Niobium (V) oxide

Crystal structure
__ Nb 5+      __ O 2−
General
Surname	Niobium (V) oxide
other names	Diniobium pentoxide Niobium oxide (ambiguous)
Ratio formula	Nb 2 O 5
Brief description	white, odorless powder
External identifiers / databases
CAS number 1313-96-8 EC number 215-213-6 ECHA InfoCard 100.013.831 PubChem 123105 Wikidata Q419787
properties
Molar mass	265.81 g · mol -1
Physical state	firmly
density	4.55 g cm −3
Melting point	1491 ° C (α modification)
solubility	practically insoluble in water
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	> 10,000 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Niobium (V) oxide is a chemical compound from the group of oxides of the element niobium . It is in the form of a non-flammable, white and odorless powder.

Extraction and presentation

Niobium (V) oxide is formed when niobium is oxidized in air. In its pure form, it can be obtained by hydrolysis of niobium (V) chloride .

${\displaystyle \mathrm {2\ NbCl_{5}+5\ H_{2}O\longrightarrow Nb_{2}O_{5}+10\ HCl} }$

Niobium (V) oxide can also be obtained from niobium ethoxide Nb (OC ₂ H ₅ ) ₅ in a sol-gel process .

properties

Niobium (V) oxide has a monoclinic crystal structure and a refractive index of 2.3 at 500 nm and is transparent in the range from 350 to 7000 nm. However, niobium (V) oxide occurs in several modifications, of which the mostly present B form is stable below 750 ° C. It crystallizes monoclinically in flakes and has a structure like antimony (V) oxide with an almost hexagonally dense oxygen lattice. The connection of the coordination polyhedra corresponds to the rutile type with the space group B 2 / b (space group no. 15, position 2) , a = 1273 pm, b = 556 pm, c = 488 pm, γ = 105 ° 05 '. The H-form is thermodynamically stable above about 750 ° C.

use

Niobium (V) oxide is used to increase the refractive index in optical glasses, e.g. B. in lenses for cameras and copiers as well as in eyeglass lenses used. It is also used for the production of lithium niobate and calcium barium niobate.

See also

• Niobium (II) oxide
• Niobium (IV) oxide

Individual evidence

1. ↑ ^{a b c d e f} Entry on niobium (V) oxide in the GESTIS substance database of the IFA , accessed on March 29, 2018(JavaScript required) .
2. ↑ ^{a b} Data sheet niobium (V) oxide (PDF) from Merck , accessed on February 20, 2010.
3. ↑ Science24: Tuning the nanostructuration of Nb ₂ O ₅ oxides for specific optical non-linear properties
4. ↑ Paperback for chemists and physicists: Volume 3; Elements, inorganic compounds and materials, minerals; By Roger Blachnik, Jean D'Ans, Ellen Lax, Claudia Synowietz; Springer Verlag 1998; ISBN 3-540-60035-3 .
5. ↑ Foyol: Evaporation Materials ( Memento of the original from March 5, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
6. ↑ Georg Brauer (ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1465.