Raw materials

At first glance, quartz glass appears very simple, both chemically and structurally, since it is made from a single oxide component (silicon dioxide – SiO₂).

Silica, as it is also known, is found throughout the earth’s crust. However, only a small fraction has sufficient purity
(> 99.98 %) to be suitable as raw material for quartz glass. Sand at the beach is also SiO₂, but isn’t suitable for the use in the semiconductor industry.

Note that the structure is completely connected: meaning that all atoms are bonded to at least two others.

In the quartz glass structure all atoms are bonded t at least two others. Together with the strength of the siliconoxygen (Si-O) chemical bond gives quartz glass high temperature stability and chemical resistance. But the structure is also rather open with wide spaces (interstices) between the structural units. This accounts for higher gas permeability and much lower thermal expansion coefficient of quartz glass relative to other materials.