Abstract
A spectroscopic analysis of sodium germanate glasses activated with Eu3+, Tb3+ and Eu3+/Tb3+ is performed from their photoluminescence spectra and decay times. In the Eu3+-singly doped glass reddish-orange light emission, with x=0.64 and y=0.35 CIE1931 chromaticity coordinates, is obtained upon Eu3+ excitation at 393nm. Such chromaticity coordinates are close to those (0.67, 0.33) proposed by the National Television Standard Committee for the red phosphor. When the sodium germanate glass is co-doped with Tb3+ and Eu3+ greenish-yellow light emission, with (0.41, 0.46) CIE1931 chromaticity coordinates, is obtained upon Tb3+ excitation at 344nm. Such greenish-yellow luminescence is due mainly to the terbium 5D4→7F6,5 and europium 5D0→7F1,2 emissions, Eu3+ being sensitized by Tb3+ through a non-radiative energy transfer. The non-radiative nature of this energy transfer is inferred from the increase in the decay rate of the Tb3+ emission when the glass is co-doped with Eu3+. From an analysis of the Tb3+ emission decay time curves it is inferred that such energy transfer might take place between Tb3+ and Eu3+ clusters through a short-range interaction mechanism.
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