Luminescence and ESR Studies of CaS:Dy Phosphor

CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoluminescence. Defect centres formed in CaS:Dy are studied using the technique of electron spin resonance. The thermoluminescence glow curve shows peaks at around 117°C and 345°C. Irradiated CaS:Dy exhibits ESR lines due to defect centres. The thermal annealing behaviour of one of the defect centres appears to correlate with the TL peaks at 117°C and 345°C. This centre is characterized by an isotropic g-value of 2.0035 and is assigned to an F⁺ centre.