gamma-Fe.sub.2./sub.O.sub.3./sub. nanopowders synthesized in microwave plasma and extraordinarily strong temperature influence on their Mössbauer spectra

0392673 - FZÚ 2014 RIV US eng J - Článek v odborném periodiku
David, Bohumil - Pizúrová, Naděžda - Schneeweiss, Oldřich - Šantavá, Eva - Kudrle, V. - Jašek, O.
gamma-Fe₂O₃ nanopowders synthesized in microwave plasma and extraordinarily strong temperature influence on their Mössbauer spectra.
Journal of Nanoscience and Nanotechnology. Roč. 12, č. 12 (2012), s. 9277-9285. ISSN 1533-4880
Institucionální podpora: RVO:68081723 ; RVO:68378271
Klíčová slova: gamma-Fe₂O₃ * nanoparticles * Mössbauer and Raman spectra * XRD * TEM * magnetic meas
Kód oboru RIV: BM - Fyzika pevných látek a magnetismus
Impakt faktor: 1.149, rok: 2012

Two nanopowders synth. in microwave plasma:the first one in a torch discharge at 1 bar,the second one in low-pressure plasma at 40 mbar. Morphology, composition and properties studied by TEM, XRD, Raman and Mössbauer spectra, magnetic meas.. By XRD only gamma- Fe2O3 identified (mean crystallite size dXRD 24 nm for the first and 13 nm for the second one). From the Mössbauer spectra meas.at 5 K, no other iron oxide phases found in both samples. Unusually strong temp. dependence of the Lamb-Mössbauer factor observed: ISA(5 K)/ISA(293 K)=6 in the case of the first sample and ISA(5 K)/ISA(293 K)=22 for the second sample (ISA denotes integral spectrum area),which explained as the consequence of the reduced clump of electrically charged nanoparticles in the plasma, i.e., particles can either move at 293 K (when they are free) or tilt (if they are a chain part). No superparamagnetic phase at 293 K by Mössbauer spectra of both samples.
Trvalý link: http://hdl.handle.net/11104/0221465