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- Neodymium activated strontium zinc aluminate (Sr3ZnAl2O7:x%Nd3+) nanophosphor was synthesized using the sol-gel technique whereby the Nd3+ concentration was varied in the range 0≤x≤2. The effect of Nd3+ concentration on the structure, particle morphology and photoluminescence properties of Sr3ZnAl2O7 were in vestigated. The X-ray diffraction (XRD) results revealed that all samples resembled the mixture of both ZnAl2O4 and Sr3Al2O6 cubic structures. Nd3+ doping influenced the crystallite sizes of the prepared phosphor materials. The energy dispersive X-ray spectroscopy (EDS) results confirmed the presence of all expected elements in the composition. Scanning electron microscopy (SEM) revealed that as the Nd3+ concentration increased the surface morphology changed to smooth mountain-like structures. The ultraviolet–visible (UV–Vis) diffuse reflection spectroscopy showed that the band gap of Sr3ZnAl2O7 can be tuned from 2.74 to 2.95 eV by increasing the Nd3+ concentration. When the host is excited above the bandgap (374nm), broad emission attributed to defects occurs with the maximum near 585nm. Doped samples excited in this manner do not exhibit additional luminescence due to the Nd3+ ions, but in contrast there is a small dip in the defect emission band near 585nm due to absorption attributed to Nd3+ ions. Characteristic infrared emissions of Nd3+ ions at 885, 1064 and 1340nm were observed by directly exciting the Nd3+ ions at 585 nm (4I9/2→5G5/2+2G7/2) and were attributed to 4F3/ 2 →4I9/2, 4I11/2 and 4I13/2 transitions, respectively. The Commission Internationale de l’Eclairage (CIE) co ordinates results showed that the orange emission colour is from the host.
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- MgAl2O4:x% Gd3+ (0 ≤ x ≤ 3) nano-powders were prepared via the citrate sol–gel method. The x-ray diffraction confirmed that the prepared samples consist of the cubic crystalline structures. There was no secondary phases due to Gd3+ doping. The estimated average grain sizes were found to be in the order of 8 nm. Energy dispersive spectroscopy showed the presence of the anticipated elements (Mg, Al, O, and Gd). The scanning electron microscope results revealed that the morphology of the samples is influenced by the Gd3+ concentration. Transmission electron microscopy analysis revealed that the prepared samples are in the nano-scale range. Selected area electron diffraction patterns indicated highly crystalline structure and the intensities of the bright spots varied with Gd3+ concentration. Photoluminescence studies showed two distinct emission peaks at 385 and 392 nm, which are certainly attributed to the defects levels located at different positions on the host material (MgAl2O4). The emission peaks located at 315 and 628 nm were respectively attributed to the 6P7/2 → 8S7/2 and 6G7/2 → 6P3/2 transitions in the Gd3+ ion. The luminescence intensity of the 388 nm decreased with an increase in the Gd3+ concentration. Commission Internationale de l’Eclairage (CIE) coordinates showed that the violet emission color from host cannot be tuned by varying Gd3+ concentration.
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