Spectrally tunable near-infrared photoluminescence in MP 3 O 9 :Cr 3+ (M = Al, Ga, In) phosphate phosphors.

Modulation of the octahedral crystal field environment of Cr 3+ is an effective approach to achieve tunable emission. Here, we prepared a series of broadband MP 3 O 9 :Cr 3+ (M = Al, Ga, In) near-infrared (NIR) phosphors, and cubic AlP 3 O 9 :Cr 3+ (APO-c:Cr 3+ ) and monoclinic AlP 3 O 9 :Cr 3+ (APO-m:Cr 3+ ) phosphors were prepared by controlling the synthesis temperature. The emission wavelength was tuned from 787 nm for APO-c:Cr 3+ to 894 nm for monoclinic InP 3 O 9 :Cr 3+ (IPO:Cr 3+ ) by regulating the M ion and reducing the crystal field intensity. Excitingly, the MP 3 O 9 :Cr 3+ (M = Al, Ga, In) family shows excellent thermal stability; the emission intensity of APO-c:Cr 3+ , APO-m:Cr 3+ and monoclinic GaP 3 O 9 :Cr 3+ (GPO:Cr 3+ ) can still maintain 95.6%, 86% and 86% of that at room temperature when heating to 423 K, respectively. An NIR LED device was prepared by incorporating GPO:Cr 3+ and a blue light LED, demonstrating the potential application in night vision and non-destructive testing.