Caracterização óptica e estrutural do titanato de magnésio contendo cobalto divalente como íon emissor

Abstract

Mg2TiO4 inverse spinel ceramics were prepared using the acetate method in pure forms and containing Co2+ for concentrations 0.1%, 0.5 %, 1%, 5%, 10% and 50%. For the structural characterization of these samples, X-ray diffraction and X-ray fluorescence measurements were carried out. The obtained results confirm the formation of Mg2TiO4 as the main phase and the presence of MgTiO3 as secondary phase. X-ray diffraction data were adjusted using the Rietveld method for refining crystalline structures, which allowed the quantification of the phases and the crystalline parameters. The optical properties of photoluminescence, as well as the effect of the activating ion Co2+, were investigated as a function of concentration. The crystal field parameters were calculated using the optical spectra in conjunction with the Tanabe-Sugano theory. The photoluminescence spectra exhibited emission in the red-near-infrared region for samples with concentrations 0.1% and 0.5%. The emission spectrum of the sample with a concentration of 0.1% Co2+ showed a broad and homogeneous band centered at 716 nm, which was attributed to the spin-allowed transition 4 T1 (4P) → 4 A2 (4F) resulting from the occupation of Co2+ in the tetrahedral sites of Mg2TiO4. The transition 4T1 (4P) → 4 T2 (4F) was also identified at 854 nm, associated with a weak and narrow band. The sample that showed the best photoluminescence emission was the Mg2TiO4: Co2+ sample containing 0.1% divalent cobalt.