Red-emitting Ln_(2-x)Eu_xTe_2O_(6:RE (Ln = La, Y; RE = Sm~(3+), Gd~(3+)) phosphors prepared by the Pechini sol-gel method

摘要

La_(1.90)Eu_(0.10)TeO_6 :RE~(3+) (RE = Gd, Sm) and Y_2TeO_6:Eu~(3+)nanophosphors were prepared by the Pechini sol-gel process, using lanthanide sesquioxides and telluric acid as precursors. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectra (PL) and fluorescence lifetime were used to characterize the resulting phosphors. The results of XRD indicate that all samples crystallized completely at 1073 K and are isostructural with orthorhombic Ln_2TeO_6. The SEM study reveals that the samples have a strong tendency to form agglomerates with an average size ranging from 40 to 65 nm. The luminescence decay curves suggest for all samples a monoexponential behavior. The photoluminescence intensity and chromaticity were improved for excitation at 395 nm when the co-doping concentration reaches the 1% mol. The optimized phosphors La_(1.88)Eu_(0.10) Gd_(0.02) TeO_6 and La_(1.88)Eu_(0.10)Sm_(0.02)TeO_6, could be considered an efficient red-emitting phosphor for solid-state lighting devices based on InGaN LEDs.