Computational and experimental analyses on the origin of TL and OSL signals in undoped and doped compounds

Abstract

The main objective of this work is to present the current knowledge concerning the origin of the luminescent signal generated through Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) techniques in well-known compounds. The discussion about this mechanism involves experimental analysis, atomistic simulation, and literature review. Materials such as undoped or doped magnesium tetraborate (MgB4O7) were examined as examples. The atomistic simulation was carried out using GULP, a well-established tool that enables, among others, the analysis of energy formation of various point defects. The experimental measurements were conducted using the Riso reader on materials that were produced and characterized. Combining different methodologies, it became feasible to ascertain the most likely point defects in each studied compound. The outcomes obtained from the study of undoped MgB4O7 enabled the identification of the likely defects responsible for the emitted signal in this material. We also developed a proposal to explain the formation of the MgO anti-Schottky defect, which presented the lowest energy solution (eV/defect) among the analysed defects. In the case of Li-doped MgB4O7, a hypothesis was postulated to elucidate the suppression in the signal caused by the presence of lithium. Furthermore, computational analysis was conducted on Ce-doped and Ce-doped/Li-codoped MgB4O7, which has garnered significant attention due to its potential applications as TLD and, more notably, OSLD. In this instance, experimental analysis and literature review revealed compelling evidence of a complicated correlation between the dopant concentrations and the resulting signals, which require further investigation in future studies. This type of information is highly significant in the present era when better comprehension of the origin of the signal could lead to an enhanced capability to design new dosimeters and gain deeper insights into the behavior of currently used materials.