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Niobium pentoxide
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Niobium pentoxide
Niobium pentoxide is the inorganic compound with the formula Nb2O5. A colorless, insoluble, and fairly unreactive solid, it is the most widespread precursor for other compounds and materials containing niobium. It is predominantly used in alloying, with other specialized applications in capacitors, optical glasses, and the production of lithium niobate.
It has many polymorphic forms all based largely on octahedrally coordinated niobium atoms. The polymorphs are identified with a variety of prefixes. The form most commonly encountered is monoclinic H-Nb2O5, which has a complex structure with a unit cell containing 28 niobium atoms and 70 oxygen, where 27 of the niobium atoms are octahedrally coordinated and one tetrahedrally. There is an uncharacterised solid hydrate, Nb2O5·nH2O, the so-called niobic acid (previously called columbic acid), which can be prepared by hydrolysis of a basic solution of niobium pentachloride or Nb2O5 dissolved in HF.
Molten niobium pentoxide has lower mean coordination numbers than the crystalline forms, with a structure comprising mostly NbO5 and NbO6 polyhedra.
Nb2O5 is prepared by hydrolysis of alkali-metal niobates, alkoxides or fluoride using base. Such ostensibly simple procedures afford hydrated oxides that can then be calcined. Pure Nb2O5 can also be prepared by hydrolysis of NbCl5:
A method of production via sol-gel techniques has been reported hydrolysing niobium alkoxides in the presence of acetic acid, followed by calcination of the gels to produce the orthorhombic form, T-Nb2O5.
Given that Nb2O5 is the most common and robust compound of niobium, many methods, both practical and esoteric, exist for its formation. The oxide for example, arises when niobium metal is oxidised in air. The oxidation of niobium dioxide, NbO2 in air forms the polymorph, L-Nb2O5.
Nano-sized niobium pentoxide particles have been synthesized by LiH reduction of NbCl5, followed by aerial oxidation as part of a synthesis of nano structured niobates.[citation needed]
Nb2O5 is attacked by HF and dissolves in fused alkali.
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Niobium pentoxide
Niobium pentoxide is the inorganic compound with the formula Nb2O5. A colorless, insoluble, and fairly unreactive solid, it is the most widespread precursor for other compounds and materials containing niobium. It is predominantly used in alloying, with other specialized applications in capacitors, optical glasses, and the production of lithium niobate.
It has many polymorphic forms all based largely on octahedrally coordinated niobium atoms. The polymorphs are identified with a variety of prefixes. The form most commonly encountered is monoclinic H-Nb2O5, which has a complex structure with a unit cell containing 28 niobium atoms and 70 oxygen, where 27 of the niobium atoms are octahedrally coordinated and one tetrahedrally. There is an uncharacterised solid hydrate, Nb2O5·nH2O, the so-called niobic acid (previously called columbic acid), which can be prepared by hydrolysis of a basic solution of niobium pentachloride or Nb2O5 dissolved in HF.
Molten niobium pentoxide has lower mean coordination numbers than the crystalline forms, with a structure comprising mostly NbO5 and NbO6 polyhedra.
Nb2O5 is prepared by hydrolysis of alkali-metal niobates, alkoxides or fluoride using base. Such ostensibly simple procedures afford hydrated oxides that can then be calcined. Pure Nb2O5 can also be prepared by hydrolysis of NbCl5:
A method of production via sol-gel techniques has been reported hydrolysing niobium alkoxides in the presence of acetic acid, followed by calcination of the gels to produce the orthorhombic form, T-Nb2O5.
Given that Nb2O5 is the most common and robust compound of niobium, many methods, both practical and esoteric, exist for its formation. The oxide for example, arises when niobium metal is oxidised in air. The oxidation of niobium dioxide, NbO2 in air forms the polymorph, L-Nb2O5.
Nano-sized niobium pentoxide particles have been synthesized by LiH reduction of NbCl5, followed by aerial oxidation as part of a synthesis of nano structured niobates.[citation needed]
Nb2O5 is attacked by HF and dissolves in fused alkali.
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