On the Valence State of Iron in Sr_0.5²⁺Ca_0.5²⁺Fe_0.5⁴⁺ Me_0.5⁴⁺O₃²⁻

Abstract

A b s t r a c t . Powder samples of Sro,sCao~SFe,~,~e,,~O~ (Me = Co, Zr or Mn) and Sr,.3La0.,Fe03 are investigated by X-ray diffraction and Mossbauer effect spectroscopy.Analysis of the completely ordered spectra suggested three kinds of iron ions coexist in general where the resolution into the different valence state is clearly seen. The Nossbauer effect parameters values are found to be close to those expected for Fe3+, Fed+ and Fe5+ indicating that some of the tetravalent iron ions in its high spin state disproportionate into Fe3+ and Fe5+ ions passing through temperature dependent intermediate valence states. Zum Valenzzustand des Eisens in S r~.~C a~.~F e P , ; t , M e~.~O~-I n h a l t s u b e r s i c h t . Pulverproben von Sr,~SCa,.,Feo~,Meo,,03 (Me = Co, Zr oder Mn) und Sro,3Lao~,Fe03 wurden niittels Rontgenstreuung und Mossbauer-Spektroskopie untersucht. Die Analyse der gesamten geordneten Spektren weist auf drei koexistierende Eisenionarten hin, die klar voneinander nnterschieden werden konnen. Ihre Mossbauerparameter sind nahe den fur Fe3+, Fe*+ und Fe5+ erwarteten und legen nahe, da13 einige der tetravalenten Eisenionen in hohem Spinzustand in Fe3+-und Fe5+-Ionen iiber tempemtiirabhingige Zwischenvalenzzustande aufspalten.

The study of 57Fe Mössbauer spectra for La0.7Sr0.3FeO3−δ with different structure

“…It was thought that Fe ions were in average valence states or that electron hopping existed between Fe3+ and Fe4+ [6,71,3. Fe4+ and Fe5+ ions as well as Fe3' ions were detected at low temperature [8]. In this paper, by measuring the 57Fe Mossbauer spectra of Lao.7Sro.3Fe03 -6 with different structures, we investigated and discussed the changes of the Fe ion state in the different structures.…”