The influence of ionic radii on the grain growth and sintering-resistance of Ln₂Ce₂O₇ (Ln = La, Nd, Sm, Gd)

Rare earth cerium oxides (Ln₂Ce₂O₇, Ln = La, Nd, Sm, and Gd) with cubic-fluorite structure were prepared by hydrothermal method using cetyltrimethyl ammonium bromide as surfactant. X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), Raman spectroscopy, and field emission scanning electron microscopy (FESEM) were utilized to characterize the phase structure, thermal decomposition, and morphology of the products, respectively. Qualitative analyses indicate that the as-prepared products are fluorite-type structures. The lattice parameter and average crystallite size of the products are closely related to the ionic radii. The activation energy of crystal growth shows an increasing trend with the decrease in ionic radii. The sintering behavior of compacted body was also investigated, revealing that the sintering-resistance properties of Ln₂Ce₂O₇ are descending as the order of La₂Ce₂O₇, Nd₂Ce₂O₇, Sm₂Ce₂O₇, and Gd₂Ce₂O₇.