is an oxide of tin, with tin in oxidation state +4. The naturally occurring mineral is called cassiterite and this is the main ore of tin.[1] SnO2 is usually regarded as an oxygen-deficient n-type semiconductor.[2].
There are hydrous forms of SnO2 which have been described in the past as stannic acids. These have been shown to be hydrated particles of SnO2 where the composition reflects the particle size.[3]
Contents |
[edit] Preparation and chemistry
Industrially SnO2 is prepared by burning tin in air. [3] Annual production is in the range of 10 kilotons.[3]
SnO2 is insoluble in water. It is an amphoteric oxide. Reports of its solubility in acids and alkalis vary considerably. Cassiterite ore has been described as very difficult to dissolve in acids and alkalis[4]
The principal tin species produced by dissolution in halogen acids are hexahalostannate anions[5] e.g. [SnI6]2−. One report describes reacting a sample in refluxing HI for many hours.[6]
- SnO2 + 6HI → [SnI6]2− + 2H3O +
Dissolving in concentrated sulfuric acid gives the SnIV salt:[3]
- SnO2 + 2H2SO4 → Sn(SO4)2.
- Reaction with bases
In molten Na2O or NaOH SnO2 dissolves to give Na2SnO3.[3] Dissolving the solidified SnO2/NaOH melt in water gives Na2[Sn(OH)6]2, "preparing salt" which is used in the dyeing industry.[3]
SnO2 is reduced industrially to form tin metal by using carbon in a reverbatory furnace at 1200-1300°C.[7]
[edit] Structure
Cassiterite has a rutile structure like titanium dioxide, TiO2, where the tin atoms are 6 coordinate and the oxygen atoms three coordinate.[1]
[edit] Uses
As a catalyst it has been used in conjunction with vanadium oxide for oxidation of aromatic compounds in the synthesis of organic acids and acid anhydrides.[1]
SnO2 coatings can be applied using CVD, vapour deposition techniques that employ SnCl4[1] or organotin trihalides[8] e.g. butyltin trichloride as the volatile agent. This technique is used to coat glass bottles with a thin (<0.1μm) toughening layer of SnO2.[1] Thicker layers doped with Sb or F ions are electrically conducting and used in electroluminescent devices.[1]
SnO2 has been used as pigment in the manufacture of glasses, enamels and ceramic glazes. On its own SnO2 gives a milky white colour; other colours are achieved when mixed with other metallic oxides e.g. V2O5 yellow; Cr2O3 pink; and Sb2O5 grey blue.[3]
SnO2 has been used as a polishing powder[3] and is sometimes known as "putty powder", [4]
SnO2 is used in sensors of combustible gases. In these the sensor area is heated to a constant temperature (low 100s °C) and in the presence of a combustible gas the electrical resistivity drops.[9]
Doping with various compounds has been investigated (e.g. with CuO [10]). Doping with Cobalt + Manganese, gives a material that can be used in e.g. high voltage varistors.[11] Tin dioxide doped with iron or manganese is being investigated as a magnetic semiconductor [12]
[edit] References
- ^ a b c d e f Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ Solid State Chemistry: An Introduction Lesley Smart, Elaine A. Moore (2005) CRC Press ISBN 0748775161
- ^ a b c d e f g h Inorganic Chemistry, Egon Wiberg, Arnold Frederick Holleman Elsevier 2001 ISBN 0123526515
- ^ a b Inorganic & Theoretical chemistry, F. Sherwood Taylor Heineman, 6th Edition (1942)
- ^ Donaldson & Grimes in Chemistry of tin ed. P.G. Harrison Blackie (1989)
- ^ Earle R. Caley (1932). "THE ACTION OF HYDRIODIC ACID ON STANNIC OXIDE". J. Am. Chem. Soc. 54 (8): 3240–3243. doi:.
- ^ Tin: Inorganic chemistry,J L Wardell, Encyclopedia of Inorganic Chemistry ed R. Bruce King, John wiley & Son Ltd., (1995) ISBN 0471936200
- ^ US patent 4130673
- ^ Joseph Watson The stannic oxide semiconductor gas sensor in The Electrical engineering Handbook 3d Edition; Sensors Nanoscience Biomedical Engineering and Instruments ed R.C Dorf CRC Press Taylor and Francis ISBN 084937 34 68
- ^ Wang, Chun-Ming; Wang, Jin-Feng; Su, Wen-Bin (2006). "Microstructural Morphology and Electrical Properties of Copper- and Niobium-Doped Tin Dioxide Polycrystalline Varistors". Journal of the American Ceramic Society 89 (8): 2502–2508. doi:.[1]
- ^ Dibb A., Cilense M, Bueno P.R, Maniette Y., Varela J.A., Longo E. (2006). "Evaluation of Rare Earth Oxides doping SnO2.(Co0.25,Mn0.75)O-based Varistor System". Materials Research 9 (3): 339–343. doi:.
- ^ A. Punnoose, J. Hays, A. Thurber, M. H. Engelhard, R. K. Kukkadapu, C. Wang, V. Shutthanandan, and S. Thevuthasan (2005). "Development of high-temperature ferromagnetism in SnO2 and paramagnetism in SnO by Fe doping". Phys. Rev. B 72 (8): 054402. doi:.
