Potassium Fluorosilicate
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Potassium fluorosilicate is a chemical compound with the chemical formula . When doped with potassium hexafluoromanganate(IV) (, with ) it forms a narrow band red producing
phosphor A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or ...
, (often abbreviated PSF or KSF), of economic interest due to its applicability in LED lighting and
displays A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal ...
.


Natural occurrence

Occurs naturally as hiereatite, found in the
Aeolian islands The Aeolian Islands ( ; ; ), sometimes referred to as the Lipari Islands or Lipari group ( , ) after their largest island, are a volcanic archipelago in the Tyrrhenian Sea north of Sicily, said to be named after Aeolus, the mythical ruler of ...
(
Sicily Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
, Italy). A
hexagonal In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°. Regular hexagon A regular hexagon is d ...
form demartinite has also been found at the rim of
volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...
fumarole A fumarole (or fumerole) is a vent in the surface of the Earth or another rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...
s in the same islands. The sea sponge Halichondria Moorei builds a skeleton of potassium fluorosilicate.


Structure and properties

According to analysis by Loehlin (1984), it has
space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
Fmm, with a0 = 0.8134 nm, V = 0.538.2 nm3 at 295 K. The Si-F
bond length In molecular geometry, bond length or bond distance is defined as the average distance between Atomic nucleus, nuclei of two chemical bond, bonded atoms in a molecule. It is a Transferability (chemistry), transferable property of a bond between at ...
is 0.1683 nm. At high temperatures and pressures -beta and -gamma phases exist.


Applications

Potassium fluorosilicate has applications in
porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...
manufacture, the preservation of
timber Lumber is wood that has been processed into uniform and useful sizes (dimensional lumber), including beams and planks or boards. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). ...
, aluminium and magnesium
smelting Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron-making, iron, copper extraction, copper ...
, and the manufacture of
optical glass Optical glass refers to a quality of glass suitable for the manufacture of optical systems such as optical lenses, Prism (geometry), prisms or mirrors. Unlike window glass or crystal, whose formula is adapted to the desired aesthetic effect, optic ...
.


Red phosphor

When doped with potassium hexafluoromanganate(IV) ), a narrow band red phosphor is produced, emitting at around 630 nm. This substance has application improving the white light quality of white LEDs that use a blue emitting
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
in combination with the yellow
cerium Cerium is a chemical element; it has Chemical symbol, symbol Ce and atomic number 58. It is a hardness, soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it ...
doped
yttrium aluminium garnet Yttrium aluminium garnet (YAG, Yttrium, Y3Aluminium, Al5Oxygen, O12) is a synthetic crystalline material of the garnet group. It is a Crystal system, cubic yttrium aluminium oxide phase, with other examples being YAlO3 (YAP) in a Crystal system, ...
phosphor (YAG), . Synthesis routes to the phosphor include co- crystallisation and co-
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...
. For example, in (40 %)
hydrofluoric acid Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive. A common concentration is 49% (48–52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling p ...
with
potassium fluoride Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide salt and occurs naturally as the ...
can be mixed with dissolved in (40 %) hydrofluoric acid to co-precipitate the phosphor. The acronyms KSF or PSF are used for potassium fluorosilicate phosphors.


See also

* Fluorosilicic acid * Ammonium fluorosilicate * Sodium fluorosilicate


References

{{Silicon compounds Potassium compounds Hexafluorosilicates Phosphors and scintillators