Ca/Si Modification of the (Gd,Lu)AG Garnet for Enhanced Broadband Cr Luminescence of High Thermal Stability.

Near-infrared (NIR)-emitting phosphors with high quantum efficiency and thermal stability are crucial to NIR pc-LEDs. Garnet-structured (GdLuCa)(AlSiCr)O ( = 0.01-0.2) and (GdLuCa)(AlSiCr)O ( = 0.2-1.0) new phosphors with promising NIR luminescence under blue light excitation were designed and fabricated by a solid-state reaction in this work. It was analyzed that the Ca, Cr, and Si ions would replace Gd in [GdO], Al1 in [Al1O], and Al2 in [Al2O], respectively, and the optimal Cr content is = 0.05, above which concentration quenching would occur via an electric dipole-dipole interaction. Increasing Ca/Si substitution up to = 1.0 led to luminescence enhancement by a factor of up to 1.85 and internal/external quantum efficiency (%) increment from ∼25.9/10.7 to 63.4/27.5, and all of the phosphors showed excellent thermal stability (/ ≥ 87.6%). The luminescence properties of Cr were discussed in detail through systematic investigation of the effects of Cr and Ca/Si contents on the crystal structure, local coordination, and crystal field. With the NIR pc-LED device integrated from the optimal phosphor ( = 1.0) and a blue LED chip, electroluminescence manifested potential applications in night vision and medical diagnosis.