Structural and optical properties of langbeinite-related red-emitting K(2)Sc(2)(MoO(4))(PO(4))(2):Eu phosphors

The concentration series of langbeinite-related solid solutions K(2)Sc(2)(MoO(4))(PO(4))(2):xEu (x = 0.1, 0.2, 0.6, 0.8, and 1.0 mol%) has been prepared via a solid state route and the effects of europium content on the phase composition, morphology, crystal structure and luminescence properties have been studied by scanning electron microscopy, X-ray powder diffraction, UV-vis, IR and luminescence spectroscopy. The band gap values have been estimated from UV-vis spectra and are in the range of 3.7–3.8 eV for all concentrations studied. The electronic band structure calculations have shown that Sc d, Mo d and O(phos) p states dominate in the band edge region and determine the optical transitions in the K(2)Sc(2)(MoO(4))(PO(4))(2) host. The photoluminescence (PL) spectra, intensity and decay time dependences on the Eu(3+) concentration revealed complex behavior of europium-containing emitting centers. The PL characteristics indicated the presence of at least two types of luminescence centers. One of them (Eu(K)) is shown to be formed by the Eu(3+) ion located within K sites, while the other one is formed by the Eu(3+) ions that reside in Sc sites (Eu(Sc)). The luminescence color coordinates calculated for K(2)Sc(2)(MoO(4))(PO(4))(2):xEu indicated that these ceramics can be potential candidates for UV-based lighting applications as efficient red phosphors.