Observation of photoluminescence and radioluminescence in Eu and Mn doped NaMgF3 nanoparticles

Eu and Mn doped NaMgF3 nanoparticles have been made using a reverse micro-emulsion method. All nanoparticles show Mn2+, Eu2+, or Eu3+ photoluminescence (PL) and radioluminescence (RL) as well as PL from an unidentified defect that does not display RL. The Mn2+ sample contains PL emissions from distorted and undistorted Mn2+ sites but the RL is dominated by the undistorted Mn2+ site. The PL lifetime is lowest for the highest Eu concentration. This may be due to energy transfer from Eu3+ sites in the core to Eu3+ sites near the surface followed by non-radiative decay. However, the possibility that Eu3+ substitution leads to more non-radiative decay sites in the core cannot be excluded. The internal quantum efficiency at 270 K is highest for the NaMgF3:1% Eu nanoparticles (76%). The RL is independent of dose after an initial ∼10 kGy irradiation.