Environmentally Friendly Fe³⁺-Activated Li₂MgTi₃O₈ Far-Red Emitting Phosphors for Dual-Mode Optical Thermometry and...

Fe³⁺-activated luminescent materials have recently evoked considerable interest owing to their environmentally friendly and versatile applications potential. In this study, novel Li₂MgTi₃O₈: Fe³⁺ phosphors are synthesized and its luminescence properties were systematically investigated. The Li₂MgTi₃O₈: Fe³⁺ phosphor exhibits a broad excitation spectrum covering the ultraviolet-visible region from 250 to 600 nm. Upon 417 nm excitation, the as-prepared phosphor shows a broad far-red emission band centered at 709 nm due to the ⁴T₁ (⁴G) → ⁶A₁ (⁶S) transition of Fe³⁺ ions, along with a good internal quantum efficiency (IQE) of 39%. Importantly, the emission band of phosphors can be well matched with the absorption spectra of plant pigments. Furthermore, the temperature sensing properties of the phosphor samples were analyzed by using the fluorescence intensity (FI) and fluorescence lifetime (FL) technique, achieving maximum relative sensitivities (S_r) of 1.73% K^-1@423 K and 3.52% K^-1@373 K, respectively. These results indicate that Li₂MgTi₃O₈: Fe³⁺ phosphors have potential applications for optical thermometry and plant growth illumination.