Textural, structural and electrical properties of SnO_2 nanoparticles prepared by the polyol method

摘要

Nanocrystalline mesoporous SnO_2 nanoparticles were synthesized by the polyol method followed by thermal annealing. The composition, texture, structure and morphology of the samples treated at 90, 500 and 700 ℃ in air were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR), thermogravimetry coupled to mass spectrometry (DTA/TGA/MS) and Nitrogen Sorption Porosimetry. FTIR and TGA-MS data indicate that tin oxide species were obtained with a complete removal of polyol residues after thermal treatment above 500 ℃. XRD patterns reveal that nanocrystallites of cassiterite, i.e. rutile-like tetragonal structure, SnO_2 were formed after annealing, the average crystallite size increasing with the temperature of the thermal post-treatment. Moreover, TEM and N_2 sorption porosimetry show that the calcined samples are composed of an aggregated network of almost spherical nanoparticles, the mesoporosity observed being related to the interparticle space. Finally, electrical properties of the SnO_2 nanopowder calcined at 700 ℃ were studied between 543 and 723 K, in the 200 Hz-5 MHz frequency range by impedance measurements. Bulk conductivity dependence with temperature was found to follow an Arrhenius law with an activation energy of 0.68 eV that is typical of tin dioxide nanopowders.