Publication

Abstract : The growing demand for efficient, thermally stable, and colour-tunable luminescent materials has spurred extensive research on rare earth doped glasses and glass–ceramics for optoelectronic and solid-state lighting applications. Among these, Sm3+-doped phosphors are particularly attractive due to their characteristic orange-red emissions, which are suitable for generating warm white light. Achieving high structural stability, optical efficiency, and colour purity in oxide glass matrices remains challenging. Thus, the present work demonstrates that the addition of WO3 to Sm3+-doped Lithium-Strontium-Bismuth-Borate (LSBBWSm) glasses alters their properties, resulting in LSBBWSm glass–ceramics. DSC shows Tg increases from 394 °C (LSBBSm1.0) to 420 °C (LSBBWSm1.0). Structural analysis reveals that the SrWO4 crystalline phase forms in samples with a WO3 concentration of 0.5 mol%, whereas it is absent in amorphous glasses. Optical studies show E g ind decreases from 1.94 to 0.52 eV in LSBBSm glasses but increases from 2.51 to 2.71 eV in glass–ceramics. The existence of the SrWO4 phase enhances photoluminescence through efficient energy transfer, resulting in higher emission (∼3.12 × 104 W/nm) with 97.0 % colour purity and a CCT of 1605 K. Furthermore, the JO parameters (Ω2, Ω4, Ω6) decrease sharply, indicating a shift from asymmetric covalent to symmetric ionic environments with WO3. Oscillator strength drops from 6.55 × 10−6 to 0.55 × 10−6; rms deviation improves, showing increased site uniformity. Radiative transition analysis reveals that the AT reduces from 582 to 89.5 s−1 and τrad increases from 1.72 to 11.17 ms, indicating a decrease in covalency and an increase in symmetry around Sm3+-ions. The Emission cross-section and bandwidth are higher in glasses than in glass–ceramics, reflecting stronger radiative transitions in amorphous phases. Overall, WO3 enhances thermal stability, order, and luminescence through partial crystallization and phase separation, as well as energy transfer (ET). Overall, the LSBBWSm1.0 exhibits intense orange–red emission (97 % purity, CCT ≈ ∼1605 K) and longer lifetimes, making it a promising light-emitting material.