138.253.124.43 (talk) Mistake between the solubilities of the hexagonal and rutile forms (cf. Pourbaix diagrams) |
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| ImageFileR1 = GeO2powder.jpg |
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| IUPACName = Germanium dioxide |
| IUPACName = Germanium dioxide |
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| OtherNames = Germanium(IV) oxide<br/>Germania<br/>ACC10380<br/>G-15<br/>Germanium oxide<br/>Germanic acid<br/>Germanic oxide |
| OtherNames = Germanium(IV) oxide<br/>Germania<br/>ACC10380<br/>G-15<br/>Germanium oxide<br/>Germanic acid<br/>Germanic oxide |
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'''Germanium dioxide''', also called |
'''Germanium dioxide''', also called germanium oxide and germania, is the [[inorganic compound]] with the chemical formula [[Germanium|Ge]][[Oxide|O]]<sub>2</sub>. It is the main commercial source of germanium. forms as a [[Passivation (chemistry)|passivation layer]] on pure germanium in contact with atmospheric oxygen. |
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==Structure== |
==Structure== |
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The |
The two predominant polymorphs of GeO<sub>2</sub> are hexagonal and tetragonal. Hexagonal GeO<sub>2</sub> has the same structure as β-quartz, germanium having [[coordination number]] 4). Tetragonal GeO<sub>2</sub> (the mineral [[argutite]]) has the [[rutile]]-like structure seen in [[stishovite]]. In this motif, germanium has the coordination number 6). An amorphous (glassy) form of GeO<sub>2</sub> is similar to [[fused silica]].<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> |
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''tetragonal'' GeO<sub>2</sub> (the mineral [[argutite]]) has the [[rutile]]-like structure of [[stishovite]] (germanium having coordination number 6); and ''amorphous'' (glassy) GeO<sub>2</sub> is similar to [[fused silica]].<ref name = "Greenwood">{{Greenwood&Earnshaw}}</ref> |
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Germanium dioxide can be prepared in both [[crystalline]] and [[amorphous]] forms. At ambient pressure the amorphous structure is formed by a network of GeO<sub>4</sub> tetrahedra. At elevated pressure up to approximately 9 [[GPa]] the germanium average [[coordination number]] steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance.<ref name=Drewitt2010>{{Cite journal|author=J W E Drewitt, P S Salmon, A C Barnes, S Klotz, H E Fischer, W A Crichton|journal=Physical Review B|year=2010|volume=81|pages=014202|title=Structure of GeO<sub>2</sub> glass at pressures up to 8.6 GPa|doi=10.1103/PhysRevB.81.014202|bibcode = 2010PhRvB..81a4202D }}</ref> At higher pressures, up to approximately 15 [[GPa]], the germanium [[coordination number]] increases to 6 and the dense network structure is composed of GeO<sub>6</sub> octahedra.<ref name=Guthrie>{{Cite journal|title=Formation and Structure of a Dense Octahedral Glass|author=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|journal=Physical Review Letters|volume=93|issue=11|pages=115502|doi=10.1103/PhysRevLett.93.115502|pmid=15447351|year=2004|bibcode=2004PhRvL..93k5502G}}</ref> When the pressure is subsequently reduced, the structure reverts to the tetrahedral form.<ref name=Drewitt2010/><ref name=Guthrie/> At high pressure, the rutile form converts to an orthorhombic CaCl<sub>2</sub> form.<ref>Structural evolution of rutile-type and CaCl<sub>2</sub>-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}}</ref> |
Germanium dioxide can be prepared in both [[crystalline]] and [[amorphous]] forms. At ambient pressure the amorphous structure is formed by a network of GeO<sub>4</sub> tetrahedra. At elevated pressure up to approximately 9 [[GPa]] the germanium average [[coordination number]] steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance.<ref name=Drewitt2010>{{Cite journal|author=J W E Drewitt, P S Salmon, A C Barnes, S Klotz, H E Fischer, W A Crichton|journal=Physical Review B|year=2010|volume=81|pages=014202|title=Structure of GeO<sub>2</sub> glass at pressures up to 8.6 GPa|doi=10.1103/PhysRevB.81.014202|bibcode = 2010PhRvB..81a4202D }}</ref> At higher pressures, up to approximately 15 [[GPa]], the germanium [[coordination number]] increases to 6 and the dense network structure is composed of GeO<sub>6</sub> octahedra.<ref name=Guthrie>{{Cite journal|title=Formation and Structure of a Dense Octahedral Glass|author=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|journal=Physical Review Letters|volume=93|issue=11|pages=115502|doi=10.1103/PhysRevLett.93.115502|pmid=15447351|year=2004|bibcode=2004PhRvL..93k5502G}}</ref> When the pressure is subsequently reduced, the structure reverts to the tetrahedral form.<ref name=Drewitt2010/><ref name=Guthrie/> At high pressure, the rutile form converts to an orthorhombic CaCl<sub>2</sub> form.<ref>Structural evolution of rutile-type and CaCl<sub>2</sub>-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}}</ref> |
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The hexagonal (d = 4.29 g/cm3) form of germanium dioxide is more soluble than the rutile (d = 6.27 g/cm3) form and dissolves to form {{not a typo|germanic}} acid, H<sub>4</sub>GeO<sub>4</sub> or Ge(OH)<sub>4</sub>.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman, (2001) ''Inorganic Chemistry'', Elsevier ISBN 0-12-352651-5</ref> GeO<sub>2</sub> is only slightly soluble in acid but dissolves more readily in alkali to give [[germanate]]s.<ref name = "Wiberg&Holleman"/> |
The hexagonal (d = 4.29 g/cm3) form of germanium dioxide is more soluble than the rutile (d = 6.27 g/cm3) form and dissolves to form {{not a typo|germanic}} acid, H<sub>4</sub>GeO<sub>4</sub> or Ge(OH)<sub>4</sub>.<ref name = "Wiberg&Holleman">Egon Wiberg, Arnold Frederick Holleman, (2001) ''Inorganic Chemistry'', Elsevier ISBN 0-12-352651-5</ref> GeO<sub>2</sub> is only slightly soluble in acid but dissolves more readily in alkali to give [[germanate]]s.<ref name = "Wiberg&Holleman"/> |
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In contact with [[hydrochloric acid]], it releases the volatile and corrosive [[germanium tetrachloride]]. |
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==Uses== |
==Uses== |
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Germanium dioxide is also used as a [[catalyst]] in production of [[polyethylene terephthalate]] resin,<ref name=Thiele>{{cite journal | author = Thiele, Ulrich K. | year = 2001 | title = The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation | journal = International Journal of Polymeric Materials | volume = 50 | issue = 3 | pages = 387–394 |doi = 10.1080/00914030108035115 }}</ref> and for production of other germanium compounds. It is used as a feedstock for production of some [[phosphor]]s and [[semiconductor material]]s. |
Germanium dioxide is also used as a [[catalyst]] in production of [[polyethylene terephthalate]] resin,<ref name=Thiele>{{cite journal | author = Thiele, Ulrich K. | year = 2001 | title = The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation | journal = International Journal of Polymeric Materials | volume = 50 | issue = 3 | pages = 387–394 |doi = 10.1080/00914030108035115 }}</ref> and for production of other germanium compounds. It is used as a feedstock for production of some [[phosphor]]s and [[semiconductor material]]s. |
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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. |
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Furthermore germanium dioxide is used in [[algaculture]] as an inhibitor of unwanted [[diatom]] growth in algal cultures since a contamination with the comparatively fast-growing diatoms often inhibits the growth of or outcompetes the original algae strains. GeO<sub>2</sub> is readily taken up by diatoms and leads to silicon being substituted by germanium in biochemical processes within the diatoms, causing a significant reduction of the diatoms' growth rate or even a complete elimination of the contaminating algae practically without affecting non-diatom algal species. For this application the typically used concentration of germanium dioxide in the culture medium is between 1 and 10 mg/l, depending on the stage of the contamination and the species.<ref name=Andersen>{{cite book| url =http://books.google.com/books?id=9NADUHyFZaEC&pg | title = Algal culturing techniques| author = Robert Arthur Andersen| publisher = Elsevier Academic Press | year = 2005}}</ref> |
Furthermore germanium dioxide is used in [[algaculture]] as an inhibitor of unwanted [[diatom]] growth in algal cultures since a contamination with the comparatively fast-growing diatoms often inhibits the growth of or outcompetes the original algae strains. GeO<sub>2</sub> is readily taken up by diatoms and leads to silicon being substituted by germanium in biochemical processes within the diatoms, causing a significant reduction of the diatoms' growth rate or even a complete elimination of the contaminating algae practically without affecting non-diatom algal species. For this application the typically used concentration of germanium dioxide in the culture medium is between 1 and 10 mg/l, depending on the stage of the contamination and the species.<ref name=Andersen>{{cite book| url =http://books.google.com/books?id=9NADUHyFZaEC&pg | title = Algal culturing techniques| author = Robert Arthur Andersen| publisher = Elsevier Academic Press | year = 2005}}</ref> |
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==Toxicity and medical== |
==Toxicity and medical== |
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Germanium dioxide has low toxicity, but in higher doses it is [[Nephrotoxicity|nephrotoxic]]. |
Germanium dioxide has low toxicity, but in higher doses it is [[Nephrotoxicity|nephrotoxic]]. |
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Germanium dioxide is used as a germanium supplement in some questionable [[dietary supplement]]s and "miracle cures".<ref>{{cite journal | author = Tao, S.H. and Bolger, P.M. | year = 1997 | month = June | title = Hazard Assessment of Germanium Supplements | journal = [[Regulatory Toxicology and Pharmacology]] | volume = 25 | issue = 3 | pages = 211–219 | doi = 10.1006/rtph.1997.1098 | pmid = 9237323 }}</ref> High doses of these resulted in several cases of germanium poisonings. |
Germanium dioxide is used as a germanium supplement in some questionable [[dietary supplement]]s and "miracle cures".<ref>{{cite journal | author = Tao, S.H. and Bolger, P.M. | year = 1997 | month = June | title = Hazard Assessment of Germanium Supplements | journal = [[Regulatory Toxicology and Pharmacology]] | volume = 25 | issue = 3 | pages = 211–219 | doi = 10.1006/rtph.1997.1098 | pmid = 9237323 }}</ref> High doses of these resulted in several cases of germanium poisonings. |
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Revision as of 13:50, 5 November 2013
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Names | |||
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IUPAC name
Germanium dioxide
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Other names
Germanium(IV) oxide
Germania ACC10380 G-15 Germanium oxide Germanic acid Germanic oxide | |||
Identifiers | |||
3D model (JSmol)
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ChemSpider | |||
ECHA InfoCard | 100.013.801 | ||
PubChem CID
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RTECS number |
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UNII | |||
CompTox Dashboard (EPA)
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Properties | |||
GeO2 | |||
Molar mass | 104.6388 g/mol | ||
Appearance | white powder or colourless crystals | ||
Density | 4.228 g/cm3 | ||
Melting point | 1,115 °C (2,039 °F; 1,388 K) | ||
4.47 g/L (25 °C) 10.7 g/L (100 °C) | |||
Solubility | insoluble in HF, HCl soluble in other acid and alkali | ||
Refractive index (nD)
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1.650 | ||
Structure | |||
hexagonal | |||
Hazards | |||
Flash point | Non-flammable | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose)
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3700 m/kg (rat, oral) | ||
Related compounds | |||
Other anions
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Germanium disulfide Germanium diselenide | ||
Other cations
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Carbon dioxide Silicon dioxide Tin 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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Germanium dioxide, also called germanium oxide and germania, is the inorganic compound with the chemical formula GeO2. It is the main commercial source of germanium. forms as a passivation layer on pure germanium in contact with atmospheric oxygen.
Structure
The two predominant polymorphs of GeO2 are hexagonal and tetragonal. Hexagonal GeO2 has the same structure as β-quartz, germanium having coordination number 4). Tetragonal GeO2 (the mineral argutite) has the rutile-like structure seen in stishovite. In this motif, germanium has the coordination number 6). An amorphous (glassy) form of GeO2 is similar to fused silica.[1]
Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO4 tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance.[2] At higher pressures, up to approximately 15 GPa, the germanium coordination number increases to 6 and the dense network structure is composed of GeO6 octahedra.[3] When the pressure is subsequently reduced, the structure reverts to the tetrahedral form.[2][3] At high pressure, the rutile form converts to an orthorhombic CaCl2 form.[4]
Reactions
Heating germanium dioxide with powdered germanium at 1000 °C forms germanium monoxide (GeO).[1]
The hexagonal (d = 4.29 g/cm3) form of germanium dioxide is more soluble than the rutile (d = 6.27 g/cm3) form and dissolves to form germanic acid, H4GeO4 or Ge(OH)4.[5] GeO2 is only slightly soluble in acid but dissolves more readily in alkali to give germanates.[5]
In contact with hydrochloric acid, it releases the volatile and corrosive germanium tetrachloride.
Uses
The refractive index (1.7) of germanium dioxide and optical dispersion properties makes 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.[6] 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.[7]
Germanium dioxide is also used as a catalyst in production of polyethylene terephthalate resin,[8] and for production of other germanium compounds. It is used as a feedstock for production of some phosphors and semiconductor materials.
Furthermore germanium dioxide is used in algaculture as an inhibitor of unwanted diatom growth in algal cultures since a contamination with the comparatively fast-growing diatoms often inhibits the growth of or outcompetes the original algae strains. GeO2 is readily taken up by diatoms and leads to silicon being substituted by germanium in biochemical processes within the diatoms, causing a significant reduction of the diatoms' growth rate or even a complete elimination of the contaminating algae practically without affecting non-diatom algal species. For this application the typically used concentration of germanium dioxide in the culture medium is between 1 and 10 mg/l, depending on the stage of the contamination and the species.[9]
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".[10] High doses of these resulted in several cases of germanium poisonings.
References
- ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ a b J W E Drewitt, P S Salmon, A C Barnes, S Klotz, H E Fischer, W A Crichton (2010). "Structure of GeO2 glass at pressures up to 8.6 GPa". Physical Review B. 81: 014202. Bibcode:2010PhRvB..81a4202D. doi:10.1103/PhysRevB.81.014202.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ a b 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 (2004). "Formation and Structure of a Dense Octahedral Glass". Physical Review Letters. 93 (11): 115502. Bibcode:2004PhRvL..93k5502G. doi:10.1103/PhysRevLett.93.115502. PMID 15447351.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ 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 0-12-352651-5
- ^ Robert D. Brown, Jr. (2000). "Germanium" (PDF). U.S. Geological Survey.
- ^ 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:10.1080/00914030108035115.
- ^ Robert Arthur Andersen (2005). Algal culturing techniques. Elsevier Academic Press.
- ^ Tao, S.H. and Bolger, P.M. (1997). "Hazard Assessment of Germanium Supplements". Regulatory Toxicology and Pharmacology. 25 (3): 211–219. doi:10.1006/rtph.1997.1098. PMID 9237323.
{{cite journal}}
: Unknown parameter|month=
ignored (help)CS1 maint: multiple names: authors list (link)