Sintering SnO 2 under argon flow at temperatures in the range of 1350-1500°C causes the formation of wires, rods, and tubes on the sample surface. At high temperatures of the mentioned range, microwires with lengths of hundreds of microns are formed. At lower temperatures the formation of micro-and nanorods as well as micro-and nanotubes takes place. The influence of ball milling of the starting powder on the formation of tubes is investigated. The local cathodoluminescence measurements show a different defect structure in the tubes than in the sample background.

Indium oxide elongated micro- and nanostructures have been grown by thermal treatment of InN powder. Chains of nanopyramids connected by nanowires, forming a necklace-like structure, as well as cubes and arrow-like structures consisting of a long rod with a micron size pyramid on the top, grow at temperatures in the range 600–700°C in a catalyst free process. The structures have been characterized by scanning electron microscopy and cathodoluminescence.

Anatase TiO 2 nanoparticles doped with Al or Fe have been synthesized via a modified Pechini method which allows us to reach high control in size and composition. Microstructural analysis confirms the good crystallinity of the doped anatase nanoparticles with average sizes around 5 nm and dopant cationic concentrations up to 30%. The anatase to rutile transition (ART) has been thermally driven and analyzed as a function of the doping. Thermo-diffraction measurements indicate that the phase transition can be either promoted or inhibited by Fe or Al doping, respectively. The influence of Al and Fe doping on the phase transition has been discussed by means of Raman spectroscopy, photoluminescence and X-ray photoelectron spectroscopy, with special attention paid to the role played by Ti 3+ at the surface. The anatase phase has been stabilized up to temperatures above 900 C by appropriate Al doping.

Polycrystalline samples of titanium oxide were prepared by thermal sintering, in argon and air atmospheres at temperatures ranging from 1100 to 1500 • C, from powders of anatase and rutile phases. The samples sintered in argon were further treated in oxygen at the temperature of 800 • C for intervals of time up to 8 h. The luminescence emission of the initial powders was situated in the green region, with the peak at 580 nm. The sintering treatment in argon leads to a decrease of the luminescence intensity that appears as a broad band peaked at 550 nm in the case of anatase and as a band peaked at 450 nm in the case of the rutile phase. The sintering treatment in air causes the quenching of the emission in the visible region. In both cases, a sharp and intense emission appears in the infrared region at 800 nm for rutile and 820 nm for the anatase phase.The blue emission is sensitive to the treatment in oxygen atmosphere which causes mainly an intensity increase of the band at 450 nm. The treatment in oxygen results in the reconstruction of the polycrystalline sample surface as hexagonal shape protrusions and large terraces.

Cathodoluminescence ͑CL͒ in the scanning electron microscope ͑SEM͒ has been used to investigate the luminescence mechanisms in tin oxide. Sintered material prepared from high purity powder has been found to show a strong dependence of the CL emission on the thermal treatments applied during sample preparation. SEM images show the presence of nano and microcrystalline grains. The correlation of the grain size and morphology with the optical emission is analyzed by CL microscopy and spectroscopy. The main emission bands appear centered at about 2.58, 2.25, and 1.94 eV depending on the sintering treatment. CL images reveal that the 2.25 and the 2.58 eV bands are associated at specific crystal faces. The evolution of the luminescence bands with mechanical milling shows a complex evolution of the 1.94 and 2.58 eV emissions which is explained by formation and recovery of defects during milling.