Zinc sulfide

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Zinc sulfide
Sphalerite, the more common polymorph of zinc sulfide
Wurtzite, the less common polymorph of zinc sulfide
Other names Zinc sulphide
Identifiers
CAS number [[1314-98-3][1]]
Properties
Molecular formula ZnS
Molar mass 97.475 g mol−1
Density 4.090 g cm−3
Melting point

varies:1973 K[1],2103 K[2],sublimes before melting[3]
Boiling point

2100 K[4],sublimes before melting[3]
Solubility in other solvents insoluble
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Zinc sulfide (or zinc sulphide) is a chemical compound with the formula ZnS. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as the mineral sphalerite. The hexagonal form is also known both as a synthetic material and as the mineral wurtzite. Both sphalerite and wurtzite are intrinsic, wide-bandgap semiconductors. The cubic form has a band gap of 3.54 eV at 300 K whereas the hexagonal form has a band gap of 3.91 eV.

A transition from the sphalerite form to the wurtzite form occurs at around 1293.15 K. Sphalerite melts at 1991 K. It has a standard enthalpy of formation of −204.6 kJ mol−1 at 298 K.

Contents

[edit] Applications

ZnS was used by Ernest Rutherford and others in the early years of nuclear physics as a scintillation detector, because it emits light on excitation by x-rays or electron beam, making it useful for x-ray screens and cathode ray tubes. It also exhibits phosphorescence due to impurities on illumination with blue or ultraviolet light.

Zinc sulfide, with addition of few ppm of suitable activator, is used as phosphor in many applications, from cathode ray tubes through x-ray screens to glow in the dark products. When silver is used as activator, the resulting color is bright blue, with maximum at 450 nm. Manganese yields an orange-red color at around 590 nm. Copper provides long glow time and the familiar glow-in-the-dark greenish color. Copper doped zinc sulfide (ZnS+Cu) is used also in electroluminescent panels.

Zinc sulfide is also used as an infrared optical material, transmitting from visible wavelengths to over 12 micrometres. It can be used planar as an optical window or shaped into a lens. It is made as microcrystalline sheets by the synthesis from H2S gas and zinc vapour and sold as FLIR (Forward Looking IR) grade ZnS a pale milky yellow visibly opaque form. This material when hot isostatically pressed (HIPed) can be converted to a water-clear form known as Cleartran (trademark). Early commercial forms were marketed as Irtran-2 but this designation is now obsolete.

It can be doped as both n-type semiconductor and p-type semiconductor, which is unusual for the II-VI semiconductors. ZnS is a covalently bonded solid.

[edit] Production in lab

It is easily produced by mixing an amount of zinc and sulfur and then igniting it and as it extingushes zinc sulfide is obtained. This can be a very dangerous process.

[edit] See also

[edit] References

  1. ^ a b Zinc Sulfide HSB Search results 'Melting Point: 1700 deg C' ... 'CLASSIFICATION: D; not classifiable as to human carcinogenicity' ... 'Zinc sulfide, as well as barium sulfate which was similarly encountered /from liquid center of golf ball accidentally squirted into eye of 2 children/, produced only slight macrophage reaction and negligible tissue damage'
  2. ^ ZINC SULPHIDE KORTH KRISTALLE GMBH '1830°C (sublimation)'
  3. ^ a b [www.springerlink.com/index/d5btmradh2rabvd7.pdf] 'Under normal pressure ZnS sublimes before melting'
  4. ^ Boiling Point diracdelta.co.uk science and engineering encyclopedia

[edit] External links

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