P. N. Lisboa-Filho

Microstructural and morphological analysis of pure and Ce-doped tin dioxide nanoparticles

Structural and morphological studies in pure and Ce-doped tin dioxide nanoparticles with high stability against particle growth were performed in samples, obtained using the polymeric precursor method and prepared at different annealing temperatures. A Ce-rich surface layer was used to control the particle size and stabilize SnO2 against particle growth. The formation of this segregated layer can contribute to a decreased surface energy, acting in the driving force, or reducing the surface mobility. Only the cassiterite SnO2 phase was observed below 1000 � C and a secondary phase (CeO2) was observed for the Ce-doped SnO2 at temperatures higher than 1000 � C, when de-mixing process occurs. The evolution of crystallite size, microstrain and morphology of the nanoparticles with annealing temperatures was investigated by X-ray diffraction (XRD), associated to Rietveld refinements, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). # 2002 Elsevier Science Ltd. All rights reserved.

The influence of cation segregation on the methanol decomposition on nanostructured SnO2

Abstract Here we describe a new route to synthesize ultrafine rare earth doped and undoped tin oxide particles for catalytic applications. The catalytic behavior observed in SnO2 samples suggests the control of the catalytic activity and the selectivity of the products by the segregation of a layer of a rare earth compound with the increase of the heat-treatment temperature. The ultrafine particles were characterized by means of BET, XPS, TEM, XRD and Rietveld refinement. It was demonstrated that the effects of the dopant on the methanol decomposition reaction and on the H2 selectivity were correlated with the segregation of a rare earth layer on the tin oxide samples.

Specific heat at low temperatures and magnetic measurements inNd0.5Sr0.5MnO3andR0.5Ca0.5MnO3(R=Nd,Sm, Dy, and Ho) samples

We studied the magnetization as a function of temperature and magnetic field in the compounds

Synthesis and characterization of Li2ZnTi3O8 spinel using the modified polymeric precursor method

{\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3},

Granularity in superconductors: intrinsic properties and processing-dependent effects

{\mathrm{Nd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},

Superconductivity in sintered-polycrystalline PrBa2Cu3O7−δ

{\mathrm{Sm}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},

Structural, optical, and magnetic properties of NiMoO4 nanorods prepared by microwave sintering.

{\mathrm{Dy}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},