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 Tb(3+) concentrations have been successfully prepared as nanoparticles and their emission properties have been characterized using SEM, XRPD, photoluminescence spectroscopy and cathodoluminescence. (5)D3-(5)D4 cross relaxation processes between Tb(3+) cations were observed in both Y2O2S and Gd2O2S as a function of Tb(3+) concentration. In the Y2O2S host lattice, the predominant emission colour shifts from blue to green with increased Tb(3+) concentration. In contrast, green emission is always predominant in Gd2O2S at Tb(3+) 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.