Chalcogenides

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Pyrite cubes in the bedrock, pyrite as an iron sulfide is a typical chalcogenide and is of importance e.g. B. for chemical evolution
The mineral cinnabar ( cinnabarite ), chemically: mercury sulfide, belongs to the chalcogenides and is used as a pigment

Chalcogenides are chemical compounds consisting of one or more chalcogen elements ( oxygen , sulfur , selenium and tellurium ) as formal anions with metals or more electropositive elements ( arsenic , germanium , phosphorus , antimony , lead , boron , aluminum , gallium , indium , titanium , Sodium ) as formal cations .

Subdivision

Chalcogenides are therefore divided into oxides , sulfides , selenides and tellurides and, depending on the binding partner, form gaseous (such as carbon dioxide ) or mostly solid substances. As solids , they can form compounds with an ionic or covalent character, depending on the difference in electronegativity . The solids are mostly crystalline , but they can also be produced as amorphous glass-like materials. Formally, they can be understood as the salts of the respective chalcogenic acid ( water , hydrosulfuric acid, hydroselenic acid and hydrofluoric acid).

meaning

Rather ionic chalcogenides such as B. iron sulfides or cadmium sulfide occur as sulfidic ores and minerals and are z. B. used as pigments: HgS ( cinnabar ), CdS (cadmium yellow), CdSe (cadmium red), zinc sulfide (white pigment).

The more glassy chalcogenides than

  • Optical glasses for the infrared range: The glasses are transparent in the spectral range of 1–14 micrometers light wavelength. ( Ge 33 As 12 Se 55 , Ge 30 As 13 Se 32 Te 25 , Ge 10 As 40 Se 50 , Ge 28 Sb 12 Se 60 , As 40 Se 60 )
  • Coating of rewritable optical storage media: In the form of alloys of chalcogenides, it is the active material in CD-RWs and DVD-RAMs . This makes use of the fact that the optical properties of the two phases (amorphous, crystalline) differ and that they are stable with temperature (Laser) lets the material switch back and forth between the two phases (see also phase change technique ).
  • Resistive element in electronic memory phase-change random access memory : Also in the form of alloys of chalcogenides, it represents the active material in these new non-volatile memories . This makes use of the fact that the electrical properties ( electrical resistance ) of the two phases (amorphous, crystalline) and that the material can be switched back and forth between the two phases in a stable manner via temperature (current pulse).
  • Photoresist in photolithography

Individual evidence

  1. ↑ a b Gurinder Kaur Ahluwalia: Applications of Chalcogenides: S, Se, and Te . Springer, 2016, ISBN 978-3-319-41190-3 , pp. 5 ( limited preview in Google Book search).
  2. ↑ a b Victor I. Mikla, Victor V. Mikla: Amorphous chalcogenide The Past, Present and Future . Elsevier, 2011, ISBN 978-0-12-388434-3 , pp. x ( limited preview in Google Book Search).
  3. ^ JL Adam, X. Zhang: Chalcogenide Glasses Preparation, Properties and Applications . Woodhead Publishing, 2014, ISBN 978-0-85709-356-1 ( limited preview in Google Book Search).
  4. ↑ J. David Musgraves, Juejun Hu, Laurent Calvez: Springer Handbook of Glass . Springer Nature, 2019, ISBN 978-3-319-93728-1 , pp. 532 ( limited preview in Google Book search).