On the study of the C6+ ion beam and γ-ray induced effect on structural and luminescence properties of Eu doped LiNaSO4: explanation of TSL mechanism using PL, TL and EPR study.

ABSTRACT

The present paper reports on the γ-ray and C6+ ion beam induced effect on the structural and luminescence properties of Eu doped LiNaSO4 phosphors synthesized via wet the chemical method. The material was irradiated by 60Co and 137Cs γ-rays and 75 MeV C6+ ions in a fluence range varying from 2 × 1010 to 1 × 1012 ion per cm2. The ion induced modified properties were investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) studies. The XRD and micro-Raman results confirm the loss of crystallinity and elongation of the lattice parameters after ion beam irradiation. The presence of both divalent as well as trivalent states of Eu ions at multiple sites of LiNaSO4 is observed by PL study. Irradiation of the LiNaSO4Eu phosphor with a C6+ ion beam modifies the population of the valence state of the doped rare earth Eu ion and enhances the TL sensitivity of this phosphor. The nature of the prominent TL glow curve is identical for both γ-ray and C6+ ion beam irradiated materials while additional deep trap levels appear in the latter due to the formation of several types of cation and anion vacancy. The electron paramagnetic resonance (EPR) technique also supports the presence of the Eu ion at multiple sites and provides information regarding several types of radical produced after γ-ray and C6+ ion irradiation. Finally, a mechanism is presented for the thermally stimulated luminescence phenomenon on the basis of our observed results from the PL, TL and EPR studies. The reason behind ion beam irradiation induced modification of the TL properties and enhancement of luminescence intensity is also explained in this report.