Abstract: Mg₁₄Ge₅O₂₄:Cr near-infrared(NIR)phosphors were synthesized by the high-temperature solid-phase method to achieve the coexistence of Cr³⁺ and Cr⁴⁺ valence luminescence. The crystalline phases of the samples were analyzed using XRD and GASA refinement software. The material has two luminescence centers, one from Cr³⁺ occupying the octahedral Ge⁴⁺ position with an emission band in the NIR I region and a half-peak width up to 256 nm, and the other from Cr⁴⁺ occupying the tetrahedral Ge⁴⁺ position with an emission band in the NIR II region and a half-peak width up to 266 nm. The luminescence properties of the material were analyzed by low-temperature spectra and lifetime decay curves. The modulation of Cr³⁺ and Cr⁴⁺ luminescence can be achieved by using Ga³⁺ instead of Ge⁴⁺. The addition of large radius Ga³⁺ ions generates new lattice sites, which affects the overall crystal field intensity, and a phosphor with more intense luminescence in the NIR I region is obtained.

Key words: luminescence, near infrared, Mg₁₄Ge₅O₂₄:Cr, Ga³⁺