This work focuses on a particular behavior of dense yttria samples fabricated by spark plasma sintering, which display a reddish coloration when subjected to X-ray irradiation. The reddish coloration appears exclusively in sintered material. Optical measurements, X-ray photoelectron spectroscopy and chemical methods have been used to investigate the properties of consolidated yttria. The results obtained suggest that the sintered material exhibits a relatively high concentration of oxygen vacancies. Thermoluminescence measurements indicate that they act as electronic trapping sites. A generalized-order kinetic analysis suggests that at least five different shallow traps can be identified. (C) 2014 Elsevier B.V. All rights reserved.