Mechanism of upconversion emission enhancement in Y3Al5O12:Er3+/Li+ powders

Er3+ and Li+ codoped Y3Al5O12 (YAG) powders were prepared for a systematic investigation of their upconversion emissions. X-ray diffraction (XRD), upconversion emission spectra, pump power dependence, FT-IR spectra and decay time were studied to characterize the samples. With Li+ doping, the upconversion emission intensity of Er3+ doped YAG powders was obviously enhanced, accompanied with an increase in the ratio of green to red intensity. The enhancement of emission intensity could be attributed to two mechanisms: one was the distortion of local crystal field around Er3+, and the other was the decrease in the amount of CO32− and OH− groups. Our results revealed that the latter was the dominant mechanism of the upconversion intensity enhancement in the YAG:Er3+/Li+ powders.