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Ca x Sr 1Àx TiO 3 samples were synthesized by the microwave-assisted hydrothermal method. The X-ray diffraction results indicate that strontium calcium titanates powders show two crystalline structures: perovskite cubic and orthorhombic. The ultraviolet-visible spectra show that the band gap energies decrease with the Ca addition, suggesting imperfections or defects in the forbidden band of the titanates. The photoluminescence spectra show a broad band, which is usually observed at low temperatures in perovskite-type crystals. The nanoparticles show a nonuniform distribution with polyhedral morphology and spherical agglomerates, which change to faceted surfaces suggesting that the sample can reach other morphologies which ensure symmetry of lowest energy.

Single-nanobelt gas sensor devices were nanofabricated to estimate Sn3O4 and SnO2 Debye length (LD) in presence of NO2, and gas–solid interactions between O species/NO2 and Sn2+/Sn4+ surfaces were proposed based on tin oxide sensor signals.