Thermoluminescence and ESR centers of Fluorapatite crystal from Brazil

Abstract

Apatite Ca5(PO4)3(OH, F, CI) can be found in nature in igneous, sedimentary and metamorphic rocks. Many authors studied the TL and PTTL emission of apatite and observed anomalous fading in its emission. Ishii et al reported a study about ESR, TL and Fission Track (FT) of the fluorapatite. They used the hole center O- that substituted F (g = 2.0027 and g = 2.0528) to evaluate an equivalent dose (Q) of the sample. In the present work we investigated TL properties above KT in fluorapatite mineral sample to observe the stability of the TL emission. We have characterized the glow peaks through second order kinetics based on the monoemergetic trap model, determining the TL glow peak parameters (activation energy, E and frequency factor, s) and the mean life of the TL traps. Regeneration and additive dose methods were applied in order to observe the TL growth curves of the peaks. Furthermore, we tried to identify the ESR centers and also to analyze theirs growths with γ-ray irradiation to determine the equivalent dose (Q) of the sample. In the studied sample Ce and La were found as impurity that can replace Ca in fluorapatite crystal lattice. These rare earth elements are well-known luminescence centers that can be used in TL dosimeters and laser crystal. It is guessed that they may be the impurities related to TL emission.