Zinc sulfide is an inorganic compound
with the chemical formula of ZnS. This
is the main form of zinc found in
nature, where it mainly occurs as the
mineral sphalerite. 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 be transparent, and it
is used as a window for visible optics
and infrared optics.
Structure 
ZnS exists in two main crystalline
forms, and this dualism is often a
salient example of polymorphism. In each
form, the coordination geometry at Zn
and S is tetrahedral. The more stable
cubic form is known also as zinc blende
or sphalerite. The hexagonal form is
known as the mineral wurtzite, although
it also can be produced synthetically.
The transition from the sphalerite form
to the wurtzite form occurs at around
1020 celsius. A tetragonal form is also
known as the very rare mineral called
polhemusite, with the formulaS.
Applications 
= Luminescent material =
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 nanometers. Using
manganese yields an orange-red color at
around 590 nanometers. Copper gives
long-time glow, and it has the familiar
greenish glow-in-the-dark. Copper-doped
zinc sulfide is used also in
electroluminescent panels. It also
exhibits phosphorescence due to
impurities on illumination with blue or
ultraviolet light.
= Optical material =
Zinc sulfide is also used as an infrared
optical material, transmitting from
visible wavelengths to just over 12
micrometers. It can be used planar as an
optical window or shaped into a lens. It
is made as microcrystalline sheets by
the synthesis from hydrogen sulfide gas
and zinc vapour, and this is sold as
FLIR-grade, where the zinc sulfide is in
a milky-yellow, opaque form. This
material when hot isostatically pressed
can be converted to a water-clear form
known as Cleartran. Early commercial
forms were marketed as Irtran-2 but this
designation is now obsolete.
= Pigment =
Zinc sulfide is a common pigment,
sometimes called sachtolith. When
combined with barium sulfate, zinc
sulfide forms lithopone.
= Semiconductor properties =
Both sphalerite and wurtzite are
intrinsic, wide-bandgap semiconductors.
These are prototypical II-VI
semiconductors, and they adopt
structures related to many of the other
semiconductors, such as gallium
arsenide. The cubic form of ZnS has a
band gap of about 3.54 electron volts at
300 kelvin, but the hexagonal form has a
band gap of about 3.91 electron volts.
ZnS can be doped as either an n-type
semiconductor or a p-type semiconductor.
History 
The phosphorescence of ZnS was first
reported by the French chemist Théodore
Sidot in 1866. His findings were
presented by A. E. Becquerel, who was
renowned for the research on
luminescence. ZnS was used by Ernest
Rutherford and others in the early years
of nuclear physics as a scintillation
detector, because it emits light upon
excitation by x-rays or electron beam,
making it useful for X-ray screens and
cathode ray tubes.
Production 
Zinc sulfide is usually produced from
waste materials from other applications.
Typical sources include smelter, slag,
and pickle liquors. It is also a
by-product of the synthesis of ammonia
from methane where zinc oxide is used to
scavenge hydrogen sulfide impurities in
the natural gas:
ZnO + H2S → ZnS + H2O
= Laboratory preparation =
It is easily produced by igniting a
mixture of zinc and sulfur. Since zinc
sulfide is insoluble in water, it can
also be produced in a precipitation
reaction. Solutions containing Zn2+
salts readily form a precipitate ZnS in
the presence of sulfide ions.
Zn2+ + S2− → ZnS
This reaction is the basis of a
gravimetric analysis for zinc.
References 
External links 
Zinc and Sulfur at The Periodic Table of
Videos
Composition of CRT phosphors
University of Reading, Infrared
Multilayer Laboratory optical data
