Correlated ESR, PL and TL studies on K3Na(SO4)2 : Eu thermoluminescence dosimetry phosphor

Strong thermoluminescence (TL) was observed in K3Na(SO4)2 : Eu phosphor in the Eu doped K2SO4–Na2SO4 system. The defect centres formed in this TL phosphor are studied using the technique of electron spin resonance. Two glow peaks at 423 and 475 K are observed in K3Na(SO4)2 : Eu phosphor prepared by the melt method. The peak 475 K is shown to be at least thrice as sensitive as the conventional CaSO4 : Dy phosphor used in the TL dosimetry of ionizing radiations. Two centres, assigned to SO4− and SO3−, are observed at room temperature in the melt prepared phosphor. Step annealing measurements showed a connection between these centres and the observed TL glow peaks. Three TL glow peaks at 360, 423 and 453 K are observed in the K3Na(SO4)2 : Eu phosphor prepared by the evaporation method. A SO4− centre and two different SO4− centres are observed in this phosphor. TL and photoluminescence emission spectra indicate that the europium ion is in the divalent state in K3Na(SO4)2 : Eu phosphor.