Optical and Electrical Properties of SnO 2

Tin oxide films were deposited on glass substrates by reactive and non reactive r.f. sputtering using different types of targets corresponding to various Sn/F atomic ratio: hot pressed Sn–SnF2 or SnO2–SnF2 mixtures, ceramics obtained by casting either an aqueous SnO2–SnF2 slurry or a suspension of tin oxide in molten tin fluoride. The samples were prepared in oxygen-argon gas mixtures in which the oxygen concentration was varied from 0 mole % up to 30 mole% depending on the target. The optical and electrical properties of the obtained thin films have been studied and compared to those of the films obtained by spray technique

Fe-substituted mullite powders for the in situ synthesis of carbon nanotubes by catalytic chemical vapor deposition

Powders of iron-substituted mullite were prepared by combustion and further calcination in air at different temperatures. A detailed study involving notably Mo¨ssbauer spectroscopy showed that the Fe3+ ions are distributed between the mullite phase and a corundum phase that progressively dissolves into mullite upon the increase in calcination temperature. Carbon nanotube-Fe-mullite nanocomposites were prepared for the first time by a direct method involving a reduction of these powders in H2-CH4 and without any mechanical mixing step. The carbon nanotubes formed by the catalytic decomposition of CH4 on the smallest metal particles are mostly double-walled and multiwalled, although some carbon nanofibers are also observed

SODIUM IRON FLUOROPHOSPHITE GLASSES PART II. EPR AND MÖSSBAUER RESONANCE STUDY

EPR and Mössbauer measurements have been performed on sodium iron fluorophosphate glasses. Mössbauer spectra show the presence of Fe3+ and Fe2+ both in octahedral coordination sites. However, for low iron concentration, EPR suggests a small number of Fe3+ tetrahedra coexisting with Fe3+ octahedra. On the basis of these results, Fe3+ tetrahedrally and/or octahedrally coordinated, connected with P(O,F)4 tetrahedra would behave as a network-former cation, whereas Fe2+ would substitute for Na+ as a network-modifier. Long range magnetic order previously observed by magnetic measurements has been confirmed for iron-rich compositions