Zinc sulfide

Crystal structure
Crystal structures of zinc sulfide, ZnS left : sphalerite (cubic); right : Wurtzit (hexagonal) __ Zn 2+      __ S 2−
General
Surname	Zinc sulfide
other names	Zinc (II) sulfide Sphalerite ( zinc blende ) Wurtzit CI Pigment White 7
Ratio formula	ZnS
Brief description	white, odorless powder
External identifiers / databases
CAS number 1314-98-3 EC number 215-251-3 ECHA InfoCard 100,013,866 PubChem 14821 Wikidata Q204952
properties
Molar mass	97.46 g · mol -1
Physical state	firmly
density	4.087 g cm −3 (α shape) 4.102 g cm −3 (β-form)
solubility	practically insoluble in water soluble in dilute mineral acids
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Zinc sulfide (specifically, zinc (II) sulfide; Molecular Formula ZnS) is the zinc - salt of hydrogen sulphide . It occurs naturally in mineral form as cubic sphalerite ( zinc blende ) and hexagonal wurtzite and can be mined. In both sphalerite and wurtzite the zinc ions are tetrahedrally surrounded by four sulfide ions and vice versa. Both crystal structures are prototypes for a whole range of compounds. Wurtzite is the high-temperature modification . Zinc sulfide is a II-VI compound semiconductor ( E _G = 3.54 eV, at room temperature).

Manufacturing

Zinc sulfide can be made by oxidizing zinc with sulfur:

${\displaystyle \mathrm {8\ Zn+S_{8}\longrightarrow 8\ ZnS} }$

The reaction of aqueous solutions of zinc salts with ammonium sulfide solution also forms as a white to pale yellow amorphous precipitate.

It is also possible to produce it by reacting a zinc sulfate solution with hydrogen sulfide with the addition of ammonium acetate

${\displaystyle \mathrm {ZnSO_{4}+H_{2}S\longrightarrow ZnS+H_{2}SO_{4}} }$

or the reaction of zinc oxide and sulfur in an ammoniacal medium.

${\displaystyle \mathrm {3\ ZnO+4\ S+2\ NH_{3}+H_{2}O\longrightarrow 3\ ZnS+(NH_{4})_{2}SO_{4}} }$

properties

Pure zinc sulfide is a white powder that can appear in two polymorphic crystal forms. The α-shape forms a cubic lattice and occurs naturally as sphalerite ( zinc blende , α-ZnS). The conversion into the naturally occurring β-modification wurtzite (β-ZnS) begins at 1185 ° C and is completed at 1200 ° C. Wurtzite crystallizes in a hexagonal crystal lattice. It shows no melting point at normal pressure and sublimates at 1185 ° C. At a high pressure of 15 MPa, the melting point is 1850 ° C.

From 480 ° C, in the presence of air, oxidation to zinc oxide and sulfur dioxide takes place .

${\displaystyle \mathrm {2\ ZnS+3\ O_{2}\longrightarrow 2\ ZnO+2\ SO_{2}} }$

use

With Al ³⁺ - and Cu ⁺ - ion -doped zinc sulfide shows luminescence and is used for light screens in picture tubes , Magic eyes and luminescent dials of watches used. It is also used in electroluminescent films . Doping with manganese causes orange-red luminescence under UV light (366 nm). Alternatively, doping with silver ions is possible.

In painting, it is used together with barium sulfate as a white pigment; a form that is precipitated together is known as a lithopone . A disadvantage for use as a pigment is the limited resistance of ZnS, especially in outdoor applications. Oxygen slowly oxidizes ZnS to soluble zinc sulfate .

Because of its high refractive index of 2.37, thin ZnS films vapor-deposited in a vacuum are used for coating optical components.

Zinc sulfide is transparent over a wide range of the technically used infrared spectrum and is therefore increasingly used for infrared optics (IR cameras) and protective glasses. It is cheaper than the alternatives germanium and zinc selenide and also less critical from a toxicological point of view. Due to the high refractive index, when passing through an uncoated ZnS window, around 30% of the IR intensity is lost due to reflection at the interfaces. That is why such windows and optics are usually given an elaborate anti-reflective coating.

Individual evidence

1. ↑ ^{a b c} Entry on zinc sulfide in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
2. ↑ ^{a b} Entry on zinc sulfide. In: Römpp Online . Georg Thieme Verlag, accessed on January 30, 2015.
3. ↑ ^{a b} Georg Brauer (Ed.), With the collaboration of Marianne Baudler u a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1027.
4. ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 142 .
5. ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 177 .
6. ↑ A. Otto Gübli-Litscher: About the energy of formation of some heavy metal sulfides with an addition about potassium cyanomanganate-1. Diss.-Druckerei A.-O. Oebr. Leemann & Co., Zurich 1941, p. 71 ( PDF 3.97 MB )
7. ↑ Prabhu, GM; Ulrichson, DL; Pulsifer, AH: Kinetics of the Oxidation of Zinc Sulfide in Ind. Eng. Chem. Fundam. 23 (1984) 271-273, doi : 10.1021 / i100015a001 .