Tb 3 + single- and Tb 3 + / Eu 3 + double-doped borate as well as fluorozirconate glasses are investigated for their photoluminescence and energy transfer properties based on the concentration of the dopants. All the double-doped glasses consist of a constant concentration of 0.5 at% Tb 3 + ions and an increasing Eu 3 + ions concentration, ranging from 0.05 to 0.5 at%. Upon direct excitation of only Tb 3 + at 485 nm, the emission spectra of the double-doped glasses demonstrate an enhancement of typical Eu 3 + emissions, thus validating the energy transfer from Tb 3 + to Eu 3 + in both glass systems. While the spectral composition of the emissions of both borate and fluorozirconate glasses are mostly similar, the radiative decay in borate glass is faster than in fluorozirconate glass. The energy transfer efficiency in each glass system is calculated based on the radiative decay measurements. The mechanism of multipolar interaction underlying the energy transfer is determined to be mostly due to dipole-dipole interactions. With increasing Eu 3 + concentration, a gradual shift in chromaticity from green to orange/red is observed. Besides the variation in Eu 3 + concentration, tunable chromaticity can also be achieved by varying the excitation wavelength.
