Tuning the Near Infrared Emission of MgO:Cr3+ Phosphors by Inducing Ti4+ Ions

Near-infrared (NIR) phosphors activated by Cr 3+ ions hold significant potential for applications such as night vision and plant growth lighting due to their tunable emission properties governed by crystal field (CF) strength. In this study, Cr 3+ and Ti 4+ co-doped MgO phosphors were synthesized via a high-temperature solid-state reaction to modulate the NIR emission. Structural and optical characterizations revealed that Ti 4+ incorporation enhances the CF strength ( D q/ B ratio increases from 2.4 to 2.6), inducing a blue shift in the emission peak from 810 (MgO:Cr 3+ ) to 780 nm (Mg 0.8 Ti 0.2 O:Cr 3+ ) and with a strong sharp emission at 720 nm. The Ti 4+ doping also increases the fluorescence lifetime from 150.9 to 816.4 μs, attributed to altered Cr 3+ occupancy in octahedral sites and modified spin-allowed transitions. These findings demonstrate that Ti 4+ co-doping effectively tunes the NIR emission of MgO:Cr 3+ phosphors, offering a promising strategy for designing wavelength-adjustable NIR light sources.