Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen. XIV. Oxydationsprodukte von orthorhombischem Nb12O29 Elektronenoptische Untersuchung

Contributions to the Investigation of Inorganic Non-stoichiometric Compounds. XIV. Oxidation Products of Orthorhombic Nb₁₂O₂₉, Electron Optical Investigation An electron optical investigation shows that the orthorhombic starting material Nb₁₂O₂₉(BII) is well ordered. The oxidation products Nb₂O₅(Ox1BII) and Nb₂O₅(Ox2BII) are different from each other in structures as well as in their reactions. Nb₂O₅(Ox1BII) is unstable in the electron beam and differs from BII by characteristic point-defects. The radiation load can lead to the reduction to BII or to a transition into a defect structure with R-type-tunnels. The not well ordered structure of Nb₂O₅(Ox2BII) is stable in the electron beam. Characteristic is the sequence of 2×5] and 3×4] blocks, the latter in two different orientations. The observed composition O/Nb = 2.500 can be described by the present structural modell assuming vacant niobium tetrahedral sites. The large structural differences between the oxidation products of the orthorhombic and the monoclinic Nb₁₂O₂₉ are remarkable.