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This work describes the obtaining of cobalt-doped tin oxide nanoparticles using the method of controlled precipitation. The synthesized powders were used to form stable slurry, using as solvent water and 64% in solids, adding the suspension 5% ammonium polyacrylate -- PAA as a deflocculant and tetraetil ortosilicato -- TEOS. With this slip, and using the colloidal method (slip casting), were obtained in green pieces to sintering to 1250 °C, 2 hours, presented a uniform porous microstructure and a 94% of theoretical density, to doping sample with 2% by weight of Co, very suitable microstructure considering these parts used as active material in devices gas sensors. [ABSTRACT FROM AUTHOR]

Ceramic powders of pure barium stannate (BaSnO 3 ) were synthesized using two wet chemical methods: controlled precipitation and polymeric precursor (Pechini). The obtained ceramic powders were characterized using IR spectroscopy, DTA–TGA, XRD and SEM. Using the precipitation and Pechini methods, single phase BaSnO 3 powders were achieved at temperatures of 1250 °C and 1000 °C respectively—substantially lower than the temperatures required for conventional synthesis (> 1350 °C). Leading from these results, the physicochemical mechanisms that lead to BaSnO 3 formation in the processes of synthesis employed in this work are proposed. This constitutes important information both for determining the advantages and disadvantages of each method and for controlling the characteristics of the powder end product. [ABSTRACT FROM AUTHOR]

Tin oxide, SnO2, has a big technological importance. For its uses it is of great interest to optimize the sintering conditions to obtain an adequate densification, microstructure and mechanical properties, depending on the technological application. In this paper, ceramic powders of SnO2 obtained by controlled precipitation method were sintered. Powders were shaped to obtain "green" pieces using both pressing and by the casting method ("slip casting") for this. For the slip casting method was realized a careful study of SnO2 suspensions to obtain a stable slurry. For determine the effect of shaping methods on the densification of pieces, were obtained important information analyzing the results of curves of weight loss, shrinkage and densification, as temperature functions, of the different samples. Finally, the sintered pieces were characterized using SEM to know their microstructure. The shaped pieces using colloidal method showed the higher density values (ρ= 4,2 ± 0,2 g/cm3). These samples showed a uniform microstructure with very small pores. These characteristics would allow their use as membranes or gas sensors. [ABSTRACT FROM AUTHOR]

The titanium dioxide, TiO2, is a material of technological importance for their physicochemical properties. Also is known that material properties depend of synthesis process used for their production, condition that is more demanding in new technologies, specifically in nanotechnology. In this work we used two methods of synthesis, sol-gel and polymeric precursor (Pechini), we realized a comparative analysis of the two processes. The synthesized powders were characterized using infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (TEM and SEM). With the results we determined the effect of the synthesis methods on the characteristics of the final product. The powders obtained presented nanometric size and primary anatase crystalline phase, from a temperature up of 450°C. The presence of AcacH complexing, in the system, reduced the size of the agglomerates and modified their morphology. [ABSTRACT FROM AUTHOR]

Perovskite nanoparticles MSnO 3 (M = Ba, Zn, Ca) were synthesized at low temperature in a controllable and reproducible way, using the polymer complex method. The physicochemical, structural and optical characteristics of the mixed oxides were determined using DTA/GTA, XRD, FTIR, SEM/TEM, DRS and XPS. The pure crystalline phases were obtained between 700 and 800 °C, with particle size less than 80 nm, a spheroidal morphology in the BaSnO 3 and ZnSnO 3 , and laminar in the CaSnO 3. The band-gap energy between 3.4 and ~4.6 eV were obtained. Urbach energy (E u) was calculated to determine the degree of disorder of the synthesized perovskites, with BaSnO 3 giving the highest E u value (417 meV). This result indicates the existence of defects, e.g. oxygen vacancies, a condition that was verified by deconvolution and analysis of XPS spectra. Considering the nature of the synthesis process and the results obtained, a mechanism was proposed to explain the formation of the perovskites. [Display omitted] • Nanoparticles of the MSnO 3 (M = Ba, Zn, Ca) system were successfully synthesized using the polymer complex method. • A suitable description of the synthesis process was indicated in the study. • A mechanism to explain the formation of the perovskites was put forward. • Structural and optical characterization of the perovskites MSnO 3 (M = Ba, Zn, Ca) was undertaken. • The energy that determine the degree of disorder of the synthesized perovskites was calculated. [ABSTRACT FROM AUTHOR]