Akademik Veri Yönetim Sistemi
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, cilt.341, 2025 (SCI-Expanded, Scopus)
In this study, the structural and luminescent properties of alkali-modified K7SrY2(B5O10)3 phosphors activated with Tb3+ 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 Tb3+ ions preferentially occupying Y3+ sites. Photoluminescence (PL) studies revealed intense green emission centered at 540 nm (5D4 → 7F5 transition), with maximum intensity observed at 3 wt% Tb3+, 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 Ω4 and Ω6 intensity parameters of 0.96 × 10−20 and 1.12 × 10−20 cm2, 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% Tb3+ 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:Tb3+ phosphors as efficient, color-stable, and structurally robust green-emitting components for phosphor-converted white LED and optical display devices.