Effect of γ-radiation on TL, ESR and evaluation of trapping parameters of K2Ca(SO4)2:X (X = Dy or Eu) phosphors

Abstract

ABSTRACTThe present phosphor K2Ca(SO4)2, doped by dysprosium and europium, is synthesized by the solid-state diffusion method. The doping concentration varied from 0.1 to 0.5 mol% by weight. A phosphor is studied for X-ray powder diffraction, surface morphology analytical scanning electron microscopy and analyzed by energy-dispersive X-ray spectroscopy. The prepared phosphor K2Ca(SO4)2, doped by Dy and Eu, has been characterized for thermoluminescence (TL) glow curve, showing maximum peak temperatures at 176°C and at 200°C, respectively. TL peak intensity of K2Ca(SO4)2: Dy and Eu was compared with the standard TLD CaSO4:Dy phosphor. Both phosphors show the dose linearity ranging from 20 to 240 Gy doses of γ-rays of 60Co source at room temperature. Negligible fading has been observed when irradiated with γ-rays and stored for 60 days without taking any care from sunlight. The TL materials were used in powder forms. The linearity of ESR response with dose for powder forms of K2Ca(SO4)2: Dy was also studied using the signals at g = 2:0039 (SO3−) and at g = 2:02282 (SO4−). It was observed that the range of linearity of dose response extended between 20 and 240 Gy. Kinetic parameters have been calculated using three different methods: Chen's peak shape method, various heating rate method and initial rise method. To study the heating rate method, the glow curve was recorded for the heating rate as 1°C, 3°C, 5°C, 7°C, 9°C each time. Electron spin resonance (ESR) shows the ionic radical formation during γ-irradiation, which is responsible for TL. The effect of temperature and microwave power on the ESR signal was also studied.