Temperature assisted radiative and non-radiative recombination mechanisms in sillimanite (AlSiO) mineral.

Temperature assisted luminescence in sillimanite (AlSiO) mineral was studied using thermoluminescence (TL). TL characteristics were studied in un-annealed and different annealed samples. Analysis showed that in the un-annealed sample, there was four electron trapping sites at depths ~0.56, 0.87, 1.08, 1.32eV and a hole trapping site at depth ~3.63eV from the conduction band acting as a recombination center. Further analysis on the annealed samples showed that the 0.56eV trapping site was a pressure induced surface trap and it disappeared after annealing. However, the other trapping and recombination sites were found to be stable under thermal treatment. Due to this trap distribution, three partially overlapping glow peaks were observed. The glow peaks were found to be affected by thermal quenching. The thermal quenching parameters were evaluated from the composite glow curves by using Computerized Resolved Peak (CRP) technique. The activation energies for thermal quenching (W) estimated from the three peaks were found to be ~0.69±0.05, 0.92±0.06 and 1.15±0.03eV respectively and the pre-exponential factors (C) were ~1.12×10, 2.65×10 and 9.23×10 respectively. Based on the analysis, a band model was proposed and the whole radiative and non-radiative recombination mechanisms were discussed.