Luminescence properties of Eu3+ and TiIV/ZrIV doped yttrium oxysulfides (Y2O2S:Eu3+,TiIV/ZrIV)

Abstract

The red emitting Y2O2S:Eu3+,TiIV (or ZrIV, xEu: 0.01, xTi/Zr: 0.003/0.015/0.03) materials were prepared with a flux method. According to X-ray powder diffraction, the materials have the hexagonal crystal structure. The UV excited (λexc: 250 nm) emission maximum was observed at 628 nm due to the 5D0→7F2 transition of Eu3+. The excitation spectra (λem: 628 nm) consist of broad bands centered at 240 and 320 nm due to the charge transfer transitions O2−→Eu3+ and S2−→Eu3+, respectively. Red persistent luminescence was observed with a maximum at 628 nm, as well. Persistent luminescence was the strongest with the TiIV co-doping though the intensity of persistent luminescence decreased with the increasing amount of both the TiIV and ZrIV co-dopants. The thermoluminescence (TL) glow curves of the Y2O2S:Eu3+,TiIV materials consist of bands at ca. 110 and 200 °C. In Y2O2S:Eu3+,ZrIV, similar bands are observed at lower temperatures viz. at ca. 100 and 180 °C. TL weakens when the amount of co-dopants is increased. The TiIV co-doped materials have stronger TL than the ZrIV co-doped materials. The deconvolution of TL glow curves revealed three distinct traps with depths ranging from 0.6 to 1.0 eV.