La3Ga5SiO14:Cr3+: A broadband near-infrared phosphor induced by the two-site occupation of Cr3+

The broadband near-infrared phosphors are feasible to apply in real-time nondestructive examination. In this work, La3Ga5SiO14:Cr3+ phosphors with the broadband near-infrared emission have been synthesized using a solid state reaction method. Their optical characteristics were investigated via the measurements of ultraviolet–visible diffused reflectance and luminescence spectra. The occupations of Cr3+ ions in La3Ga5SiO14 host were inquired by the X-ray absorption near edge structure and electron paramagnetic resonance analyses. The results indicate that Cr3+ ions substitute octahedral and tetrahedral Ga3+ ions in La3Ga5SiO14 host, which results in a sharp emission band coming from the 2Eg → 4A2g transitions of Cr3+ and a wide emission band coming from the 4T2g → 4A2g transitions of Cr3+. The fabricated NIR pc-LED device by combining the synthesized La3Ga5SiO14:0.10Cr3+ phosphor with a blue LED chip indicates that the La3Ga5SiO14:Cr3+ phosphors have potential applications in nondestructive examination.