Afterglow Luminescence of Lu2O3:Eu Ceramics Synthesized at Different Atmospheres

Three series of Lu2O3:Eu Ceramic Materials doped with different concentrations of Eu3+ ions (0.05-5 atom %) were prepared by sintering at the temperature of 1700 degrees C of nanocrystalline powders. The heat-treatments were performed in oxidizing, slightly reducing, and strongly reducing atmosphere of air, vacuum, and a N-2-H-2 mixture (9:1 by volume), respectively. The radioluminescent properties of these materials have been systematically Studied. After exposure to X-rays, independent of the atmosphere of the preparation, the ceramics exhibited all extensive afterglow, especially long and strong for low Eu concentrations. The afterglow and radioluminescence spectra differed significantly with the former showing Much more emission resulting from Eu3+ ions Occupying the S-6 symmetry site ill the host compared to the activator in the C-2 position. The effect was especially significant within the range of low and medium Eu concentrations, 0.05-1 atom %. From the decay traces of the persistent luminescence of Lu2O3:Eu ceramics it was Concluded that the mechanism of the process is governed by the second order kinetics. It is Postulated that only Eu3+ ions located within the layer containing both S-6 and C-2 metal ion sites tire active in the afterglow emission, while those placed within the layer consisting of only the C-2, metal ion sites do not contribute to the afterglow. Another option is that electronic levels of Eu3+ in S-6 site are more favorably positioned to intercept migrating from their traps excited carriers.