Preparation and characterization of both,iron-zinc manganites at different iron content (x = Fe/(Fe + Zn) 0, 0.01, 0.05, 0.10) and their carbonate precursors are reported. In,particular, structural properties and the iron chemical state I were investigated., Precursors, obtained by coprecipitation at constant pH,were in all cases monophasic and,made by,a rhodochrosite like FexZnyMn(1-x-y)CO3, phase. Mossbauer spectroscopy proved that, surprisingly, Fe3+ was 95% of total iron. A hypothesis about the charge compensation mechanism in the rhodochrosite-like structure is given. The carbonate precursors were decomposed in air at 721, and 973 K, leading at both temperatures to monophasic iron-zinc manganites characterized by a distorted.. spinel-like structure with tetragonal symmetry. In such a structure, trivalent Mn3+ ions and bivalent Zn2+, ions are perfectly ordered in the octahedral and, tetrahedral sites of,the crystal lattice, respectively, as expected for a 'normal' spinel. Mossbauer investigation revealed-that iron is present-As trivalent ions in the octahedral sites and that no iron extra-phases Wefd, formed. Moreover,three. doublets corresponding to octahedral Fe3+ ions were. detected, likely related to different distributions of Fe3+/Mn3+ cations in the next nearest coordination sphere.
Iron chemical state and structural properties of Fe-Zn manganites and their carbonate precursors / G., Fierro; Lojacono, Mariano; R., Dragone; Giovanni, Ferraris; Andreozzi, Giovanni Battista; Graziani, Giorgio. - In: DIFFUSION AND DEFECT DATA, SOLID STATE DATA. PART B, SOLID STATE PHENOMENA. - ISSN 1012-0394. - 90-91:(2003), pp. 153-158. (Intervento presentato al convegno 5th International Conference on Solid State Chemistry tenutosi a BRATISLAVA, SLOVAKIA nel JUL 07-12, 2002) [10.4028/www.scientific.net/ssp.90-91.153].
Iron chemical state and structural properties of Fe-Zn manganites and their carbonate precursors
LOJACONO, Mariano;ANDREOZZI, Giovanni Battista;GRAZIANI, Giorgio
2003
Abstract
Preparation and characterization of both,iron-zinc manganites at different iron content (x = Fe/(Fe + Zn) 0, 0.01, 0.05, 0.10) and their carbonate precursors are reported. In,particular, structural properties and the iron chemical state I were investigated., Precursors, obtained by coprecipitation at constant pH,were in all cases monophasic and,made by,a rhodochrosite like FexZnyMn(1-x-y)CO3, phase. Mossbauer spectroscopy proved that, surprisingly, Fe3+ was 95% of total iron. A hypothesis about the charge compensation mechanism in the rhodochrosite-like structure is given. The carbonate precursors were decomposed in air at 721, and 973 K, leading at both temperatures to monophasic iron-zinc manganites characterized by a distorted.. spinel-like structure with tetragonal symmetry. In such a structure, trivalent Mn3+ ions and bivalent Zn2+, ions are perfectly ordered in the octahedral and, tetrahedral sites of,the crystal lattice, respectively, as expected for a 'normal' spinel. Mossbauer investigation revealed-that iron is present-As trivalent ions in the octahedral sites and that no iron extra-phases Wefd, formed. Moreover,three. doublets corresponding to octahedral Fe3+ ions were. detected, likely related to different distributions of Fe3+/Mn3+ cations in the next nearest coordination sphere.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
