Luminescence and decay behaviors of Tb-doped yttrium silicate

Abstract

The photoluminescence of terbium-activated yttrium silicate with the general formula Y2−XTbxSiO5 was investigated as a function of Tb3+ concentration. Especially, the main attention was focused on the 5D3 fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+ concentration. The diffuse reflectance spectrum was also measured in the range from VUV to UV. As a result, yttrium silicate was found to have a broad absorption band extended from the VUV to UV range. The concentration quenching was investigated in terms of luminance and decay time both for 5D3 and 5D4 fluorescence. The energy transfer was also investigated by analyzing the decay curve of 5D3 emission on the basis of the multipolar interaction. The decay curves of 5D3 emission, for which well-known cross-relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula on the basis of the direct quenching scheme. Furthermore, the rate equations including a newly proposed quenching scheme were taken into consideration. The rate equations accept the emission quenching as due to the cross-relaxation from 5D3 or 4 to some upper levels such as 7D and the charge-transfer band.