## Abstract

We have investigated the defect structure of nonstoichiometric wüstite Fe1-xO as a function of temperature and oxygen partial pressure by means of diffuse elastic neutron scattering of a single crystal at thermal equilibrium. Particularly for T=1423 K and x=0.08, a Fourier analysis yielded short-range order and lattice displacement parameters as well as the ratio of the numbers of vacancies to interstitials, ρ=4.0±0.5. The measured short-range order showing a strong correlation between nearest interstitials and vacancies was simulated in a computer model. A further analysis yielded the size distribution of the vacancy-interstitial defect clusters exhibiting a large fraction of 30% of free vacancies, while a further 15% of the defects are bound in isolated so-called 4:1 defect clusters. The entire long-range displacement fields were modeled in a Kanzaki force approach using independent phonon data. Within the usual approach of a single-defect approximation the observed asymmetries of the diffuse scattering around the Bragg peaks were described by using Coulomb-like forces around the cation vacancies of random 4:1 defect clusters. The measured decrease of Huang scattering and the development of diffuse peaks with increasing nonstoichiometry was reproduced by a more general type of Kanzaki model for concentrated solid solutions. Therefore, we used the same defect model of the 4:1 cluster, although surrounded with two occupied cation shells to screen the long-range displacement fields.

Original language | English |
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Pages (from-to) | 15771-15788 |

Number of pages | 18 |

Journal | Physical Review B |

Volume | 51 |

Issue number | 22 |

DOIs | |

State | Published - 1995 |