Thermoluminescence study of K2Ca2(SO4)3:Cu nanophosphor for gamma ray dosimetry

Nanocrystalline K2Ca2(SO4)3:Cu was synthesized by chemical coprecipitation method and annealed at 700 °C. XRD of this sample shows the cubic structure and the crystallite size ∼20 nm. The same was also confirmed with TEM and shows the formation of nanorods of quite uniform in shape having diameter ∼20 nm and length in the range of 200 nm. The FTIR spectrum exhibits the bands corresponding to sulphate anions around 1015 and 600 cm−1. These samples were irradiated with gamma radiation for the dose varying from 0.1 Gy to 50 kGy and their TL characteristics have been studied. The glow curves of the pristine samples consists of two peaks one at around 139 °C while another one around 185 °C while the glow curve of samples annealed at 700 °C show a major peak at around 165 °C and other two peaks of low intensity at around 300 °C and 390 °C. The change in glow curve structures around 700 °C is due to the phase transition (from orthorhombic P212121to cubic P213 phase). The energy levels (trapping levels) get reorganized due to phase transition after the phase transition temperature (260 °C) and remain the same at higher temperatures (700 °C). TL dose response shows a linear behavior up to 1 kGy and further saturates with increase in the dose. Simple glow curve structure, easy method of synthesis, linear dose response and low fading make the nanocrystalline phosphor a good candidate for radiation dosimetry and especially, for the estimation of high doses of gamma rays where the microcrystalline phosphors generally saturate.