Mixed-Phase Engineering in Single Particles for Enhancing Performance of Fe ^{3 <b>+</b>} Doped Mg ₃ Ga ₂ GeO ₈ Phosphors

Developing high-efficiency and broadband near-infrared (NIR) phosphors is a core demand in the field of advanced optoelectronics. However, achieving the synergistic improvement of their quantum efficiency and thermal stability remains a critical challenge awaiting breakthrough. In this study, the Mg₃Ga₂GeO₈:Fe³⁺ phosphor was selected as the research system, and a modification strategy via Al³⁺ substitution for Ga³⁺ was proposed. This strategy successfully realized the structural transformation of the material from a single-phase structure to a single-particle multiphase structure, while significantly optimizing its NIR luminescent performance and thermal stability. The single-particle multiphase phosphor obtained via multiphase engineering exhibits excellent quantum yield (92.6%) and thermal stability (89.4%@150 °C). Integrating this single-particle multiphase phosphor with a 365 nm near-ultraviolet chip yielded an NIR phosphor-converted light-emitting diode (pc-LED). The device exhibited a stable NIR output power of 1.97 mW at a working current of 120 mA and possesses biological tissue penetration capability, demonstrating promising application potential in night vision imaging, noninvasive blood vessel visualization, and other fields. This study confirms that inducing the formation of a single-particle multiphase structure via ion substitution is an effective strategy for optimizing the comprehensive performance of Fe³⁺-doped phosphors, providing important insights for the design and development of high-performance NIR phosphors.