Characterisation of clay samples from minerals–rich deposits for thermoluminescence applications

Abstract

Thermoluminescent (TL) characteristics of clay samples from Ijero-Ekiti and Isan-Ekiti, Ekiti State, Nigeria were studied for application in retrospective dosimetry. In order to increase the potentials of the clay material for relevant radiation measurement applications, characteristic glow curves of samples from the clay deposits have been obtained using a Victoreen (2800M) TL reader and the TL properties subsequently examined. The variable heating rate method was used to determine the glow peak shape and intensity by estimating the activation energy or trap depth, E and the frequency factor, S. Most samples demonstrated the dependence of their glow curve on the heating rate, with the peak temperature, Tm increasing with the heating rate. These glow peaks were noted to be a complex trapping system, consisting of several overlapping first order peaks and each with different TL behaviour, except for certain samples, which showed independence of peak temperature with dose. While recommending further heating protocol to isolate each peak for the calculation of other kinetic parameters, we present an approximate 0.29–0.84 eV for E and 3.7 × 101 to 4.0 × 106 s−1 for S. Though the samples with the TL dosimetric property of increased peak intensity with increasing excitation dose could be considered for TL applications, the reduction in TL intensity must be considered for high heating rates applications. Keywords: Clay, Thermoluminescence applications, Kinetic parameters, Trapping centres