The paper explores the structure and luminescence of sol-gel-derived SnO 2 :Eu and SnO 2 :Eu,Sb nanopowders which may be useful as electrically conductive phosphors. The samples were sintered in air at temperatures reaching up to 1400°C. Raman-, SEM-, EDX-and photoluminescence characterization of the samples was carried out.High-temperature annealing of SnO 2 :Eu leads to a nanoparticulate phosphor with considerable efficiency of host-sensitized Eu 3+ emission under UV excitation although the emission is slightly quenched at room temperature. While Sb co-dopant immensely improves crystallization at 1400°C, it also impairs luminescence performance. SEM and EDX characterization suggest pronounced segregation of Eu induced by the enhanced crystal growth. Interestingly, Sb-doping seems to activate in the Raman spectrum quite a few SnO 2 vibrations which are normally rather weak or IR active.
The invention of electrospinning has solved the problem of producing micro-and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO 2 , TiO 2 , ZrO 2 , HfO 2 and CeO 2 ) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.
The pinching phenomenon is used to shape jets of
Sn(OBu)4
based viscous oligomeric melts into nanometre range sharp oxide needles. The
influence of viscosity of the liquid, humidity of surrounding environment and
pulling speed on formation of the needles is investigated. Optimal conditions enable
reproducible preparation of needles that have tip radii down to 15–25 nm, i.e. in the
range that is of considerable interest for many nanotechnological applications.
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