The photoluminescence of terbium-activated yttrium silicate with the genera
l formula Y2-xTbxSiO5 was investigated as a function of Tb3+ concentration.
Especially, the main attention was focused on the D-5(3) fluorescence and
its energy transfer behavior. The emission and excitation spectra were meas
ured in terms of Tb3+ concentration. The diffuse reflectance spectrum was a
lso 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. T
he concentration quenching was investigated in terms of luminance and decay
time both for D-5(3) and D-5(4) fluorescence. The energy transfer was also
investigated by analyzing the decay curve of D-5(3) emission on the basis
of the multipolar interaction. The decay curves of D-5(3) emission, for whi
ch well-known cross-relaxation has been accepted as a main factor, were ana
lyzed by Inokuti and Hirayama's formula on the basis of the direct quenchin
g scheme. Furthermore, the rate equations including a newly proposed quench
ing scheme were taken into consideration. The rate equations accept the emi
ssion quenching as due to the cross-relaxation from D-5(3 or 4) to some upp
er levels such as D-7 and the charge-transfer band.