Light emission bands in the radioluminescence and thermoluminescence spectra of kaolinite

This work is focused on the study of the thermoluminescence (TL) and radioluminescence (RL) properties of a well-characterized kaolinite. Both TL and RL spectra exhibited complex glow curves that were deconvoluted into five wavebands at about 370, 425, 464, 544 and 680 nm. The low wavelength emissions were linked to structural defects that induced strains in the lattice due to the presence of the hydroxyl groups. Green and red emissions were associated with Mn2+ and Fe3+ ions. Unlike other aluminosilicates, the sample did not display the 290 nm waveband that is attributable to the presence of Na ions. The chemical analysis by ICP-MS indicated the absence of this alkali ion. The estimation of the activation energy for each TL waveband using the initial rise method revealed the existence of traps at the same depth (ca. 1.06 ± 0.09 eV) regardless of the spectral region.