High-color-purity orange luminescence from Sm³⁺-doped NaY₉Si₆O₂₆ oxyapatite nanophosphors for optoelectronic applications

Abstract

Luminescent Sm³⁺-doped NaY₉Si₆O₂₆ oxyapatites were hydrothermally synthesized and studied for their structural, morphological, and optical properties, aiming for high-color-purity orange emission. X-ray diffraction confirmed a single-phase oxyapatite host lattice across 0.1–6 mol% Sm³⁺ doping, with nanoscale crystallites. Transmission electron microscopy revealed elongated sphere-like nanoparticles with an average size of ∼44 nm. All samples emitted intense orange light under 405 nm excitation, with chromaticity coordinates within the high-purity orange region of the CIE 1931 diagram. It was also shown that concentration quenching of Sm³⁺ emission in NaY₉Si₆O₂₆ host is predominantly governed by dipole–dipole electric multipolar interactions. The optimized NaY₉Si₆O₂₆:0.5 mol% Sm³⁺ sample demonstrated excellent thermal stability, maintaining 100 % of its emission intensity up to 200 °C and showing consistent luminescence during extended operation at 100 °C for 300 min. A prototype LED–phosphor device produced bright orange light under electrical excitation, confirming the potential of Sm³⁺-doped NaY₉Si₆O₂₆ nanophosphors for high-quality solid-state lighting