Nb 3d and O 1s core levels and chemical bonding in niobates

A set of available experimental data on binding energies of Nb 3d(5/2) and O 1s core levels in niobates has been observed with using energy difference (O 1s-Nb 3d(5/2)) as a robust parameter for compound characterization. An empirical relationship between (O 1s-Nb 3d(5/2)) values measured with XPS for Nb5+-niobates and mean chemical bond length L(Nb-O) has been discussed. A range of (O 1s-Nb 3d(5/2)) values possible in Nb5+-niobates has been defined. An energy gap similar to1.4-1.8 eV is found between (O 1s-Nb 3d(5/2)) values reasonable for Nb5+ and Nb4+ states in niobates. (C) 2004 Elsevier B.V. All rights reserved.