Effects of annealing temperature on the structure and photoluminescence properties of the ZnO/ZnAl_2O_4/Ca_5Al_6O_(14)/Ca_3Al_4ZnO_(10):0.1% Ce~(3+) mixed-phases nanophosphor prepared by citrate sol-gel process

摘要

Mixed-phases of the undoped ZnAl_2O_4/ZnO/Ca_5Al_6O_(14) (ZZC) and Ce~(3+) doped ZnAl_2O_4/ZnO/Ca_5Al_6O_(14)/Ca_3Al_4ZnO_(10) (ZZCC:0.1%Ce~(3+)) were successfully prepared using the sol-gel method. The 0.1% Ce~(3+) concentration was kept constant while the annealing temperature (T_a) was varied from 500 to 1300 °C. X-ray diffraction (XRD) results showed that the prepared materials consist of the mixture of the cubic (ZnAl_2O_4), hexagonal wurtzite (ZnO) and orthorhombic (Ca_5Al_6O_(14) and Ca_3Al_4ZnO_(10)) crystal structures, which highly depends on the T_a. Energy dispersive x-ray spectroscopy (EDS) analysis confirmed the presence of all the expected elementary compositions. Scanning electron microscopy (SEM) results showed that varying the T_a does not influence the morphology of the prepared nanophosphor material. Transmission electron microscopy confirmed that the prepared powders were in the nanoscale region. The photoluminescence (PL) results showed emission peaks located at 409, 488, 545, 589, 615, 695 and 785 nm, which were attributed to the intrinsic defects within ZZC mixed phases. There was no emission observed from the Ce~(3+) transition. Optimum photoluminescence intensity was observed at the T_a = 600 °C. The commission Internationale de I'Eclairage coordinates (CIE) showed that the emission colour could be tuned by varying the T_a.