Ultra-Wide Vis–NIR Mg2Al4Si5O18:Eu2+,Cr3+ Phosphor Containing Unusual NIR Luminescence Induced by Cr3+ Occupying Tetrahedral Coordination for Hyperspectral Imaging

Cr3+-activated broadband near-infrared (NIR) phosphors, featured by the octahedral coordination preference and strong absorption in visible (Vis) region, have great potential application in nondestructive assessment. It is still a challenge to develop Cr3+-doped phosphors with the tetrahedrally coordinated Cr3+ NIR emission behavior and ultra-wide Vis–NIR luminescence. Herein, an unusual NIR-emitting Mg2Al4Si5O18:Cr3+ phosphor offers emission peak at 867 nm with full-width at half-maximum of 237 nm due to preferential occupation of the AlO4 tetrahedra by Cr3+ as demonstrated by structural and optical properties studies. Eu2+–Cr3+ energy transfer is proposed to induce ultra-wide Vis–NIR Mg2Al4Si5O18:Eu2+,Cr3+ phosphors with more efficient NIR emission and lower thermal quenching behavior of Cr3+. The fabricated Vis–NIR phosphor-converted light-emitting diode is expected to be an alternative to halogen lamp in hyperspectral imaging. This work reveals the luminescence behavior of Cr3+ in tetrahedra and demonstrates the application of Mg2Al4Si5O18:Eu2+,Cr3+ phosphor in hyperspectral imaging, which will facilitate further research on NIR and Vis–NIR phosphors.