Heat treatments of Gd2O2S:Tb, Y2O2S:Tb phosphors

It's well known, that some heat treatments improve significantly the light yield of Gd2O2S:Tb, Y202S:Tb phosphors, but processes ofthe energy transfer at excitations need further investigations. We present the new results ofthe synthesis and heat treatments optimization of oxysulfide phosphors. The heat treatments curried out at different ambient atmospheres in temperature range 200-1000°C. To measure kinetic properties of defects formations/annealing at heat treatments we measured the dependencies ofrelative defect concentrations on the duration of isothermal annealing. The investigation of bulk and surface defects in phosphors before and after heat treatments carried out at different excitation with different methods: spectra measurements with direct Tb3+ center excitation (4.9 eV UV excitation), spectra measurements with above gap excitation (X-ray; 1 kV and 10 kV electrons, 8.4 eV VUV excitation), thermo-stimulated luminescence measurements. The results of investigations allow us to increase the light yield of phosphors (20% increase in comparison with commercial samples).