Improved luminescence of CaAl12-xGaxO19:Cr3+ near-infrared phosphor based on Sr2+ and Ga3+ substitution

Abstract

Cr3+-doped near-infrared phosphors have recently attracted a wide attention. Here, NIR Ca1-ySryAl12-xGaxO19:0.12Cr3+ phosphors are obtained by a high-temperature solid-phase method. First, a series of CaAl7.88Ga4O19:0.12Cr3+ samples is studied and shows that the crystal field strength can be tuned by cation substitutions, until achieving a sharp emission at 692 nm and a broad emission at 780 nm under a 400 nm excitation, and an internal quantum yield of 90.73%. A further substitution by an appropriate amount of Sr2+ is suggested to be beneficial to increase the rigidity of the crystal structure by Debye temperature calculations. Experimentally, it is observed that Sr2+ for Ca2+ substitutions did not affect the luminescence wavelength and resulted in a significant increase of the thermal stability. When 0.7 Sr2+ substitute Ca2+, the thermal stability at 450 K increased by 28% compared to the samples without Sr2+.