Study of structural and luminescent characteristics of novel color tunable blue-green Tb~(3+)-doped Na_3Y(PO_4)_2 nanoparticles for NUV-based WLEDs

摘要

Nanoscaled Tb~(3+)-doped Na_3Y(PO_4)_2 phosphors with magnificent color domain have been synthesized via urea-assisted solution combustion process and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and photolumines-cence (PL) studies. The Rietveld refinement was executed on the XRD data of Na_3Y_(0.96)Tb_(0.04)(PO_4)_2 and showed that the samples were crystallized into a single-phase orthorhombic lattice with space group Pca21(29). Additionally, TEM micrograph, and Debye-Scherrer equation analysis of Na_3Y_(0.96)Tb_(0.04)(PO_4)_2 revealed the occurrence of nanosized phosphor particles in a size domain lying between 25 and 40 nm. Furthermore, to forecast PL of the as-synthesized nanophosphors, their PL emission and excitation spectra were recorded at a wavelength of 374 and 545 nm, respectively. Under the excitation wavelength (at λ_(ex) = 374 nm), the PL emission spectra of Na_3Y_((1-x))Tb_x(PO_4)_2 (where x = 0.015-0.06 mol) exhibited the appearance of most intense peak at 545 nm corresponding to ~5D_4→~7F_5 (magnetic dipole allowed) transition. Critical concentration for the nanophosphors series was found to be x = 0.04 (4 mol%) and also the critical transfer distance (R_c) was determined to be 21 A which ultimately depicted the energy transfer mechanism majorly responsible for concentration quenching as quadrupole-quadrupole interactions. Quantum efficiency for the whole series was calculated and intrinsic lifetime (4.03 ms) was also determined using Auzel's fitting parameters. CIE coordinates (x, y) for series Na_3Y_(1-x)Tb_x(PO_4)_2 (where x = 0.015-0.05 mol) were also evaluated by MATLAB software and their results showed that the color tunability from bluish to greenish can be achieved simply by changing the concentration of dopant ions. All the as-obtained results suggest that Na_3Y_(1-x)(PO_4)_2:xTb~(3+) nanophosphors may show their potential usability as a blue-green component in Near-Ultraviolet (NUV)-based WLEDs, and display gadgets.