Ferriti di stronzio nanostrutturate: sintesi e caratterizzazione

Due to their important and diverse properties, together with their thermal and mechanical stability, mixed transition metal oxides having perovskite crystal structures have long been object of study and technological applications. In this framework, strontium ferrite SrFeO3-x holds particular interest due to its capability to act as both an electronic and ionic conductor at high temperatures (becoming capable to conduct O2- ions through vacancies in its crystal structure) and thus employable both in fuel cells (as an electrode) and oxygen concentrating devices[1]. Moreover also the magnetic and catalytic properties of this compound are also to be considered. In this work, the perovskite SrFeO3-x has been obtained through coprecipitation. Three synthetic paths have been explored: coprecipitation of hydroxides from an aqueous solution, coprecipitation of oxalates from an aqueous solution and polyol-assisted coprecipitation[2]. Products of all three synthetic paths were analyzed by means of powder XRD and XPS to determine the purity of the sample and to optimize the synthetic process itself. Pure samples were further characterized by means of ICP analysis, nitrogen adsorption, elemental analysis and Mössbauer spectroscopy. In particular, XRD and Mössbauer spectroscopy were used respectively to deduce the crystal structure of the obtained powders and to analyze the oxidation states and magnetic properties of the iron atoms contained in the sample, thus allowing to estimate the magnitude of the defects (as an oxygen vacancy would result in the presence of Fe(III) rather than Fe(IV)).