Hydrothermal synthesis and luminescence properties of YF3:Ln (Ln=Sm, Dy, Tb and Pr) nano-/microcrystals

YF3:Ln (Ln=Sm, Dy, Tb and Pr) nano-/microcrystals with uniform morphology and size have been successfully prepared by a facile, and environmentally friendly hydrothermal method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) have been used to study the morphologies and crystal structure of the products. The effects of the molar ratio of EDTA to Y3+, and chelator on the crystal growth have been investigated in detail. The time-dependent experiments have been conducted to investigate the morphology evolution process. Based on the results, a possible growth mechanism is proposed. The photoluminescence spectra at room temperature show that the as-prepared YF3:Ln (Ln=Sm, Pr, Tb and Dy) nano-/microcrystals show strong light emissions with different colors coming from different activator ions. It is noticed that morphology and size of the products have great influence on their emission intensity. Interestingly, in the YF3:Sm system, we observed the Sm2+ emission peaks when excited at 323 nm. The results reveal that some of the Sm3+ ions should have been reduced to the divalent state during the hydrothermal process.