Electrical and magnetic properties ofNb2O5−δcrystallographic shear structures

The reduced niobium oxides ${\mathrm{Nb}}_{25}$ ${\mathrm{O}}_{62}$, ${\mathrm{Nb}}_{47}$ ${\mathrm{O}}_{116}$, ${\mathrm{Nb}}_{22}$ ${\mathrm{O}}_{54}$, and ${\mathrm{Nb}}_{12}$ ${\mathrm{O}}_{29}$ 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 ${\mathrm{Nb}}_2$ ${\mathrm{O}}_{5\mathrm{-}\mathrm{\delta }}$. Electrical conductivities increase with increasing reduction: ${\mathrm{Nb}}_{12}$ ${\mathrm{O}}_{29}$ is a metallic conductor down to 0.3 K. All show, surprisingly, Curie-Weiss behavior in the χ-vs-T curves, with ${\mathrm{Nb}}_{12}$ ${\mathrm{O}}_{29}$ ordering antiferromagnetically at 12 K.