Structural and optical properties of CaTiO3 perovskite-based materials obtained by microwave-assisted hydrothermal synthesis: An experimental and theoretical insight

Structural refinement and photoluminescence properties of irregular cube-like (Ca1−xCux)TiO3 microcrystals synthesized by the microwave–hydrothermal method

“…10(aec) were verified that the crystals are agglomerate and polydisperse. These microcrystals exhibit a shape as irregular cubes in agreement with the literature [15,27]. Some of these cube-like (Ca x Cu 1Àx )TiO 3 microcrystals are small, regular, very faceted and present a smooth surface that may be associated to the microwave irradiation exposure.…”

“…5(a), the pre-edge peak observed for (Ca 1Àx Cu x )TiO 3 is characteristic of a six-coordination of the octahedral [TiO 6 ] clusters, which is observed in well-crystallized titanates [41,42]. Besides that theoretical and experimental studies showed that for the perovskite type materials the higher intensity of this peak indicates that the local environment of Ti is non-centrosymmetric, i.e., is distorted from its symmetric center [7,27,39].…”

“…The literature [27] describes that the band gap energy is direct when the electronic transitions occur from the maximum-energy states (near or inside) the valence band (VB) to minimum-energy states (below or inside) the conduction band (CB), in a same regions in the Brillouin zone. Therefore, the presence of different E gap values calculated from the UVevis absorption spectra indicates the existence of intermediary energy levels between the valence and conduction band [54].…”

Local structure study of vanadium pentoxide 1D-nanostructures

“…Nevertheless, EXAFS results confirm that studied samples exhibit a similar coordination number, i.e., any significant change concerning the first coordination shell around the V atoms can be observed. Since the dependence of local order with photoluminescence properties has been reported for several nanostructures, like for titanates and vanadates (Nakajima et al 2010;Motta et al 2009;Moreira et al 2009;Longo et al 2008;Zhang et al 1998), the difference in PL intensity may be related to the local order for V-O sphere, as observed in Raman and XAS results.…”

“…In fact, several papers correlated some properties of different materials, like photoluminescence, to this aspect (Nakajima et al 2010;Moreira et al 2009;Motta et al 2009). …”