Highly uniform YF3:Ln3+ (Ln = Ce3+, Tb3+) walnut-like microcrystals: Hydrothermal synthesis and luminescent properties

Uniform and well-crystallized YF3 walnut-like microcrystals were prepared by a facile one-step hydrothermal synthesis. The crystalline phase, size, morphology, and luminescence properties were characterized using powder X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE). The results revealed that the existence of Ce3+ (sensitizer) can dramatically enhance green emission centered at 545 nm of Tb3+ (activator) in codoped samples due to an efficient energy transfer from Ce3+ to Tb3+. The critical energy transfer distance between Ce3+ and Tb3+ was also calculated by methods of concentration quenching and spectral overlapping. Experimental analysis and theoretical calculations indicated that the dipole–dipole interaction should be the dominant mechanism for the Ce3+–Tb3+ energy transfer.