Color tuning and white light emission in a single-phased La2Ti2O7:Pr3+, Tb3+ phosphor

Abstract

Color-tunable and white-emitting Pr3+ and Tb3+ co-doped La2Ti2O7 phosphors were prepared via a molten salt method. The as-synthesized samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflection spectra (DRS), photoluminescence spectra (PL), fluorescence decay curves and temperature-dependent photoluminescence spectra in detail. The La2Ti2O7:Pr3+, Tb3+ phosphors are uniform square-like nanobelt and the band gap of La2Ti2O7 host is calculated to be 3.83 eV by DRS. Under 296 nm wavelength UV excitation, the La2Ti2O7:Pr3+ compounds show strong red emission with peaking at 612 nm. Four typical emission lines of Tb3+ ions are observed from the region of 480–650 nm in La2Ti2O7:Tb3+ phosphors, and the strongest green emission peak is located at 545 nm. What's more, the emission color of La2Ti2O7:0.001Pr3+, 0.010 Tb3+ can be tuned from white (0.3274, 0.3379) to pink (0.4777, 0.2890) upon the excitation from 290 to 348 nm and the emission color of La2Ti2O7:0.001Pr3+, xTb3+ can be also tuned from white to green by changing the concentration of Tb3+. The La2Ti2O7:Pr3+, Tb3+ phosphors have the poor temperature dependence, resulting from the value of ΔR (the displacement between parabolas of the intervalence charge transfer states and ground states) for Tb3+ and Pr3+ both are larger. The results indicate that La2Ti2O7:Pr3+, Tb3+ phosphors could be a promising tunable and white light emission phosphor.