Niobium (IV) oxide

Crystal structure
__ Nb 4+      __ O 2−
General
Surname	Niobium (IV) oxide
other names	Niobium dioxide
Ratio formula	NbO 2
Brief description	black powder
External identifiers / databases
CAS number 12034-59-2 EC number 234-809-7 ECHA InfoCard 100,031,632 PubChem 82839 Wikidata Q408470
properties
Molar mass	124.91 g mol −1
Physical state	firmly
density	5.98 g cm −3 (α mod.) 5.84 g cm −3 (β mod.)
Melting point	1915 ° C
boiling point	3500 ° C
solubility	almost insoluble in water (at 20 ° C) practically insoluble in hydrochloric, sulfuric and nitric acid
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Niobium (IV) oxide is a chemical compound from the group of oxides of niobium .

Extraction and presentation

Niobium (IV) oxide can be obtained by reacting niobium (V) oxide with hydrogen at 800–1350 ° C. An alternative production method is the reaction of niobium (V) oxide with niobium powder at 1100 ° C.

${\displaystyle {\ce {Nb2O5 + H2 -> 2 NbO2 + H2O}}}$

${\displaystyle {\ce {Nb + 2 Nb2O5 -> 5 NbO2}}}$

properties

Niobium (IV) oxide is a black, somewhat bluish powder. The above-mentioned preparation methods produce the α-niobium (IV) oxide. Besides a reversible conversion into a high-temperature form, a very closely structurally related β-modification is known. The latter can be accessed by means of transport (such as iodine , niobium (V) chloride , mercury (II) chloride ) from niobium (II) oxide - niobium (IV) oxide mixtures. Both crystal structures are derived from the rutile type , but differ in terms of niobium-niobium pairs. The α-modification has the space group I 4 ₁ / a (space group no. 88) and the lattice parameters a = 13.681, c = 5.976 Å . The β-modification has the space group I 4 ₁ (No. 80) with the lattice parameters a = 9.686, c = 5.985 Å. The homogeneity range of niobium dioxide extends from NbO _1.94 to NbO _2.09 . At temperatures below 500 ° C it easily reduces carbon dioxide to carbon, sulfur dioxide to sulfur and decomposes sodium hydroxide with the release of hydrogen. It oxidizes to niobium (V) oxide in air.

Individual evidence

1. ↑ ^{a b c} Datasheet Niobium (IV) oxide, −200 mesh from Sigma-Aldrich , accessed on August 11, 2011 ( PDF ).
2. ↑ ^{a b c} Georg Brauer (ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 , p. 1463.
3. ↑ ^{a b} C. K. Gupta, AK Suri, S Gupta, K Gupta (1994), Extractive Metallurgy of Niobium , CRC Press, ISBN 0849360714
4. ↑ THERMOPHYSICAL, ELECTRICAL, AND OPTICAL PROPERTIES OF SELECTED METAL-NONMETAL TRANSITION MATERIALS , Comprehensive Bibliography With Typical Data, YS TOULOUKIAN, CY HO, and JF CHANEY, CINDAS REPORT 50, February 1978
5. ↑ Data sheet niobium (IV) oxide (PDF) from Merck , accessed on August 11, 2011.
6. ^ ^{A b} R. Blachnik: Pocket book for chemists and physicists Volume 3: Elements, inorganic compounds and materials, minerals . Springer-Verlag, 2013, ISBN 978-3-642-58842-6 , pp. 1444 ( limited preview in Google Book search).
7. ↑ Pradyot Patnaik (2002), Handbook of Inorganic Chemicals , McGraw-Hill Professional, ISBN 0070494398
8. ^ CK Gupta, AK Suri: Extractive Metallurgy of Niobium . CRC Press, 1993, ISBN 978-0-8493-6071-8 , pp. 144 ( limited preview in Google Book search).