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| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.029.189 |
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| Properties | |
| BaF2 | |
| Molar mass | 175.324 g/mol[1] |
| Appearance | white cubic crystals[1] |
| Density | 4.893 g/cm3[1] |
| Melting point | 1,368 °C (2,494 °F; 1,641 K)[1] |
| Boiling point | 2,260 °C (4,100 °F; 2,530 K)[1] |
| 1.58 g/L (10 °C) 1.61 g/L (25 °C)[2] | |
Solubility product (Ksp) | 1.84·10−7[3] |
| Solubility | soluble inmethanol,ethanol |
| −51·10−6 cm3/mol[4] | |
| Thermal conductivity | 10.9 W/(m·K)[5] |
Refractive index (nD) |
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| Structure[7] | |
| Fluorite (cubic),cF12 | |
| Fm3m, No. 225 | |
a = 0.62 nm | |
Formula units (Z) | 4 |
| Thermochemistry[8] | |
| 71.2 J/(mol·K) | |
Std molar entropy(S⦵298) | 96.4 J/(mol·K) |
Std enthalpy of formation(ΔfH⦵298) | −1207.1 kJ/mol |
Gibbs free energy(ΔfG⦵) | −1156.8 kJ/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Toxic |
| GHS labelling: | |
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| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 250 mg/kg, oral (rat) |
| Safety data sheet (SDS) | PubChem |
| Related compounds | |
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Othercations | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Barium fluoride is aninorganic compound with the formulaBaF2. It is a colorless solid that occurs in nature as the rare mineralfrankdicksonite.[9] Under standard conditions it adopts thefluorite structure and at high pressure thePbCl2 structure.[10] LikeCaF2, it is resilient to and insoluble in water.
Above ca. 500 °C,BaF2 is corroded by moisture, but in dry environments it can be used up to 800 °C. Prolonged exposure to moisture degrades transmission in thevacuum UV range. It is less resistant to water thancalcium fluoride, but it is the most resistant of all the optical fluorides to high-energy radiation, though its far ultraviolet transmittance is lower than that of the other fluorides. It is quite hard, very sensitive tothermal shock and fractures quite easily.
Barium fluoride is transparent from theultraviolet to theinfrared, from 150 to 200nm to 11–11.5 μm. It is used in windows forinfrared spectroscopy, in particular in the field of fuel oil analysis. Itstransmittance at 200 nm is relatively low (0.60), but at 500 nm it goes up to 0.96–0.97 and stays at that level until 9 μm, then it starts falling off (0.85 for 10 μm and 0.42 for 12 μm). The refractive index is about 1.46 from 700 nm to 5 μm.[11]
Barium fluoride is also a common, very fast (one of the fastest)scintillators for the detection ofX-rays,gamma rays or other high energy particles. One of its applications is the detection of 511keV gamma photons inpositron emission tomography. It responds also to alpha and beta particles, but, unlike most scintillators, it does not emit ultraviolet light.[12] It can be also used for detection of high-energy (10–150 MeV)neutrons, using pulse shape discrimination techniques to separate them from simultaneously occurring gamma photons.
Barium fluoride is used as apreopacifying agent and inenamel and glazing frits production. Its other use is in the production ofwelding agents (an additive to somefluxes, a component of coatings forwelding rods and in welding powders). It is also used inmetallurgy, as a molten bath for refiningaluminium.
In the vapor phase theBaF2 molecule is non-linear with an F-Ba-F angle of approximately 108°.[13] Its nonlinearity violatesVSEPR theory. Ab initio calculations indicate that contributions from d orbitals in the shell below the valence shell are responsible.[14] Another proposal is that polarisation of the electron core of the barium atom creates an approximately tetrahedral distribution of charge that interacts with the Ba-F bonds.[15]
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