Luminescence - structure relationships in MYP2O7:Eu3+ (M=K, Rb, Cs)

In this work we present the series of MYP2O7 phosphates doped with 3% of Eu3+ ions. All samples were prepared using wet-chemistry methods. The structural properties were characterized by XRD and Raman spectroscopy. The detailed spectroscopic properties like emission spectra at 10 and 300 K, VUV excitation spectra, luminescence kinetics and luminescence temperature quenching were performed to determine the influence of alkali metal ion. In MYP2O7 compounds, the Eu3+ ions enter two different sites - one with C1 symmetry (Y3+ sites) and one with S4 site (M+ site). All phosphors have a broad charge transfer (CT) absorption band located in the UV region (200-250 nm). The ratio between CT and 4f-4f bands is decreasing with increasing the alkali metal ion size. The mechanisms responsible of luminescence temperature quenching are thermalization of higher lying 5DJ levels, energy transfer between two nearby Eu3+ sites and non-radiative losses on defects in the host lattices.