Red-emitting Ln2−xEuxTe2O6:RE (Ln = La, Y; RE = Sm3+, Gd3+) phosphors prepared by the Pechini sol–gel method

La1.90Eu0.10TeO6:RE3+ (RE = Gd, Sm) and Y2TeO6:Eu3+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 Ln2TeO6. 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 phosphorsLa1.88Eu0.10Gd0.02TeO6and La1.88Eu0.10Sm0.02TeO6, could be considered an efficient red-emitting phosphor for solid-state lighting devices based on InGaN LEDs.

Research highlights
► Synthesis of nanocrystalline phosphors by Pechini sol–gel methods.
► Co-doped Gd3+ or Sm3+ enhance the emission efficiency at 395 nm of La1.90Eu0.1TeO6 when some Eu3+ ions are replaced by Gd3+ or Sm3+ cations.
► The optimized phosphors have been obtained when the Gd3+ or Sm3+ concentration reaches 1 mol% in the host structure.