GeO2

GeO2, or germanium dioxide, is the binary oxide of germanium. It occurs as a white, odorless powder in its anhydrous form and is mainly produced synthetically for industrial use. The compound is a network-forming oxide that, like silicon dioxide, forms extended GeO4 tetrahedra linked into three-dimensional structures.

GeO2 exhibits several crystalline polymorphs. The most common at room temperature is a quartz-like α-GeO2 structure, and other high-temperature or high-pressure forms have been studied, including structures related to cristobalite and rutile-type arrangements. In addition to its crystalline forms, GeO2 readily forms an amorphous glass known as germania, which is a transparent, colorless solid with interesting optical properties.

Chemically, GeO2 is sparingly soluble in water and shows amphoteric behavior, dissolving in strong bases to yield germanate species and reacting with acids to form soluble germanium aquo complexes under appropriate conditions. The compound melts around 1110–1115 °C and has a relatively high density for a simple oxide. In practice, GeO2 is often encountered as a glassy material or as a dopant in other glasses.

Industrially, GeO2 is prepared by oxidation of germanium-containing materials or by hydrolysis of GeCl4 and related precursors, followed by drying and heating to yield the oxide. It serves as a key precursor for germanium-containing glasses and ceramics. In optics and photonics, germania is widely used as a dopant in silica glass to increase refractive index and to tailor optical properties, enabling applications such as optical fibers and waveguides.

Safety considerations include the irritation potential of GeO2 dust; handling should avoid inhalation and ingestion, with standard laboratory and industrial dust-control practices in place.