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

Abstract Cr 3+ ‐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 Cr 3+ ‐doped phosphors with the tetrahedrally coordinated Cr 3+ NIR emission behavior and ultra‐wide Vis–NIR luminescence. Herein, an unusual NIR‐emitting Mg 2 Al 4 Si 5 O 18 :Cr 3+ phosphor offers emission peak at 867 nm with full‐width at half‐maximum of 237 nm due to preferential occupation of the AlO 4 tetrahedra by Cr 3+ as demonstrated by structural and optical properties studies. Eu 2+ –Cr 3+ energy transfer is proposed to induce ultra‐wide Vis–NIR Mg 2 Al 4 Si 5 O 18 :Eu 2+ ,Cr 3+ phosphors with more efficient NIR emission and lower thermal quenching behavior of Cr 3+ . 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 Cr 3+ in tetrahedra and demonstrates the application of Mg 2 Al 4 Si 5 O 18 :Eu 2+ ,Cr 3+ phosphor in hyperspectral imaging, which will facilitate further research on NIR and Vis–NIR phosphors.