Atmospheric-pressure Microwave Torch Discharge Generated γ-Fe2O3 Nanopowder

AbstractMicrowave torch discharge ignited in Ar at 1bar was used for the synthesis of γ-Fe2O3 nanoparticles. A double- walled nozzle electrode enabled to introduce gases separately: Ar flowed in the central channel, whereas the mixture of H2/O2/Fe(CO)5 was added into the torch discharge through an outer channel. The composition and properties of the synthesized nanopowders were studied by TEM, XRD, Raman and Mössbauer spectroscopies. Basic magnetic measurements at low/high temperatures were performed. The γ-Fe2O3 phase with the mean crystallite size of 24nm was identified by XRD in the representative sample. The measured Raman spectrum matched well those reported for γ-Fe2O3 powders in the literature. In the transmission Mössbauer spectrum measured at 5K the two sextets characteristic for γ-Fe2O3 were clearly identified. No change in specific magnetic moment typical of Fe3O4 at its Verwey temperature was observed on the zero field curve, which smoothly increased with temperature. Neither Fe3O4 nor α-Fe2O3 were present in the sample. We also report on the high-temperature magnetic properties of the representative sample and describe its structural changes and phase transformations up to 1073K