Hydration-induced coupling of the excitonic state of Y2O3with its phonon: Negative effect on the luminescence efficiency of Y2O3:Eu+3nanophosphor

Abstract

Luminescence properties of a series of samples of Y2O3:Eu+3red phosphor of particle sizes ranging from 50 to 300 nm were investigated as a function of time to decipher the long-standing mystery of the effect of reduction of particle size on the luminescence efficiency of the phosphor. The samples were found to lose luminescence efficiency and suffer a change in the excitation profile with time. Infrared studies showed that although the samples at their freshly prepared stage were almost free from contaminated water, on aging in air at room temperature, they absorbed the latter. The phenomenon of hydration-induced coupling of the excitonic state of Y2O3with one of its Fumodes was detected in the case of the aged sample, which was shown to be instrumental in introducing newer nonradiative channels in the system. Because of larger surface-to-volume ratio, the effect was most pronounced in the case of nanocrystalline samples.