Radiation effect on the UV-green thermally stimulated luminescence emission of a natural Na-rich aluminosilicate.

Abstract

This paper reports on the thermoluminescence (TL) emission (from 250 to 500 nm) of a 10 Gy irradiated natural Na-rich aluminosilicate from Minas Gerais (Brazil), previously characterized by Raman spectroscopy and differential thermal analysis techniques. 3D-TL spectrum of the analyzed sample displays a complex glow curves with five different emissions bands peaked at 290, 380, 420, 460 and 500 nm that could be associated with structural and point defects. The UV-blue emission bands have the following characteristics: (i) the 290 nm waveband could be due to defects-sites by the presence of Na ions; (ii) the 380 nm band, caused by intrinsic defects in the lattice (i.e. Non-Bridging Oxygen Hole Centers (NBOHCs), [AlO4]o centres, alkali planar defects and Oxygen Defect Centers (ODCs), among others); (iii) the 420 nm waveband, linked to the recombination on a centre formed from a hole-oxygen atom adjacent to two aluminum atoms (Al-O-Al) and Al-O-Si complexes; (iv) the 460 nm band, associated with the presence of Ti4+ in the plagiclase crystal lattice. The green waveband could be linked to de-excitation of Mn2+ ions. The estimation of the activation energy (Ea) from the 10 Gy-induced TL glow curves analyzed by means of the initial rise method display linear regressions with acceptable r coefficients (r > 0.977) that reveal three groups of components with traps at different depth in the crystal lattice of the albite with Ea values in the range of 0.5–0.64 eV.