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.

Germanium dioxide is a structural analog of silicon dioxide. Hexagonal GeO2 has structure as β-quartz with coordination number of germanium 4, tetragonal GeO2 has rutile structure of stishovite with coordination number of germanium 6 and amorphous GeO2 is similar to fused silica. It can be prepared both crystalline and amorphous. At very high pressures, germanium dioxide forms unusual octahedral structure. 

Application

1.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.

2.Germanium Oxide, Germanium Dioxide or Germania is a highly insoluble thermally stable Germanium source suitable for glass, optic and ceramic applications. 

3.Germanium Oxide can be prepared in both crystalline and amorphous forms. Oxide compounds are not conductive to electricity. Metal oxide compounds are basic anhydrides and can therefore react with acids and with strong reducing agents in redox reactions.