Spectroscopic analysis of color-tunable LiLaMgWO6:Ln3+(Ln=Sm, Tb) phosphor for opto-electronic applications

Abstract

This study investigates the tunable photoluminescence properties of LiLaMgWO₆ phosphors doped with Sm³⁺ and Tb³⁺ ions, synthesized through a solid-state reaction method. Structural analysis via X-ray diffraction confirmed the monoclinic double perovskite phase (space group C2/m), while energy-dispersive X-ray spectroscopy validated elements present in as prepared sample. SEM studies have confirmed the morphology. Raman spectroscopy revealed that co-doping enhances peak intensities, correlating with improved luminescent behaviour. Photoluminescence studies confirmed the emission of Sm³⁺ at 604 nm (⁴G_5/2 → ⁶H_7/2) for excitation of 404 nm (⁶H_5/2 → ⁴D_7/2), and for Tb³⁺, emission was observed at 545 nm (⁵D₄ →⁷F₅) for excitation of 305 nm. The energy transfer leads to improved PL intensity of the green emission band of Tb³⁺ ion via co-doping with Sm³⁺ ions. Lifetime analysis helps to verify the energy transfer mechanism. The wide color tunability from the reddish orange to green region and the changes in color purity of Tb³⁺ doped phosphors via Sm³⁺ doping is elucidated through CIE diagrams. Also, the CCT analysis indicates a warm nature of the emitted light. These findings highlight the potential of LiLaMgWO₆ Sm³⁺/Tb³⁺ phosphors for application in display technologies and white light-emitting diodes (wLEDs).