Lanthanum hexaboride

Crystal structure
	__ La 3+ __ B
General
Surname	Lanthanum hexaboride
Ratio formula	LaB 6
Brief description	purple odorless powder
External identifiers / databases
EC number	234-531-6
ECHA InfoCard	100,031,379
PubChem	133108840
Wikidata	Q410318
properties
Molar mass	203.78 g mol −1
Physical state	firmly
density	2.61 g cm −3
Melting point	2210 ° C
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Lanthanum hexaboride (LaB ₆ ) is an inorganic compound of boron and lanthanum and belongs to the borides .

Extraction and presentation

Lanthanum hexaboride can be obtained by reacting lanthanum oxide with sodium borohydride at 1200 ° C, lanthanum chloride with sodium borohydride and magnesium at 400 ° C, or lanthanum nitrate with boron and a fuel.

properties

Lanthanum hexaboride is a refractory ceramic material with a melting point of 2210 ° C. It is odorless and has a purple color. It is insoluble in water and hydrochloric acid .

Lanthanum hexaboride has a cubic crystal structure with the space group Pm 3 m (space group no. 221) . Its structure has been known since 1930. Template: room group / 221

use

Lanthanum hexaboride cathode

The material is vacuum stable, and is characterized by an extremely low electron work function only 2.7 eV from. It is therefore used, among other things, in plasma technology and as an electron source ( hot cathode ) in some electron microscopes .

Borides as well as lanthanum hexaboride can be added to a transparent polymer in the form of very fine particles in low concentrations as a laser absorber without significantly changing its visible optical properties. An absorption of laser radiation with a wavelength of 1064 nm of the frequently used Nd: YAG laser is achieved. This can then be used for laser marking or laser welding of such materials.

Furthermore, due to its favorable reflective positions, lanthanum hexaboride is used as a standard substance for quantitative X-ray diffraction measurements ( XRD ).

literature

T. Lundström: Structure, defects and properties of some refractory borides . In: Pure Appl. Chem. Band 57 , no. 10 , 1985, pp. 1383–1390 ( PDF - crystal structure and color changes of lanthanum hexaboride).

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g Data sheet Lanthanum boride, 99.5% (REO) from AlfaAesar, accessed on December 7, 2019 ( PDF )(JavaScript required) .
↑ Jean Etourneau, Jean-Pierre Mercurio, Roger Naslain, Paul Hagenmuller: Structure electronique de quelques hexaborures de type CaB ₆ . In: Journal of Solid State Chemistry . 2, 1970, pp. 332-342, doi : 10.1016 / 0022-4596 (70) 90091-5 .
↑ Bao Lihong, Wurentuya, Wei Wei, O. Tegus: A new route for the synthesis of submicron-sized LaB6. In: Materials Characterization. 97, 2014, p. 69, doi : 10.1016 / j.matchar.2014.08.011 .
↑ Maofeng Zhang, Liang Yuan, Xiaoqing Wang, Hai Fan, Xuyang Wang, Xueying Wu, Haizhen Wang, Yitai Qian: A low-temperature route for the synthesis of nanocrystalline LaB6. In: Journal of Solid State Chemistry. 181, 2008, p. 294, doi : 10.1016 / j.jssc.2007.12.011 .
^ Yoseph Bar-Cohen: High Temperature Materials and Mechanisms . CRC Press, 2014, ISBN 978-1-4665-6646-0 , pp. 171 ( limited preview in Google Book search).
↑ MM Korsukova, T. Lundström, V. Ν. Gurin, L.-E. Tergenius: An X-ray diffractometry study of LaB6 single crystals, prepared by high-temperature solution growth. In: Journal of Crystallography - Crystalline Materials. 168, 1984, doi : 10.1524 / zkri.1984.168.14.299 .
↑ springer.com: LaB6 Crystal Structure - SpringerMaterials , accessed June 21, 2016.
↑ Treibacher Industrie AG: Boride .
↑ Wissenschaft-online.de: leaving work .
↑ sindlhauser.de: LaB6 ceramics and cathodes .
↑ patent WO2006029677 . ‌
↑ Dr AK Singh, Defense Metallurgical Research Laboratory (Hyderabad India): Advanced X-ray Techniques in Research and Industry . IOS Press, 2005, ISBN 978-1-58603-537-2 ( google.de [accessed January 9, 2018]).

[alfa-1] ↑ ^a ^b ^c ^d ^e ^f ^g Data sheet Lanthanum boride, 99.5% (REO) from AlfaAesar, accessed on December 7, 2019 ( PDF )(JavaScript required) .

[2] Jean Etourneau, Jean-Pierre Mercurio, Roger Naslain, Paul Hagenmuller: Structure electronique de quelques hexaborures de type CaB ₆ . In: Journal of Solid State Chemistry . 2, 1970, pp. 332-342, doi : 10.1016 / 0022-4596 (70) 90091-5 .

[DOI10.1016/j.matchar.2014.08.011-3] Bao Lihong, Wurentuya, Wei Wei, O. Tegus: A new route for the synthesis of submicron-sized LaB6. In: Materials Characterization. 97, 2014, p. 69, doi : 10.1016 / j.matchar.2014.08.011 .

[DOI10.1016/j.jssc.2007.12.011-4] Maofeng Zhang, Liang Yuan, Xiaoqing Wang, Hai Fan, Xuyang Wang, Xueying Wu, Haizhen Wang, Yitai Qian: A low-temperature route for the synthesis of nanocrystalline LaB6. In: Journal of Solid State Chemistry. 181, 2008, p. 294, doi : 10.1016 / j.jssc.2007.12.011 .

[Yoseph_Bar-Cohen-5] Yoseph Bar-Cohen: High Temperature Materials and Mechanisms . CRC Press, 2014, ISBN 978-1-4665-6646-0 , pp. 171 ( limited preview in Google Book search).

[DOI10.1524/zkri.1984.168.14.299-6] MM Korsukova, T. Lundström, V. Ν. Gurin, L.-E. Tergenius: An X-ray diffractometry study of LaB6 single crystals, prepared by high-temperature solution growth. In: Journal of Crystallography - Crystalline Materials. 168, 1984, doi : 10.1524 / zkri.1984.168.14.299 .

[springer.com-7] springer.com: LaB6 Crystal Structure - SpringerMaterials , accessed June 21, 2016.

[Austrittsarbeit-8] Treibacher Industrie AG: Boride .

[Austrittsarbeit_2-9] Wissenschaft-online.de: leaving work .

[LaB6-10] sindlhauser.de: LaB6 ceramics and cathodes .

[Lasermarkierung-11] tent WO2006029677 . ‌

[12] Dr AK Singh, Defense Metallurgical Research Laboratory (Hyderabad India): Advanced X-ray Techniques in Research and Industry . IOS Press, 2005, ISBN 978-1-58603-537-2 ( google.de [accessed January 9, 2018]).