Editing Silicon dioxide (section)

===Precursor to glass and silicon===
Silica is the primary ingredient in the production of most [[glass]]. As other minerals are melted with silica, the principle of [[freezing point depression]] lowers the melting point of the mixture and increases fluidity. The [[glass transition]] temperature of pure SiO<sub>2</sub> is about 1475 K.<ref>{{cite journal|vauthors=Ojovan MI|year=2004|title=Glass formation in amorphous SiO<sub>2</sub> as a percolation phase transition in a system of network defects|journal=[[Journal of Experimental and Theoretical Physics Letters|JETP Lett.]]|volume=79|issue=12|pages=632–634|bibcode=2004JETPL..79..632O|doi=10.1134/1.1790021|s2cid=124299526}}</ref> When molten silicon dioxide SiO<sub>2</sub> is rapidly cooled, it does not crystallize, but solidifies as a glass.<ref>{{Cite book |last=Stachurski |first=Zbigniew H. |url=https://books.google.com/books?id=DBF1BgAAQBAJ&dq=silicon+dioxide+SiO2+is+rapidly+cooled+but+solidifies+as+a+glass&pg=PA176 |title=Fundamentals of Amorphous Solids: Structure and Properties |date=2015 |publisher=John Wiley & Sons |isbn=978-3-527-68219-5 |pages=176 |language=en}}</ref> Because of this, most [[ceramic glaze]]s have silica as the main ingredient.<ref>{{Cite book |url=https://books.google.com/books?id=qxRhA3MZg6AC&dq=ceramic+glazes+have+silica+as+the+main+ingredient&pg=PA563 |title=Advanced Inorganic Chemistry: Vollume II |publisher=Krishna Prakashan Media |pages=563 |language=en}}</ref>

The structural geometry of silicon and oxygen in glass is similar to that in quartz and most other crystalline forms of silicon and oxygen, with silicon surrounded by regular tetrahedra of oxygen centres. The difference between the glass and crystalline forms arises from the connectivity of the tetrahedral units: Although there is no long-range periodicity in the glassy network, ordering remains at length scales well beyond the SiO bond length. One example of this ordering is the preference to form rings of 6-tetrahedra.<ref>{{cite journal|vauthors=Elliott SR|year=1991|title=Medium-range structural order in covalent amorphous solids|journal=[[Nature (journal)|Nature]]|volume=354|issue=6353|pages=445–452|bibcode=1991Natur.354..445E|doi=10.1038/354445a0|s2cid=4344891}}</ref>

The majority of [[optical fiber]]s for [[telecommunications]] are also made from silica. It is a primary raw material for many ceramics such as [[earthenware]], [[stoneware]], and [[porcelain]].

Silicon dioxide is used to produce elemental [[silicon]]. The process involves [[carbothermic reduction]] in an [[electric arc furnace]]:<ref>{{Cite book|title=Shriver & Atkins' inorganic chemistry|publisher=Oxford University Press|year=2010|isbn=9780199236176|veditors=Atkins PW, Overton T, Rourke J, Weller M, Armstrong F|edition=5th|location=Oxford|pages=354|oclc=430678988|display-editors=3}}</ref>
:<chem>SiO2 + 2 C -> Si + 2 CO</chem>