Síntese e caracterização do aluminato de estrôncio dopado via sol-gel modificado para aplicação como pigmento cerâmico

Abstract

In the present work, Dy3+ co-doped SrAl2O4:Eu3+ was produced via proteic sol-gel method, a modified sol-gel route which allows the formation of oxides at lower temperatures than other methods. CO2 laser sintering was used as a method for heat treatment, effective in reducing trivalent europium ions in doped samples. Thermal analysis of the precursors, performed by TG and DTA, revealed that the crystallization of SrAl2O4 phase occurs at approximately 1060 °C. By X-ray diffractometry of the samples characterized before and after sintering was verified monoclinic and hexagonal phases formation. DLS technique revealed the presence of nanosized and micrometric particles, and particle agglomerates, result which was confirmed by SEM images before and after sintering. Micrographs of the fracture surface of a sintered pellet revealed a high degree of densification caused by heat treatment. Photoluminescence measurements showed that the samples after synthesis and before the heat treatment with laser have reddish emission, composed of characteristic narrow emission lines from Eu3+ and more intense emission when the samples are excited at 265 nm. The laser treatment promotes the reduction of Eu3+ to Eu2+ and this effect is confirmed by the presence of a wide emission band in the green region of the spectrum with a maximum emission obtained after excitation at 350 nm. The luminescent decay time of the thermally treated sample was approximately 100 minutes. Via XRF measurements of acquired frits, DTA and TG of the frits, of the pigment and of mixtures of both, and via applications of the mixtures on ceramic plates it was noticed good compatibility in terms of thermal processes, that indicates that the pigment have a potential to be used in ceramic floor tiles.