Lattice parameter and thermal conductivity of Th1−M O2− (M = Y, La, Ce, Nd, Gd and U)

Lattice contraction and lattice deformation of UO 2 and ThO 2 doped with Gd 2 O 3

“…The ThO 2 fluorite lattice parameter contracts with À12.6 ± 0.2 pm per substitution fraction x. This value agrees with the lattice contractions reported by Mathews et al [10] and Muta et al [12] for low dopant concentrations and our observations indicate that the linear contraction continues also for the higher dopant concentrations. The results of Mathews et al [10] seemed to indicate that the lattice contraction at x !…”

“…This work À12.5 ± 0.2 0.9986 Mathews et al [10] À9.9 ± 0.7 0.9800 Muta et al [12] À12.0 1 Horlait et al [11] À4.9 ± 0.5 0.9939 …”

Synthesis of UO2 and ThO2 doped with Gd2O3

“…Indeed, the powder metallurgical route applied by Mathews et al [42] uses several heating (at different temperatures and very prolonged sintering times of 36-48 h) and regrinding steps to obtain single-phased samples. Muta et al [15] also used multiple grinding and sintering steps and in addition, the final sintering was performed via spark plasma sintering under pressure. Both works confirm the difficulty in achieving highly dense, single-phased doped ThO 2 pellets using powder metallurgy.…”

“…The REEs are present in the form of oxides dissolved in the fuel [12]. Therefore, the study of thoria-rare-earth oxide (ThO 2 -REO) systems and the effect of incorporation of REEs on the material properties have been and still are of interest to the scientific community [13][14][15]. Also from a more fundamental point of view, the Th 1Àx RE x O 2Àx/2 systems are intriguing because a large amount of defects in the form of oxygen vacancies are formed to compensate for the substitution of Th 4+ cations by RE 3+ cations, especially at high REE concentrations [16].…”

“…In the specific case of Gd 2 O 3 -doped UO 2 production, powder metallurgical routes were described by Grossman et al [32], Yuda and Une [33], and Riella et al [34], coprecipitation processes by Manzel and Dörr [35], Fukushima et al [36], Miyake et al [37], Riella et al [34], Leyva et al [38], and Durazzo et al [39], and sol gel routes by Gündüz et al [40,41]. For the synthesis of Gd 2 O 3 -doped ThO 2 , powder metallurgical routes were described by Mathews et al [42] and Muta et al [15], and co-precipitation processes by Horlait et al [13].…”