Neutral and warm white light emission in Tb3+/Sm3+ zinc phosphate glasses

A spectroscopy analysis of Tb3+ and Tb3+/Sm3+ doped zinc phosphate glasses based on emission spectra and decay time profiles was performed. The Tb3+ singly doped glass shows a green overall emission with x = 0.258 and y = 0.429 CIE1931 chromaticity coordinates, upon Tb3+ excitation at 318 nm. Under co-excitations of Tb3+ and Sm3+ at 344, 361 and 374 nm, the Tb3+/Sm3+ co-doped glasses display neutral and warm white overall emissions with CIE1931 chromaticity coordinates in ranges of x = 0.407-0.487 and y = 0.437-0.485, color temperature in the range of 2447-4024 K and quantum yield up to 12.38%, depending on the excitation wavelength and relative amount of Tb3+ and Sm3+. In all cases, it was observed that the Sm3+ emission is enhanced by the addition of Tb3+, which is correlated with a quenching of the Tb3+ emission as consequence of a non-radiative Tb3+ -> Sm3+ energy transfer process. The non-radiative nature of the energy transfer process was inferred by the shortening of the Tb3+ emission decay time observed in the Tb3+/Sm3+ co-doped zinc phosphate glasses. An analysis of the Tb3+ emission decay time profiles by the Inokuti-Hirayama model suggests that an interaction electric dipole-dipole into the Tb3+-Sm3+ clusters might dominate in the energy transfer process with efficiency and probability of 0.23-0.25 and 96.22-111.35 s(-1), respectively