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Cell parameters and linear thermal expansion studies of the Th–M oxide systems with general compositions Th 1− x M x O 2− x /2 (M = Eu 3+ , Gd 3+ and Dy 3+ , 0.0 ⩽ x ⩽ 1.0) are reported. The XRD patterns of each product were refined to specify the solid solubility limits of MO 1.5 in the ThO 2 lattice. The upper solid solubility limits of EuO 1.5 , GdO 1.5 and DyO 1.5 in the ThO 2 lattice under conditions of slow cooling from 1673 K are represented as Th 0.50 Eu 0.50 O 1.75 , Th 0.60 Gd 0.40 O 1.80 and Th 0.85 Dy 0.15 O 1.925 , respectively. The linear thermal expansion (293–1123 K) of MO 1.5 and their single-phase solid solutions with thoria were investigated by dilatometery. The average linear thermal expansion coefficients ( α ¯ ) of the compounds decrease on going from EuO 1.5 to DyO 1.5 . The values of α ¯ for EuO 1.5 , GdO 1.5 and DyO 1.5 containing solid solutions showed a downward trend as a function of the dopant concentration. The linear thermal expansion (293–1473 K) of the solid solutions investigated by high-temperature XRD also showed a similar trend. |
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