Crystal Field-Engineered Cr3+-Doped Gd3(MgxGa5–2xGex)O12 Phosphors for Near-Infrared LEDs and X-ray Imaging Applications

Inorganic materials doped with chromium (Cr) ions generate remarkable and adjustable broadband near-infrared (NIR) light, offering promising applications in the fields of imaging and night vision technology. However, achieving high efficiency and thermal stability in these broadband NIR phosphors poses a significant challenge for their practical application. Here, we employ crystal field engineering to modulate the NIR characteristics of Cr³⁺-doped Gd₃Ga₅O₁₂ (GGG). The Gd₃Mg_xGa_5-2xGe_xO₁₂ (GMGG):7.5% Cr³⁺ (x = 0, 0.05, 0.15, 0.20, and 0.40) phosphors with NIR emission are developed through the cosubstitution of Mg²⁺ and Ge⁴⁺ for Ga³⁺ sites. This cosubstitution strategy also effectively reduces the crystal field strength around Cr³⁺ ions, which results in a significant enhancement of the photoluminescence (PL) full width at half-maximum (fwhm) from 97 to 165 nm, alongside a red shift in the PL peak and an enhancement of the PL intensity up to 2.3 times. Notably, the thermal stability of the PL behaviors is also improved. The developed phosphors demonstrate significant potential in biological tissue penetration and night vision, as well as an exceptional scintillation performance for NIR scintillator imaging. This research paves a new perspective on the development of high-performance NIR technology in light-emitting diodes (LEDs) and X-ray imaging applications.