Oxide glass formers extending persistent luminescence in Eu and Dy co-doped strontium aluminates

Abstract

Recent work has shown that the incorporation of electrically charged, non-bridging oxygen (NBO) species into Eu and Dy co-doped Sr4Al14O25 (S4A7ED) crystal structure, in the form of Bo2O-, induces the clustering of divalent Eu and trivalent Dy, which is manifested as persistent luminescence (PersiL). Because other ceramic compounds exhibiting persistent luminescence also contain Si, P, and Zr, we evaluated other oxide glass forming cations-Si, P, Zr and V-for extending PersiL in S4A7ED. To understand the structural changes that these cations imparted to the atomic arrangements inside the S4A7ED crystal structure, we applied FTIR and micro-Raman spectroscopy to analyze the impact of charged NBOs. Raman shifts were revealed in Si-doped S4A7ED exhibiting PersiL at 1077 cm-1, corresponding to vibrations involving SiO4 tetrahedra with 2 bridging oxygens (BOs) and 2 NBOs and at 1107 cm-1, corresponding to vibrations involving SiO4 tetrahedra with 3 BOs and 1 NBOs. Raman shifts were also observed in P-doped S4A7ED exhibiting PersiL at 1070 cm-1, corresponding to PO4 tetrahedra with 1 BO and 3 NBOs, and at 700 cm-1, corresponding to PO4 tetrahedra with 2 BOs and 2 NBOs. These results suggest that PersiL extension in S4A7ED compounds, Pechini-processed with oxides of Si, P, Zr, and V, is correlated to structural changes from the incorporation of polyanions with NBOs, although the presence of a BO in the cation polyhedra is also essential.