Synthesis and characterisation of a new thermoluminescent phosphor CaSO 4 :Dy,Zn

A new thermoluminescent (TL) phosphor CaSO4:Dy,Zn with a major peak near 260°C and a minor peak near 165°C with potential applications in radiation dosimetry has been developed without the involvement of any acid using a simple solid-state reaction with ZnSO4 flux at 700°C sintering temperature in air. Its TL sensitivity and thermal stability are comparable to that of recrystallised CaSO4:Dy in H2SO4 acid media. Its TL response is linear in the low and medium-dose range up to 50 Gy and slightly supralinear in the 100–1000 Gy range. No saturation in its TL response was seen up to the highest gamma dose (10 kGy) studied which makes it a potential candidate for low- and high-level radiation dosimetry. Glow curve deconvolution (GCD) analysis reveals that the TL peaks exhibit a symmetry factor μg of 0.49, indicating second-order kinetics with significant re-trapping effects. An activation energy of 0.755 eV and a frequency factor of 106 s-1 were calculated via Chen’s second-order peak method. We propose that the interstitial oxygen ions formed from the thermal decomposition of SO42- ions at high temperatures (SO42-→ SO3 + O2-) in the presence of water vapour present in air serve as hole traps and the corresponding anion vacancies formed serve as electron traps in CaSO4:Dy/Dy, Zn.