Synthesis and characterization of Th1−xLnxO2−x/2 mixed-oxides

Abstract Several Th 1− x Ln x O 2− x /2 mixed-oxides (Ln = Nd, Sm, Gd, Dy, Er or Yb) were prepared from oxalate precursors. Structural and microstructural investigations of both initial precursors and resulting oxides were undertaken by XRD, μ-Raman spectroscopy and SEM, with a particular attention paid to the Th 1− x Nd x O 2− x /2 series. For oxides, XRD and μ-Raman agreed well with the stabilization of the F m 3 ¯ m structure up to x Nd = 0.4, thanks to the concomitant creation of oxygen vacancies, as also confirmed by μ-Raman. Then, a structural transition to the I a 3 ¯ superstructure occurred. For x Nd ≥ 0.49, mixed-oxides with an additional hexagonal Nd 2 O 3 phase were prepared. Besides, the unit cell parameter of the Th 1− x Ln x O 2− x /2 series followed a quadratic relation versus the x substitution rate as a result of the combination between modifications of cationic radius and cation coordination, and the decrease of O O repulsion linked to the presence of oxygen vacancies.