Effect of 14-MeV neutrons on strontium–aluminate-based long-lasting phosphor

Long-lasting phosphor (LLP) emits photons for a long period of time after the cessation of irradiation without external excitation. LLP exhibits not only a long-lasting emission but also strong fluorescence. The fluorescence and long-lasting emission properties of two types of strontium-aluminate-based LLPs – SrAl2O4:Eu2+, Dy3+ and Sr4Al14O25:Eu2+, Dy3+ – are examined under 14-MeV neutron irradiation. The fluorescent spectra of the LLPs have characteristic peaks due to their dopants and the fluorescent intensity of Sr4Al14O25:Eu2+, Dy3+ shows good radiation resistance for the neutrons, with a slight change after increasing the irradiation fluence up to 1019 n/m2. Long-lasting emissions are exhibited after neutron irradiation, and the emission spectra have one peak due to Eu2+. A peak due to Dy3+ ends immediately when the irradiation is stopped. Further, it is found that there is an optimum neutron fluence at which the longest decay time is obtained.