Synthesis, structural and optical properties of Eu3+-doped ALnP2O7 (A = Cs, Rb, Tl; Ln = Y, Lu, Tm) pyrophosphates phosphors for solid-state lighting

A series of 2%Eu3+-activated ALnP2O7 (A = Rb, Cs, Tl; Ln = Y, Lu, Tm) pyrophosphates were synthesized via solid-state reaction method and characterized by X-ray diffraction (XRD), NMR and IR/Raman spectroscopy. Their photoluminescence properties were investigated at room temperature. The phosphors present red emitting luminescence under blue light excitation, based on f-f transitions of Eu3+ ions. Emission spectra showed that the samples had intense and prevailing red emissions at 610 nm belonging to the 5D0→7F2 electric dipole transition. One Eu3+ center was assigned according to the crystal structure and the luminescence characteristics. The decay times were measured monitoring the maximum of emission at λem = 610 nm and exciting in the 5D2 band (λexc = 464 nm). All decay curves were single exponential and lifetimes remain constant with value in integral range 3-4 ms, according to the alkali metal ion. The optical properties show that these host materials are suitable for phosphor materials for solid-state lighting applications.