Germanium dioxide
Germanium dioxide, also called
germanium oxide and
germania, is an
inorganic compound, an
oxide of
germanium. Its chemical formula is
GeO2. Its
CAS number is . Its other names are
germanic acid,
G-15, and
ACC10380. It has the appearance of white powder or colorless crystals, with melting point of 1115 °C. Germanium dioxide is a structural analog of
silicon dioxide. It can be prepared both
crystalline and
amorphous. It forms a
passivation layer on pure germanium in contact with atmospheric oxygen.
Germanium dioxide's
refractive index 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.
Mixture of silicon dioxide and germanium dioxide ("silica-germania") is used as an optical material for
optical fibers and
optical waveguides. 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. [
1]
Germanium dioxide is also used as a
catalyst in production of
polyethylene terephthalate resin, and for production of other germanium compounds. It is used as a feedstock for production of some
phosphors and
semiconductor materials.
Germanium dioxide has low toxicity; in higher doses it is
nephrotoxic. It is not flammable. In contact with
hydrochloric acid it releases volatile and corrosive
germanium tetrachloride. It is moderately soluble in water, with which it reacts and forms
germanic acid.
Germanium dioxide is used as a germanium supplement in some questionable
dietary supplements and "miracle cures". High doses of these resulted in several cases of germanium poisonings.
At very high pressures, germanium dioxide forms unusual octahedral structure. [
2][
3]
In 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.
