CaTiO 3 and Ca 1−3x Sm x TiO 3 : Photoluminescence and morphology as a result of Hydrothermal Microwave Methodology

Abstract

Calcium titanate (CaTiO 3 -CT) and samarium doped calcium titanate (CaTiO 3 :Sm 3 þ -CT:Sm) powders in different Sm 3 þ concentrations (0.5-5.0% molar ratio of Sm 3 þ ) were obtained by the Hydrothermal Microwave Methodology at 140 1C for 16 min. These crystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy. Field emission scanning electron microscopy images were employed to observe the shape and size of the crystals. The optical properties were investigated by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) measurements. The XRD indicated structural organization at long range while MR revealed short range order for all undoped and Sm-doped samples. Morphological analysis revealed a new cubic morphology for CT:Sm, presenting an average size of 3.0 μm. Further, the ultraviolet-visible absorption spectra indicated the existence of intermediary energy levels within the band gap. The maximum intensity PL emission occurred due to 4 G 5/2 -6 H 7/2 and 4 G 5/2 -6 H 9/2 transitions of Sm 3 þ . CIE chromaticity coordinates of the samples were determined and support these materials are promising candidates for applications as phosphors in the visible orange range. This research concluded that the methodology employed here was responsible for the presence of unusual and interesting properties for these new luminescent materials.

Ftir and Raman Spectroscopic Study of a Complex Perovskite: Ca0.91-XCe0.09Rb0.04Csx[(Zr0.50Ti0.45)Al0.05]O3, X=0.2 to 0.4, Dedicated for Radioactive Waste Confinement

“…The band at 246 cm -1 , reported in the literature at 244 cm -1 , is overlapping the hard mode B1g (P4) assigned to the oxygen octahedron cage rotation [69,71]. The symmetrical stretching (794 cm -1 ) derived from A1g vibrations of TiO6 octahedrons movement does not appear [72], due to steric considerations and to B site cations' nature (Ti 3+ , Zr 4+ ), these last inhibiting TiO6 spectroscopic study of a complex perovskite: Ca0.91-xCe0.09Rb0.04Csx[(Zr0.50Ti0.45)Al0.05]O3, x=0.2 to 0.4, dedicated for radioactive waste confinement stretching.…”

“…Penatti I.M. et al [69] report these bands, in a comparative table, at 172, 219, 237, 280 and 333 cm -1 . A morphotropic phase boundary, which is mainly associated to the Ag (P2) band (181 cm -1 ) indicates an orthorhombic phase [67,71].…”

“…I.M. Penatti et al [69] attribute the absence of some perovskite modes to their low polarizabilities. The B1+E (P5) mode (280 cm -1 [68]) shifts to 278 cm -1 .…”

“…The P2 to P6 perovskite modes are strongly depend on the metal-oxygen distances, and their bands vary as a function of the dopants in both A and B positions, these last, in turn, affect the modes polarizabilities [69][70][71]. The bands at 181 cm -1 , and 224, 246, 278, 339 cm -1 are assigned to O-Ti-O bending (P2 to P6 modes, respectively) [71].…”

Effect of concentration of Nd3+ on the photoluminescence and ferroelectric properties of Bi4-xNdxTi3O12 films

“…The emission intensity reaches the maximum when the concentration of Nd 3+ is equal to 0.45, which indicates quenching concentration is about 0.45. Concentration quenching mechanism is highly relevant to the critical interaction distance between neighboring activators in the host lattice [40,41].…”