Authors: L.H. Oliveira, A.P. de Moura, L.S. Cavalcante, S.A. Gutierrez, E. Longo, J.A. Varela
Affilation: Universidade Federal de São Carlos, Brazil
Pages: 394 - 397
Keywords: photoluminescence, microwave hydrothermal method, Rietveld refinement, XANES spectroscopy
In this work, (Ca1-xCux)TiO3 crystals with (x = 0, 0.01 and 0.02), were synthesized by the microwave-hydrothermal method at 140ºC for 32 min. The photo-physical properties were studied to analyze the influence of Cu2+ doping in the CaTiO3 photoluminescence response. XRD patterns, Rietveld refinement and FT-Raman spectroscopy indicated that these crystals present a CaTiO3 perovskite-type orthorhombic structure (Pbnm). The Rietveld refinement, micro-Raman and XANES spectra suggested that the substitution of Ca by Cu in A-site promoted a displacement of the [TiO6]−[TiO6] clusters adjacent from its symmetric center, which leads distortions on the [CaO12] clusters neighboring and consequently cause the strains into the CaTiO3 lattice. FE-SEM images showed that these crystals have an irregular shape as cube like probably indicating an Ostwald-ripening and self-assemble as dominant mechanisms to crystals growth. The powders presented an intense PL blue-emission. As the concentration of copper increases it was observed reduction in the intensity PL emission as well as a shift for green emission up to x = 0.01. In this work, we believe that distorted [CaO12] and [TiO6] clusters in the powders have great importance and contribute significantly to possible electronic transitions between the valence band and conduction band after excitation process.