 ZnS powders containing different concentrations of sulfur vacancies[1] | |
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| Other names | |
| Identifiers | |
3D model (JSmol) | |
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| ECHA InfoCard | 100.013.866 |
| RTECS number |
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| Properties | |
| ZnS | |
| Molar mass | 97.474 g/mol |
| Density | 4.090 g/cm3 |
| Melting point | 1,850 °C (3,360 °F; 2,120 K) (sublime) |
| negligible | |
| Band gap | 3.54 eV (cubic, 300 K) 3.91 eV (hexagonal, 300 K) |
Refractive index (nD) | 2.3677 |
| Structure | |
| see text | |
| Tetrahedral (Zn2+) Tetrahedral (S2−) | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | −204.6 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Safety data sheet (SDS) | ICSC 1627 |
| Related compounds | |
Otheranions | Zinc oxide Zinc selenide Zinc telluride |
Othercations | Cadmium sulfide Mercury sulfide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Zinc sulfide (orzinc sulphide) is aninorganic compound with thechemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineralsphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment. In its dense synthetic form, zinc sulfide can betransparent, and it is used as a window forvisible optics andinfrared optics.
ZnS exists in two maincrystalline forms. This dualism is an example ofpolymorphism. In each form, the coordination geometry at Zn and S is tetrahedral. The more stable cubic form is known also as zinc blende orsphalerite. The hexagonal form is known as the mineralwurtzite, although it also can be produced synthetically.[2] The transition from the sphalerite form to the wurtzite form occurs at around 1020 °C.
Zinc sulfide, with addition of a fewppm of a suitableactivator, exhibits strongphosphorescence. The phenomenon was described byNikola Tesla in 1893,[3] and is currently used in many applications, fromcathode-ray tubes throughX-ray screens toglow in the dark products. Whensilver is used as activator, the resulting color is bright blue, with maximum at 450nanometers. Usingmanganese yields an orange-red color at around 590 nanometers.Copper gives a longer glow, and it has the familiar greenish glow-in-the-dark. Copper-doped zinc sulfide ("ZnS plus Cu") is used also inelectroluminescent panels.[4] It also exhibitsphosphorescence due to impurities on illumination with blue orultraviolet light.
Zinc sulfide is also used as aninfrared optical material, transmitting from visiblewavelengths to just over 12micrometers. It can be used planar as anoptical window or shaped into alens. It is made asmicrocrystalline sheets by the synthesis fromhydrogen sulfide gas and zinc vapour, and this is sold asFLIR-grade (Forward Looking Infrared), where the zinc sulfide is in a milky-yellow, opaque form. This material whenhot isostatically pressed (HIPed) can be converted to a water-clear form known asCleartran (trademark). Early commercial forms were marketed asIrtran-2 but this designation is now obsolete.
Zinc sulfide is a commonpigment, sometimes called sachtolith. When combined with barium sulfate, zinc sulfide formslithopone.[5]
Fine ZnS powder is an efficientphotocatalyst, which produces hydrogen gas from water upon illumination. Sulfur vacancies can be introduced in ZnS during its synthesis; this gradually turns the white-yellowish ZnS into a brown powder, and boosts the photocatalytic activity through enhanced light absorption.[1]
Both sphalerite and wurtzite are intrinsic, wide-bandgapsemiconductors. These are prototypicalII-VI semiconductors, and they adopt structures related to many of the other semiconductors, such asgallium arsenide. The cubic form of ZnS has aband gap of about 3.54electron volts at 300kelvins, but the hexagonal form has a band gap of about 3.91 electron volts. ZnS can bedoped as either ann-type semiconductor or ap-type semiconductor.
Thephosphorescence of ZnS was first reported by the French chemistThéodore Sidot in 1866. His findings were presented byA. E. Becquerel, who was renowned for the research onluminescence.[6] ZnS was used byErnest Rutherford and others in the early years ofnuclear physics as ascintillation detector, because it emits light upon excitation byx-rays orelectron beam, making it useful for X-ray screens and cathode-ray tubes.[7] This property made zinc sulfide useful in thedials of radium watches.
Zinc sulfide is usually produced from waste materials from other applications. Typical sources include smelter, slag, and pickle liquors.[5] As an example, the synthesis ofammonia frommethane requiresa priori removal ofhydrogen sulfide impurities in the natural gas, for whichzinc oxide is used. This scavenging produces zinc sulfide:
Crude zinc sulfide can be produced by igniting a mixture ofzinc andsulfur.[8] More conventionally, ZnS is prepared by treating a mildly acidic solution of Zn2+ salts withH2S:[9]
This reaction is the basis of agravimetric analysis for zinc.[10]
