57Fe Mössbauer study on compositions of the series Fe3+TaO4-Fe2+Ta2O6 |
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| Authors: | E Schmidbauer J Lebküchner-Neugebauer |
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| Institution: | 1. Institut für Allgemeine und Angewandte Geophysik der Universit?t München, 8000, München, West-Germany
2. Institut für Werkstofftechnologie der Universit?t Dortmund, 4600, Dortmund, West-Germany
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| Abstract: | Fe57 Mössbauer spectra were measured on compositions of the series Fe1?x/3Ta1+x/3O4, 0≤x≤1. The spectra are characterized by mixed valencies of Fe2+ and Fe3+ ions for 0<x<1. Starting from x=0 with rutile structure, a trirutile structure forms towards x=1. Quadrupole splitting QS of Fe3+ is QS(Fe3+)≈0.55 mm/s and isomer shift IS is IS(Fe3+)≈0.40 mm/s (referred to Fe); both quantities exhibit minor variations along the series. The Fe2+ subspectra for x>0.5 were fitted using one symmetrical doublet; however, for x<0.5 two symmetrical doublets were necessary to describe these patterns. QS(Fe2+)=2.0–3.2 mm/s and IS(Fe2+)=0.90–1.15 mm/s for all compositions. In the case x<0.5, marked temperature dependent QS values appear to exist. This feature may be related to short range order effects and possibly also in part to intervalence electron transfer betwee Fe2+ and Fe3+ ions. |
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