Preparation of La-Dy-CeO2 ternary compound: Examination of photocatalytic and photoluminescence properties

This study investigated the photochemical changes of cerium oxide (CeO2) with the contribution of rare earth ions. Lanthanum (La) and Dysprosium (Dy) were added to the CeO2 crystal structure simultaneously via citric acid sol-gel synthesis. Following synthesis, the sintering temperatures were chosen as 800 and 1000 °C. Results of X-ray diffraction (XRD) analysis showed that the doped and undoped CeO2 compounds exhibited a cubic phase. The surface morphology of the samples was examined by scanning electron microscopy (SEM). The particle sizes varied in the range of 90−150 nm and the composite elements were observed to maintain the stoichiometric ratio. Compound impurity control was performed using energy dispersive X-ray (EDX). Lattice changes in the compounds were revealed via Raman spectroscopy, which indicated that the La and Dy had caused changes in the CeO2 symmetry. The photocatalytic behavior of the compounds was investigated using methylene blue degradation. Optical band gaps were calculated and the La and Dy were found to have narrow band spacing. The band gap of the Ce0.85La0.10Dy0.05O2 compound sintered at 1000 °C was 1.63 eV, the rate constant was 9.4 * 10−3 min−1, and the degradation efficiency at 100 min was calculated as 60 %. The photoluminescence spectra exhibited four bands centered at 435, 532, 565, and 610 nm. The emission band at 565 nm was attributed to the transition from the 4F9/2 to the 6H13/2state, whereas the emission bands peaking at 435 nm, 532 nm, and 610 nm can be explained by the intrinsic luminescence of the host lattice.