Tin(IV) oxide
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| Names | |
|---|---|
| IUPAC name
Tin dioxide
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| Other names | |
| Identifiers | |
| ECHA InfoCard | 100.038.311 |
| EC Number |
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| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |
| SnO2 | |
| Molar mass | 150.71 g/mol |
| Appearance | white powder |
| Density | 6.95 g/cm3 |
| Melting point | 1630 °C |
| Boiling point | 1800–1900 °C |
| insoluble | |
Refractive index (nD)
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2.006 |
| Structure | |
| Rutile (tetragonal), tP6 | |
| P42/mnm, No. 136 | |
| Octahedral (SnIV); trigonal planar (O2–) | |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
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Tin disulfide |
Other cations
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Carbon dioxide Silicon dioxide Titanium dioxide Germanium dioxide Zirconium dioxide Hafnium dioxide Lead dioxide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Tin dioxide is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin.[1] With many other names (see infobox), this oxide of tin is the most important raw material in tin chemistry. This colourless, diamagnetic solid is amphoteric.
Structure
It crystallises with the rutile structure, wherein the tin atoms are 6 coordinate and the oxygen atoms three coordinate.[1] SnO2 is usually regarded as an oxygen-deficient n-type semiconductor.[2] Hydrous forms of SnO2 have been described in the past as stannic acids, although such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size.[3]
Preparation
Tin dioxide occurs naturally but is purified by reduction to the metal followed by burning tin in air.[3] Annual production is in the range of 10 kilotons.[3] SnO2 is reduced industrially to the metal with carbon in a reverbatory furnace at 1200-1300 °C.[4]
Amphoterism
Although SnO2 is insoluble in water, it is an amphoteric oxide, although cassiterite ore has been described as difficult to dissolve in acids and alkalis.[5] "Stannic acid" refers to hydrated tin dioxide, SnO2, which is also called "stannic hydroxide."
Tin oxides dissolve in acids. Halogen acids attack SnO2 to give hexahalostannates,[6] such as [SnI6]2-. One report describes reacting a sample in refluxing HI for many hours.[7]
- SnO2 + 6 HI → H2SnI6 + 2 H2O
Similarly, SnO2 dissolves in sulfuric acid to give the sulfate:[3]
- SnO2 + 2 H2SO4 → Sn(SO4)2 + 2 H2O
SnO2 dissolves in strong base to give "stannates," with the nominal formula Na2SnO3.[3] Dissolving the solidified SnO2/NaOH melt in water gives Na2[Sn(OH)6]2, "preparing salt," which is used in the dye industry.[3]
Uses
In conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides.[1]
Tin dioxide has long been used as an opacifier and as a white colorant in ceramic glazes.[8] Its use has been particular common in glazes for earthenware, sanitaryware and wall tiles; see the articles tin-glazing and Tin-glazed pottery. Tin oxide remains in suspension in vitreous matrix of the fired glazes, and, with its high refractive index being sufficiently different from the matrix, light is scattered, and hence increases the opacity of the glaze. The degree of dissolution increases with the firing temperature, and hence the extent of opacity diminishes.[9] Although dependant on the other constituents the solubility of tin oxide in glaze melts is generally low. Its solubility is increased by Na2, K2 and B2O3, and reduced by CaO, BaO, ZnO, Al2O3, and to a limited extent PbO.[10]
SnO2 wires are commonly used as the detecting element in carbon monoxide detectors.
SnO2 coatings can be applied using chemical vapor deposition, vapour deposition techniques that employ SnCl4[1] or organotin trihalides[11] e.g. butyltin trichloride as the volatile agent. This technique is used to coat glass bottles with a thin (<0.1 μm) layer of SnO2, which helps to adhere a subsequent, protective polymer coating such as polyethylene to the glass.[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. Pure 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",[5] SnO2 is used in sensors of combustible gases. In these the sensor area is heated to a constant temperature (few hundred °C) and in the presence of a combustible gas the electrical resistivity drops.[12] Doping with various compounds has been investigated (e.g. with CuO [13]). Doping with cobalt and manganese, gives a material that can be used in e.g. high voltage varistors.[14] Tin dioxide can be doped into the oxides of iron or manganese.[15]
References
- ^ a b c d e f Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 447–48. ISBN 978-0-08-022057-4.
- ^ Solid State Chemistry: An Introduction Lesley Smart, Elaine A. Moore (2005) CRC Press ISBN 0-7487-7516-1
- ^ a b c d e f g h Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5
- ^ Tin: Inorganic chemistry,J L Wardell, Encyclopedia of Inorganic Chemistry ed R. Bruce King, John Wiley & Son Ltd., (1995) ISBN 0-471-93620-0
- ^ 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:10.1021/ja01347a028.
- ^ ’The Glazer’s Book’ – 2nd edition. A.B.Searle.The Technical Press Limited. London. 1935.
- ^ ’A Treatise On Ceramic Industries.’ E.Bourry. Fourth edition. Scott, Greenwood & son. London. 1926.
- ^ ’Ceramic Glazes’ Third edition. C.W.Parmelee & C.G.Harman. Cahners Books, Boston, Massachusetts. 1973.
- ^ US 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 0-8493-7346-8
- ^
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:10.1111/j.1551-2916.2006.01076.x.
{{cite journal}}: CS1 maint: multiple names: authors list (link)[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:10.1590/S1516-14392006000300015.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^
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:10.1103/PhysRevB.72.054402.
{{cite journal}}: CS1 maint: multiple names: authors list (link)