Mass-spectrometric determination of oxygen potential of hypostoichiometric urania–yttria solid solution

The oxygen potentials of hypostoichiometric urania–yttria solid solutions expressed as nearly U1−yYyO2−x (x=y/2) are investigated by use of a mass spectrometer combined with Knudsen cell. The pertinent ions observed in this study were UO2+, UO+ and U+. The ions associated with yttrium atoms were not observed up to about 2200 K. The partial pressures of uranium-bearing vapor species over the solid solutions were determined by comparing their ion intensities to those of UO2+ for UO2 specimen. It was found that the oxygen potentials of U1−yYyO2−x (x=y/2) are almost in agreement with those for pure urania having the same oxygen deficiencies.