Solid solutions of higher valence actinides in TiO2 and ZrO2–Y2O3

Abstract

From X-ray diffraction, scanning electron microscopy, X-ray absorption near edge structure (XANES) and diffuse reflectance (DR) spectroscopic studies, it was found that approximately 0.03 formula units (f.u.) of mixed hexavalent and pentavalent U, but <0.001f.u. of Pu or Np, can be dilutely incorporated into the Ti site of rutile, TiO2, sintered at 1400°C in air. The valence of 0.01f.u. of U in Zr(1−x)YxO2−x/2 (x=0.23–0.5) fired in air is also between +5 and +6 based on XANES. The presence of U5+ is confirmed in both rutile and doped zirconia samples by DR spectroscopy. The valence of 0.01f.u. of Np in Zr(1−x)YxO2−x/2 (x=0.23–0.5) fired in air is found to be +6 from DR study.