Enhancement of the NIR Emission of Cr³⁺–Yb³⁺ Co-doped La₃GaGe₅O₁₆ Phosphors by Doping Nd³⁺ Ions via Efficient Energy Transfer for NIR Spectroscopy Regulation

The efficient energy transfer in La₃GaGe₅O₁₆:Cr³⁺, Yb³⁺/Nd³⁺ and La₃GaGe₅O₁₆:Cr³⁺, Yb³⁺, Nd³⁺ was investigated in detail. In this phosphor, Cr³⁺ acts as the energy absorber (250–700 nm) to sensitize Yb³⁺/Nd³⁺ in La₃GaGe₅O₁₆. Under excitation at 418 nm, La₃GaGe₅O₁₆:Cr³⁺, Yb³⁺ phosphors exhibited a broad emission band in the near-infrared (NIR) region located at 976 nm (La₃GaGe₅O₁₆:Cr³⁺, Nd³⁺ at 1056 nm), which was attributed to the ²F_5/2–²F_7/2 transition of the Yb³⁺ ions (²F_3/2 → ⁴I_11/2 transition of Nd³⁺). Moreover, a Nd³⁺ ion was introduced into La₃GaGe₅O₁₆:Cr³⁺, Yb³⁺. The analysis of excitation spectra and decay time proves that Nd³⁺ acts as a bridging ion in the system. This can be used as a new strategy to enhance the energy transfer in Cr³⁺, Yb³⁺ co-doped phosphors, and these phosphors have potential applications in NIR spectroscopy regulation.