Structural, thermal, and luminescence kinetics of Sr4Nb2O9 phosphor doped with Dy3+ ions for cool w-LED applications

In this study, a series of white-light-emitting strontium niobium oxide {Sr 4 Nb 2 O 9 : x Dy 3+ ( x = 0.01, 0.03, 0.05, 0.07, and 0.10 mol)} phosphors were synthesized via solid-state reaction approach and analyzed by using XRD, SEM, diffuse reflectance, photoluminescence (PL), and temperature-dependent PL (TDPL) spectroscopy. The cubic structure of Sr 4 Nb 2 O 9 microparticles was identified by inspecting the diffraction pattern of the freshly generated phosphor. The formation of heterogeneous microstructures, including some aggregation, was seen in the SEM image of Sr 4 Nb 2 O 9 phosphor. Diffuse reflectance and PL were examined for varying dopant ions concentration to explore the optical luminescence characteristics of Sr 4 Nb 2 O 9 phosphor materials. Further, absorption spectra were obtained by using the diffuse reflectance spectra. The PL spectra of as-prepared phosphor exhibit two peaks at 483 nm and 580 nm, corresponding to the 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions, respectively. By correlating absorption and PL spectra, Judd oflet parameters were evaluated. The intensity of PL spectra of as-prepared phosphors increases up to 7 mol% and beyond that, it decreases. It is also affirmed that the PL intensity is maximum for the 7 mol% Dy 3+ ions-doped Sr 4 Nb 2 O 9 sample. The PL lifetime of the level 4 F 9/2 was evaluated by exciting the Dy 3+ ions at 350 nm. By applying the Inokuti-Hirayama model to decay curves, the energy transfer process was explored. The CIE chromaticity coordinates of all the as-prepared phosphors lie in the white zone of the chromaticity diagram. The PL intensity remains 71% at 200 °C that of at room temperature, indicating the phosphor's exceptional thermal stability. From the aforesaid findings, it is observed that Sr 4 Nb 2 O 9 : Dy 3+ phosphor is a promising choice for lighting and luminescent devices.