UV–VUV spectroscopy of rare earth doped persistent luminescence materials

Abstract

The electronic and defect energy level structure of polycrystalline SrAl 2O 4:Eu 2+,R 3+ persistent luminescence materials were studied with thermoluminescence and UV–VUV synchrotron radiation emission and excitation spectroscopy. Theoretical calculations using the density functional theory (DFT) were carried out simultaneously with the experimental work. The experimental band gap energy ( E g) value of 6.6 eV agrees very well with the DFT value of 6.4 eV. The 4f 7 → 4f 65d 1 excitation bands of Eu 2+ were found rather similar irrespective of the R 3+ co-dopant. The trap level energy distribution depended strongly on the R 3+ co-dopant except for the shallowest trap energy above the room temperature remaining the same, however. The different processes in the mechanism of persistent luminescence from SrAl 2O 4:Eu 2+,R 3+ was constructed and discussed.