On the synthesis and physical properties of iron doped SnO2 nanoparticles.

The synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanoparticles have a dominant SnO2 phase (as revealed by Wide Angle X-ray Scattering), with particles of the order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmed by SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-ray Scattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersed within the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sn content suggesting that the magnetization is not controlled solely by the amount of Fe dispersed within the nanoparticles.

Iron oxide-based nanoparticles with different mean sizes obtained by the laser pyrolysis: structural and magnetic properties.

Nano-sized iron oxide-based particles have been directly synthesized by the laser induced pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer)/ethylene (as sensitizer). In this paper we further demonstrate the possibility to vary the chemical composition and the nanoparticle dimensions of the iron oxide-based materials by handling the oxidation procedure in the frame of the laser pyrolysis process. Thus, nanoparticles with major maghemite/magnetite content may change composition into mixtures with variable amounts of three components: major gamma-Fe2O3/Fe3O4 iron oxide, metallic Fe and cementite Fe3C. By X-ray diffraction (XRD) it is found that the relative proportion of these phases differs in function of the reaction temperature (laser power). As revealed by transmission electron microscopy (TEM), mean particle sizes between about 4 nm and 6 nm and between about 9 and 11 nm may be prepared by varying the oxidation procedure and the laser power, respectively. By the controlled heating of samples (maximum temperature 185 degrees C), increased crystallinity for the gamma-Fe2O3/Fe3O4 oxide phase was found as well as an increase of the mean particle diameters. The examination of the magnetization curves for samples obtained for different laser powers indicates notable differences in the magnetic behavior and parameters. The temperature dependent Mossbauer measurements confirm the formation of larger particles at higher laser power densities as well as the presence of inter-particle magnetic interactions. On this basis, the estimation of phase composition for the different representative samples is given.