Preparation, luminescence and structural properties of rare-earth-doped RbLuS2 compounds

Rare-earth (RE = Ce, Pr, Sm, Tb) doped ternary sulfides of the general formula RbLu0.99RE0.01S2 and undoped RbLuS2 were synthesized in the form of crystalline hexagonal platelets by chemical reaction in the electric resistance furnace under the flow of hydrogen sulfide. Only a single crystalline phase of the rhombohedral lattice system (space group R anti 3 m) was detected by X-ray powder diffraction. Absorption and luminescence characteristics were measured. The band edge of RbLuS2 is found at 310 nm, and characteristic Pr3+, Sm3+ and Tb3+ 4f-4f emission lines in the visible spectral range are observed. A charge transfer transition in the Pr3+ excitation spectrum in the near UV spectral region is revealed and an efficient energy transfer from the host to the emission centers is found. The application potential for white LED or X-ray phosphors is discussed. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)