Germanium dioxide
From Wikipedia, the free encyclopedia
| Germanium dioxide | |
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| IUPAC name |
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| Other names | Germanium(IV) oxide Germania ACC10380 G-15 |
| Identifiers | |
| CAS number | [] |
| PubChem | |
| RTECS number | LY5240000 |
| InChI |
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| Properties | |
| Molecular formula | GeO2 |
| Molar mass | 104.61 g/mol |
| Appearance | white powder or colourless crystals |
| Density | 4.228 g/cm3 |
| Melting point |
400 °C |
| Boiling point |
1200 °C |
| Solubility in water | 5.2 g/l (25 °C) 10.7 g/l (100 °C) |
| Hazards | |
| EU Index | Not listed |
| Flash point | Non-flammable |
| Related compounds | |
| Other anions | Germanium disulfide Germanium diselenide |
| Other cations | Carbon dioxide Silicon dioxide Tin dioxide Lead dioxide |
| Related compounds | Germanium monoxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Germanium dioxide, also called germanium oxide and germania, is an inorganic compound, an oxide of germanium. Its chemical formula is GeO2. Its other names are germanic acid, G-15, and ACC10380. It forms as a passivation layer on pure germanium in contact with atmospheric oxygen.
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[edit] Structure
The forms of germanium dioxide to an extent parallel those of silicon dioxide. Hexagonal GeO2 has the same structure as β-quartz (germanium having coordination number 4); tetragonal GeO2 (the mineral argutite) has the rutile-like structure of stishovite (germanium having coordination number 6); and amorphous (glassy) GeO2 is similar to fused silica.[1]
Germanium dioxide can be prepared in both crystalline and amorphous forms. At very high pressures, the coordination number of germanium in amorphous germanium dioxide changes to 6, and when the pressure is reduced, the structure reverts back to the 4-coordinate form.[2] At high pressure, the rutile form converts to an orthorhombic CaCl2 form.[3]
[edit] Reactions
Heating germanium dioxide with powdered germanium at 1000 °C forms germanium monoxide (GeO).[1]
The rutile form of germanium dioxide is more soluble than the hexagonal form and dissolves to form germanic acid, H4GeO4 or Ge(OH)4.[4] GeO2 is only slightly soluble in acid but dissolves more readily in alkali to give germanates.[4]
Germanium dioxide is not flammable. In contact with hydrochloric acid, it releases the volatile and corrosive germanium tetrachloride.
[edit] Uses
Germanium dioxide's refractive index (1.7) and optical dispersion properties make it useful as an optical material for wide-angle lenses and in optical microscope objective lenses. It is transparent in infrared.
A mixture of silicon dioxide and germanium dioxide ("silica-germania") is used as an optical material for optical fibers and optical waveguides.[5] Controlling the ratio of the elements allows precise control of refractive index. Silica-germania glasses have lower viscosity and higher refractive index than pure silica. Germania replaced titania as the silica dopant for silica fiber, eliminating the need for subsequent heat treatment, which made the fibers brittle.[6]
Germanium dioxide is also used as a catalyst in production of polyethylene terephthalate resin,[7] and for production of other germanium compounds. It is used as a feedstock for production of some phosphors and semiconductor materials. In the manufacture of integrated circuits and transistors, germanium dioxide is a rather poor dielectric and is chemically unstable, which is one of the disadvantages of germanium in comparison with silicon.
[edit] Toxicity and medical
Germanium dioxide has low toxicity, but in higher doses it is nephrotoxic. Germanium dioxide is used as a germanium supplement in some questionable dietary supplements and "miracle cures".[8] High doses of these resulted in several cases of germanium poisonings.
[edit] References
- ^ a b Greenwood, Norman N.; Earnshaw, A. (1997), Chemistry of the Elements (2nd ed.), Oxford: Butterworth-Heinemann, ISBN 0-7506-3365-4
- ^ Formation and Structure of a Dense Octahedral Glass, M. Guthrie, C. A. Tulk, C. J. Benmore, J. Xu, J. L. Yarger, D. D. Klug, J. S. Tse, H-k. Mao, R. J. Hemley, Physical Review Letters, 93, 115502, doi:10.1103/PhysRevLett.93.115502
- ^ Structural evolution of rutile-type and CaCl2-type germanium dioxide at high pressure, J. Haines, J. M.Léger, C.Chateau, A. S.Pereira, Physics and Chemistry of Minerals, 27, 8 ,(2000), 575-582,doi:10.1007/s002690000092
- ^ a b Egon Wiberg, Arnold Frederick Holleman, (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
- ^ Robert D. Brown, Jr. (2000). "GERMANIUM". U.S. Geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf.
- ^ Chapter Iii: Optical Fiber For Communications
- ^ Thiele, Ulrich K. (2001). "The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation". International Journal of Polymeric Materials 50 (3): 387 – 394. doi:.
- ^ Tao, S.H. and Bolger, P.M. (June 1997). "Hazard Assessment of Germanium Supplements". Regulatory Toxicology and Pharmacology 25 (3): 211–219. doi:.
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