The enhanced and color-tunable photoluminescence of Eu3+/V5+ co-doped Gd2Ti2O7 nanocrystals

Eu3+-doped and Eu3+/V5+ co-doped pyrochlore-type gadolinium dititanate (Gd2Ti2O7) nanoparticles were synthesized by sol-gel method. X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence (PL) spectroscopy were employed to characterize the phosphors obtained, respectively. In Eu3+-doped Gd2Ti2O7 nanocrystals, only the bright orange emissions which can be assigned to the 5D0-7F1 magnetic dipole transition of Eu3+ had been noticeable because of the existence of inversion symmetry for Gd3+ sites occupied by Eu3+ ions. Interestingly, upon co-doping V5+ in Gd2Ti2O7:Eu3+ phosphor, the bright red emissions which can be assigned to the 5D0-7F2 electric dipole transition of Eu3+ were observed, due to the absence of inversion symmetry induced by the steric effect and charge effect. The ratio of the intensity of red luminescence to that of orange luminescence increased with increasing the doping concentration of V5+, which is encouraging for its application in optical devices.