Effects of annealing temperature on the structure and photoluminescence properties of the ZnO/ZnAl2O4/Ca5Al6O14/Ca3Al4ZnO10:0.1% Ce3+ mixed-phases nanophosphor prepared by citrate sol–gel process

Mixed-phases of the undoped ZnAl2O4/ZnO/Ca5Al6O14 (ZZC) and Ce3+ doped ZnAl2O4/ZnO/Ca5Al6O14/Ca3Al4ZnO10 (ZZCC:0.1% Ce3+) were successfully prepared using the sol–gel method. The 0.1% Ce3+ concentration was kept constant while the annealing temperature (Ta) was varied from 500 to 1300 °C. X-ray diffraction (XRD) results showed that the prepared materials consist of the mixture of the cubic (ZnAl2O4), hexagonal wurtzite (ZnO) and orthorhombic (Ca5Al6O14 and Ca3Al4ZnO10) crystal structures, which highly depends on the Ta. 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 Ta 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 Ce3+ transition. Optimum photoluminescence intensity was observed at the Ta = 600 °C. The commission Internationale de I’Eclairage coordinates (CIE) showed that the emission colour could be tuned by varying the Ta.