Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

The reduction of crystals of Nb₁₂O₂₉, having an excess of oxygen, has been studied by high-resolution electron microscopy and electron diffraction. A superstructure and faulted slabs are formed, by aggregation of the point defects forming chains with a limited length in the matrix structure, induced by electron-beam irradiation. Ordering of the chains of point defects in the crystals is directly observed by electron microscopy with resolution of the atomic level. A mechanism for the dissipation of the point defects is discussed in terms of the reduction and oxidation of the nonstoichiometric crystals of Nb₁₂O₂₉.