Pr³⁺ Activated NaY₉Si₆O₂₆ Nanophosphors With Tunable Visible Emission and High Thermal Stability for Solid-state...

NaY₉Si₆O₂₆ nanoparticles with varying Pr³⁺ concentrations were synthesized by an alkaline hydrothermal process, yielding agglomerated spherical particles ∼55 nm in diameter with a hexagonal crystal structure. Emission spectra show that the intensity of UV 4f¹5d¹→4f² emissions is partially suppressed by efficient nonradiative relaxation, resulting in sharp visible emissions from intraconfigurational Pr³⁺ 4f² transitions. The photoluminescence intensity increases with Pr³⁺ concentration up to 0.2 mol%, where the strongest emission is observed, and then decreases at higher concentrations. Increasing the Pr³⁺ concentration also decreases the emission decay constant for both the 4f¹5d¹ and 4f² levels. These materials exhibit excellent thermal and temporal stability, retaining ~ 95% of their room-temperature emission up to 150 °C and showing no degradation over 400 min of continuous operation, underscoring their robustness. Prototype LED demonstrators fabricated with these phosphors show efficient color-tunable orange, yellow, and green emission, confirming strong compatibility with commercial LED platforms and potential for solid-state lighting.