Orange-red Emitting KSr₆ScSi₄O₁₆:Sm³⁺ Phosphors with Exceptional Thermal Stability for WLED Applications

To address the insufficient color performance in contemporary solid-state lighting, a novel series of orange-red-emitting KSr₆ScSi₄O₁₆:Sm³⁺ (KSSSO: Sm³⁺) phosphors was synthesized employing conventional solid-state synthesis. Comprehensive characterization encompassing phase analysis, luminescence properties, and thermal behavior was performed on the temperature-optimized material. Under 402 nm excitation, the Sm³⁺-activated phosphors exhibit four distinct emission bands centered at 562 nm, 599 nm, 645 nm, and 708 nm, corresponding to the characteristic ⁴G_5/2→⁶H_5/2, ⁴G_5/2→⁶H_7/2, ⁴G_5/2→⁶H_9/2, and ⁴G_5/2→⁶H_11/2 transitions of Sm³⁺ ions, respectively. Notably, the 599 nm emission (⁴G_5/2→⁶H_7/2 transition) dominates the luminescence spectrum, resulting in an orange-red emission color for the phosphor. The ideal Sm³⁺ concentration was determined to be 2 mol%, exceeding this level induces concentration quenching primarily via dipole-dipole interactions. All synthesized samples demonstrate exceptional color purity exceeding 98%. The phosphor exhibits the remarkable property of very low thermal quenching, demonstrating exceptional thermal stability with a retention intensity of 99.58% even at an elevated temperature of 420 K. A phosphor-converted white light-emitting diode (pc-WLED) was fabricated via a tri-color blending approach, demonstrating an ideal correlated color temperature (CCT) of 5638 K and an excellent color rendering index (R_a = 92.8). These outstanding photometric properties confirm the exceptional suitability of the phosphor for high-performance WLEDs.