Energy transfer process in CaSO4:Tb,Ce phosphor

Thermoluminescence (TL) and photoluminescence studies have been carried out on CaSO4:Tb, CaSO4:Ce and CaSO4:Tb,Ce phosphors with the aim of studying energy transfer process in the CaSO4:Tb,Ce phosphor. CaSO4:Tb,Ce shows TL peaks at 150, 220, 320 and 400°C. Changes in Tb and Ce concentrations influence the relative heights of these glow peaks. Co-doping with 0.1 mol% of Ce in CaSO4:Tb enhances the sensitivity of 320oC TL peak by a factor of 15. Fluorescence results show that there is energy transfer from Ce to Tb ion. The defect centres formed in CaSO4:Tb,Ce phosphor are studied using electron spin resonance technique. The 320oC glow peak correlates with a centre (SO3−radical) with g-values: g||=2.0061 and g⊥=2.0026.