Crystal structure and photoluminescence properties of Ho3+-doped germanium garnet phosphor NaY2Ga2InGe2O12

Narrow-band green phosphors with tunable decay dynamics have attracted continuous interest for exploring novel luminescent materials. In this work, a series of Ho 3+ -doped sodium yttrium gallium indium germanium garnet (NYGIG) phosphors were synthesized via a conventional high-temperature solid-state reaction route. X-ray diffraction and X-ray photoelectron spectroscopy confirm that Ho 3+ ions are successfully incorporated into the garnet lattice at dodecahedral Y 3+ sites without inducing impurity phases or significant lattice distortion. Under 453 nm blue light excitation, the as-prepared phosphors exhibit intense green emission centered at 548 nm, originating from the 5 S 2 / 5 F 4  →  5 I 8 transition of Ho 3+ , along with a weaker near-infrared emission band at ~ 758 nm assigned to the 5 I 4  →  5 I 8 transition. The green emission intensity reaches its maximum at a Ho 3+ doping concentration of 7 mol%, and the corresponding color purity is calculated to be 83.5%.