Structural and Photoluminescence properties of nepheline-structure NaAlSiO4:Dy3+ nanophosphors

Most of the phosphors are composed of known host material with the incorporation of some percentage of an activator into the matrix. In this work Dy3+-activated NaAlSiO4 phosphors have been synthesized using sol-gel combustion technique. The phase purity, crystallite size and luminescence properties of the prepared phosphors have been investigated systematically by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) techniques. In addition, the effects of annealing temperature and Dy3+ doping concentration on the photoluminescence intensities are also investigated in detail. The X-ray diffraction pattern of the synthesized NaAlSiO4 powder can be perfectly indexed to hexagonal crystalline phase with lattice constants of a = 9.978 Å, b = 9.978 Å and c = 8.330 Å. No peaks of any other phases or impurities were observed from the XRD pattern, indicating that NaAlSiO4 crystalline phase with high purity could be obtained using the present synthesis route. The average crystallite size obtained using Scherer's equation is around 48 nm which was later confirmed by TEM. The phosphor forms the final nepheline single-phase structure at 800 °C. Under excitation with ultraviolet light, the NaAlSiO4:Dy3+ phosphor exhibited the characteristic emission of Dy3+ (4F9/2-6H15/2 and 4F9/2-6H13/2 transitions) with efficient blue and intense yellow emission at 485 nm and 574 nm, respectively. The PL characteristics of prepared phosphor shows the excitation well matched with the solid state lighting excitation sources and emission in the blue as well as yellow region of the spectrum indicating that Dy3+ activated NaAlSiO4 nanophosphors may be applicable for solid state lighting with stable physical as well as chemical properties.