A novel rare-earth free red-emitting Li3Mg2SbO6:Mn4+ phosphor-in-glass for warm w-LEDs: Synthesis, structure, and luminescence properties

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Developing a novel non-rare-earth activated oxide red phosphor with admirable luminescent performance and low cost is still of great interest in the field of energy-saving warm white light-emitting diodes (w-LEDs) illumination. Here, Li3Mg2SbO6:Mn4+ (LMSO:Mn4+) red-emitting phosphor has been successfully prepared with cheap raw materials via a traditional solid-state method. Crystal structure, morphology, composition as well as optical properties are studied in detail. The prepared LMSO:Mn4+ phosphor exhibits a broad and deep red emission band in the range of 600–750 nm with the maximum centered at 666 nm, which is ascribed to the Mn4+:2Eg→4A2g transition in [SbO6] octahedral environment. Moreover, the nephelauxetic effect of Mn4+ in the LMSO matrix is evaluated by investigating the crystal field strength (Dq) and Racah parameters (B and C). Importantly, LMSO:0.01Mn4+ phosphor demonstrates good thermal stability and high quantum efficiency. By embedding LMSO:Mn4+ and Y3Al5O12:Ce3+ phosphors with various ratios in the TeO2-based glass host, a series of phosphors-in-glass(PiG) composites are achieved and demonstrate to remain the original optical properties of phosphors. Remarkably, by coupling PiG color converters with a blue LED chip, high-power w-LEDs devices with tunable optoelectronic parameters are constructed, with the correlated color temperature evolving from cool white (6783 K) to warm one (4014 K) and the color rendering index increasing from 72.2 to 88.7.