Site-selective spectroscopy of Eu3+-doped orthorhombic lanthanum and monoclinic yttrium polyphosphates

In order to study the influence in the change of the coordination environment of the cationic sites on the luminescent properties of rare-earth ions doping polyphosphates Ln(PO3)3 (Ln = La, Y) with two different structures, the time-resolved luminescence of the Eu3+ ion, used as structural probe, is reported. La(PO3)3 has an orthorhombic structure in which only one position with eight coordination is available for the cation, while Y(PO3)3 adopts the Yb(PO3)3 structure in which four slightly different octahedral sites are available for the trivalent rare-earth ion. Site-selective excitation of the 5D0 level was performed and luminescence decay times of each Eu3+ site were measured at 77 K. The spectroscopic results are discussed and correlated with the structural data.