Effects of the host lattice and doping concentration on the colour of Tb3+ cation emission in Y2O2S:Tb3+ and Gd2O2S:Tb3+ nanometer sized phosphor particles

Y2O2S and Gd2O2S phosphor lattices activated with a range of Tb3+ concentrations have been successfully prepared as nanoparticles and their emission properties have been characterized using SEM, XRPD, photoluminescence spectroscopy and cathodoluminescence. D-5(3)-D-5(4) cross relaxation processes between Tb3+ cations were observed in both Y2O2S and Gd2O2S as a function of Tb3+ concentration. In the Y2O2S host lattice, the predominant emission colour shifts from blue to green with increased Tb3+ concentration. In contrast, green emission is always predominant in Gd2O2S at Tb3+ concentrations from 0.1 mol% to 5 mol%. This finding is explained in accordance with previous reports on the bulk materials that found the Gd2O2S lattice has a lower charge transfer state than the Y2O2S host lattice.