Synthesis, characterization and thermal expansion studies on ThO2–SmO1.5 solid solutions

Highly homogeneous Th1−xSmxO2; 0 ≤ x ≤ 0.8 solid solutions were synthesized by a co-precipitation technique and the co-precipitated samples were sintered at 1473 K. Compositions of the solid solutions were characterized by standard wet-chemical analysis. X-ray diffraction measurements were performed on the sintered pellets for structural analysis, lattice parameter calculation and determination of solid solubility of SmO1.5 in ThO2 matrix. Bulk and theoretical densities of solid solutions were also determined. A fluorite structure was observed for ThO2–SmO1.5 solid solutions with 0–55.2 mol% SmO1.5. Thermal expansion coefficients were measured using high temperature X-ray diffraction technique. The mean linear thermal expansivity, α¯m for ThO2–SmO1.5 solid solutions containing 17.9, 41.7 and 52.0 mol% of SmO1.5 were determined in the temperature range 298–2000 K for the first time. The mean linear thermal expansion coefficients for ThO2–SmO1.5 solid solutions are 10.47, 11.16 and 11.45 × 10−6 K−1, respectively.