X-Ray Induced Light Emission of Yttrium Oxide

Abstract

The paper presents the experimental results of light radiation from Y2O3 ceramics caused by X-rays with energy up to 50 keV. The samples were made from commercial Y2O3 nanopowder by pressing and subsequent sintering in air at different temperatures from 1300 to 1500°С. Some samples sintered at 1500°C were additionally annealed at 1000°C for 10 hours. X-ray diffraction analysis of all samples did not reveal differences in the crystal structure that could be explained by heat treatment during sintering and annealing. The spectra of light emission in the wavelength range of 250-750 nm showed the presence of radiation from the electronic transitions of YO structures on the background of the luminescence of trivalent yttrium oxide. The presence of such lines of YO systems were observed also for the powder, which allows us to conclude that these structures appear on the surface of the crystallites during production. As the sintering temperature of the sample increased, the intensity of optical radiation increased. A significant difference in the effect of both temperature and sintering (annealing) time on the intensity of light emission of yttrium oxide was revealed. The intensity of the luminescent band, which is associated with the self-trapped exciton, increased with increasing thermal contribution (to estimate the contribution, we introduced a parameter equal to the product of temperature and the time of thermal action). The increase in spectral intensity in the second, third, fourth, and fifth line systems (especially for the system of lines with a maximum of λ=573.5 nm) considerably exceeded the one for self-trapped exciton. Our experimental results on the second, fourth and fifth systems of lines, which coincide well with the molecular lines YO, suggest that the heat treatment of the samples sintered from pressed Y2O3 powder leads to an increase in YO structures on the surface of the crystallites.