Concentration‐Induced Hetero‐Valent Partial‐Inverse Occupation of Infrared Phosphor

Abstract Infrared luminescent materials have evoked much attention from chemists and material scientists. Although substantial progress is made in materials design, the luminescent mechanism remains ambiguous in the complex structures, presenting major barriers to developing novel infrared luminescent materials. Herein, this study aims to deliberate a complete discussion on infrared phosphors with concentration‐induced hetero‐valent partial‐inverse occupation. High‐resolution synchrotron X‐ray diffraction and Raman spectroscopy reveal the subtle structural change in LiGa_5(1−x)O₈:5xCr³⁺. Besides, Cr K‐edge wavelet analysis and extended X‐ray absorption fine structure illustrate the impact of Cr in the second shell of another Cr ion and the practical coordination of Ga and Cr ions. Furthermore, unexpected two‐center Cr³⁺ emissions and the Cr–Cr pair emission are observed at high Cr concentrations. Variation between the zero‐phonon line and N‐line at different temperatures is demonstrated. Finally, the structural and luminescent properties are comprehensively discussed, providing the origin of the unexpected Cr2 emission. This study not only provides insight into the hetero‐valent partial‐inverse occupation process in inorganic materials but also sheds light on developing novel infrared luminescent materials.