Synthesis and photoluminescence properties of (Y,Gd)SiO5:Tb3+ under VUV excitation

Single phase of green-emitting X2−(Y,Gd)SiO5:Tb3+ phosphoqr was successfully prepared at 1250 °C by a co-precipitation process. The photoluminescence of as-prepared Y1.9SiO5:0.1Tb3+ and Y1.85Gd0.05SiO5:0.1Tb3+ were investigated in vacuum ultraviolet region. Under 147 nm excitation, the phosphors showed main emission peak at 543 nm attributed to the 5D4→7F5 transition of Tb3+. According to the relative emission intensity of samples with different composition, the optimal substitution proportions of Tb and Gd for Y were determined to be 10% and 5%, respectively. Besides, Y1.85Gd0.05SiO5:0.1Tb3+ maintained the short decay time of Y2SiO5:Tb3+ phosphor only 3.5 ms, which is much shorter than the commercial green-emitting phosphor Zn2SiO4:Mn2+. As showed in the excitation spectrum, the 141 and 175 nm excitation bands were assigned to the charge transfer bands of Y-O and Gd-O, respectively. Compared to Y2SiO5:Tb3+, Gd3+ provided another energy transfer channel from matrix to the luminescence center Tb3+, thereby enhancing the photoluminescence efficiency. The projected density of states of Y2SiO5 and Gd2SiO5 were also discussed in this work trying to understand the charge transfer mechanics of this phosphor.