Decomposition and ordering in Fe_1−xO

Abstract

Samples in the composition range Fe0.gsO-Feo.880 quenched from about 1000°C, have been studied by electron diffraction/microscopy with special emphasis on the dark-field technique. The set of morphologies obtained by quenching and annealing confirms a spinodal-like decomposition in an oxygen-rich and an almost stoichiometric component. The diffraction spots and dark-field images reveal a considerable degree of order which is enhanced upon heat treatment below 300°C. Previous diffraction studies have been interpreted in terms of an ordered phase with cubic symmetry. Dark-field microscopy, particularly at the symmetric composition, showed that the compositional fluctuation wave contained domains of tetragonal or orthorhombic symmetry at a very early stage. The range of order was found to increase during decomposition. An ordered phase of orthorhombic symmetry developed in oxygen-rich samples. Superstructure spots could be indexed by an A-faced orthorhombic cell with dimensions five times the fundamental cell.Extinctions lead to the space group Abm2 and a periodic antiphase relation. Only four types of clusters, all of which are based on three connected defect tetrahedra, are then possible.

The commensurate (10/4) cluster model in quenched wüstite P''. New simulation of HREM direct images

“…(b) Generally, it has been shown that the long-range ordering is not cubic; a (2.5X, 2-5X, 5)0 superstructure has frequently been observed linked with the presence of stacking faults for values of z close to 0.09-0.10 (Andersson & Sletnes, 1977;Ishiguro & Nagakura, 1985.…”

Paracrystal Formation from Ni1−xO and CaO upon Interdiffusion

“…E-mail: pshen@mail.nsysu.edu.tw. assemble into larger units (e.g., 13:4, 16:5 and form a paracrystal (4,5)) which order further into Fe O spinel or other ordered phases: p and p (6,7). (The paracrystalline distribution is such that the spacing between defect clusters tends to be maintained fairly constant but relative lateral translations may occur more variably; hence, there is negligible di!raction intensity beyond "rst order (4,5).…”

Formation and Growth of Iron Nuclei on Wüstite Surface at the Initial Stage of Reduction

“…5) According to the previous results obtained by X-ray diffraction, neutron diffraction, transmission electron microscope (TEM) and computer simulation, defect clusters are periodically arranged every 2.5-2.7a 0 (a 0 is the lattice parameter of the rock-salt type FeO). [6][7][8][9][10][11][12] However, there are only limited reports on the surface structures of bulk Fe 1-x O. The surface crystal structures of Fe 1-x O were only studied in terms of a thin film on a substrate using scanning tunneling microscope (STM), low energy electron diffraction (LEED) and/or Auger electron spectroscopy (AES).…”