Zinc sulfide (or zinc sulphide) is a
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
ZnZinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
SSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as zinc blende or
sphaleriteSphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
. The hexagonal form is also known both as a synthetic material and as the mineral
wurtziteWurtzite is a zinc iron sulfide mineral a less frequently encountered mineral form of sphalerite.Its crystal structure is called the wurtzite crystal structure, to which it lends its name...
. A tetragonal form is also known as very rare mineral polhemusite (Zn,Hg)S. Both sphalerite and wurtzite are intrinsic, wide-bandgap
semiconductorA semiconductor is a material that has an electrical resistivity between that of a conductor and an insulator, that is, generally in the range 10
3 Siemens/cm to 10
−8 S/cm. Devices made from semiconductor materials are the foundation of modern electronics, including radio,...
s. The cubic form has a
band gapIn solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states exist...
of 3.54 eV at 300
KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
whereas the hexagonal form has a band gap of 3.91 eV. The transition from the sphalerite form to the wurtzite form occurs at around 1020 ºC.
Applications
The first time the phosphorescence of ZnS was observed by the French chemist Théodore Sidot in 1866. His findings were presented by the reknown chemist
A. E. BecquerelAlexandre-Edmond Becquerel was a French physicist who studied the solar spectrum, magnetism, electricity, and optics. He is known for his work in luminescence and phosphorescence. He discovered the photovoltaic effect, which is the physics behind the solar cell, in 1839...
who was involved in the research on luminescence and phosphorescence.
ZnS was used by
Ernest RutherfordErnest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS was a New Zealand chemist and physicist who became known as the father of nuclear physics....
and others in the early years of
nuclear physicsNuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.The most commonly known applications of nuclear physics are nuclear power and nuclear weapons, but the research has provided wider applications, including those in medicine , materials...
as a
scintillationA scintillator is material which exhibits the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate, i.e. reemit the absorbed energy in the form of a small flash of light, typically in the visible...
detector, because it emits light on excitation by x-rays or electron beam, making it useful for x-ray screens and
cathode ray tubeThe cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen...
s. It also exhibits
phosphorescencePhosphorescence is a specific type of photoluminescence related to fluorescence. Unlike fluorescence, a phosphorescent material does not immediately re-emit the radiation it absorbs. The slower time scales of the re-emission are associated with "forbidden" energy state transitions in quantum...
due to impurities on illumination with blue or
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light.
Zinc sulfide, with addition of few ppm of suitable activator, is used as
phosphorA phosphor is a substance that exhibits the phenomenon of phosphorescence ....
in many applications, from
cathode ray tubeThe cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen...
s through
x-rayX-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays...
screens to glow in the dark products. When
silverSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
is used as activator, the resulting color is bright blue, with maximum at 450
nmA nanometre is a unit of length in the metric system, equal to one billionth of a meter....
.
ManganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
yields an orange-red color at around 590 nm.
CopperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
provides long glow time and the familiar glow-in-the-dark greenish color. Copper doped zinc sulfide (ZnS+Cu) is used also in
electroluminescentElectroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to an electric current passed through it, or to a strong electric field...
panels.
Zinc sulfide is also used as an
infraredInfrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves...
optical material, transmitting from visible
wavelengthIn physics, the wavelength of a sinusoidal wave is the spatial period of the wave – the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s to over 12
micrometreA micrometre or micron is one millionth of a metre,or equivalently one thousandth of a millimetre....
s. It can be used planar as an
optical windowThe meaning of this term depends on the context:* In astronomy, the optical window is the optical portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground...
or shaped into a
lensA lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens is a lens consisting of a single optical element...
. It is made as microcrystalline sheets by the synthesis from H
2S 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 pressedHot isostatic pressing is a manufacturing process used to reduce the porosity of metals and influence the density of many ceramic materials. This improves the mechanical properties, workability and ceramic density....
(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 semiconductorAn N-type semiconductor is a material obtained by carrying out a process of doping, that is, by adding some amount of an element with more electrons to a semiconductor element with fewer electrons, in order to increase the number of free charge carriers. In this case the charge carriers are...
and
p-type semiconductorA P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free charge carriers ....
, which is unusual for the II-VI semiconductors. ZnS is a
covalently bondedA covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds...
solid.
Production in lab
It is easily produced by mixing an amount of zinc and sulfur and then igniting it. The result (after cooling) is zinc sulfide.
Zinc sulfide is insoluble in water and solutions containing Zn
2+ readily precipitate ZnS in the presence of sulfide ions (e.g., from
H2SHydrogen sulfide is the chemical compound with the formula H
2S. This colorless, toxic and flammable gas is partially responsible for the foul odor of rotten eggs and flatulence....
).
- Zn2+ + S2− → ZnS
This has formed the basis of a gravimetric analysis for zinc.
External links