Lanthanum(III) bromide

Lanthanum(III) bromide

Names
IUPAC names Lanthanum(III) bromide Lanthanum tribromide
Identifiers
CAS Number	13536-79-3
ChemSpider	75393
EC Number	36-896-7
Jmol interactive 3D	Image
PubChem	83563
InChI InChI=1S/3BrH.La/h3*1H;/q;;;+3/p-3 Key: XKUYOJZZLGFZTC-UHFFFAOYSA-K InChI=1/3BrH.La/h3*1H;/q;;;+3/p-3 Key: XKUYOJZZLGFZTC-DFZHHIFOAJ
SMILES Br[La](Br)Br
Properties
Chemical formula	LaBr3
Molar mass	378.62 g/mol (anhydrous)
Appearance	white solid, hygroscopic
Density	5.06 g/cm^3, solid
Melting point	783 °C (1,441 °F; 1,056 K)
Boiling point	1,577 °C (2,871 °F; 1,850 K)
Solubility in water	Not Published Yet (very soluble in water)
Structure
Crystal structure	hexagonal (UCl3 type), hP8
Space group	P63/m, No. 176
Coordination geometry	Tricapped trigonal prismatic (nine-coordinate)
Hazards
EU classification (DSD)	not listed
Flash point	not flammable
Related compounds
Other anions	Lanthanum(III) fluoride Lanthanum(III) chloride Lanthanum(III) iodide
Other cations	Cerium(III) bromide Praseodymium(III) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Lanthanum(III) bromide (LaBr₃) is an inorganic halide salt of lanthanum. When pure, it is a colorless white powder. The single crystals of LaBr₃ are hexagonal crystals with melting point of 783 °C. It is highly hygroscopic and water-soluble. There are several hydrates, La₃Br·X H₂O, of the salt also known. It is often used as a source of lanthanum in chemical synthesis, and is being evaluated for use as a scintillation material in certain applications.

Uses

Cerium activated lanthanum bromide is the recent inorganic scintillator which has a combination of high light yield and the best energy resolution.

Lanthanum bromide scintillation detector

Recent advances in scintillator material have resulted in the development of cerium activated lanthanum bromide (LaBr₃) detectors. LaBr₃ was discovered in 2001.^[1] These detectors offer improved energy resolution, fast emission and excellent temperature and linearity characteristics. Typical energy resolution at 662 keV is 3% as compared to sodium iodide detectors at 7%.^[2] The improved resolution is due to a photoelectron yield that is 160% greater than is achieved with sodium iodide. Another advantage of LaBr₃ is the nearly flat photo emission over a 70 °C temperature range (~1% change in light output).

Today LaBr₃ detectors are offered with bialkali photomultiplier tubes (PMT) that can be two inches in diameter and 10 or more inches long . However, miniature packaging can be obtained by the use of a silicon drift detector (SDD). These UV enhanced diodes provide excellent wavelength matching to the 380 nm emission of LaBr₃. A paper presented at the 2005 IEEE Nuclear Science Symposium shows that the SDD has a higher quantum efficiency over the PMT . Moreover, the SDD is not as sensitive to temperature and bias drift. The reported spectroscopy performance of the SDD configuration resulted in a 2.8% energy resolution at 662 keV for the detector sizes considered.

LaBr₃ introduces an enhanced set of capabilities to a range of gamma spectroscopy radioisotope detection and identification systems used in the homeland security market. Isotope identification utilizes several techniques (known as algorithms) which rely on the detector’s ability to discriminate peaks. The improvements in resolution allow more accurate peak discrimination in ranges where isotopes often have many overlapping peaks. This leads to better isotope classification. Screening of all types (pedestrians, cargo, conveyor belts, shipping containers, vehicles, etc.) often requires accurate isotopic identification to differentiate concerning materials from non-concerning materials (medical isotopes in patients, naturally occurring radioactive materials, etc.) Heavy R&D and deployment of instruments utilizing LaBr₃ is expected in the upcoming years. (List of companies who manufacture commercial off-the-shelf Radiation Isotope Identifiers for Homeland Security: Canberra Industries, ORTEC, Berkeley Nucleonics, spectra sample and spectroscopy example])

References

1. E. V. D. van Loef, P. Dorenbos, C. W. E. van Eijk, K. W. Kraemer and H. U. Guedel Appl. Phys. Lett. 79 2001 1573
2. Knoll, Glenn F., Radiation Detection and Measurement 3rd ed. (Wiley, New York, 2000).