Effect of Nd₂O₃ Concentration on the Defect Structure of CeO₂–Nd₂O₃ Solid Solution

Abstract

An extensive X‐ray study of CeO2–Nd2O3 solid solutions was performed, and the densities of solid solutions containing various concentrations of NdO1.5 were measured using several techniques. Solid solutions containing 0–80 mol% NdO1.5 were synthesized by coprecipitation from Ce(NO3)3 and Nd(NO3)3 aqueous solutions, and the coprecipitated samples were sintered at 1400°C. A fluorite structure was observed for CeO2–NdO1.5 solid solutions with 0–40 mol% NdO1.5, which changed to a rare earth C‐type structure at 45–75 mol% NdO1.5. The change in the lattice parameters of CeO2–NdO1.5 solid solutions, when plotted with respect to the NdO1.5 concentration, showed that the lattice parameters followed Vegard's law in both the fluorite and rare earth C‐type regions. The maximum solubility limit for NdO1.5 in CeO2 solid solution was approximately 75 mol%. The relationship between the density and the Nd concentration indicated that the defect structure followed the anion vacancy model over the entire range (0–70 mol% NdO1.5) of solid solution.

Cerium and neodymium co-precipitation in molten chloride by wet argon sparging

“…The evolution of the cell parameter refined from the X-ray diffraction patterns is in good agreement with data given in the literature [22,23,25] (Table 4, Fig. 8) and with the results from the precipitate.…”

“…There is no diffusion at 1250°C between the mixed oxide Ce 1Ày Nd y O 2À0.5y coming from precipitation and the mixed oxide Ce 1Àx Nd x O 2À0.5x coming from oxychloride conversion. The cerium/neodymium mixed oxides have been previously investigated by several authors [22][23][24][25]. With the increase of neodymium concentration, the mixed oxide structure changes from fluorine F-type (Fm 3 m, with a F unit cell parameter) to the superstructure C-type (Ia 3, a C % 2a F unit cell parameter) at about x Nd -% 0.40.…”

Lattice parameter, defect concentration and oxygen diffusion in ceria solid solutions

“…Even in GdO 1.5 -CeO 2 system the satellite peaks started to be seen at the concentration of 40 % GdO 1.5 . In the case of NdO 1.5 -CeO 2 system, the x-ray diffractions 6) are shown in Figure 2. At the low concentration of NdO 1.5 , the crystal was also in fluorite structure and at 45 % NdO 1.5 and higher concentration, satellite peaks were seen.…”

“…They are shown in Figures 3 and 4. [4][5][6] In order to calculate the lattice parameters in the range where there were no satellite peaks, all the peaks were used for the calculation. However, in the range where there were satellite peaks, only those peaks which corresponded to fluorite structure were used: satellite peaks were not used.…”

Lattice parameter, defect concentration and oxygen diffusion in ceria solid solutions

“…Even in Gd0u-Ce0 2 system the satellite peaks started to be seen at the concentration of 40 % GdOu. In the case of Nd0u-Ce0 2 system, the x-ray diffractions 6 l are shown in Figure 2. At the low concentration of NdOu, the crystal was also in fluorite structure and at 45 % NdOu and higher concentration, satellite peaks were seen.…”