Broadband near-infrared luminescence and energy transfer of Cr3+, Ce3+ co-doped Ca2LuHf2Al3O12 phosphors

Broadband near-infrared phosphors are highly desirable for food testing. Targeted Ca2LuHf2Al3O12:Cr3+ (CLHA:Cr3+) and Ca2LuHf2Al3O12:Ce3+,Cr3+ (CLHA:Ce3+,Cr3+) phosphors were synthesized by the conventional high-temperature solid state reaction. The CLHA:Cr3+ phosphor, with a good thermal stability, shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr3+ content. For co-doped sample, the emission intensity of Cr3+ can be enhanced by three times due to the energy transfer from Ce3+ to Cr3+, which can be evidenced by a significant overlap between the PLE of Cr3+ single-doped phosphor and the PL of Ce3+ single-doped phosphor. In addition, the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay lifetime and Dexter's energy transfer formula. The broadband NIR emission peaked at 775 nm of CLHA:Cr3+,Ce3+ phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.