Germanium dioxide
IUPAC name	Germanium dioxide
Other names	Germanium(IV) oxide Germania ACC10380 G-15
Identifiers
CAS number	1310-53-8 Y
PubChem	14796
RTECS number	LY5240000
InChI	1/GeO2/c2-1-3
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
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.

Contents 1 Structure 2 Reactions 3 Uses 4 Toxicity and medical 5 References

[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

v • d • e   Germanium compounds GeCl2 · GeCl4 · GeI2 · GeO · GeO2 · GeS · GeS2 · GeTe