“…Trivalent lanthanides, and in particular Eu 3+ , have also been used as luminescent local probes to analyze the crystalline structure and local site symmetry in diverse inorganic materials [20][21][22][23]. Das et al [24] use Eu 3+ to explore Na 0.1 Sr 9.8 Eu 0.1 (PO 4 ) 6 F 2 both as a potential phosphor material and host for radioactive waste immobilization.…”