Marcia R. S. Silva

Effect of the composition on the thermal behaviour of the SrSn1-xTixO3 precursor prepared by the polymeric precursor method

Strontium stannate titanate Sr(Sn, Ti)O3 is a solid solution between strontium stannate (SrSnO3) and strontium titanate (SrTiO3). In the present study, it was synthesized at low temperature by the polymeric precursor method, derived from the Pechini process. The powders were calcined in oxygen atmosphere in order to eliminate organic matter and to decrease the amount of SrCO3 formed during the synthesis. The powders were annealed at different temperatures to crystallize the samples into perovskites-type structures. All the compositions were studied by thermogravimetry (TG) and differential thermal analysis (DTA), infrared spectroscopy (IR) and X-ray diffraction (XRD). The lattice former, Ti4+ and Sn4+, had a meaningful influence in the mass loss, without changing the profile of the TG curves. On the other hand, DTA curves were strongly modified with the Ti4+:Sn4+ proportion in the system indicating that intermediate compounds may be formed during the synthesis being eliminated at different temperature ranges, while SrCO3 elimination occurs at higher temperature as shown by XRD and IR spectra.

Influence of Nd Doping on the Properties of SrTiO3 thin Films Synthesized by PLD on Different Substrates

SrTiO3, SrTi0.99Nd0.01O3 and Sr0.99Nd0.01TiO3 thin films were synthesized by pulsed laser deposition at 700 °C on different substrates (silica, R-sapphire, (100) LaAlO3 and (100) MgO). The influence of Nd3+ substitution into the A and B sites of SrTiO3 perovskite on film growth was studied. The films were characterized by X-ray diffraction (θ-2θ, θ- and θ-scans), micro-Raman spectroscopy, UV-Vis spectroscopy and field-emission scanning electron microscopy. All of the films exhibited a (h00) orientation and high-quality epitaxial growth on LaAlOθ. The films grown on MgO, with the exception of the SrTiNd0.01O3 film, also exhibited a (h00) orientation. The polycrystallinity of the SrTi0.99Nd0.01O3 film may be related to the increased lattice distortion when Ti4+ was replaced with Nd3+. A polycrystalline growth was observed for all of the films deposited on silica and R-sapphire, as expected. The Raman results showed that Nd doping led to an increase in the short-range disorder. The morphology strongly depended on the nature of the substrate and on Nd doping, specially in the case of SrTi0.99Nd0.01O3.