Influence of Tb3+ doping on the structural and down-conversion luminescence behaviour of SrLaAlO4 nanophosphor

Different concentrations of terbium activated strontium lanthanum aluminates (SLA:Tb3+) were synthesized by adopting urea-aided solution combustion route at the sintering temperature of 1330 degrees C. XRD based Rietveld refinement technique confirms that SLA:Tb3+ nanophosphors have a perovskite-based structure with I4/mmm space group symmetry. Morphological information is collected on scanning and transmission electron microscopes (SEM & TEM) however, the energy dispersive mode of SEM (EDS) provides an idea about the distribution of existing elements throughout the host lattice. The band-gap studies for SrLaAlO4 (5.00 eV) and SrLa0.98Tb0.02AlO4 (4.50 eV) compositions are carried out using diffuse reflectance (DR) measurements via Kubelka-Munk relations. The down-converted photoluminescence (PL) studies reveal that an intense green emission is obtained at 545 nm due to D-5(4) -> F-7(5) transition under 279 nm UV-excitation. Further, Dexter's theory helps in explaining the concentration quenching mechanism in SLA:xTb(3+) nanocrystals (d-q interactions, s = 8.13). Moreover, the radiative lifetime (1.17 ms), non-radiative rates (194.28 s(-1)) and quantum efficiencies (81%) of D-5(4) term are calculated using Auzel's model. Finally, the Commission International de I'Eclairage (CIE) color coordinates confirm the emission in green region; which approves the role of Tb3+-activated SLA nanophosphors as a green component in RGB based white light emitting diodes (WLEDs).