Ultra‐Wide Vis–NIR Mg<sub>2</sub>Al<sub>4</sub>Si<sub>5</sub>O<sub>18</sub>:Eu<sup>2+</sup>,Cr<sup>3+</sup> Phosphor Containing Unusual NIR Luminescence Induced by Cr<sup>3+</sup> Occupying Tetrahedral Coordination for Hyperspectral Imaging
Xikun Zou, Haoran Zhang, Wei Li, Mingtao Zheng, Мaxim S. Моlokeev, Zhiguo Xia, Yinjian Zheng, Qingming Li, Yingliang Liu, Xuejie Zhang, Bingfu Lei
Abstract
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.