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Undoped ZnAl2O4/ZnO mixed phases (hereafter called ZZ) and Sm3+ doped ZZ nanopowders were synthesized by precipitation method and annealed at 750 ℃ for 3.5 h. This study aimed to investigate the effect of varying the Sm3+ concentration on the ZZ mixed phases nanopowders. The effect of Sm3+ on the structure, morphology, optical and luminescence properties were studied in detail. The X-ray diffraction (XRD) analysis confirmed that the samples have mixed phases of face-centred cubic and a hexagonal wurtzite structure from ZnAl2O4 and ZnO, respectively. At 3.0% Sm3+ concentration, XRD peaks changed from a mixed phase of ZZ to a singled phase ZnO. It was also found that the estimated crystallite size for ZnAl2O4 decreased with an increase in Sm3+ concentration and increased for ZnO. Scanning electron microscopy (SEM) revealed that an increase in Sm3+ concentration influenced the morphology from clustered spherical shapes to aggregated inhomogeneous structures. Energy dispersive x-ray spectroscopy (EDS) analysis confirmed the anticipated elementary composition. Ultraviolet-visible (UV) showed a decrease in bandgap compared to the ZZ. Photoluminescence (PL) analysis indicated that doping with Sm3+ induced defects within ZZ. The emission peaks observed around 382, 501, 613, 680, 785 and 835 nm are from the undoped material. There are limited reports on the 835 nm peak. The emission peaks at 560, 610, 658 and 698 nm corresponds to the sharp emissions of Sm3+. The Commision Internationale de L'Eclairage (CIE) colour chromaticity diagram showed emission colour tuned from violet → orange → white → orange by varying the Sm3+ concentration in ZZ.
Keywords: ZnAl2O4/ZnO, phase transformation, Samarium, singled phase.
