Electrical and magnetic properties of Nb2O5-δ crystallographic shear structures

The reduced niobium oxides Nb25O62, Nb47O116, Nb22O54, and Nb12O29 have been prepared in pure polycrystalline form by a niobium-metal gettering technique. They are related to the high niobia parent structure through the action of cystallographic shear to accommodate oxygen deficiency in Nb2O5-δ. Electrical conductivities increase with increasing reduction: Nb12O29 is a metallic conductor down to 0.3 K. All show, surprisingly, Curie-Weiss behavior in the χ-vs-T curves, with Nb12O29 ordering antiferromagnetically at 12 K.