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Synthesis and Properties of Fluorovermiculite with High Contents of Iron

Title data

Baumgartner, Alexander ; Mariychuk, Ruslan ; Seidl, Wolfgang ; Porteanu, Horia ; Wagner, Friedrich E. ; Dubbe, Andreas ; Moos, Ralf ; Breu, Josef:
Synthesis and Properties of Fluorovermiculite with High Contents of Iron.
2004
Event: 12. Vortragstagung der GDCh-Fachgruppe Festkörperchemie und Materialforschung , 12.-15.09.2004 , Gießen, Deutschland.
(Conference item: Conference , Poster )

Abstract in another language

Vermiculite [Cs0.5]Inter[Mg2.5Al0.5]Oct[AlSi3]TetO10(OH,F)2 is a member of the 2:1-layered silicates family with medium layer charge. The complete substitution of OH_ groups by F_ leads to an increase of thermal and chemical stability. Incorporation of transition metals into the crystal structure of fluoro-vermiculite leads to new materials with interesting magnetic, conducting and photo-chemical properties. Here we report the synthesis and the investigation of physical and chemical properties of [Cs0.5]Inter[Mg2.5_xFe2_xAl0.5]Oct[AlSi3]Tet O10F2. The substitution is limited to x _ 1.5 for crystal chemical reasons [1]. The lateral dimension of the octahedral layer increases with incorporation of Fe2_ to the point where the tetrahedral layer can no longer adjust in order to fit these two structural building blocks of 2:1 layered silicates. As a consequence, compositions with octahedral layers being too large can not be realised. Moessbauer spectroscopy (MB) confirms that all Fe is indeed Fe2_ and that it has octahedral coordination. No tetrahedral Fe is observed. Beginning at 15 K a continuously increasing magnetic ordering is observed with low temperature MB. This behaviour can be explained with a distribution of superparamagnetic clusters, similar to what has been observed for olivines. Electrical conductivity was measured with microwave resonance spectroscopy and with impedance spectroscopy. Impedance measurements have been carried out between 300 and 600 °C and at different oxygen fugacities. With both methods the material shows a conductivity comparable to other semiconducting transition metal oxides and that it is sensitive to oxygen. From impedance measurements the activation energy is estimated to be 0.50 eV. Keeping in mind that the vermiculites can easily be pillared by cation exchange to yield micro-porous materials the observation of conductivity will open pathways to interesting sensor materials.

Further data

Item Type: Conference item (Poster)
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Faculties
Faculties > Faculty of Engineering Science > Chair Functional Materials
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Profile Fields
Profile Fields > Advanced Fields
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 29 Jun 2015 11:25
Last Modified: 05 Apr 2016 06:49
URI: https://eref.uni-bayreuth.de/id/eprint/15420