Potassium fluorosilicate

Potassium fluorosilicate

Names
Preferred IUPAC name Potassium fluorosilicate
Other names Potassium hexafluorosilicate(IV)
Identifiers
CAS Number	16871-90-2
3D model (JSmol)	Interactive image
ChemSpider	55723
ECHA InfoCard	100.037.163
EC Number	240-896-2 [1]
PubChem CID	61851
RTECS number	VV8400000
UNII	2610W49XYD
UN number	2655
CompTox Dashboard (EPA)	DTXSID10884939
InChI InChI=1S/F6Si.2K/c1-7(2,3,4,5)6;;/q-2;2*+1 Key: UUHPPUWEDCVPCO-UHFFFAOYSA-N
SMILES F[Si-2](F)(F)(F)(F)F.[K+].[K+]
Properties
Chemical formula	K2[SiF6]
Molar mass	220.28 gmol−1 [1]
Density	2.27gcm−3,[1] 2.719gcm−3 [2]
Solubility in water	Slightly soluble in water
Structure
Crystal structure	cubic
Space group	Fm3m
Lattice constant	a = 0.8134 nm
Lattice volume (V)	0.538.2 nm3
Formula units (Z)	4
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H311, H331
Precautionary statements	P261, P264, P270, P271, P280, P301+P310, P302+P352, P304+P340, P311, P312, P321, P322, P330, P361, P363, P403+P233, P405, P501
Related compounds
Other cations	Ammonium hexafluorosilicate Sodium fluorosilicate Fluorosilicic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Potassium fluorosilicate is a chemical compound with the chemical formula K₂[SiF₆].

When doped with Potassium hexafluoromanganate(IV) ((K₂[MnF₆]) it forms a narrow band red producing phosphor, (often abbreviated PSF or KSF), of economic interest due to its applicability in LED lighting and displays.

Natural occurrence

Occurs naturally as Hiereatite, found in the Aeolian islands (Sicily/Italy).^[3] A hexagonal form Demartinite has also been found at the rim of volcanic fumaroles in the same islands.^[4]

Structure and properties

According to analysis by (Loehlin, 1984) it has space group Fm3m, with a₀ = 0.8134 nm, V = 0.538.2 nm³ at 295K. The Si-F bond length is 0.1683 nm.^[2] At high temperatures and pressures -beta and -gamma phases exist.^[5]

Application

Potassium fluorosilicate has applications in porcelain manufacture, the preservation of timber, aluminium and magnesium smelting, and the manufacture of optical glass.^[1]

Red phosphor

When doped with potassium hexafluoromanganate(IV) (K₂[MnF₆]), 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 in combination with the yellow cerium doped yttrium aluminium garnet phosphor (YAG), Y₃Al₅O₁₂:Ce³⁺.^[6]

Synthesis routes to the phosphor include co-crystallisation and co-precipitation. For example, K₂[MnF₆] in (40%) hydrofluoric acid with potassium fluoride can be mixed with SiO₂ dissolved in (40%) hydrofluoric acid to co-precipitate the phosphor.^[5]

The acronyms KSF or PSF are used for potassium fluorosilicate phosphors.^[7]

See also

• Fluorosilicic acid
• Ammonium fluorosilicate
• Sodium fluorosilicate

References