Synthesis, grouping, and optical properties of REF3–KF nanocrystals

Through a polyethylene glycol (PEG) assisted hydrothermal method, the REF3–KF system materials have been synthesized. The crystalline structure and the morphology of the final products can be divided into three groups. With the molar ratio of REF3 to KF = 1:0, 1:1, and 3:1 in the final products, the samples crystallize in the hexagonal phase (REF3, RE = La, Ce, Pr, and Nd), the cubic phase (KREF4, RE = Sm, Eu, Gd, Tb, and Dy), and the tetragonal phase (KRE3F10, RE = Ho, Er, Tm, Yb, and Y), respectively. The enhanced luminescence of Tb3+ has been observed in the Ce3+/Tb3+ co-doped samples and the CeF3 sample. Acting as a probe, the Eu3+ presents different optical properties in the tetragonal phase of KY3F10 and in the cubic phase of KEuF4. In addition, the luminescent concentration effects of Tb3+ and Eu3+ have also been observed in KTbF4 and KEuF4 samples and the luminescent decay curves prove those.