Site selective substitution of Eu3+ and its effects on structural and luminescent properties of monoclinic YP5O14 pentaphosphate

Y1-xEuxP5O14 (0 < x ≤ 1) pentaphosphate polycrystallines were synthesized by solid state reaction and the effects of Eu3+ content on the structure and luminescent properties were investigated. X-ray diffraction and Infrared spectroscopy studies revealed a sequence of the composition-driven structural phase transitions C2/c → P21/c; occur at the lower Eu3+ concentration (below 40 mol% of Eu3+ doping). The spectroscopic properties in UV-excitable range of the doped compounds were investigated. Site-selective laser excitation in the 5D2 level of Eu3+ ion was performed and luminescence decay times were measured at 30 K for 5 and 10%Eu3+ -doped YP5O14 samples. The obtained results clearly show that the Eu3+ ions are distributed over two distinct crystallographic sites. Careful analysis of the main 5D2→7FJ (J = 0, 2) transitions revealed a good agreement between the observed and expected components numbers for the local symmetry predicated upon the crystal structure of the monoclinic YP5O14. The spectroscopic results are discussed and correlated with the structural data.