Investigation of Structure and Performance of Cerium-Doped Lanthanum Fluoride Nanocrystals for Scintillators

The synthesis and characterization of cerium-doped lanthanum fluoride (La_(1−x)Ce_xF₃) nanocrystals have been carried out. The surfaces of La_(1−x)Ce_xF₃ nanocrystals were modified with oleic acid using the co-precipitation technique, and then doped with cerium with various mole fractions (x) = 0.05, 0.10, 0.15, 0.20, and 0.25. The nanocrystals produced were characterized for their crystal structure using x-ray diffraction (XRD), their morphology by transmission electron microscopy (TEM), their functional group identification using Fourier-transform infrared (FTIR), and Raman spectroscopy, and their photoluminescence behavior using photoluminescence (PL) spectroscopy. Detailed investigations revealed that, based on the XRD data and TEM images, La_(1−x)Ce_xF₃ exhibits trigonal-structured nanocrystals with the symmetry space group P-3c1. Among the samples, La_0.75Ce_0.25F₃ exhibited the sharpest PL peak. The PL spectra for La_0.75Ce_0.25F₃ nanocrystals excited at 370 nm and showed an intense emission peak at 495 nm with a lifetime τ = 1.523 × 10⁻¹⁰ s. This emission was assigned to the 5d → 4f (²F_5/2 and ²F_7/2) transitions of Ce³⁺ energy levels, indicating a luminescence center mechanism. These results indicate that the synthesized La_0.75Ce_0.25F₃ is a promising phosphor material for detector scintillators.