Thermoluminescence of kunzite: A study of kinetic processes and dosimetry characteristics F.O. Ogundare a,⇑ , M.A. Alatishe a , M.L. Chithambo b , G. Costin c a Department of Physics, University of Ibadan, Ibadan, Nigeria b Department of Physics and Electronics, Rhodes University, PO BOX 94, Grahamstown 6140, South Africa c Department of Earth Science, Rice University, Houston, TX 77005, USA article info Article history: Received 17 December 2015 Received in revised form 10 February 2016 Accepted 25 February 2016 Keywords: Thermoluminescence Kunzite Thermal quenching Luminescence dating Dosimetry abstract Since the use of natural minerals for dating and dose reconstruction using luminescence techniques is well-established and always of interest, we present thermoluminescence characteristics of kunzite, a gem variety of spodumene. The chemical composition of the sample was determined using an Electron Probe MicroAnalyzer to be (Li 0.996 Na 0.009 Mn 0.006 ) P = 1.016 (Al 0.981 Cr 0.003 Fe 2+ 0.001 ) P = 0.995 [(Si 1.993 Al 0.008 ) P = 2.000 O 6 ]. Thermoluminescence glow curves measured at 0.5 K/s after laboratory irradiation consist of three prominent peaks at 338 K (labelled as peak I), 454 K (peak II) and 681 K (peak III). The dose response of these three peaks is linear in the range 20–308 Gy studied. The position of each of the peaks is inde- pendent of dose, an archetypical feature of first order behaviour. However, detailed kinetic analyses showed that in fact, the peaks are not subject to first order kinetics. Each of the three peaks is affected by thermal quenching with an associated activation energy of thermal quenching estimated to be 0.70, 1.35 and 0.54 eV for peaks I, II and III respectively. In terms of dosimetry use, only peak III was found to be reliable for possible use in luminescence dating and dose reconstruction. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction Thermoluminescence (TL) and optically stimulated lumines- cence are widely used for retrospective dosimetry and archaeolog- ical dating [1]. Although the number of natural materials that can be used in such applications is obviously very large, much work has concentrated only on quartz [2,3] and feldspar [4]. There have however been a number of valuable studies on materials with which humans have direct and continuous contact such as busi- ness cards and buttons [5], prosthetics [6] or resistors from cell- phones [7]. Kunzite, the material studied in this report, is a photochromic variety of spodumene. It is in the context of it as a gem material that its dosimetry features reported in this work should be understood. Kunzite, which occurs with a pink or lilac hue, is one of the three varieties of spodumene (LiAlSi 2 O 6 ) . This is a natural lithium aluminosilicate mineral with luminescence characteristics that makes it amenable for application in luminescence dose recon- struction and dating [8]. Apart from being one of the principal sources of Li and the most important Li mineral in pegmatites [9], kunzite is an important source of lithium for use in various materials including ceramics, mobile phone and automotive bat- teries, production of lithium carbonate, and as a fluxing agent. Because of its attractive colouration, kunzite is considered semi- precious and is used in jewellery and even with fabrics for shoes and handbags. These wide applications and varied properties make kunzite a desirable mineral that should be investigated for applica- tion in radiation dosimetry. Reports of luminescence from kunzite are rare with only a few devoted to its thermoluminescence. Claffy [10] examined the chemical composition, luminescence (phosphorescence and fluorescence) and tenebrescence of spodumene from different localities. Ito and Isotani [11] and Isotani et al. [12] reported the optical absorption spectra of irradiated and heat-treated spodumene in both the visible and ultraviolet range. Lipatov et al. [13] also reported the spectral characteristics of pulsed cathodoluminescence and pulsed photoluminescence of natural spodumene from Russia. All the studies indicated that Mn 2+ impurities play a significant role in the luminescence emission from the phosphor. http://dx.doi.org/10.1016/j.nimb.2016.02.059 0168-583X/Ó 2016 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: ogun_dare@yahoo.com (F.O. Ogundare). Nuclear Instruments and Methods in Physics Research B 373 (2016) 44–51 Contents lists available at ScienceDirect Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb