Germanium Dioxide - Uses

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. 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. 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.

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.