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.

Properties of Germanium Dioxide

Molecular formula : GeO₂

Appearance : white powder or colourless crystals

Molar mass : 104.61 g/mol

Density : 3.64 g/cm³

Melting point : 1115 °C

Boiling point : 1200 °C

Solubility in water : 5.2 g/l (25 °C) ; 10.7 g/l (100 °C)

Applications of Germanium Dioxide

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.

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.