Open AccessLocal structural properties of (Mn,Fe)Nb 2 O 6 from Mössbauer and X‐ray absorption spectroscopy
Author(s) -
Ghigna Paolo,
McCammon Catherine,
Amantea Roberta,
Carpenter Michael A.,
Tarantino Serena C.
Publication year - 2005
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
eISSN - 1600-5740
pISSN - 0108-7681
DOI - 10.1107/s0108768105008116
Subject(s) - extended x ray absorption fine structure , mössbauer spectroscopy , xanes , octahedron , crystallography , hyperfine structure , bond length , coordination number , manganese , materials science , absorption (acoustics) , x ray absorption fine structure , analytical chemistry (journal) , spectroscopy , x ray absorption spectroscopy , spectral line , mössbauer effect , chemistry , absorption spectroscopy , ion , crystal structure , atomic physics , physics , organic chemistry , quantum mechanics , chromatography , astronomy , metallurgy , composite material
The MnNb 2 O 6 –FeNb 2 O 6 solid solution has been investigated by Fe–K‐ and Mn–K‐edge X‐ray absorption (XANES and EXAFS), and Mössbauer spectroscopy. The first‐shell M —O bond lengths deduced from EXAFS show a fairly small compositional dependence. A degree of static disorder, which increases with increasing manganese content, is clearly seen by the loss of correlation for the next‐neighbour (NN) interaction. Hyperfine parameters from Mössbauer spectra are consistent with variations in the average environment, as recorded by X‐ray data. Line broadening of the Mössbauer spectra provides evidence for next‐neighbour effects and is consistent with there being no significant clustering of Fe or Mn within the samples. There appear to be differences in the way the columbite structure accommodates Fe 2+ and Mn 2+ ions. In ferrocolumbite all the Fe octahedra are close to being identical, while there are local structural heterogeneities at a longer length scale, presumably in ordering the precise topology of polyhedra immediately adjacent to the octahedron. By contrast, the manganocolumbite seems to have some diversity in the precise coordination at the MnO 6 octahedra, but a greater uniformity in how the adjacent polyhedra are configured around them.