Positron lifetime studies of CaSO4: Dy thermoluminescence phosphors

Positron lifetime studies have been carried out an CaSO4:Dy phosphors with and without Teflon binder. The effect of Co-60 gamma irradiation exposure in these samples has been investigated. Unexpected CaSo(4):Dy embedded Teflon discs exhibited four lilfetime components viz. 228, 755, 3865 and 77 ps with intensities of 62%, 18%, 14% and 6% respectively. Since Teflon is used as a binder in these phosphors, the long lived components are understood to arise from this Upon radiation exposure there is a clear change in these resolved lifetime components. To understand the variation of these lifetime xomponents better, positron lifetime studies was carried out on pure CaSO4:Dy powder (without Teflon) as well as pure Teflon discs exposed to varying radiation doses. The variation of positron lifetime parameters of CaSO4:Dy powder showed systematics, ascribabic to SO4 ion formation due to gamma-ray exposure. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim