Investigative study of Mn2+ concentration on the structure, morphology and photoluminescence of sol-gel ZnAl2O4/ZnO/ SrAl2O4/Sr3Al2O6 mixed phase nanophosphor

The sol-gel technique was used to synthesize mixed phases of ZnAl2O4/ZnO/SrAl2O4/Sr3Al2O6 (ZZSS) nanophosphors. The study investigated the effect of varying the Mn2+ doping concentration on the structural, morphological and optical properties of the prepared phosphor materials. X-ray diffraction (XRD) patterns revealed that the structure of the un-doped ZZSS powder was not influenced by varying the Mn2+ concentration. Scanning electron microscopy (SEM) images showed that the morphological features of the prepared nanophosphors were influenced by the Mn2+ concentration. Transmission electron microscopy (TEM) confirmed that the prepared materials are on the nanoscale. Ultraviolet–visible (UV–vis) diffuse reflection spectroscopy showed that the band gap energy can be tuned in the range 4.78–4.92 eV. The photoluminescence (PL) results showed that the un-doped ZZSS exhibited an emission peak at 580 nm when excited at 374 nm, which is attributed to the defect centres within the ZnAl2O4 and ZnO. The doped samples showed broad emission bands at 600 nm, which were attributed to the 4T1g(G) → 6A1g(S) transitions of Mn2+ ions. The Commission International de I'Eclairage (CIE) chromaticity colour coordinates showed that the emission colour of the prepared phosphors can be tuned from yellow to orange by varying the Mn2+ concentration.