Kaynar S Cam, Altowyan Abeer S, Aydin H, Kaynar U H, Coban M B, Hakami Jabir, Can N
Manisa Celal Bayar University, Faculty of Engineering and Natural Sciences, Physics Department, Manisa, Turkiye.
Department of Physics, College of Science, Princess Nourah Bint Abdulrahman University, P.O. Box 84428, Riyadh 11671, Saudi Arabia.
Spectrochim Acta A Mol Biomol Spectrosc. 2025 Nov 15;341:126435. doi: 10.1016/j.saa.2025.126435. Epub 2025 May 19.
In this study, the structural and luminescent properties of alkali-modified KSrY(BO) phosphors activated with Tb ions were systematically investigated for solid-state lighting and photonic applications. A combination of X-ray diffraction (XRD) with Rietveld refinement, vibrational spectroscopy (FTIR and Raman), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) confirmed that the trigonal R32 structure of the host lattice is retained upon doping and co-doping, with Tb ions preferentially occupying Y sites. Photoluminescence (PL) studies revealed intense green emission centered at 540 nm (D → F transition), with maximum intensity observed at 3 wt% Tb, beyond which concentration quenching occurred. The critical interaction distance (∼28 Å) and interaction parameter (θ ≈ 5.55) confirmed that dipole-dipole interactions govern the quenching mechanism. Co-doping with Li and Na resulted in a significant enhancement in both emission intensity and decay lifetime, with Li co-doping at 3 wt% yielding an ∼11.7-fold enhancement and increasing the average lifetime from 1.48 ms to 1.95 ms. This corresponds to a high radiative efficiency of ∼93 %, indicating effective suppression of non-radiative losses. These enhancements were attributed to improved crystallinity, suppression of non-radiative defects, and modulation of the local crystal field symmetry. Judd-Ofelt analysis of the well-resolved emission bands yielded Ω and Ω intensity parameters of 0.96 × 10 and 1.12 × 10 cm, respectively, indicating moderate asymmetry in the ligand environment. The theoretical radiative lifetime (∼1.10 ms) showed excellent agreement with experimental values, indicating high radiative efficiency with minimal non-radiative losses. CIE chromaticity coordinates reached (0.3782, 0.6081) for 3 wt% Tb and shifted toward the blue-green region (e.g., (0.2791, 0.4284) with Li), demonstrating tunable and stable green emission. This work demonstrates the potential of Li/Na co-doped KSYBO:Tb phosphors as efficient, color-stable, and structurally robust green-emitting components for phosphor-converted white LED and optical display devices.
