nbo

NbO, or niobium(II) oxide, is a substoichiometric oxide of niobium with the nominal formula NbO. It is one of several oxides of niobium, alongside more common forms such as NbO2 and Nb2O5. NbO arises under reducing conditions and is characterized by a non-stoichiometric composition with niobium in a relatively low oxidation state.

Structurally, NbO adopts a defective rock-salt (NaCl-type) lattice. In the ideal rock-salt arrangement, niobium and oxygen occupy alternating octahedral sites in a cubic close-packed framework. In NbO, intrinsic vacancies on the niobium sublattice are present and can become ordered at lower temperatures, producing the non-stoichiometric NbO phase. This defect structure gives NbO distinct physical properties compared with the perfect oxide.

NbO can be prepared by reducing higher niobium oxides, such as Nb2O5 or Nb2O3, in hydrogen at elevated temperatures, or by controlled oxidation of Nb metal under specific oxygen partial pressures. The material can also form as a phase in Nb-rich oxide systems.

Physically, NbO behaves as a metallic conductor and exhibits high hardness and chemical stability typical of transition metal oxides with significant defect content. Its electrical conductivity and defect chemistry make NbO a useful model system for studying non-stoichiometry and electron behavior in metal oxides.

Applications and research interest for NbO focus on fundamental defect chemistry, synthesis of niobium oxide materials, and potential uses as precursors to more oxidized niobium oxides or as components in ceramic and catalytic systems. See also NbO2, Nb2O5, and related niobium oxides.