Beiträge zur Untersuchung anorganischer nichtstöchiometrischer Verbindungen. XXXV [1, 2]. Reduktion von Blockstrukturen im Elektronenmikroskop - in situ - Beobachtung einer topotaktischen Reaktion im System Nb2O5/WO3

Contributions to the investigation of inorganic non-stoichiometric compounds. XXXV. Reduction of block structures by heating with the electron beam -- in situ investigation of a topotactic reaction in the system Nb₂O₅/WO₃ In quenched samples with the starting composition Nb₂O₅: WO₃ ≈? 1:1 we observed by using high resolution transmission electron microscopy (HRTEM) areas with large blocks of 5 × n] M–O octahedra (n = 6, 7, 8, 9; M = Nb, W). Upon heating with the electron beam a structural change occurs as an in-situ reaction. The original 5 × n] blocks are splitting up mostly in two 5 × 1/2n] blocks (n even) or when n is odd into one block with 5 × 1/2(n + 1)] and one with 5 × 1/2(n--1)] M–O octahedra. The splitting up of blocks forces some corner sharing octahedra to become edge sharing octahedra. This change of connections constitutes a partial reduction of the sample.